HomeMy WebLinkAboutIMPALA REDEVELOPMENT - FDP230001 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
FINAL DRAINAGE REPORT
IMPALA REDEVELOPMENT
FORT COLLINS, COLORADO
JANUARY 11, 2023
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FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
COVER SHEET
January 11, 2023
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: FINAL DRAINAGE REPORT FOR
IMPALA REDEVELOPMENT
Dear Staff,
Northern Engineering is pleased to submit this Final Drainage Report for your review. This report
accompanies the Preliminary Development Plan submittal for the proposed Impala Redevelopment.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual
(FCSCM) and serves to document the stormwater impacts associated with the proposed Impala
Redevelopment 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.
SHANE RITCHIE, PE DANNY WEBER, PE
Project Engineer Project Manager
Compliance Statement
I hereby attest that this report for the Preliminary drainage design for Impala Redevelopment 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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TABLE OF CONTENTS
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ....................................................................................... 4
II. DRAINAGE BASINS AND SUB-BASINS ............................................................................................ 6
III. DRAINAGE DESIGN CRITERIA ....................................................................................................... 6
IV. DRAINAGE FACILITY DESIGN ....................................................................................................... 8
V. CONCLUSIONS ........................................................................................................................ 10
VI. REFERENCES ........................................................................................................................... 11
TABLES AND FIGURES
Figure 1 - Vicinity Map ................................................................................................................................ 4
Figure 2 - Aerial Photograph ..................................................................................................................... 5
Figure 3 - Existing Floodplains .................................................................................................................. 5
Table 1 - LID Summary ............................................................................................................................... 8
Table 2 - Detention Summary ................................................................................................................... 9
APPENDICES
APPENDIX A – HYDROLOGIC & POND COMPUTATIONS
APPENDIX B – HYDRAULIC COMPUTATIONS
APPENDIX C – LID & WATER QUALITY EXHIBITS
APPENDIX D – USDA SOILS REPORT
APPENDIX E – FEMA FIRMETTE
MAP POCKET
IMPV – IMPERVIOUS AREA EXHIBIT
HILL CREST PUD
POND SIZING EXHIBIT
C 500 – HISTORIC DRAINAGE EXHIBIT
C 501 – DRAIANGE EXHIBIT
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I. GENERAL LOCATION AND DESCRIPTION
A. LOCATION
1. Vicinity Map
Figure 1 - Vicinity Map
2. The Impala Redevelopment project site is located in the northeast quarter of Section 9, Township 7
North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
3. The project site (refer to Figure 1) is bordered to the north and west by Poudre High School; to the
east by single family homes; and to the south by W Mulberry Street and a future park tract.
4. There is existing storm drainage infrastructure that was constructed with Hill Crest PUD and Impala
Subdivision.
B. DESCRIPTION OF PROPERTY
1. The Impala Redevelopment is comprised of 7.20 acres.
2. The site is currently comprised of single-family and single-family attached housing, as well as
associated parking, roadways, and open space.
3. The project site resides in the City of Fort Collins Canal Importation Master Drainage Basin. The
detention requirements of the subject area were considered in the design of the detention ponds
for Impala Redevelopment and have been factored into the LID requirements, which are described
in further detail throughout this report.
4. The existing on-site runoff generally drains from the Northwest to the Southeast across flat grades
(e.g., 0.50% - 2.00%) to West Mulberry Street.
5. According to the United States Department of Agriculture (USDA) Natural Resources Conservation
Service (NRCS) Soil Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx),
the site consists primarily of Altvan-Satanta loams (Hydrologic Soil Group B) and Nunn clay loam
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(Hydrologic Soil Group C).
Figure 2 - Aerial Photograph
6. The proposed development will consist of four (4) multi-family residential buildings containing 56
units with onsite and street parking, and a clubhouse.
7. The proposed land use is multi-family. This is a permitted use in the Low Density Mixed-Use
Neighborhood District (LMN).
C. FLOODPLAIN
1. No portions of the site are located in a FEMA regulatory floodplain.
Figure 3 - Existing Floodplains
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2. The City of Fort Collins High-Risk Canal Importation 100-year floodplain extends into the SE corner
of the project site and the subject property will be required to comply with Chapter 10 of the City
Municipal code and the development review floodplain checklist.
3. There are no special floodplain considerations required regarding finished floor elevations of
building footprints.
4. A floodplain use permit will be required prior to construction for any work in the floodplain.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
The project area of the Impala Redevelopment is located within the City of Fort Collins Canal
Importation Drainage Basin. Detention requirements for this basin are to detain the difference
between the 100-yr developed inflow rate and the historic 2-year release rate. However, outflow
from this property is limited by the previously established Hill Crest PUD using an orifice restricted
total release rate of 5.8 cubic feet per second and existing storm infrastructure in W Mulberry
Street. An excerpt from the Hill Crest PUD and Pond Sizing Exhibit have been provided in the Map
Pocket for clarification.
B. Sub-Basin Description
1. The outfall for the project site is at the south end of the project site to existing storm infrastructure
in West Mulberry Street.
2. The existing subject site can be defined with 9 distinct drainage basins (see DR1 in the provided
map pocket).
3. The existing site runoff generally drains from Northwest to Southeast towards West Mulberry
Street.
4. The project area receives offsite runoff from the north. This was accounted for in the previous
drainage report for the project and will continue to be accounted for with the proposed design.
III. DRAINAGE DESIGN CRITERIA
A. OPTIONAL PROVISIONS
There are no optional provisions outside of the FCSCM proposed with Impala Redevelopment.
B. STORMWATER MANAGEMENT STRATEGY
The overall stormwater management strategy employed with Impala Redevelopment utilizes the
“Four Step Process” to minimize adverse impacts of urbanization on receiving waters. The following
is a description of how the proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the
stormwater impacts of this development is the site selection itself. By choosing an already
developed site with public storm sewer currently in place, the burden is significantly less than
developing a vacant parcel absent of any infrastructure.
Impala Redevelopment 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 a rain garden or water quality pond. 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
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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 between several rain gardens
between major parking areas of the property and the existing detention ponds installed for Impala
Redevelopment.
Step 3 – Stabilize Drainageways. While not directly applicable to this site, the project will pay one-
time stormwater development fees as well as ongoing monthly stormwater utility fees, both of
which help achieve citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to
industrial and commercial developments.
C. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
1. The subject property is not part of an overall development plan.
2. The project area is constrained to the north and west by Poudre High School; to the east by single
family homes; and to the south by W Mulberry Street and a future park tract.
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 Impala
Redevelopment project. Tabulated data contained in Table 3.4-1 has been utilized for Rational
Method runoff calculations.
2. The Rational Method has been used to estimate peak developed stormwater runoff from drainage
basins within the developed site for the 2-year, 10-year, and 100-year design storms. Peak runoff
discharges determined using this methodology have been used to check the street capacities,
inlets, swales, and storm drain lines.
3. Two separate design storms have been utilized to address distinct drainage scenarios. The first
event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second
event considered is the “Major Storm,” which has a 100-year recurrence interval.
E. HYDRAULIC CRITERIA
1. The drainage facilities proposed with the Impala Redevelopment project are designed in
accordance with criteria outlined in the FCSCM.
2. As stated in Section I.C.1, above, the subject property is not located next to a FEMA designated
floodplain, however, it is located within the Canal Importation High-Risk City Floodplain.
F. FLOODPLAIN REGULATIONS COMPLIANCE
As previously mentioned, this project is not adjacent to a FEMA regulated floodplain, but a portion
of the project falls within a City 100-yr Floodplain and will be subject to these regulations.
G. MODIFICATIONS OF CRITERIA
There are no formal modifications outside of the FCSCM proposed with Impala Redevelopment.
H. CONFORMANCE WITH WATER QUALITY TREATMENT CRITERIA
City Code requires that 100% of runoff from new or modified areas in a project site shall receive
some sort of water quality treatment, of which a majority of the site is receiving. There are several
small areas that flow directly offsite, without treatment. While these small areas will not receive
formal water quality treatment, most areas will still see some treatment as runoff is directed
through the landscaped areas or through extended detention basins before leaving the site. The
existing Pond 2 does not have a multiple stage outlet configuration that includes a water quality
plate. The Pond 2 water quality volume will be provided in Pond 1 to reduce unnecessary
modifications to the Pond 2 outlet structure.
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I. CONFORMANCE WITH LOW IMPACT DEVELOPMENT (LID)
The project site will conform with the requirement to treat a minimum of 75% of new or modified
impervious area using a LID technique. The proposed project site will treat 95% of modified area
with LID, with small portions of the site flowing directly offsite. One rain garden will be used to
capture and treat most of the impervious area on the project site.
J. SIZING OF LID & WQ FACILITIES
Rain Gardens
1. The rain gardens were sized by first determining the required water quality capture volume (WQCV)
for Sub-basin 100.
2. Once the WQCV was identified, the rain garden area was sized for its respective WQCV. The rain
garden will be constructed with a biomedia filter and underdrain. An overflow inlet and spillway
will be provided to provide safe conveyance of storms greater than the WQCV.
Table 1 - LID Summary
LID ID Area (ft2) Weighted %
Impervious
Volume per
UD-BMP (ft3)
Vol. w/ 20%
increase per
FC Manual
(ft3)
Impervious
area (ft2)
Rain Garden 1 111,708 72% 1,798 2,158 80,430
Water Quality
3. The existing Pond 2 does not have a water quality plate and is only constrained by an orifice plate.
4. In leu of modifying Pond 2 to accommodate the required increased water quality in Pond 2 the
required volume is being added to the modified Pond 1.
IV. DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
1. The main objective of the Impala Redevelopment drainage design is to maintain existing drainage
patterns, while not adversely impacting adjacent properties.
2. All storm drains on the site have been designed to convey 100-yr flows.
3. A list of tables and figures used within this report can be found in the Table of Contents at the front
of the document. The tables and figures are located within the sections to which the content best
applies.
4. Drainage for the project site has been analyzed using 9 drainage sub-basins, designated as sub-
basins 100-102, 200, ad OS1-OS5. All sub-basins aside from OS2 are om-site basins. OS2 is an off-
site basin whose flow are collected in Detention Pond 1. Sub-basins OS1, OS3, OS4, and OS5 flow
off-site and are not treated with any form of water quality.
Sub-Basin 100
Sub-basin 100 is comprised of multi-family residential, asphalt drives and parking, and landscaped
areas. The flows from this basin travel via overland flow, curb and gutter, and storm pipe to Rain
Garden 1. From Rain Garden 1, flows are discharged via an underdrain and overflow weir into
Detention Pond 1, which was modified to accommodate the needs of the modified site area.
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Sub-Basin 101
Sub-Basin 101 is composed of existing duplexes, landscaped area, Rain Garden 1, and modified
Detention Pond 1. Flows travel via overland flow to Detention Pond 1.
Sub-Basin 102
Sub-Basin 102 is comprised of existing duplexes, paved drives and parking, and landscaped area.
The flows from this basin are conveyed via overland flow, curb and gutter flow, and concrete pan to
Detention Pond 1.
Sub-Basin 200
Sub-Basin 200 is comprised of existing duplexes, asphalt drives and parking, landscaped areas, and
proposed multi-family. Sub-Basin 200 contains Detention Pond 2. Detention Pond 2 was previously
proposed with Hill Crest P.U.D but is being modified to better suit the needs of the proposed site
including adding a water quality headwall with a proposed water quality plate.
Sub-Basin OS1
Sub-Basin OS1 is composed of multi-family buildings, concrete walks, and landscaped areas. The
flows from this basin travel via overland flow directly offsite and are not treated for water quality or
captured. This follows historic patterns and will still allow for 75% of the modified site area to be
treated with LID.
Sub-Basin OS2
Sub-Basin OS2 Is comprised of existing off-site soccer and baseball fields whose flow is accounted
for in Detention Pond 1’s sizing. Overland flow is the primary method in which these flows travel to
Detention Pond 1. These flows are not treated by LID.
Sub-Basins OS3 and OS4
Sub-Basins OS3 and OS4 are composed of existing and proposed buildings, landscaped area, and
paved roadways. Flows from these basins travel via overland flow and curb and gutter flow to W
Mulberry Street. These flows are not captured nor were they planned to be captured with Hill Crest
P.U.D.
Sub-Basins OS5
Sub-Basin OS5 is composed of a small portion of proposed roadway and sidewalk. These flows
travel directly offsite and are not captured or treated.
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. There are 2 existing detention ponds on the project site, both of which are being modified to
accommodate the additional impervious area being added to the existing site. These ponds will
detain up to the 100-yr storm event and release at or below the previously calculated release rates.
See Table 2 for detention summary.
Table 2 - Detention Summary
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2. LID treatment is being provided within Rain Garden 1. These treat approximately 77% of the
modified site impervious runoff, which is more than the required 75% LID treatment. Please see the
LID exhibit and calculations in Appendix C.
3. Detention allowable release rate is based on computed 100-year historic flow for the overall
property as proposed with Hill Crest P.U.D.
4. The existing ponds are being modified to provide the required increase in detention, LID and water
quality volumes. Pond 1 requires 0.30 acre-feet of detention increase, 0.03 acre-feet of Pond 2
water quality volume. Pond 2 requires 0.03 acre-feet of increase.
5. Stormwater facility Standard Operations Procedures (SOP) will be provided by the City of Fort
Collins in the Development Agreement.
6. Final Design details, and construction documentation shall be provided to the City of Fort Collins
for review prior to Final Development Plan approval.
V. CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
1. The drainage design proposed with Impala Redevelopment complies with the City of Fort Collins
Master Drainage Plan for the Canal Importation Basin.
2. The drainage plan and stormwater management measures proposed with the Impala
Redevelopment project are compliant with all applicable State and Federal regulations governing
stormwater discharge.
B. DRAINAGE CONCEPT
1. The drainage plan and stormwater management measures proposed with the Impala
Redevelopment project are compliant with all applicable State and Federal regulations governing
stormwater discharge.
2. Impala Redevelopment will not impact the Master Drainage Plan recommendations for the City of
Fort Collins Canal Importation Major Drainage Basin.
3. The proposed drainage plan for the Impala Redevelopment complies with the previously proposed
impervious values for the site from the Hill Crest P.U.D plan dated February 1995. The proposed
project will also release at the same rates proposed with Hill Crest P.U.D. For this reason, it is
believed the downstream infrastructure will continue to be sufficient as this portion of the site is
developed.
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VI. REFERENCES
1. 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.
2. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
3. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright- McLaughlin Engineers, Denver, Colorado, Revised April 2008.
4. Final Storm Drainage Report for Hill Crest P.U.D, Stewart & Associates, Fort Collins, Colorado, dated
February 1995.
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FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
APPENDIX A
HYDROLOGIC & POND COMPUTATIONS
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………50%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Residential (Low Density).…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………50%0.55 0.55 0.69
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt/Co
ncrete
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of
Single Family
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
100 2.420 0.54 0.41 0.28 0.00 0.00 0.00 0.00 1.60 51% 0.65 0.65 0.71
101 0.838 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.77 9% 0.31 0.31 0.37
102 1.948 0.49 0.31 0.27 0.00 0.00 0.00 0.00 0.88 54% 0.63 0.63 0.69
200 1.992 0.13 0.07 0.18 0.00 0.00 0.00 0.00 1.68 20% 0.39 0.39 0.45
Offsite Basins
OS1 0.359 0.00 0.06 0.05 0.00 0.00 0.00 0.00 0.30 30% 0.49 0.49 0.55
OS2 4.929 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.93 2% 0.25 0.25 0.31
OS3 0.343 0.11 0.00 0.00 0.00 0.00 0.00 0.00 0.24 32% 0.47 0.47 0.53
OS4 0.287 0.14 0.02 0.00 0.00 0.00 0.00 0.00 0.12 58% 0.65 0.65 0.70
Total On-Site 7.20 1.16 0.79 0.79 0.00 0.00 0.00 0.00 4.46 38% 0.52 0.52 0.57
HISTORIC BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
100 100 0.65 0.71 0 N/A N/A N/A 739 1.24% 0.015 0.59 7.80 1.6 N/A 1.6 1.6 5.0 5.0
101 102 0.63 0.69 52 3.85% 4.0 N/A 404 0.45% 0.015 0.59 4.69 1.4 12.5 5.5 1.4 5.5 5.0
102 200 0.39 0.45 0 N/A N/A N/A 362 0.54% 0.015 0.59 5.13 1.2 N/A 1.2 1.2 5.0 5.0
200 200 0.39 0.45 0 N/A N/A N/A 521 1.23% 0.015 0.59 7.74 1.1 N/A 1.1 1.1 5.0 5.0
os1 OS1 0.49 0.55 71 0.24% 15.5 14.0 0 N/A 0.015 0.59 N/A N/A 10.4 15.5 14.0 10.4 10.4
os2 OS2 0.25 0.31 300 2.06% 21.6 20.1 410 0.91% 0.015 0.59 6.66 1.0 13.9 22.7 21.1 13.9 13.9
os3 OS3 0.47 0.53 92 3.26% 7.6 6.9 102 0.13% 0.015 0.59 2.49 0.7 11.1 8.3 7.6 8.3 7.6
os4 OS4 0.65 0.70 58 2.55% 4.7 4.2 136 1.54% 0.038 0.50 3.06 0.7 11.1 5.4 4.9 5.4 5.0
HISTORIC DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
Offsite Basins
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10 Notes:
1) Add 5000 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 slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Rational Method Equation:
Rainfall Intensity:
100 100 2.42 5.0 5.0 0.65 0.71 2.85 4.87 7.00 4.48 7.66 12.03
101 102 0.84 5.0 5.0 0.31 0.37 2.85 4.87 7.00 0.74 1.27 2.17
102 200 1.95 5.0 5.0 0.63 0.69 2.85 4.87 7.00 3.50 5.98 9.41
200 200 1.99 5.0 5.0 0.39 0.45 2.85 2.85 7.00 2.21 2.21 6.27
os1 OS1 0.36 10.4 10.4 0.49 0.55 2.21 2.21 6.80 0.39 0.39 1.34
os2 OS2 4.93 13.9 13.9 0.25 0.31 1.95 1.95 6.24 2.40 2.40 9.54
os3 OS3 0.34 7.6 7.6 0.47 0.53 2.46 2.46 6.94 0.40 0.40 1.26
os4 OS4 0.29 5.0 5.0 0.65 0.70 2.85 2.85 7.00 0.53 0.53 1.41
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
Offsite Basins
HISTORIC RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
()()()AiCCQf=
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Residential (Low Density).…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………50%0.55 0.55 0.69
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt/Co
ncrete
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of
Single Family
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
100 2.56 0.93 0.38 0.56 0.00 0.00 0.00 0.00 1.07 72% 0.80 0.80 0.86
101 0.84 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.77 9% 0.31 0.31 0.39
102 1.95 0.49 0.31 0.27 0.00 0.00 0.00 0.00 0.88 54% 0.63 0.63 0.79
200 1.99 0.14 0.13 0.20 0.00 0.00 0.00 0.00 1.65 24% 0.43 0.43 0.54
Offsite Basins 0.00
OS1 0.20 0.00 0.04 0.11 0.00 0.00 0.00 0.00 0.05 72% 0.79 0.79 0.99
OS2 4.93 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.93 2% 0.25 0.25 0.31
OS3 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 2% 0.25 0.25 0.31
OS4 0.29 0.14 0.02 0.00 0.00 0.00 0.00 0.00 0.12 58% 0.65 0.65 0.81
OS5 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100% 0.95 0.95 1.00
Pond 1 10.28 1.42 0.69 0.89 0.00 0.00 0.00 0.00 7.27 30% 0.46 0.46 0.58
Total On-Site 7.34 1.56 0.82 1.09 0.00 0.00 0.00 0.00 3.87 47% 0.58 0.58 0.64
DEVELOPED BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
100 100 0.80 0.86 0 N/A N/A N/A 515 1.34% 0.015 0.59 8.09 1.1 N/A 1.1 1.1 5.0 5.0
101 101 0.31 0.39 82 2.38% 10.0 N/A 323 0.52% 0.015 0.59 5.02 1.1 12.3 11.1 1.1 11.1 5.0
102 102 0.63 0.79 0 N/A N/A N/A 362 0.54% 0.015 0.59 5.13 1.2 N/A 1.2 1.2 5.0 5.0
200 200 0.43 0.54 0 N/A N/A N/A 521 1.23% 0.015 0.59 7.74 1.1 N/A 1.1 1.1 5.0 5.0
os1 OS1 0.79 0.99 55 2.47% 3.2 1.2 0 N/A 0.015 0.59 N/A N/A 10.3 3.2 1.2 5.0 5.0
os2 OS2 0.25 0.31 300 2.06% 21.6 20.1 410 0.91% 0.015 0.59 6.66 1.0 13.9 22.7 21.1 13.9 13.9
os3 OS3 0.25 0.31 92 3.26% 10.3 9.5 102 0.13% 0.015 0.59 2.49 0.7 11.1 11.0 10.2 11.0 10.2
os4 OS4 0.65 0.81 58 1.79% 5.3 3.4 136 1.54% 0.038 0.50 3.06 0.7 11.1 6.0 4.1 6.0 5.0
os5 OS5 0.95 1.00 58 1.79% 1.8 1.2 136 1.54% 0.038 0.50 3.06 0.7 11.1 2.5 1.9 5.0 5.0
Offsite Basins
DEVELOPED DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10 Notes:
1) Add 5000 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 slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Rational Method Equation:
Rainfall Intensity:
100 100 2.56 5.0 5.0 0.80 0.86 2.85 4.87 9.95 5.85 9.99 21.94
101 101 0.84 5.0 5.0 0.31 0.39 2.85 4.87 9.95 0.74 1.27 3.23
102 102 1.95 5.0 5.0 0.63 0.79 2.85 4.87 9.95 3.50 5.98 15.26
200 200 1.99 5.0 5.0 0.43 0.54 2.85 2.85 9.95 2.44 2.44 10.65
os1 OS1 0.20 5.0 5.0 0.79 0.99 2.85 2.85 9.95 0.46 0.46 1.99
os2 OS2 4.93 13.9 13.9 0.25 0.31 1.95 1.95 6.82 2.40 2.40 10.50
os3 OS3 0.04 10.2 10.2 0.25 0.31 2.21 2.21 7.72 0.02 0.02 0.09
os4 OS4 0.29 5.0 5.0 0.65 0.81 2.85 2.85 9.95 0.53 0.53 2.32
os5 OS5 0.01 5.0 5.0 0.95 1.00 2.85 2.85 9.95 0.04 0.04 0.13
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
Offsite Basins
DEVELOPED RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
()()()AiCCQf=
Pond No :1
1
100-yr
0.86 Pond 2 WQCV 1220 ft3
5.00 min Pond 1 Detention 13042 ft3
2.56 acres 0.33 ac-ft
Max Release Rate =2.80 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 6572 1.00 2.80 840 5732
10 7.720 10198 1.00 2.80 1680 8518
15 6.520 12919 1.00 2.80 2520 10399
20 5.600 14795 1.00 2.80 3360 11435
25 4.980 16446 1.00 2.80 4200 12246
30 4.520 17912 1.00 2.80 5040 12872
35 4.080 18863 1.00 2.80 5880 12983
40 3.740 19762 1.00 2.80 6720 13042
45 3.460 20567 1.00 2.80 7560 13007
50 3.230 21334 1.00 2.80 8400 12934
55 3.030 22014 1.00 2.80 9240 12774
60 2.860 22668 1.00 2.80 10080 12588
65 2.720 23355 1.00 2.80 10920 12435
70 2.590 23949 1.00 2.80 11760 12189
75 2.480 24570 1.00 2.80 12600 11970
80 2.380 25151 1.00 2.80 13440 11711
85 2.290 25712 1.00 2.80 14280 11432
90 2.210 26274 1.00 2.80 15120 11154
95 2.130 26730 1.00 2.80 15960 10770
100 2.060 27212 1.00 2.80 16800 10412
105 2.000 27740 1.00 2.80 17640 10100
110 1.940 28189 1.00 2.80 18480 9709
115 1.890 28711 1.00 2.80 19320 9391
120 1.840 29167 1.00 2.80 20160 9007
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
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 Increase
Fort Collins, CO
1914-001
Impala Redevelopment
Project Number :
Project Name :
1/11/2023
11:19 AM
1914-001_FAA_Pond 1 (north)Northern Engineering Services
Max. Elev. Description cu. ft. acre ft
5,082.71 Invert 0.00 0.00
5,083.00 43.56 0.00
5,083.90 WQ- POND 2 1,306.80 0.03
5,084.00 1,742.40 0.04
5,085.00 10,018.80 0.23
5,086.00 27,442.80 0.63
5,086.26 100YR-WSE 34,848.00 0.80
5,086.26 Spillway 34,848.00 0.80
Detention Pond 1
STAGE STORAGE CURVE
Contour Cummalitive Volume
Pond Stage Storage Curve
Impala Redevelopment
January 11, 2023
Project:
Date:
Calculations By:S. Ritchie
1
Pond No :2
1
100-yr
1.00
5.00 min 1338 ft3
0.12 acres 0.03 ac-ft
Max Release Rate =0.04 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 9.950 358 1.00 0.04 11 348
10 7.720 556 1.00 0.04 21 535
15 6.520 704 1.00 0.04 32 673
20 5.600 806 1.00 0.04 42 764
25 4.980 896 1.00 0.04 53 844
30 4.520 976 1.00 0.04 63 913
35 4.080 1028 1.00 0.04 74 955
40 3.740 1077 1.00 0.04 84 993
45 3.460 1121 1.00 0.04 95 1026
50 3.230 1163 1.00 0.04 105 1058
55 3.030 1200 1.00 0.04 116 1084
60 2.860 1236 1.00 0.04 126 1109
65 2.720 1273 1.00 0.04 137 1136
70 2.590 1305 1.00 0.04 147 1158
75 2.480 1339 1.00 0.04 158 1182
80 2.380 1371 1.00 0.04 168 1203
85 2.290 1401 1.00 0.04 179 1223
90 2.210 1432 1.00 0.04 189 1243
95 2.130 1457 1.00 0.04 200 1257
100 2.060 1483 1.00 0.04 210 1273
105 2.000 1512 1.00 0.04 221 1291
110 1.940 1536 1.00 0.04 231 1305
115 1.890 1565 1.00 0.04 242 1323
120 1.840 1590 1.00 0.04 252 1338
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
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 Increase
Fort Collins, CO
1914-001
Impala Housing Catalyst
Project Number :
Project Name :
1/11/2023
11:24 AM
1914-001_FAA_Pond 2 (south)
FAA
Northern Engineering Services
Max. Elev. Description cu. ft. acre ft
5,080.10 Invert 0.00 0.00
5,081.00 2,178.00 0.05
5,082.00 8,276.40 0.19
5,082.46 100YR-WSE 12,196.80 0.28
5,082.46 Spillway 12,196.80 0.28
Pond Stage Storage Curve
Contour Cummalitive Volume
Calculations By:S. Ritchie
STAGE STORAGE CURVE
Detention Pond 2
Project:Impala Redevelopment
Date:January 11, 2023
1
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
APPENDIX B
HYDRAULIC COMPUTATIONS
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
APPENDIX C
LID & WATER QUALITY EXHIBITS
Project Number:Project:
Project Location:
Calculations By:Date:
Sq. Ft. Acres
100 111,708 2.56 72%Rain Garden 1 Rain Garden 2,158 80,430
101 36,520 0.84 9%n/a n/a 0 3,287
200 (NEW or
Modified)11,638 0.27
100%n/a n/a 877 11,638
OS1 10,135 0.20 72% n/a n/a 0 7,297
OS5 590 0.01 100% n/a n/a 0 590
Total 170,591 1.31 103,242
LID Summary
Project Number:Project:
Project Location:
Calculations By:Date:
LID Summary
per LID
Structure
Sq. Ft. Acres
Rain Garden 1 111,708 2.56 72%101 Rain Garden 1,798 2,158 80,430
Total 111,708 2.56 2,158 80,430
170,591 ft2
103,242 ft2
10,584 ft2
77,431 ft2
80,430 ft2
77.90%
LID Summary
AreaBasin ID Treatment TypePercent
Impervious LID ID
Impala Redevelopment
1/11/2023
1914-001
Fort Collins, Colorado
S. Ritchie
Total
Impervious
Area (ft2)
Required
Volume (ft3)
LID Summary per Basin
Area Weighted
%
Impervious
1914-001
Fort Collins, Colorado
S. Ritchie
Impervious
Area (ft2)
Vol. w/20%
Increase per
Fort Collins
Manual (ft3)
Impala Redevelopment
1/11/2023
Subbasin ID Treatment TypeLID ID Volume per
UD-BMP (ft3)
Total Treated Area
Percent Impervious Treated by LID
O1-O7
75% Requried Minimum Area to be Treated
LID Site Summary - New Impervious Area
Total Area of Current Development
Total Impervious Area
Total Impervious Area without LID Treatment
XSSTTTTVAULT
F.O
.XXXXXXXXXSX
SIRR
IRRIRR SSSFODSSDSTSTSTSTXXXX
T T
POND 1WHWHWHWHUPXXOS1102OS2101OS3OS4101OS1102OS3OS4OS2200200DETENTIONPOND 2100100RAIN GARDEN 1RAIN GARDEN 2OS5OS5DRAWN BY:SCALE:ISSUED:IMPALAREDEVELOPMENTSHEET NO:FORT COLLINS: 301 North Howes Street, Suite 100, 80521GREELEY: 820 8th Street, 80631ENGINEERNGIEHTRONRN970.221.4158northernengineering.comLID EXHIBITC. Ungerman1in=120ft01/11/23PROPOSED STORM SEWERPROPOSED CURB & GUTTERPROPERTY BOUNDARYPROPOSED INLETADESIGN POINTDRAINAGE BASIN LABELDRAINAGE BASIN BOUNDARYALEGEND:( IN FEET )1 inch = ft.Feet0120120120RAIN GARDEN LIMITSSTORMTECH CHAMBERSFOR DRAINAGE REVIEW ONLYNOT FOR CONSTRUCTIONTotal Area of Current Development168,153ft2Total Impervious Area92,745ft2Total Impervious Area without LID Treatment10,584ft2O1-O775% Requried Minimum Area to be Treated69,559ft2Total Treated Area71,493ft2Percent Impervious Treated by LID77.09%
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =72.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.720
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.23 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 111,708 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =2,118 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 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 5.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =1609 sq ft
D) Actual Flat Surface Area AActual =1668 sq ft
E) Area at Design Depth (Top Surface Area)ATop =2693 sq ft
F) Rain Garden Total Volume VT=2,181 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 =cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
S. Ritchie
Northern Engineering
January 11, 2023
Impala Redevelopment
Rain garden 1
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07_Rain Garden 1, RG 1/11/2023, 11:11 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:
Design Procedure Form: Rain Garden (RG)
S. Ritchie
Northern Engineering
January 11, 2023
Impala Redevelopment
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
UD-BMP_v3.07_Rain Garden 1, RG 1/11/2023, 11:11 AM
Project:
Calc. By:
Date:
2.56 <-- INPUT from impervious calcs
24%<-- INPUT from impervious calcs
0.24 <-- CALCULATED
40 hours <-- from FCSM Figure 5.4-1
1.00 <-- from FCSM Figure 5.4-1
0.13 <-- MHFD Vol. 3 Equation 3-1
0.03 <-- FCSCM Equation 7-2
1,220 <-- Calculated from above
1.19 <-- INPUT from stage-storage table
0.11 <-- CALCULATED from Equation EDB-3
dia (in) =2/8
number of columns=1.00
number of rows =2.00
number of holes =2.00
Area Per Row =0.05
Total Outlet Area (in2) =0.10 <-- CALCULATED from total number of holes
Drain Time =
Drain Time Coefficient =
WQCV (ac-ft) =
WQ Depth (ft) =
Area Required Per Row, a (in 2) =
Circular Perforation Sizing
WQCV (cu. ft.) =
WQCV (watershed inches) =
Required Storage & Outlet Works
Basin Area (acres) =
Basin Percent Imperviousness =
Basin Imperviousness Ratio =
WATER QUALITY POND DESIGN CALCULATIONS
Water Quality Pond 1
Impala Redevelopment
S. Ritchie
January 11, 2023
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
Project Number:
Project Name:
Project Location:
Pond No:Calc. By:S.Ritchie
Orifice Dia (in):9 3/16
Orifice Area (sf):0.46
Orifice invert (ft):5,082.71
Orifice Coefficient:0.65
Elevation Stage (ft)Velocity (ft/s)Flow Rate (cfs)Comments
5,082.71 0.00 0.00 0.00
5,086.26 3.55 9.82 4.50 <-100 Year Elev.
Orifice Rating Curve
ORIFICE RATING CURVE
1494-001
Impala Redevelopment
Fort Collins, Colorado
1
Orifice Design Data
Detention Pond 1
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
APPENDIX D
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, ColoradoNatural
Resources
Conservation
Service
March 29, 2022
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
3—Altvan-Satanta loams, 0 to 3 percent slopes.........................................13
35—Fort Collins loam, 0 to 3 percent slopes..............................................15
74—Nunn clay loam, 1 to 3 percent slopes.................................................16
76—Nunn clay loam, wet, 1 to 3 percent slopes.........................................17
Soil Information for All Uses...............................................................................20
Soil Properties and Qualities..............................................................................20
Soil Erosion Factors........................................................................................20
K Factor, Whole Soil....................................................................................20
Soil Qualities and Features.............................................................................23
Hydrologic Soil Group.................................................................................23
References............................................................................................................28
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.
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.
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9
Custom Soil Resource Report
Soil Map
449231044923604492410449246044925104492560449261044926604492710449231044923604492410449246044925104492560449261044926604492710489700 489750 489800 489850 489900 489950 490000
489700 489750 489800 489850 489900 489950 490000
40° 35' 7'' N 105° 7' 18'' W40° 35' 7'' N105° 7' 4'' W40° 34' 53'' N
105° 7' 18'' W40° 34' 53'' N
105° 7' 4'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,100 if printed on A portrait (8.5" x 11") 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 16, Sep 2, 2021
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.
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Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0 to 3
percent slopes
9.3 44.7%
35 Fort Collins loam, 0 to 3 percent
slopes
1.9 9.0%
74 Nunn clay loam, 1 to 3 percent
slopes
6.3 30.4%
76 Nunn clay loam, wet, 1 to 3
percent slopes
3.3 16.0%
Totals for Area of Interest 20.8 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
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11
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
3—Altvan-Satanta loams, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpw2
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: Prime farmland if irrigated
Map Unit Composition
Altvan and similar soils:45 percent
Satanta and similar soils:30 percent
Minor components:25 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Altvan
Setting
Landform:Terraces, benches
Landform position (three-dimensional):Side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 10 inches: loam
H2 - 10 to 18 inches: clay loam
H3 - 18 to 30 inches: loam
H4 - 30 to 60 inches: gravelly sand
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
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 content:10 percent
Available water supply, 0 to 60 inches: Low (about 5.4 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
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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 18 inches: loam
H3 - 18 to 60 inches: loam
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
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 content:10 percent
Available water supply, 0 to 60 inches: High (about 10.1 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:10 percent
Ecological site:R067BZ902CO - Loamy Plains
Hydric soil rating: No
Larim
Percent of map unit:10 percent
Ecological site:R067BY063CO - Gravel Breaks
Hydric soil rating: No
Stoneham
Percent of map unit:5 percent
Ecological site:R067BZ902CO - Loamy Plains
Hydric soil rating: No
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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: 135 to 160 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, stream terraces
Landform position (three-dimensional):Interfluve, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Pleistocene or older alluvium 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
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 content:12 percent
Maximum salinity:Nonsaline to very slightly saline (0.1 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
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Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:10 percent
Landform:Stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY002CO - Loamy Plains
Hydric soil rating: No
Vona
Percent of map unit:5 percent
Landform:Interfluves
Landform position (three-dimensional):Side slope, interfluve
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY024CO - Sandy Plains
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
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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
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 content:7 percent
Maximum salinity:Nonsaline to very slightly saline (0.1 to 2.0 mmhos/cm)
Sodium adsorption ratio, maximum:0.5
Available water supply, 0 to 60 inches: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: R067BY042CO - Clayey Plains
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:R067BY042CO - Clayey Plains
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:R067BY002CO - Loamy Plains
Hydric soil rating: No
76—Nunn clay loam, wet, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpxq
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
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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
Nunn, wet, and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn, Wet
Setting
Landform:Stream terraces, alluvial fans
Landform position (three-dimensional):Base slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Alluvium
Typical profile
H1 - 0 to 10 inches: clay loam
H2 - 10 to 47 inches: clay
H3 - 47 to 60 inches: gravelly loam
Properties and qualities
Slope:1 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat poorly drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately low to
moderately high (0.06 to 0.60 in/hr)
Depth to water table:About 24 to 36 inches
Frequency of flooding:NoneRare
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2w
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: C
Ecological site: R067BZ902CO - Loamy Plains
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit:6 percent
Ecological site:R067BZ902CO - Loamy Plains
Hydric soil rating: No
Dacono
Percent of map unit:3 percent
Ecological site:R067BY042CO - Clayey Plains
Hydric soil rating: No
Mollic halaquepts
Percent of map unit:1 percent
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Landform:Swales
Hydric soil rating: Yes
Custom Soil Resource Report
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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.
K Factor, Whole Soil
Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by
water. Factor K is one of six factors used in the Universal Soil Loss Equation
(USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the
average annual rate of soil loss by sheet and rill erosion in tons per acre per year.
The estimates are based primarily on percentage of silt, sand, and organic matter
and on soil structure and saturated hydraulic conductivity (Ksat). Values of K range
from 0.02 to 0.69. Other factors being equal, the higher the value, the more
susceptible the soil is to sheet and rill erosion by water.
"Erosion factor Kw (whole soil)" indicates the erodibility of the whole soil. The
estimates are modified by the presence of rock fragments.
Factor K does not apply to organic horizons and is not reported for those layers.
20
21
Custom Soil Resource Report
Map—K Factor, Whole Soil
449231044923604492410449246044925104492560449261044926604492710449231044923604492410449246044925104492560449261044926604492710489700 489750 489800 489850 489900 489950 490000
489700 489750 489800 489850 489900 489950 490000
40° 35' 7'' N 105° 7' 18'' W40° 35' 7'' N105° 7' 4'' W40° 34' 53'' N
105° 7' 18'' W40° 34' 53'' N
105° 7' 4'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,100 if printed on A portrait (8.5" x 11") 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
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
Not rated or not available
Soil Rating Lines
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
Not rated or not available
Soil Rating Points
.02
.05
.10
.15
.17
.20
.24
.28
.32
.37
.43
.49
.55
.64
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 16, Sep 2, 2021
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
22
Table—K Factor, Whole Soil
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0
to 3 percent slopes
.28 9.3 44.7%
35 Fort Collins loam, 0 to 3
percent slopes
.43 1.9 9.0%
74 Nunn clay loam, 1 to 3
percent slopes
.28 6.3 30.4%
76 Nunn clay loam, wet, 1 to
3 percent slopes
.24 3.3 16.0%
Totals for Area of Interest 20.8 100.0%
Rating Options—K Factor, Whole Soil
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable)
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.
Custom Soil Resource Report
23
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
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
24
25
Custom Soil Resource Report
Map—Hydrologic Soil Group
449231044923604492410449246044925104492560449261044926604492710449231044923604492410449246044925104492560449261044926604492710489700 489750 489800 489850 489900 489950 490000
489700 489750 489800 489850 489900 489950 490000
40° 35' 7'' N 105° 7' 18'' W40° 35' 7'' N105° 7' 4'' W40° 34' 53'' N
105° 7' 18'' W40° 34' 53'' N
105° 7' 4'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,100 if printed on A portrait (8.5" x 11") 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 16, Sep 2, 2021
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
26
Table—Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0
to 3 percent slopes
B 9.3 44.7%
35 Fort Collins loam, 0 to 3
percent slopes
C 1.9 9.0%
74 Nunn clay loam, 1 to 3
percent slopes
C 6.3 30.4%
76 Nunn clay loam, wet, 1 to
3 percent slopes
C 3.3 16.0%
Totals for Area of Interest 20.8 100.0%
Rating Options—Hydrologic Soil Group
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
27
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
28
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
29
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
APPENDIX E
FEMA FIRMETTE
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOOD
HAZARD AREAS
Without Base Flood Elevation (BFE)
Zone A, V, A99
With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areas
of 1% annual chance flood with average
depth less than one foot or with drainage
areas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard information is derived directly from the
authoritative NFHL web services provided by FEMA. This map
was exported on 3/30/2022 at 2:25 PM and does not
reflect changes or amendments subsequent to this date and
time. The NFHL and effective information may change or
become superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximate
point selected by the user and does not represent
an authoritative property location.
1:6,000
105°7'30"W 40°35'15"N
105°6'53"W 40°34'47"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY
FINAL DRAINAGE REPORT: IMPALA REDEVELOPMENT
APPENDIX
MAP POCKET
IMPV – IMPERVIOUS AREA EXHIBIT
HILL CREST PUD EXHIBIT
POND SIZING EXHIBIT
C 500 – HISTORIC DRAINAGE EXHIBIT
C 501 – DRAINAGE EXHIBIT
XXXX X XXXTXXXXXGGEESTWSS9S WFEEE ETXXTXXXXXGGEEST9
CCCCCSWFEEE ETROOFTOPCONCRETEASPHALTGRAVELSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)5,2714,2496,115090%100%100%50%0TOTALS63,68715,108TOTAL=EXISTINGPROPOSEDP:\1914-001\DWG\DRNG\1914-001_IMPV.DWG
IMPALA REDEVELOPMENTFORT COLLINS COLORADOFort Collins: 301 N. Howes St., Ste. 100, 80521Greeley: 820 8th Street, 80631ENGINEERNGIEHTRONRNPHONE: 970.221.4158www.northernengineering.comDESCRIPTIONEXISTING VS. PROPOSEDIMPERVIOUS AREADRAWN BYC. UngermanDATEJANUARY 11, 2023PROJECT1914-001DR-A1DRAWINGSCALE1" = 50'ARTIFICIALTURF050%04,744LANDSCAPE48,0522%9614,2496,115ROOFTOPCONCRETEASPHALTGRAVELSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)8,5635,4936,121090%100%100%50%0TOTALS63,68720,191TOTAL=ARTIFICIALTURF050%07,706LANDSCAPE43,9682%8705,4936,1215,173NET CHANGE FROM EXISTING=
XXXXXXXXXXXXXXXXXXXXXXXXXX X X X
DDDSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTXXXXXXXXX X
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9
7 XXXXXXOS1102200OS2101OS3100101OS1102UD200OS3OS4OS2EXISTING 10'EASEMENTIMPALA CIRCLESOUTH IMPALA DRIVEWEST MULBERRY STREETIMPALA CIRCLEOLIVE STREETDETENTIONPOND 2RAINGARDEN 1DETENTIONPOND 1EXISTING 36"STORM DRAINEXISTING 15"STORM DRAINPROPOSED 6'CONCRETE PANPROPOSED 2'CONCRETE PANPROPOSED OUTLETSTRUCTUREEXISTING 2'CONCRETE PANPROPOSED 2'SIDEWALK CULVERTPROPOSEDRIPRAP RUNDOWNPROPOSEDSTORM DRAINPROPOSED 4'CONCRETE RUNDOWNAND FORBAYPROPOSEDSTORM DRAINPROPOSED STORMDRAINOS4PROPOSED 2'CONCRETE PAN100EXISTINGHEADWALLEXISTINGHEADWALLOS5OS55088 (NAVD88)5087 (NAVD88)5086 (NAVD88)
5085 (NAVD88)
5084 (NAVD88)
5083 (NAVD88)
5082 (NAVD88)
5081 (NAVD88)
5080 (NAVD88)CITY OF FORT COLLINS100-YR FLOODWAYCITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGECITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGEX-SEC #2303 - 5085.14' (NAVD88)
X-SEC #1983 - 5081.71' (NAVD88)PROPOSEDWATERQUALITYHEADWALLPROPOSEDOVERFLOWWEIRC 501DRAINAGE EXHIBIT18CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOUDIG, GRADE, OR EXCAVATE FOR THE MARKING OFUNDERGROUND MEMBER UTILITIES.CALL UTILITY NOTIFICATION CENTER OFCOLORADOKnow what'sbelow.before you dig.CallRNORTH( IN FEET )1 inch = ft.Feet0505050100150PROPOSED CONTOURPROPOSED STORM SEWERPROPOSED SWALEEXISTING CONTOURPROPOSED CURB & GUTTERPROPERTY BOUNDARYPROPOSED INLETADESIGN POINTFLOW ARROWDRAINAGE BASIN LABELDRAINAGE BASIN BOUNDARYPROPOSED SWALE SECTION11NOTES:1.REFER TO THE PRELIMINARY DRAINAGE REPORT, DATED OCTOBER 19, 2022 BYNORTHERN ENGINEERING FOR ADDITIONAL INFORMATION.2.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROM THE CITY OFFORT COLLINS AND PAY ALL APPLICABLE FLOODPLAIN USE PERMIT FEES PRIOR TOCOMMENCING ANY CONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES,GRADING, FILL, DETENTION, PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHIN THE CANALIMPORTATION FLOODPLAIN AND FLOODWAY. ALL ACTIVITIES WITHIN THEFLOODPLAIN ARE SUBJECT TO THE REQUIREMENTS OF CHAPTER 10 OF THE FORTCOLLINS MUNICIPAL CODE.3.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS, WALKWAYS,DRIVEWAYS, WALLS, AND PARKING AREAS IS PROHIBITED IN THE FLOODWAYUNLESS NO-RISE CONDITIONS ARE MET, PER SECTION 10-45 OF CITY CODE. ANYCONSTRUCTION ACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDEA NO-RISE CERTIFICATION PREPARED BY A PROFESSIONAL ENGINEER LICENSED INCOLORADO.4.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY OR PERMANENT) IS NOTALLOWED IN THE FLOODWAY.ALEGEND:FOR DRAINAGE REVIEW ONLYNOT FOR CONSTRUCTIONSheetIMPALA REDEVELOPMENT 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 CO
N
S
T
R
U
C
T
I
O
N
REVIEW SE
T
of 18Rational Flow Summary | Developed Basin Flow RatesBASINIDTOTAL AREA(acres)Tc2(min)Tc100(min)C2C100Q2(cfs)Q100(cfs)1002.565.05.00.730.795.3420.161010.845.05.00.310.390.743.231021.955.05.00.630.793.5015.262001.995.05.00.430.542.4410.65OS10.205.05.00.790.990.461.99OS24.9313.913.90.250.312.4010.50OS30.0410.210.20.250.310.020.09OS40.295.05.00.650.810.532.32OS50.015.05.00.951.000.040.13XXXXXXXXXXXXXXXXXXXXXXXXXX X X X
DDSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTXXXXXXXXX X
42 8
9
7
B B B B BBBBBBBBBBBBBB B B B BBB BBBBBBBB B B B B B BBBBBBBBBBBBBBBBBBBBBBB B BBBBBBBBBBBBBBBBBBBB B B BB
XXXXXXOS1102200OS2101OS3100101OS1102UDTTTEE EVAULTELEC200OS3OS4OS2EXISTING 10'EASEMENTIMPALA CIRCLESOUTH IMPALA DRIVEWEST MULBERRY STREETIMPALA CIRCLEOLIVE STREETDETENTIONPOND 2RAINGARDEN 1DETENTIONPOND 1EXISTING 36"STORM DRAINEXISTING 15"STORM DRAINPROPOSED 6'CONCRETE PANPROPOSED 2'CONCRETE PANPROPOSED OUTLETSTRUCTUREEXISTING 2'CONCRETE PANPROPOSED 2'SIDEWALK CULVERTPROPOSEDRIPRAP RUNDOWNPROPOSEDSTORM DRAINPROPOSED 4'CONCRETE RUNDOWNAND FORBAYPROPOSEDSTORM DRAINPROPOSEDSTORM DRAINPROPOSED STORMDRAINOS4PROPOSED 2'CONCRETE PAN100EXISTINGHEADWALLEXISTINGHEADWALLOS5OS55088 (NAVD88)5087 (NAVD88)5086 (NAVD88)
5085 (NAVD88)
5084 (NAVD88)
5083 (NAVD88)
5082 (NAVD88)
5081 (NAVD88)
5080 (NAVD88)CITY OF FORT COLLINS100-YR FLOODWAYCITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGECITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGEX-SEC #2303 - 5085.14' (NAVD88)
X-SEC #1983 - 5081.71' (NAVD88)PROPOSEDWATERQUALITYHEADWALLPROPOSEDOVERFLOWWEIRHEADWALLRELOCATED WITHSAME RELEASERATE (4.50 CFS) ATLOWER ELEVATIONPond No :21100-yr1.005.00 min1338ft30.12 acres 0.03ac-ftMax Release Rate =0.04 cfsA =Tc =Project Location :Design PointC =Design StormDETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDFInput VariablesResultsRequired Detention Volume IncreaseFort Collins, CO1914-001Impala Housing CatalystProject Number :Project Name :XXTXXXGGEEST9
CCCCCIRRIRRIRRSWF
ROOFTOPCONCRETEASPHALTGRAVELSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)8,5635,4936,121090%100%100%50%0TOTALS63,68720,191TOTAL=ARTIFICIALTURF050%07,706LANDSCAPE43,9682%8705,4936,1215,173NET CHANGE FROM EXISTING=5.79 CFS - 4.50 CFS = 1.29 CFS0.12 ACRES / 4.42 ACRES = 3 %3 % of 1.29 CFS = 0.04 CFS
XXX XXXXXX XX X
XXX
XXX
X X X X X X
XXXXXXXXXXXXXXXXXXXXXWW WW WWWWWWWWWWWWWWWWWWWWWWWWWW
WWWWWWWWWWWWWWWWWWWWWWWWWWWWWW WW
WWWWWWWWWWWWWWWWWWWW WW WWWWWWWWWW WWWWWWWWWW
WWWWIRRIRRIRR IRR IRR
IRR
IRR
IRR
D
D
D
ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST STSTXXXXXXXXXXTTTTT45088 (NAVD88)28975087 (NAVD88)5086 (NAVD88)5085 (NAVD88)5084 (NAVD88)5083 (NAVD88)5082 (NAVD88)5081 (NAVD88)5080 (NAVD88)POND 1
POND 2
100
101
OS1
IMPALA CIRCLE
SOUTH IMPALA DRIVEWEST MULBERRY STREET
IMPALA CIRCLE
OLIVE STREET
EXISTING 15"
STORM DRAIN
EXISTING 36"
STORM DRAIN
EXISTING 2'
CONCRETE PAN
EXISTING HEADWALL &
OVERFLOW WEIR
EXISTING HEADWALL &
OVERFLOW WEIR
CITY OF FORT COLLINS
100-YR FLOODWAY
CITY OF FORT COLLINS
100-YR HIGH-RISK
FLOOD FRINGE
CITY OF FORT COLLINS
100-YR HIGH-RISK
FLOOD FRINGE
OS1
200
OS2
100
OS4
102
101
OS3
X-SEC #2303 - 5085.14' (NAVD88)X-SEC #1983 - 5081.71' (NAVD88)C 610DRAINAGE EXHIBITHISTORIC29
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.
Feet05050
50
100 150
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 JANUARY 11, 2023 BY NORTHERN
ENGINEERING FOR ADDITIONAL INFORMATION.
2.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROM THE CITY OF
FORT COLLINS AND PAY ALL APPLICABLE FLOODPLAIN USE PERMIT FEES PRIOR TO
COMMENCING ANY CONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES,
GRADING, FILL, DETENTION, PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,
LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHIN THE CANAL
IMPORTATION FLOODPLAIN AND FLOODWAY. ALL ACTIVITIES WITHIN THE
FLOODPLAIN ARE SUBJECT TO THE REQUIREMENTS OF CHAPTER 10 OF THE FORT
COLLINS MUNICIPAL CODE.
3.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS, WALKWAYS,
DRIVEWAYS, WALLS, AND PARKING AREAS IS PROHIBITED IN THE FLOODWAY
UNLESS NO-RISE CONDITIONS ARE MET, PER SECTION 10-45 OF CITY CODE. ANY
CONSTRUCTION ACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDE
A NO-RISE CERTIFICATION PREPARED BY A PROFESSIONAL ENGINEER LICENSED IN
COLORADO.
4.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY OR PERMANENT) IS NOT
ALLOWED IN THE FLOODWAY.
A
LEGEND:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
SheetIMPALA REDEVELOPMENTThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETof 30
XXXXXXXXXXXXXXXXXXXXXXXXXX X X X
DDDSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTXXXXXXXXX X
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7 XXXXXXOS1102200OS2101OS3100101OS1102UD200OS3OS4OS2EXISTING 10'EASEMENTIMPALA CIRCLESOUTH IMPALA DRIVEWEST MULBERRY STREETIMPALA CIRCLEOLIVE STREETDETENTIONPOND 2RAINGARDEN 1DETENTIONPOND 1EXISTING 36"STORM DRAINEXISTING 15"STORM DRAINPROPOSED 6'CONCRETE PANPROPOSED 2'CONCRETE PANPROPOSED OUTLETSTRUCTUREEXISTING 2'CONCRETE PANPROPOSED 2'SIDEWALK CHASEPROPOSEDRIPRAP RUNDOWNPROPOSEDSTORM DRAINPROPOSED 4'CONCRETE RUNDOWNAND FORBAYPROPOSEDSTORM DRAINPROPOSED STORMDRAINOS4PROPOSED 2'CONCRETE PAN100EXISTINGHEADWALLEXISTINGHEADWALLOS5OS55088 (NAVD88)5087 (NAVD88)5086 (NAVD88)
5085 (NAVD88)
5084 (NAVD88)
5083 (NAVD88)
5082 (NAVD88)
5081 (NAVD88)
5080 (NAVD88)CITY OF FORT COLLINS100-YR FLOODWAYCITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGECITY OF FORT COLLINS100-YR HIGH-RISKFLOOD FRINGEX-SEC #2303 - 5085.14' (NAVD88)
X-SEC #1983 - 5081.71' (NAVD88)PROPOSEDOVERFLOWWEIRC 611DRAINAGE EXHIBIT30CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOUDIG, GRADE, OR EXCAVATE FOR THE MARKING OFUNDERGROUND MEMBER UTILITIES.CALL UTILITY NOTIFICATION CENTER OFCOLORADOKnow what'sbelow.before you dig.CallRNORTH( IN FEET )1 inch = ft.Feet0505050100150PROPOSED CONTOURPROPOSED STORM SEWERPROPOSED SWALEEXISTING CONTOURPROPOSED CURB & GUTTERPROPERTY BOUNDARYPROPOSED INLETADESIGN POINTFLOW ARROWDRAINAGE BASIN LABELDRAINAGE BASIN BOUNDARYPROPOSED SWALE SECTION11NOTES:1.REFER TO THE FINAL DRAINAGE REPORT, DATED JANUARY 11, 2023 BY NORTHERNENGINEERING FOR ADDITIONAL INFORMATION.2.THE DEVELOPER SHALL OBTAIN A FLOODPLAIN USE PERMIT FROM THE CITY OFFORT COLLINS AND PAY ALL APPLICABLE FLOODPLAIN USE PERMIT FEES PRIOR TOCOMMENCING ANY CONSTRUCTION ACTIVITY (BUILDING OF STRUCTURES,GRADING, FILL, DETENTION, PONDS, BIKE PATHS, PARKING LOTS, UTILITIES,LANDSCAPED AREAS, FLOOD CONTROL CHANNELS, ETC.) WITHIN THE CANALIMPORTATION FLOODPLAIN AND FLOODWAY. ALL ACTIVITIES WITHIN THEFLOODPLAIN ARE SUBJECT TO THE REQUIREMENTS OF CHAPTER 10 OF THE FORTCOLLINS MUNICIPAL CODE.3.CONSTRUCTION OF NEW STRUCTURES, HARD SURFACE PATHS, WALKWAYS,DRIVEWAYS, WALLS, AND PARKING AREAS IS PROHIBITED IN THE FLOODWAYUNLESS NO-RISE CONDITIONS ARE MET, PER SECTION 10-45 OF CITY CODE. ANYCONSTRUCTION ACTIVITIES IN THE REGULATORY FLOODWAY MUST ALSO INCLUDEA NO-RISE CERTIFICATION PREPARED BY A PROFESSIONAL ENGINEER LICENSED INCOLORADO.4.STORAGE OF EQUIPMENT AND MATERIALS (TEMPORARY OR PERMANENT) IS NOTALLOWED IN THE FLOODWAY.ALEGEND:FOR DRAINAGE REVIEW ONLYNOT FOR CONSTRUCTIONSheetIMPALA REDEVELOPMENT 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 CO
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of 30Rational Flow Summary | Developed Basin Flow RatesBASINIDTOTAL AREA(acres)Tc2(min)Tc100(min)C2C100Q2(cfs)Q100(cfs)1002.565.05.00.730.795.3420.161010.845.05.00.310.390.743.231021.955.05.00.630.793.5015.262001.995.05.00.430.542.4410.65OS10.205.05.00.790.990.461.99OS24.9313.913.90.250.312.4010.50OS30.0410.210.20.250.310.020.09OS40.295.05.00.650.810.532.32OS50.015.05.00.951.000.040.13Max. Elev. Description cu. ft. acre ft5,080.10Invert0.000.005,081.002,178.000.055,082.008,276.400.195,082.46100YR-WSE12,196.800.285,082.46Spillway12,196.800.28Pond Stage Storage CurveContourCummalitive VolumeCalculations By:S. RitchieSTAGE STORAGE CURVEDetention Pond 2Project:Impala RedevelopmentDate:January 11, 2023Max. Elev. Description cu. ft. acre ft5,082.71Invert0.000.005,083.0043.560.005,083.90WQ- POND 21,306.800.035,084.001,742.400.045,085.0010,018.800.235,086.0027,442.800.635,086.26100YR-WSE34,848.000.805,086.26Spillway34,848.000.80Detention Pond 1STAGE STORAGE CURVEContourCummalitive VolumePond Stage Storage CurveImpala RedevelopmentJanuary 11, 2023Project:Date:Calculations By:S. Ritchie