HomeMy WebLinkAboutAddendum 1 - RFP - 10181 Consulting Services - Water Treatment Facility Comprehensive PlanAddendum # 1
10181
ADDENDUM NO. 1
SPECIFICATIONS AND CONTRACT DOCUMENTS
Description of RFP 10181: Consulting Services - WTF Comprehensive Plan
OPENING DATE: 3:00 PM (Our Clock) July 23, 2025
To all prospective bidders under the specifications and contract documents described above, the
following changes/additions are hereby made and detailed in the following sections of this
addendum:
Exhibit 1 – Questions and Answers
Exhibit 2 – Preproposal Powerpoint Presentation .pdf
Please contact Jake Rector, Purchasing Manager, at (970) 221-6776 or jrector@fcgov.com with
any questions regarding this addendum.
RECEIPT OF THIS ADDENDUM MUST BE ACKNOWLEDGED BY A WRITTEN STATEMENT
ENCLOSED WITH THE PROPOSAL STATING THAT THIS ADDENDUM HAS BEEN
RECEIVED.
Financial Services
Purchasing Division
215 N. Mason St. 2nd Floor
PO Box 580
Fort Collins, CO 80522
970.221.6775
fcgov.com/purchasing
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EXHIBIT 1
Questions and Answers
1. Future Work Eligibility
Can the City please clarify whether the firm selected to develop the Comprehensive Plan will
be eligible to pursue — or be part of a team pursuing — future phases of work identified as
a result of this planning effort? Specifically, we would like to confirm that participation in this
contract does not preclude the selected firm from pursuing future related work, including
design and construction services.
A: Correct. An award for the Comprehensive Plan will not preclude the selected firm from
pursuing future related work.
2. Missing Exhibit
RFP page 15, Section D.9 references an attached “Preferred Qualifications & Experience”
exhibit that proposers are instructed to complete as part of the submittal. However, this
exhibit does not appear to be included in the RFP materials. Can the City please confirm
whether this exhibit is required and, if so, provide a copy?
A: The Preferred Qualifications and Experience template is no longer required.
3. Clarification on Preferred Qualifications
RFP page 15, Section D.8 asks proposers to provide project descriptions aligned with the
“Preferred Qualifications & Experience listed above and note which Qualification the
example/experience meets.” Can the City clarify whether there is a defined list of preferred
qualifications to reference, or if proposers are expected to interpret and format this content
based on their understanding of the RFP?
A: Preferred Qualifications and Experience template is no longer required. Please provide
any relevant experience in regards to long-range planning, CIP development, and other
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areas of the scope in the solicitation.
4. Reference Requirements
On page 15 of the RFP, Section D.4 and D.9 ask for three similar projects with references
and also to identify the team’s “top three references.” Can the City clarify whether these are
separate requirements, and if so, how they differ?
A: Please provide three references of similar projects that have been completed in the past
5 years.
5. Use of 11x17 Pages & Font Size in Graphics
The RFP states that 11x17 pages may be used for detailed pricing and will count as one
page. Would the City also permit the use of 11x17 pages for other content such as
schedules, organization charts, or infographics? Additionally, while the RFP specifies a
minimum font size of 10 pt, would it be acceptable for text within graphics or figures to be
slightly smaller, provided it remains legible?
A: Yes, the main point is to not submit an overly excessive proposal that doesn’t directly
meet the requirements of the RFP. Infographics must be limited to 2 pages.
6. Regarding Task 2 - Condition Assessment (pgs. 6-9)
1. Please provide additional information on the scope of work desired for the
condition assessment. Clarify if consultant should look at:
1. Poudre River Gateway Diversion, tunnel, and settling basin? A: Yes.
Particularly the structural integrity of these assets.
2. PVP settling basin? A: Structural analysis only.
3. RFP States (II. A. 5, page 5) “Raw water lines will be documented as best
as possible with limited access.” Please clarify if that includes physical
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assessment of all appurtenances/vaults along the raw water pipelines. Or
is the assessment expected to be a desktop assessment for the raw water
lines? A: The assessment will look at what areas of the pipe are easily
accessible, however that is a very small percentage of the entire pipeline.
The transmission lines are in need of repair and a detailed investigation of
their condition is not worth the effort in the eyes of the City. A desktop
exercise confirming to the best of our abilities where the pipe is and
opportunities for where to fix and/or move it are what is needed.
4. WTF in its entirety on site, including lab building? A: Yes to the process lab,
no to the Water Quality Lab.
5. Finished water storage tanks (exterior only?) A: Both interior and exterior
finished water storage tanks.
6. Yard piping at the WTF? A: Where possible, yes.
7. Regarding Task 3 – Long Range Planning, Subtask 3.2 Capacity and Quality Analysis (pg.
10)
a. Please confirm if a hydraulic model is being requested, and/or if hydraulic stress
testing of the facility is required for this effort. A:Please provide a hydrualic model.
b. Please confirm whether projecting changes in raw water quality conditions is
anticipated as part of the water quality analysis, or if analysis will be completed
based on current water quality. A: Analysis will be completed based on current
water quality with projections to the best of available based on any anticipated
changes in the 20-year horizon.
c. Please confirm that treated/finished water quality impacts related to high and low
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demands are limited to turbidity and TOC in the treated water, or if other
parameters are of interest such as iron and manganese are of interest. Are impacts
to coagulant and polymer dose, disinfection requirements and residuals handling
also to be considered? A: The main focus will be the filters, however, there is
interest in understanding the holistic water quality at low and high rates of
production.
8. Regarding Task 4 - Innovation and Partnership (pg.11)
a. RFP States (II. A. 7, page 5) “Evaluation potential partnership opportunities both
inside and outside the City of Fort Collins One Water Organization. This can
include, but is not limited to, other districts, other City departments, funding
opportunities, and overall watershed health.” During the pre-proposal meeting, City
staff stated desire is only for internal partnerships. Please clarify or confirm if
regional partnership opportunities with organizations outside the City are to be
included in this scope. If so, please provide additional level of effort desired:
number of workshops, meetings, etc. A: The intent is to create a list of potential
opportunities, but to not actually pursue them. Please do not plan to coordinate
any workshops or meetings with external entities. City staff will take on the efforts
as opportunities arise.
9. Clarification for Requirement Section D – Organization chart and Qualifications (pg. 15)
a. The RFP asks for an organizational chart (D.1. and D6.) and qualifications (D.3.
and D.7.-D.8.) twice. D.3. asks for “A list of qualifications for your firm and
qualifications and experience of the specific staff members (with professional
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licenses and certifications) proposed to perform the services described above” but
D.7. asks for “A list of qualifications for your firm and qualifications and experience,
including resumes, of the specific staff members proposed to perform the
consulting services described above” along with (D.8.) “project descriptions of work
performed and references for each of the Preferred Qualifications & Experience
listed above”. Is this intentional? Or should we include one set of requirements
over the other? A: Please include a list of key personnel with resumes that include
any relevant experience to this project for each person and past experience as a
team with references to contact.
b.Please clarify what consultants need to include in our project references. Do we
need to include all of the following: which qualification the example/experience
meets, owner’s name, title of project, beginning price, ending price, contact name,
email and phone number, staff proposed for these services, subconsultants on the
team and any change orders (as asked for in D.8.) A: Yes, please include all of the
items listed in this question.
10.Clarification for Requirement Section D.9. (pg. 15)
a.The RFP asks for consultants to complete an attached Preferred Qualifications &
Experience exhibit to identify our top three references but no exhibit is provided.
A: See answer to Question 2.
11.Clarification about Proposal Submittal (pg. 13)
a.Dividers and the Table of Contents are not included as part of the page count. Can
we use dividers as section-specific Table of Contents to list out the RFP
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requirements that will be covered in the following pages? Or will this count against
the page count requirements? A: Yes and it will not count against the page count.
b.Can we use an 11x17 sized page for items other than detailed pricing? (i.e., for the
schedule) A: Yes
12. Could you please share a copy of the Raw Water Line assessment that was
completed between summer 2018 and 2020?
A: See attached
June 24, 2025
10181 –Consulting Services –WTF Comprehensive Plan
Jake Rector & Kelly Wasserbach
EXHIBIT 2
10181 Consulting Services –WTF Comprehensive Plan
-Introductions
Jake Rector –Purchasing Manager
Kelly Wasserbach –Special Projects Manager
Gregg Stonecipher –Director, Plant Operations
Tyler Wells –Manager, Plant Operations
Scott Foreman –Sr. Supervisor Plant Maintenance
-Please enter Name, Company and Email in Chat Line
RFP Issued –June 16, 2025
Pre-Proposal Meeting –2:00PM MT June 24, 2025
Question Deadline –3:00PM MT July 9, 2025
Proposals Due –3:00PM MT July 23, 2025
Interviews –Week of August 11th
Award –September 2025
2
10181 Consulting Services – WTF Comprehensive Plan
3
Objective:
Planning services for the 20-year comprehensive plan for the
Water Treatment Facility including the treatment facility,
storage tanks, pump stations, and raw water infrastructure.
10181 Consulting Services – WTF Comprehensive Plan
Consultant Expectations, at a Minimum:
1.Workshops
2.Pageflips
3.Review of Existing Water Efficiency Plan, H2O Quality Report,
EMPs, Strategic Asset Management Plan and Previous H2O
Treatment Plans
4.High, Medium and Low Project Prioritization
5.Condition Assessment
6.Long Range Planning (20 Years)
7.Innovation and Regional Partnership Opportunities
8.Budgeting
4
10181 Consulting Services – WTF Comprehensive Plan
5
Tasks
Task 1 General Projects Management
Subtask 1.2 Project Controls and Reporting
Task 2 Condition Assessment
Subtask 2.1 Weighted Criterion
10181 Consulting Services – WTF Comprehensive Plan
Subtask 2.2: Condition Assessment
6
10181 Consulting Services – WTF Comprehensive Plan
Task 3 – Long Range Planning
Subtask 3.1 20 Year Demand Projections
Subtask 3.2 Capacity and Quality Analytics
Subtask 3.3 Changing Water Quality and Treatment Alternatives
7
10181 Consulting Services – WTF Comprehensive Plan
Task 4 – Innovation and Partnerships
Subtask 4.1 Levels of Service
Subtask 4.2 Innovation – Areas of potential improvement – Energy
efficiency, alternative energy sources, solids handling and
others
Subtask 4.3 One Water Partnerships – How can the Water Production
Program integrate with other sections of the One Water
Utility
8
10181 Consulting Services – WTF Comprehensive Plan
Task 5 – Project Prioritization and Budget
The project prioritization will assist the City with budgeting in the coming
years. The following must be included for each project listed:
9
10181 Consulting Services – WTF Comprehensive Plan
Task 6 – Comprehensive Plant Integration
Prepare a cohesive reading document containing pertinent information from
Tasks 2-5.
10
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Evaluation Criteria
10181 Consulting Services – WTF Comprehensive Plan
Colorado Open Records Act (CORA) C.R.S. §§24-72-200.1 et seq.
-Any proposals submitted hereunder are subject to public disclosure by
the City pursuant to CORA and City ordinances.
-Vendors may submit one (1) additional complete proposal clearly
marked “FOR PUBLIC VIEWING.”
-Such statement does not necessarily exempt such documentation
from public disclosure if awarded the project as all provisions of any
contract resulting from this request for proposal will be public
information.
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10181 Consulting Services – WTF Comprehensive Plan
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Questions?
Please send to Jake Rector at jrector@fcgov.com
RFP Issued – June 16, 2025
Pre-Proposal Meeting – 2:00PM MT June 24, 2025
Question Deadline – 3:00PM MT July 9, 2025
Proposals Due – 3:00PM MT July 23, 2025
Interviews – Week of August 11th
Award – September 2025
Poudre Pipeline Crossing Erosion
Study
This report presents an analysis of the risks
-inch steel and 24-
raw water supply pipelines cross
30, 2018
Sign-off Sheet
This document entitled Poudre Pipeline Crossing Erosion Study was prepared by Stantec Consulting Services Inc.
(“Stantec”) for the account of City of Fort Collins (the “Client”). Any reliance on this document by any third party is strictly
prohibited. The material in it reflects Stantec’s professional judgment in light of the scope, schedule and other limitations
stated in the document and in the contract between Stantec and the Client. The opinions in the document are based on
conditions and information existing at the time the document was published and do not take into account any subsequent
changes. In preparing the document, Stantec did not verify information supplied to it by others. Any use which a third party
makes of this document is the responsibility of such third party. Such third party agrees that Stantec shall not be
responsible for costs or damages of any kind, if any, suffered by it or any other third party as a result of decisions made or
actions taken based on this document.
Prepared by
(signature)
Randy Walsh
Reviewed and Approved by
(signature)
Cort Nickel, P.E.
POUDRE PIPELINE CROSSING EROSION STUDY
Table of Contents
EXECUTIVE SUMMARY ............................................................................................................ I
GLOSSARY ............................................................................................................................... V
1.0 PROJECT SCOPE AND GOALS ................................................................................. 1.1
1.1 PROJECT SCOPE ....................................................................................................... 1.1
1.2 PROJECT GOALS ....................................................................................................... 1.2
2.0 EVALUATION METHODOLOGIES .............................................................................. 2.1
2.1 COMPONENTS OF A GEOMORPHIC APPROACH TO RIVER ANALYSIS ................ 2.1
2.1.1 Stream and River Fundamentals ................................................................. 2.1
2.1.2 Bankfull Discharge ...................................................................................... 2.1
2.1.3 Channel Dimensions ................................................................................... 2.1
2.1.4 Channel Pattern .......................................................................................... 2.2
2.1.5 Channel Profile and Materials ..................................................................... 2.2
2.1.6 Vertical and Lateral Stability ........................................................................ 2.2
2.2 RESEARCH METHODS ............................................................................................... 2.3
2.2.1 Discharge Validation ................................................................................... 2.3
2.2.2 Longitudinal Profile ...................................................................................... 2.3
2.2.3 Cross Sections ............................................................................................ 2.3
2.2.4 Wolman Pebble Count ................................................................................ 2.4
2.3 MULTI-CRITERION DECISION ANALYSIS ................................................................. 2.4
3.0 ANALYSIS OF PIPELINE CROSSINGS ...................................................................... 3.1
3.1 CROSSING 1 ............................................................................................................... 3.1
3.1.1 Synopsis of Field Data ................................................................................ 3.1
3.1.2 Risk Analysis ............................................................................................... 3.7
3.2 CROSSING 2 ............................................................................................................... 3.8
3.2.1 Synopsis of Field Data ................................................................................ 3.8
3.2.2 Risk Analysis ............................................................................................. 3.14
3.3 CROSSING 3 ............................................................................................................. 3.15
3.3.1 Synopsis of Field Data .............................................................................. 3.15
3.3.2 Risk Analysis ............................................................................................. 3.21
3.4 CROSSING 4 ............................................................................................................. 3.22
3.4.1 Synopsis of Field Data .............................................................................. 3.22
3.4.2 Risk Analysis ............................................................................................. 3.25
3.5 CROSSING 5 ............................................................................................................. 3.26
3.5.1 Synopsis of Field Data .............................................................................. 3.26
3.5.2 Risk Analysis ............................................................................................. 3.31
3.6 CROSSING 6 ............................................................................................................. 3.32
3.6.1 Synopsis of Field Data .............................................................................. 3.32
3.6.2 Risk Analysis ............................................................................................. 3.38
3.7 CROSSING 7 ............................................................................................................. 3.39
3.7.1 Synopsis of Field Data .............................................................................. 3.39
3.7.2 Risk Analysis ............................................................................................. 3.44
POUDRE PIPELINE CROSSING EROSION STUDY
3.7.3 Evaluation of Alternatives .......................................................................... 3.44
3.8 CROSSING 8 ............................................................................................................. 3.48
3.8.1 Synopsis of Field Data .............................................................................. 3.48
3.8.2 Risk Analysis ............................................................................................. 3.53
3.9 CROSSING 9 ............................................................................................................. 3.54
3.9.1 Synopsis of Field Data .............................................................................. 3.54
3.9.2 Risk Analysis ............................................................................................. 3.64
3.9.3 Evaluation of Alternatives .......................................................................... 3.65
3.10 CROSSING 10 ........................................................................................................... 3.71
3.10.1 Synopsis of Field Data .............................................................................. 3.71
3.10.2 Risk Analysis ............................................................................................. 3.76
4.0 PLANNING LEVEL PROGRAM COSTS AND ENVIRONMENTAL PERMITTING ....... 4.1
4.1.1 Contractor’s Estimate of Construction Costs ............................................... 4.1
4.1.2 Engineer’s Opinion of Probable Project Costs ............................................. 4.2
4.1.3 Environmental Permitting ............................................................................ 4.3
5.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................ 5.5
5.1 CROSSING 2 RECOMMENDATIONS.......................................................................... 5.5
5.2 CROSSING 7 RECOMMENDATIONS.......................................................................... 5.6
5.3 CROSSING 9 RECOMMENDATIONS.......................................................................... 5.6
6.0 REFERENCES ............................................................................................................. 6.1
LIST OF TABLES
Table 1 - Typical Crossing Alternatives Decision Matrix ........................................................... 2.5
Table 2 - Crossing 7 Alternatives Decision Matrix .................................................................. 3.47
Table 3 - Estimated Riprap Sizing Requirements ................................................................... 3.65
Table 4 - Crossing 9 Alternatives Decision Matrix .................................................................. 3.70
Table 5 – Construction Cost Estimates for Crossing 7 Alternatives .......................................... 4.1
Table 6 – Construction Cost Estimates for Crossing 9 Alternatives .......................................... 4.2
Table 7 - EEOPPC for Crossing 7, Alternative 4 “Waterline Lowering” ..................................... 4.3
Table 8 - EEOPPC for Crossing 9, Alternative 4 & 5 “Channel Habitat Improvements and
Waterline Lowering” ................................................................................................... 4.3
Table 9 - Summary of Geomorphic Risk by Crossing Location ................................................. 5.5
LIST OF FIGURES
Figure 1 Pipeline Crossing Locations – Key Map (Drawing No. C-00.0) ................................... 1.3
Figure 2 Crossing Location #1, 24" RCP & 27" STL Pipelines (Drawing No. C-01.0) ............... 3.2
Figure 3 Crossing Location #1, 24" RCP & 27" STL Profiles (Drawing No. C-01.1) .................. 3.3
Figure 4 Crossing Location #1, Geomorphic Cross Sections (Drawing No. C-01.2) ................. 3.4
Figure 5 Crossing Location #1, Geomorphic Cross Sections (Drawing No. C-01.3) ................. 3.5
Figure 6 Crossing Location #1, Geomorphic Longitudinal Profiles (Drawing No. C-01.4) ......... 3.6
Figure 7 Left Bank at Crossing 1 .............................................................................................. 3.7
Figure 8 Crossing Location #2, 27" STL Pipeline (Drawing No. C-02.0) ................................... 3.9
Figure 9 Crossing Location #2, 27" STL Profile (Drawing No. C-02.1) .................................... 3.10
Figure 10 Crossing Location #2, Geomorphic Cross Sections (Drawing No. C-02.2) ............. 3.11
POUDRE PIPELINE CROSSING EROSION STUDY
Figure 11 Crossing Location #2, Geomorphic Cross Sections (Drawing No. C-02.3) ............. 3.12
Figure 12 Crossing Location #2, Geomorphic Longitudinal Profiles (Drawing No. C-02.4) ..... 3.13
Figure 13 Crossing 2 Left Bank Erosion (A) and (B) ............................................................... 3.14
Figure 14 Crossing Location #3, 27" STL Pipeline (Drawing No. C-03.0) ............................... 3.16
Figure 15 Crossing Location #3, 27" STL Pipeline Profile (Drawing No. C-03.1) .................... 3.17
Figure 16 Crossing Location #3, Geomorphic Cross Sections (Drawing No. C-03.2) ............. 3.18
Figure 17 Crossing Location #3, Geomorphic Cross Sections (Drawing No. C-03.3) ............. 3.19
Figure 18 Crossing Location #3, Geomorphic Longitudinal Profiles (Drawing No. C-03.4) ..... 3.20
Figure 19 Crossing 3 Right Bank Erosion ............................................................................... 3.21
Figure 20 Crossing Location #4, 24" RCP & 27" STL Pipelines (Drawing No. C-04.0) ........... 3.23
Figure 21 Crossing Location #4, 24" RCP & 27" STL Profiles (Drawing No. C-04.1) .............. 3.24
Figure 22 Crossing 4 Left Bank Erosion (A) and (B) ............................................................... 3.25
Figure 23 Crossing Location #5, 24" RCP & 27" STL Pipelines (Drawing No. C-05.0) ........... 3.27
Figure 24 Crossing Location #5, 24" RCP & 27" STL Profiles (Drawing No. C-05.1) .............. 3.28
Figure 25 Crossing Location #5, Geomorphic Cross Sections (Drawing No. C-05.2) ............. 3.29
Figure 26 Crossing Location #5, Geomorphic Longitudinal Profile (Drawing No. C-05.3) ....... 3.30
Figure 27 Crossing Location #6, 24" RCP & 27" STL Pipelines (Drawing No. C-06.0) ........... 3.33
Figure 28 Crossing Location #6, 24" RCP & 27" STL Profiles (Drawing No. C-06.1) .............. 3.34
Figure 29 Crossing Location #6, Geomorphic Cross Sections (Drawing No. C-06.2) ............. 3.35
Figure 30 Crossing Location #6, Geomorphic Cross Sections (Drawing No. C-06.3) ............. 3.36
Figure 31 Crossing Location #6, Geomorphic Longitudinal Profiles (Drawing No. C-06.4) ..... 3.37
Figure 32 Crossing Location #7, 24" RCP & 27" STL Pipelines (Drawing No. C-07.0) ........... 3.40
Figure 33 Crossing Location #7, 24" RCP & 27" STL Profiles (Drawing No. C-07.1) .............. 3.41
Figure 34 Crossing Location #7, Geomorphic Cross Sections (Drawing No. C-07.2) ............. 3.42
Figure 35 Crossing Location #7, Geomorphic Longitudinal Profile (Drawing No. C-07.3) ....... 3.43
Figure 36 Crossing Location #7, Alternative 2 (Drawing No. C-07.4) ...................................... 3.45
Figure 37 Crossing Location #7, Alternative 3 (Drawing No. C-07.5) ...................................... 3.46
Figure 38 Crossing Location #8, 27" STL Pipelines (Drawing No. C-08.0) ............................. 3.49
Figure 39 Crossing Location #8, 27" STL Profiles (Drawing No. C-08.1) ................................ 3.50
Figure 40 Crossing Location #8, Geomorphic Cross Sections (Drawing No. C-08.2) ............. 3.51
Figure 41 Crossing Location #8, Geomorphic Longitudinal Profile (Drawing No. C-08.3) ....... 3.52
Figure 42 Discharge vs Shear Stress ..................................................................................... 3.55
Figure 43 Discharge vs Unit Stream Power ............................................................................ 3.55
Figure 44 Discharge vs. Width ............................................................................................... 3.56
Figure 45 Hydraulic Condition Comparison ............................................................................ 3.56
Figure 46 Crossing Location #9, 27" STL Pipeline (Drawing No. C-09.0) ............................... 3.58
Figure 47 Crossing Location #9, 27" STL Profile (Drawing No. C-09.1) .................................. 3.59
Figure 48 Crossing Location #9, Geomorphic Cross Sections (Drawing No. C-09.2) ............. 3.60
Figure 49 Crossing Location #9, Geomorphic Cross Sections (Drawing No. C-09.3) ............. 3.61
Figure 50 Crossing Location #9, Geomorphic Cross Sections (Drawing No. C-09.4) ............. 3.62
Figure 51 Crossing Location #9, Geomorphic Longitudinal Profiles (Drawing No. C-09.5) ..... 3.63
Figure 52 Crossing 9 Flow Convergence Example ................................................................. 3.64
Figure 53 Crossing Location #9, Alternative 2 (Drawing No. C-09.6) ...................................... 3.67
Figure 54 Crossing Location #9, Alternative 3 (Drawing No. C-09.7) ...................................... 3.68
Figure 55 Crossing Location #9, Alternative 4 (Drawing No. C-09.8) ...................................... 3.69
Figure 56 Crossing Location #10, 24” RCP & 27" STL Pipeline (Drawing No. C-10.0) ........... 3.72
Figure 57 Crossing Location #10, 24” RCP & 27" STL Profile (Drawing No. C-10.1) .............. 3.73
Figure 58 Crossing Location #10, Geomorphic Cross Sections (Drawing No. C-10.2) ........... 3.74
POUDRE PIPELINE CROSSING EROSION STUDY
Figure 59 Crossing Location #10, Geomorphic Longitudinal Profiles (Drawing No. C-
10.3) ........................................................................................................................ 3.75
POUDRE PIPELINE CROSSING EROSION STUDY
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Executive Summary
Since the early days of the City of Fort Collins (City), planners have focused on providing redundant water supplies.
As part of that redundancy, the City owns and operates two pipelines in the Cache La Poudre (Poudre) River Canyon
- between Gateway Park and the mouth of the Poudre Canyon.
Between 1924 and 1926, the City constructed a 24” diameter Reinforced Concrete Pipe (RCP) between the Pre-
Sedimentation Basin (a.k.a. “Pre-Sed Basin”) at Gateway Park and the community of Bellvue. Later, in the mid-
1950’s, the City constructed a 27” diameter steel (STL) pipeline in the same corridor to increase the quantity and
reliability of their raw water conveyance. These pipelines are critical to the conveyance of raw water to the City’s
water treatment plant. Damage to either of these pipelines would impact operation of the water utility. Thus,
protection of these assets is a high priority for the City.
During the semi-annual inspection of the pipelines in the Fall of 2017, the City noticed that a section of the 27” steel
pipe near Gateway Park had been exposed; becoming the primary driver in the Spring/Summer of 2018 for the City to
commission an analysis of how best to protect this section of pipe concurrently with evaluating all river crossings for
both the 24” RCP and 27” steel pipelines.
Figure ES-1 shows the overall location of the ten 27” steel pipeline crossings and the six 24” RCP pipeline crossings
of the Poudre. Stantec’s Stream Restoration Group conducted a geomorphic assessment at these crossing locations
on April 11-12, 2018. As a result of the survey and subsequent data processing, the team identified three crossings
with potential risks to the waterlines at crossings 2, 7, and 9, as indicated in Table ES-1.
Table ES-1 - Summary of Geomorphic Risk by Crossing Location
Crossing # Low Risk Medium Risk High Risk
1
2
3
4
5
6
7
8
9
10
Crossing locations 2, 7, and 9 have some degree of exposure risk based on existing geomorphic conditions. Crossing
2 is located south of State Highway 14 and just downstream of the Canyon mouth. Currently, local erosion in this
reach does not pose an immediate threat to either the 24” RCP or 27” STL. As such, we recommend the City
POUDRE PIPELINE CROSSING EROSION STUDY
ii
conduct annual post-runoff monitoring to further evaluate the instabilities in this reach. Should erosion continue, or a
chute cutoff begin to develop, further actions may be warranted.
Crossing 7 includes both 24” RCP and 27” STL pipe crossings. The 24” RCP is considered a moderate risk crossing
because of the uncertainty associated with the extent of potential pipe exposure and because the pipe crosses the
river through a pool section – placing the pipeline at greater risk of vertical degradation especially at high flow events.
As such, we recommend the City plan to lower the 24” RCP through this section and that the City budget $475,000
for Work associated with this crossing. We also recommend this project be completed concurrently with the Work
associated with Crossing 9. Due to the need to budget, design and obtain permits, the earliest this Work could be
completed would be Fall 2019. The 27” STL pipe is considered a low risk crossing because it crosses the river in a
glide section - the least hazardous location for a pipe crossing as glide sections are more prone to aggradation rather
than degradation. As part of the City’s planning efforts, these crossings should be re-surveyed in the Fall of 2018 to
confirm potential geomorphic changes.
Crossing 9 is located just downstream of the entrance to Gateway Park. Crossing 9 represents the reach with the
highest risk associated with channel/bed degradation in relation to the 27” STL waterline crossing. Anthropogenic
alterations of the channel banks and floodplains have created an area of rapid constriction and increased
confinement, which have resulted in exposure of approximately 75’ of waterline along the left bank. Due to the extent
of the exposure, we recommend corrective action by implementing Design Alternative 4 - “Holistic Geomorphic
Approach with Waterline Lowering” (as shown in Figure ES-2) in conjunction with lowering the waterline through this
reach.
Alternative 4 focuses on adjustment of the channel and floodplain geometry to eliminate bank erosion at higher flow
events, paired with the riprap protection described in Alternative 5. Primarily, the channel and floodplain
improvements would occur in the “Upstream Reach” of the crossing and consist of implementing a bankfull bench
with wood toe and soil lifts. Wood is the preferred material for bank reconstruction in this area due to the stability a
bioengineered structure provides combined with the physical and biological uplift it creates through time (e.g.,
bedform complexity, allochthonous input). This modification of the overwide “Upstream Reach” will reduce the rapid
constriction at the waterline crossing and improve flow resistance and energy dissipation along the Woody Toe. This
solution addresses the cause of the bank erosion, instead of patching the symptoms. Improving the geometry of the
channel and associated floodplain at the 27” STL crossing offers a sustainable long-term alternative to the
reoccurring pipe exposure issue. We recommend the City budget $950,000 for Work associated with this crossing
and that this Work be completed as-soon-as-practical.
Prior to implementation of any improvements, the City will need to budget, design, and obtain permits for the
improvements. From a scheduling perspective, the earliest this Work could be completed would be in the Fall of
2019.
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-00.0
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PIPELINE CROSSING LOCATIONS
KEY MAP
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MAC MAC CDN
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PIPELINE CROSSING LOCATIONS KEY MAP
1" = 1500'
PICNIC
ROCK
VISITOR'S
CENTER
MUNROE DIVERSION
SIPHON
PRE-SED
BASIN
GATEWAY PARK &
NATURAL AREA
SEAMAN
RESERVOIR
STATE HWY 14
CROSSING
LOCATION #1
CROSSING
LOCATION #2
(MEDIUM RISK)
CROSSING
LOCATION #3
CROSSING
LOCATION #4
CROSSING
LOCATION #5
CROSSING
LOCATION #6
CROSSING
LOCATION #7
(MEDIUM RISK)
CROSSING
LOCATION #8
CROSSING
LOCATION #9
(HIGH RISK)
CROSSING
LOCATION #10
DIVERSION
STRUCTURE
24" RCP
LINE
27" STL
LINE
67" PVP
PIPELINE
FI
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MUNROE CANAL
POUDRE VALLEY CANAL
MUNROE DIVERSION
CHARLES HANSEN
FEEDER CANAL
POUDRE PIPELINE CROSSING EROSION STUDY
iv
Figure ES-2 Wood-Toe and Soil Lifts Detail
POUDRE PIPELINE CROSSING EROSION STUDY
v
Glossary
Active Bed Riffle Pebble Count – A systematic sample method to characterize the bed material
only at the surveyed riffle cross-section where one hundred particles are measured at
evenly spaced intervals across the active bed.
Aggradation – a raising of local base level due to sediment depositional processes.
Allochthonous - material imported into an ecosystem from outside of it. In stream and river
systems, the term usually refers to wood or leaves which serve as a food source for benthic
macroinvertebrates. Such materials provide the basis for nutrient cycling and food web
dynamics in many fluvial systems.
Bank-Height Ratio (BHR) – a quantitative measure of the degree of vertical containment or
degree of channel incision as determined by the ratio of the lowest bank height divided
by the maximum bankfull depth.
Bankfull Depth – See Mean Bankfull Depth (dbkf)
Bankfull Discharge – a frequently occurring peak flow whose stage represents the incipient point
of flooding. It is often associated with a return period of 1-2 years, with an average of 1.5
years. It is expressed as the momentary maximum of instantaneous peak flows rather than
the mean daily discharge.
Bankfull Stage – The elevation of the water surface associated with the bankfull discharge.
Bankfull Width (Wbkf) – The surface width of the river measured at the bankfull stage.
Belt Width – The width of the full lateral extent of the bankfull channel measured perpendicular
to the Fall line of the valley.
CFS – Cubic Feet per Second
Channel Confinement – A measure of the lateral containment of a river channel as measured by
Meander Width Ratio (the ratio of belt width to bankfull width). The lower the
dimensionless value of MWR, the more confined the river channel.
Channel Incision – The process of lowering of the local base level. The degree of incision is
measured by Bank-Height Ratio (BHR): ratio of lowest bank height to maximum bankfull
depth.
Competence – The ability of the river to move the largest particle made available from the
immediate upstream supply.
Cross-Sectional Area (Abkf) – The sum of the products of unit width and depth at the bankfull
stage elevation in a riffle section.
D values (e.g., D50, D85) - The most commonly used metrics when describing particle
size distributions. The D50 is the diameter of the particle that 50% of a sample's mass is
smaller than and 50% of a sample's mass is larger than.
Degradation – A lowering of local base level due to channel incision processes.
POUDRE PIPELINE CROSSING EROSION STUDY
vi
Entrenchment – The vertical containment of a river that is quantitatively defines as the width of
the flood-prone area divided by the bankfull width. (The flood-prone area is the width of
the channel at an elevation that is twice the maximum bankfull riffle depth).
Floodplain – The floodplain is the relatively flat area adjacent to the bankfull channel. It is
available to the river to accommodate flows greater than the bankfull discharge. There is
not a constant frequency of occurrence of flood discharge associated with the
floodplain as the depth of flow over the floodplain is a function of the width and the
roughness of the floodplain and the magnitude of the flood peak.
Flood-Prone Area Width – The width of the channel associated with the elevation that is twice
the maximum bankfull depth. It is the area including the floodplain of the river and often
the low terrace of alluvial rivers. This value, when divided by the bankfull width, is used to
determine entrenchment ratio.
Incision – A process relating to abandonment of an active floodplain and a lowering of the
local base level.
Left Bank – The left bank of the river when viewed in the downstream direction.
Maximum Bankfull Depth (dmbkf) – Maximum depth of the bankfull channel cross-section or the
distance between the thalweg and bankfull stage.
Mean Bankfull Depth (dbkf) – The mean depth of flow at the bankfull stage, determined as the
cross-sectional area (sum of the products of unit width and depth) divided by the surface
bankfull width.
Meander Width Ratio (MWR) – The quantitative, morphological measure of confinement that is
determined by the ratio of belt width to bankfull width.
Pebble Count – See Active Bed Riffle Pebble Count
Riffle/Pool Channel – Channels where pools (deep and flat slope facets) and riffles (shallow and
steep slope facets) occur.
Right Bank – The right bank of the river when viewed in the downstream direction.
River Stability – A river’s ability in the present climate to transport streamflows and sediments of its
watershed, over time, in such a manner that the channel maintains its dimension, pattern,
and profile without either aggrading nor degrading.
Shear Stress (τ) – The frictional force per unit area causing flow resistance along the channel
boundary.
Thalweg – the “line” connecting the lowest or deepest points along a river bed, valley, or
reservoir, whether under water or not.
USACE – United States Army Corps of Engineers
Width/Depth Ratio – The ratio of bankfull surface width (Wbkf) to mean bankfull depth (dbkf). The
width/depth ratio is a dimensionless value that describes the channel shape (large
number = wide & shallow; small number = narrow & deep) and is used as delineative
criteria for stream classification and in departure analyses for channel stability.
Wolman Pebble Count – See Active Bed Riffle Pebble Count
POUDRE PIPELINE CROSSING EROSION STUDY
Project Scope and Goals
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1.0 PROJECT SCOPE AND GOALS
1.1 PROJECT SCOPE
As shown on Figure 1, the 27-inch steel pipe crosses the Cache La Poudre (“Poudre”) River a total of ten (10) times
at locations from the Pre-Sedimentation Basin (Pre-Sed Basin) to just downstream of the mouth of the Canyon. In
addition, the 24-inch RCP crosses the River a total of six (6) times in this same corridor. At several locations, the
pipelines cross in the same general location – resulting in ten (10) discrete crossing locations.
Per the March 5, 2018 Work Order (P.O. # 9181655) between Stantec and the City, Stantec’s Scope of Services
focused on analysis of these crossings and on providing the City an understanding of the pipelines geomorphological
risk mechanisms, overall risks of pipeline exposure, and accompanying approaches to mitigate these risks.
Stantec’s Work began with acquisition of data to define the horizontal and vertical location of the pipelines within the
river bed and banks. Working with City locate crews and Coffey Engineering (project survey subconsultant), Stantec
first established the horizontal and vertical control at the ten crossings on the same database as that used on
previous pipeline work in the Canyon. Following establishing project survey control, the project team located the
pipeline at all crossing locations by tracing the pipe, horizontally and vertically, as located by City locate crews. The
survey team also took spot elevations and recorded top of pipe depth elevations at each of the marked locations
provided by locators. Top of pipe depths for the 24” RCP could not always be gathered from the utility locator device
due to pipe material. However, the top of surface elevation shots along this alignment were verified after integrating
the survey with a 3-D model of the pipeline alignment provided by Pure Technologies, following a previous inspection
of the 24” RCP pipeline in September of 2017.
Following locating the pipelines, Stantec’s Stream Restoration Group conducted a geomorphic field survey and
collected data to quantify and assess vertical and lateral stream migration potential. Geospatial data capture of
specific sections and river thalweg profiles were also completed at key locations within each of the ten (10) crossings,
as well as above and below pipe crossing locations.
In general, these GPS surveyed cross-sections were completed at approximately one-hundred feet (100’) intervals
upstream and downstream of each crossing –as based on the configuration of the river. A Wolman Pebble Count
was conducted within the project reaches to determine the D50 and D85 of the bed and bank material. This information
was utilized in combination with available hydrology and hydraulics data to estimate sediment transport competence
and capacity through the existing reach. In addition to these surveys, photographs were taken of the Poudre River
along the pipeline alignment. The Analysis of Pipeline Crossings Sections of this report includes Plan and Profiles,
longitudinal profiles, cross-sections, Wolman Pebble Counts and photographs for each of the ten (10) discrete
crossing locations.
Once this data was acquired, Stantec assessed the stability of the river bed and banks, estimated the stability of the
river bed material, and evaluated scour potential and lateral forces that could be encountered during a range of
discharges, including the estimated100-year flood event. Data processing and modeling associated with scour
analysis include CAD, GIS, and RiverMorph software. Discharge Values and corresponding return intervals were
determined by analyzing the Colorado Department of Water Resource stream gage at the Canyon mouth.
POUDRE PIPELINE CROSSING EROSION STUDY
Project Scope and Goals
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Various alternatives were considered to protect the pipeline crossings at risk – three of the more common practices
including encasing the pipe, improving channel geometry, and armoring the river banks. As appropriate, we also
considered various combinations thereof.
While these approaches protect the pipe from impacts, they may not completely mitigate undercutting or exposure of
the pipe and encasement. As such, we also investigated alternative solutions including:
• Lowering the pipe along its profile and encasing the pipe in concrete that is, in turn, attached to the bedrock,
• Armoring the upstream and downstream sides of the pipe to a depth greater than anticipated bed migration,
• Placing the pipe on piers anchored to bedrock.
1.2 PROJECT GOALS
Given the above, the City commissioned this study to address the following goals:
• Goal #1, Pipeline Location – continue to advance the knowledge of and document the horizontal and
vertical location of the pipelines between the mouth of the Canyon to Gateway Park.
• Goal #2, Stream Stability Analysis – complete a stream stability analysis of the existing pipelines from the
mouth of the Canyon to Gateway Park.
• Goal #3, Analysis of Alternatives – complete an analysis of viable options to mitigate any at risk crossings,
including the existing section of exposed 27-inch steel pipeline.
• Goal #4, Mitigation Planning – provide programming level Work element plans, budgets, and schedules for
any medium to high risk pipeline crossings.
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-00.0
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PIPELINE CROSSING LOCATIONS
KEY MAP
0
As Indicated
MAC MAC CDN
N
PIPELINE CROSSING LOCATIONS KEY MAP
1" = 1500'
PICNIC
ROCK
VISITOR'S
CENTER
MUNROE DIVERSION
SIPHON
PRE-SED
BASIN
GATEWAY PARK &
NATURAL AREA
SEAMAN
RESERVOIR
STATE HWY 14
CROSSING
LOCATION #1
CROSSING
LOCATION #2
(MEDIUM RISK)
CROSSING
LOCATION #3
CROSSING
LOCATION #4
CROSSING
LOCATION #5
CROSSING
LOCATION #6
CROSSING
LOCATION #7
(MEDIUM RISK)
CROSSING
LOCATION #8
CROSSING
LOCATION #9
(HIGH RISK)
CROSSING
LOCATION #10
DIVERSION
STRUCTURE
24" RCP
LINE
27" STL
LINE
67" PVP
PIPELINE
FI
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R
E
1
MUNROE CANAL
POUDRE VALLEY CANAL
MUNROE DIVERSION
CHARLES HANSEN
FEEDER CANAL
POUDRE PIPELINE CROSSING EROSION STUDY
Evaluation Methodologies
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2.0 EVALUATION METHODOLOGIES
2.1 COMPONENTS OF A GEOMORPHIC APPROACH TO RIVER
ANALYSIS
2.1.1 Stream and River Fundamentals
A stream and its floodplain comprise a dynamic environment where the floodplain, channel, and stream bed evolve
through natural processes. Weather and hydraulic processes erode, transport, sort, and deposit alluvial materials
throughout the riparian system. The size and flow of a stream are directly related to its watershed area. Other factors
that affect channel size and stream flow are vegetation, geology, land use, soil types, topography, and climate.
Channel morphology reflects all these factors. The result is a dynamic equilibrium wherein the stream maintains its
dimension, pattern, and profile over time, and neither degrades nor aggrades (Rosgen 1996). Land use changes in
the watershed, including increases in imperviousness, channelization resulting in a lower groundwater elevation, and
removal of riparian vegetation, can upset this balance. A new equilibrium may eventually result, but not before large
adjustments in channel form can occur, such as extreme bank erosion or incision (Lane 1955; Schumm 1977).
2.1.2 Bankfull Discharge
By convention, the “left bank” and “right bank” nomenclature adopted when discussing river systems are defined as
one would look down river. Bankfull discharge, also referred to as the channel-forming discharge, effective discharge,
or dominant discharge, creates a natural and predictable channel size and shape. This discharge is the flow which
moves the most sediment over time, thus having the greatest impact on sediment distribution and channel geometry.
Proper determination of bankfull stage in the field is vital to stream assessment.
The bankfull stage is the depth of bankfull discharge in a channel and represents the break point between the
channel and the floodplain. This point may or may not be the top of the stream bank. For example, if the stream has
incised (cut down) the bankfull stage may be indicated by a stain on the stream bank. If the stream has widened the
bankfull stage may be a small depositional bench on the stream bank. On average, bankfull discharge occurs every
1.5 years (Leopold 1994).
2.1.3 Channel Dimensions
The width, depth, and cross-sectional area values of a stream or river channel cross section are the channel’s
“dimensions.” Channel dimensions are expressed relative to bankfull stage. Width is related to flow frequency and
amount and the size and type of channel materials and transported sediment. Depth varies greatly even in stream
reaches experiencing the same flow, due to riffle and pool stream bed features. Riffles are shallow areas with fast
moving flow; pools are deep areas with slower moving water. Bankfull cross-sectional area is an expression of
channel size related to the amount of streamflow and watershed size. Changes in channel dimension correspond to
changes in the amount and/or frequency of bankfull discharge and can result from land development, reservoir
management, flow diversion, grazing management, vegetation management, and other watershed practices (Rosgen
1996).
POUDRE PIPELINE CROSSING EROSION STUDY
Evaluation Methodologies
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2.1.4 Channel Pattern
The plan view features of streams and rivers are the stream channel pattern and include straight, sinuous, or braided
forms. Stream pattern can be quantitatively expressed with the geometric parameters of radius of curvature, meander
wavelength, amplitude, and belt width. Meander geometry is most often expressed as a function of bankfull width at a
riffle. For example, the location and spacing of riffles and pools correspond to the straight segments and curved
sections of the stream and the linear distance between pools is commonly noted to be 5-7 times bankfull width as the
result of empirical studies (Leopold et al. 1964). Changes in the amount and frequency of bankfull discharge can
change stream patterns because the patterns of rivers develop to provide energy dissipation of the moving water and
sediment. Correspondingly, altering river pattern, such as by straightening, ultimately leads to instability.
2.1.5 Channel Profile and Materials
The slope of the flowing, bankfull discharge water surface and the stream bed relief as the water flows along the
deepest part of the cross section (thalweg), down into pools and up and over riffles, constitute the stream channel
profile. Stream slope generally decreases in the downstream direction as streamflow increases, but there are many
variations in channel slope, bed features, and channel materials that are independent of streamflow and watershed
location due to local topography and geology.
The profile of a stream bed and the composition of stream bed materials are largely dependent on valley slope and
geology. In simple terms, steep, straight streams are found in steep, colluvial valleys, while flat, meandering streams
are found in flat, alluvial valleys. A colluvial valley forms through hillslope processes. Sediment supply in colluvial
valleys is controlled by hillslope erosion and mass wasting (i.e., the sediments in the stream bed originate from the
hillslopes). Sediments reaching the channel in a colluvial valley are typically poorly-sorted mixtures of fine and
coarse-grained materials, ranging in size from sand to boulders. In contrast, an alluvial valley forms through stream
and floodplain processes. Sediments in alluvial valleys include some coarse gravel and cobble, transported from
steeper upland areas, but consist predominantly of fine grained particles such as gravel and sand. Grain size
generally decreases with decreasing valley slope and increasing drainage area (Lane 1955).
Meandering streams in alluvial valleys have sequences of riffles and pools that maintain channel slope and bed
stability. The riffle is a bed feature composed of gravel or larger-sized particles. The water depth at a riffle is relatively
shallow, and the slope is steeper than the average slope of the channel. Riffles control the stream bed elevation and
are usually found in straight channel segments, or the cross-overs between curved segments (meander bends). The
inside of the meander bend is a depositional feature called a point bar; pools are typically located on the outside
bends of meanders, between riffles. Pools have a flat slope and are much deeper than the average depth of the
channel.
2.1.6 Vertical and Lateral Stability
A naturally stable stream must be able to transport the sediment load supplied by its watershed while maintaining
dimension, pattern, and profile over time so that it does not degrade or aggrade (Rosgen, 1994). Stable streams
migrate within landscapes slowly, over long periods of time, while maintaining their form and function.
Instability of the streambed occurs when scouring causes the channel to incise (degrade), or excessive deposition
causes the channel bed to rise (aggrade). Instability of the stream banks can result from a variety of processes both
POUDRE PIPELINE CROSSING EROSION STUDY
Evaluation Methodologies
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interconnected and independent of those related to streambed instability, including surface erosion, mass wasting,
and ice scour. The ability of streambanks to resist erosion is primarily determined by the ratio of stream bank height
to bankfull stage, various stream bank and riparian area vegetation characteristics (such as rooting density/depth and
surface density), stream bank angle, and various stream bank material characteristics (such as stream bank material
composition and stratigraphy).
Bank erosion is a natural and normal fluvial process, provided the rates are not excessive or occurring where it is not
expected. Bank erosion is common along the outside of bends where hydraulic forces are locally intensified by bend
geometry (Knighton 1998). In quasi-equilibrium systems, the rate of erosion on one bank is equal to the rate of
sediment deposition on the opposite bank. In such systems, the rate of erosion along bends is not excessive,
meaning that vegetation growth is typically able to keep up with bank retreat. Higher rates of bank erosion, several
inches or more per year, or bank erosion that is occurring along straight sections of channel, is often an indication of
a problem.
2.2 RESEARCH METHODS
2.2.1 Discharge Validation
The identification of bankfull is one of the single most important features to determine geomorphic parameters, such
as stream type, bank height ratios, width to depth ratios, and entrenchment ratios. The methods used to determine
bankfull stage and corresponding discharge include:
• Prior to the initial field work a gage analysis of annual peak flow data was conducted. A Log-Pearson Type
III Distribution was used to estimate the discharge that occurs approximately every 1.25-1.5 years, which is
typical of a bankfull discharge in the Mountain West.
• At each crossing location, we identified the most consistent bankfull indicators that were obviously formed by
river processes, such as point bars, lateral bars, or similar depositional bank features. These features were
surveyed in both the longitudinal profile and cross sections. In many cases, a survey shot was taken at both
the upper and lower extent of these depositional features to provide a bracket in the limits for analysis.
• The survey data was then post-processed, considering the overall bankfull slope, active riffle bed
distribution, and cross-sectional area, to calculate estimated discharges within the upper and lower bankfull
indicators.
• The calculated discharges were then compared to the gage analysis discharges for overall agreement.
2.2.2 Longitudinal Profile
A longitudinal profile is created by measuring and plotting elevations of the deepest point in the channel bed, water
surface, bankfull, and low bank height. Profile points are surveyed at prescribed intervals and at significant breaks in
slope, such as head of riffle and deepest point of a pool. This profile can be used to determine average bankfull water
surface slope. Facet (e.g., riffle, run, pool) slopes of each individual stream bed feature (measured along the water
surface) are also important for stability assessment.
2.2.3 Cross Sections
A cross section is created by measuring and plotting elevations along a line crossing the stream channel at a right
angle. The width of the flood-prone area of the channel is also included. Flood-prone area width is associated with a
POUDRE PIPELINE CROSSING EROSION STUDY
Evaluation Methodologies
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flood stage equal to twice the bankfull depth. Measurements are taken at bankfull, the top of bank, the water surface,
and at break-in-slope points.
2.2.4 Wolman Pebble Count
The pebble count procedure (Wolman 1954) characterizes the channel and bed material present through a given
study reach. A representative pebble count is used to classify the stream type, whereas an active bed riffle pebble
count is used for hydraulic calculations and to calculate sediment competence. Active bed pebble counts characterize
the channel substrate only at the surveyed riffle cross section – these were collected for select Poudre River crossing
locations. To complete the survey, one hundred particles are measured at evenly-spaced intervals across the active
bed of the surveyed riffle cross-section. The active bed riffle count data are used for hydraulic calculations (R/D84)
and for sediment competence calculations.
2.3 MULTI-CRITERION DECISION ANALYSIS
Each capital improvement project has its unique combination of monetary and non-monetary elements. For example,
although a project may have significant capital costs, its overall benefits make the project viable or necessary, despite
the costs. To help understand how to value these elements against each other, decision makers often rely on a
Multi-Criterion Decision Analysis, or MCDA matrix. A typical MCDA includes three key elements 1) the criteria that
are important to the selection (i.e. permitting, capital cost, etc.) 2) each criteria’s’ importance factor when considered
against other criteria (for example the environmental impacts of a project may be twice as important as the projects
capital costs) and, 3) the alternatives being considered.
The comparison criteria considered in this study are included below along with a synopsis of what issues the
comparison criteria address are:
Permitting – Addresses the scheduling and difficulties associated with obtaining a permit from the USACE
Temporary Recreation Impacts – Addresses the impacts of the project on recreational uses in the project reach
Changes to River Environment – Addresses long-term structural changes to the river form associated with project
Capital Cost – Addresses estimated Capital cost (including design, permitting and construction)
Long-Term Pipeline Stability – Addresses whether option is either a short-term or long-term solution
Habitat Improvements – Addresses whether option improves habitat of river reach
To obtain a weighted total, each comparison criteria is then evaluated on a scale from 1 to 5 based on the options
unique characteristics with 1 being the least desirable characteristic and 5 being the most desirable characteristic.
These values are then multiplied by the importance factor to get the sub-total weight for each comparison criteria.
When all the sub-total weights are added for each alternative, a weighted total is obtained for that alternative and, the
alternative with the highest weighted total being the most preferred.
The weighted totals are also graphically highlighted with green being the most desirable alternative and red being the
least desirable alternative. In addition, each alternative has also been highlighted using the same green/red displays.
POUDRE PIPELINE CROSSING EROSION STUDY
Evaluation Methodologies
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 2.5
Table 1 has been prepared as a sample river crossing MCDA for this project. As shown, Alternative #4 (with 47
points), would be the preferred alternative for this crossing. Table 1 also graphically portrays that the greatest
advantage with this alternative is that it provides the best long-term stability for the pipeline but will have short-term
recreational impacts.
Table 1 - Typical Crossing Alternatives Decision Matrix
Co
m
p
a
r
i
s
o
n
C
r
i
t
e
r
i
a
Im
p
o
r
t
a
n
c
e
F
a
c
t
o
r
1- Do
No
t
h
i
n
g
2
- Pr
o
t
e
c
t
i
n
P
l
a
c
e
(
A
)
Ri
p
r
a
p
A
r
m
o
r
i
n
g
- Pr
o
t
e
c
t
i
n
P
l
a
c
e
(
B
)
4
- Wa
t
e
r
l
i
n
e
L
o
w
e
r
i
n
g
5
- Sl
i
p
l
i
n
i
n
g
Permitting
Temporary Recreation
Changes to River
Long Term Pipeline
44 47 42
Unit Weighting - 1 = less effective, 5 = most effective
Green = most desirable, Red = least desirable
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.1
3.0 ANALYSIS OF PIPELINE CROSSINGS
3.1 CROSSING 1
Crossing 1 includes the first crossing of both the 27-inch steel pipe (STL) and the 24-inch reinforced concrete pipe
(RCP). This is located south of State Highway 14 downstream of the Canyon mouth. The 27-inch STL and 24-inch
RCP cross nearly perpendicular to the river channel. The Poudre Valley Canal has an outlet structure at this location
which delivers water to the Poudre River. The banks of the channel created for the Charles Hansen Feeder Canal
have been built up with riprap, and the confluence of the two channels is located in-between the two pipe crossings.
No noticeable bank erosion was present at the time of inspection.
3.1.1 Synopsis of Field Data
The geomorphic survey consisted of 3 cross-sections, and a longitudinal profile. The locations and extent of the
cross-sections and longitudinal profile were selected to compare changes in hydraulic conditions throughout the
reach. Cross-section 1 and 2 (XS-01 and XS-02) were taken in a shallow but long pool section. The bank-full width of
XS-01 measured 80 ft, and the bank-full width of XS-02 measured 137 ft. Cross-section 3 (XS-03) was taken at the
head of a mildly sloped riffle, and bank-full width measured 77 ft. The bank-full slope measured from the longitudinal
profile was found to range between 0.2% and 0.5%.
The survey of the 27-inch STL showed ground cover of 6 to 9 ft across the channel. The survey of the 24-inch RCP
had poor coverage, but the one pipe point that was collected showed a ground cover of 8.5 ft. The longitudinal profile
shows the thalweg of the river at an elevation of 6 ft above the 27-inch STL pipe at the beginning of a pool section.
The 24-inch RCP had no survey data within the vicinity of the thalweg measurements for comparison.
Figures 2 through 6 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 1.
LOC #27.13
27" BLOWOFF
N 157537.06
E 158094.78
LOC #27.14
27" AIR/VAC
N 157771.72
E 157876.78
LOC #27.15
27" BLOWOFF
N 157933.09
E 157687.87
0+0
0
1+
0
0
2+
0
0
3+00
4+0
0
5+00
6+00
7+00
7+72.77
9+0
0
9+5
0
.
8
1
LOC #27.12
27" AIR/VAC
N 157084.76
E 158497.26
C-01
XS-01
C-01 XS-0
2
C-0
1 XS
-
0
3
C-0
2
XS
-
0
3
C-01
XS-01
C-01 XS-0
2
C-0
1 XS
-
0
3
LOC #24.14
24" BLOWOFF
N 157980.68
E 158015.85
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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P
M
27" STL LINE
24" RCP LINE
NCITY OF FORT COLLINS
ELECTRIC SUBSTATION
67" STL PVP
27" STL
XING #1
27" STL
XING #1
24" RCP
XING #1
CITY OF GREELEY
RAW WATER LINE
XING
67" PVP
PIPELINE
C-01.0
CROSSING LOCATION #1
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
CHA
R
L
E
S
H
A
N
S
E
N
F
E
E
D
E
R
C
A
N
A
L
CACHE LA PO
U
D
R
E
R
I
V
E
R
FLOW
FLO
W
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
G
U
R
E
2
Profile View: 24" Reinforced Concrete Pipe Section 1
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5200
5205
5210
5215
5220
5200
5205
5210
5215
5220
157+50 158+00 159+00 159+50
Profile View: 27" Steel Pipe Section 1
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5195
5200
5205
5210
5215
5195
5200
5205
5210
5215
158+50 159+00 160+00 161+00
27" STEEL PIPE SECTION
27" STEEL PIPE
EXISTING GROUND
24" RCP
(ONLY ONE POINT)
EXISTING GROUND
24" REINFORCED CONCRETE PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-01.1
CROSSING LOCATION #1
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-01
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
3
Profile View: C1 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5200
5205
5210
5215
5200
5205
5210
5215
0+00 1+00 2+00
Profile View: C1 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5200
5205
5210
5215
5200
5205
5210
5215
0+00 1+00 1+60
BANKFULL WIDTH = 137'
BANKFULL
ELEV: 5209.70'
WATER SURFACE
ELEV: 5205.32'
BANKFULL WIDTH = 80'
BANKFULL
ELEV: 5209.88'
C1 XS-01
C1 XS-02
WATER SURFACE
ELEV: 5205.15'Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-01.2
CROSSING LOCATION #1
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-01
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
4
Profile View: C2 XS-03
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5205
5210
5215
5205
5210
5215
0+00 1+00 1+20
C2 XS-03
BANKFULL WIDTH = 77'
BANKFULL
ELEV: 5213.30'
WATER SURFACE
ELEV: 5208.55'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-01.3
CROSSING LOCATION #1
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-01
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
5
5190
5195
5200
5205
5210
5215
5190
5195
5200
5205
5210
5215
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 8+50
XS
-
0
1
XS
-
0
2
XS
-
0
3
RIVER BED (THALWEG) LONGITUDINAL PROFILE
0.2%0.5%0.4%
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE
BANKFULL PROFILE
RUN GLIDE RIFFLEPOOL
27" STEEL PIPE
ELEV: 5197.64'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-01.4
CROSSING LOCATION #1
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-01
FI
G
U
R
E
6
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.7
3.1.2 Risk Analysis
Crossing 1 is the most downstream crossing location investigated as part of this project. This reach includes
subsurface crossing of both the 27-inch STL and the 24-inch RCP. Although both pipes cross the channel within a
pool, survey showed that the depth of cover through the channel is 6 to 9 feet, and both are at a low risk of exposure
due to vertical degradation. At the approximate crossing location of the 24-inch RCP, the river left bank is in poor
condition. It is located immediately downstream of the confluence with the Charles Hansen Feeder Canal overflow
channel and pushed up against a high terrace, which is likely contributing to the bank erosion shown in Figure 7
below. However, the erosion is not likely severe enough to threaten the integrity of the 24-inch RCP.
Figure 7 Left Bank at Crossing 1
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.8
3.2 CROSSING 2
Crossing 2 includes the 2nd crossing of the 27” STL. This crossing is located south of State Highway 14 and just
downstream of the Canyon mouth. The 27” STL crosses the river at a 45°angle. The survey documented a man-
made berm that was built up 3 to 4 ft above the native floodplain on river right from station 0+00 to 3+50. The
embankment associated with the Poudre Valley canal has encroached on the floodplain on river right (the right side
of the river, looking downstream) from station 6+50 to the end of the reach. The reach exhibits excellent floodplain
access except for the upstream bend near the berm, and downstream adjacent to the canal. An actively eroding bank
of up to 12 ft tall was documented at station 1+00 on river left (the left side of the river, looking downstream). All other
banks were in stable condition including the embankment along the Charles Hansen Feeder Canal.
3.2.1 Synopsis of Field Data
The geomorphic survey consisted of 3 cross-sections, 4 valley cross-sections, a longitudinal profile, and a Wolman
Pebble Count. The locations and extent of the cross-sections and longitudinal profile were selected to compare
changes in hydraulic conditions throughout the reach. Cross-sections 1 and 2 (XS-01 and XS-02) were measured in
the riffle section of the reach. The bankfull width of XS-01 was measured to be 110 ft, and the bankfull width of XS-02
was measured to be 121 ft. Cross-section 3 (XS-03) was measured in the downstream pool with a bankfull width of
77 ft. The valley cross-sections were collected to understand the expansion and contraction experienced at higher
flow events. The 5-year discharge of about 4000 CFS showed substantial contraction followed by expansion through
the reach. Valley XS-01 was measured to be 298 ft, which contracts down to 182 ft and 166 ft at Valley XS-02 and
Valley XS-03 respectively. Moving downstream, the valley then widens to 432 ft at Valley XS-04. The pebble count
was collected in the middle of the riffle at XS-02, with a D50 of 74mm/3” (small cobble) and a D84 of 126 mm/5”
(large cobble). The average bankfull slope measured from the longitudinal profile was 0.5%.
The survey of the 27” STL showed a ground cover of 4 to 7 ft across the channel. The longitudinal profile shows the
thalweg of the river at an elevation of 5.5 ft above the 27” STL in the middle of a riffle section.
Figures 8 through 12 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 2.
LOC #27.14
27" AIR/VAC
N 157771.72
E 157876.78
LOC #27.15
27" BLOWOFF
N 157933.09
E 157687.87
0+00
1+0
0
2+0
0
3+00
4+00
0+0
0
1+
0
0
2+
0
0
3+
0
0
4+
0
0
5+
0
0
6+
0
0
7+
0
0
8+
0
0
9+
0
0
9+
5
0
.
8
1
C-02
XS-01
C-02
XS-02
C-02
XS-0
3
C-0
1 XS-
0
1
C-0
1
XS
-
0
2
C-02
XS-01
C-02
XS-02
C-02
XS-0
3
C-0
1 XS-
0
1
C-0
1
XS
-
0
2
C-0
2
VA
L
L
E
Y
X
S
-
0
1
C-0
2
VAL
L
E
Y
X
S
-
0
2
C-0
2
VAL
L
E
Y
X
S
-
0
3
C-02
VAL
L
E
Y
X
S
-
0
4
LOC #24.14
24" BLOWOFF
N 157980.68
E 158015.85
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
27" STL LINE
24" RCP LINE
N
GREELEY RAW
WATER LINE XING
67" STL PVP
WATERLINE
CH
A
R
L
E
S
H
A
N
S
E
N
F
E
E
D
E
R
C
A
N
A
L
CITY OF FORT COLLINS
ELECTRIC SUBSTATION
27" STL
XING #2
24" RCP
XING #1
27" STL
XING #1
CITY OF GREELEY
RAW WATER LINE
XING
67" PVP
PIPELINE
C-02.0
CROSSING LOCATION #2
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
CACHE LA POUDRE RIVER
FLOW
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
UNSTABLE
ERODING BANK
ARTIFICIAL
BERM
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
G
U
R
E
8
Profile View: 27" Steel Pipe Section 2
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5200
5205
5210
5215
5200
5205
5210
5215
166+50 167+00 168+00 168+50
27" STEEL PIPE SECTION
27" STEEL PIPE
EXISTING GROUND
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-02.1
CROSSING LOCATION #2
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-02
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
9
Profile View: C2 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5210
5215
5220
5225
5210
5215
5220
5225
0+00 1+00 1+90
Profile View: C2 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5207
5210
5215
5220
5207
5210
5215
5220
0+00 1+00 2+00
BANKFULL WIDTH = 121'
BANKFULL
ELEV: 5214.70'
WATER SURFACE
ELEV: 5212.49'
BANKFULL WIDTH = 110'
BANKFULL
ELEV: 5215.12'
C2 XS-01
C2 XS-02
WATER SURFACE
ELEV: 5212.51'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-02.2
CROSSING LOCATION #2
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-02
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
10
Profile View: C2 XS-03
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5205
5210
5215
5205
5210
5215
0+00 1+00 1+20
C2 XS-03
BANKFULL WIDTH = 77'
BANKFULL
ELEV: 5213.30'
WATER SURFACE
ELEV: 5208.55'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-02.3
CROSSING LOCATION #2
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-02
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
11
5200
5205
5210
5215
5220
5225
5200
5205
5210
5215
5220
5225
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 10+50
XS
-
0
1
XS
-
0
2
XS
-
0
3
RIVER BED (THALWEG) LONGITUDINAL PROFILE
0.3%0.3%
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE
BANKFULL PROFILE
POOLRUNPOOLGLIDERIFFLE
27" STEEL PIPE
ELEV: 5205.23'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-02.4
CROSSING LOCATION #2
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-02
FI
G
U
R
E
12
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.14
3.2.2 Risk Analysis
At the crossing 2 location, only the 27” STL pipe crossing the channel within the lower portion of a riffle and the depth
of ground cover over the pipe ranges from 4 to 7 feet. The channel and banks within the immediate vicinity (+- 300’)
were stable with no signs of erosion, degradation, or aggradation. However, the river left bank along the outside of a
meander bend between stations 0+95 – 1+50 is highly unstable and actively eroding, as shown in Figure 13 (A) and
(B) below.
Figure 13 Crossing 2 Left Bank Erosion (A) and (B)
This does not pose an immediate threat to either the 24” STL or 27” RCP. At the termination point of this high bank, a
small chute cutoff high flow channel was observed through the cottonwood gallery on the floodplain on river left. If
the erosion and lateral bank migration continues, there is the potential for down valley migration during a large storm
event. Although the likelihood of the formation of a catastrophic chute cutoff is low, this area should be monitored
following above average storm events for change detection.
While down-valley channel migration is a natural process, this area is likely experiencing accelerated erosion rates
compared to natural conditions. This is likely caused by the presence of an anthropogenically created berm that
occurs on the adjacent right floodplain. The berm, shown as the right over-bank on Cross Section “C2 XS-01” on
sheet “C-02.2” above, is approximately 1.5 times the mean bankfull depth. This artificial entrenchment occurring on
the inside of a meander bend results in increased shear stress and pressure on the outside bank.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.15
3.3 CROSSING 3
Crossing 3 includes the 3rd crossing of the 27” STL. This crossing is located just south of State Highway 14 and at the
mouth of the Canyon. The 27” STL crosses the river at a 15° angle. There is a diversion structure at the downstream
end of this reach that backs up a substantial amount of flow. There is also a large mid-channel bar that extends from
station 8+00 to 11+00 (main channel stationing). Mild bank erosion was documented from station 7+50 to 9+75 (main
channel stationing) on river right. The reach exhibits adequate floodplain access upstream of the mid-channel bar but
lacks floodplain access downstream up to the diversion structure.
3.3.1 Synopsis of Field Data
The geomorphic survey consisted of 4 cross-sections, a longitudinal profile, and a Wolman Pebble Count. The
locations and extent of the cross-sections and longitudinal profile were selected to compare changes in hydraulic
conditions throughout the reach. Cross-sections 1 and 2 (XS-01 and XS-02) were taken in a compound pool section.
The bankfull width of XS-01 was measured to be 108 ft, and the bankfull width of XS-02 was measured to be 110 ft.
Cross-section 3 (XS-03) was taken at the head of riffle where the channel splits into the left channel and the main
channel. The bankfull width of XS-03 was measured to be 251 ft, which is substantially wider than the upstream
sections due to the presence of the mid-channel bar. Cross-section 4 (XS-04) was collected at the tail of the main
channel riffle where the left channel rejoins the main channel. The bankfull width of XS-04 was measured to be 143 ft.
The pebble count was collected at XS-02 in the compound pool section, with a D50 of 45 mm/1-3/4” (very coarse
gravel) and a D84 of 89 mm/3.5” (small cobble). The bankfull slope measured from the longitudinal profile was found
to range between 0.1% and 0.3%.
The survey of the 27” STL showed a ground cover of 5.5 to 8 ft across the channel. The longitudinal profile measured
the thalweg elevation to be 5.5 ft above the elevation of the pipe at the end of the compound pool section.
Figures 14 through 18 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 3.
STATE HIGHWAY 14
POUDRE VALLEY CA
N
A
L
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
LOC #24.XX
24" AIR/VAC
N 159485.05
E 156177.64
LOC #24.XX
CPTS
N 159486.14
E 156110.43LOC #24.XX
24" AIR/VAC
N 159508.60
E 155972.37
LOC #27.XX
27" AIR/VAC
N 158901.12
E 156197.12
0+00 1+00 2+00 3+00 4+00
5+00
6+00 7+00 8+00
9+00
10+00
11+0
0
12+00 13+00
14+0
0
15+0
0
16+0
016+4
3
.
1
6
0+00
1+00
2+00
3+
0
0
4+00
5+00 6+00
7+00
7+83.35
C-
0
3
XS
-
0
1
C-
0
3
XS
-
0
2
C-
0
3
XS
-
0
3
C-
0
3
XS
-
0
4
C-0
3
XS
-
0
3
C-
0
3
XS
-
0
4
C-
0
3
XS
-
0
2
C-
0
3
XS
-
0
1
STATE HIGHWAY 14
STATE HIGHWAY 14
POUDRE VALLEY CANA
L
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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2
0
5
3
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2
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1
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-
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-
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1
0
20
1
8
.
0
7
.
0
5
1
:
0
4
:
5
3
P
M
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
27" STL
XING #3
POUDRE
VALLEY
CANAL
C-03.0
CROSSING LOCATION #3
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
N
27" STL LINE
24" RCP LINE
FLOW
FLO
W
LONGITUDINAL
PROFILE BASE
(LEFT CHANNEL)
KEY MAP
1" = 1000'
MID-CHANNEL
ISLAND/BAR
FORMATION
MILD BANK
EROSION
LONGITUDINAL
PROFILE BASE
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
DIVERSION
STRUCTURE
FI
G
U
R
E
1
4
Profile View: 27" Steel Pipe Section 3
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5215
5220
5225
5230
5235
5215
5220
5225
5230
5235
191+00 192+00 193+00 194+00 195+00 196+00 196+60
27" STEEL PIPE
EXISTING GROUND
27" STEEL PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-03.1
CROSSING LOCATION #3
27" STL PIPELINE PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-03
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
1
5
Profile View: C3 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5225
5230
5235
5240
5225
5230
5235
5240
0+00 1+00 2+00 2+40
Profile View: C3 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5220
5225
5230
5235
5240
5220
5225
5230
5235
5240
0+00 1+00 2+00 3+00 3+20
WATER SURFACE
ELEV: 5229.26'
BANKFULL WIDTH = 110'
BANKFULL
ELEV: 5232.04'
WATER SURFACE
ELEV: 5228.86'
BANKFULL WIDTH = 108'
BANKFULL
ELEV: 5232.40'
C3 XS-01
C3 XS-02
27" STEEL PIPE
ELEV: 5222.45'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-03.2
CROSSING LOCATION #3
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-03
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
1
6
Profile View: C3 XS-03
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5218
5220
5225
5230
5235
5218
5220
5225
5230
5235
0+00 1+00 2+00 3+00
Profile View: C3 XS-04
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5223
5225
5230
5235
5240
5223
5225
5230
5235
5240
0+00 1+00 2+00 2+40
WATER SURFACE
ELEV: 5227.66'
WATER SURFACE
ELEV: 5226.12'
C3 XS-03
C3 XS-04
BANKFULL WIDTH = 251'
BANKFULL
ELEV: 5231.10'
BANKFULL WIDTH = 143'
BANKFULL
ELEV: 5230.60'
WATER SURFACE
ELEV: 5227.66'
27" STEEL PIPE
ELEV: 5221.60'
MILD BANK
EROSION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-03.3
CROSSING LOCATION #3
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-03
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
1
7
5210
5215
5220
5225
5230
5235
5240
5210
5215
5220
5225
5230
5235
5240
1+50 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11+00 12+00 13+00 13+55
5215
5220
5225
5230
5235
5215
5220
5225
5230
5235
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 8+50
XS
-
0
1
XS
-
0
2
XS
-
0
3
XS
-
0
4
RIVER BED (THALWEG) LONGITUDINAL PROFILE
RIVER BED (THALWEG) LONGITUDINAL PROFILE (LEFT CHANNEL)
0.3%0.1%0.3%
0.2%
XS
-
0
3
XS
-
0
4
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE
27" STEEL PIPE
ELEV: 5221.81'
BANKFULL PROFILE
POOLRUNCOMPOUND POOL GLIDE RIFFLE
POOL GLIDE RIFFLE POOL GLIDE RIFFLERUN
27" STEEL PIPE
ELEV: 5221.08'
(CENTER)
27" STEEL PIPE
ELEV: 5220.64'
(RIGHT BANK)
27" STEEL PIPE
ELEV: 5222.99'
(LEFT BANK)
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-03.4
CROSSING LOCATION #3
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-03
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
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1
8
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.21
3.3.2 Risk Analysis
Crossing 3, located approximately 1,000’ upstream of the Greeley Water Treatment Plant Diversion Dam, includes
the crossing of the 27” STL waterline. The pipe crosses the river just upstream of a large mid-channel bar/island,
which is actively aggrading, through a pool and glide section. Presence of a mid-channel bars indicate a localized
reduction in channel competency and typically results in lateral bank erosion. The 24” STL waterline has a sufficient
depth of cover of 5.5 to 8 feet beneath the channel bottom and the top of pipe is lower than the downstream invert of
the Diversion Dam. As such, there is a very low risk of exposure due to vertical degradation. However, the right bank
at the crossing location is experiencing some minor bank erosion caused by the adjacent mid-channel bar. Figure 19
below, demonstrates an example of the lateral erosion, with the waterline marker visible in the background.
Figure 19 Crossing 3 Right Bank Erosion
The overall risk of lateral bank erosion causing pipe exposure is relatively low in this location because of the low bank
height ratio (ratio of bankfull elevation to adjacent floodplain elevation), and the 7 to 8 feet of cover. However, this
location should be monitored after above average storm discharges for change detection.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.22
3.4 CROSSING 4
Crossing 4 includes the 2nd crossing of the 24” RCP and the 4th crossing of the 27” STL. The crossing is located just
downstream of a large diversion structure adjacent to State Highway 14. Both the 24” RCP and the 27” RCP cross
the channel at a 35-degree angle. Massive sediment deposition characterizes the reach downstream of the diversion
structure. The deposition has created two channels that flow around a large mid-channel bar for the entirety of the
reach.
3.4.1 Synopsis of Field Data
No geomorphic data was collected because the diversion structure heavily influences the geomorphology of the
reach. The pipe surveys showed a ground cover of 3.5 to 4 ft over the 24” RCP, and a ground cover of 4.5 to 5 ft over
the 27” STL.
Figures 20 and 21 provide the Plan, Pipe Profiles for Crossing 4.
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LOC #24.18
24" AIR/VAC
N 160946.64
E 153189.90
LOC #24.19
24" AIR/VAC
N 161703.88
E 152607.12
LOC #27.22
27" AIR/VAC
N 161710.99
E 152497.21
LOC #27.20
27" AIR/VAC
N 161141.43
E 153026.51
LOC #27.21
27" BLOWOFF
N 161242.78
E 152960.82
STATE HIGHWAY 14
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Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
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27" STL LINE
24" RCP LINE
N
27" STL
XING #4
24" RCP
XING #2
27" STL
XING #5
24" RCP
XING #3
PICNIC
ROCK
C-04.0
CROSSING LOCATION #4
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
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1" = 1000'
MILD BANK
EROSION
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
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POUDRE VALLEY CANAL
DIVERSION STRUCTURE
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Profile View: 24" Reinforced Concrete Pipe Section 2
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5230
5235
5240
5245
5250
5230
5235
5240
5245
5250
227+50 228+00 229+00 230+00 230+50
Profile View: 27" Steel Pipe Section 4
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5230
5235
5240
5245
5250
5230
5235
5240
5245
5250
227+00 228+00 229+00 230+00
27" STEEL PIPE
EXISTING GROUND
24" RCP
EXISTING GROUND
27" STEEL PIPE SECTION
24" REINFORCED CONCRETE PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-04.1
CROSSING LOCATION #4
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-04
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
21
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.25
3.4.2 Risk Analysis
Crossing 4, located just downstream of the Poudre Valley Canal Diversion Dam, includes the crossings of both the
27” STL and the 24” RCP pipes. The proximity to the diversion dam has created a heavily modified reach, and
therefore no geomorphic data was collected. Overall, field observations concluded that this is a fairly low risk area.
However, it is understood that some erosion occurred at the crossing location during the 2013 flood and was
addressed with bank armoring.
Just upstream of the pipe crossing, mild bank erosion was observed on the left bank immediately downstream of the
diversion dam, as shown in Figure 22 below.
Figure 22 Crossing 4 Left Bank Erosion (A) and (B)
Although this localized erosion poses minimal risk to the pipe crossings, it should be monitored follow above average
discharge events for change detection.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.26
3.5 CROSSING 5
Crossing 5 includes the 3rd crossing of the 24” RCP and the 5th crossing locations of the 27” STL. This crossing is
located adjacent to the Picnic Rock recreation area. The 24” RCP crosses the river at a 70° angle and the 27” STL
crosses nearly perpendicular to the channel. The reach is bordered on river right by a large vertical bedrock outcrop
with moderate floodplain access on river left. There are no substantial anthropogenic modifications noted within the
reach. No substantial bank erosion was observed within the reach.
3.5.1 Synopsis of Field Data
The geomorphic survey consisted of 1 cross-section, and a longitudinal profile. The locations and extent of the cross-
section and longitudinal profile were selected to compare the changes in hydraulic conditions throughout the reach.
Cross-section 1 (XS-01) was taken near the head of a riffle section, with the bankfull width measuring 138 ft. The
average bankfull slope measured from the longitudinal profile was 0.5%.
The survey of the 24” RCP showed a ground cover of 6 to 8 ft across the channel. The survey of the 27” STL showed
a ground cover of 5.5 to 6 ft across the channel. The longitudinal profile measured the thalweg elevation at 4.0 ft
above the 24” RCP and 4.2 ft above the 27” STL. The 24” RCP was in a glide section, and the 27” STL was located
just downstream at the head of riffle.
Figures 23 through 26 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 5.
LOC #24.19
24" AIR/VAC
N 161703.88
E 152607.12
LOC #27.22
27" AIR/VAC
N 161710.99
E 152497.21
LOC #27.23
27" BLOWOFF
N 161729.05
E 152411.12
LOC #27.20
27" AIR/VAC
N 161141.43
E 153026.51
LOC #27.21
27" BLOWOFF
N 161242.78
E 152960.82
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Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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27" STL LINE
24" RCP LINE
N
27" STL LINE
24" RCP LINE
27" STL
XING #4
27" STL
XING #5
24" RCP
XING #3
24" RCP
XING #2
PICNIC
ROCK
C-05.0
CROSSING LOCATION #5
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
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FLOW
FLO
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LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
PICNIC ROCK
NATURAL AREA
PARKING LOT
FI
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2
3
Profile View: 24" Reinforced Concrete Pipe Section 3
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5240
5245
5250
5255
5260
5265
5240
5245
5250
5255
5260
5265
235+00 236+00 237+00 237+50
Profile View: 27" Steel Pipe Section 5
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5240
5245
5250
5255
5260
5265
5270
5240
5245
5250
5255
5260
5265
5270
234+00 235+00 236+00 237+00
27" STEEL PIPE
EXISTING GROUND
24" RCP
EXISTING GROUND
27" STEEL PIPE SECTION
24" REINFORCED CONCRETE PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-05.1
CROSSING LOCATION #5
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-05
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
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E
2
4
Profile View: C5 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5240
5245
5250
5255
5260
5240
5245
5250
5255
5260
0+00 1+00 2+00 2+30
WATER SURFACE
ELEV: 5251.53'
BANKFULL WIDTH = 138'
BANKFULL
ELEV: 5254.08'
C5 XS-01
24" RCP
ELEV: 5243.53'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-05.2
CROSSING LOCATION #5
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-05
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
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E
25
5240
5245
5250
5255
5260
5265
5240
5245
5250
5255
5260
5265
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 10+50
XS
-
0
1
RIVER BED (THALWEG) LONGITUDINAL PROFILE
27" STEEL PIPE
ELEV: 5246.09'
EXISTING RIVER BED
(THALWEG) PROFILE WATER SURFACE PROFILE
27" RCP
ELEV: 5245.90'
0.5%
BANKFULL PROFILE
RIFFLEPOOLRIFFLERUNGLIDE
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-05.3
CROSSING LOCATION #5
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-05
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
G
U
R
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26
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.31
3.5.2 Risk Analysis
Crossing 5 is located near the Picnic Rock recreation area and includes crossings of both the 24” RCP and 27” STL
pipes. Both pipes cross at the transition point between the end of a glide and head of a riffle, which is an ideal
location from a vertical bed degradation risk perspective. No channel or bank erosion was observed throughout this
reach and risk to the pipes is minimal.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.32
3.6 CROSSING 6
Crossing 6 includes the 4th crossing of the 24” RCP and the 6th crossing of the 27” STL. The crossing is located
upstream of a bridge on State Highway 14. The 24” RCP crosses the channel at approximately a 60° angle, and the
27” STL crosses at approximately a 70°angle. The reach begins with a vertical bedrock wall on river left, then opens
to an overwide channel with moderate floodplain access. At station 7+50 the channel splits due to a mid-channel bar
and rejoins at station 10+50, just before the downstream pool. At the downstream end of the reach, the bedrock
controls the elevation at the tail of the riffle as the river enters a deep narrow pool before the bridge. There was no
substantial bank erosion observed in the reach despite the presence of a mid-channel bar around the bend.
3.6.1 Synopsis of Field Data
The geomorphic survey consisted of 3 cross-sections, a longitudinal profile and a Wolman Pebble Count. The
locations and extent of the cross-section and longitudinal profile were selected to compare the changes in hydraulic
conditions throughout the reach. Cross-section 1 (XS-01) was taken in a glide section, just before the head of riffle.
The bankfull width of XS-01 was measured at 122 ft. Cross-section 2 (XS-02) was taken in the middle of a shallow
pool with a bankfull width measured at 115 ft. Cross-section 3 (XS-03) was taken at the head of a riffle and with a
bankfull width of 183 ft. The pebble count was collected at XS-03 at the head of riffle with a D50 of 58 mm/2-1/4” (very
coarse gravel) and a D84 of 87 mm/3.5” (small cobble). The bankfull slope measured from the longitudinal profile was
found to range between 0.2% and 0.8%.
The survey of the 24” RCP showed a ground cover of 9 to 10 ft across the channel. The 27” STL survey showed a
ground cover of 4 to 5 ft across the channel. The longitudinal profile measured a thalweg elevation of 8 ft above the
24” RCP at the head of a riffle, and an elevation of 3 ft above the 27” STL in the middle of a riffle.
Figures 27 through 31 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 6.
ST
A
T
E
H
I
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A
Y
1
4
LOC #24.22
24" AIR/VAC
N 166946.67
E 150173.62
LOC #24.24
24" BLOWOFF
N 167485.02
E 150262.09
LOC #27.25
27" AIR/VAC
N 167041.68
E 150092.44
LOC #27.26
27" BLOWOFF
N 167162.84
E 150107.55
LOC #27.XX
27" AIR/VAC
N 168015.83
E 150534.14
0+0
0
1+0
0
2+
0
0
3+
0
0
4+
0
0
5+
0
0
6+
0
0
7+
0
0
8+
0
0
9+
0
0
10+
0
0
11+0
0
11+9
4
.
8
8
C-06
XS-01
C-06
XS-02
C-06
XS-03
C-06XS-03
C-06
XS-02
C-06
XS-01
CA
C
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STATE
H
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1
4
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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27" STL LINE
24" RCP LINE
27" STL
XING #6
24" RCP
XING #4
INVERTED
SIPHON
C-06.0
CROSSING LOCATION #6
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
CAC
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
FLO
W
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
G
U
R
E
2
7
Profile View: 24" Reinforced Concrete Pipe Section 4
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5297
5300
5305
5310
5315
5320
5297
5300
5305
5310
5315
5320
315+00 316+00 317+00 318+00
Profile View: 27" Steel Pipe Section 6
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5300
5305
5310
5315
5320
5300
5305
5310
5315
5320
316+00 317+00 318+00 319+00
27" STEEL PIPE
EXISTING GROUND
24" REINFORCED CONCRET PIPE SECTION
24" RCP
EXISTING GROUND
27" STEEL PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-06.1
CROSSING LOCATION #6
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-06
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
28
Profile View: C6 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5307
5310
5315
5320
5325
5307
5310
5315
5320
5325
0+00 1+00 1+70
Profile View: C6 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5305
5310
5315
5320
5325
5305
5310
5315
5320
5325
0+00 1+00 2+00 2+30
WATER SURFACE
ELEV: 5312.31'
BANKFULL WIDTH = 115'
BANKFULL
ELEV: 5314.80'
WATER SURFACE
ELEV: 5312.97'
BANKFULL WIDTH = 122'
BANKFULL
ELEV: 5315.80'
C6 XS-01
C6 XS-02
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-06.2
CROSSING LOCATION #6
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-06
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
29
Profile View: C6 XS-03
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5298
5300
5305
5310
5315
5320
5298
5300
5305
5310
5315
5320
0+00 1+00 2+00 3+00 3+50
WATER SURFACE
ELEV: 5311.91'
C6 XS-02
BANKFULL WIDTH = 183'
BANKFULL
ELEV: 5313.90'
24" RCP
ELEV: 5301.37'
27" STEEL PIPE
ELEV: 5308.97'
C6 XS-03
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-06.3
CROSSING LOCATION #6
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-06
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
G
U
R
E
30
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-06.4
CROSSING LOCATION #6
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-06
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
G
U
R
E
31
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.38
3.6.2 Risk Analysis
Crossing 6 is located just upstream of a State Highway 14 bridge within private and public land and includes the
crossing of both the 24” RCP and the 27” STL. The 24” RCP crosses the river at the end of a glide section through
the head of a riffle section. This crossing location is an ideal location from a vertical bed degradation risk perspective.
The 27” STL crosses the river in the middle of a riffle section and under a mid-channel bar. The presence of a mid-
channel bar indicates aggradation occurring from a lack of sediment transport competency that typically results in
lateral bank erosion. Interestingly, no substantial bank erosion was observed within the vicinity of the pipe crossings.
Both the 27” STL and the 24” RCP have sufficient depth of cover, 9 to 10 ft, and 4 to 5 ft respectively. As such, there
is a low risk of exposure due to vertical degradation.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.39
3.7 CROSSING 7
Crossing 7 includes the 5th crossing of the 24” RCP and the 7th crossing of the 27” STL. The 24” RCP and the 27”
STL cross the channel at a 50° angle. The reach begins with a tight left bend that is controlled on the outside by a
large vertical bedrock wall. The channel and floodplain widen downstream and allow for moderate floodplain access.
At the downstream end, the channel bends back to the right and loses floodplain access.
3.7.1 Synopsis of Field Data
The geomorphic survey consisted of 2 cross-sections, a longitudinal profile, and a Wolman Pebble Count. The
locations and extent of the cross-section and longitudinal profile were selected to compare the changes in hydraulic
conditions throughout the reach. Cross-section 1 (XS-01) was taken at the head of a riffle, with the bankfull width
measuring 114 ft. Cross-section 2 (XS-02) was taken in the middle of the same riffle, and had a bankfull width of 113
ft. The pebble count was collected at XS-02 and resulted in a D50 of 58 mm/2-1/4” (very coarse gravel) and a D84 of
121 mm/4-3/4” (small cobble). The average bankfull slope measured from the longitudinal profile was found to be
0.5%.
The survey of the 24” RCP did not collect any pipe location shots. The survey was made from best efforts to identify
the location of the pipe based on the location of the 24” blow off on river left and a pipe marker on river right.
However, the survey missed the pipe crossing location by about 25 ft horizontally. To supplement the absence of pipe
elevation shots, the survey data (collected September 2017) from the “Poudre Pipeline Rehabilitation for the 24”
RCP” (Stantec, 2017) was compared with the data from this study. Projecting the pipe elevation from the 2017 survey
onto the surveyed pipe cross-section data showed marginal ground cover (Figure 33, Drawing C-07.1). Due to the
horizontal discrepancy between the ground shots and the pipe shots, the data integrity of the 24” RCP section is
marginal. Projecting the pipe crossing elevation from the 2017 survey onto the geomorphic thalweg profile showed a
potential pipe exposure of 1 ft (Figure 35, Drawing C-07.3). This potential exposure could have been missed in the
field by both crews with a water depth of 3 ft above the exposure. This discovery warrants further investigation during
low flow conditions to confirm what the data are showing. The 27” STL survey showed a ground cover of 6 to 8 ft. The
longitudinal profile showed a thalweg elevation of 4 ft above the 27” STL at the head of a riffle.
Figures 32 through 35 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 7.
LOC #24.XX
24" AIR/VAC
N 168322.86
E 150446.80
LOC #24.26
24" BLOWOFF
N 168936.78
E 149884.69
LOC #27.28
27" BLOWOFF
N 168829.68
E 150270.28
0+00
1+00
2+0
0
3+
0
0
4+0
0
5+0
0
6+0
0
7+00
7+53.5
5
C-07 XS-0
1
C-0
7 XS-
0
2
C-07 XS-0
1
C-0
7 XS-
0
2
LOC #27.29
27" AIR/VAC
N 169017.02
E 149739.44
CAC
H
E
L
A
P
O
U
D
R
E
R
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V
E
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H
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1
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STATE
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1
4
CAC
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P
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D
R
E
R
I
V
E
R
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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27" STL LINE
24" RCP LINE
27" STL
XING #7
24" RCP
XING #5
24" RCP
XING #8
INVERTED
SIPHON
C-07.0
CROSSING LOCATION #7
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
STAT
E
H
I
G
H
W
A
Y
1
4
FLOW
FLO
W
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
MUNROE DIVERSION
SIPHON
FI
G
U
R
E
3
2
Profile View: 24" Reinforced Concrete Pipe Section 5
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5320
5325
5330
5320
5325
5330
332+50 333+00 334+00 335+00
Profile View: 27" Steel Pipe Section 7
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5315
5320
5325
5330
5335
5315
5320
5325
5330
5335
335+50 336+00 337+00 338+00
27" STEEL PIPE
EXISTING GROUND
24" RCP
27" STEEL PIPE SECTION
24" REINFORCED CONCRETE PIPE SECTION
EXISTING GROUND
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-07.1
CROSSING LOCATION #7
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-07
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
3
3
Profile View: C7 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5315
5320
5325
5330
5335
5315
5320
5325
5330
5335
0+00 1+00 1+80
Profile View: C7 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5320
5325
5330
5335
5320
5325
5330
5335
0+00 1+00 2+00
WATER SURFACE
ELEV: 5324.38'
BANKFULL WIDTH = 113'
BANKFULL
ELEV: 5327.06'
WATER SURFACE
ELEV: 5325.18'
BANKFULL WIDTH = 114'
BANKFULL
ELEV: 5327.50'
C7 XS-01
C7 XS-02
27" STEEL PIPE
ELEV: 5327.45'
27" STEEL PIPE
ELEV: 5318.98'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-07.2
CROSSING LOCATION #7
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-07
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
34
5310
5315
5320
5325
5330
5335
5310
5315
5320
5325
5330
5335
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 8+50
XS
-
0
1
XS
-
0
2
RIVER BED (THALWEG) LONGITUDINAL PROFILE
27" STEEL PIPE
ELEV: 5319.11'
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE0.4%0.5%0.5%
BANKFULL PROFILE
GLIDERUNPOOL RIFFLE
24" RCP
ELEV: 5322.22'
(POTENTIAL EXPOSURE)
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-07.3
CROSSING LOCATION #7
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-07
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
G
U
R
E
35
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.44
3.7.2 Risk Analysis
Crossing 7 includes the crossing of both the 24” RCP and the 27” STL. The 24” RCP is considered a moderate risk
crossing because of the uncertainty associated with the waterline survey and potential pipe exposure, and because it
crosses through a pool section. Pool sections have a greater risk of vertical degradation especially at high flow
events. The 27” STL is considered a low risk crossing because it crosses the river in a glide section. This is
considered the least hazardous point for a pipe crossing because glide sections are more prone to aggradation rather
than degradation.
3.7.3 Evaluation of Alternatives
3.7.3.1 Alternative 1 – Leave As-Is and Monitor
The first alternative is to leave the existing conditions as-is and monitor the bank erosion on an annual basis (after
spring runoff), as well as after any flow event greater than the bankfull discharge. This approach is most cost-effective
in the short term but has an increased risk of damage to the pipe in a large flow event. This alternative is not
advisable as a sustainable long-term solution.
3.7.3.2 Alternative 2 - Protect in Place (A) with Riprap Armoring
Alternative 2 is to leave the pipe in place and armor the pipe exposure with riprap. Patching the problem is relatively
low impact and cost effective in the short-term. The longevity of this solution is uncertain, but statistically it will last
about 10 years. This estimate is based on hydraulic analysis which shows 30” diameter riprap being moved during a
10-year flow event.
3.7.3.3 Alternative 3 - Protect in Place (B) with Articulated Concrete Mat Protection
Alternative 3 is to leave the pipe in place and armor the pipe with an articulated concrete mat. This alternative
provides a robust solution for the integrity of the pipe (if it is exposed) but does not address risks associated with
further channel adjustment (i.e. vertical degradation).
3.7.3.4 Alternative 4 - Waterline Lowering
Alternative 4 is to lower the waterline in the vicinity of the 24-inch RCP crossing to achieve a depth of cover of at least
4 to 6 ft. This is a high impact, and high cost solution, but does ensure the longevity of the solution. By providing an
adequate depth of cover, the vertical channel erosion will not expose the pipe in the future.
3.7.3.5 Alternative 5 - Sliplining.
Alternative 5 for improving Crossing 7 is to slipline the 27-inch STL pipe section from station 330+50 to 335+00.
Sliplining is a relatively low impact alternative that provides an inert liner inside the pipeline. It is effective for sealing
the pipe through the section and preventing leaks but adds very little to the structural integrity of the pipe. Therefore,
as a long-term option, Alternative 5 does not protect the pipe crossing from vertical channel erosion.
Plan sheets were prepared showing Crossing 7 alternatives 2 and 3 in Figures 36 and 37, as follows:
LOC #24.XX
24" AIR/VAC
N 168322.86
E 150446.80
LOC #24.26
24" BLOWOFF
N 168936.78
E 149884.69
LOC #27.28
27" BLOWOFF
N 168829.68
E 150270.28
LOC #27.29
27" AIR/VAC
N 169017.02
E 149739.44
0+00
1+00
2+0
0
3+
0
0
4+
0
0
5+0
0
6+0
0
7+00
7+53.5
5
C-07 XS-0
1
C-0
7 XS-
0
2
C-07 XS-0
1
C-0
7 XS-
0
2
W. C. GRAVES JR AND ARISTA
GRAVES 1958
W 1
2 SE 1
4 S 4 T8N R70W
W. C. GRAVES JR AND ARISTA
GRAVES 1958
E 1
2 NW 1
4 S 4 T8N R70W
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-07-ALTERNATIVES
v:
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2
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5
3
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20
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.
2
8
9
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3
4
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0
8
A
M
N
27" STL LINE
24" RCP LINE
27" STL
XING #6
27" STL
XING #7
24" RCP
XING #5
C-07.4
CROSSING LOCATION #7
24" RCP PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW KEY MAP
1" = 1000'
PIPE
EXPOSURE
ARMOR AND BURY
EXPOSED PIPE
WITH RIPRAP
ALTERNATIVE 2
24" RCP
XING #4
MONROE DIVERSION SIPHON
27" STL
XING #8
EXISTING
EASEMENT
EXISTING
EASEMENT
LONGITUDINAL
PROFILE BASE
FI
G
U
R
E
36
LOC #24.XX
24" AIR/VAC
N 168322.86
E 150446.80
LOC #24.26
24" BLOWOFF
N 168936.78
E 149884.69
LOC #27.28
27" BLOWOFF
N 168829.68
E 150270.28
LOC #27.29
27" AIR/VAC
N 169017.02
E 149739.44
0+00
1+00
2+0
0
3+
0
0
4+
0
0
5+0
0
6+0
0
7+00
7+53.5
5
C-07 XS-0
1
C-0
7 XS-
0
2
C-07 XS-0
1
C-0
7 XS-
0
2
W. C. GRAVES JR AND ARISTA
GRAVES 1958
W 1
2 SE 1
4 S 4 T8N R70W
W. C. GRAVES JR AND ARISTA
GRAVES 1958
E 1
2 NW 1
4 S 4 T8N R70W
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-07-ALTERNATIVES
v:
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s
20
1
8
.
0
6
.
2
8
9
:
3
4
:
1
3
A
M
N
27" STL LINE
24" RCP LINE
27" STL
XING #6
27" STL
XING #7
24" RCP
XING #5
C-07.5
CROSSING LOCATION #7
24" RCP PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
PIPE
EXPOSURE
INSTALL
ARTICULATED
CONCRETE MAT
ALTERNATIVE 3
24" RCP
XING #4
MONROE DIVERSION SIPHON
27" STL
XING #8
EXISTING
EASEMENT
EXISTING
EASEMENT
FI
G
U
R
E
37
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.47
An MCDA for Crossing 7 shows the weighted totals in Table 2. As shown, Alternative 4 is the most desirable.
Table 2 - Crossing 7 Alternatives Decision Matrix
Co
m
p
a
r
i
s
o
n
C
r
i
t
e
r
i
a
Im
po
r
t
a
n
c
e
F
a
c
t
o
r
1- Do
N
o
t
h
ing
2
- Pr
o
t
e
c
t
i
n
P
l
a
c
e
(
A
)
Ri
p
r
a
p
A
r
m
o
r
i
n
g
- Pr
o
t
e
c
t
i
n
P
l
a
c
e
(
B
)
4
- Wa
t
e
r
l
i
n
e
L
o
w
e
r
i
n
g
5
- Sl
i
p
l
i
n
i
n
g
Permitting Requirements 2 5 10 3 6 3 6 2 4 3 6
Temporary Recreation
Changes to River
47
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.48
3.8 CROSSING 8
Crossing 8 includes the 8th crossing of the 27” STL. The 27” STL crosses the channel at a 40° angle. Most of the
reach is confined by bedrock on river left, and moderate floodplain access on river right until station 6+00 where the
embankment from State Highway 14 encroaches on the floodplain. Downstream of station 6+00 the channel
becomes confined with minimal floodplain access.
3.8.1 Synopsis of Field Data
The geomorphic survey consisted of 2 cross-sections, a longitudinal profile, and a Wolman Pebble Count. The
locations and extent of the cross-section and longitudinal profile were selected to compare the changes in hydraulic
conditions throughout the reach. Cross-section 1 (XS-01) was taken at the head of a riffle section with a bankfull
width measuring 130 ft. Cross-section 2 (XS-02) was taken just downstream in the middle of a riffle section with a
bankfull width of 125 ft. The pebble count was collected at XS-02 and resulted in at D50 of 52 mm/2” (very coarse
gravel) and a D84 of 93 mm/3-3/4” (small cobble). The average bankfull slope measured from the longitudinal profile
ranged from 0.4% to 0.6%.
The survey of the 27” STL showed a ground cover of 9.5 to 10 ft. The longitudinal profile measured a thalweg
elevation of 7 ft above the 27” STL in a glide section.
Figures 38 through 41 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 8.
CACHE LA PO
U
D
R
E
R
I
V
E
R
STATE HIG
H
W
A
Y
1
4
CACHE LA PO
U
D
R
E
R
I
V
E
R
LOC #24.27
24" AIR/VAC
N 170050.70
E 149146.33
LOC #27.30
27" BLOWOFF
N 169921.46
E 149109.06
0+00 1+00 2+00
3+00
4+0
0
5+0
0
6+0
0
7+00
8+008+01.6
3
C-0
8
XS-
0
1
C-0
8
XS
-
0
2
C-0
8
XS-
0
2
C-0
8
XS
-
0
1
CA
C
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
STA
T
E
H
I
G
H
W
A
Y
1
4
CA
C
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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27" STL LINE
24" RCP LINE
27" STL
XING #7
27" STL
XING #8
27" STL
XING #9
24" RCP
XING #5
C-08.0
CROSSING LOCATION #8
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
G
U
R
E
3
8
Profile View: 27" Steel Pipe Section 8
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5325
5330
5335
5340
5345
5325
5330
5335
5340
5345
352+00 353+00 354+00 354+50
27" STEEL PIPE
EXISTING GROUND
27" STEEL PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-08.1
CROSSING LOCATION #8
27" STL PIPELINE PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-08
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
39
Profile View: C8 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5325
5330
5335
5340
5345
5325
5330
5335
5340
5345
0+00 1+00 2+002+15
Profile View: C8 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5325
5330
5335
5340
5345
5325
5330
5335
5340
5345
0+00 1+00 2+00
WATER SURFACE
ELEV: 5336.89'
BANKFULL WIDTH = 125'
BANKFULL
ELEV: 5340.00'
WATER SURFACE
ELEV: 5337.17'
BANKFULL WIDTH = 130'
BANKFULL
ELEV: 5340.10'
C8 XS-02
27" STEEL PIPE
ELEV: 5328.11'
27" STEEL PIPE
ELEV: 5328.34'
C8 XS-01
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-08.2
CROSSING LOCATION #8
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-08
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
40
5320
5325
5330
5335
5340
5345
5350
5320
5325
5330
5335
5340
5345
5350
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 9+50
XS
-
0
1
XS
-
0
2
RIVER BED (THALWEG) LONGITUDINAL PROFILE
27" STEEL PIPE
ELEV: 5327.36'
EXISTING RIVER BED
(THALWEG) PROFILE WATER SURFACE PROFILE
0.5%
0.4%0.6%
BANKFULL PROFILE
RUNRIFFLE RIFFLEPOOLGLIDE
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-08.3
CROSSING LOCATION #8
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-08
Horiz
Scale
Vert
Scale
0'100'
0'10'
FI
G
U
R
E
41
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.53
3.8.2 Risk Analysis
Crossing 8 includes a crossing of the 27” STL pipeline. The pipe crosses through the end of a pool section, a glide,
and the head of a riffle section. The glide and head of riffle segment of pipe cross at an ideal location from a vertical
bed degradation risk perspective. However, the pool segment of the crossing does leave a small segment of the
pipeline open to potential for vertical degradation. The 27” STL has substantial cover of 7 to 10 ft. As such, there is a
low risk of exposure due to vertical degradation.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.54
3.9 CROSSING 9
The 9th crossing of the 27” STL Waterline is located just downstream of the entrance to Gateway park and is
currently exposed in two locations. The steel waterline crosses the channel at an approximate 75° angle in
downstream direction, through a riffle and pool section. The channel and banks throughout the reach have been
anthropogenically modified to accommodate an old roadway and rock wall, berms created during the construction of
the 24” RCP waterline, and State Highway 14. The anthropogenic influences have resulted in a reach that contains
rapid change in geomorphic conditions which have ultimately led to excessive erosion around the pipeline crossing,
which are discussed in greater detail below. Overall the reach can be characterized by an overwide section with a
rapid transition to a narrow and confined section.
3.9.1 Synopsis of Field Data
The geomorphic survey consisted of 5 cross sections, a longitudinal profile, and a Wolman Pebble Count. The
locations and extent of the cross sections and longitudinal profile were selected to compare and explain changes in
hydraulic conditions throughout the reach. The overwide “Upstream Reach” (Cross Sections 1 and 2), is
characterized by a shallow riffle along river left and an extended lateral pool along the right bank. The right bank
consists of a vertical stacked rock wall that provides minimal hydraulic resistance at elevated discharge stages. The
left bank has low to moderate floodplain access, with an anthropogenically created berm approximately 5’ above the
bankfull stage. On average, the bankfull width through the upper portion of the reach is 120-150’. The “Downstream
Reach” includes Cross Sections 3-5. Cross Section 3 is located through a riffle at the point of constriction, just
upstream of the exposed waterline, where the bankfull channel width necks down to ~90’. Cross Sections 4 and 5 are
located adjacent to the exposed pipe and have a similar bankfull width as cross section 3. This Downstream Reach
(XS 3-5), is significantly narrower and more confined than the upper section, which is theorized to be one of the main
drivers for the observed erosion at the pipe crossing location.
The implications of a rapid channel and floodplain constriction can be explained and quantified by evaluating the
hydraulic conditions throughout the transition area. Several different hydraulic metrics were analyzed for flows
ranging from bankfull to the estimated 100-year and are presented in Figures 42 through 45 below.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.55
Figure 42 Discharge vs Shear Stress
Figure 43 Discharge vs Unit Stream Power
1
10
1000 10000
Sh
e
a
r
S
t
r
e
s
s
(
l
b
/
f
t
2)
Discharge (cfs)
Discharge vs Shear Q vs Shear XS1
Q vs Shear XS2
Q vs Shear XS3
Q vs Shear XS4
Q vs Shear XS5
Bankfull
5-year
10-year
25-year
50-year
100-year
2013 (FEMA)
Log. (Q vs Shear XS1)
Log. (Q vs Shear XS2)
Log. (Q vs Shear XS3)
Log. (Q vs Shear XS4)
Log. (Q vs Shear XS5)
1
10
100
1000 10000
Un
i
t
S
t
r
e
a
m
P
o
w
e
r
Discharge (cfs)
Discharge vs Unit Stream Power Q vs Stream Power XS1
Q vs Stream Power XS2
Q vs Stream Power XS3
Q vs Stream Power XS4
Q vs Stream Power XS5
Bankfull
5
10
25
50
100
2013 (FEMA)
Linear (Q vs Stream Power XS1)
Linear (Q vs Stream Power XS2)
Linear (Q vs Stream Power XS3)
Linear (Q vs Stream Power XS4)
Linear (Q vs Stream Power XS5)
Downstream Reach
Upstream Reach
Upstream Reach
Downstream Reach
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.56
Figure 44 Discharge vs. Width
Figure 45 Hydraulic Condition Comparison
0
20
40
60
80
100
120
140
160
180
200
0 2000 4000 6000 8000 10000 12000 14000
Wi
d
t
h
(
f
t
)
Discharge (cfs)
Discharge vs Width Q vs Width XS1
Q vs Width XS2
Q vs Width XS3
Q vs Width XS4
Q vs Width XS5
Bankfull
5
25
50
100
2013 (FEMA)
Expon. (Q vs Width XS1)
Expon. (Q vs Width XS2)
Expon. (Q vs Width XS3)
Expon. (Q vs Width XS4)
Expon. (Q vs Width XS5)
-20%
-10%
0%
10%
20%
30%
40%
16
3
2
22
3
7
40
7
8
50
5
8
71
0
1
80
8
4
10
1
2
2
13
0
0
0
Pe
r
c
e
n
t
C
h
a
n
g
e
f
r
o
m
1
&
2
t
o
3
,
4
,
&
5
Discharge (cfs)
Crossing 9 Hydraulic Condition Comparison
% Change in Area
% Change in Velocity
% Change in Shear Stress
Downstream
Reach
Upstream
Reach
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.57
Both Shear Stress and Unit Stream Power are hydraulic metrics that provide insight into the hydraulic force exerted
along the bed and bank. Figures 44 and 45 show a significant increase in both shear stress and unit stream power,
when comparing the upstream reach to the downstream reach, at various discharge values. Similarly, Figure 46
shows a reduction in channel width (increase in confinement) in the downstream direction, which supports the theory
that confinement and degradation potential are positively related.
Figures 46 through 51 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 9.
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
STAT
E
H
I
G
H
W
A
Y
1
4
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
LOC #24.29
24" AIR/VAC
N 171845.05
E 147847.01
E 148033.71
LOC #27.31
27" AIR/VAC
N 170827.06
E 148674.88
LOC #27.32
27" BLOWOFF
N 171067.98
E 148453.96
N 172185.09
E 148023.51
0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 8+56.50
0+0
0
1+0
0
2+0
0
3+0
0
4+0
0
5+0
0
C-10XS-
0
1
C-1
0XS
-
0
2
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
2
C-
0
9
XS
-
0
3
C-
0
9
XS
-
0
4
C-
0
9
XS
-
0
5
C-
0
9
XS
-
0
2
C-
0
9
XS
-
0
3
C-
0
9
XS
-
0
4
C-
0
9
XS
-
0
5
C-1
0XS
-
0
2
C-1
0XS-
0
1
CAC
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
STA
T
E
H
I
G
H
W
A
Y
1
4
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
CA
C
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
CA
C
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
CAC
H
E
L
A
P
O
U
D
R
E
R
I
V
E
R
CACH
E
L
A
P
O
U
D
R
E
R
I
V
E
R
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
v:
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A
M
N
27" STL LINE
24" RCP LINE
27" STL
XING #8
27" STL
XING #9
27" STL
XING #10
24" RCP
XING #6
C-09.0
CROSSING LOCATION #9
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
FLO
W
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
ROCK
WALL
PIPE
EXPOSURE
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
G
U
R
E
4
6
PRE-SED
BASIN
Profile View: 27" Steel Pipe Section 9
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5330
5335
5340
5345
5350
5355
5330
5335
5340
5345
5350
5355
365+00 366+00 367+00 368+00 369+00 369+50
27" STEEL PIPE
EXISTING GROUND
27" STEEL PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-09.1
CROSSING LOCATION #9
27" STL PIPELINE PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-09
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
47
Profile View: C9 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5345
5350
5355
5360
5345
5350
5355
5360
0+00 1+00 2+00
Profile View: C9 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5345
5350
5355
5360
5345
5350
5355
5360
0+00 1+00 2+002+10
WATER SURFACE
ELEV: 5350.77'
WATER SURFACE
ELEV: 5350.26'
BANKFULL
ELEV: 5352.3'
BANKFULL WIDTH = 152'
BANKFULL WIDTH = 120'
BANKFULL
ELEV: 5352.35'
C9 XS-01
C9 XS-02
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-09.2
CROSSING LOCATION #9
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-09
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
48
Profile View: C9 XS-03
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5340
5345
5350
5355
5340
5345
5350
5355
0+00 1+00 1+50
Profile View: C9 XS-04
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5340
5345
5350
5355
5340
5345
5350
5355
0+00 1+00 1+50
BANKFULL
ELEV: 5348.6'
WATER SURFACE
ELEV: 5345.90'
WATER SURFACE
ELEV: 5344.80'
27" STEEL PIPE
ELEV: 5345.34'
27" STEEL PIPE
ELEV: 5345.47'
BANKFULL WIDTH = 93'
BANKFULL WIDTH = 77'
C9 XS-03
C9 XS-04
BANKFULL
ELEV: 5347.26'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-09.3
CROSSING LOCATION #9
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-09
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
49
Profile View: C9 XS-05
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5340
5345
5350
5355
5360
5340
5345
5350
5355
5360
0+00 1+00 1+50
BANKFULL
ELEV: 5347.33'
WATER SURFACE
ELEV: 5344.82'
27" STEEL PIPE
ELEV: 5344.10'
BANKFULL WIDTH = 85'
C9 XS-05
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-09.4
CROSSING LOCATION #9
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-09
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
50
5330
5335
5340
5345
5350
5355
5360
5330
5335
5340
5345
5350
5355
5360
0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 8+75
RIVER BED (THALWEG) LONGITUDINAL PROFILE
27" STEEL PIPE
ELEV: 5342.19'
(CENTER)
BANKFULL PROFILE
XS
-
0
1
XS
-
0
2
XS
-
0
3
XS
-
0
4
XS
-
0
5
27" STEEL PIPE
(SUPERIMPOSED)WATER SURFACE PROFILE
1.5%
0.7%
1.5%
0.5%
EXISTING RIVER BED
(THALWEG) PROFILE
RIFFLE RIFFLEEXPECTED POOL GLIDE
27" STEEL PIPE
ELEV: 5345.47'
(LEFT BANK)
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-09.5
CROSSING LOCATION #9
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-09
FI
G
U
R
E
51
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.64
3.9.2 Risk Analysis
Crossing 9 represents the reach with the highest risk associated with channel/bed degradation in relation to the 27”
STL waterline crossing. The anthropogenic alterations of the channel banks and floodplains have created an area of
rapid constriction and increased confinement, which have resulted in exposure of approximately 75’ the waterline
along the left bank. The configuration of the overwide, upstream contributing reach results in flow convergence right
at the proximity of the waterline crossing, as shown in Figure 52, below. Additionally, the nearly vertical rock wall
along the right bank, provides minimal hydraulic resistance at all flow levels. Therefore, as the river stages up
through this reach, the lack of hydraulic resistance results in minimal dampening effects on localized velocities, as
compared to a naturalize bank. The effect of this phenomena is likely contributing to the excessive shear stress and
scour at the waterline crossing. Other contributing factors to the overall risk is the waterline elevation profile and the
skewed orientation of the waterline crossing in relation to the active channel. As shown above in Figure 46, the 27”
waterline crosses the active channel at an approximate 75° angle in the downstream direction. In the waterline profile
(Figure 47) sufficient depth of cover (3+ft) exists from the river right bank through the approximate channel thalweg,
but the overall slope of the waterline is such that as it approaches the left bank, depth of cover drops to less than 1 ft.
There is no evidence of significant lateral channel migration at this location, so the waterline was likely installed in this
manner.
Figure 52 Crossing 9 Flow Convergence Example
It is assumed based on field observation, the City of Fort Collins have implemented scour protection measures in the
form of riprap armoring. However, the occurrence of less frequent, higher magnitude discharge events has resulted in
shear stresses that exceed the critical threshold value of the riprap armoring. Table 3 below shows an example of
approximate riprap sizing when considering the calculated hydraulic values for the 25, 50 and 100-year events.
However, it should be noted that the riprap sizes below are based off the average channel shear and velocity values,
and localized forces are likely much higher. Development of a 2D model would be recommended to better inform
design riprap sizing.
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.65
Table 3 - Estimated Riprap Sizing Requirements
Return
Interval
Discharge
(CFS)
Velocity
(ft/s)
Shear
Stress
(lbs./ft2)
Riprap
D50 (In)
Riprap
D100 (In)
25 7,090 9.46 4.28 15.7 31.4
50 8,038 9.91 4.58 16.6 33.2
100 10,070 10.74 5.17 18.5 37
3.9.3 Evaluation of Alternatives
3.9.3.1 Alternative 1 – Leave As-Is and Monitor
The first alternative is to leave the existing conditions as-is and monitor the bank erosion on an annual basis (after
spring runoff), as well as after any flow event greater than the bankfull discharge. This approach is most cost-effective
in the short term but has an increased risk of damage to the pipe in a large flow event. This alternative is not
advisable as a sustainable long-term solution.
3.9.3.2 Alternative 2 – Protect in Place (A) Riprap Armoring
Alternative 2 is to leave the pipe in place and armor the pipe exposure with riprap. This appears to have been the
preferred alternative in the past, as suggested by the existing riprap in the area which has been eroded away. This
alternative also includes the installation of boulder vanes to direct high velocities away from the pipeline. Patching the
problem is relatively low impact and cost effective in the short-term. The longevity of this solution is uncertain, but
statistically it will last about 10 years. This estimate is based on hydraulic analysis which shows 30” diameter riprap
being moved during a 10-year flow event. As evidenced by the eroded riprap, this alternative will require long term
monitoring and maintenance.
The anthropogenic impacts within the floodplain are causing the channel to adjust in the form of bank erosion.
Without addressing the cause of the bank erosion, continued channel adjustment can be expected. Further channel
adjustment has the potential to expose the 27” STL in a different location. When these adjustments may occur can’t
be accurately predicted, but flow events as low as the average peak runoff have the potential to cause incremental
channel adjustments.
3.9.3.3 Alternative 3 – Protect in Place (B) Articulated Concrete Mat Protection
Alternative 3 is to leave the pipe in place and armor the pipe with an articulated concrete mat and install boulder
vanes to direct high velocities away from the pipe. This alternative provides a robust solution for the integrity of the
pipe in the current exposure location but does not address risks associated with further channel adjustment. The
anthropogenic impacts within the floodplain are causing the channel to adjust in the form of bank erosion. As stated in
Alternative 2, without addressing the cause of the bank erosion, continued channel adjustment can be expected.
Further channel adjustment has the potential to expose the 27” STL in a different location. When these adjustments
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.66
may occur can’t be accurately predicted, but flow events as low as the average peak runoff have the potential to
cause incremental channel adjustments.
3.9.3.4 Alternative 4 – Holistic Geomorphic Approach with Waterline Lowering
Alternative 4 is the adjustment of the channel and floodplain geometry to eliminate bank erosion at higher flow
events, paired with the waterline lowering described in Alternative 5. Primarily, the channel and floodplain
improvements would occur in the “Upstream Reach” area and consist of implementing a bankfull bench with Wood
Toe and soil lifts (refer to Figure ES-2). This modification of the overwide “Upstream Reach” will reduce the rapid
constriction at the waterline crossing and improve flow resistance and energy dissipation along the Woody Toe. This
solution addresses the cause of the bank erosion, instead of patching the symptoms. Improving the geometry of the
channel and associated floodplain at the 27” STL crossing offers a sustainable long-term alternative to the
reoccurring pipe exposure issue. This solution would be designed to the 50-year flow event. Which means, on
average, the longevity of this project is 50 years. This is a relatively high impact and costly solution in the short term.
However, the reduction in long term maintenance and re-work will likely offset some of the initial investment.
3.9.3.5 Alternative 5 – Waterline Lowering
Alternative 5 lowers the waterline in the vicinity of the 27-inch STL crossing to achieve a depth of cover of at least 4 to
6 ft. This is a high impact, and high cost solution, but does ensure the longevity of the solution. Without addressing
the cause of the bank erosion, continued bank erosion can be expected. By providing an adequate depth of cover,
the lateral bank erosion will not expose the pipe in the future.
3.9.3.6 Alternative 6 –Sliplining
Sliplining the 27-inch STL pipe section from station 370+00 to 366+00 at Crossing 9 can be accomplished with low
impact to the channel since the installation process occurs from open cuts to access the inside of the pipe from each
side of the river. It is effective for preventing leaks but adds very little to the structural integrity of the pipe. Therefore,
as a long-term option, Alternative 6 does not protect the pipe in Crossing 9 from vertical channel erosion, nor does it
prevent lateral bank erosion.
Plan sheets were prepared showing Crossing 9 alternatives in Figures 53 through 55, as follows:
LOC #24.29
24" AIR/VAC
N 171845.05
E 147847.01
LOC #27.32
27" BLOWOFF
N 171067.98
E 148453.96
0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00
3+0
0
4+0
0
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
2
C-
0
9
XS
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3
C-
0
9
XS
-
0
4
C-
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9
XS
-
0
5
C-
0
9
XS
-
0
2
C-
0
9
XS
-
0
3
C-
0
9
XS
-
0
4
C-
0
9
XS
-
0
5
C-1
0XS
-
0
2
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-09-ALTERNATIVES
v:
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2
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P
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27" STL LINE
24" RCP LINE
27" STL
XING #8
27" STL
XING #9
27" STL
XING #10
24" RCP
XING #6
C-09.6
CROSSING LOCATION #9
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
ROCK
WALL
PIPE
EXPOSURE
BOULDER
VANES
ARMOR AND BURY
EXPOSED PIPE WITH
RIPRAP
ALTERNATIVE 2
FI
G
U
R
E
53
LOC #24.29
24" AIR/VAC
N 171845.05
E 147847.01
LOC #27.32
27" BLOWOFF
N 171067.98
E 148453.96
0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00
3+0
0
4+0
0
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
1
C-
0
9
XS
-
0
2
C-
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C-
0
9
XS
-
0
4
C-
0
9
XS
-
0
5
C-1
0XS
-
0
2
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-09-ALTERNATIVES
v:
\
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2
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2
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P
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27" STL LINE
24" RCP LINE
27" STL
XING #8
27" STL
XING #9
27" STL
XING #10
24" RCP
XING #6
C-09.7
CROSSING LOCATION #9
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
ROCK
WALL
PIPE
EXPOSURE
BOULDER
VANES
INSTALL
ARTICULATED
CONCRETE MAT
ALTERNATIVE 3
FI
G
U
R
E
54
LOC #24.29
24" AIR/VAC
N 171845.05
E 147847.01
LOC #27.32
27" BLOWOFF
N 171067.98
E 148453.96
0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00
3+0
0
4+0
0
C-
0
9
XS
-
0
1
C-
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9
XS
-
0
1
C-
0
9
XS
-
0
2
C-
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9
XS
-
0
4
C-
0
9
XS
-
0
5
C-1
0XS
-
0
2
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-09-ALTERNATIVES
v:
\
2
0
5
3
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2
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27" STL LINE
24" RCP LINE
27" STL
XING #8
27" STL
XING #9
27" STL
XING #10
24" RCP
XING #6
C-09.8
CROSSING LOCATION #9
27" STL PIPELINE
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLOW
LONGITUDINAL
PROFILE BASE
KEY MAP
1" = 1000'
ROCK
WALL
PIPE
EXPOSURE
HABITAT
FEATURES
BANKFULL
BENCH
SOIL LIFTS
WOOD TOE
BOULDER
VANES
ARMOR AND BURY
EXPOSED PIPE
WITH RIPRAP
EXCAVATE
POOL
ALTERNATIVE 4
FI
G
U
R
E
55
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
tpm v:\2053\active\205305271\report\final report revisions aug 2018\final rpt_poudre_pipeline_crossing_erosion_study_2018-08-30.docx 3.70
A MCDA for Crossing 9 shows the weighted totals in Table 4. As shown, Alternative 4 combined with Alternative 5 is
the most desirable according to the rankings.
Table 4 - Crossing 9 Alternatives Decision Matrix
Co
m
p
a
r
i
s
o
n
C
r
i
t
e
r
i
a
Im
p
o
r
t
a
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F
a
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t
o
r
1- Do
N
o
t
h
ing
2
- Pr
o
t
e
c
t
i
n
P
l
a
c
e
(
A
)
Ri
p
r
a
p
A
r
m
o
r
i
n
g
3
- Pr
o
t
e
c
t
i
n
P
l
a
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e
(
B
)
Ar
t
i
c
u
l
a
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e
d
C
o
n
c
r
e
t
e
M
a
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c
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i
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4
- Ch
a
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G
e
o
m
e
t
r
y
Ad
j
u
s
t
m
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t
a
n
d
H
a
b
i
t
a
t
Im
p
r
o
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e
n
t
5
- Wa
t
e
r
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i
n
e
L
o
w
e
r
i
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g
6
- Co
m
b
i
n
a
t
i
o
n
o
f
Op
t
i
o
n
s
4
a
n
d
5
7
- Sl
i
p
l
i
n
i
n
g
Permitting
Temporary
Changes to River
Long Term Pipeline
Habitat
62
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
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3.10 CROSSING 10
Crossing 10 includes the 6th crossing of the 24” RCP and the 10th crossing of the 27” STL. The 24” RCP crosses the
channel at a 50°angle and the 27” STL crosses the channel at a 45° angle. The upstream end of the reach is
confined by bedrock on river left until station 2+50, with moderate floodplain access on river right. At station 2+50 the
valley becomes less confined with good floodplain access on both sides of the river. A mid-channel bar has formed
from station 3+50 to station 6+00, splitting the low flow into two separate channels. Downstream of station 6+00
floodplain access is lost and the channel becomes confined by an embankment on river right.
3.10.1 Synopsis of Field Data
The geomorphic survey consisted of 2 cross-sections, and a longitudinal profile. The locations and extent of the
cross-section and longitudinal profile were selected to compare the changes in hydraulic conditions throughout the
reach. Cross-section 1 (XS-01) was taken at the head of a riffle section with a bankfull width measuring 128 ft. Cross-
section 2 (XS-02) was taken in the middle of the same riffle section with a bankfull width measuring 151 ft. The
bankfull slope measured from the longitudinal profile ranges between 0.5% and 0.6%.
The survey of the 24” RCP shows a ground cover of 4 to 6 ft across the channel. The 27” STL survey showed a
ground cover of 5.5 to 6 ft across the channel. The longitudinal profile measured a thalweg elevation of 5.5 ft above
the 24” RCP in the middle of a riffle section and 5 ft above the 27” STL in the middle of the same riffle section.
Figures 56 through 59 provide the Plan, Pipe Profile, Cross Sections (with photos) and the Longitudinal Profile for
Crossing 9.
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LOC #24.29
24" AIR/VAC
N 171845.05
E 147847.01
LOC #24.30
24" ILV
N 172177.37
E 148033.71
LOC #27.33
27" AIR/VAC
N 171827.67
E 147796.20
LOC #27.34
27" BLOWOFF
N 171918.10
E 147843.48
LOC #27.35
27" ILV
N 172185.09
E 148023.51
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Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1.Geomorphic survey conducted on
April 11-12th 2018.
2.Estimated Discharge on date of
survey ~40 CFS.
File Name: 05271_PV-C-01-C-10
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KEY MAP
1" = 1000'
N
27" STL LINE
24" RCP LINE
27" STL
XING #8
27" STL
XING #9
27" STL
XING #10
24" RCP
XING #6
PRE-SED
BASIN
DIVERSION
STRUCTURE
C-10.0
CROSSING LOCATION #10
24" RCP & 27" STL PIPELINES
0
As Indicated
MAC MAC CDN
NOTE:
RED LINES SHOWN ARE 27" STL RIVER CROSSINGS.
YELLOW LINES SHOWN ARE 24" RCP RIVER CROSSINGS.
WATERLINE LEGEND
AIR/VAC (AIR RELEASE VALVE)
BFV (BUTTERFLY VALVE)
BLOWOFF VALVE/ ILV (INLINE VALVE)
CPTS (CATHODIC PROTECTION TEST STATION)
WATERLINE MARKER
N
FLO
W
FL
O
W
PRE-SED BASIN AT
GATEWAY PARK
LONGITUDINAL
PROFILE BASE
NEWLY CONSTRUCTED
BOAT LAUNCH
ROCK WALL
FACET TYPE LEGEND
GLIDE
RIFFLE
POOL
RUN
FI
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5
6
Profile View: 24_ Reinforced Concrete Pipe Section 6
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5350
5355
5360
5365
5350
5355
5360
5365
375+00 376+00 377+00 378+00
Profile View: 27" Steel Pipe Section 10
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5345
5350
5355
5360
5365
5345
5350
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377+50 378+00 379+00 380+00 380+50
27" STEEL PIPE
EXISTING GROUND
24" RCP
EXISTING GROUND
27" STEEL PIPE SECTION
24" REINFORCED CONCRETE PIPE SECTION
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-10.1
CROSSING LOCATION #10
27" STL & 24" RCP PIPELINE PROFILES
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-10
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
57
Profile View: C10 XS-01
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5355
5360
5365
5370
5355
5360
5365
5370
-0+20 0+00 1+00 2+00
Profile View: C10 XS-02
Horizontal Scale: 1" = 50
Vertical Scale: 1" = 10'
Vertical Exaggeration: 5:1
5348
5350
5355
5360
5348
5350
5355
5360
-0+20 0+00 1+00 2+00
WATER SURFACE
ELEV: 5357.53'
BANKFULL WIDTH = 128'
BANKFULL
ELEV: 5359.76'
C10 XS-01
WATER SURFACE
ELEV: 5356.32'
BANKFULL WIDTH = 151'
BANKFULL
ELEV: 5358.40'
C10 XS-02
27" STEEL PIPE
ELEV: 5350.59'
24" RCP
ELEV: 5351.52'
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-10.2
CROSSING LOCATION #10
GEOMORPHIC CROSS SECTIONS
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-10
Horiz
Scale
Vert
Scale
0'50'
0'10'
FI
G
U
R
E
58
5340
5345
5350
5355
5360
5365
5340
5345
5350
5355
5360
5365
-0+50 0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 7+50
RIVER BED (THALWEG) LONGITUDINAL PROFILE
XS
-
0
1
XS
-
0
2
27" STEEL PIPE
ELEV: 5350.07'
BANKFULL PROFILE
EXISTING RIVER BED
(THALWEG) PROFILE
WATER SURFACE PROFILE
24" RCP
ELEV: 5349.46'
0.5%
0.6%
RUNRIFFLE POOL
Project No.Scale
Revision Drawing No.
Title
Client/Project
Client/Project Logo
Permit/Seal
Issued
Revision
Notes
Consultant
Copyright Reserved
By Appd YYYY.MM.DD
By Appd YYYY.MM.DD
Dsgn.Chkd.YYYY.MM.DDDwn.
The Contractor shall verify and be responsible for all dimensions. DO NOT scale the d
- any errors or omissions shall be reported to Stantec without delay.
The Copyrights to all designs and drawings are the property of Stantec. Reproduction
use for any purpose other than that authorized by Stantec is forbidden.
PRELIMINARY
NOT FOR
CONSTRUCTION
Not for permits, pricing or other official
purposes. This document has not been
completed or checked and is for
general information or comment only.
ORIGINAL SHEET - ANSI D
Tel:
www.stantec.com
Stantec Consulting Services Inc.
3325 South Timberline Road Suite 150
Fort Collins CO 80525-2903
(970) 482-5922
A
B
C
D
1 2 3 4 5
City of Fort Collins
Poudre Pipeline Erosion Control
for Existing 24" RCP & 27" STL
Fort Collins, CO
205305271
2018.04.11
1. Geomorphic survey conducted on
April 11-12th 2018.
2. Estimated Discharge on date of
survey ~40 CFS.
C-10.3
CROSSING LOCATION #10
GEOMORPHIC LONGITUDINAL
PROFILE
0
As Indicated
MAC MAC CDNFile Name: 05271_SV-C-10
FI
G
U
R
E
59
POUDRE PIPELINE CROSSING EROSION STUDY
Analysis of Pipeline Crossings
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3.10.2 Risk Analysis
Crossing 10 includes crossings of both the 24” RCP and the 27” STL. Both pipelines cross through the middle of a
riffle section just upstream of a mid-channel bar. The presence of a mid-channel bar indicates aggradation occurring
from a lack of sediment transport competency that typically results in lateral bank erosion. However, no substantial
bank erosion was observed within the vicinity of the pipe crossings. Both the 27” STL and the 24” RCP have sufficient
depth of cover, 4 to 6 ft, and 5 to 6 ft respectively. As such, there is a low risk of exposure due to vertical degradation.
POUDRE PIPELINE CROSSING EROSION STUDY
Planning Level Program Costs and Environmental Permitting
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4.0 PLANNING LEVEL PROGRAM COSTS AND
ENVIRONMENTAL PERMITTING
4.1.1 Contractor’s Estimate of Construction Costs
As part of the projects planning efforts, the City engaged the services of Hydro Construction for the primary purpose
of sharing their expertise gained from multiple previous repairs on the existing pipelines and for the expertise in
providing guidance related to constriction within, and associated costs of working in the Poudre. Following
completion of defining the alternatives to be considered, Stantec provided schematic layouts of the proposed Work at
Crossings #7 and #9.
In turn, Hydro completed planning level construction costs for the various alternatives – as shown in Tables 5 and 6
below.
Table 5 – Construction Cost Estimates for Crossing 7 Alternatives
Alternative / Description Quantity Unit Total Cost
Alternative 1 -Do Nothing
Alternative 2 - Protect in Place (A) Riprap Armoring
Type VH Void Filled Riprap 170 cu. yd
Total Alternative Conceptual Estimate $ 62,000.00
Alternative 3 - Protect in Place (B) Articulated Concrete Mat Protection Articulated Mat
(40' wide x 100' long) 400 sq. ft
Total Alternative Conceptual Estimate $ 83,000.00
Alternative 4 - Holistic Geomorphic Approach with Riprap Protection
Type VH Void Filled Riprap 0 cu. yd
Wood Toe 0 linear ft
3 ft Diameter Boulders 0 ea. Bankfull bench fill (borrow
fill on-site from excavating
Alternative 5 - Waterline Lowering
Alternative 6 - Sliplining
POUDRE PIPELINE CROSSING EROSION STUDY
Planning Level Program Costs and Environmental Permitting
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Table 6 – Construction Cost Estimates for Crossing 9 Alternatives
Alternative / Description Quantity Unit Total Cost
Alternative 1 -Do Nothing
Alternative 2 - Protect in Place (A) Riprap Armoring
Type VH Void Filled Riprap 130 cu. yd
3 ft Diameter Boulders 110 ea.
Total Alternative Conceptual Estimate $ 88,000.00
Alternative 3 - Protect in Place (B) Articulated Concrete Mat Protection Articulated Mat
(40' wide x 100' long) 400 sq. ft
3 ft Diameter Boulders 110 ea.
Total Alternative Conceptual Estimate $ 112,000.00
Alternative 4 - Holistic Geomorphic Approach with Riprap Protection
Type VH Void Filled Riprap 130 cu. yd
Wood Toe 315 linear ft
3 ft Diameter Boulders 150 ea. Bankfull bench fill (borrow
fill on-site from excavating
Alternative 5 - Waterline Lowering
Alternative 6 - Sliplining
4.1.2 Engineer’s Opinion of Probable Project Costs
The Engineer’s Opinion of Probable Project Cost (EEOPPC) to construct each alternative was developed to an
accuracy consistent with a planning level study used for concept screening. The Cost Estimate Classification System
defines this level as Class 5 with an expected accuracy in the low range of -20% to -50%, and in the high range
+30% to +100%.
The cost estimates for the preferred alternatives for Crossing 7 and Crossing 9 are presented in Tables 7 and 8.
POUDRE PIPELINE CROSSING EROSION STUDY
Planning Level Program Costs and Environmental Permitting
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Table 7 - EEOPPC for Crossing 7, Alternative 4 “Waterline Lowering”
ITEM QUAN UNIT UNIT COST COST
1 Lower 24" RCP (from station 333+50 to 335+00) 150 LS $335,000 $335,000
Construction subtotal $335,000
Construction Contingency 20% LS $67,000 $ 67,000
Construction Total $402,000
Engineering Design 20% $80,400 $80,400
Engineering Permitting 1 L.S. $ 25,000 $ 25,000
City PM 8 Weeks $ 6,000 $ 48,000
Crossing 7 Project Total $556,000
Table 8 - EEOPPC for Crossing 9, Alternative 4 & 5 “Channel Habitat Improvements and
Waterline Lowering”
1. Holistic Geomorphic Approach with Riprap
Protection
1 LS $262,000 $262,000
2. Lower 27" STL (from station 370+00 to
366+70)
330 LS $540,000 $540,000
Construction subtotal $802,000
Construction Contingency 20% LS $ 160,400
Construction Total $962,500
Engineering Design 20% $192,500 $192,500
Engineering Permitting 1 L.S. $ 50,000 $ 50,000
City PM 12 Weeks $ 6,000 $ 72,000
Crossing 9 Project Total $1,300,000
4.1.3 Environmental Permitting
The Cache la Poudre River is a jurisdictional waterbody subject to regulation under Sections 404 and 401 of the
Clean Water Act, the Rivers and Harbors Act, and other associated environmental laws. Work performed below the
Ordinary High Water Mark (OHWM) of jurisdictional waters requires permitting activities that are administered by the
U.S. Army Corps of Engineers (USACE). Preliminary consultation with the Corps will determine the type of permit(s)
required for the projects described here. Crossing 7 and Crossing 9 may fall within the authority of the USACE
Nationwide Permit (NWP) program. A nationwide permit is a general permit that authorizes activities that have only
minimal individual and cumulative adverse environmental effects. There are 54 different types of NWPs, and the two
permits that may apply to this project are #12 (Utility Line Activities) and #27 (Aquatic Habitat Restoration,
Establishment, and Enhancement Activities). The permits entail, at minimum, a pre-construction notification, site walk
with the USACE, and concurrence from the USACE prior to finalizing design. The type and number of permits
required for any project, as well as the enforcement of any applicable regional conditions, is under of the sole
POUDRE PIPELINE CROSSING EROSION STUDY
Planning Level Program Costs and Environmental Permitting
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discretion of the USACE and cooperating federal and state regulatory agencies. Permitting costs associated with the
EEOPPC presented here assume that NWPs are applicable, appropriate, and would be granted for these projects.
The USACE serves as the lead federal agency for Clean Water Act §404 permits. As such they consult directly with
other regulatory agencies in assessing project purpose and need and permitting requirements under applicable laws
(e.g., Endangered Species Act, National Historic Preservation Act). As part of the process, the Corps will
communicate directly with the US Environmental protection Agency (EPA), US Fish and Wildlife Service (USFWS),
State Historic Preservation Officer (SHPO), and Colorado Parks and Wildlife (CPW). In addition, the Corps will work
with the Colorado Department of Public Health and Environment (CDPHE) Water Quality Control Division (WQCD)
whom will review and issue Water Quality Certifications under Section 401 of the federal Clean Water Act. Other
state and local permits may be required in association with the projects described here, including righ-of-way or
special use permits from the Coloroado Department of Transportation (CDOT), permits related to the Wild and Scenic
Rivers Act by the U.S. Forect Service (USFWS), and floodplain permits administered by Larmier County. Site-specific
environmental and cultural resources surveys may be required for these projects to obtain permits necessary for
implementation.
The preferred alternative for Crossing 7 is the “Waterline Lowering”, which may meet the requirements for the
Nationwide Permit 12 – Utility Line Activities. This is a straightforward and commonly used permit for projects of
similar nature.
The preferred alternative for Crossing 9 is the “Holistic Approach with Waterline Lowering.” This alternative may
require both a Nationwide 12 and a Nationwide 27. This approach will also likely require a Larimer County Floodplain
Permit to document no adverse effects (i.e., a “no-rise” certification) on the regulatory FEMA floodplain.
POUDRE PIPELINE CROSSING EROSION STUDY
Conclusions and Recommendations
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5.0 CONCLUSIONS AND RECOMMENDATIONS
The 24” diameter RCP and 27” diameter STL pipelines are a critical component in providing raw water for the City of
Fort Collins. Successful operation of the water utility is reliant on the integrity of these pipes, thus long-term
protection of this infrastructure is a high priority for the City.
During the Fall 2017’s semi-annual inspection, an exposure of the 27” STL pipe was observed near Gateway Park.
This location has experienced exposure issues in the past, which have been remediated with armoring of angular
stone (i.e. riprap). However, this approach is not a permanent solution given the pipe has become exposed again.
Stantec’s Stream Restoration Group conducted a geomorphic assessment at the ten 27” STL pipeline crossings and
the six 24” RCP pipeline crossings of the Poudre River, to evaluate the current and future exposure risk from
geomorphic channel adjustment. The team identified 3 crossings with potential risks, including crossings 2, 7, and 9,
based on the observed and measured geomorphic conditions. Table 9 below shows the estimated risk factor for each
of the crossing locations. The recommendations for the 3 crossings with some degree of exposure risk are
summarized in greater detail below.
Table 9 - Summary of Geomorphic Risk by Crossing Location
Crossing # Low Risk Medium Risk High Risk
1
5.1 CROSSING 2 RECOMMENDATIONS
Crossing 2 is located south of State Highway 14 and just downstream of the canyon mouth. At this crossing location,
only the 27” STL crosses the Poudre River in the middle of a stable riffle. However, approximately 380’ upstream of
the pipeline crossing, moderate to high bank erosion was observed along the left outside meander bend. While this
bank erosion does not pose an immediate threat of exposure to either the 24” RCP or 27” STL pipeline, continued
erosion could lead to the formation of a chute cutoff channel. As such, the crossing is considered a moderate risk,
and we recommend this area be monitored annually, post runoff, or after a major storm event.
POUDRE PIPELINE CROSSING EROSION STUDY
Conclusions and Recommendations
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5.2 CROSSING 7 RECOMMENDATIONS
Crossing 7 includes the 5th crossing of the 24” RCP and the 7th crossing of the 27” STL. During the survey effort,
the 24” RCP was unable to be located. Stantec utilized survey data from a September 2017 study (Poudre Pipeline
Rehabilitation for the 24” RCP. Stantec 2017), to compare pipe elevation data with the geomorphic survey data.
Projecting the pipe elevation from the 2017 survey onto the surveyed pipe cross-section data showed marginal
ground cover with a potential exposure. At the time of the project survey, the potential exposure could have been
missed by the field crews since the crossing occurs in a pool (depth at time of survey 3+ feet). Due to the uncertainty
of the 24” RCP crossing in both location and elevation, this reach should be re-evaluated in Fall 2018 to check for
potential pipe exposure.
However, even if the pipe is found to not be exposed, based on the location of the crossing within a pool and the
likelihood of marginal cover over the pipe, we recommend implementation of Alternative 4 – Waterline Lowering.
Lowering of the waterline is the only alternative that will provide long term protection from future geomorphic changes
to the river.
5.3 CROSSING 9 RECOMMENDATIONS
Crossing 9 is the reach with the highest risk and only location of a known exposure of the 27” STL pipe. This reach
has been heavily influenced by the State Highway 14 embankment and old access road to Gateway Park. The
anthropogenic alterations have created an area of rapid constriction immediately upstream and throughout the
pipeline crossing location. When a channel/floodplain is subject to a rapid change (expansion/contraction), the
hydraulic forces are typically exacerbated, which leads to erosion/degradation. Such is the case at this location
where approximately 75’ of pipe has become exposed. Based on the amount of angular boulder material on the left
bank of the river near the area of exposure, it appears that this has been an ongoing problem and that effforts to
cover the pipe with large rock material have repeatedy failed. We recommend the City evaluate implementing Design
Alternative 4 “Holistic Geomorphic Approach with Alternative 5 “Waterline Lowering.” This combination of alternatives
should address the root cause of the channel bed and bank erosion by eliminating the rapid constriction upstream of
the crossing and lower the pipe to provide adequate depth of cover. Waterline lowering itself is not a permanent
solution for the exposure at crossing 9, as it does not correct the contraction/expansion scour that is causing the pipe
to become exposed. The combination of waterline lowering and correction of upstream channel/floodplain geometry
is a complete, long-term solution to the pieline exposure issues at this crossing location. This is a relatively high-
impact and costly solution in the short-term. However, the reduction in long-term maintenance and re-work will likely
offset some of the initial investment.
POUDRE PIPELINE CROSSING EROSION STUDY
References
6.1
6.0 REFERENCES
Wolman, M. G. 1954. A Method of Sampling Coarse River-bed Material. Transactions, American Geophysical Union
35(6): 951- 956.
Schumm, S. A. 1977. The Fluvial System (2003 Reprint). The Blackburn Press. 338 p.
Knighton, A.D., 1998. Fluvial Forms and Processes: A New Perspective. London: Arnold. 383 p.
Lane, E. W. 1955. The importance of fluvial morphology in hydraulic engineering. Proceedings of the American
Society of Civil Engineers 81: 17.
Leopold 1994. A View of the River. Harvard University Press. 298 p.
Leopold, L. B., Wolman, M. G. and J. P. Miller. 1964. Fluvial Processes in Geomorphology. New York: Dover
Publications, Inc. 522 p.
Rosgen, D. 1996. Applied River Morphology. Pagosa Springs: Wildland Hydrology