HomeMy WebLinkAbout320 MAPLE MIXED-USE - FDP - FDP160032 - REPORTS - DRAINAGE REPORTSeptember 14, 2016
FINAL DRAINAGE REPORT
MAPLE MIXED USE
Fort Collins, Colorado
Prepared for:
Alex Schuman
Schuman Companies, Inc.
605 S. College Avenue, Suite 100
Fort Collins, Colorado 80524
Prepared by:
301 N. Howes Street Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 574-007
PThis 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.
September 14, 2016
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
Maple Mixed Use
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage Report for your review. This
report accompanies the Final Plan submittal for the proposed Maple Mixed Use
development.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria
Manual (FCSCM), and serves to document the stormwater impacts associated with the
proposed Maple Mixed Use housing project. We understand that review by the City of Fort
Collins 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, PhD, PE
Senior Project Engineer
Maple Mixed Use
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 4
III. DRAINAGE DESIGN CRITERIA ......................................................................... 5
IV. DRAINAGE FACILITY DESIGN .......................................................................... 8
V. CONCLUSIONS............................................................................................. 10
References ............................................................................................................. 11
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Hydraulic Computations
B.2 – Detention Facilities
APPENDIX C – Water Quality Design Computations, LID Information
APPENDIX D – Erosion Control Report
APPENDIX E – USDA Soils Report
MAP POCKET:
DR1 – Drainage Exhibit
DR2 – Existing Drainage Exhibit
Maple Mixed Use
Page|1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 – Vicinity Map
2. The Maple Mixed Use project site is located in the southwest quarter of Section 11,
Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins,
County of Larimer, State of Colorado.
3. The project site (refer to Figure 1) is bordered to the north by a single family
residence; to the south by Maple Street (100’ ROW); to the east by an existing public
alley (20' Right-of-Way); and to the west by Meldrum Street (100’ ROW).
4. There are no major drainageways within or adjacent to the site.
Maple Mixed Use
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B. Description of Property
1. Maple Mixed Use is comprised of ±0.65 acres.
2. The site is currently occupied by two commercial buildings, a single family residence
and several small outbuildings.
Figure 2 – Aerial Photograph
3. The existing groundcover consists of grasses, asphalt and gravel. The existing on-site
runoff generally drains from the southwest-to-northeast east across flat grades (e.g.,
<2.00%) into the existing alley. From there it is directed to Maple Street via the
alley, and then to an existing inlet via curb and gutter on Maple. The existing inlet is
located at the intersection of Maple and Howes, at the northwest corner. From there,
the drainage continues through an existing storm system down Maple Street to a large
regional drainage culvert near Mason Street, and on to the Cache La Poudre River.
4. 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).
5. There are no major drainageways within or adjacent to the project site.
6. The proposed Maple Mixed Use development will consist of a single mixed-use
building. Other proposed improvements include: a new concrete parking area located
under the building, new sidewalks and new landscaping.
7. The proposed land use is mixed-use. This is a permitted use in the Downtown District
(D).
Project Site
Maple Mixed Use
Page|3
Floodplain
8. The subject property is not located in a FEMA regulatory floodplain. In particular, the
project site is not located within a FEMA designated 100-year floodplain per Map
Number 08069C0979H (Effective date: May 2, 2012).
The project site is, however, located adjacent to a City of Fort Collins regulated Old
Town floodplain.
Figure 4 – FEMA Firmette (Map Number 08069C0979H)
9. Our initial analysis of the Old Town Floodplain adjacent to the project site
indicated that the City floodplain and floodway limits did not necessarily match
existing observed conditions. As such, the project has completed an updated
HEC-RAS model of the Old Town Floodplain using field survey data collected by
Northern Engineering. The results of the updated modeling indicate that the limit
of the existing Old Town Floodplain adjacent to the property should more closely
follow the existing sidewalk along Maple Street. Final results of this modeling
have been submitted in a floodplain modeling report, and are currently being
reviewed. If the results are accepted, the building envelope will not be located
within any City or FEMA floodplain.
Project Site
Maple Mixed Use
Page|4
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. Maple Mixed Use is located within the City of Fort Collins Old Town major drainage
basin. Specifically, the project site is situated in the north-central portion of this major
drainage basin. This basin is located in north-central Fort Collins and has a drainage
area of approximately 2,120 acres, including approximately 400 acres of the Colorado
State University campus. The Old Town major drainage basin generally drains from
west to east. It receives some runoff from the Canal Importation Basin directly west of
Old Town. Most of the runoff from the Old Town major drainage basin drains into the
Poudre River.
B. Sub-Basin Description
1. The outfall for the project site is the existing storm line in Maple Street.
2. The existing subject site can be defined with one (1) sub-basin. Refer to the Existing
Drainage Exhibit for additional information.
· Sub-basin EX1 delineates the proposed project site, which was used to
approximate the 2- and 100-year existing runoff.
The existing site runoff generally drains from northwest-to-southeast into the existing
alley along the eastern boundary of the site.
3. The project site does not receive notable runoff from contiguous off-site properties.
Maple Mixed Use
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III. DRAINAGE DESIGN CRITERIA
A. There are no optional provisions outside of the FCSCM proposed with Maple Mixed Use.
B. The overall stormwater management strategy employed with Maple Mixed Use 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. The first consideration taken in trying to
reduce the stormwater impacts of this development is the site selection itself. By choosing
an already developed site with public storm sewer currently in place, the burden is
significantly less than developing a vacant parcel absent of any infrastructure.
Maple Mixed Use aims to reduce runoff peaks, volumes and pollutant loads from
frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and 2-year
storm events) by implementing Low Impact Development (LID) strategies. Wherever
practical, runoff will be routed across landscaped areas or Bio-retention planters. These
LID practices reduce the overall amount of impervious area, while at the same time
Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA
techniques will be implemented, where practical, throughout the development, thereby
slowing runoff and increasing opportunities for infiltration.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release. The efforts taken in Step 1 will help to minimize excess runoff from
frequently occurring storm events; however, urban development of this intensity will still
have stormwater runoff leaving the site. The primary water quality treatment will occur in
the Bio-retention planters located in the second level courtyard.
Step 3 – Stabilize Drainageways. As stated in Section I.B.5, above, there are no major
drainageways in or near the subject site. While this step may not seem applicable to
Maple Mixed Use, the proposed project indirectly helps achieve stabilized drainageways
nonetheless. Once again, site selection has a positive effect on stream stabilization. By
developing an infill site with existing stormwater infrastructure, combined with LID and
MDCIA strategies, the likelihood of bed and bank erosion is reduced. Furthermore, this
project will pay one-time stormwater development fees, as well as ongoing monthly
stormwater utility fees, both of which help achieve Citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically
applies to industrial and commercial developments.
C. Development Criteria Reference and Constraints
1. The subject property is not part of any Overall Development Plan (ODP) drainage
study or similar “development/project” drainage master plan.
2. The site plan is constrained on two sides by public streets, as well as by existing
developments along the remaining two sides.
Maple Mixed Use
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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 Maple Mixed Use 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. The Rational Formula-based Federal Aviation Administration (FAA) procedure has
utilized for detention storage calculations.
4. Two separate design storms have been utilized to address distinct drainage scenarios.
The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year
recurrence interval. The second event considered is the “Major Storm,” which has a
100-year recurrence interval.
E. Hydraulic Criteria
1. The drainage facilities proposed with the Maple Mixed Use project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban
Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria
Manual.
2. As stated in Section I.C.1, above, the subject property is located in a City of
Fort Collins designated floodplain but an update to the modeling is underway
that will remove the lot from the floodplain.
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is adjacent to a City of Fort Collins
regulated floodplain. Discussions with City staff have indicated that more
accurate mapping information will likely remove all or part of the property from
the floodplain fringe. A floodplain modeling report is under review by City
staff.
2. Should additional data not have the anticipated effect on the floodplain
mapping, the building will be elevated or flood-proofed above the regulatory
floodplain as required by City Code. Additionally, all requirements set forth in
Chapter 10 of the City Municipal Code shall be met.
G. Modifications of Criteria
1. No modifications are requested at this time.
Maple Mixed Use
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H. Conformance with Water Quality Treatment Criteria
1. City Code requires that 100% of runoff from a project site receive some sort
of water quality treatment. This project proposes to provide water quality
treatment through the use of raised bio-retention basins (aka - planter boxes)
located in the upper level courtyard. These planter boxes are considered and
LID treatment method. Additionally, the landscape planter beds between
the building and the public sidewalks will be constructed as Landscape
Buffers with an engineered soil section and subdrain. These are also
considered an LID treatment technique. Due to the physical constraints
associated with an infill project of this nature and the prohibition of providing
water quality facilities within the public right-of-way, the majority of the
project site will receive formal water treatment. The areas that will not be
treated are small, narrow areas around the perimeter of the project that
cannot be captured. These areas tend to be narrow strips of concrete
flatwork that link the building entrances to the public sidewalks as well as
small planter beds between the building and public sidewalks or property
lines.
While these small areas will not receive formal water quality treatment, most
areas will still see some treatment as runoff is directed across through the
landscaped planter beds or across the landscaped parkways before reaching
the roadway curb and gutter.
I. Conformance with Low Impact Development (LID)
1. The project site will conform with the requirement to treat a minimum of 75%
of the project site using an LID technique. Please see Appendix C for LID
design information, table, and exhibit(s). As shown in the LID table provided
in the appendix, 80.5% of the proposed site impervious area will receive LID
treatment.
Maple Mixed Use
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IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objective of the Maple Mixed Use drainage design is to maintain existing
drainage patterns, while not adversely impacting adjacent properties.
2. No notable off-site runoff passes directly through the project site.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. Drainage for the project site has been analyzed using two (2) drainage sub-basins,
designated as sub-basins A & B. The drainage patterns anticipated for the basins are
further described below.
Sub-Basin A
Sub-basin A encompasses approximately 85%the total site area. This sub-basin is
comprised primarily of roof area and the on-site parking area. The majority of the
parking area will be located below the building and will not be exposed to
precipitation. Detention will be provided within an underground vault located under
the parking area.
Sub-Basin B
Sub-basin B encompasses approximately 15%the total site area. This sub-basin is
comprised primarily of landscaped area surrounding the building. Sub-basin B will
leave the site undetained. This basin will release at 0.12 cfs in the 2-yr event and at
0.54 cfs in the 100-year event.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. The existing impervious area on the site has been grandfathered due to the site
condition and the historic stormwater fees paid by the property owner. This
allows the runoff from existing impervious areas to be released undetained at
the historic 100-yr release rate.
2. The release rate for the undeveloped land (pre-development) was established
by calculating the 100-year peak runoff rate for the existing impervious areas
and adding the 2-year peak runoff rate of the undeveloped portions of the
project area. The total establishes the overall maximum allowable release rate,
3.73 cfs, from the project site. The allowable release rate of 3.73 cfs utilized
in the FAA procedure detention storage computations (Refer to Appendix B for
these calculations) and was established by subtracting the total undetained
release from Basin B of 0.54 cfs from the overall maximum allowable release
rate.
3. The FAA method was used to size the on-site detention volume for quantity
Maple Mixed Use
Page|9
detention. Calculations for this area, based on the characteristics of sub-basin
A and adjusted release rate, indicate a required detention volume of 685 cu.
ft. This does not include any volume for Water Quality Capture Volume
(WQCV) as WQ treatment is being provided in the bio-retention planters. There
is no-infiltration accounted for with this design.
4. The detention volume will be provided using surface ponding within the
parking area. 698 cu. ft. of volume is currently provided with a 100-yr water
surface elevation of 4989.32. This volume exceeds the 685 cu. ft. that are
required.
5. To the extent feasible, roof drain downspouts will discharge into the bio-
retention planters section. The exception to this are the small awnings located
over entrances, which will release into landscaped areas, as well as the
second level terrace located on the north side of the building, which will
release into the detention vault.
6. The emergency spill path will be from the surface detention area into the existing
alley, where flows will proceed along the historic path south along the alley and east
to the existing curb inlet.
Maple Mixed Use
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V. CONCLUSIONS
A. Compliance with Standards
1. The design elements comply without variation, and meet all LID requirements.
2. The drainage design proposed with Maple Mixed Use complies with the City of Fort
Collins Master Drainage Plan for the Old Town Basin.
3. There are no FEMA regulatory floodplains associated with the Maple Mixed Use
development. However the project is impacted by the Old Town Floodplain, which is
a City Regulated floodplain. All provisions within Chapter 10 of the City Municipal
Code shall be adhered to.
4. The drainage plan and stormwater management measures proposed with the Maple
Mixed Use project 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 potential damage
associated with its stormwater runoff. Maple Mixed Use will detain for the pervious
area converted to impervious areas to release at the 2-year existing rate during the
100-year storm.
2. The proposed Maple Mixed Use development will not impact the Master Drainage
Plan recommendations for the Old Town major drainage basin.
Maple Mixed Use
Page|11
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. 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.
3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
4. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Maple Mixed Use
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100 Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90
Gravel ……….…………………….….…………………………..……………………………….. 0.50 40
Roofs …….…….………………..……………….…………………………………………….. 0.95 90
Concrete 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
Concrete
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
EX1 28,498 0.65 0.05 0.04 0.27 0.04 0.00 0.25 0.61 0.61 0.76 52.6
TOTAL ONSITE 28,498 0.65 0.05 0.04 0.27 0.04 0.00 0.25 0.61 0.61 0.76 52.6
EXISTING 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
September 14, 2016
Overland Flow, Time of Concentration:
Project: Maple Mixed Use
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
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)
Rational Method Equation: Project: Maple Mixed Use
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
EX1 EX1 0.65 8.4 8.4 8.0 0.61 0.61 0.76 2.40 4.10 8.59 0.96 1.63 4.28
N/A
EX1
(Impervious) 0.36 5.0 1.00 9.95 3.54
N/A
EX1
(Undeveloped) 0.30 5.0 0.23 2.85 0.19
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)
EXISTING 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)
A. Reese
September 14, 2016
Q = C f ( C )( i )( A )
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C10 C100
2-yr Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
EX1 EX1 0.65 0.61 0.61 0.76 8.4 8.4 8.0 0.96 1.63 4.28
EXISTING RUNOFF SUMMARY TABLE
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Summary Table
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Maple Mixed Use
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese
Asphalt ……....……………...……….....…...……………….………………………………….0.95 . 100 Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90
Gravel ……….…………………….….…………………………..……………………………….0.50 . 40
Roofs …….…….………………..……………….…………………………………………….0..95 90
Concrete 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
Concrete
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
A 24,009 0.55 0.00 0.00 0.55 0.00 0.00 0.00 0.95 0.95 1.00 90.0
B 4,489 0.10 0.00 0.04 0.00 0.00 0.00 0.07 0.42 0.42 0.53 30.6
TOTAL ONSITE 28,498 0.65 0.00 0.00 0.55 0.00 0.00 0.00 0.80 0.80 1.00 75.8
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
Overland Flow, Time of Concentration:
Project: Maple Mixed Use
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: Maple Mixed Use
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
A A 0.55 5.0 5.0 5.0 0.95 0.95 1.00 2.85 4.87 9.95 1.49 2.55 5.48
B B 0.10 5.0 5.0 5.0 0.42 0.42 0.53 2.85 4.87 9.95 0.12 0.21 0.54
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)
A. Reese
September 14, 2016
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)
Q = C f ( C )( i )( A )
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C10 C100
2-yr Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
A A 0.55 0.95 0.95 1.00 5.0 5.0 5.0 1.49 2.55 5.48
B B 0.10 0.42 0.42 0.53 5.0 5.0 5.0 0.12 0.21 0.54
DEVELOPED RUNOFF SUMMARY TABLE
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Summary Table
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Detention
Facilities
APPENDIX B.1
STORM SEWERS
APPENDIX B.2
DETENTION FACILITIES
Maple Mixed Use
Fort Collins, Colorado
A. Reese Date: September 14, 2016
Pond No.: A
A
100-yr
1.00 WQCV 0 ft
3
Area (A)= 0.55 acres Quantity Detention 685 ft
3
Max Release Rate = 3.19 cfs Total Volume 685 ft
3
Total Volume 0.016 ac-ft
Time Time
Ft.Collins
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 9.95 5.5 1642 957 685
10 600 7.72 4.2 2548 1914 634
15 900 6.52 3.6 3227 2871 356
20 1200 5.60 3.1 3696 3828 -132
25 1500 4.98 2.7 4109 4785 -676
30 1800 4.52 2.5 4475 5742 -1267
35 2100 4.08 2.2 4712 6699 -1987
40 2400 3.74 2.1 4937 7656 -2719
45 2700 3.46 1.9 5138 8613 -3475
50 3000 3.23 1.8 5330 9570 -4241
55 3300 3.03 1.7 5499 10527 -5028
60 3600 2.86 1.6 5663 11484 -5821
65 3900 2.72 1.5 5834 12441 -6607
70 4200 2.59 1.4 5983 13398 -7415
75 4500 2.48 1.4 6138 14355 -8217
80 4800 2.38 1.3 6283 15312 -9029
85 5100 2.29 1.3 6423 16269 -9846
90 5400 2.21 1.2 6564 17226 -10662
95 5700 2.13 1.2 6678 18183 -11505
100 6000 2.06 1.1 6798 19140 -12342
105 6300 2.00 1.1 6930 20097 -13167
110 6600 1.94 1.1 7042 21054 -14012
115 6900 1.89 1.0 7173 22011 -14838
120 7200 1.84 1.0 7286 22968 -15682
125 7500 1.79 1.0 7384 23925 -16541
130 7800 1.75 1.0 7508 24882 -17375
135 8100 1.71 0.9 7618 25839 -18221
OUTLET RATING CURVE
Detention Orifice
Project: Maple Mixed Use
Date: September 14, 2016
By: A. Reese
100-YR ORIFICE RATING
Orifice Dia (in) 8.50
Orifice Area (sf) 0.3941
Orifice invert (ft) 0.00
Orifice Coefficient 0.65
Outlet
Orifice Area Stage release
(SF) (FT) (CFS)
0.3941 0.00 0.00
0.3941 0.25 1.03
0.3941 0.50 1.45
0.3941 0.75 1.78
0.3941 1.00 2.06
0.3941 1.25 2.30
0.3941 1.50 2.52
0.3941 1.75 2.72
0.3941 2.00 2.91
0.3941 2.25 3.08
0.3941 2.50 3.25
D:\Projects\574-007\Drainage\Detention\574-007_Orifice rating.xlsx
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
LID Conformance Report
Date: September 14, 2016
Project: Maple Mixed Use Project No. 574-007
Fort Collins, Colorado
Attn: Stormwater Staff
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Stormwater Staff:
This letter serves to document conformance of the above referenced project with City of Fort Collins Low
Impact Development (LID) requirements. In particular, the project is meeting Section 3.1 of the Fort
Collins Stormwater Amendments to the Urban Drainage and Flood Control District Criteria Manual,
including Section3.1 (a)(1) requiring that no less than 50% of any newly added impervious area be treated
using one or more LID techniques and Section 3.1(a)(2) requiring that no less than 25% of all new paving
use a permeable pavement technology that is considered an LID technique.
Section 3.1(a)(1)
The entire project site has an impervious area of 25,814 sf. This results in a minimum required LID
treatment area of 12,907 sf. The project is treating 20,423 sf of the project area using bio-retention
planters that will be located in the second floor courtyard. The project is treating an additional 2,517 sf of
additional area using Landscape Buffers that will have an engineered soil section to promote infiltration.
The total project area treated by LID techniques is 22,940 sf, which is 80.50% of the total project area.
Section 3.1(a)(2)
The project is not proposing any areas of exposed impervious paving for parking, removing the requirement
for permeable pavement to be used on this project.
An exhibit has been provided to illustrate the topics outlined. Please feel free to contact me if you have
any questions.
Sincerely,
Andrew Reese Nicholas W. Haws, PE
Project Engineer Project Manager.
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 8,740 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 291 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 11 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 194 sq ft
D) Actual Flat Surface Area AActual = 340 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 340 sq ft
F) Rain Garden Total Volume VT= 312 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
12" thick layer of Fort Collins Bioretention Sand Media over 6" thick layer of
pea gravel over 8" thick layer of CDOT No. 4 aggregate
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.2 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 291 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.39 in
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
Spetember 14, 2016
Maple Mixed Use
Courtyard Planters - East
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03_Planters-East.xlsm, RG 9/14/2016, 10:09 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
Spetember 14, 2016
Maple Mixed Use
Courtyard Planters - East
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.03_Planters-East.xlsm, RG 9/14/2016, 10:09 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 3,326 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 111 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 9 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 74 sq ft
D) Actual Flat Surface Area AActual = 153 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 153 sq ft
F) Rain Garden Total Volume VT= 115 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
12" thick layer of Fort Collins Bioretention Sand Media over 6" thick layer of
pea gravel over 8" thick layer of CDOT No. 4 aggregate
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.2 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 111 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.24 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
September 14, 2016
Maple Mixed Use
Courtyard Planters - North
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03_Planters-North.xlsm, RG 9/14/2016, 10:10 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
September 14, 2016
Maple Mixed Use
Courtyard Planters - North
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.03_Planters-North.xlsm, RG 9/14/2016, 10:10 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 8,000 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 267 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 10 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 178 sq ft
D) Actual Flat Surface Area AActual = 340 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 340 sq ft
F) Rain Garden Total Volume VT= 283 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
12" thick layer of Fort Collins Bioretention Sand Media over 6" thick layer of
pea gravel over 8" thick layer of CDOT No. 4 aggregate
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.2 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 267 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.37 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
September 14, 2016
Maple Mixed Use
Courtyard Planters - West
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03_Planters-West.xlsm, RG 9/14/2016, 10:10 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Andy Reese
Northern Engineering
September 14, 2016
Maple Mixed Use
Courtyard Planters - West
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.03_Planters-West.xlsm, RG 9/14/2016, 10:10 AM
APPENDIX D
EROSION CONTROL REPORT
Maple Mixed Use
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) has
been 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 and/or wattles 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 Sheet C001 of the Utility Plans. The
Final Utility Plans will also contain a full-size Erosion Control Plan 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 any existing Development Agreement(s) of record, as well as the Development
Agreement, to be recorded prior to issuance of the Development Construction Permit. Also,
the Site Contractor for this project may 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, before commencing any earth
disturbing 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 E
USDA SOILS REPORT
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Natural Area, Colorado
Resources
Conservation
Service
July 22, 2016
Preface
Soil surveys contain information that affects land use planning in survey areas. They
highlight soil limitations that affect various land uses and provide information about
the properties of the soils in the survey areas. Soil surveys are designed for many
different users, including farmers, ranchers, foresters, agronomists, urban planners,
community officials, engineers, developers, builders, and home buyers. Also,
conservationists, teachers, students, and specialists in recreation, waste disposal,
and pollution control can use the surveys to help them understand, protect, or enhance
the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil properties
that are used in making various land use or land treatment decisions. The information
is intended to help the land users identify and reduce the effects of soil limitations on
various land uses. The landowner or user is responsible for identifying and complying
with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some cases.
Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/portal/
nrcs/main/soils/health/) and certain conservation and engineering applications. For
more detailed information, contact your local USDA Service Center (http://
offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic
tank absorption fields. A high water table makes a soil poorly suited to basements or
underground installations.
The National Cooperative Soil Survey is a joint effort of the United States Department
of Agriculture and other Federal agencies, State agencies including the Agricultural
Experiment Stations, and local agencies. The Natural Resources Conservation
Service (NRCS) has leadership for the Federal part of the National Cooperative Soil
Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs
and activities on the basis of race, color, national origin, age, disability, and where
applicable, sex, marital status, familial status, parental status, religion, sexual
orientation, genetic information, political beliefs, reprisal, or because all or a part of an
individual's income is derived from any public assistance program. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative means
2
for communication of program information (Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400
Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272
(voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and
employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................7
Soil Map................................................................................................................8
Legend..................................................................................................................9
Map Unit Legend................................................................................................10
Map Unit Descriptions........................................................................................10
Larimer County Area, Colorado......................................................................12
81—Paoli fine sandy loam, 0 to 1 percent slopes.......................................12
References............................................................................................................14
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous areas
in a specific area. They include a description of the soils and miscellaneous areas and
their location on the landscape and tables that show soil properties and limitations
affecting various uses. Soil scientists observed the steepness, length, and shape of
the slopes; the general pattern of drainage; the kinds of crops and native plants; and
the kinds of bedrock. They observed and described many soil profiles. A soil profile is
the sequence of natural layers, or horizons, in a soil. The profile extends from the
surface down into the unconsolidated material in which the soil formed or from the
surface down to bedrock. The unconsolidated material is devoid of roots and other
living organisms and has not been changed by other biological activity.
Currently, soils are mapped according to the boundaries of major land resource areas
(MLRAs). MLRAs are geographically associated land resource units that share
common characteristics related to physiography, geology, climate, water resources,
soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically
consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that is
related to the geology, landforms, relief, climate, and natural vegetation of the area.
Each kind of soil and miscellaneous area is associated with a particular kind of
landform or with a segment of the landform. By observing the soils and miscellaneous
areas in the survey area and relating their position to specific segments of the
landform, a soil scientist develops a concept, or model, of how they were formed. Thus,
during mapping, this model enables the soil scientist to predict with a considerable
degree of accuracy the kind of soil or miscellaneous area at a specific location on the
landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented by
an understanding of the soil-vegetation-landscape relationship, are sufficient to verify
predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them to
identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character of
soil properties and the arrangement of horizons within the profile. After the soil
scientists classified and named the soils in the survey area, they compared the
5
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that have
similar use and management requirements. Each map unit is defined by a unique
combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components of
the map unit. The presence of minor components in a map unit in no way diminishes
the usefulness or accuracy of the data. The delineation of such landforms and
landform segments on the map provides sufficient information for the development of
resource plans. If intensive use of small areas is planned, onsite investigation is
needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape, and
experience of the soil scientist. Observations are made to test and refine the soil-
landscape model and predictions and to verify the classification of the soils at specific
locations. Once the soil-landscape model is refined, a significantly smaller number of
measurements of individual soil properties are made and recorded. These
measurements may include field measurements, such as those for color, depth to
bedrock, and texture, and laboratory measurements, such as those for content of
sand, silt, clay, salt, and other components. Properties of each soil typically vary from
one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists interpret
the data from these analyses and tests as well as the field-observed characteristics
and the soil properties to determine the expected behavior of the soils under different
uses. Interpretations for all of the soils are field tested through observation of the soils
in different uses and under different levels of management. Some interpretations are
modified to fit local conditions, and some new interpretations are developed to meet
local needs. Data are assembled from other sources, such as research information,
production records, and field experience of specialists. For example, data on crop
yields under defined levels of management are assembled from farm records and from
field or plot experiments on the same kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on such
variables as climate and biological activity. Soil conditions are predictable over long
periods of time, but they are not predictable from year to year. For example, soil
scientists can predict with a fairly high degree of accuracy that a given soil will have
a high water table within certain depths in most years, but they cannot predict that a
high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
identified each as a specific map unit. Aerial photographs show trees, buildings, fields,
roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
6
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of soil
map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
7
8
Custom Soil Resource Report
Soil Map
4493350 4493360 4493370 4493380 4493390 4493400
4493350 4493360 4493370 4493380 4493390 4493400
493020 493030 493040 493050 493060 493070 493080 493090 493100 493110
493020 493030 493040 493050 493060 493070 493080 493090 493100 493110
40° 35' 29'' N
105° 4' 57'' W
40° 35' 29'' N
105° 4' 53'' W
40° 35' 27'' N
105° 4' 57'' W
40° 35' 27'' N
105° 4' 53'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:453 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
81 Paoli fine sandy loam, 0 to 1
percent slopes
0.8 100.0%
Totals for Area of Interest 0.8 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the soils
or miscellaneous areas in the survey area. The map unit descriptions, along with the
maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the landscape,
however, the soils are natural phenomena, and they have the characteristic variability
of all natural phenomena. Thus, the range of some observed properties may extend
beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic
class rarely, if ever, can be mapped without including areas of other taxonomic
classes. Consequently, every map unit is made up of the soils or miscellaneous areas
for which it is named and some minor components that belong to taxonomic classes
other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They generally
are in small areas and could not be mapped separately because of the scale used.
Some small areas of strongly contrasting soils or miscellaneous areas are identified
by a special symbol on the maps. If included in the database for a given area, the
contrasting minor components are identified in the map unit descriptions along with
some characteristics of each. A few areas of minor components may not have been
observed, and consequently they are not mentioned in the descriptions, especially
where the pattern was so complex that it was impractical to make enough observations
to identify all the soils and miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the usefulness
or accuracy of the data. The objective of mapping is not to delineate pure taxonomic
classes but rather to separate the landscape into landforms or landform segments that
have similar use and management requirements. The delineation of such segments
on the map provides sufficient information for the development of resource plans. If
intensive use of small areas is planned, however, onsite investigation is needed to
define and locate the soils and miscellaneous areas.
Custom Soil Resource Report
10
An identifying symbol precedes the map unit name in the map unit descriptions. Each
description includes general facts about the unit and gives important soil properties
and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major horizons
that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity,
degree of erosion, and other characteristics that affect their use. On the basis of such
differences, a soil series is divided into soil phases. Most of the areas shown on the
detailed soil maps are phases of soil series. The name of a soil phase commonly
indicates a feature that affects use or management. For example, Alpha silt loam, 0
to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps. The
pattern and proportion of the soils or miscellaneous areas are somewhat similar in all
areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present or
anticipated uses of the map units in the survey area, it was not considered practical
or necessary to map the soils or miscellaneous areas separately. The pattern and
relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-
Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas that
could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion of
the soils or miscellaneous areas in a mapped area are not uniform. An area can be
made up of only one of the major soils or miscellaneous areas, or it can be made up
of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil material
and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
11
Larimer County Area, Colorado
81—Paoli fine sandy loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpxx
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Paoli and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Paoli
Setting
Landform: Stream terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 30 inches: fine sandy loam
H2 - 30 to 60 inches: fine sandy loam, sandy loam, loamy sand
H2 - 30 to 60 inches:
H2 - 30 to 60 inches:
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Very low
Capacity of the most limiting layer to transmit water (Ksat): High (2.00 to 6.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 15 percent
Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water storage in profile: Very high (about 16.5 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: A
Ecological site: Overflow (R067BY036CO)
Minor Components
Caruso
Percent of map unit: 6 percent
Custom Soil Resource Report
12
Table mountain
Percent of map unit: 6 percent
Fluvaquentic haplustolls
Percent of map unit: 3 percent
Landform: Terraces
Custom Soil Resource Report
13
References
American Association of State Highway and Transportation Officials (AASHTO). 2004.
Standard specifications for transportation materials and methods of sampling and
testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service
FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils
in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.
Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making
and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service,
U.S. Department of Agriculture Handbook 436. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://www.nrcs.usda.gov/wps/
portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
14
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States, the
Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
15
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Custom Soil Resource Report
9
140 8400 1.67 0.9 7715 26796 -19081
145 8700 1.63 0.9 7800 27753 -19953
150 9000 1.60 0.9 7920 28710 -20790
155 9300 1.57 0.9 8031 29667 -21636
160 9600 1.54 0.8 8131 30624 -22493
165 9900 1.51 0.8 8222 31581 -23359
170 10200 1.48 0.8 8303 32538 -24235
175 10500 1.45 0.8 8374 33495 -25121
180 10800 1.42 0.8 8435 34452 -26017
185 11100 1.40 0.8 8547 35409 -26862
190 11400 1.38 0.8 8653 36366 -27713
195 11700 1.36 0.7 8752 37323 -28571
200 12000 1.34 0.7 8844 38280 -29436
205 12300 1.32 0.7 8930 39237 -30307
210 12600 1.30 0.7 9009 40194 -31185
215 12900 1.28 0.7 9082 41151 -32069
220 13200 1.26 0.7 9148 42108 -32960
225 13500 1.24 0.7 9207 43065 -33858
230 13800 1.22 0.7 9260 44022 -34762
235 14100 1.21 0.7 9384 44979 -35595
240 14400 1.20 0.7 9504 45936 -36432
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
Detention Pond Calculation | FAA Method
Project:
Project Location:
Calculations By:
D:\Projects\574-007\Drainage\Detention\574-007_Detention.xlsm\
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A A No 0.95 0.95 1.00 25 1.00 1.4 1.4 0.9 83 2.11 2.90 0.5 83 2.11 2.18 0.6 5.0 5.0 5.0
B B No 0.95 0.95 1.00 15 1.67 0.9 0.9 0.6 0 N/A 0.00 0.0 0 N/A 0.00 0.0 5.0 5.0 5.0
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Design
Point
Basin
Overland Flow
A. Reese
September 14, 2016
GutterConcentration Flow Swale Flow Time of
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Tc-2-yr_&_100-yr
September 14, 2016
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\C-Values
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
EX1 EX1 No 0.25 0.25 0.31 25 2.9 5.6 5.6 5.2 0 0.0 0.00 0.0 117 0.2 0.69 2.8 8.4 8.4 8.0
EXISTING TIME OF CONCENTRATION COMPUTATIONS
Design
Point
Basin
Overland Flow
A. Reese
September 14, 2016
GutterConcentration Flow Swale Flow Time of
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Tc-2-yr_&_100-yr
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\C-Values