HomeMy WebLinkAboutFORT COLLINS HOTEL (DOWNTOWN HOTEL) - PDP - PDP150008 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTJune 24, 2015
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT FOR
FORT COLLINS HOTEL
Fort Collins, Colorado
Prepared for:
Bohemian Companies
&
Mcwhinney
Prepared by:
200 South College Avenue, Suite 10
Fort Collins, Colorado 80524
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 947-002
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
June 24, 2015
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
FORT COLLINS HOTEL
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report
for your review. This report accompanies the Project Development Plan submittal for the
proposed Fort Collins Hotel.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed project. We
understand that review by the City is to assure general compliance with standardized criteria
contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Aaron Cvar, PE
Project Engineer
Fort Collins Hotel
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 2
C. Floodplain.......................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description .................................................................................................................... 4
B. Sub-Basin Description ....................................................................................................................... 5
III. DRAINAGE DESIGN CRITERIA ................................................................................... 5
A. Regulations........................................................................................................................................ 5
B. Four Step Process .............................................................................................................................. 5
C. Development Criteria Reference and Constraints ............................................................................ 6
D. Hydrological Criteria ......................................................................................................................... 6
E. Hydraulic Criteria .............................................................................................................................. 6
F. Modifications of Criteria ................................................................................................................... 6
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept ............................................................................................................................... 7
B. Specific Details .................................................................................................................................. 7
V. CONCLUSIONS ........................................................................................................ 8
A. Compliance with Standards .............................................................................................................. 8
B. Drainage Concept .............................................................................................................................. 9
APPENDICES:
APPENDIX A.1 - Historic Conditions Hydrologic Computations
APPENDIX A.2 - Developed Conditions Hydrologic Computations
APPENDIX B.1 - Erosion Control Report
APPENDIX C.1 - Base Flood Elevation Analysis
Fort Collins Hotel
Preliminary Drainage Report
LIST OF FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 4
MAP POCKET:
Proposed Drainage Exhibit
Fort Collins Hotel
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
Vicinity Map
1. The project site is located in the southwest quarter of Section 12, Township 7 North,
Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado.
2. The project site is located just north of the intersection of Walnut Street and Mountain
Avenue.
3. The project site lies within the Old Town Basin. A small portion of the site drains to
the storm sewer system in Walnut Street, which is conveyed south to Oak Street and
then the Udall water quality treatment area. The majority of the site drains into the
existing storm sewer system in Chestnut Street, which conveys flows into the Cache
La Poudre River. The Downtown River District Final Design Report, by Ayres 2012
(Ref. 5), shows the majority of the site conveyed via sheet flow into the Chestnut
Street storm system (Basin 106). As long as existing site runoff rates are not
increased, detention is not required for the site. However, the site still must provide
meet current City Low Impact Design (LID) requirements. Several water quality
treatment methods are proposed for the site, and are described in further detail
Fort Collins Hotel
Preliminary Drainage Report 2
below.
4. As this is an infill site, the area surrounding the site is fully developed.
5. No offsite flows enter the site from the south, west, or east. A small area to the
northwest of the site sheet flows onto the site. This area has been broken into two
offsite basins, which is described further in Section IV.A, below.
B. Description of Property
1. The development area is roughly 2.4 net acres.
Figure 1 – Aerial Photograph
2. The subject property is currently composed of existing buildings, and landscaped
areas. Existing ground slopes are mild to moderate (i.e., 1 - 6±%) through the
interior of the property. General topography slopes from northwest to southeast.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey website:
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx,
the site consists of Paoli fine sandy loam (Hydrologic Soil Group A), and Santana
loam (Hydrologic Soil Group B).
4. The proposed project site plan is composed of the development of a hotel and parking
lot. Associated site work, water, and sewer lines will be constructed with the
development. Current City Low Impact Design (LID) requirements will be
implemented with the project, and will consist of several LID features which are
discussed in Section IV, below.
Fort Collins Hotel
Preliminary Drainage Report 3
Figure 2– Proposed Site Plan
5. There are no known irrigation laterals crossing the site.
6. The proposed land use is a downtown hotel development.
C. Floodplain
1. The project site is not encroached by any City or FEMA designated 100-year
floodplain. However, the City of Fort Collins Stormwater Utility has identified areas
adjacent to the site as a 100-year flood risk zone. The adjacent Walnut Street and
Chestnut Street have been studied for flood risk, and base flood elevation in these
adjacent streets has been analyzed. Appendix C provides a summary of the analysis
performed to determine base (100-year) flood elevation in adjacent street Right of
Way, which is intended to be utilized for the design of finished floor elevation or flood
proofing at Final design.
Fort Collins Hotel
Preliminary Drainage Report 4
Figure 3 –Area Floodplain Mapping
2. A minimum of 12-inches of freeboard will be provided at Final design from base
(100-year) flood elevation in adjacent Right of Way. This freeboard level will be
applied to either the design of finished floor elevations, or the minimum level of flood
proofing measures.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
3. The project site lies within the Old Town Basin. Generally, detention requirements for
this basin are to detain the difference between the 100-year developed inflow rate
and the historic 2-year release rate. However, a portion of the site drains to the storm
sewer system in Walnut Street, which is conveyed south to Oak Street and then the
Udall water quality treatment area. The remainder of the site drains into the existing
storm sewer system in Chestnut Street, which conveys flows into the Cache La Poudre
River. As long as existing site runoff rates are not increased, detention is not required
for the site. The site still must meet current City Low Impact Design (LID)
requirements. Several LID treatment methods are proposed for the site, and are
described in further detail below.
Fort Collins Hotel
Preliminary Drainage Report 5
B. Sub-Basin Description
1. The subject property historically drains overland from northwest to southeast. Runoff
from the majority of the site has historically been collected in existing inlets located
within Walnut Street and Chestnut Street.
2. A more detailed description of the project drainage patterns is provided below.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the proposed
project.
B. Four Step Process
The overall stormwater management strategy employed with the proposed project utilizes
the “Four Step Process” to minimize adverse impacts of urbanization on receiving waters.
The following is a description of how the proposed development has incorporated each
step.
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low Impact Development (LID) strategies including:
Conserving existing amenities in the site including the existing vegetated areas.
Providing vegetated open areas throughout the site to reduce the overall impervious
area and to minimize directly connected impervious areas (MDCIA).
Routing flows, to the extent feasible, through vegetated swales to increase time of
concentration, promote infiltration and provide initial water quality.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, urban
development of this intensity will still generate stormwater runoff that will require
additional BMPs and water quality. The majority of stormwater runoff from the site will
ultimately be intercepted and treated using extended detention methods prior to exiting the
site.
Step 3 – Stabilize Drainageways
There are no major drainageways within the subject property. While this step may not
seem applicable to proposed development, the project indirectly helps achieve stabilized
drainageways nonetheless. By providing water quality treatment, where none previously
existed, sediment with erosion potential is removed from downstream drainageway
systems. Furthermore, this project will pay one-time stormwater development fees, as
well as ongoing monthly stormwater utility fees, both of which help achieve City-wide
drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Fort Collins Hotel
Preliminary Drainage Report 6
The proposed development will provide LID features which enhance water quality;
thus, eliminating sources of potential pollution previously left exposed to weathering
and runoff processes.
C. Development Criteria Reference and Constraints
The subject property is surrounded by currently developed properties. Thus, several
constraints have been identified during the course of this analysis that will impact the
proposed drainage system including:
Existing elevations along the property lines will generally be maintained.
As previously mentioned, overall drainage patterns of the existing site will be
maintained.
Elevations of existing downstream facilities that the subject property will release to
will be maintained.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with the proposed development. Tabulated data contained in Table RA-7
has been utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. Three separate design storms have been utilized to address distinct drainage
scenarios. A fourth design storm has also been computed for comparison purposes.
The first design storm considered is the 80th percentile rain event, which has been
employed to design the project’s water quality features. The second event analyzed is
the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The third
event considered is the “Major Storm,” which has a 100-year recurrence interval.
The fourth storm computed, for comparison purposes only, is the 10-year event.
4. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property maintains historic drainage patterns.
2. All drainage facilities proposed with the project are designed in accordance with
criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District
(UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated above, the subject property is not located in a City or FEMA designated
floodplain. The proposed project does not propose to modify any natural
drainageways.
F. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
Fort Collins Hotel
Preliminary Drainage Report 7
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the project drainage design are to maintain existing drainage
patterns, and to ensure no adverse impacts to any adjacent properties.
2. Onsite LID features will be provided and will enhance water quality. These measures
are discussed further below.
3. Drainage patterns anticipated for drainage basins shown in the Drainage Exhibit are
described below. Drainage basins have been defined for preliminary design purposes
and are subject to change at Final design; however, general drainage patterns and
concepts are not expected to be significantly altered.
Basins 1a through 1c
Basins 1a through 1c will generally drain via overland flow and roof drains into
proposed LID features and then into existing storm drain systems within Walnut Street
and Chestnut Street.
Basin 2
Basin 2 will generally drain via sheet flow into LID features and a series of proposed
area drains which will tie to the existing storm drain system within Chestnut Street.
Please see further discussion of LID features in Section IV.B, below.
Basins OS1, OS2
Basins OS1 and OS2 consist of areas to the north of the project site which sheet flow
towards the site. Basin OS1 will be conveyed through the site via the existing
alleyway (which will be improved) running in between the hotel portion of the site and
the parking area. Basin OS2 will be conveyed along the north side of the proposed
parking area and flow north into the adjacent Jefferson Street.
Basins OS3 through OS5
Basins OS3 through OS5 consist of adjacent Rights of Way of Walnut Street, Chestnut
Street, and Mountain Avenue. Basin OS3 will drain via sheet flow and curb and gutter
into an improved inlet to be constructed in Walnut Street, which will tie to the existing
storm line in Chestnut Street. Basin OS4 will drain via sheet flow and curb and gutter
into improved inlets to be constructed in Chestnut Street, which will tie to the existing
storm line in Chestnut Street. Basin OS5 will drain via sheet flow and curb and gutter
into the existing curb and gutter of Mountain Avenue.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report. Runoff computations for these basins based on the Rational Method is
provided in Appendix A.
B. Specific Details
1. Low Impact Design (LID) measures will be incorporated into the site design
which will consist of permeable paver fields placed at key on-site locations
within the development area. Design of the paver fields will include subdrain
systems draining into the adjacent Chestnut Street storm drain. Details of this
design will be provided at Final design. Preliminary locations of paver fields
are noted on the Drainage Exhibit.
Fort Collins Hotel
Preliminary Drainage Report 8
2. The following table summarizes proposed LID features and overall percentage of the
basin being treated by the proposed LID features.
Table 1 – LID Summary
50% On-Site Treatment by LID Requirement
New Impervious Area 1.670 Ac.
Paver Area 0.208 Ac.
Traditional Pavement Area 0.830 Ac.
Other Impervious Surfaces (Roofs, Concrete Walks, etc.) 0.632 Ac.
Required Minimum Impervious Area to be Treated 0.835 Ac.
Area of Pavers 0.208 Ac.
Run-on area for Pavers (parking area) 0.830 Ac.
Run-on area for Pavers (other - concrete walks, etc.) 0.080 Ac.
Impervious Area Treated by LID Pavers 1.118 Ac.
Total Impervious Area Treated 1.118 Ac.
Percent of Impervious Area Treated 66.92 %
25% Permeable Pavement Requirement
New Pavement Area 36154 Sq. Ft.
Required Minimum Area of Permeable Pavement 9039 Sq. Ft.
Total Permeable Pavement Area 9039 Sq. Ft.
Actual % of Permeable Pavement Provided 25.0 %
3. Final design details, construction documentation, and Standard Operating
Procedures (SOP) Manual shall be provided to the City of Fort Collins for
review prior to Final Development Plan approval. A final copy of the approved
SOP manual shall be provided to City and must be maintained on-site by the
entity responsible for the facility maintenance. Annual reports must also be
prepared and submitted to the City discussing the results of the maintenance
program (i.e. inspection dates, inspection frequency, volume loss due to
sedimentation, corrective actions taken, etc.).
4. Proper maintenance of the drainage facilities designed with the proposed
development is a critical component of their ongoing performance and
effectiveness.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the proposed project complies with the City of Fort
Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with this project complies with requirements for the Old
Town Basin.
3. The drainage plan and stormwater management measures proposed with the
Fort Collins Hotel
Preliminary Drainage Report 9
proposed development are compliant with all applicable State and Federal regulations
governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit any potential
damage associated with its stormwater runoff by compliance with requirements set
forth in current City master plans.
2. The drainage concept for the proposed development is consistent with requirements
for the Old Town Basin and the Downtown River District Final Design Report.
References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
2. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
4. Old Town Master Drainage Plan, Baseline Hydraulics, Volume II, Anderson Consulting,
July 15, 2003.
5. Downtown River District Final Design Report, Ayres, February 2012.
6. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A.1
HISTORIC CONDITIONS HYDROLOGIC COMPUATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: 947-002
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: ATC
Asphalt ……....……………...……….....…...……………….…………………………………. 0.95 100% Date:
Concrete …….......……………….….……….………………..….……………………………… 0.95 90%
Gravel ……….…………………….….…………………………..………………………………. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Lawn, Rain
Garden, or
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
H1a 1363 0.03 0.03 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
H1b 7543 0.17 0.17 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
H1c 34057 0.78 0.38 0.11 0.18 0.00 0.11 0.85 0.85 1.00 0.82
H2 47462 1.09 0.24 0.08 0.72 0.00 0.05 0.92 0.92 1.00 0.88
OS1 18920 0.43 0.43 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
OS2 10772 0.25 0.25 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
OS3 16862 0.39 0.33 0.06 0.00 0.00 0.00 0.95 0.95 1.00 0.98
OS4 30999 0.71 0.45 0.17 0.00 0.00 0.09 0.86 0.86 1.00 0.85
OS5 5138 0.12 0.08 0.02 0.00 0.00 0.02 0.82 0.82 1.00 0.80
Overland Flow, Time of Concentration:
Project: 947-002
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: 947-002
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
H1a H1a 0.03 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.08 0.14 0.31
H1b H1b 0.17 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.47 0.80 1.72
H1c H1c 0.78 5 5 5 0.85 0.85 1.00 2.85 4.87 9.95 1.90 3.25 7.78
H2 H2 1.09 5 5 5 0.92 0.92 1.00 2.85 4.87 9.95 2.86 4.88 10.84
OS1 OS1 0.43 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.18 2.01 4.32
OS2 OS2 0.25 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.67 1.14 2.46
OS3 OS3 0.39 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.05 1.79 3.85
OS4 OS4 0.71 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 1.74 2.98 7.08
OS5 OS5 0.12 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 0.28 0.47 1.17
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
HISTORIC RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
ATC
June 15, 2015
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Q C f C i A
APPENDIX A.2
DEVELOPED CONDITIONS HYDROLOGIC COMPUATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: 947-002
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: ATC
Asphalt ……....……………...……….....…...……………….…………………………………. 0.95 100% Date:
Concrete …….......……………….….……….………………..….……………………………… 0.95 90%
Gravel ……….…………………….….…………………………..………………………………. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Lawn, Rain
Garden, or
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
1a 1363 0.03 0.00 0.03 0.00 0.00 0.00 0.95 0.95 1.00 0.90
1b 7543 0.17 0.00 0.17 0.00 0.00 0.00 0.95 0.95 1.00 0.90
1c 34057 0.78 0.00 0.00 0.78 0.00 0.00 0.95 0.95 1.00 0.90
2 47462 1.09 0.83 0.01 0.00 0.00 0.25 0.79 0.79 0.99 0.77
OS1 18920 0.43 0.43 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
OS2 10772 0.25 0.25 0.00 0.00 0.00 0.00 0.95 0.95 1.00 1.00
OS3 16862 0.39 0.36 0.00 0.00 0.00 0.03 0.90 0.90 1.00 0.92
OS4 30999 0.71 0.22 0.57 0.00 0.00 -0.09 1.04 1.04 1.00 1.04
OS5 5138 0.12 0.09 0.02 0.00 0.00 0.01 0.89 0.89 1.00 0.90
Overland Flow, Time of Concentration:
Project: 947-002
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: 947-002
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1a 1a 0.03 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.08 0.14 0.31
1b 1b 0.17 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.47 0.80 1.72
1c 1c 0.78 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 2.11 3.61 7.78
2 2 1.09 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 2.45 4.19 10.69
OS1 OS1 0.43 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.18 2.01 4.32
OS2 OS2 0.25 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.67 1.14 2.46
OS3 OS3 0.39 5 5 5 0.90 0.90 1.00 2.85 4.87 9.95 0.99 1.69 3.85
OS4 OS4 0.71 5 5 5 1.04 1.04 1.00 2.85 4.87 9.95 2.10 3.59 7.08
OS5 OS5 0.12 5 5 5 0.89 0.89 1.00 2.85 4.87 9.95 0.30 0.51 1.17
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
ATC
June 15, 2015
Q C f C i A
APPENDIX B.1
EROSION CONTROL REPORT
Fort Collins Hotel
Preliminary Erosion Control Report
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. It should be noted, however, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at existing and proposed storm inlets. Vehicle tracking control pads, spill
containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site
restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet as well as a separate sheet dedicated to Erosion Control Details. In
addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere
to, the applicable requirements outlined in the Development Agreement for the development. Also,
the Site Contractor for this project will be required to secure a Stormwater Construction General
Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division – Stormwater Program, prior to any earth disturbance activities. Prior to securing
said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan
(SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and
document the ongoing activities, inspections, and maintenance of construction BMPs.
APPENDIX C.1
WATER WAWABASE FLOOD ELEVATION ANALYSIS
1
June 5, 2015
City of Fort Collins
Stormwater Utility
Attn: Mr. Shane Boyle, PE
700 Wood Street
Fort Collins, Colorado 80521
RE: 100-Year Flood Elevation Determination for
Downtown Fort Collins Hotel
Mr. Boyle:
Northern Engineering is pleased to submit this 100-Year Flood Elevation Determination for the
proposed Downtown Fort Collins Hotel for your review. The project is located just north of the
intersection of Walnut and Chestnut and Walnut Street.
VICINITY MAP North
Mitchell
Block
Project Site
Flow Split
Walnut St.
Chestnut St.
Mountain Ave.
2
The City of Fort Collins has identified Walnut Street and Chestnut Street as potential flooding
areas, and has requested we perform floodplain modeling to further define flood potential
within these adjacent roadways by determining 100-year flood elevations.
The project site is located just north of a previous project site, the “Mitchell Block”, for which
we conducted similar hydraulic modeling. This modeling was summarized in our previous
report entitled “Final Drainage Report for Mitchell Block”, dated February 25, 2009. However,
for the purposes of the Mitchell Block project, the previous modeling separated out flows in the
adjacent south half-street of Walnut Street, and determined a 100-year peak flow rate of 36.3
cfs. Additionally, the flow split at Chestnut Street was not analyzed because this was not
relevant to the Mitchell Block project.
In 2009, we obtained effective HEC-RAS files from the City of Fort Collins in order to set up base
hydraulic modeling. We added several cross-sections to the effective HEC-RAS model in the
streets adjacent to the Mitchell Block project (Mountain Avenue and Walnut Street). Please
see the effective model workmap in Appendix 1.1.
For current modeling efforts, the base modeling obtained from the City of Fort Collins in 2009
for the Mitchell Block was utilized as our starting point. However, in order to model the flow
split at Walnut and Chestnut, we needed to create a separate truncated model because HEC-
RAS does not allow a flow split junction to have multiple reaches entering and exiting the
junction. The truncated model we created is named “Oak_NEmod” and is provided in
Attachment 2.2.
This model focuses on the flow split that occurs at the Walnut Street, Chestnut Street, and
Mountain Avenue confluence. We used the effective model peak 100-year flow in Walnut of
60.0 cfs, and we also utilized the effective model water surface elevation in Mountain Avenue
near section 11+00 of 4976.18 as a starting water surface elevation in Mountain Ave. This
water surface elevation is conservative, as it is based on 100% of the flow from Walnut St.
entering Mountain Ave., resulting in slightly higher water surface elevations within our area of
interest. The starting water surface elevation was converted from NGVD-29 to NAVD-88
utilizing a conversion factor of 3.18-ft, based on City of Fort Collins Bechmark No. 5-00.
Several cross-sections were added within Walnut Street, Chestnut Street, and Mountain
Avenue in order to define the flow split that occurs at the intersection. We utilized the same
parameters found in the effective HEC-RAS model, with n-values in both channel and overbank
of 0.016. A hydraulic modeling workmap for the current model “Oak_NEmod”, is provided in
Appendix 2.1. Table 1, below provides a summary of our modeling results.
As shown in Table 1, a flow split occurs at the intersection of Walnut St., Chestnut St., and
Mountain Ave. such that roughly 33% of the flow in Walnut St. goes to Chestnut St. and roughly
67% of the flow goes to Mountain Ave. This is reasonable, as the Chestnut St. turn lane has a
little less than half the conveyance area of that of the Mountain Ave. turn-off.
3
TABLE 1 – HEC-RAS MODELING RESULTS
Street Section ID 100-Yr
Discharge (CFS)
100-Yr WSEL
(Ft-NAVD88)
Walnut St. 10 60 4977.13
Walnut St. 20 60 4978.81
Chestnut St. 10 19.58 4974.08
Chestnut St. 20 19.58 4975.26
Chestnut St. 30 19.58 4976.69
Mountain Ave. 10 40.42 4976.18
Mountain Ave. 20 40.42 4976.71
If you should have any questions as you review this, please feel free to contact us at your
earliest convenience.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Aaron Cvar, PE
Project Engineer
ATTACHMENT 1.1
EFFECTIVE HEC-RAS MODELING WORKMAP
ATTACHMENT 2.1
PROPOSED CONDITION HEC-RAS MODELING WORKMAP
W
MOUNTAIN
AVE.
SPLIT
CHESTNUT
ST.
SPLIT
WALNUT ST.
10
20
30
10
20
10
20
WALNUT STREET
CHESTNUT STREET
MOUNTAIN AVENUE
PROJECT SITE
NORTH
( IN FEET )
1 inch = ft.
60 0 60 Feet
60
HEC-RAS MODELING
EXHIBIT
ATTACHMENT 2.2
PROPOSED CONDITION HEC-RAS MODEL OUTPUT
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
HEC-RAS Version 4.1.0 Jan 2010
U.S. Army Corps of Engineers
Hydrologic Engineering Center
609 Second Street
Davis, California
X X XXXXXX XXXX XXXX XX XXXX
X X X X X X X X X X
X X X X X X X X X
XXXXXXX XXXX X XXX XXXX XXXXXX XXXX
X X X X X X X X X
X X X X X X X X X X
X X XXXXXX XXXX X X X X XXXXX
PROJECT DATA
Project Title: Oak Street Outfall - 100yr-Proposed
Project File : Oak_NEmod.prj
Run Date and Time: 6/8/2015 3:30:00 PM
Project in English units
PLAN DATA
Plan Title: Plan01_Chestnut Split
Plan File : d:\Projects\947-002\Drainage\Modeling\HEC-RAS\Proposed Cond-2015-06-02\Oak_NEmod.p01
Geometry Title: Chestnut Split Flow
Geometry File : d:\Projects\947-002\Drainage\Modeling\HEC-RAS\Proposed Cond-2015-06-
02\Oak_NEmod.g01
Flow Title : Flow 01
Flow File : d:\Projects\947-002\Drainage\Modeling\HEC-RAS\Proposed Cond-2015-06-
02\Oak_NEmod.f01
Plan Summary Information:
Number of: Cross Sections = 7 Multiple Openings = 0
Culverts = 0 Inline Structures = 0
Bridges = 0 Lateral Structures = 0
Computational Information
Water surface calculation tolerance = 0.01
Critical depth calculation tolerance = 0.01
Maximum number of iterations = 20
Maximum difference tolerance = 0.3
Flow tolerance factor = 0.001
Computation Options
Critical depth computed only where necessary
Conveyance Calculation Method: At breaks in n values only
Friction Slope Method: Average Conveyance
Computational Flow Regime: Subcritical Flow
FLOW DATA
Flow Title: Flow 01
Flow File : d:\Projects\947-002\Drainage\Modeling\HEC-RAS\Proposed Cond-2015-06-02\Oak_NEmod.f01
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
Flow Data (cfs)
River Reach RS PF 1
Chestnut Split 1 30 10
Mountain 1 20 50
Walnut 1 20 60
Mountain Split 1 20 50
Boundary Conditions
River Reach Profile Upstream
Downstream
Chestnut Split 1 PF 1 Normal S =
0.005
Mountain Split 1 PF 1 Known WS =
4976.18
GEOMETRY DATA
Geometry Title: Chestnut Split Flow
Geometry File : d:\Projects\947-002\Drainage\Modeling\HEC-RAS\Proposed Cond-2015-06-
02\Oak_NEmod.g01
Reach Connection Table
River Reach Upstream Boundary Downstream Boundary
Chestnut Split 1 Split_1
Mountain Split 1 Split_1
Walnut 1 Split_1
JUNCTION INFORMATION
Name: Split_1
Description:
Energy computation Method
Length across Junction Tributary
River Reach River Reach Length Angle
Walnut 1 to Chestnut Split 1 70.4
Walnut 1 to Mountain Split 1 70.4
CROSS SECTION
RIVER: Chestnut Split
REACH: 1 RS: 30
INPUT
Description:
Station Elevation Data num= 6
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
0 4977.14 23 4976.68 23.05 4976.18 41 4976.54 41.05 4977.04
46 4977.2
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
0 .016 0 .016 46 .016
Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan.
0 46 224.9 224.9 224.9 .1 .3
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4976.86 Element Left OB Channel Right OB
Vel Head (ft) 0.17 Wt. n-Val. 0.016
W.S. Elev (ft) 4976.69 Reach Len. (ft) 224.90 224.90 224.90
Crit W.S. (ft) 4976.69 Flow Area (sq ft) 6.00
E.G. Slope (ft/ft) 0.005847 Area (sq ft) 6.00
Q Total (cfs) 19.58 Flow (cfs) 19.58
Top Width (ft) 18.67 Top Width (ft) 18.67
Vel Total (ft/s) 3.26 Avg. Vel. (ft/s) 3.26
Max Chl Dpth (ft) 0.51 Hydr. Depth (ft) 0.32
Conv. Total (cfs) 256.0 Conv. (cfs) 256.0
Length Wtd. (ft) 224.90 Wetted Per. (ft) 19.27
Min Ch El (ft) 4976.18 Shear (lb/sq ft) 0.11
Alpha 1.00 Stream Power (lb/ft s) 46.00 0.00 0.00
Frctn Loss (ft) 1.37 Cum Volume (acre-ft) 0.05
C & E Loss (ft) 0.01 Cum SA (acres) 0.20
Warning: The energy equation could not be balanced within the specified number of iterations.
The program used critical depth
for the water surface and continued on with the calculations.
Warning: The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross
section. This may indicate the
need for additional cross sections.
Warning: During the standard step iterations, when the assumed water surface was set equal to
critical depth, the calculated water
surface came back below critical depth. This indicates that there is not a valid
subcritical answer. The program
defaulted to critical depth.
CROSS SECTION
RIVER: Chestnut Split
REACH: 1 RS: 20
INPUT
Description:
Station Elevation Data num= 7
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
0 4975.45 10 4975.25 10.05 4974.75 27 4975.4 44 4974.75
44.05 4975.25 54 4975.45
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
0 .016 0 .016 54 .016
Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan.
0 54 113.1 113.1 113.1 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4975.39 Element Left OB Channel Right OB
Vel Head (ft) 0.13 Wt. n-Val. 0.016
W.S. Elev (ft) 4975.26 Reach Len. (ft) 113.10 113.10 113.10
Crit W.S. (ft) 4975.26 Flow Area (sq ft) 6.90
E.G. Slope (ft/ft) 0.006352 Area (sq ft) 6.90
Q Total (cfs) 19.58 Flow (cfs) 19.58
Top Width (ft) 28.15 Top Width (ft) 28.15
Vel Total (ft/s) 2.84 Avg. Vel. (ft/s) 2.84
Max Chl Dpth (ft) 0.51 Hydr. Depth (ft) 0.25
Conv. Total (cfs) 245.6 Conv. (cfs) 245.6
Length Wtd. (ft) 113.10 Wetted Per. (ft) 29.07
Min Ch El (ft) 4974.75 Shear (lb/sq ft) 0.09
Alpha 1.00 Stream Power (lb/ft s) 54.00 0.00 0.00
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
Frctn Loss (ft) 0.63 Cum Volume (acre-ft) 0.02
C & E Loss (ft) 0.01 Cum SA (acres) 0.07
Warning: The energy equation could not be balanced within the specified number of iterations.
The program used critical depth
for the water surface and continued on with the calculations.
Warning: Divided flow computed for this cross-section.
Warning: The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross
section. This may indicate the
need for additional cross sections.
Warning: During the standard step iterations, when the assumed water surface was set equal to
critical depth, the calculated water
surface came back below critical depth. This indicates that there is not a valid
subcritical answer. The program
defaulted to critical depth.
CROSS SECTION
RIVER: Chestnut Split
REACH: 1 RS: 10
INPUT
Description:
Station Elevation Data num= 36
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
0 4981 .1 4974.78 3.76 4974.66 6.16 4974.7 6.45 4974.71
7.98 4974.52 10.34 4974.24 10.6 4974.09 10.87 4973.88 12.36 4973.95
23.84 4974.25 24.64 4974.27 25.25 4974.27 48.43 4974.49 48.98 4974.49
61.12 4974.31 67.12 4974.22 84.73 4973.44 85.39 4973.42 85.42 4973.42
86.39 4973.5 86.52 4973.36 86.71 4973.68 86.85 4973.85 86.88 4973.85
86.97 4973.81 86.98 4973.81 87.05 4973.81 87.08 4973.81 89.84 4973.88
93.27 4974.09 95.28 4974.27 96.53 4974.34 97.34 4974.36 98.5 4974.38
98.6 4981
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
0 .016 3.76 .016 96.53 .016
Bank Sta: Left Right Coeff Contr. Expan.
3.76 96.53 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4974.19 Element Left OB Channel Right OB
Vel Head (ft) 0.11 Wt. n-Val. 0.016
W.S. Elev (ft) 4974.08 Reach Len. (ft)
Crit W.S. (ft) 4974.05 Flow Area (sq ft) 7.50
E.G. Slope (ft/ft) 0.004994 Area (sq ft) 7.50
Q Total (cfs) 19.58 Flow (cfs) 19.58
Top Width (ft) 29.43 Top Width (ft) 29.43
Vel Total (ft/s) 2.61 Avg. Vel. (ft/s) 2.61
Max Chl Dpth (ft) 0.72 Hydr. Depth (ft) 0.25
Conv. Total (cfs) 277.0 Conv. (cfs) 277.0
Length Wtd. (ft) Wetted Per. (ft) 29.86
Min Ch El (ft) 4973.36 Shear (lb/sq ft) 0.08
Alpha 1.00 Stream Power (lb/ft s) 98.60 0.00 0.00
Frctn Loss (ft) Cum Volume (acre-ft)
C & E Loss (ft) Cum SA (acres)
Warning: Divided flow computed for this cross-section.
CROSS SECTION
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
RIVER: Mountain Split
REACH: 1 RS: 20
INPUT
Description:
Station Elevation Data num= 37
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
7.25 4978.23 11.84 4978.11 12.27 4978.08 12.74 4978.03 18.87 4977.05
18.95 4976.97 19.39 4976.54 19.68 4976.56 21.38 4976.68 26.56 4976.67
38.06 4976.66 38.09 4976.66 38.1 4976.66 38.53 4976.67 38.93 4976.68
39.8 4976.68 39.85 4976.63 40 4976.63 41.56 4976.64 45.49 4976.46
49.69 4976.39 52.51 4976.38 62.19 4976.2 64.02 4976.18 65.86 4975.88
66.23 4975.83 66.56 4975.83 66.78 4976.08 67.15 4976.5 69.14 4976.51
71.09 4976.52 71.24 4976.5 72.64 4976.36 73.48 4976.41 74.36 4976.47
75.62 4976.53 80 4976.68
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
7.25 .016 11.84 .016 75.62 .016
Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan.
11.84 75.62 179.3 179.3 179.3 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4976.85 Element Left OB Channel Right OB
Vel Head (ft) 0.14 Wt. n-Val. 0.016 0.016
W.S. Elev (ft) 4976.71 Reach Len. (ft) 179.30 179.30 179.30
Crit W.S. (ft) 4976.71 Flow Area (sq ft) 13.25 0.48
E.G. Slope (ft/ft) 0.007216 Area (sq ft) 13.25 0.48
Q Total (cfs) 40.42 Flow (cfs) 39.57 0.85
Top Width (ft) 60.79 Top Width (ft) 56.41 4.38
Vel Total (ft/s) 2.95 Avg. Vel. (ft/s) 2.99 1.79
Max Chl Dpth (ft) 0.88 Hydr. Depth (ft) 0.23 0.11
Conv. Total (cfs) 475.9 Conv. (cfs) 465.8 10.0
Length Wtd. (ft) 179.30 Wetted Per. (ft) 56.86 4.42
Min Ch El (ft) 4975.83 Shear (lb/sq ft) 0.10 0.05
Alpha 1.01 Stream Power (lb/ft s) 80.00 0.00 0.00
Frctn Loss (ft) 0.15 Cum Volume (acre-ft) 0.00 0.12 0.00
C & E Loss (ft) 0.04 Cum SA (acres) 0.00 0.33 0.01
Warning: The energy equation could not be balanced within the specified number of iterations.
The program used critical depth
for the water surface and continued on with the calculations.
Warning: The cross-section end points had to be extended vertically for the computed water
surface.
Warning: The conveyance ratio (upstream conveyance divided by downstream conveyance) is less
than 0.7 or greater than 1.4.
This may indicate the need for additional cross sections.
Warning: During the standard step iterations, when the assumed water surface was set equal to
critical depth, the calculated water
surface came back below critical depth. This indicates that there is not a valid
subcritical answer. The program
defaulted to critical depth.
CROSS SECTION
RIVER: Mountain Split
REACH: 1 RS: 10
INPUT
Description:
Station Elevation Data num= 61
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
0 4981 .1 4975.92 1.42 4975.93 9.93 4975.63 12.88 4975.5
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
14.56 4975.4 16.97 4975.33 17.37 4975.03 17.58 4974.86 19.22 4974.97
19.58 4975.01 19.61 4975 22.89 4975.25 23.47 4975.28 27.21 4975.47
27.47 4975.48 32.38 4975.69 34.39 4975.78 34.67 4975.79 35.43 4975.78
35.44 4975.8 39.92 4975.91 41.77 4975.94 48.53 4976.15 53.97 4976.21
58.88 4976.26 60.92 4976.22 62.38 4976.23 63.6 4976.25 64.06 4976.25
65.81 4976.23 67.99 4976.22 69.08 4976.19 74.15 4975.99 74.66 4976.96
74.69 4977.01 75.43 4976.95 76.47 4976.87 77.6 4976.84 79.53 4977.05
79.89 4976.19 79.99 4975.98 83.06 4976 94.01 4976.12 100.59 4975.94
106.07 4975.78 110.29 4975.67 112.77 4975.61 121.21 4975.39 121.8 4975.34
123.21 4975.22 123.36 4975.36 123.71 4975.72 126.88 4975.77 128.14 4975.78
128.27 4975.79 128.62 4975.78 128.76 4975.8 128.87 4976.13 128.91 4975.79
129 4981
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
0 .016 1.42 .016 126.88 .016
Bank Sta: Left Right Coeff Contr. Expan.
1.42 126.88 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4976.19 Element Left OB Channel Right OB
Vel Head (ft) 0.01 Wt. n-Val. 0.016 0.016 0.016
W.S. Elev (ft) 4976.18 Reach Len. (ft)
Crit W.S. (ft) 4975.77 Flow Area (sq ft) 0.34 43.52 0.79
E.G. Slope (ft/ft) 0.000302 Area (sq ft) 0.34 43.52 0.79
Q Total (cfs) 40.42 Flow (cfs) 0.19 39.70 0.53
Top Width (ft) 105.12 Top Width (ft) 1.33 101.76 2.04
Vel Total (ft/s) 0.91 Avg. Vel. (ft/s) 0.58 0.91 0.67
Max Chl Dpth (ft) 1.32 Hydr. Depth (ft) 0.25 0.43 0.39
Conv. Total (cfs) 2325.6 Conv. (cfs) 11.2 2284.1 30.3
Length Wtd. (ft) Wetted Per. (ft) 1.58 102.45 2.96
Min Ch El (ft) 4974.86 Shear (lb/sq ft) 0.00 0.01 0.01
Alpha 1.01 Stream Power (lb/ft s) 129.00 0.00 0.00
Frctn Loss (ft) Cum Volume (acre-ft)
C & E Loss (ft) Cum SA (acres)
Warning: Divided flow computed for this cross-section.
CROSS SECTION
RIVER: Walnut
REACH: 1 RS: 20
INPUT
Description: Effective Model Section 2+58
Station Elevation Data num= 13
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
100 4981.18 100.1 4979.08 106.2 4978.78 116 4978.32 116.2 4977.9
118.3 4977.77 141.2 4979.02 153.9 4979.2 165.7 4979.02 191.3 4978.48
191.6 4978.98 203.6 4979.18 203.7 4981.18
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
100 .016 106.2 .016 203.6 .016
Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan.
106.2 203.6 183.3 183.3 183.3 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4979.00 Element Left OB Channel Right OB
Vel Head (ft) 0.19 Wt. n-Val. 0.016 0.016
W.S. Elev (ft) 4978.81 Reach Len. (ft) 183.30 183.30 183.30
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
Crit W.S. (ft) 4978.81 Flow Area (sq ft) 0.01 17.12
E.G. Slope (ft/ft) 0.005516 Area (sq ft) 0.01 17.12
Q Total (cfs) 60.00 Flow (cfs) 0.00 60.00
Top Width (ft) 47.36 Top Width (ft) 0.56 46.80
Vel Total (ft/s) 3.50 Avg. Vel. (ft/s) 0.39 3.50
Max Chl Dpth (ft) 1.04 Hydr. Depth (ft) 0.01 0.37
Conv. Total (cfs) 807.8 Conv. (cfs) 0.0 807.8
Length Wtd. (ft) 183.30 Wetted Per. (ft) 0.56 47.30
Min Ch El (ft) 4977.77 Shear (lb/sq ft) 0.00 0.12
Alpha 1.00 Stream Power (lb/ft s) 203.70 0.00 0.00
Frctn Loss (ft) 0.92 Cum Volume (acre-ft) 0.00 0.10 0.01
C & E Loss (ft) 0.02 Cum SA (acres) 0.00 0.24 0.03
Warning: The energy equation could not be balanced within the specified number of iterations.
The program used critical depth
for the water surface and continued on with the calculations.
Warning: Divided flow computed for this cross-section.
Warning: The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross
section. This may indicate the
need for additional cross sections.
Warning: During the standard step iterations, when the assumed water surface was set equal to
critical depth, the calculated water
surface came back below critical depth. This indicates that there is not a valid
subcritical answer. The program
defaulted to critical depth.
CROSS SECTION
RIVER: Walnut
REACH: 1 RS: 10
INPUT
Description:
Station Elevation Data num= 49
Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev
0 4981 1.02 4977.13 1.14 4977.1 8.14 4976.98 8.84 4976.96
10.44 4976.82 11.7 4976.81 11.94 4976.8 12.29 4976.37 12.38 4976.28
12.92 4976.23 14.83 4976.19 19.29 4976.53 20.24 4976.59 21.78 4976.67
28.24 4976.97 38.58 4977.18 44.11 4977.29 46.18 4977.32 46.6 4977.31
54.9 4977.12 62.06 4976.91 66.97 4976.8 67.12 4976.8 68.6 4976.75
71.42 4976.67 72.77 4976.6 74.13 4976.51 74.79 4976.84 74.98 4976.96
74.99 4976.98 76.48 4977.16 77.63 4976.94 78.24 4976.93 80.15 4976.93
80.23 4976.79 80.25 4976.78 81.82 4976.85 82.66 4976.89 83.28 4976.93
86.58 4976.93 89.45 4976.96 91.08 4976.92 91.47 4976.92 92.26 4976.92
98.6 4976.88 99.55 4976.88 101.6 4976.89 101.7 4981
Manning's n Values num= 3
Sta n Val Sta n Val Sta n Val
0 .016 1.02 .016 89.45 .016
Bank Sta: Left Right Coeff Contr. Expan.
1.02 89.45 .1 .3
CROSS SECTION OUTPUT Profile #PF 1
E.G. Elev (ft) 4977.24 Element Left OB Channel Right OB
Vel Head (ft) 0.11 Wt. n-Val. 0.016 0.016
W.S. Elev (ft) 4977.13 Reach Len. (ft)
Crit W.S. (ft) 4977.11 Flow Area (sq ft) 19.78 2.73
E.G. Slope (ft/ft) 0.004606 Area (sq ft) 19.78 2.73
Q Total (cfs) 60.00 Flow (cfs) 53.74 6.26
Top Width (ft) 81.54 Top Width (ft) 69.38 12.16
Vel Total (ft/s) 2.67 Avg. Vel. (ft/s) 2.72 2.30
Max Chl Dpth (ft) 0.94 Hydr. Depth (ft) 0.29 0.22
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
Length Wtd. (ft) Wetted Per. (ft) 69.91 12.39
Min Ch El (ft) 4976.19 Shear (lb/sq ft) 0.08 0.06
Alpha 1.01 Stream Power (lb/ft s) 101.70 0.00 0.00
Frctn Loss (ft) 0.38 Cum Volume (acre-ft) 0.02 0.00
C & E Loss (ft) 0.00 Cum SA (acres)
Warning: Divided flow computed for this cross-section.
Warning: A flow split was encountered. The program first calculated the momentum of both
channels below the junction. An
energy balance was performed across the junction from the stream with the highest
momentum downstream to the
section upstream.
SUMMARY OF MANNING'S N VALUES
River:Chestnut Split
Reach River Sta. n1 n2 n3
1 30 .016 .016 .016
1 20 .016 .016 .016
1 10 .016 .016 .016
River:Mountain Split
Reach River Sta. n1 n2 n3
1 20 .016 .016 .016
1 10 .016 .016 .016
River:Walnut
Reach River Sta. n1 n2 n3
1 20 .016 .016 .016
1 10 .016 .016 .016
SUMMARY OF REACH LENGTHS
River: Chestnut Split
Reach River Sta. Left Channel Right
1 30 224.9 224.9 224.9
1 20 113.1 113.1 113.1
1 10
River: Mountain Split
Reach River Sta. Left Channel Right
1 20 179.3 179.3 179.3
1 10
River: Walnut
Reach River Sta. Left Channel Right
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
1 20 183.3 183.3 183.3
1 10
SUMMARY OF CONTRACTION AND EXPANSION COEFFICIENTS
River: Chestnut Split
Reach River Sta. Contr. Expan.
1 30 .1 .3
1 20 .1 .3
1 10 .1 .3
River: Mountain Split
Reach River Sta. Contr. Expan.
1 20 .1 .3
1 10 .1 .3
River: Walnut
Reach River Sta. Contr. Expan.
1 20 .1 .3
1 10 .1 .3
Profile Output Table - Standard Table 1
River Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit
W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl
(cfs) (ft) (ft)
(ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)
Chestnut Split 1 10 PF 1 19.58 4973.36 4974.08
4974.05 4974.19 0.004994 2.61 7.50 29.43 0.91
Chestnut Split 1 20 PF 1 19.58 4974.75 4975.26
4975.26 4975.39 0.006352 2.84 6.90 28.15 1.01
Chestnut Split 1 30 PF 1 19.58 4976.18 4976.69
4976.69 4976.86 0.005847 3.26 6.00 18.67 1.01
Mountain Split 1 10 PF 1 40.42 4974.86 4976.18
4975.77 4976.19 0.000302 0.91 44.65 105.12 0.25
Mountain Split 1 20 PF 1 40.42 4975.83 4976.71
4976.71 4976.85 0.007216 2.99 13.72 60.79 1.09
Walnut 1 10 PF 1 60.00 4976.19 4977.13
4977.11 4977.24 0.004606 2.72 22.51 81.54 0.90
Walnut 1 20 PF 1 60.00 4977.77 4978.81
4978.81 4979.00 0.005516 3.50 17.13 47.36 1.02
Profile Output Table - Standard Table 2
River Reach River Sta Profile E.G. Elev W.S. Elev Vel Head
Frctn Loss C & E Loss Q Left Q Channel Q Right Top Width
(ft) (ft) (ft)
(ft) (ft) (cfs) (cfs) (cfs) (ft)
Chestnut Split 1 10 PF 1 4974.19 4974.08 0.11
19.58 29.43
OAK STREET OUTFALL; TRUNCATED MODEL
FORT COLLINS DOWNTOWN HOTEL
100-YR PROPOSED CONDITION
NORTHERN ENGINEERING; 6/1/15
Chestnut Split 1 20 PF 1 4975.39 4975.26 0.13
0.63 0.01 19.58 28.15
Chestnut Split 1 30 PF 1 4976.86 4976.69 0.17
1.37 0.01 19.58 18.67
Mountain Split 1 10 PF 1 4976.19 4976.18 0.01
0.19 39.70 0.53 105.12
Mountain Split 1 20 PF 1 4976.85 4976.71 0.14
0.15 0.04 39.57 0.85 60.79
Walnut 1 10 PF 1 4977.24 4977.13 0.11
0.38 0.00 53.74 6.26 81.54
Walnut 1 20 PF 1 4979.00 4978.81 0.19
0.92 0.02 0.00 60.00 47.36
MAP POCKET
DRAINAGE EXHIBITS
LEGEND:
FIELD SURVEY BY:
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
R
( IN FEET )
0
1 INCH = 20 FEET
20 20 40 60
MOUNTAIN AVENUE
PROPOSED
DOWNTOWN HOTEL
EXISTING PROPERTY LINE
EXISTING RIGHT-OF-WAY
EXISTING
RIGHT-OF-WAY
EXISTING RIGHT-OF-WAY
EXISTING PROPERTY LINE
ISS. #
KEY PLAN
DESCRIPTION DATE
ARCHITECT'S PROJECT NUMBER
copyright 2015
NOT FOR
CONSTRUCTION
OWNER
4240 ARCHITECTURE INC
3507 RINGSBY COURT SUITE 117
DENVER, CO 80216
t: 303.292.3388 f: 303.292.3113
ARCHITECT
WALNUT ST & CHESTNUT ST
FORT COLLINS, CO 80524
21129.00
FORT COLLINS HOTEL
MCWHINNEY
2725 ROCKY MOUNTAIN AVE STE 200
LOVELAND, CO 80538
OWNER
SAGE HOSPITALITY
1575 WELTON STREET STE 300
DENVER, CO 80202
OPERATOR
t: 970.962.9990
t: 303.595.7200 f: 303.595.7219
BOHEMIAN COMPANIES
262 E MOUNTAIN AVE
FORT COLLINS, CO 80524
t: 970.490.2626
NORTHERN ENGINEERING, INC
200 S COLLEGE AVE
FORT COLLINS, CO 80524
CIVIL
RUSSELL + MILLS STUDIOS
141 S COLLEGE AVE
FORT COLLINS, CO 80524
LANDSCAPE
t: 970.568.5415 f: 970.221.4159
t: 970.484.8855
A PDP SUBMITTAL 24 JUNE 2015
C500
DRAINAGE PLAN
PARKING LOT ALTERNATIVE
NOTES:
REVIEW SET
NOT FOR CONSTRUCTION
REVIEW SET
NOT FOR CONSTRUCTION
PROPOSED 2' WIDE CONCRETE CHASE
EXISTING
DRIVEWAY
LIMITS OF CONSTRUCTION
A
B2
1.45 ac
Conv. Total (cfs) 884.1 Conv. (cfs) 791.8 92.3
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1a 1a No 0.95 0.95 1.00 20 2.00% 1.0 1.0 0.7 53 1.00% 2.00 0.4 0 0.00% N/A N/A 5 5 5
1b 1b No 0.95 0.95 1.00 20 2.00% 1.0 1.0 0.7 307 1.00% 2.00 2.6 0 0.00% N/A N/A 5 5 5
1c 1c No 0.95 0.95 1.00 45 1.00% 1.9 1.9 1.3 183 1.00% 2.00 1.5 0 0.00% N/A N/A 5 5 5
22No0.95 0.95 1.00 75 2.00% 1.9 1.9 1.3 168 0.50% 1.41 2.0 0 0.00% N/A N/A 5 5 5
OS1 OS1 No 0.95 0.95 1.00 45 1.00% 1.9 1.9 1.3 112 0.50% 1.41 1.3 0 0.00% N/A N/A 5 5 5
OS2 OS2 No 0.95 0.95 1.00 30 1.00% 1.5 1.5 1.0 144 0.50% 1.41 1.7 0 0.00% N/A N/A 5 5 5
OS3 OS3 No 0.95 0.95 1.00 30 2.00% 1.2 1.2 0.8 124 0.50% 1.41 1.5 0 0.00% N/A N/A 5 5 5
OS4 OS4 No 0.95 0.95 1.00 40 2.00% 1.4 1.4 0.9 320 0.50% 1.41 3.8 0 0.00% N/A N/A 5 5 5
OS5 OS5 No 0.95 0.95 1.00 30 2.00% 1.2 1.2 0.8 56 0.50% 1.41 0.7 0 0.00% N/A N/A 5 5 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
ATC
June 15, 2015
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
June 15, 2015
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
H1a H1a No 0.95 0.95 1.00 20 2.00% 1.0 1.0 0.7 53 0.50% 1.41 0.6 0 0.00% N/A N/A 5 5 5
H1b H1b No 0.95 0.95 1.00 20 2.00% 1.0 1.0 0.7 307 0.50% 1.41 3.6 0 0.00% N/A N/A 5 5 5
H1c H1c No 0.95 0.95 1.00 112 1.70% 2.5 2.5 1.7 221 0.80% 1.79 2.1 0 0.00% N/A N/A 5 5 5
H2 H2 No 0.95 0.95 1.00 30 2.00% 1.2 1.2 0.8 188 0.50% 1.41 2.2 0 0.00% N/A N/A 5 5 5
OS1 OS1 No 0.95 0.95 1.00 45 1.00% 1.9 1.9 1.3 112 0.50% 1.41 1.3 0 0.00% N/A N/A 5 5 5
OS2 OS2 No 0.95 0.95 1.00 30 1.00% 1.5 1.5 1.0 144 0.50% 1.41 1.7 0 0.00% N/A N/A 5 5 5
OS3 OS3 No 0.95 0.95 1.00 30 2.00% 1.2 1.2 0.8 124 0.50% 1.41 1.5 0 0.00% N/A N/A 5 5 5
OS4 OS4 No 0.95 0.95 1.00 40 2.00% 1.4 1.4 0.9 320 0.50% 1.41 3.8 0 0.00% N/A N/A 5 5 5
OS5 OS5 No 0.95 0.95 1.00 30 2.00% 1.2 1.2 0.8 56 0.50% 1.41 0.7 0 0.00% N/A N/A 5 5 5
HISTORIC TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
ATC
June 15, 2015
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
HISTORIC COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
June 15, 2015