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FINAL DRAINAGE REPORT
SNOW RIDGE APARTMENTS
FORT COLLINS, COLORADO
APRIL 3, 2024
NORTHERNENGINEERING.COM
970.221.4158
FORT COLLINS
GREELEY
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FORT COLLINS | GREELEY COVER LETTER
April 3, 2024
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: FINAL DRAINAGE REPORT FOR
SNOW RIDGE APARTMENTS
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage Report for your review. This report accompanies
the Final submittal for the proposed Snow Ridge Apartments.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM) and serves
to document the stormwater impacts associated with the project. We understand that review by the City of Fort
Collins is to assure general compliance with standardized criteria contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
AMANDA POINCELOT JACOB O’BANION
Project Manager Project Engineer
Compliance Statement
I hereby attest that this report for the final drainage design for the Snow Ridge Apartments was prepared by me
or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual.
I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by
others.
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FORT COLLINS | GREELEY TABLE OF CONTENTS
TABLE OF CONTENTS
GENERAL LOCATION AND DESCRIPTION .......................................................... 1
DRAIN BASINS AND SUB-BASINS ..................................................................... 3
DRAINAGE DESIGN CRITERIA .......................................................................... 4
DRAINAGE FACILITY DESIGN ........................................................................... 6
CONCLUSIONS .............................................................................................. 8
REFERENCES ................................................................................................ 9
TABLES AND FIGURES
FIGURE 1 – AERIAL PHOTOGRAPH ...................................................................................1
FIGURE 2 – FEMA FIRMETTE .............................................................................................3
FIGURE 3 – EXISTING CITY FLOODPLAINS .......................................................................3
TABLE 1 - DETENTION SUMMARY .....................................................................................7
APPENDICES
APPENDIX A – HYDROLOGIC COMPUTATIONS
APPENDIX B – HYDRAULIC CALCULATIONS
APPENDIX C –WATER QUALITY/LID COMPUTATIONS
APPENDIX D – EROSION CONTROL REPORT
APPENDIX E – USDA SOILS REPORT
APPENDIX F – SIGNED VARIANCE APPLICATION
MAP POCKET
DR1 – DRAINAGE EXHIBIT
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GENERAL LOCATION AND DESCRIPTION
A. LOCATION
Vicinity Map
The Snow Ridge Apartments project site is a tract of land located in the southeast quarter of Section
15, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of
Larimer, State of Colorado.
The project site (refer to Figure 1) is bordered to the north by an existing single-family residential
area; to the south by Prospect Road; to the east by Shields Street; and to the west by an existing
single-family residential area.
B. DESCRIPTION OF PROPERTY
The Snow Ridge Apartments is a ± 0.67-acre tract.
The site is currently zoned as Neighborhood Conservation, Buffer District (N-C-B) with one existing
residential structure on site.
The subject property is not located within a FEMA floodplain or within a City of Fort Collins
regulatory floodplain.
Figure 1 – Aerial Photograph
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FORT COLLINS | GREELEY 2 | 11
The existing groundcover consists of grass with tree cover, a residential structure, and an asphalt
driveway. The existing on-site runoff of the western two thirds of the property generally drains from
the east-to-southwest where it sheet flows to the adjacent properties to the south and west. The
existing on-site runoff of the eastern third of the property generally drains from the west-to-east
across moderately flat grades (e.g., <6.00%) onto Shields Street. From there, the drainage
continues to Prospect Road, and is received by the New Mercer Canal.
According to the United States Department of Agriculture (USDA) Natural Resources Conservation
Service (NRCS) Soil Survey, the site consists primarily of Altvan-Satana loams which fall into
Hydrologic Soil Group B.
The proposed development is an 8-unit complex. Consisting of a conversion of the existing
residential structure to a 2-unit complex and the addition of (3) 2-unit interconnected structures.
Other proposed improvements include a new drive aisle consisting of concrete and permeable
pavers, new sidewalks and new landscaping, a mailroom with bike storage, outdoor bike parking,
trash enclosure, and a patio common area.
The proposed land use is Multi-Family Residential. This is a permitted use in the existing
Neighborhood Conservation Buffer (NCB) zoning between CSU/Downtown and the residential
neighborhoods to the west.
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C. FLOODPLAIN
The subject property is not located within a FEMA floodplain or within a City regulatory
floodplain.
Figure 2 – FEMA FIRMette
Figure 3 – Existing City Floodplains
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DRAIN BASINS AND SUB-BASINS
A. MAJOR BASIN DESCRIPTION
a) The Snow Ridge Apartments project is located within the Canal Importation Basin. The Canal
Importation Basin encompasses almost five square miles (3,200 acres) of west-central Fort Collins.
Three irrigation canals pass through the basin flowing generally from north to south. The runoff
from the Snow Ridge Apartments is received by the New Mercer Canal which generally flows west
to east.
B. SUB-BASIN DESCRIPTION
The project site is broken up into five sub-basins. Three on-site basins and two off-site basins. The
central and western on-site basins are connected via a subdrain that receives infiltration from the
pavers located in the drive isle within both basins. The eastern onsite basin flows to the proposed
detention pond adjacent to Shields Street. The project site has one outfall location which is the
existing flowline of Shields Street.
The project site does not receive notable runoff from contiguous off-site properties.
DRAINAGE DESIGN CRITERIA
A. STORMWATER MANAGEMENT STRATEGY
The overall stormwater management strategy employed with Snow Ridge Apartments 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. Snow Ridge Apartments aims to reduce runoff peaks,
volumes and pollutant loads from frequently occurring storm events (i.e., water quality (i.e., 80th
percentile) and 2-year storm events) by implementing Low Impact Development (LID) strategies.
Wherever practical, runoff will be routed across landscaped areas or through Permeable Interlocking
Concrete Pavers (PICP). These LID practices reduce the overall amount of impervious area, while at the
same time Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA
techniques will be implemented, where practical, throughout the development, thereby slowing runoff
and increasing opportunities for infiltration.
Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow
Release. The efforts taken in Step 1 will help to minimize excess runoff from frequently occurring storm
events; however, urban development of this intensity will still have stormwater runoff leaving the site.
The primary water quality treatment will occur via Permeable Interlocking Concrete Pavers (PICP) to a
subdrain beneath the parking and drive isle from the northwest part of the site that flows to the
detention pond in the east. In addition to LID treatment, traditional water quality treatment will be
provided within the lower stages of the detention pond.
Step 3 – Stabilize Drainageways. The Snow Ridge Apartments project aims to protect the existing
New Mercer Canal by limiting any increases beyond historical flow rates within the ditch. By utilizing a
combination of LID, traditional water quality treatment, and a detention pond. As such, the peak
discharge from the Snow Ridge Apartments project will not be compounded with peak flow in the
ditch. Furthermore, this project will pay a one-time stormwater development fee, as well as ongoing
monthly utility fees, both of which help achieve citywide drainage stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to
industrial and commercial developments. This does not apply to this site.
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B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
The subject property is part of the Canal Importation Basin Master Drainage Plan.
The site plan is constrained on the north, south, and west by residential properties, and on the east
side by Shields Street.
C. HYDROLOGICAL CRITERIA
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 Snow Ridge
Apartments development. Data contained in Table 3.4-1 has been utilized for Rational Method
runoff calculations.
The Rational Method has been employed to compute stormwater runoff utilizing coefficients
contained in Tables 4.1-2 and 4.1-3 of the FCSCM.
Two separate design storms have been utilized to address distinct drainage scenarios. The first
event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second
event considered is the “Major Storm,” which has a 100-year recurrence interval.
D. HYDRAULIC CRITERIA
The drainage facilities proposed with the Snow Ridge Apartments development project are
designed in accordance with criteria outlined in the Mile High Flood District’s “Urban Storm
Drainage Criteria Manual” (UDFCD) and the Fort Collins Stormwater Criteria Manual (FCSCM).
As stated in Section I.B.3, above, the subject property is not located within a FEMA floodplain or
within a City of Fort Collins regulatory floodplain.
E. CONFORMANCE WITH WATER QUALITY TREATMENT CRITERIA
City Code requires that 100% of runoff from a project site receive some sort of water quality treatment.
This project proposes to provide water quality treatment using Permeable Interlocking Concrete
Pavers (PICP) and traditional water within the lower stages of the detention pond. Through these
methods 100% of the on-site area will be treated for water quality.
F. CONFORMANCE WITH LOW IMPACT DEVELOPMENT (LID)
The project site will conform with the requirement to treat a minimum of 50% of the proposed
impervious surfaces using LID treatment from PICP pavers. Please see Appendix C for LID design
information, table, and exhibit(s). As shown in the LID table provided in the appendix, 60.94% of the
proposed site impervious area will receive LID treatment from PICP pavers, which exceeds the
minimum required.
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G. SIZING OF LID SYSTEMS
Permeable Pavers Systems
The type of Permeable Pavement sections chosen for this project are Permeable Interlocking
Concrete Pavers.
The effective imperviousness of area tributary to permeable pavement, the tributary watershed
area and the area of the permeable pavement system were used to determine the required storage
volumes for each area of the PICPs.
The minimum depth of reservoir, the slope of the subgrade, the porosity of the subgrade, the slope
of the subgrade interface, and the length between lateral flow barriers were used to determine the
volume provided based on the depth of base course.
DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
The main objective of the Snow Ridge Apartments project drainage design is to maintain existing
drainage patterns, while not adversely impacting adjacent properties.
A list of tables and figures used within this report can be found in the Table of Contents at the front
of the document. The tables and figures are located within the sections to which the content best
applies.
Drainage for the project site has been analyzed using five (5) drainage sub-basins. On-site is
designated as sub-basins A1, A2, and A3. Offsite basins designated as OS1 and OS2. The drainage
patterns anticipated for the basins are further described below.
Sub-Basin A1
Sub-basin A1 is comprised of a section of the drive Isle, portions of the multi-family development,
vegetated area, and the detention pond. Drainage is routed to the pond via curb/gutters, swales
and a concrete drain pan.
Sub-Basin A2
Sub-basin A2 is comprised of portions of the multifamily development and the drive isle. Drainage
is routed to Paver 1 where it will be treated for LID prior to infiltration and release via subdrain to
the pond.
Sub-Basin A3
Sub-basin A3 is comprised of portions of the multifamily development including the parking area
and drive isle, and vegetated area. Drainage is routed to Paver 2 where it will be treated for LID
prior to infiltration and release via subdrain to the pond. A low spot within A3 gathers the overflow
from the runoff of Paver 2 and a small portion of the multifamily development and directs it to the
pond via storm pipe and concrete drain pan.
Sub-Basin OS1
Sub-basin OS1 is comprised of the proposed right of way and utility easement, which includes
vegetated area, the pond outlet, a portion of sidewalk, and the entrance. Drainage is routed to the
flowline in Shields St.
Sub-Basin OS2
Sub-basin OS2 is comprised of vegetated area. This area follows the historic drainage pattern and
goes southwest.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report.
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B. SPECIFIC DETAILS
Snow Ridge Apartments is bounded by residential lots to the north, south and west and adjacent
to Shields Street on the east. The site will be discharging to Shields Street. In order to reduce runoff
peaks, volumes and pollutant loads from urbanizing areas, LID strategies and a detention pond are
proposed.
Snow Ridge Apartments proposes providing 100-year detention and utilizing extended detention
for water quality.
Permeable Interlocking Concrete Pavers are proposed to treat on-site runoff and conform with LID
practices established in the UDFCD and Fort Collins Stormwater Criteria Manual.
A stormwater variance application was submitted and approved by the City of Fort Collins. This
variance requests that the flows from basin OS-2 be released offsite and not be deducted from the
release rate of the proposed pond. A copy of the signed variance is shown in the Appendix.
Detention Pond Calculations:
a) Detention Pond Calculations were done via FAA Modified method as described in Chapter 6,
Section 2.3 in the City of Fort Collins Stormwater Criteria Manual.
Pond
ID
Tributary
Area (ac)
Weighted
Percent
Imperviousness
(%)
Extended
Detention
WQCV (ac-
ft)
LID
WQCV
(ac-ft)
100-Yr
Detention
Vol. (ac-
ft)
Total Pond
Volume
(ac-ft)
100-Yr
Detention
WSEL (ft)
Final
Release
Rate
(cfs)
Pond 1 0.23 52 0.005 N/A 0.055 0.060 5037.46 0.60
Paver 1 0.15 70 N/A 0.003 N/A N/A N/A N/A
Paver 2 0.14 57 N/A 0.002 N/A N/A N/A N/A
Table 1 - Detention Summary
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CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
The detention design proposed with the Snow Ridge Apartments project does comply with the City
of Fort Collins’ Stormwater Criteria Manual.
The drainage design proposed with the Snow Ridge Apartments complies with the City of Fort
Collins Canal Importation Master Drainage Plan.
The drainage plan and stormwater management measures proposed with the Snow Ridge
Apartments project are compliant with all applicable State and Federal regulations governing
stormwater discharge.
The requested stormwater variance has been approved by the City of Fort Collins.
B. DRAINAGE CONCEPT
The drainage design proposed with this project will effectively limit potential damage associated
with its stormwater runoff.
The proposed Snow Ridge Apartments development will not impact the Master Drainage Plan
recommendations for the Canal Importation Basin.
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REFERENCES
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November
5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code.
3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
4. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
5. Canal Importation Basin Master Drainage Plan Hydraulic Evaluation and Mapping Update, City of
Fort Collins, Colorado, Anderson Consulting Engineers, Inc., Fort Collins, Colorado, July 22, 2014.
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX A
HYDROLOGIC COMPUTATIONS
Runoff Coefficient1
Percent
Impervious1 Project:
Location:
0.95 100%Calc. By:
0.95 90%Date:
0.15 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)
Asphalt, Concrete
(acres)Rooftop (acres)
Lawns, Sandy Soil,
Avg Slope 2-7%
(acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
HA1 10,496 0.24 0.08 0.03 0.14 0.00 43% 0.50 0.50 0.50 0.62
HA2 18,660 0.43 0.02 0.02 0.39 0.00 11% 0.23 0.23 0.23 0.28
Total 29,156 0.67 0.10 0.05 0.52 0.00 23% 0.32 0.32 0.32 0.41
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).USDA SOIL TYPE: B
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
HISTORIC RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Lawns, Sandy Soil, Avg Slope 2-7%
Streets, Parking Lots, Roofs, Alleys, and Drives:
Character of Surface:Snow Ridge Apartments
Fort Collins
J. Obanion
Nov. 9, 2023
Notes:
1) A1 drains Southeast to Shields Street
2) A2 drainas Southwest to adjacent property line
Page 1 of 4
Snow Ridge Apartments
Nov. 9, 2023
Where:
C2*Cf C100*Cf
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)
Ti
2-Yr
(min)
Ti
100-Yr
(min)
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)Surface n
Flow
Area3
(sq.ft.)
WP3 (ft)R (ft)V
(ft/s)
Tt
(min)
Max.
Tc
(min)
Comp.
Tc 2-Yr
(min)
Tc
2-Yr
(min)
Comp.
Tc 100-
Yr
(min)
Tc
100-Yr
(min)
HA1 ha1 0.50 0.62 37 38.77 37.95
2.21%5.26 4.17 121 37.95 35.55
1.99%Swale (8:1)0.035 8.00 16.12 0.50 3.77 0.53 10.88 5.80 5.80 4.71 5.00
HA2 ha2 0.23 0.28 55 38.69 37.46 2.23%9.28 8.68 126 37.46 36.25 0.96% Swale (8:1)0.035 8.00 16.12 0.50 2.61 0.80 11.01 10.09 10.09 9.49 9.49
total Total 0.36 0.45 37 38.77 37.95 2.21%6.44 5.65 121 37.95 35.55 1.99% Swale (8:1)0.035 8.00 16.12 0.50 3.77 0.53 10.88 6.98 6.98 6.18 6.18
Design
Point Basin ID
Overland Flow Channelized Flow Time of Concentration
HISTORIC TIME OF CONCENTRATION COMPUTATIONS
Location:
Maximum Tc:Overland Flow, Time of Concentration:
Channelized Flow, Velocity: Channelized Flow, Time of Concentration:
Snow Ridge Apartments
Fort Collins
J. Obanion
Nov. 9, 2023
Project:
Calculations By:
Date:
Notes
S = Longitudinal Slope, feet/feet
R = Hydraulic Radius (feet)
n = Roughness Coefficient
V = Velocity (ft/sec) WP = Wetted Perimeter (ft)
(Equation 3.3-2 per Fort Collins Stormwater =1.87 1.1 − ∗
=1.49
∗
/ ∗ (Equation 5-4 per Fort Collins Stormwater
=
180 + 10
(Equation 3.3-5 per Fort Collins
Stormwater Manual)
=
∗ 60
(Equation 5-5 per Fort Collins
1) Add 4900 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5
min.
3) Assume a water depth of 6" and a typical curb and
gutter per Larimer County Urban Street Standard Detail
701 for curb and gutter channelized flow. Assume a water
depth of 1', fixed side slopes, and a triangular swale
section for grass channelized flow. Assume a water depth
Page 2 of 4
Tc2 Tc10 Tc100 C2 C10 C100 I2 I10 I100 Q2 Q10 Q100
HA1 ha1 0.24 5.8 5.8 5.0 0.5 0.5 0.6 2.8 4.7 10.0 0.3 0.6 1.5
HA2 ha2 0.43 10.1 10.1 9.5 0.2 0.2 0.3 2.2 3.8 8.0 0.2 0.4 1.0
total Total 0.67 7.0 7.0 6.2 0.3 0.3 0.4 2.6 4.4 9.3 0.6 1.0 2.5
Rational Equation: Q = CiA (Equation 6-1 per MHFD)
Area
(acres)
Runoff CTc (Min)
HISTORIC DIRECT RUNOFF COMPUTATIONS
Intensity (in/hr)Flow (cfs)
Snow Ridge Apartments
J. Obanion
Nov. 9, 2023Date:
Fort Collins
Project:
Location:
Calc. By:
Design
Point Basin
Intensity, I, from Fig. 3.4.1 Fort Collins Stormwater Manual.
Page 3 of 4
Runoff Coefficient1
Percent
Impervious1 Project:
Location:
0.95 100%Calc. By:
0.95 90%Date:
0.50 40%
0.20 2%
0.20 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)
Asphalt, Concrete
(acres)Rooftop (acres) Gravel (acres)
Undeveloped:
Greenbelts,
Agriculture (acres)
Lawns, Clayey Soil,
Flat Slope < 2%
(acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
A1 10,151 0.23 0.08 0.05 0.00 0.00 0.10 54%0.61 0.61 0.61 0.77
A2 6,552 0.15 0.05 0.04 0.05 0.00 0.01 70%0.74 0.74 0.74 0.93
A3 5,895 0.14 0.06 0.01 0.03 0.00 0.04 57%0.63 0.63 0.63 0.79
Total 22,598 0.52 0.18 0.10 0.08 0.00 0.16 59%0.66 0.66 0.66 0.82
OS1 1,827 0.04 0.01 0.00 0.00 0.00 0.03 33%0.44 0.44 0.44 0.55
OS2 4,134 0.09 0.00 0.00 0.00 0.00 0.09 2%0.20 0.20 0.20 0.25
Total 5,961 0.14 0.01 0.00 0.00 0.00 0.12 11%0.27 0.27 0.27 0.34
DEVELOPED RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Gravel
Streets, Parking Lots, Roofs, Alleys, and Drives:
Character of Surface:Snow Ridge Apartments
Fort Collins
A. Poincelot
January 11, 2024
Lawns and Landscaping:
Offsite Basins
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).
Lawns, Clayey Soil, Flat Slope < 2%
USDA SOIL TYPE: C
Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
5/18/2022
Where:
C2*Cf C100*Cf
Slope
(%)
Ti
2-Yr
(min)
Ti
100-Yr
(min)
Length
(ft)
Slope
(%)Surface n
Flow Area3
(sq.ft.)WP3 (ft)R (ft)V
(ft/s)
Tt
(min)
Max.
Tc
(min)
Comp.
Tc 2-Yr
(min)
Tc
2-Yr
(min)
Comp.
Tc 100-
Yr
(min)
Tc
100-Yr
(min)
a1 A1 0.61 0.77 2.20%4.15 2.84 152
1.32%Swale (6:1)0.035 6.00 12.17 0.49 3.05 0.83 11.04 4.98 5.00 3.67 5.00
a2 A2 0.74 0.93 5.03%2.29 1.09 120
0.73%Swale (8:1)0.035 8.00 16.12 0.50 2.28 0.88 10.86 3.17 5.00 1.97 5.00
a3 A3 0.63 0.79 1.03%5.16 3.44 54
0.54%Swale (8:1)0.035 8.00 16.12 0.50 1.96 0.46 10.49 5.62 5.62 3.90 5.00
os1 OS1 0.44 0.44 2.86%5.17 5.17 0 n/a Swale (8:1)0.00 8.00 16.12 N/A N/A 0.00 10.19 5.17 5.17 5.17 5.17
os2 OS2 0.20 0.20 5.71%5.57 5.57 0 n/a Swale (8:1)0.00 8.00 16.12 N/A N/A 0.00 10.19 5.57 5.57 5.57 5.57
Offsite Basins
Notes
S = Longitudinal Slope, feet/feet
R = Hydraulic Radius (feet)
n = Roughness Coefficient
V = Velocity (ft/sec) WP = Wetted Perimeter (ft)
Design
Point Basin ID
Overland Flow Channelized Flow Time of Concentration
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Location:
Maximum Tc:Overland Flow, Time of Concentration:
Channelized Flow, Velocity: Channelized Flow, Time of Concentration:
Snow Ridge Apartments
Fort Collins
A. Poincelot
January 11, 2024
Project:
Calculations By:
Date:
(Equation 3.3-2 per Fort
Collins Stormwater Manual)
1.87 1.1 ∗
1.49
∗
/ ∗ (Equation 5-4 per Fort Collins
Stormwater Manual)
180 10 (Equation 3.3-5 per Fort Collins
Stormwater Manual)
∗ 60
(Equation 5-5 per Fort Collins
1) Add 4900 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5
min.
3) Assume a water depth of 6" and a typical curb and gutter
per Larimer County Urban Street Standard Detail 701 for
curb and gutter channelized flow. Assume a water depth of
1', fixed side slopes, and a triangular swale section for grass
channelized flow. Assume a water depth of 1', 4:1 side
Tc2 Tc10 Tc100 C2 C10 C100 I2 I10 I100 QWQ Q2 Q10 Q100
a1 A1 0.23 5.0 5.0 5.0 0.6 0.6 0.8 2.9 4.9 10.0 0.2 0.4 0.7 1.8
a2 A2 0.15 5.0 5.0 5.0 0.7 0.7 0.9 2.9 4.9 10.0 0.2 0.3 0.5 1.4
a3 A3 0.14 5.6 5.6 5.0 0.6 0.6 0.8 2.8 4.7 10.0 0.1 0.2 0.4 1.1
os1 OS1 0.04 5.2 5.2 5.2 0.4 0.4 0.4 2.9 4.9 10.0 0.0 0.1 0.1 0.2
os2 OS2 0.09 5.6 5.6 5.6 0.2 0.2 0.2 2.8 4.7 9.6 0.0 0.1 0.1 0.2
Offsite Basins
Fort Collins
Project:
Location:
Calc. By:
Flow (cfs)
Intensity, I from Fig. 3.4.1 Fort Collins Stormwater Manual
Rational Equation: Q = CiA (Equation 6-1 per MHFD)
DEVELOPED DIRECT RUNOFF COMPUTATIONS
Intensity (in/hr)
Snow Ridge Apartments
A. Poincelot
January 11, 2024
Design
Point Basin Area
(acres)
Runoff CTc (Min)
Date:
Pond No :
A1
100-yr
0.82
5.00 min 2393 ft3
0.52 acres 0.055 ac-ft
Max Release Rate =0.60 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 1273 1.00 0.60 180 1093
10 7.720 1975 1.00 0.60 360 1615
15 6.520 2502 1.00 0.60 540 1962
20 5.600 2865 1.00 0.60 720 2145
25 4.980 3185 1.00 0.60 900 2285
30 4.520 3469 1.00 0.60 1080 2389
35 4.080 3653 1.00 0.60 1260 2393
40 3.740 3827 1.00 0.60 1440 2387
45 3.460 3983 1.00 0.60 1620 2363
50 3.230 4132 1.00 0.60 1800 2332
55 3.030 4264 1.00 0.60 1980 2284
60 2.860 4390 1.00 0.60 2160 2230
65 2.720 4523 1.00 0.60 2340 2183
70 2.590 4638 1.00 0.60 2520 2118
75 2.480 4759 1.00 0.60 2700 2059
80 2.380 4871 1.00 0.60 2880 1991
85 2.290 4980 1.00 0.60 3060 1920
90 2.210 5089 1.00 0.60 3240 1849
95 2.130 5177 1.00 0.60 3420 1757
100 2.060 5270 1.00 0.60 3600 1670
105 2.000 5373 1.00 0.60 3780 1593
110 1.940 5460 1.00 0.60 3960 1500
115 1.890 5561 1.00 0.60 4140 1421
120 1.840 5649 1.00 0.60 4320 1329
*Note: Using the method described in FCSCM Chapter 6 Section 2.3
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
2047-001
Snow Ridge Apartments
Project Number :
Project Name :
Pond 1
Page 1 of 1
2047-001_FAAModified
Pond Stage-Storage Curve
Pond: 1
Project: 2047-001 Snow Ridge Apartments
By: Amanda Poincelot
Date: 02/05/2024
Stage
(FT)
Contour Area
(SF)
Volume
(CU.FT.)
Volume
(AC-FT)
5,036.00 343.94 0.000 0.000
5,036.20 869.80 118.090 0.003
5,036.28 1,043.32 207 0.005 WQCV
5,036.40 1,291.63 334.230 0.008
5,036.60 1,687.08 632.100 0.015
5,036.80 2,095.93 1009.720 0.023
5,037.00 2,996.06 1518.920 0.035
5,037.20 4,245.67 1718.890 0.039
5,037.40 5,334.31 2308.130 0.053
5,037.46 4,061.12 2600 0.060 100-YR DETENTION
5,037.60 1,031.63 3294.490 0.076
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX B
HYDRAULIC CALCULATIONS
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX C
WATER QUALITY/LID COMPUTATIONS
MBMBMB
FO
FO
OH
U
OH
U
OH
U
OH
U
OH
U
OHU OHU
FO
FO
X
X
X
X
G
G
G
G
E
E
E
15
"
S
S
SO
U
T
H
S
H
I
E
L
D
S
S
T
R
E
E
T
DETENTION POND 10.14 ac.
A3
0.06 ac.
OS1
0.15 ac.
A2
0.22 ac.
A1
a3
a2
a1
PROPOSED 12" PVC
PERFORATED
UNDERDRAIN @0.2%
PAVER 1
PAVER 2
PROPOSED 12" PVC
STORM DRAIN @ 0.2%
PROPOSED 12" PVC
PERFORATED
UNDERDRAIN @0.2%
0.09 ac.
OS2
DRAWN BY:
SCALE:
ISSUED:
SNOW RIDGE
APARTMENTS
SHEET NO:
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
E N G I N E E R N GI
EHTRON R N
970.221.4158
northernengineering.com
LID EXHIBIT
J. OBanion
1in=30ft
04/03/2024
PROPOSED STORM SEWER
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
aDESIGN POINT
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
A
LEGEND:
( IN FEET )
1 inch = ft.
Feet03030
30
PERMEABLE PAVER LIMITS
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
On-Site LID Treatment
Project Summary
Total Impervious Area 13,040 sf
Target Treatment Percentage 50%
Minimum Area to be Treated by LID measures 6,520 sf
Permeable Paver Area
Paver 1 Impervious Area 4,586 sf
Run-on area for Paver 1 3,029 sf
Total Pavers Treatment Area 1,557 sf
Impervious Run-on Ratio for Pavers 1 (3:1 Max) 2 :1
Paver 2 Impervious Area 3,360 sf
Run-on area for Paver 2 2,185 sf
Total Pavers Treatment Area 1,175 sf
Impervious Run-on Ratio for Pavers 2 (3:1 Max) 2 :1
Total Treatment Area 7,947 sf
Percent Total Project Area Treated 60.9%
AREA TREATED BY PAVER 1
AREA TREATED BY PAVER 2
*SEE RATIONAL CALCS FOR IMPERVIOUS AREA CALCULATIONS
Project Number:Project:
Project Location:
Calculations By:Date:
Sq. Ft. Acres
A1 9,795 0.22 52%n/a Traditional 173 5,093
A2 6,552 0.15 70%Pavers 1 Pavers 120 4,586
A3 5,895 0.14 57%Pavers 2 Pavers 89 3,360
Total 22,242 0.51 13,040
Sq. Ft. Acres
Pavers 1 6,552 0.15 70% 4,586
A2 Pavers 120
Pavers 2 5,895 0.14 57% 3,360
A3 Pavers 89
Total 12,447 0.29 7,947 209
Treatment via
Traditional
Sq. Ft.Acres
Pond 1 9,795 0.22 52% 5,093
A1 Extended Detention 173
Total 9,795 0.22 5,093
22,242 ft2
13,040 ft2
6,520 ft2
7,947 ft2
60.94%
5,093 ft2
39.06%
100.00%
Tributary Area Weighted %
Impervious
Required
Volume (ft3)
LID Summary per Basin
Subbasin ID Treatment TypeWQ Treatment
Volume per
UD-BMP or
FAA (ft3)
Impervious
Area (ft2)
Water Quality Treatment via LID
LID Summary
AreaBasin ID WQ Treatment Type
Percent
Impervious LID ID
Snow Ridge Apartments
11/9/2023
2047-001
Fort Collins, Colorado
J. Obanion
Total Impervious
Area (ft2)
Percent Impervious Area Treated by Traditional WQ or LID
Total Impervious Area Treated by PICP
50% Required Minimum Area to be Treated by PICP
Total Area of Current Development
Total Impervious Area
Total Impervious Area Treated by Traditional WQ
Percent Impervious Treated by Traditional Water Quality
WQ Treatment Tributary Area Weighted %
Impervious
LID Site Summary - New Impervious Area
Treatment Type Volume per
MHFD-
Percent Impervious Treated by PICP
Subbasin IDImpervious
Area (ft2)
Project Title Date:
Project Number Calcs By:
City
Basins
1
WQCV = Watershed inches of Runoff (inches)52%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100)0.212 in
0.22 ac
0.0040 ac-ft 173 cu. ft.
0.0048 ac-ft 207 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
V =
V (120%) =
A =
Snow Ridge Apartments November 9, 2023
2047-001 J. Obanion
Fort Collins
Pond 1
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 0.
1
0.
2
0.
3
0.
4
0.
5
0.
6
0.
7
0.
8
0.
9
1
WQ
C
V
(
w
a
t
e
r
s
h
e
d
i
n
c
h
e
s
)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
()iii78.019.10.91aWQCV 23 +-=
()iii78.019.10.91aWQCV 23 +-=
AV*
12
WQCV
=
40 hr
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Type of Permeable Pavement Section
A) What type of section of permeable pavement is used?
(Based on the land use and activities, proximity to adjacent
structures and soil characteristics.)
B) What type of wearing course?1
2. Required Storage Volume
A) Effective Imperviousness of Area Tributary to Permeable Pavement, Ia Ia =70.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100)i = 0.700
C) Tributary Watershed Area ATotal = 6,552 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS =1,557 sq ft
(Minimum recommended permeable pavement area = 1699 sq ft)
E) Impervious Tributary Ratio RT =2.2 IMPERVIOUS TRIBUTARY RATIO EXCEEDS 2.0
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 120 cu ft
(WQCV = (0.8 * (0.91 * i3 - 1.19 * i2 + 0.78 * i) / 12) * Area)
G) Is flood control volume being added?
H) Total Volume Needed VTotal =120 cu ft
3. Depth of Reservoir
A) Minimum Depth of Reservoir Dmin =10.0 inches
(Minimum recommended depth is 6 inches)
B) Is the slope of the reservoir/subgrade interface equal to 0%?
2
C) Porosity (Porous Gravel Pavement < 0.3, Others < 0.40) P = 0.30
D) Slope of the Base Course/Subgrade Interface S = 0.002 ft / ft
E) Length Between Lateral Flow Barriers (max = 257.19 ft.) L = 150.0 ft
F) Volume Provided Based on Depth of Base Course V = 280 cu ft
Flat or Stepped: V = P * ((Dmin - 1) / 12) * Area Volume assumes uniform slope & lateral flow barrier spacing
Sloped: V = P * ((Dmin - 6*S*L - 1) / 12) * Area Calculate the volume of each cell individually when this varies.
4. Lateral Flow Barriers
A) Type of Lateral Flow Barriers
B) Number of Permeable Pavement Cells Cells =
5. Perimeter Barrier
A) Is a perimeter barrier provided on all sides of the
pavement system?
(Recommeded for PICP, concrete grid pavement, or for any
no-infiltration section.)
Snow Ridge Apartments
Basin A2
Design Procedure Form: Permeable Pavement Systems (PPS)
J. Obanion
Northern Engineering
November 9, 2023
UD-BMP (Version 3.07, March 2018)
Choose One
No Infiltration
Partial Infiltration Section
Full Infiltration Section
Choose One
YES
NO
Choose One
YES- Flat or Stepped Installation
NO- Sloped Installation
Choose One
Concrete Walls
PVC geomembrane installed normal to flow
N/A- Flat installation
Other (Describe):
Choose One
YES
NO
Choose One
PICP
Concrete Grid Pavement
Pervious Concrete
Porous Gravel
UD-BMP_v3.07-Pavers East, PPS 11/9/2023, 11:48 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
6. Filter Material and Underdrain System
A) Is the underdrain placed below a 6-inch thick layer of
CDOT Class C filter material?
B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2)
C) Distance from the Lowest Elevation of the Storage Volume y = ft
(i.e. the bottom of the base course to the center of the orifice)
7. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is there a minimum 30 mil thick impermeable PVC geomembrane
liner on the bottom and sides of the basin, extending up to the top
of the base course?
B) CDOT Class B Separator Fabric
8. Outlet 1
(Assumes each cell has similar area, subgrade slope, and length
between lateral barriers (unless subgrade is flat). Calculate cells
individually where this varies.)
A) Depth of WQCV in the Reservoir DWQCV =inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice =inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
Snow Ridge Apartments
Design Procedure Form: Permeable Pavement Systems (PPS)
J. Obanion
Northern Engineering
November 9, 2023
Basin A2
Choose One
YES
NO
Choose One
4-inch
6-inch
Choose One
Choose One
YES
NO
Placed above the liner
Placed above and below the liner
N/A
UD-BMP_v3.07-Pavers East, PPS 11/9/2023, 11:48 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Type of Permeable Pavement Section
A) What type of section of permeable pavement is used?
(Based on the land use and activities, proximity to adjacent
structures and soil characteristics.)
B) What type of wearing course?1
2. Required Storage Volume
A) Effective Imperviousness of Area Tributary to Permeable Pavement, Ia Ia =57.0 %
B) Tributary Area's Imperviousness Ratio (I = Ia / 100)i = 0.570
C) Tributary Watershed Area ATotal = 5,895 sq ft
(including area of permeable pavement system)
D) Area of Permeable Pavement System APPS =1,175 sq ft
(Minimum recommended permeable pavement area = 1307 sq ft)
E) Impervious Tributary Ratio RT =2.3 IMPERVIOUS TRIBUTARY RATIO EXCEEDS 2.0
(Contributing Imperviuos Area / Permeable Pavement Ratio)
F) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 89 cu ft
(WQCV = (0.8 * (0.91 * i3 - 1.19 * i2 + 0.78 * i) / 12) * Area)
G) Is flood control volume being added?
H) Total Volume Needed VTotal =89 cu ft
3. Depth of Reservoir
A) Minimum Depth of Reservoir Dmin =10.0 inches
(Minimum recommended depth is 6 inches)
B) Is the slope of the reservoir/subgrade interface equal to 0%?
2
C) Porosity (Porous Gravel Pavement < 0.3, Others < 0.40) P = 0.30
D) Slope of the Base Course/Subgrade Interface S = 0.002 ft / ft
E) Length Between Lateral Flow Barriers (max = 252.52 ft.) L = 150.0 ft
F) Volume Provided Based on Depth of Base Course V = 212 cu ft
Flat or Stepped: V = P * ((Dmin - 1) / 12) * Area Volume assumes uniform slope & lateral flow barrier spacing
Sloped: V = P * ((Dmin - 6*S*L - 1) / 12) * Area Calculate the volume of each cell individually when this varies.
4. Lateral Flow Barriers
A) Type of Lateral Flow Barriers
B) Number of Permeable Pavement Cells Cells =
5. Perimeter Barrier
A) Is a perimeter barrier provided on all sides of the
pavement system?
(Recommeded for PICP, concrete grid pavement, or for any
no-infiltration section.)
Snow Ridge Apartments
Basin A3
Design Procedure Form: Permeable Pavement Systems (PPS)
J.Obanion
Northern Engineering
November 9, 2023
UD-BMP (Version 3.07, March 2018)
Choose One
No Infiltration
Partial Infiltration Section
Full Infiltration Section
Choose One
YES
NO
Choose One
YES- Flat or Stepped Installation
NO- Sloped Installation
Choose One
Concrete Walls
PVC geomembrane installed normal to flow
N/A- Flat installation
Other (Describe):
Choose One
YES
NO
Choose One
PICP
Concrete Grid Pavement
Pervious Concrete
Porous Gravel
UD-BMP_v3.07-Pavers West, PPS 11/9/2023, 11:47 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
6. Filter Material and Underdrain System
A) Is the underdrain placed below a 6-inch thick layer of
CDOT Class C filter material?
B) Diameter of Slotted Pipe (slot dimensions per Table PPs-2)
C) Distance from the Lowest Elevation of the Storage Volume y = ft
(i.e. the bottom of the base course to the center of the orifice)
7. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is there a minimum 30 mil thick impermeable PVC geomembrane
liner on the bottom and sides of the basin, extending up to the top
of the base course?
B) CDOT Class B Separator Fabric
8. Outlet 1
(Assumes each cell has similar area, subgrade slope, and length
between lateral barriers (unless subgrade is flat). Calculate cells
individually where this varies.)
A) Depth of WQCV in the Reservoir DWQCV =inches
(Elevation of the Flood Control Outlet)
B) Diameter of Orifice for 12-hour Drain Time DOrifice =inches
(Use a minimum orifice diameter of 3/8-inches)
Notes:
Basin A3
Snow Ridge Apartments
Design Procedure Form: Permeable Pavement Systems (PPS)
J.Obanion
Northern Engineering
November 9, 2023
Choose One
YES
NO
Choose One
4-inch
6-inch
Choose One
Choose One
YES
NO
Placed above the liner
Placed above and below the liner
N/A
UD-BMP_v3.07-Pavers West, PPS 11/9/2023, 11:47 AM
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX D
EROSION CONTROL REPORT
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY EROSION CONTROL REPORT
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) has been included with the
final construction drawings. It should be noted; however, any such Erosion and Sediment Control Plan serves
only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or
different BMPs from those included may be necessary during construction, or as required by the authorities
having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and
followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to
site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed, or
modified in conjunction with construction activities. It is imperative to appropriately reflect the current site
conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during
construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3,
Chapter 7 – Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing and/or
wattles along the disturbed perimeter, gutter protection in the adjacent roadways, and inlet protection at
existing and proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures,
designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on Sheet CS2 of the Utility Plans. The Final Utility Plans will also
contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion Control Details. In
addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere to, the
applicable requirements outlined in any existing Development Agreement(s) of record, as well as the
Development Agreement, to be recorded prior to issuance of the Development Construction Permit. Also, the
Site Contractor for this project may be required to secure a Stormwater Construction General Permit from the
Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division – Stormwater
Program, before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor
shall develop a comprehensive Storm Water 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.
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX E
USDA SOILS REPORT
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
Maxfield Subdivision Lot 2 - 1509
Shields
Natural
Resources
Conservation
Service
July 7, 2023
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
4—Altvan-Satanta loams, 3 to 9 percent slopes.........................................13
Soil Information for All Uses...............................................................................15
Soil Properties and Qualities..............................................................................15
Soil Erosion Factors........................................................................................15
Wind Erodibility Index..................................................................................15
Wind Erodibility Group.................................................................................18
Soil Qualities and Features.............................................................................21
Hydrologic Soil Group.................................................................................21
References............................................................................................................26
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
Custom Soil Resource Report
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.
Custom Soil Resource Report
7
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
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:507 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
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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
4 Altvan-Satanta loams, 3 to 9
percent slopes
0.7 100.0%
Totals for Area of Interest 0.7 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
Custom Soil Resource Report
11
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
12
Larimer County Area, Colorado
4—Altvan-Satanta loams, 3 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpwf
Elevation: 5,200 to 6,200 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
Altvan and similar soils:55 percent
Satanta and similar soils:35 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Altvan
Setting
Landform:Fans, benches, terraces
Landform position (three-dimensional):Base slope, side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 16 inches: clay loam
H3 - 16 to 31 inches: loam
H4 - 31 to 60 inches: gravelly sand
Properties and qualities
Slope:6 to 9 percent
Depth to restrictive feature:More than 80 inches
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 content:10 percent
Available water supply, 0 to 60 inches: Low (about 5.5 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: B
Ecological site: R067BY008CO - Loamy Slopes
Hydric soil rating: No
Custom Soil Resource Report
13
Description of Satanta
Setting
Landform:Structural 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 9 inches: loam
H2 - 9 to 14 inches: loam
H3 - 14 to 60 inches: loam
Properties and qualities
Slope:3 to 6 percent
Depth to restrictive feature:More than 80 inches
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 content:10 percent
Available water supply, 0 to 60 inches: High (about 10.1 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:6 percent
Ecological site:R067BY002CO - Loamy Plains
Hydric soil rating: No
Larimer
Percent of map unit:4 percent
Ecological site:R067BY002CO - Loamy Plains
Hydric soil rating: No
Custom Soil Resource Report
14
Soil Information for All Uses
Soil Properties and Qualities
The Soil Properties and Qualities section includes various soil properties and
qualities displayed as thematic maps with a summary table for the soil map units in
the selected area of interest. A single value or rating for each map unit is generated
by aggregating the interpretive ratings of individual map unit components. This
aggregation process is defined for each property or quality.
Soil Erosion Factors
Soil Erosion Factors are soil properties and interpretations used in evaluating the
soil for potential erosion. Example soil erosion factors can include K factor for the
whole soil or on a rock free basis, T factor, wind erodibility group and wind erodibility
index.
Wind Erodibility Index
The wind erodibility index is a numerical value indicating the susceptibility of soil to
wind erosion, or the tons per acre per year that can be expected to be lost to wind
erosion. There is a close correlation between wind erosion and the texture of the
surface layer, the size and durability of surface clods, rock fragments, organic
matter, and a calcareous reaction. Soil moisture and frozen soil layers also
influence wind erosion.
15
16
Custom Soil Resource Report
Map—Wind Erodibility Index
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:507 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 Rating Polygons
0
38
48
56
86
134
160
180
220
250
310
Not rated or not available
Soil Rating Lines
0
38
48
56
86
134
160
180
220
250
310
Not rated or not available
Soil Rating Points
0
38
48
56
86
134
160
180
220
250
310
Not rated or not available
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
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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
17
Table—Wind Erodibility Index
Map unit symbol Map unit name Rating (tons per acre
per year)
Acres in AOI Percent of AOI
4 Altvan-Satanta loams, 3
to 9 percent slopes
56 0.7 100.0%
Totals for Area of Interest 0.7 100.0%
Rating Options—Wind Erodibility Index
Units of Measure: tons per acre per year
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Wind Erodibility Group
A wind erodibility group (WEG) consists of soils that have similar properties
affecting their susceptibility to wind erosion in cultivated areas. The soils assigned
to group 1 are the most susceptible to wind erosion, and those assigned to group 8
are the least susceptible.
Custom Soil Resource Report
18
19
Custom Soil Resource Report
Map—Wind Erodibility Group
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40° 34' 6'' N
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10
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4
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N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:507 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 Rating Polygons
1
2
3
4
4L
5
6
7
8
Not rated or not available
Soil Rating Lines
1
2
3
4
4L
5
6
7
8
Not rated or not available
Soil Rating Points
1
2
3
4
4L
5
6
7
8
Not rated or not available
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
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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
20
Table—Wind Erodibility Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
4 Altvan-Satanta loams, 3
to 9 percent slopes
5 0.7 100.0%
Totals for Area of Interest 0.7 100.0%
Rating Options—Wind Erodibility Group
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Lower
Soil Qualities and Features
Soil qualities are behavior and performance attributes that are not directly
measured, but are inferred from observations of dynamic conditions and from soil
properties. Example soil qualities include natural drainage, and frost action. Soil
features are attributes that are not directly part of the soil. Example soil features
include slope and depth to restrictive layer. These features can greatly impact the
use and management of the soil.
Hydrologic Soil Group
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
Custom Soil Resource Report
21
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer at
or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
Custom Soil Resource Report
22
23
Custom Soil Resource Report
Map—Hydrologic Soil Group
44
9
0
7
8
0
44
9
0
7
9
0
44
9
0
8
0
0
44
9
0
8
1
0
44
9
0
8
2
0
44
9
0
8
3
0
44
9
0
8
4
0
44
9
0
8
5
0
44
9
0
7
8
0
44
9
0
7
9
0
44
9
0
8
0
0
44
9
0
8
1
0
44
9
0
8
2
0
44
9
0
8
3
0
44
9
0
8
4
0
44
9
0
8
5
0
491760 491770 491780 491790 491800 491810 491820 491830 491840 491850 491860 491870
491760 491770 491780 491790 491800 491810 491820 491830 491840 491850 491860
40° 34' 6'' N
10
5
°
5
'
5
0
'
'
W
40° 34' 6'' N
10
5
°
5
'
4
5
'
'
W
40° 34' 3'' N
10
5
°
5
'
5
0
'
'
W
40° 34' 3'' N
10
5
°
5
'
4
5
'
'
W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 20 40 80 120
Feet
0 5 10 20 30
Meters
Map Scale: 1:507 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 Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
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
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 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
24
Table—Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
4 Altvan-Satanta loams, 3
to 9 percent slopes
B 0.7 100.0%
Totals for Area of Interest 0.7 100.0%
Rating Options—Hydrologic Soil Group
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
25
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
26
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
27
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
APPENDIX F
SIGNED STORMWATER VARIANCE APPLICATION
1/11/24
1/22/24 x
Site constraints prevent this area from draining internally, lack
of stormwater infrastructure available in adjacent ROW, lower
release to the street than previously, mostly landscape area.
NORTHERNENGINEERING.COM | 970.221.4158 Stormwater Variance Attachment
FORT COLLINS | GREELEY 1 | 1
STORMWATER VARIANCE ATTACHMENT
Additional Information for Variance:
· The closest stormwater infrastructure is an inlet located on Prospect, directly southwest of the site. Alternatives
we considered at the beginning of the project included a pipe from the southwest corner of this site, through
multiple private properties, down to the inlet off Prospect. This would have required several easements through
private properties, if allowed. After discussions with the City, neighbors, and the owner, we determined that
releasing to the flowline of Shields Street would be the better option.
· Site is limited by the existing grades and shallow slopes.
· The high point of the entrance has been moved farther east to reduce offsite flows not being detained. The original
100-yr release rate for Basin OS-1 was 0.4 cfs and the proposed 100-yr release rate is 0.2 cfs.
NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: SNOW RIDGE APARTMENTS
FORT COLLINS | GREELEY APPENDIX
MAP PACKET
DR1 – HISTORIC DRAINAGE EXHIBIT
DR2 – DEVELOPED DRAINAGE EXHIBIT
H Y D
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a2
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CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
1 inch = ft.
Feet02020
20
40 60
EXISTING CONTOUR
PROPERTY BOUNDARY
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
NOTES:
1.REFER TO THE FINAL DRAINAGE REPORT, DATED APRIL 3, 2023 FOR ADDITIONAL
INFORMATION.
A
LEGEND:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
HISTORIC DRAINAGE SUMMARY
Design
Point Basin ID
Total
Area
(acres)
C2 C100 2-Yr Tc
(min)
100-Yr Tc
(min)
Q2
(cfs)
Q100
(cfs)
HA1 ha1 0.241 0.50 0.62 5.80 5.80 0.33 1.49
HA2 ha2 0.428 0.23 0.28 10.09 10.09 0.21 0.98
total Total 0.669 0.32 0.41 6.98 6.98 0.56 2.53
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OS2 0.04 ac.
OS1
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A2
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A1
a3
a2
a1
PROPOSED EMERGENCY
SPILLWAY LOCATION
PROPOSED POND
OUTLET STRUCTURE
PAVER 1
PROPOSED PERMEABLE
INTERLOCKING PAVERS
PAVER 2
PROPOSED PERMEABLE
INTERLOCKING PAVERS
PROPOSED SIDEWALK CHASE
PROPOSED SIDEWALK CHASE
PROPOSED SIDEWALK CHASE
PROPOSED 8'
CONCRETE PAN
PROPERTY BOUNDARY (TYP.)
PROPOSED 2'
CONCRETE PAN
LIMITS OF
CONVENTIONAL
TOPO (TYP.)
OFFSITE CONTOURS PROVIDED
FOR REFERENCE ONLY
PROPOSED UNDERDRAIN OUTFALL
WITH UPTURNED ELBOW
PROPOSED 2' U-CHANNEL
100-YR WSEL100-YR WSEL
20' DRAINAGE
EASEMENT
51' DRAINAGE
EASEMENT
46' DRAINAGE
EASEMENT
7.4' DRAINAGE
EASEMENT
15.5' DRAINAGE
EASEMENT
22' DRAINAGE
EASEMENT
10' UTILITY
EASEMENT
10' UTILITY
EASEMENT
STORM DRAIN LINE B
SEE SHEET ST1
STORM DRAIN LINE A
SEE SHEET ST1
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DR2
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13
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
1 inch = ft.
Feet02020
20
40 60
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
11
NOTES:
1.REFER TO THE FINAL DRAINAGE REPORT, DATED APRIL 3, 2023 FOR ADDITIONAL
INFORMATION.
A
LEGEND:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
Detention Summary
ID Tributary
Area (ac)
Weighted
Percent
Impervious
Extended
Detention
WQV (ac-ft)
LID WQV
(ac-ft)
100-Year
Detention
Vol. (ac-ft)
100-Yr Total
Pond Volume
(ac-ft)
100-Yr
Detention
WSEL (ft)
Final
Release
Rate (cfs)
Pond 1 0.23 77%0.005 N/A 0.055 0.060 5,037.42 0.60
Paver 1 0.15 93%N/A 0.003 N/A N/A N/A N/A
Paver 2 0.14 79%N/A 0.002 N/A N/A N/A N/A
DEVELOPED DRAINAGE SUMMARY
Design Point Basin ID
Total
Area
(acres)
C2 C100 2-Yr Tc
(min)
100-Yr Tc
(min)
Q2
(cfs)
Q100
(cfs)
a1 A1 0.233 0.61 0.77 5.00 5.00 0.41 1.78
a2 A2 0.150 0.74 0.93 5.00 5.00 0.32 1.39
a3 A3 0.135 0.63 0.79 5.62 5.62 0.23 1.06
Offsite Basins
os1 OS1 0.042 0.44 0.44 5.17 5.17 0.05 0.18
os2 OS2 0.095 0.20 0.20 5.57 5.57 0.05 0.18