HomeMy WebLinkAboutRENNAT SUBDIVISION - FDP200006 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTMarch 18, 2020
FINAL DRAINAGE AND
EROSION CONTROL REPORT FOR
RENNAT SUBDIVISION
Fort Collins, Colorado
Prepared for:
JD Padilla
Post Modern Development
144 N. Mason St., Suite 4
Ft.Collins, CO 80524
Prepared by:
301 N. Howes, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1204-003
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.
March 18, 2020
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage and Erosion Control Report for
RENNAT SUBDIVISION
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your
review. This report accompanies the Final Plan submittal for the proposed Rennat Subdivision
development.
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, PhD, PE
Senior Project Engineer
Rennat Subdivision
Final Drainage and Erosion Control Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 2
C. Floodplain.......................................................................................................................................... 4
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description .................................................................................................................... 4
B. Sub-Basin Description ....................................................................................................................... 4
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 .............................................................................................................................. 7
F. Modifications of Criteria ................................................................................................................... 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 8
A. General Concept ............................................................................................................................... 8
B. Specific Details .................................................................................................................................. 9
V. CONCLUSIONS ...................................................................................................... 10
A. Compliance with Standards ............................................................................................................ 10
B. Drainage Concept ............................................................................................................................ 10
APPENDICES:
APPENDIX A.1–Hydrologic Computations and Supporting Documentation
APPENDIX A.2–Inlet Computations
APPENDIX A.3–Storm Line Computations
APPENDIX A.4–Riprap Computations
APPENDIX A.5–Street Capacity Computations
APPENDIX B–Water Quality and LID Computations and Information
APPENDIX C–Detention Computations, SWMM Output
APPENDIX D–Erosion Control Report
APPENDIX E–USDA Soils Information
Rennat Subdivision
Final Drainage and Erosion Control 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
Rennat Subdivision
Final Drainage and Erosion Control Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The project site is located in the east half of Section 7, Township 6 North, Range 68
West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
3. The project site is located just west of the intersection of Timberline Rd. and Rosen
Dr.
4. Existing residential developments, Fossil Creek at Linden Park, Crowne at Timberline
LP exist to the south of the site; Willow Springs exists to the north of the site.
5. No significant offsite flows enter the site from the north or south. There are existing
ridgelines near the northern and southern boundaries of the site. Timberline Road has
a high point just northeast of the site and acts as a barrier for any offsite flows from
the east. Historic flows convey west towards the existing Union Pacific Railroad
embankment and pass under the embankment through an existing large diameter
ductile iron pipe.
Rennat Subdivision
Final Drainage and Erosion Control Report 2
B. Description of Property
1. The overall property is 57.83 acres in size; however, the proposed development area
is roughly 33.5 acres in size.
Figure 1 – Aerial Photograph
2. The subject property is currently composed of undeveloped land. Existing ground
slopes are mild to moderate (i.e., 1 - 6±%) through the interior of the property.
Historic drainage patterns direct flows generally from north, south and east, and drain
via sheet flow collecting within an existing wet pond in the west central portion of the
site.
3. Historically, the majority of storm runoff discharges into the existing wet pond located
within the west central portion of the site. The proposed development will maintain
historic drainage patterns and will provide detention within the upper level of the
existing wet pond, as discussed further below.
4. The proposed detention pond will overdetain flows and release below historic rates
west to the existing culvert under the Union Pacific Railroad embankment. We
propose to restrict peak 100-year discharge from the proposed detention pond to no
greater than 5.0 cfs, as discussed below.
5. The proposed site design will include both LID and Extended Detention water quality
treatment prior to stormwater discharge from the site. Water quality treatment
methods are described in further detail below.
6. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey website:
PROJECT SITE
Rennat Subdivision
Final Drainage and Erosion Control Report 3
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx,
the site primarily consists of Fort Collins Loam, which falls into Hydrologic Soil Group
B, and Aquepts Loam, which falls into Hydrologic Soil Group D.
7. The proposed project site plan is composed of single family, and multi-family
residential development Associated site work, water, and sewer lines will be
constructed with the development. Onsite detention water quality treatment is
proposed and will consist of several features which are discussed in Section IV.
Figure 2– Proposed Site Plan
8. The proposed land use is single family and multi-family residential.
Rennat Subdivision
Final Drainage and Erosion Control Report 4
C. Floodplain
1. The project site is not encroached by any FEMA jurisdictional flood zone.
Additionally, the site is not encroached by any City designated flood zones, as shown
in Figure 3, below.
Figure 3 –Area Floodplain Mapping
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The project site lies within the Fossil Creek Master Drainage Basin. Onsite detention
is required for the runoff volume difference between the 100-year developed inflow
rate and the historic 2-year rate, which is specified in the master plan as 0.20 cfs per
acre.
2. We propose to overdetain flows and release below historic rates west to the existing
culvert under the Union Pacific Railroad embankment. We propose to restrict peak
100-year discharge from the proposed detention pond to no greater than 5.0 cfs,
which is below the allowable release rate per the Fossil Creek master drainage study
of 0.20 cfs per acre, which translates to 11.6 cfs for the 57.83 acre site. This
reduced release rate is proposed in order to mitigate any potential downstream
impacts
B. Sub-Basin Description
1. Historically, the majority of storm runoff discharges into the existing wet pond located
within the west central portion of the site. Depending on the antecedent water level
in the pond, historic flows would overflow from the pond and convey west under the
PROJECT SITE
Rennat Subdivision
Final Drainage and Erosion Control Report 5
adjacent Union Pacific railroad embankment through an existing ductile iron pipe with
an estimated diameter of 42-inches. From this pipe, the flow path for historic flows
conveys storm runoff through the Southridge Golf Course, located just west of the
railroad embankment and then into the existing storm system within the Greenridge at
Southridge Greens subdivision. Ultimately historic runoff conveys west into Fossil
Creek. The proposed development will maintain historic drainage patterns and will
provide detention within the upper level of the existing wet pond.
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 detention and LID treatment 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:
Rennat Subdivision
Final Drainage and Erosion Control Report 6
The proposed development will provide LID and water quality treatment; 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 3.4-1 of the FCSCM, serve as the source for all hydrologic computations
associated with the proposed development. Tabulated data contained in Table 3.4-1
has been utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing runoff
coefficients contained and frequency adjustment factors in Tables 3.2-2 and 3.2-3 of
the FCSCM.
Table 3.2-2 –Surface Type – Runoff Coefficients (City of Fort Collins Stormwater Criteria Manual,
Ref.1)
Rennat Subdivision
Final Drainage and Erosion Control Report 7
Table 3.2-3 –Frequency Adjustment Factors (City of Fort Collins Stormwater Criteria Manual,
Ref.1)
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 FEMA designated floodplain,
or within a City designated floodplain and floodway. 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.
Rennat Subdivision
Final Drainage and Erosion Control Report 8
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. LID and water quality treatment will be provided in the form of forebays, extended
detention, and an existing wet pond, as 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 1, 4c, 5a, 6a, 7a
Basins 1, 4c, 5a, 6a, and 7a consist of single family areas, right of way, and open
space. Drainage from these basins will be conveyed via street curb and gutter to
proposed storm sewer systems, which will direct developed runoff into Rain Garden 1.
This rain garden will pre-treat developed runoff prior to discharge into the existing
pond located within the central western portion of the site, which will provide
detention of developed runoff.
Basins 4a, 4b
Basins 4a, 4b consist of single family back of lots and open space. Drainage from
these basins will be conveyed via sheet flow and grass lined swale directly into the
existing pond, which will provide detention of developed runoff.
Basins 2, 5b, 6b, 7b, 12
Basins 2, 5, 6b, 7b, 12 consist of single family areas, right of way, and open space.
Drainage from these basins will be conveyed via street curb and gutter to proposed
storm sewer systems, which will direct developed runoff into Water Quality Pond 1.
This water quality pond will pre-treat developed runoff prior to discharge into the
existing pond located within the central western portion of the site, which will provide
detention of developed runoff.
Basins 3,8,9,13
Basins 3,8,9,13 consist of single family areas, right of way, and open space.
Drainage from these basins will be conveyed via street curb and gutter to proposed
storm sewer systems which will direct developed runoff into detention Pond 1. This
pond will provide attenuation prior to discharge into a main storm line running east-
west through the site and discharging into the existing wet pond. No water quality
treatment will be provided in this pond; the purpose of the pond is attenuation and
downsizing of the main storm line running through the site. Discharge from Pond 1
will be conveyed in the proposed storm sewer system, which will direct developed
runoff into Rain Garden 1. This rain garden will pre-treat developed runoff prior to
discharge into the existing pond located within the central western portion of the site.
Basin 10
Basin 10 consists of frontage of a small portion of single family area and right of way.
Drainage from the basin will flow in right of way to offsite right of way to the east.
Rennat Subdivision
Final Drainage and Erosion Control Report 9
Basin 11a
Basin 11a consists of single family fronts of lots, and right of way. Drainage from this
basin will be conveyed via street curb and gutter to a proposed sidewalk culvert. This
sidewalk culvert will direct developed runoff into Water Quality Pond 2, which will
pre-treat developed runoff prior to discharge into the existing pond located within the
central western portion of the site.
Basin 11b
Basin 11b consists of backs of lots of a single family area. Drainage from the basin
will sheet flow to offsite areas to the south, which is the historic drainage pattern. We
will be reducing runoff area, and we will maintain the existing sheet flow character of
runoff from this area. Thus, we propose no adverse impact to offsite properties.
Basin OS1
Basin OS1 consists of a small portion of adjacent and right of way area that will drain
into the project site. Drainage from the basin will be conveyed via proposed curb and
the proposed storm sewer system, which will direct developed runoff into Rain Garden
1.
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. Standard water quality treatment in the form of Extended Detention is being
provided for the overall proposed development within the Water Quality Ponds
1 and 2. We have computed required extended detention volume based on
the standard water quality treatment for 50% of site runoff. Please see Water
Quality Capture Volume (Extended Detention) computations provided in
Appendix B.
2. LID treatment is being provided within Rain Garden 1, which will provide in
excess of the required LID treatment of 50% of site runoff. Please see Water
Rain Garden computations provided in Appendix B.
3. In addition to the LID treatment via Rain Garden 1, we are providing a grass
lined swale to further enhance water quality prior to discharge of developed
runoff into the existing pond.
4. The overall site drains into the existing wet Pond. The existing pond has a
permanent water surface and will provide detention above the this water
surface. Existing established wetland vegetation and the permanent water
surface will greatly enhance water quality for runoff discharging from the site.
Rain Garden 1, Water Quality Pond 1, and Water Quality Pond 2 will be
provided for pre-treatment for the majority of developed runoff prior to entry to
the existing pond.
Rennat Subdivision
Final Drainage and Erosion Control Report 10
5. Please see Table 1, below, for a detention summary.
TABLE 1 – Detention Summary
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
West Vine Basin Master Plan.
3. The drainage plan and stormwater management measures proposed with the
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 providing detention and water
quality mitigation features.
2. The drainage concept for the proposed development is consistent with requirements
for the West Vine Basin Master Plan.
Pond ID
100-Yr.
Detention Vol.
(Ac-Ft)
Total Req'd Vol.
(Ac-Ft)
Peak Release
(cfs)
Pond 1 0.81 0.81 10.10
Existing Wet Pond 10.26 10.26 4.20
Rennat Subdivision
Final Drainage and Erosion Control Report 11
References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, December 2018.
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
(https://websoilsurvey.sc.egov.usda.gov/App/ Data upload February 2019)
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.1
Hydrologic Computations and Supporting Documentation
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: 1204-003
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…………………………...………………..…………………………………………….. 0.50 40%
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.
1 188833 4.34 1.04 0.22 0.52 0.00 2.56 0.54 0.54 0.67 39%
2 144846 3.33 0.73 0.17 0.40 0.00 2.03 0.52 0.52 0.65 37%
3 188231 4.32 0.47 0.01 0.03 0.00 3.81 0.33 0.33 0.42 12%
4 1041680 23.91 0.00 1.20 2.87 0.00 19.85 0.37 0.37 0.46 15%
5 67037 1.54 0.49 0.08 0.18 0.00 0.78 0.59 0.59 0.74 47%
6a 31730 0.73 0.24 0.04 0.09 0.00 0.36 0.60 0.60 0.75 48%
6b 98339 2.26 0.52 0.11 0.27 0.00 1.35 0.53 0.53 0.66 38%
7a 48046 1.10 0.28 0.06 0.13 0.00 0.64 0.54 0.54 0.68 40%
7b 166889 3.83 0.92 0.19 0.46 0.00 2.26 0.54 0.54 0.67 39%
Overland Flow, Time of Concentration:
Project: 1204-003
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: 1204-003
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1 1 4.34 14 14 14 0.54 0.54 0.67 1.92 3.29 6.71 4.47 7.66 19.53
2 2 3.33 13 13 13 0.52 0.52 0.65 2.02 3.45 7.04 3.50 5.99 15.30
3 3 4.32 14 14 14 0.33 0.33 0.42 1.95 3.34 6.82 2.80 4.80 12.24
4 4 23.91 11 11 11 0.37 0.37 0.46 2.13 3.63 7.42 18.80 32.03 81.84
5 5 1.54 15 15 15 0.59 0.59 0.74 1.90 3.24 6.62 1.73 2.96 7.55
6a 6a 0.73 11 11 11 0.60 0.60 0.75 2.13 3.63 7.42 0.93 1.59 4.05
6b 6b 2.26 13 13 13 0.53 0.53 0.66 1.98 3.39 6.92 2.37 4.06 10.35
7a 7a 1.10 13 13 13 0.54 0.54 0.68 2.02 3.45 7.04 1.21 2.07 5.28
7b 7b 3.83 14 14 14 0.54 0.54 0.67 1.92 3.29 6.71 3.95 6.77 17.26
8 8 1.72 12 12 12 0.54 0.54 0.67 2.05 3.50 7.16 1.89 3.23 8.27
9 9 1.57 15 15 15 0.57 0.57 0.71 1.90 3.24 6.62 1.68 2.87 7.32
10 10 0.09 6 6 6 0.63 0.63 0.79 2.67 4.56 9.31 0.14 0.25 0.63
11a 11a 2.23 13 13 13 0.60 0.60 0.75 1.98 3.39 6.92 2.65 4.53 11.57
11b 11b 0.95 10 10 10 0.37 0.37 0.46 2.21 3.78 7.72 0.77 1.32 3.37
12 12 3.05 16 16 16 0.52 0.52 0.65 1.84 3.14 6.41 2.94 5.00 12.79
13 13 2.51 13 13 13 0.70 0.70 0.87 1.98 3.39 6.92 3.46 5.92 15.11
OS1 OS1 0.34 13 13 13 0.71 0.71 0.88 1.98 3.39 6.92 0.48 0.82 2.10
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
February 4, 2020
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
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.2 Runoff Coefficients
Page 4
3.2 Runoff Coefficients
Runoff coefficients used for the Rational Method are determined based on either overall land use or
surface type across the drainage area. For Overall Drainage Plan (ODP) submittals, when surface types
may not yet be known, land use shall be used to estimate flow rates and volumes. Table 3.2-1 lists the
runoff coefficients for common types of land uses in the City.
Table 3.2-1. Zoning Classification - Runoff Coefficients
Land Use Runoff Coefficient (C)
Residential
Urban Estate 0.30
Low Density 0.55
Medium Density 0.65
High Density 0.85
Commercial
Commercial 0.85
Industrial 0.95
Undeveloped
Open Lands, Transition 0.20
Greenbelts, Agriculture 0.20
Reference: For further guidance regarding zoning classifications, refer to the Land Use
Code, Article 4.
For a Project Development Plan (PDP) or Final Plan (FP) submittals, runoff coefficients must be based on
the proposed land surface types. Since the actual runoff coefficients may be different from those
specified in Table 3.2-1, Table 3.2-2 lists coefficients for the specific types of land surfaces.
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.2 Runoff Coefficients
Page 5
Table 3.2-2. Surface Type - Runoff Coefficients
Surface Type Runoff Coefficients
Hardscape or Hard Surface
Asphalt, Concrete 0.95
Rooftop 0.95
Recycled Asphalt 0.80
Gravel 0.50
Pavers 0.50
Landscape or Pervious Surface
Lawns, Sandy Soil, Flat Slope < 2% 0.10
Lawns, Sandy Soil, Avg Slope 2-7% 0.15
Lawns, Sandy Soil, Steep Slope >7% 0.20
Lawns, Clayey Soil, Flat Slope < 2% 0.20
Lawns, Clayey Soil, Avg Slope 2-7% 0.25
Lawns, Clayey Soil, Steep Slope >7% 0.35
3.2.1 Composite Runoff Coefficients
Drainage sub-basins are frequently composed of land that has multiple surface types or zoning
classifications. In such cases a composite runoff coefficient must be calculated for any given drainage
sub-basin.
The composite runoff coefficient is obtained using the following formula:
( )
t
n
i
i i
A
C xA
C
∑
= = 1 Equation 5-2
Where: C = Composite Runoff Coefficient
Ci = Runoff Coefficient for Specific Area (Ai), dimensionless
Ai = Area of Surface with Runoff Coefficient of Ci, acres or square feet
n = Number of different surfaces to be considered
At = Total Area over which C is applicable, acres or square feet
3.2.2 Runoff Coefficient Frequency Adjustment Factor
The runoff coefficients provided in Table 3.2-1 and Table 3.2-2 are appropriate for use with the 2-year
storm event. For any analysis of storms with higher intensities, an adjustment of the runoff coefficient is
required due to the lessening amount of infiltration, depression retention, evapotranspiration and other
losses that have a proportionally smaller effect on high-intensity storm runoff. This adjustment is
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.3 Time of Concentration
Page 6
applied to the composite runoff coefficient. These frequency adjustment factors, Cf, are found in Table
3.2-3.
Table 3.2-3. Frequency Adjustment Factors
Storm Return Period
(years)
Frequency Adjustment
Factor (Cf)
2, 5, 10 1.00
25 1.10
50 1.20
100 1.25
3.3 Time of Concentration
3.3.1 Overall Equation
The next step to approximate runoff using the Rational Method is to estimate the Time of
Concentration, Tc, or the time for water to flow from the most remote part of the drainage sub-basin to
the design point under consideration.
The Time of Concentration is represented by the following equation:
𝐓𝐓𝐜𝐜 = 𝐓𝐓
𝐢𝐢 + 𝐓𝐓𝐭𝐭
Equation 5-3
Where: Tc = Total Time of Concentration, minutes
Ti = Initial or Overland Flow Time of Concentration, minutes
Tt = Channelized Flow in Swale, Gutter or Pipe, minutes
3.3.2 Overland Flow Time
Overland flow, Ti, can be determined by the following equation:
𝐓𝐓𝐢𝐢 =
𝟏𝟏.𝟖𝟖𝟖𝟖(𝟏𝟏.𝟏𝟏−𝐂𝐂𝐂𝐂𝐂𝐂𝐟𝐟)√𝐋𝐋
√𝐒𝐒
𝟑𝟑 Equation 3.3-2
Where: C = Runoff Coefficient, dimensionless
Cf = Frequency Adjustment Factor, dimensionless
L = Length of Overland Flow, feet
S = Slope, percent
CXCF
PRODUCT OF CXCF
CANNOT EXCEED THE
VALUE OF 1
OVERLAND FLOW LENGTH
L=200’ MAX IN DEVELOPED AREAS
L=500’ MAX IN UNDEVELOPED
AREAS
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 7
3.3.3 Channelized Flow Time
Travel time in a swale, gutter or storm pipe is considered “channelized” or “concentrated” flow and can
be estimated using the Manning’s Equation:
𝐕𝐕 =
𝟏𝟏.𝟒𝟒𝟒𝟒
𝐧𝐧
𝐑𝐑𝟐𝟐/𝟑𝟑
𝐒𝐒𝟏𝟏/𝟐𝟐
Equation 5-4
Where: V = Velocity, feet/second
n = Roughness Coefficient, dimensionless
R = Hydraulic Radius, feet (Hydraulic Radius = area / wetted perimeter, feet)
S = Longitudinal Slope, feet/feet
And:
𝐓𝐓𝐭𝐭 =
𝐋𝐋
𝐕𝐕𝐂𝐂𝐕𝐕𝐕𝐕
Equation 5-5
3.3.4 Total Time of Concentration
A minimum Tc of 5 minutes is required. The maximum Tc
allowed for the most upstream design point shall be
calculated using the following equation:
𝐓𝐓𝐜𝐜 =
𝐋𝐋
𝟏𝟏𝟖𝟖𝐕𝐕
+ 𝟏𝟏𝐕𝐕 Equation 3.3-5
The Total Time of Concentration, Tc, is the lesser of the
values of Tc calculated using Tc = Ti + Tt or the equation
listed above.
3.4 Intensity-Duration-Frequency Curves for Rational Method
The two-hour rainfall Intensity-Duration-Frequency curves for use with the Rational Method is provided
in Table 3.4-1 and Figure 3.4-1.
TC
• A MINIMUM TC OF 5
MINUTES IS REQUIRED IN
ALL CASES.
• A MAXIMUM TC OF 5
MINUTES IS TYPICAL FOR
SMALLER, URBAN PROJECTS.
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 8
Table 3.4-1. IDF Table for Rational Method
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
5 2.85 4.87 9.95
39 1.09 1.86 3.8
6 2.67 4.56 9.31
40 1.07 1.83 3.74
7 2.52 4.31 8.80
41 1.05 1.80 3.68
8 2.40 4.10 8.38
42 1.04 1.77 3.62
9 2.30 3.93 8.03
43 1.02 1.74 3.56
10 2.21 3.78 7.72
44 1.01 1.72 3.51
11 2.13 3.63 7.42
45 0.99 1.69 3.46
12 2.05 3.50 7.16
46 0.98 1.67 3.41
13 1.98 3.39 6.92
47 0.96 1.64 3.36
14 1.92 3.29 6.71
48 0.95 1.62 3.31
15 1.87 3.19 6.52
49 0.94 1.6 3.27
16 1.81 3.08 6.30
50 0.92 1.58 3.23
17 1.75 2.99 6.10
51 0.91 1.56 3.18
18 1.70 2.90 5.92
52 0.9 1.54 3.14
19 1.65 2.82 5.75
53 0.89 1.52 3.10
20 1.61 2.74 5.60
54 0.88 1.50 3.07
21 1.56 2.67 5.46
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 9
Figure 3.4-1. Rainfall IDF Curve – Fort Collins
APPENDIX A.2
Inlet Computations
Project: 1204-003
By: ATC
Date: 2/10/2020
Inlet Inlet Inlet Inlet Design Design
ID Size Type Condition Storm Flow Inlet Capacity
(CFS) (CFS)
1-2 Single Combination On-Grade 2-Yr 1.30 1.30
1-3 Single Combination On-Grade 2-Yr 1.30 1.30
1-4 Single Combination On-Grade 2-Yr 1.30 1.30
1-5 Single Combination On-Grade 2-Yr 1.30 1.30
1-6 Single Combination On-Grade 2-Yr 1.30 1.30
1-7 Single Combination On-Grade 2-Yr 1.30 1.30
2-2 Single Area Sump 2-Yr 0.20 4.80
2-3 Single Combination Sump 2-Yr 3.50 3.50
3-2 Single Combination Sump 2-Yr 2.75 3.50
3-3 Single Combination Sump 2-Yr 2.75 3.50
7-3 Triple Combination Sump 100-Yr 19.50 19.50
INLET CAPACITY CALCULATION SUMMARY TABLE
Project:
Inlet ID:
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL
= 2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening) No = 1 1
Length of a Single Unit Inlet (Grate or Curb Opening) Lo
= 3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo
= 1.73 1.73 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf
-G = 0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf
-C = 0.10 0.10
Street Hydraulics: OK - Q < maximum allowable from sheet 'Q-Allow' MINOR MAJOR
Total Inlet Interception Capacity Q = 1.3 2.1 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.9 2.9 cfs
Capture Percentage = Qa/Q
o = C% = 60 42 %
INLET ON A CONTINUOUS GRADE
1204-003
Single On Grade Combination Inlet
CDOT/Denver 13 Combination
UD Inlet 3.1-Combo-Single OG.xlsm, Inlet On Grade 2/10/2020, 3:11 PM
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 9.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = 3.00 3.00 feet
Width of a Unit Grate Wo = 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat = 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw (C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 3.6 7.1 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = 3.0 5.0 cfs
INLET IN A SUMP OR SAG LOCATION
1204-003
Single Combination Inlet - Sump Condition
CDOT/Denver 13 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
UD Inlet 3.1-Combo-Single SUMP.xlsm, Inlet In Sump 2/10/2020, 3:14 PM
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 3 3
Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 9.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = 3.00 3.00 feet
Width of a Unit Grate Wo = 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat = 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw (C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 6.4 19.5 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = 3.0 5.0 cfs
INLET IN A SUMP OR SAG LOCATION
1204-003
Triple Combination Inlet - Sump Condition
CDOT/Denver 13 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
UD Inlet 3.1-Combo-Triple SUMP.xlsm, Inlet In Sump 2/10/2020, 3:20 PM
APPENDIX A.3
Storm Line Computations
APPENDIX A.4
Riprap Computations
Circular
D or Da,
Pipe
Diameter
(ft)
H or Ha,
Culvert
Height
(ft)
W,
Culvert
Width
(ft)
Yt/D Q/D
1.5
Q/D
2.5 Y
t/H Q/WH
0.5
Storm Line 1 18.10 2.00 0.80 0.40 6.40 3.20 N/A N/A 4.45 3.20 3.62 11.24 Type L 12.00 10.00 1.5
Storm Line 2 4.20 1.25 0.50 0.40 3.01 2.40 N/A N/A 5.25 2.40 0.84 2.26 Type L 5.00 5.00 1.5
Storm Line 3 5.50 1.25 0.50 0.40 3.94 3.15 N/A N/A 4.50 3.15 1.10 4.28 Type L 5.00 5.00 1.5
Storm Line 4 4.70 1.00 0.40 0.40 4.70 4.70 N/A N/A 2.95 4.70 0.94 3.98 Type L 5.00 5.00 1.5
Storm Line 5 5.20 1.00 0.40 0.40 5.20 5.20 N/A N/A 1.80 5.20 1.04 2.88 Type M 5.00 5.00 1.5
Storm Line 6 19.50 2.00 0.80 0.40 6.89 3.45 N/A N/A 4.20 3.45 3.90 12.08 Type L 14.00 12.00 1.5
Storm Line 7 4.20 2.00 0.80 0.40 1.48 0.74 N/A N/A 6.70 0.74 0.84 -6.37 Type L 8.00 8.00 1.5
Project: 1204-003
Urban Drainage
pg MD-107
L=
1/(2tanq)*
[At/Yt)-W]
(ft)
Culvert Parameters
At=Q/V (ft)
INPUT
CALCULATIONS FOR RIPRAP PROTECTION AT PIPE OUTLETS
Circular
Pipe
(Figure MD-21)
Rectangular
Pipe
(Figure MD-22) Spec
Width
of
Riprap
(ft)
2*d50,
Depth
of
Riprap
(ft)
for L/2
Froude
Parameter
Q/D
2.5
Max 6.0
or
Q/WH
APPENDIX A.5
Street Capacity Computations
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 6.3 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012
Height of Curb at Gutter Flow Line HCURB = 4.70 inches
Distance from Curb Face to Street Crown TCROWN = 18.0 ft
Gutter Width W = 1.17 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.018 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 4.7 10.7 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 12.2 144.3 cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
1204-003
Local Residential Street Capacity - DP 2
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
DP2.xlsm, Q-Allow 2/12/2020, 11:18 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 6.3 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012
Height of Curb at Gutter Flow Line HCURB = 4.70 inches
Distance from Curb Face to Street Crown TCROWN = 18.0 ft
Gutter Width W = 1.17 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.032 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 4.7 10.7 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 16.3 121.5 cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
1204-003
Local Residential Street Capacity - DP 3
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
DP3.xlsm, Q-Allow 2/12/2020, 11:21 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 6.3 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012
Height of Curb at Gutter Flow Line HCURB = 4.70 inches
Distance from Curb Face to Street Crown TCROWN = 18.0 ft
Gutter Width W = 1.17 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.009 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 4.7 10.7 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 8.7 112.5 cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
1204-003
Local Residential Street Capacity - DP 5
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
DP5.xlsm, Q-Allow 2/12/2020, 11:20 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 6.3 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012
Height of Curb at Gutter Flow Line HCURB = 4.70 inches
Distance from Curb Face to Street Crown TCROWN = 18.0 ft
Gutter Width W = 1.17 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.007 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 4.7 10.7 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 7.6 99.2 cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
1204-003
Local Residential Street Capacity - DP 7B
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
DP7B.xlsm, Q-Allow 2/12/2020, 11:22 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 6.3 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.012
Height of Curb at Gutter Flow Line HCURB = 4.70 inches
Distance from Curb Face to Street Crown TCROWN = 18.0 ft
Gutter Width W = 1.17 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.098 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.007 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.012
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 18.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 4.7 10.7 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 7.6 99.2 cfs
Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
1204-003
Local Residential Street Capacity - DP 11A
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak'
DP11A.xlsm, Q-Allow 2/12/2020, 11:23 AM
APPENDIX B
Water Quality and LID Computations and Information
12" W
12" W
X
SS
VAULT
ELEC
X
X
X
X
X
IRR
WM WM WM WM
WM
WM
WM WM
WM
WM
WM
WM WM
WM WM
WM
WM
WM
WM WM
WM WM WM
WM
WM
WM WM
WM WM WM WM
WM
WM
WM
WM
WM
WM WM
WM
WM
WM
WM
WM
UD
UD
UD
UD
UD
UD UD UD UD UD UD UD
UD
UD
UD
UD
UD UD UD
UD UD
UD
V
AULT
TELE
T
VAULT
TELE
Project Number: Project: Rennat
Project Location:
Calculations By: Date: 2/12/2020
Sq. Ft. Acres
LID 764,154 17.54 36%
2, 3, 4c, 5a, 6a, 6b, 7a, 8,
9, 13, OS1
Rain Garden 1 8,611 299,955
Total 764,154 17.54 299,955
2,534,070 ft
2
599,801 ft
2
299,900 ft
2
299,955 ft
2
50.0%
Weighted
%
Impervious
1204-003
Fort Collins, Colorado
M. Ruebel
LID Summary
50% Required Minimum Area to be Treated
Total Treated Impervious Area
Percent Impervious Treated by LID
LID Summary per LID Structure
LID Site Summary
Total Site Area
Total Site Impervious Area
Impervious
Area (ft
2
)
LID ID Subbasin ID Treatment Type
Volume per
UD-BMP (ft
3
)
Area
103-042 Thornburg-Hamilton 3rd Filing
1204-003
Fort Collins, CO
M. Ruebel Date: 2/11/2020
Forbay
Total Undetained
Area Contributing
to Pond
Percent Impervious WQCV Forebay
Forebay
Depth
Forebay
Area
Forebay
Release
(2%)
(ac) (%) (ac-ft) 3% of WQCV (ft) (ft
2
) (cfs)
Forebay 1 (WQ Pond 1) 9.74 36.50% 0.138318 0.004149555 1.5 121 0.7
Forebay 2 (WQ Pond 2) 2.23 48.00% 0.037327 0.00111981 0.5 98 0.23
Urban Drainage Equation 3-1
Urban Drainage Equation 3-3
Urban Drainage Table 3-2
Project Number:
Project Location:
Calculations By:
Forebay Calculations
( )
( )
( )
a ( hours )
a hours
a hours
A
WQCV
V
WQCV a I I I
1 . 0 40
0 . 9 24
0 . 8 12
12
0 . 91 3 1 . 19 2 0 . 78
=
=
=
=
= − +
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 36.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.360
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.14 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 764,154 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 8,611 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 = 12.00 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 5502 sq ft
D) Actual Flat Surface Area AActual = 10208 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 14283 sq ft
F) Rain Garden Total Volume VT= 12,246 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
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 = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
MCR
Northern Engineering
February 12, 2020
Rennat
Rain Garden 1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
Rain Garden 1.xlsm, RG 2/11/2020, 9:28 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?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes: See approved landscaping plans for seed mixtures and plantings.
Design Procedure Form: Rain Garden (RG)
MCR
Northern Engineering
February 12, 2020
Rennat
Rain Garden 1
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
Rain Garden 1.xlsm, RG 2/11/2020, 9:28 AM
WATER QUALITY POND DESIGN CALCULATIONS
Water Quality Pond 1
Project: 1204-003
By: MCR
Date:02/12/2020
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA = 9.740 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 36.50 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.3650 <-- CALCULATED
WQCV (watershed inches) = 0.170 <-- CALCULATED from Figure EDB-2
WQCV (ac-ft) = 0.166 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
WQ Depth (ft) = 1.590 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) = 0.537 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 7/8 <-- INPUT from Figure 5
number of holes = 4 <-- INPUT from Figure 5
t (in) = 1/4 <-- INPUT from Figure 5
number of rows = 1 <-- CALCULATED from WQ Depth and row spacing
*Basins 4d, 5b, 6c, 7b, 12
WATER QUALITY POND DESIGN CALCULATIONS
Water Quality Pond 2
Project: 1204-003
By: MCR
Date:02/12/2020
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA = 2.230 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 48.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.4800 <-- CALCULATED
WQCV (watershed inches) = 0.201 <-- CALCULATED from Figure EDB-2
WQCV (ac-ft) = 0.045 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
WQ Depth (ft) = 1.200 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) = 0.176 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/2 <-- INPUT from Figure 5
number of holes = 3 <-- INPUT from Figure 5
t (in) = 1/4 <-- INPUT from Figure 5
number of rows = 1 <-- CALCULATED from WQ Depth and row spacing
*Basins 11a
Area Inlet Performance Curve:
Rennat - Outlet 4-3
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: CDOT Type C Close Mesh Grate
Shape Rectangular
Length of Grate (ft): 3.33
Width of Grate (ft): 2.75
Open Area of Grate (ft
2
): 7.54
Flowline Elevation (ft): 4941.000
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 4941.00 0.00 0.00 0.00
0.10 4941.10 0.58 6.41 0.58
0.20 4941.20 1.63 9.06 1.63
0.30 4941.30 3.00 11.10 3.00
0.40 4941.40 4.61 12.81 4.61
0.50 4941.500 6.45 14.33 6.45
0.60 4941.60 8.48 15.69 8.48 Q2
0.70 4941.70 10.68 16.95 10.68
0.80 4941.80 13.05 18.12 13.05
0.90 4941.90 15.57 19.22 15.57
1.00 4942.000 18.24 20.26 18.24
2-Year Design Flow = 8.1 cfs
0.00
5.00
10.00
15.00
20.00
25.00
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Series1 Series2
Q = 3 . 0 P H 1 . 5
APPENDIX C
Detention Computations, SWMM Output
Project: 1204-003
By: ATC
Date: 2/5/20
Pond ID
100-Yr.
Detention Vol.
(Ac-Ft)
Total Req'd Vol.
(Ac-Ft)
100-Yr.
Detention WSEL
(Ft)
Peak Release
(cfs)
Pond 1 0.81 0.81 4952.80 10.10
Existing Wet Pond 10.26 10.26 4943.60 4.20
POND SUMMARY TABLE
Pond Stage-Storage Curve
Pond: 1
Project: 1204-003
By: ATC
Date: 2/7/20
Stage
(FT)
Contour Area
(SF)
Volume
(CU.FT.)
Volume
(AC-FT)
4948.00 99.84 0.00 0.00
4948.20 500.65 54.94 0.00
4948.40 1194.29 219.48 0.01
4948.60 2071.72 542.08 0.01
4948.80 3178.46 1063.17 0.02
4949.00 4468.77 1824.24 0.04
4949.20 4925.92 2763.33 0.06
4949.40 5352.70 3790.90 0.09
4949.60 5787.68 4904.65 0.11
4949.80 6230.81 6106.23 0.14
4950.00 6682.08 7397.26 0.17
4950.20 7141.46 8779.36 0.20
4950.40 7608.18 10254.08 0.24
4950.60 8079.07 11822.57 0.27
4950.80 8553.77 13485.63 0.31
4951.00 9032.28 15244.01 0.35
4951.20 9514.61 17098.49 0.39
4951.40 10000.74 19049.83 0.44
4951.60 10490.68 21098.77 0.48
4951.80 10984.44 23246.10 0.53
4952.00 11482.00 25492.56 0.59
4952.20 11983.38 27838.92 0.64
4952.40 12495.20 30286.60 0.70
4952.60 13174.40 32853.26 0.75
4952.80 14345.38 35604.40 0.82
4953.00 223.42 36695.01 0.84
4953.20 93.43 36725.76 0.84
Pond Stage-Storage Curve
Pond: Existing Natural Pond
Project: 1204-003
By: ATC
Date: 2/7/20
Stage
(FT)
Contour Area
(SF)
Volume
(CU.FT.)
Volume
(AC-FT)
4,941.20 N/A 0 0.00
4,941.40 32,687.38 26157.15 0.60
4,941.60 33,096.37 52814.05 1.21
4,941.80 34,586.87 81045.85 1.86
4,942.00 36,424.72 111213.44 2.55
4,942.20 38,217.84 143262.18 3.29
4,942.40 40,899.35 178082.98 4.09
4,942.60 43,956.71 216054.51 4.96
4,942.80 47,251.17 257413.87 5.91
4,943.00 50,612.48 302231.03 6.94
4,943.20 53,779.99 350312.89 8.04
4,943.40 56,679.54 401392.08 9.21
4,943.60 59,098.60 454989.44 10.45
4,943.80 61,115.60 510701.56 11.72
4,944.00 63,124.96 568523.36 13.05
4,944.20 65,040.08 628379.69 14.43
4,944.40 66,728.78 690074.43 15.84
4,944.60 68,281.11 753498.43 17.30
4,944.80 69,844.40 818676.11 18.79
4,945.00 142,286.96 950047.75 21.81
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.012)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ 01/01/2000 00:00:00
Ending Date .............. 01/06/2000 01:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:15:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 30.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 18.719 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 6.957 1.364
Surface Runoff ........... 11.676 2.289
Final Storage ............ 0.148 0.029
Continuity Error (%) ..... -0.331
SWMM 5 Page 1
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 11.676 3.805
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 11.675 3.804
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 0.000 0.000
Final Stored Volume ...... 0.000 0.000
Continuity Error (%) ..... 0.014
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 29.00 sec
Average Time Step : 30.00 sec
Maximum Time Step : 30.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
Percent Not Converging : 0.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
SM1 3.67 0.00 0.00 1.42 2.24 2.88 163.31 0.610
SM2 3.67 0.00 0.00 1.27 2.38 0.68 41.80 0.649
SWMM 5 Page 2
OS2 3.67 0.00 0.00 0.94 2.71 0.25 20.25 0.739
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Depth Depth HGL Occurrence Max Depth
Node Type Feet Feet Feet days hr:min Feet
---------------------------------------------------------------------------------
outfall OUTFALL 0.00 0.00 96.00 0 00:00 0.00
ExistPondingArea STORAGE 1.51 4.57 101.57 0 03:27 4.57
Pond1 STORAGE 0.09 3.77 106.77 0 01:28 3.76
PondOS2 STORAGE 0.78 6.92 110.92 0 02:15 6.92
*******************
Node Inflow Summary
*******************
-------------------------------------------------------------------------------------------------
Maximum Maximum Lateral Total Flow
Lateral Total Time of Max Inflow Inflow Balance
Inflow Inflow Occurrence Volume Volume Error
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal Percent
-------------------------------------------------------------------------------------------------
outfall OUTFALL 0.00 4.14 0 03:27 0 3.8 0.000
ExistPondingArea STORAGE 163.31 170.84 0 00:40 2.88 3.8 0.008
Pond1 STORAGE 41.80 42.28 0 00:40 0.677 0.928 0.020
PondOS2 STORAGE 20.25 20.25 0 00:40 0.251 0.251 0.008
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
Storage Volume Summary
**********************
SWMM 5 Page 3
--------------------------------------------------------------------------------------------------
Average Avg Evap Exfil Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------------
ExistPondingArea 105.635 6 0 0 443.572 26 0 03:26 4.14
Pond1 0.590 0 0 0 35.444 14 0 01:28 10.09
PondOS2 2.468 4 0 0 30.013 45 0 02:15 0.50
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg Max Total
Freq Flow Flow Volume
Outfall Node Pcnt CFS CFS 10^6 gal
-----------------------------------------------------------
outfall 68.02 1.72 4.14 3.804
-----------------------------------------------------------
System 68.02 1.72 4.14 3.804
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
Out_ExPnd DUMMY 4.14 0 03:27
P_1_Out DUMMY 10.09 0 01:28
P_OS2_Out DUMMY 0.50 0 00:41
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
SWMM 5 Page 4
Analysis begun on: Fri Feb 07 16:27:18 2020
Analysis ended on: Fri Feb 07 16:27:18 2020
Total elapsed time: < 1 sec
SWMM 5 Page 5
Link Out_ExPnd Flow (CFS)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Flow (CFS)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
SWMM 5 Page 1
Node ExistPondingArea Volume (ft3)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Volume (ft3)
450000.0
400000.0
350000.0
300000.0
250000.0
200000.0
150000.0
100000.0
50000.0
0.0
SWMM 5 Page 1
Link P_OS2_Out Flow (CFS)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Flow (CFS)
0.6
0.4
0.2
0.0
SWMM 5 Page 1
Node PondOS2 Volume (ft3)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Volume (ft3)
35000.0
30000.0
25000.0
20000.0
15000.0
10000.0
5000.0
0.0
SWMM 5 Page 1
Link P_1_Out Flow (CFS)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Flow (CFS)
12.0
10.0
8.0
6.0
4.0
2.0
0.0
SWMM 5 Page 1
Node Pond1 Volume (ft3)
Elapsed Time (hours)
0 20 40 60 80 100 120 140
Volume (ft3)
40000.0
35000.0
30000.0
25000.0
20000.0
15000.0
10000.0
5000.0
0.0
SWMM 5 Page 1
APPENDIX D
Erosion Control Report
Rennat Subdivision
Preliminary 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 E
USDA Soils Information
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 24, 2019
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
(https://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
2
alternative means 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.................................................................................................................. 8
Soil Map................................................................................................................9
Legend................................................................................................................10
Map Unit Legend................................................................................................ 11
Map Unit Descriptions.........................................................................................11
Larimer County Area, Colorado...................................................................... 13
5—Aquepts, loamy......................................................................................13
35—Fort Collins loam, 0 to 3 percent slopes.............................................. 14
36—Fort Collins loam, 3 to 5 percent slopes.............................................. 15
37—Fort Collins loam, 5 to 9 percent slopes.............................................. 17
55—Kim loam, 5 to 9 percent slopes.......................................................... 18
63—Longmont clay, 0 to 3 percent slopes.................................................. 19
73—Nunn clay loam, 0 to 1 percent slopes.................................................20
74—Nunn clay loam, 1 to 3 percent slopes.................................................22
79—Otero sandy loam, 5 to 9 percent slopes............................................. 23
103—Stoneham loam, 5 to 9 percent slopes.............................................. 25
References............................................................................................................27
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
5
scientists classified and named the soils in the survey area, they compared the
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
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6
identified each as a specific map unit. Aerial photographs show trees, buildings,
fields, roads, and rivers, all of which help in locating boundaries accurately.
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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.
8
9
Custom Soil Resource Report
Soil Map
4483400 4483500 4483600 4483700 4483800 4483900 4484000
4483400 4483500 4483600 4483700 4483800 4483900 4484000
495800 495900 496000 496100 496200 496300 496400 496500 496600 496700
495800 495900 496000 496100 496200 496300 496400 496500 496600 496700
40° 30' 25'' N
105° 3' 1'' W
40° 30' 25'' N
105° 2' 17'' W
40° 30' 3'' N
105° 3' 1'' W
40° 30' 3'' N
105° 2' 17'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,700 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
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:
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
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
5 Aquepts, loamy 13.9 23.5%
35 Fort Collins loam, 0 to 3 percent
slopes
5.1 8.6%
36 Fort Collins loam, 3 to 5 percent
slopes
20.2 34.2%
37 Fort Collins loam, 5 to 9 percent
slopes
0.1 0.2%
55 Kim loam, 5 to 9 percent slopes 3.3 5.5%
63 Longmont clay, 0 to 3 percent
slopes
8.2 13.9%
73 Nunn clay loam, 0 to 1 percent
slopes
0.1 0.2%
74 Nunn clay loam, 1 to 3 percent
slopes
0.5 0.8%
79 Otero sandy loam, 5 to 9
percent slopes
7.6 12.9%
103 Stoneham loam, 5 to 9 percent
slopes
0.1 0.2%
Totals for Area of Interest 59.1 100.0%
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
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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.
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.
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Larimer County Area, Colorado
5—Aquepts, loamy
Map Unit Setting
National map unit symbol: jpws
Elevation: 4,500 to 6,700 feet
Mean annual precipitation: 12 to 18 inches
Mean annual air temperature: 39 to 50 degrees F
Frost-free period: 80 to 140 days
Farmland classification: Not prime farmland
Map Unit Composition
Aquepts and similar soils: 80 percent
Minor components: 20 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Aquepts
Setting
Landform: Draws, depressions, stream terraces
Landform position (three-dimensional): Base slope, tread, dip
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Loamy alluvium
Typical profile
H1 - 0 to 60 inches: variable
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Very poorly drained
Runoff class: Negligible
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
very high (0.60 to 99.90 in/hr)
Depth to water table: About 6 to 18 inches
Frequency of flooding: Rare
Frequency of ponding: None
Interpretive groups
Land capability classification (irrigated): 5w
Land capability classification (nonirrigated): 3w
Hydrologic Soil Group: A/D
Hydric soil rating: Yes
Minor Components
Nunn
Percent of map unit: 5 percent
Hydric soil rating: No
Kim
Percent of map unit: 5 percent
Hydric soil rating: No
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Stoneham
Percent of map unit: 5 percent
Hydric soil rating: No
Fort collins
Percent of map unit: 5 percent
Hydric soil rating: No
35—Fort Collins loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlnc
Elevation: 4,020 to 6,730 feet
Mean annual precipitation: 14 to 16 inches
Mean annual air temperature: 46 to 48 degrees F
Frost-free period: 143 to 154 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Fort collins and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform: Interfluves
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene or older alluvium derived from igneous, metamorphic
and sedimentary rock and/or eolian deposits
Typical profile
Ap - 0 to 4 inches: loam
Bt1 - 4 to 9 inches: clay loam
Bt2 - 9 to 16 inches: clay loam
Bk1 - 16 to 29 inches: loam
Bk2 - 29 to 80 inches: loam
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.20 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 12 percent
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Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 4c
Hydrologic Soil Group: C
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
Vona
Percent of map unit: 5 percent
Landform: Interfluves
Landform position (two-dimensional): Backslope, footslope
Landform position (three-dimensional): Side slope, base slope
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Sandy Plains (R067BY024CO)
Hydric soil rating: No
36—Fort Collins loam, 3 to 5 percent slopes
Map Unit Setting
National map unit symbol: jpw9
Elevation: 4,800 to 5,500 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
Fort collins and similar soils: 90 percent
Minor components: 10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform: Fans, terraces
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Landform position (three-dimensional): Base slope, riser
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 20 inches: loam, clay loam
H2 - 9 to 20 inches: loam, silt loam, fine sandy loam
H3 - 20 to 60 inches:
H3 - 20 to 60 inches:
H3 - 20 to 60 inches:
Properties and qualities
Slope: 3 to 5 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 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 25.5 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Ascalon
Percent of map unit: 5 percent
Hydric soil rating: No
Kim
Percent of map unit: 3 percent
Hydric soil rating: No
Stoneham
Percent of map unit: 2 percent
Hydric soil rating: No
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37—Fort Collins loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpwb
Elevation: 4,800 to 5,500 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: Farmland of statewide importance
Map Unit Composition
Fort collins and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform: Fans, terraces
Landform position (three-dimensional): Base slope, riser
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 6 inches: loam
H2 - 6 to 18 inches: loam, clay loam
H2 - 6 to 18 inches: loam, silt loam, fine sandy loam
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
Properties and qualities
Slope: 5 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 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 26.4 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 4e
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Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Larimer
Percent of map unit: 8 percent
Hydric soil rating: No
Kim
Percent of map unit: 4 percent
Hydric soil rating: No
Stoneham
Percent of map unit: 3 percent
Hydric soil rating: No
55—Kim loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpwz
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: Farmland of local importance
Map Unit Composition
Kim and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Kim
Setting
Landform: Fans
Landform position (three-dimensional): Base slope, side slope
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium
Typical profile
H1 - 0 to 7 inches: loam
H2 - 7 to 60 inches: loam, clay loam, sandy clay loam
H2 - 7 to 60 inches:
H2 - 7 to 60 inches:
Properties and qualities
Slope: 5 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
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Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 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 slightly saline (0.0 to 4.0 mmhos/cm)
Available water storage in profile: Very high (about 26.5 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Thedalund
Percent of map unit: 10 percent
Hydric soil rating: No
Stoneham
Percent of map unit: 5 percent
Hydric soil rating: No
63—Longmont clay, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpx8
Elevation: 4,800 to 5,800 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 and reclaimed of excess salts
and sodium
Map Unit Composition
Longmont and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Longmont
Setting
Landform: Flood plains, valleys
Landform position (three-dimensional): Base slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Clayey alluvium derived from shale
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Typical profile
H1 - 0 to 60 inches: clay
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Poorly drained
Runoff class: High
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: About 24 to 30 inches
Frequency of flooding: Occasional
Frequency of ponding: None
Calcium carbonate, maximum in profile: 15 percent
Gypsum, maximum in profile: 5 percent
Salinity, maximum in profile: Slightly saline to strongly saline (4.0 to 16.0
mmhos/cm)
Sodium adsorption ratio, maximum in profile: 20.0
Available water storage in profile: Moderate (about 8.4 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 6w
Hydrologic Soil Group: D
Ecological site: Salt Meadow (R067BY035CO)
Hydric soil rating: No
Minor Components
Aquolls
Percent of map unit: 5 percent
Landform: Swales
Hydric soil rating: Yes
Dacono
Percent of map unit: 5 percent
Hydric soil rating: No
Heldt
Percent of map unit: 5 percent
Hydric soil rating: No
73—Nunn clay loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: 2tlng
Elevation: 4,100 to 5,700 feet
Mean annual precipitation: 14 to 15 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 135 to 152 days
Farmland classification: Prime farmland if irrigated
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Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene aged alluvium and/or eolian deposits
Typical profile
Ap - 0 to 6 inches: clay loam
Bt1 - 6 to 10 inches: clay loam
Bt2 - 10 to 26 inches: clay loam
Btk - 26 to 31 inches: clay loam
Bk1 - 31 to 47 inches: loam
Bk2 - 47 to 80 inches: loam
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 7 percent
Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
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Wages
Percent of map unit: 5 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
74—Nunn clay loam, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlpl
Elevation: 3,900 to 5,840 feet
Mean annual precipitation: 13 to 17 inches
Mean annual air temperature: 50 to 54 degrees F
Frost-free period: 135 to 160 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene aged alluvium and/or eolian deposits
Typical profile
Ap - 0 to 9 inches: clay loam
Bt - 9 to 13 inches: clay loam
Btk - 13 to 25 inches: clay loam
Bk1 - 25 to 38 inches: clay loam
Bk2 - 38 to 80 inches: clay loam
Properties and qualities
Slope: 1 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
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Calcium carbonate, maximum in profile: 7 percent
Salinity, maximum in profile: Nonsaline to very slightly saline (0.1 to 2.0
mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Satanta
Percent of map unit: 5 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
79—Otero sandy loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpxt
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: Not prime farmland
Map Unit Composition
Otero and similar soils: 80 percent
Minor components: 20 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Custom Soil Resource Report
23
Description of Otero
Setting
Landform: Fans
Landform position (three-dimensional): Base slope, side slope
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium and/or eolian deposits
Typical profile
H1 - 0 to 14 inches: sandy loam
H2 - 14 to 60 inches: sandy loam, fine sandy loam, loamy very fine sand
H2 - 14 to 60 inches:
H2 - 14 to 60 inches:
Properties and qualities
Slope: 5 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Somewhat excessively drained
Runoff class: 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: 5 percent
Salinity, maximum in profile: Nonsaline to slightly saline (0.0 to 4.0 mmhos/cm)
Available water storage in profile: Very high (about 15.4 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: A
Ecological site: Sandy Plains (R067BY024CO)
Hydric soil rating: No
Minor Components
Kim
Percent of map unit: 9 percent
Hydric soil rating: No
Nelson
Percent of map unit: 6 percent
Hydric soil rating: No
Tassel
Percent of map unit: 5 percent
Hydric soil rating: No
Custom Soil Resource Report
24
103—Stoneham loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jptw
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: Farmland of local importance
Map Unit Composition
Stoneham and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Stoneham
Setting
Landform: Benches, terraces
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 3 inches: loam
H2 - 3 to 9 inches: clay loam, sandy clay loam, loam
H2 - 3 to 9 inches: loam, clay loam, sandy clay loam
H2 - 3 to 9 inches:
H3 - 9 to 60 inches:
H3 - 9 to 60 inches:
H3 - 9 to 60 inches:
Properties and qualities
Slope: 5 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 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 27.7 inches)
Interpretive groups
Land capability classification (irrigated): 6e
Custom Soil Resource Report
25
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Kim
Percent of map unit: 8 percent
Hydric soil rating: No
Larimer
Percent of map unit: 5 percent
Hydric soil rating: No
Fort collins
Percent of map unit: 2 percent
Hydric soil rating: No
Custom Soil Resource Report
26
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
27
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
28
MAP POCKET
Drainage Exhibit
12" W
12" W
X
SS
VAULT
ELEC
X
X
X
X
X
IRR
WM WM WM WM
WM
WM
WM WM
WM
WM
WM
WM WM
WM WM
WM
WM
WM
WM WM
WM WM WM
WM
WM
WM WM
WM WM WM WM
WM
WM
WM
WM
WM
WM WM
WM
WM
WM
WM
WM
UD
UD
UD
E
E E
E
E
E E
E
E
E
E
E E
E E E E
E
E E
E E
E E
E E
E
E
E
E
E
E
E
E
E
E E
E
E E E
E
E
E E E E E
E
E
E
E E
E
E
E
E
E
E
E
E
E
E
E
E E E E
E E
E
E E
E
E
E
G
G
G
G
G G G
G
G
G
G
G
G
G
G G G G G
G
G
G
G
G
G
G
G
G
G G
G
G
G
G
G
G
G
G
G
G G G
G
G
G
E E
E
G
G G
G
G
G
G
G
G G
G
G G G G
G
G G
G
G
G
G G
G
G
G
G
G
G
G
G G G
G
G
G G
G
G
G
G
G
G G G G
E
E E
E
E
E
E
E E
E E
E E
E
G
G
G
G
G
G
G
G
G
G
E
E
E E
E
E
E
E
E
E
E
E
E
E
E
E
G G
G
G
G
G
G
G
G
G
G
G
G
G G
G
E
E
E
G
G
UD
UD
UD UD UD UD UD UD UD
UD
UD
UD
G G
E
E
E
G
G
UD
UD UD UD
UD UD
UD
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT
VAULT VAULT
E
VAULT
VAULT
VAULT
VAULT
VAULT
TELE
T
VAULT
TELE
W
S
O
H
Y
D
W
TELE
VAULT
ELEC
VAULT
ELEC
VAULT
ELEC
VAULT
ELEC
H
Y
D
S S
S
ELEC
E
ELEC
BRKR
X
X
X X X X X X X
X
X X
X
X
X
X
X
X X
X
X X X X
X
X
X
X
X
X
X
X X
X
X
X
X X X X X
X
X
X
SS
SS
SS SS
SS SS
LID
VAULT
F.O.
W W W
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
E
E
E
E
E
E
E
E
E
T
T
T T
T
T
T T
T
T
T
G
G
G
G
G
G
T
T
T
W
W
W
W
W W
W
X
X
X
X
X
X X
X
X
X
X X X X X
X
X
X
4
1
2
3
6b
8 10
11a
4
11b
1
2
5
6b
7b
8 3
13
12 12
10
9
9
5
7b
11b
6a
7a
7a
6a
11a
CROAKING TOAD DR
FLYING MALLARD DR
WINDY WILLOW DR
MISTY MEADOW DR
ZEPHYR RD
FALLEN BRANCH DR
AUTUMN BREEZE CT
DITCH LATERAL
UNION-PACIFIC RAILROAD
EXISTING POND
DETENTION
POND 1
RED WILLOW
DRIVE
DANCING CATTAIL DR
13
WATER
QUALITY
POND 1
WATER
QUALITY
POND 2
RAIN
GARDEN 1
GRASS LINED SWALE
PROVIDES PRE-TREATMENT AND
STANDARD WATER QUALITY
OS1 OS1
OS2
OS2
X
X
X
X
X
X
X
Sheet
RENNAT SUBDIVISION These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
E NGINEER ING
N O R T H E RN
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
970.221.4158
northernengineering.com
of 66
DR1
DRAINAGE EXHIBIT
54
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
NORTH
MATCHLINE-THIS SHEET
MATCHLINE-THIS SHEET
LEGEND:
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
DESIGN POINT A
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
1
B2
1.45 ac
1
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 1 4.34 0.54 0.67 14.1 14.1 4.5 19.5
2 2 3.33 0.52 0.65 12.8 12.8 3.5 15.3
3 3 4.32 0.60 0.75 13.9 13.9 5.1 22.1
4 4 23.91 0.37 0.46 11.2 11.2 18.8 81.8
5 5 1.54 0.59 0.74 14.7 14.7 1.7 7.5
6a 6a 0.73 0.60 0.75 11.4 11.4 0.9 4.1
6b 6b 2.26 0.53 0.66 13.5 13.5 2.4 10.3
7a 7a 1.10 0.54 0.68 12.6 12.6 1.2 5.3
7b 7b 3.83 0.54 0.67 14.2 14.2 4.0 17.3
8 8 1.72 0.54 0.67 12.5 12.5 1.9 8.3
9 9 1.57 0.57 0.71 14.9 14.9 1.7 7.3
10 10 0.09 0.63 0.79 6.4 6.4 0.1 0.6
11a 11a 2.23 0.60 0.75 13.3 13.3 2.6 11.6
11b 11b 0.95 0.37 0.46 10.4 10.4 0.8 3.4
12 12 3.05 0.52 0.65 15.5 15.5 2.9 12.8
13 13 2.51 0.59 0.74 13.0 13.0 2.9 12.9
OS1 OS1 0.34 0.71 0.88 13.0 13.0 0.5 2.1
POND SUMMARY TABLE
Pond ID
100-Yr.
Detention Vol.
(Ac-Ft)
Total Req'd
Vol. (Ac-Ft)
100-Yr.
Detention
WSEL (Ft)
Peak Release
(cfs)
Pond 1 0.81 0.81 4952.80 10.10
Existing Wet Pond 10.26 10.26 4943.60 4.20
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 13, Sep 10, 2018
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
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
10
Q = 0 . 67 A ( 2 gH ) 0 . 5
TELE
VAULT
ELEC
VAULT
ELEC
VAULT
ELEC
VAULT
ELEC
ELEC
E
ELEC
BRKR
X
X
X X X X X X X
X
X X
X
X
X
X
X
X X
X
X X X X
X
X
X
X
X
X
X
X X
X
X
X
X X X X X
X
X
X
L
ID
VAULT
F.O.
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
FO
E
E
E
E
E
E
E
E
E
T
T
T T
T
T
T T
T
T
T
G
G
G
G
G
G
T
T
T
X
X
X
X
X
X X
X
X
X
X X X X X
X
X
X
DANCING CATTAIL DR
CROAKING TOAD DR
FLYING MALLARD DR
WINDY WILLOW DR
MISTY MEADOW DR
ZEPHYR RD
FALLEN BRANCH DR
AUTUMN BREEZE CT
DITCH LATERAL
UNION-PACIFIC RAILROAD
EXISTING
DETENTION POND
DETENTION
POND 1
RED WILLOW
DRIVE
DANCING CATTAIL DR
1
2
6c 3
8
13
10
OS1
11a
4a
11b
12
9
5b
7b
7a
5a
4b
4c
4e
4d
RAIN
GARDEN 1
GRASS LINED SWALE
PROVIDES PRE-TREATMENT AND
STANDARD WATER QUALITY
GRASS LINED
SWALE
WATER
QUALITY
POND 2
WATER
QUALITY
POND 1
6b
6a
X
X
X
X
X
X
X
4a
Sheet
RENNAT SUBDIVISION These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
E NGINEER ING
N O R T H E RN
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
970.221.4158
northernengineering.com
of 1
LID
LID EXHIBIT
1
NORTH
MATCHLINE-THIS SHEET
MATCHLINE-THIS SHEET
LEGEND:
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
DESIGN POINT A
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
1
B2
1.45 ac
1
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
LID ID
Area Weighted %
Impervious Subbasin ID
Treatment Type Volume per
UD-BMP (ft3)
Impervious Area
Sq. Ft. Acres (ft2)
LID 764,154 17.54 36%
2, 3, 4c, 5a, 6a, 6b, 7a, 8,
9, 13, OS1 Rain Garden 1
8,611 299,955
Total 764,154 17.54 299,955
LID Site Summary
Total Site Area 2,534,070 ft2
Total Site Impervious Area 599,801 ft2
50% Required Minimum Area to be Treated 299,900 ft2
Total Treated Impervious Area 299,955 ft2
Percent Impervious Treated by LID 50.0%
1.5
Max 8.0
Riprap
Type
(From
Figure
MD-21 or
MD-22)
By: ATC
CALCULATE
Date: 2/1/20
Storm
Line/Culvert
Label
Design
Discharge
(cfs)
Expansion
Factor
1/(2tanq)
(From
Figure
MD-23 or
MD-24)
Yt,
Tailwater
Depth
(ft)
OUTPUT
Spec
Length
of
Riprap
(ft)
Box Culvert
55 0.87 1.48 3.03
22 1.53 2.61 5.32
56 0.86 1.47 2.99
23 1.49 2.55 5.20
57 0.85 1.45 2.96
24 1.46 2.49 5.09
58 0.84 1.43 2.92
25 1.43 2.44 4.98
59 0.83 1.42 2.89
26 1.4 2.39 4.87
60 0.82 1.4 2.86
27 1.37 2.34 4.78
65 0.78 1.32 2.71
28 1.34 2.29 4.69
70 0.73 1.25 2.59
29 1.32 2.25 4.60
75 0.70 1.19 2.48
30 1.30 2.21 4.52
80 0.66 1.14 2.38
31 1.27 2.16 4.42
85 0.64 1.09 2.29
32 1.24 2.12 4.33
90 0.61 1.05 2.21
33 1.22 2.08 4.24
95 0.58 1.01 2.13
34 1.19 2.04 4.16
100 0.56 0.97 2.06
35 1.17 2.00 4.08
105 0.54 0.94 2.00
36 1.15 1.96 4.01
110 0.52 0.91 1.94
37 1.16 1.93 3.93
115 0.51 0.88 1.88
38 1.11 1.89 3.87
120 0.49 0.86 1.84
(min)
Q C f C i A
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 1 No 0.25 0.25 0.31 110 2.00% 13.2 13.2 12.3 622 1.00% 2.00 5.2 0 0.00% N/A N/A 14.1 14.1 14.1
2 2 No 0.25 0.25 0.31 106 2.00% 13.0 13.0 12.0 393 1.00% 2.00 3.3 0 0.00% N/A N/A 12.8 12.8 12.8
3 3 No 0.25 0.25 0.31 124 2.00% 14.0 14.0 13.0 584 1.00% 2.00 4.9 0 0.00% N/A N/A 13.9 13.9 13.9
4 4 No 0.25 0.25 0.31 220 3.40% 15.7 15.7 14.5 0 0.00% N/A N/A 0 0.00% N/A N/A 11.2 11.2 11.2
5 5 No 0.25 0.25 0.31 48 2.00% 8.7 8.7 8.1 792 1.00% 2.00 6.6 0 0.00% N/A N/A 14.7 14.7 14.7
6a 6a No 0.25 0.25 0.31 52 2.00% 9.1 9.1 8.4 274 1.00% 2.00 2.3 0 0.00% N/A N/A 11.4 11.4 11.4
6b 6b No 0.25 0.25 0.31 50 2.00% 8.9 8.9 8.3 579 1.00% 2.00 4.8 0 0.00% N/A N/A 13.5 13.5 13.5
7a 7a No 0.25 0.25 0.31 105 2.00% 12.9 12.9 12.0 363 1.00% 2.00 3.0 0 0.00% N/A N/A 12.6 12.6 12.6
7b 7b No 0.25 0.25 0.31 98 2.00% 12.5 12.5 11.6 652 1.00% 2.00 5.4 0 0.00% N/A N/A 14.2 14.2 14.2
8 8 No 0.25 0.25 0.31 70 2.00% 10.6 10.6 9.8 372 1.00% 2.00 3.1 0 0.00% N/A N/A 12.5 12.5 12.5
9 9 No 0.25 0.25 0.31 48 2.00% 8.7 8.7 8.1 830 1.00% 2.00 6.9 0 0.00% N/A N/A 14.9 14.9 14.9
10 10 No 0.25 0.25 0.31 22 2.00% 5.9 5.9 5.5 58 1.00% 2.00 0.5 0 0.00% N/A N/A 6.4 6.4 6.4
11a 11a No 0.25 0.25 0.31 45 2.00% 8.5 8.5 7.8 575 1.00% 2.00 4.8 0 0.00% N/A N/A 13.3 13.3 13.3
11b 11b No 0.25 0.25 0.31 75 2.00% 10.9 10.9 10.1 0 0.00% N/A N/A 0 0.00% N/A N/A 10.4 10.4 10.4
12 12 No 0.25 0.25 0.31 124 2.00% 14.0 14.0 13.0 866 1.00% 2.00 7.2 0 0.00% N/A N/A 15.5 15.5 15.5
13 13 No 0.25 0.25 0.31 85 2.00% 11.6 11.6 10.8 462 1.00% 2.00 3.9 0 0.00% N/A N/A 13.0 13.0 13.0
OS1 OS1 No 0.25 0.25 0.31 85 2.00% 11.6 11.6 10.8 455 1.00% 2.00 3.8 0 0.00% N/A N/A 13.0 13.0 13.0
TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
ATC
February 4, 2020
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
8 74945 1.72 0.41 0.09 0.21 0.00 1.02 0.54 0.54 0.67 39%
9 68296 1.57 0.44 0.08 0.19 0.00 0.86 0.57 0.57 0.71 43%
10 3746 0.09 0.03 0.00 0.01 0.00 0.04 0.63 0.63 0.79 52%
11a 97116 2.23 0.74 0.11 0.27 0.00 1.11 0.60 0.60 0.75 48%
11b 41286 0.95 0.00 0.05 0.11 0.00 0.79 0.37 0.37 0.46 15%
12 132969 3.05 0.67 0.15 0.37 0.00 1.86 0.52 0.52 0.65 37%
13 109212 2.51 0.90 0.23 0.47 0.00 0.91 0.70 0.70 0.87 61%
OS1 14994 0.34 0.17 0.02 0.04 0.00 0.12 0.71 0.71 0.88 63%
COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table3.2-2. % Impervious taken from UDFCD USDCM, Volume I. NOTE:
Impervious areas have been estimated for
preliminary design and planning purposes and are subject to change at Final Design.
10-year Cf = 1.00
February 4, 2020