HomeMy WebLinkAboutDrainage Reports - 01/31/2017City of Fort Collins Approved
Approved by:
Date: '41/1017
FINAL DRAINAGE REPORT
Lot 13, the Amended Plat of Lots 13 and 14,
Interchange Business Park
Prepared for:
R4 Architects
226 Remington Street, Unit 3
Fort Collins, CO 80524
970-224-0630
Prepared by:
Interwest Consulting Group
1218 West Ash, Suite A
Windsor, Colorado 80550
(970)460-8488
January 12, 2017
Job Number 1284-069-00
' INTERWEST CON SULTI N G GROUP
January 12, 2017
tMr. Dan Mogen
City of Fort Collins Stonmwater
700 Wood Street
Fort Collins, CO 80522-0580
' RE: Final Drainage Report for Lot 13, the Amended Plat of Lots 13 and 14, Interchange
Business Park
Dear Dan,
I am pleased to submit for your review and approval, this Final Drainage Report for the Lot 13,
' the Amended Plat of Lots 13 and 14, Interchange Business Park development. I certify that this
report for the drainage design was prepared in accordance with the criteria in the City of Fort
Collins Storm Drainage Manual with variance request as noted.
City comments dated October 8, 2016 from the City of Fort Collins Stormwater Engineering
Department have been addressed in this report.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
c
Erika Schneider, P.E.
Colorado Professional
Engineer No. 41777
Reviewed By:
Michael Oberlanc
Colorado Professional
Engineer No. 34288
' 1218 WEST ASH, SUITE C WINDSOR. COLORADO 80550
M. 970.674.3300 • ILK. 970.674.3303
TABLE OF CONTENTS
TABLEOF CONTENTS ............................................................................................................ iii
1. GENERAL LOCATION AND DESCRIPTION................................................................ 1
1.1 Location...........................................................................................................................1
' 1.2 Description of Property................................................................................................. 1
2. DRAINAGE BASINS AND SUB-BASINS.......................................................................... 2
2.1 Major Basin Description................................................................................................ 2
2.2 Sub -Basin Description................................................................................................... 2
3. DRAINAGE DESIGN CRITERIA...................................................................................... 2
3.1 Regulations......................................................................................................................2
3.2 Directly Connected Impervious Area (DCIA) Discussion .......................................... 2
3.3 Development Criteria Reference and Constraints...................................................... 3
3.4 Hydrologic Criteria........................................................................................................ 4
3.5 Hydraulic Criteria.......................................................................................................... 5
' 3.6 Floodplain Regulations Compliance............................................................................. 5
3.7 Modifications of Criteria............................................................................................... 6
' 4. DRAINAGE FACILITY DESIGN....................................................................................... 6
4.1 General Concept............................................................................................................. 6
' 4.2 Specific Flow Routing.................................................................................................... 7
4.3 Drainage Summary........................................................................................................ 7
I 5. CONCLUSIONS....................................................................................................................7
5.1 Compliance with Standards.......................................................................................... 7
5.2 Drainage Concept........................................................................................................... 8
6. REFERENCES...................................................................................................................... 8
IAPPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D
APPENDIX E
APPENDIX F
APPENDIX G
VICINITY MAP, DRAINAGE AND EROSION CONTROL PLAN,
AND FLOODPLAIN PLAN
HYDROLOGIC COMPUTATIONS
HYDRAULIC COMPUTATIONS
WATER QUALITY AND LID CALCULATIONS, APPROVED
VARIANCE REQUEST
BOXELDER INFORMATION (SWMM MODEL)
FLOODPLAIN INFORMATION AND CITY OF FORT COLLINS
FLOODPLAIN REVIEW CHECKLIST FOR 100% SUBMITTALS
SOILS INFORMATION, FIGURES AND TABLES
iii
GENERAL LOCATION AND DESCRIPTION
' 1.1 Location
' The proposed project is located in the southeast corner of the intersection of Interstate 25
and State Highway 14. More specifically it is located in the northwest quarter of Section
15, Township 7 North, Range 68 West of the 61h P.M., City of Fort Collins, County of
' Larimer, State of Colorado. Please refer to the vicinity map in Appendix A.
The project is located southeast of the Southeast Frontage Road and northwest of the
Boxelder Creek. It is Lot 13 of Interchange Business Park Amended Lots 13 and 14. Lot
14 is located to the west. Lot 12 of Interchange Business Park is located to the east.
1.2 Description of Property
' The property is approximately 1.2 acres in size and will consist of a single building and
' modifications to the existing parking and drives. The site will be served by an existing
private drive.
' The north portion of the land currently slopes to the north at about 1 % and contains the
existing drive and parking. The remainder of the site slopes towards the Boxelder Creek
' at about 4%. The site is currently vacant except for an existing parking lot located in the
northwest portion of the site and the existing drive connecting Lots 12, 13 and 14. The
' majority of the ground cover is asphalt, gravel and exposed dirt.
' The existing soil type on -site consists of Nunn clay loam (60%), classified as Type C,
Larimer-Stoneham complex (36%), classified as Type B and Paoli fine sandy loam (4%),
classified as Type A by the Natural Resources Conservation Service. The area of
' development is within the Type C soils located in the north half of the site. Soil,
information is located in Appendix G.
The Boxelder FEMA floodway is located on the south portion of the property and the
flood fringe is on the northern portion of the property (FEMA FIRM Panel
08069C0983H, effective on May 2, 2012). The "City of Fort Collins Floodplain Review
Checklist for 100% Submittals" and other floodplain information are included in
Appendix F.
1
I
2. DRAINAGE BASINS AND SUB -BASINS
' 2.1 Major Basin Description
The proposed development lies within the Boxelder Creek/Cooper Slough Master
Drainage Basin.
2.2 Sub -basin Description
tThe existing site discharges directly into Boxelder Creek.
' 3. DRAINAGE DESIGN CRITERIA
' 3.1 Regulations
This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage
' Design Criteria Manual' specifications. Where applicable, the criteria established in the
"Urban Storm Drainage Criteria Manual" (UDFCD), developed by the Denver Regional
' Council of Governments, has been used.
' 3.2 Directly Connected Impervious Area (DCIA) Discussion
Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process
for receiving water protection that focuses on reducing runoff volumes, treating the water
quality capture volume (WQCV), stabilizing drainageways and implementing long-term
' source controls. The Four Step Process applies to the management of smaller, frequently
occurring events.
' Step 1: Employ Runoff Reduction Practices
To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement
' Low Impact Development (LID) strategies, including Minimizing Directly Connected
Impervious Areas (MDCIA).
' Runoff basins B and C will be routed through a rain garden thereby reducing runoff from
' impervious surfaces over a permeable area to slow runoff and increase the time of
concentration and promote infiltration.
1 2
I
' Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow
Release
The rain garden helps reduce total runoff by allowing the water to infiltrate and allow
' sediments to settle while incorporating a slow release.
' Step 3: Stabilize Drainageways
Natural Drainageways are subject to bed and bank erosion due to increases in frequency,
duration, rate and volume of runoff during and following development. Because the site
will drain to a proposed rain garden, bank stabilization is unnecessary with this project.
The rain garden will help improve water quality and attenuate flows thereby improving
' stabilization in receiving water ways. No changes to the main Boxelder Creek channel
floodway are proposed.
' Step 4. Implement Site Specific and Other Source Control BMPs
' The proposed development will provide the LID rain garden feature which will eliminate
pollution that had previously been exposed during weathering and runoff processes. The
proposed project will proactively control pollutants at their source by preventing pollution
' rather than removing contaminants once they have entered the stormwater system as
compared to historic conditions.
' 3.3 Development Criteria Reference and Constraints
' The runoff from this site has been routed as much as possible to conform to the
requirements of the City Stormwater Department. Today, the north portion of the site has
been developed with approximately 8,000 sf of existing pavement draining north and
directly to the ROW untreated. With the development, the design leaves approximately
' 6,000 sf of pavement draining north (Basin A). It is not feasible to change this drainage
pattern and an Alternate ComplianceNariance is requested from the 100% area treatment
standard. Water quality will be met through the use of a rain garden that will accept
runoff from basins B and C of the developed site. Please refer to Appendix D for the
Stormwater Alternative ComplianceNariance Application.
3
Runoff reduction practices (LID techniques) are also required. 75% of all newly
developed areas must be treated by LID techniques. The project has a total 22,400 sf of
impervious area. Using the rain garden LID technique, 16,737 sf of impervious area
(75%) will be treated. This meets the 75% requirement.
Please refer to Appendix D for rain garden and LID calculations and LID table.
3.4 Hydrologic Criteria
The City of Fort Collins Rainfall Intensity -Duration —Frequency Curves (Figure RA-16 of
the City of Fort Collins Storm Drainage Design Criteria Manual) is used for all
hydrologic computations associated with this project. Runoff computations were
prepared for the 10-year minor and 100-year major storm frequency utilizing the rational
method. All hydrologic calculations associated with the basins are included in Appendix
B of this report. Please refer to Appendix A for the Drainage and Erosion Control Plan
depicting drainage basins and design points.
Water quality volume was calculated using the method recommended in the "Urban
Storm Drainage Criteria Manual". Water quality capture volume calculations are located
in Appendix D. Basins B and C are treated in the rain garden. It was assumed that Lot 13
was 90% impervious in these calculations (to allow for any potential future additions).
The site is located in the City of Fort Collins Boxelder/Cooper Slough master basin. It is
located in Master Basin 87 (46 acres). This basin was analyzed as 73% impervious for
the 100-year developed condition in the master plan.
Interwest has studied the impact of the proposed project on the peak flow in Boxelder
' Creek. For this study, it was assumed that Lot 13 was 90% impervious (to allow for any
potential future additions). This study has verified that the project area, even with an
increased imperviousness, does not impact the overall peak flow in Boxelder Creek, and
therefore the site does not need detention (required in the Master Plan to keep the
' Boxelder Creek peak flow at or below existing conditions). Three models were used to
show that our site does not increase the peak flow of Boxelder Creek:
4
1. Existing Conditions City Model: File name: Box_Elder_100.INP
2. Current Conditions City Model with SWMM Basin 87 split into two basins (SB87
and SB87(GRIT)) where Basin SB87(GRIT) is the project site with current
impervious conditions (15%) modeled: File name: Box_Elder_100 (CE),INP
3. Proposed Conditions City Model with SWMM Basin 87 split into two basins
(SB87 and SB87(GRIT)) where Basin SB87(GRIT) is the project site with
proposed impervious conditions (90%) modeled: File name: Box_Elder_100
(PROP),INP
The results of the SWMM model show that the existing peak flow of Boxelder Creek in
this area (SWMM conveyance ID 925L) is 1463.97 cfs at a time of 12 hours and 47
minutes. By splitting Basin 87 and adding the new imperviousness of the site into the
model, the 100-year flow of this node remains 1463.97 cfs at 12 hours and 47 minutes.
Therefore, the proposed condition does not increase the peak of Boxelder Creek (because
of the time of concentration of the site versus that of the sub -basin and channel). Please
refer to Appendix E for printouts of the models.
Since the proposed release of the site does not increase the peak flow of Boxelder Creek,
detention is not required.
3.5 Hydraulic Criteria
All hydraulic calculations are prepared in accordance with the City of Fort Collins
Drainage Criteria. All calculations are included in Appendix C of this. The roof drain
storm systems was analyzed using StormCAD software. The curb cut was analyzed using
F1owMaster software.
3.6 Floodplain Regulations Compliance
The site is within a FEMA regulated, 100-year Boxelder Creek flood fringe and floodway
(Panel 08069C1003G). A completed "City of Fort Collins Floodplain Review Checklist
for 100% Submittals" has been included in Appendix F of this report. Chapter 10 "Flood
Prevention and Protection' of the City Code has been referred to for this report.
61
4.
Construction activities will occur within the flood fringe and include installation of
sidewalk, curb and gutter and asphalt parking, utility work and landscaping. A
Floodplain Use Permit Application for this work performed in the Boxelder Creek flood
fringe will be required.
The building is located outside of the floodplain boundary. Survey will be required prior
to construction proving that the building is located outside of the floodplain. The lowest
floor (including basement or crawl space) and HVAC will not be required to be elevated
above the regulatory flood protection elevation.
The rain garden and Swale, landscaping and storm pipe system to the rain garden will be
constructed within the FEMA regulated, 100-year Boxelder Creek floodway. A City
Floodplain Use Permit and "No Rise Certification" will be required for work in the
floodway. The current design will leave the floodway area either at existing grade or in a
minor "cut" condition.
3.7 Modifications of Criteria
A variance is required for the water quality treatment. The approved variance is included
in Appendix D. The SWMM model verifies that this lot does not need detention.
DRAINAGE FACILITY DESIGN
4.1 General Concept
The south portion of the proposed development and building will be collected and
conveyed to the proposed rain garden on the southwest portion of the site where it will be
treated before being released over a level spreader into the Boxelder Creek. The north
portion of the development will continue existing conditions and flow northeast into the
existing drive aisle where it will also eventually discharge into Boxelder Creek from a
low point in the SE Frontage Road.
2
t4.2 Specific Flow Routing
' A summary of the drainage patterns within each basin is provided in the following
paragraphs.
Basin A is 0.27 acres and includes the northwest portion of the site. This basin contains
the existing parking area (which will be repaved and is smaller than the existing parking
area), six proposed parking spaces and proposed sidewalks. Runoff from this basin will
' follow existing conditions and continue to sheet to the drive aisle and then flow to
Boxelder Creek from the SE Frontage Road.
' Basin B is 0.43 acres and includes the building, drive and new parking area. The building
roof will be collected in roof drains and be conveyed to the rain garden located southwest
' of the building. The remainder of the basin will sheet flow south to the same rain garden.
' Basin C is 0.48 acres and includes remaining southern portion of the site and contains the
rain garden.
' Water will be treated for water quality in the rain garden located north of the Boxelder
Creek in the floodway. Water will be released to the south to the Boxelder Creek with a
' level spreader. Please refer to Appendix D for the rain garden design.
t4.3 Drainage Summary
' Drainage facilities located outside of the right of way (including the proposed roof storm
drain system and rain garden) will be maintained by the property owners.
' S. CONCLUSIONS
' 5.1 Compliance with Standards
' All computations that have been completed within this report are in compliance with the
City of Fort Collins Storm Drainage Design Criteria Manual.
7
' 5.2 Drainage Concept
' The proposed drainage concepts presented in this report and on the construction plans
adequately provide for stormwater quantity and quality treatment of proposed impervious
' areas. Conveyance elements will be designed during the final report to pass required
flows and to minimize future maintenance.
tThe
design minimizes impacts to other utilities and properties and maintains the existing
'
drainage flow paths as much as possible. The design will effectively control damage
from The BMPs
from storm runoff originating the site. recommended are sufficient to
reduce runoff peaks, volumes and pollutant loads from the impervious areas of the site.
If, at the time of construction, groundwater is encountered, a Colorado Department of
'
Health Construction Dewatering Permit will be required.
' 6. REFERENCES
t 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March,
1986.
' 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated January 2016, and Volume 3 dated November
' 2010 (revised November 2015).
' 3. ICON Engineer, Inc., "Hydrologic Analysis of the Boxelder Creek/Cooper Slough
Watershed", dated April 2014.
1 8
L
APPENDIX A
VICINITY MAP
DRAINAGE AND EROSION CONTROL PLAN,
FLOODPLAIN PLAN
A
LOT 13, THE AMENDED PLAT OF LOTS 13 AND 14,
INTERCHANGE BUSINESS PARK
SCALE: 1 '=1000'
PROPOSED DRAINAGE SUMMARY TABLE
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21553 sq. ft.
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larp A
Ousting lmperlous Area Unteated
7,896 sq. ft.
Proposed Area Impervious Untreated
6,20E sq. ft.
Variance Requested
lisle ll E
Impervious Area Treated
16,737 acre/sq. ft.
ImpemlousAreaTmatedhy LID
16,737 acre/sq. ft.
% Impervious Area Treated
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% Impervious Aua Treated by UD
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20 10 O 20 40
SCALE'. 1"= 20'
NOTES:
1 SEE LANDSCAPE PLAN FOR PLANTINGS THROUGHOUT THE SITE
2. THE TOP OF FOUNDAMON ELEVATION SHOWN IS HIGHER THAN
THE MINIMUM ELEVATION REQUIRED FOR PROTECTION FROM THE
I O&YR STORM.
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NOTES
\
I. NO STORAGE OF MATERIALS OR EQUIPMENT IN THE FLOODWAY.
2, PORTIONS OF THIS PROPERTY ARE LOCATED IN THE FEMA REGULATORY I OOYEAR
\ O I \\
FLOODPLAIN AND ALL DEVELOPMENT MUST SATISFY REQUIREMENTS OF CHAPTER 10 OF CITY COOL
3 PRIOR
FLOODPLAINTOBE (INNINGSE ANY WORK IN
PERMIT IS REQUIRED E FLOOD FRINGE (FILL LANDSCAPING. PAVEMENT, ETC)
1
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�' fits 4. PRIOR TO BEGINNING ANY WORK IN THE FLOODWAY (STORMWATER PIPE SYSTEM. RAIN GARDEN.
LANDSCAPING. WATER OUALTFY. ETC.) AN APPROVED NORISE CERTIFICATE IS REQUIRED.
5. THE BUILDING CORNER AND THE FLOODPLAIN BOUNDARY MUST BE STAKED PRIOR TO
CONSTRUCTION. THE FLOODPLAIN ADMINISTRATOR MUST VERIFY THE SEPARATION BEFORE AND
�\ \ AFTER CONSTRUCTION.
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APPENDIX B
HYDROLOGIC COMPUTATIONS
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Interwest Consulting Group
RUNOFF COEFFICIENTS & %IMPERVIOUS
LOCATION: GRIT
PROJECT NO: 12R4-069-00
COMPUTATIONS BY: es
DATE: 111152016
Recommended Runoff Coefficients from Table RO-11 of City of Fort Collins Stormwater Code, Volume I
Recommended % Impervious from Table RO-3 Urban Storm Drainage Criteria Manual, Volume I
coefficient
Impervious
C
0.95
100
0.95
96
0.95
90
0.50
40
0.20
0
Type C Soils Runoff
Streets, parking lots (asphalt)
Sidewalks (concrete)
Roofs
Gravel
Heavy Soil (Flat, c29/6)
SUBBASW
DESIGNATION
TOTAL
AREA
(ac.)
TOTAL
AREA
(salt)
ROOF
AREA
(sq.10
PAVED
AREA
(sq.0)
GRAVEL
AREA
(so-fl)
SIDEWALK
AREA
(W'I)
LANDSCAPE
AREA
(W.")
RUNOFF
COEFF.
(C)
%
hpewoous
REMARKS
Eh"
Lot
1.18
51,345
0
7.896
0
0
3,225
0.16
15
Proposed
Lot
1.18
5/,345
7.756
12,079
0
2,565
7.975
0,45
42
tEouations
- Calculated C coefficients & % Impervious are area weighted
C = L (Ci Ai) / At
' Ci = runoff coefficient for specific area, Ai
Ai = areas of surface with runoff coefficient of Ci
n = number of different surfaces to consider
At = total area over which C is applicable; the sum of all APs
11.15.16 FC FLOW-GRR.As
Interest Consulting Group
RUNOFF COEFFICIENTS & %IMPERVIOUS
LOCATION: GRIT
PROJECT NO: 1284-069.00
COMPUTATIONS BY: es
DATE: 1111512016
Recommended Runoff Coefficients from Table BOA 1 of City of Fort Collins Stormwater Code, Volume I
Recommended % Impervious from Table RO-3 Urban Storm Drainage Criteria Manual, Volume I
Type C Soils
Streets, parking lots (asphalt)
Sidewalks (concrete)
Roofs
Gravel or Pavers
Landscape Areas (Flat, heavy)
Landscape Areas (Steep, heavy)
Runoff
%
SUBBASW
DESIGNATION
TOTAL
AREA
W)
TOTAL
AREA
IN.111
ROOF
AREA
(N.9)
PAVED
AREA
IN.91
GRAVEL
AREA
(N.fl)
CONCRETE
AREA
(N.fl)
LANDSCAPE
AREA
IN.91
RUNOFF
COEFR
(C)
%
Ynpe s
REMARKS
A
0.27
11,553
0
5,843
0
565
5,345
0.60
54
NORTH PORTION OF LOT
a
0,43
1aa22
7.756
6.436
0
2000,
2,630
Day
e1
BUILDING AND PARKING
c
0,48
20.970
0
0
0
0
20.970
o.20
0
SOUTH PORTION OF LOT RAIN GARDEN
TOTAL
1.18
51.345
7,756
12,079
2,565
7.975
e45
42
B.O
0.91
39792
]756
6,436
2,000
23.600
0.51
39
Treated In Rain Garden
ROOF
O.tB
),)56
LJ56
0
0
0
0
0.95
90
In roof drain storm s stem
Eouations
Total Impervious A 6,208
Total Impervious B & C 16,192
- Calculated C coefficients 8 % Impervious are area weighted
Total Impervious Site 22,400
C. L(Ci Ai)I At
CI . runoff coefficient for specific area, Ai
Al = areas of surface with runoff coefficient of Ci
n . number of different surfaces to consider
At = total area over which C is applicable; the sum of all Ats
11-15-16 FC FLOW GRR.s6
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HYDRAULIC CALCULATIONS
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Ev;
Worksheet for 4 ft Curb Cut (Basin B)
Project Description
Flow Element:
Rectangular Weir
Friction Method:
Manning Formula
Solve For:
Discharge
Input Data
Headwater Elevation:
0.50
ft
Crest Elevation:
0.00
ft
Tailwater Elevation:
0.00
ft
Weir Coefficient
3,33
us
Crest Length:
4.00
ft
Number of Contractions:
0
Results
Discharge:
4.71
ft'/s
Headwater Height Above Crest:
0.50
ft
Tailwater Height Above Crest:
0.00
ft
Flow Area.
2.00
ft'
Velocity:
2.35
ft/S
Wetted Perimeter.
5.00
ft
Top Width:
4.00
ft
Cross Section for 4 ft Curb Cut (Basin B)
Project Description
Flow Element:
Rectangular Weir
Solve For:
Discharge
Section Data
Discharge.
4.71
ft/s
Headwater Elevation:
0.50
ft
Crest Elevation.
0.00
ft
Tailwater Elevation:
0.00
ft
Weir Coefficient:
3.33
us
Crest Length.
4.00
ft
Number of Contractions:
0
T
0.50 ft
1
CDO It
Worksheet for Trapezoidal Channel - 1
Protect Description
Flow Element: Trapezoidal Channel
Friction Method: Manning Formula t0v
Solve For: Discharge
Input Data
Roughness Coefficient. 0 035
Channel Slope 0,00600 ft/ft
Normal Depth: 0.50 It
Left Side Slope: 0.25 ft/ft (H:V)
Right Side Slope: 0.25 ft/ft (H:V) x 33
Bottom Width: 4-00 ft �G�$
Results Di
Dschharay
ge: 374 � � � , � �'+ � fN/s
Flow Area. 2 06 ft'
Wetted Perimeter. 5.03 It
Top Width. 4.25 ft
Critical Depth: 0.30 ft
Critical Slope: 0.03096 fUft
Velocity: 1.81 f /s
Velocity Head. 0.05 ft
Specific Energy: 0.55 ft
Froude Number: 0.46
Flow Type: Subcritical
GVF Input Data
Downstream Depth 0.00 It
Length: 0.00 ft
Number Of Steps. 0
GVF Output Data
Upstream Depth:
0.00
ft
Profile Description:
N/A
Headloss:
0.00
ft
Downstream Velocity.
0.00
f /s
Upstream Velocity
0.00
f /s
Normal Depth.
0.50
It
Critical Depth:
0.30
ft
Channel Slope:
0.00600
ft/ft
' Worksheet'for Trapezoidal Channel - 1
cMicarsiope: 0:03096 mrt
Cross Section for Trapezoidal Channel - 1
Project Description
Flow Element:
Friction Method
Solve For.
Section Data
Roughness Coefficient:
Channel Slope.
Normal Depth:
Left Side Slope:
Right Side Slope:
Bottom Width:
Discharge:
4.00 It ---I
Trapezoidal Channel
Manning Formula
Discharge
0.035
0.00600
0.50
0.25
0.25
4.00
3.74
05011
ft/ft
ft
ft/ft (H:V)
tt/fl (H:V)
ft
ft3/s
WATER QUALITY
AND
LID CALCULATIONS,
APPROVED VARIANCE REQUEST
Design Procedure Form: Rain Garden (RG) II
'
Sheet 1 of 2
Designer:
ES
Company:
INTERWEST
'
Dale:
Project:
September 21, 2016
GRIT
Location:
RAIN GARDEN (BASIN S AND C)
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, la
to =
90.0
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = 1,100)
1 =
0.900
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time
WQCV =
0.32
watershed inches
(WQCV= 0.8' (0.91" i'- 1.19" 1'+0.78" i)
D) Contributing Watershed Area (including rain garden area)
Area =
39.792
sq It
E) Water Quality Capture Volume (WQCV) Design Volume
Vwa:v =
1.065
cU It
Vol = (WQCV / 12)' Area
F) For Watersheds Outside of the Denver Region, Depth of
or =
in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region,
Vwocv orHLH =
cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume
Vwocvusee =
cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)
Dwmv -
12
in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)
Z =
4.00
ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area
AM,,, =
710
sq It
D) Actual Flat Surface Area
Ai,, eN =
749
sq It
E) Area at Design Depth (Top Surface Area)
Ara, =
1382
sq ft
F) Rain Garden Total Volume
V,=
1,066
cu it
(VY= ((AT, + Aftw) / 2)' Depth)
3. Growing Media
Choose One
Q 18" Rain
Garden Growing Media
Other (Explain);
4. Underdrain System
A) Are underdrain5 provided?
C11aose One
O YES
Q NO
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage
y =
N/A
It
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours
Vol,, =
N/A
cu ft
iii) Orifice Diameter, 3/8" Minimum
Do =
N/A
in
11 12-21-16 RG-GRIT.xlsm, FIG 12/22/2016, 10:12 AM
Design Procedure Form: Rain Garden (RG)
Sheet 2 of 2
Designer: ES
Company: INTERWEST
Date: September 21. 2016
Project: GRIT
Location: RAIN GARDEN (BASIN 8 AND C)
S. Impermeable Geomembrane Liner and Geotextile Separator Fabric
Choose Onn —
Q YES
A) Is an impermeable liner provided due to proximity
NO
of structures or groundwater comamination7
6. Inlet / Outlet Control
Choose One
Sheet Flow No Energy Dissipation Required
[--I
A) Inlet Control®
Concentrated Flo - Energy Dissipation Provided
(' CToosp (LIP
7. Vegetation
I Q Seed (Ran for frequent weed rontrol)
Q Plantings
Q Sand Grown or Other High Infiltration Sod
8. Irrigation
r Choos<One
I Q YES
A) Will the rain garden be irrigated'
I 0 �
Notes:
1 12-21-16 RG-GRIT.xlsm, RG 12/2212016, 10:12 AM
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LID Table
Summary of Areas
Total Area of the Site
51,345
sq. ft.
Total Area of Basin A
11553
sq. ft.
Total Area of Basin B & C
39792 sq. ft.
Basin A
Existing Imperious Area Untreated
7,896
sq. ft.
Proposed Area Impervious Untreated
6,208
sq. ft.
Variance Requested
Basin B & C
Impervious Area Treated
16,737
acre/sq. ft.
Impervious Area Treated by LID
16,737
acre/sq. ft.
% Impervious Area Treated
100
%
% Impervious Area Treated by LID
100
%
I
1
City
Engineer Name Interwest
Street Address 1218 W. Ash
Stormwater
ComplianceNariance Application
f Fort Collins Water Utilities Engineering
Suite A
970-460-8488
City Windsor State CO Zip 80550
Owner Name RSW Holdings ,LLC Phone ryan@sweetwood.com
Street Address 2120 Milestone Drive
City Fort Collins State CO Zip 80525
Project/Application Number from Development Review (i.e. FDP123456) POP1buU24
Legal description and/or address of property Lot 13, the Amended Plat of Lots 13 and 14,
Business Park
Description of ProjecYA single building and modifications to the existing parking and drives.
Existing Use (check one): ❑ residential ❑ non-residential ❑ mixed -use (9 vacant ground
Proposed Use (check one): ❑ 1residential a non-residential ❑ mixed -use ❑ other
If non-residential or mixed use, describe in detail Commercial development -single story gym facility
State the requirement from which alternative compliance/variance is sought. (Please include
applicable Drainage Criteria Manual volume, chapter and section.)
100% of the site to be treated with some form of water quality treatment.
What hardship prevents this site from meeting the requirement?
Today, the north portion of the site has been developed with approximately 8.000 sf of existing pavement draining directly north to the ROW untreated.
With the developmen4 the design leaves approximately 6,000 sf of pavement draining north (Basin A). It Is not feasible to change this drainage pattern.
There is no area to provide water quality. The design reduces the amount of pavement that is untreated from 8,000 sf to 6,000 sf.
Attach separate sheet it necessary
What alternative is proposed for the site?
The amount of impervious area untreated is being reduced. The entire remainder of the site is
treated by LID.
Attach separate sheet if necessary
nacre 2
I
The owner agrees to comply with the provisions of the zoning ordinance, building code and all other
applicable sections of the City Code, Land Use Code, City Plan and all other laws and ordinances
affecting the construction and; occupancy of the proposed building that are not directly approved by
this variance. The owner understands that if this variance is approved, the structure and its occupants
may be more susceptible to flood or runoff damage as well as oth erse drainage issues.
Signature of owner- Date: r 5/ 1b
The engineer hereby certiCs that the above information, along with the reference plans and project
descriptions is correct.
Signature of en ineen i G ' • 11 -
g g Date: f 5 4
5 34M V F
ll•f�rib: F
L
PE STAMP
ete application submitted: II� ?�17
roval/denial: //i//0-O /7 Variance: A approved ❑ denied /
ation/notes/conditions:
s. r
hA riv.n�l/ V/OKS Q/ CQ 1�L6! C4 rye T�V la 6j �/��
. n7i c rn Cif
�
[;Approvedby:
C
:tilityFile Database? ryes ❑ no
I
APPENDIX E
BOX ELDER INFORMATION
(SWMM MODEL)
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7---------------------------- g
LU
LLJ
lJ p Y J a V L
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o
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R +
1'
n $ �
V V
U U Y V U
G
Z
BasinlD
Width
Outlet
Area
Imper
Slope
Overland
Flow Length
(ft)
(Ac)
(%)
(%)
(ft)
2
12700
2
160.3
20
0.8
550
3
33020
3
151.6
41
0.5
200
4
8650
704
29.8
40
1.3
150
5
18380
813
147.7
55
0.7
350
6
1 6120
1 814
63.2
1 6
1.8
450
7
6270
707
136.7
10
0.6
950
8
8040
808
36.9
53
9.1
200
9
1930
809
22.1
23
0.7
500
10
4480
10
87.3
5
1.5
850
11
6420
811
147.3
6
1,1
1000
12
23960
12
27.5
90
0.9
50
13
8590
713
197.1
8
0.8
1000
15.1
610
15.2
12.3
1 30
1 1.3
880
15.2
970
15.2
3.7
14.1
0.8
170
15.3
4060
415
27.9
44.5
2.2
300
15.4
7460
415.4
62.4
35.8
1.1
360
16
500
416
11.5
7
1.6
1000
17
4140
417
52.3
5
3.9
550
18
5460
18
125.3
5
1.0
1000
19
3570
419
82
5
2.5
1000
20
14090
20
1 161.6
20
1 2.0
Soo
21
2190
421
22.6
5
2.9
450
22
1150
822
10.6
5
3.2
400
23
1700
723
31.3
5
2.0
800
24
9790
424
33.7
45
3.3
150
25
5630
725
129.1
5
0.7
1000
26
6756
726
155.1
5
2.0
1000
27
4230
727
72.8
5
2.6
75O
28
5480
28
1 125.9
9
1 3.1
1000
29
21290
729
268.8
29
0.6
550
30
4870
430
33.5
49
1.5
300
31
8040
31
184.5
7
2.1
1000
32
9290
32
213.3
6
1.4
1000
33.1
1480
433
33.9
8
2.1
1000
33.2
5520
433
38
58
2.1
300
33.3
12200
433
84
53
2.1
300
33.4
6050
433
1 41.7
53
2.1
300
34
6220
834
128.5
9
1.0
900
35
13390
735
307.3
6
0.7
1000
36
13840
36
317.8
6
1.0
1000
37
3770
37
34.6
23
1.8
400
38
12660
38
290.7
5
2.9
1000
39
2490
839
17.1
5
30.8
300
40
16070
440
110.7
53
2.7
300
41 1
38510 1
441
132.6
29
1.7
150
42
2350
42
54
5
1.3
1000
43
2060
43
37.8
40
1,9
800
44
3370
744
77.4
7
1.4
1000
45
2370
45
54.3
5
1.0
1000
46
5920
46
135.8
18
3.6
1000
47
13280
747
304.9
9
0.5
3000
48
12690
748
2111
6
0.5
1000
49
9600
49
220.3 1
5 1
3.2
1000
Appendix A - 1: Subbasin Parameters
BasinlD
Width
Outlet
Area
Imper
Slope
Overland
Flow Length
(ft)
(Ac)
(%)
(%)
(ft)
50
7310
50
167.7
5
IS
1000
51
11670
51
267.8
5
4.6
1000
52
10260
752
235.6
13
3.2
1000
53
7290
753
150.7
5
2.0
900
54
12310
54
282.6
6
2.6
1000
55
30000
755
688.6
5
1.8
1000
56
21980
456
403.7
24
2.8
800
57
95030
457
1745
36
4.5
800
58
8760
458
130.7
33
4.3
650
59
10400
459
238.7
5
1.6
1000
60
20400
260
468.4
5
3.3
1000
61
3840
61
22
30
2.0
250
62
2090
62
12
22
2.5
250
63
2400
471
1 14
24
4.5
250
64
1570
64
6.3
37
2.5
170
65
1570
65
5.1
52
2.0
140
66
1350
66
7.7
43
2.0
250
67
2990
67
17
37
2.0
250
68
1760
68
30
31
2.0
250
69
720
633
3.3
1 43
2.0
200
70
6730
70
50
30
2.0
320
71
1600
71
5.5
10
2.2
150
72
2850
861
16
5
0.7
240
75
61940
476
1422
38
6.4
1000
76
94220
477
2163
24
3.0
1000
77
51400
475
1180
25
6.0
1000
78
64030
768
1470
5
1.9
1000
79
61051
79
1401.5
5
1.3
1000
80
4350
80
34.9
5
0.3
350
81
6060
934
139.2
5
0.5
1000
83
2370
83
32.7
5
0.8
1 600
84
1130
563
26
5
0.5
1000
85
4270
785
98
5
0.3
1000
86.1
3930
564
90.3
8
0.6
1000
86.2
10450
486.2
36
80
0.6
150
86.3
17440
486.3
120.2
45
0.6
300
87
6710
617
46.1828
73
0.5
300
88
29000
930
133.3
90
0.6
200
89
38158
933
171.324
46
1.1
200
90
15180
790
174.621
32
0.7
500
91
1900
943
43.5
5
0.1
1000
92
3300
92
68.5
5
4.0
900
93
5100
565
104.901
5
0.9
900
94
6500
539
149.624
5
0.8
1000
95
16220
795
372.4
5
2.5
1000
96
2750
918
63.0725
5
2.1
1000
97
4780
544
109.786
5
1.4
1000
98
1870
98
25.7
5
1.7
600
99
4700
799
108.1
5
1.1
1000
100
498D1
100
57.2
25
1.8
500
101
6870
7301
157.8
5
0.8
1000
102
13420
7102
308
5
0.6
1000
103
30200
103
693.2
16
1.5
1000
BasinlD
Width
Outlet
Area
Imper
Slope
Overland
Flow Length
(ft)
(Ac)
(%)
(%)
(ft)
104
12fi00
104
290.8
14
3.6
1010
105
24130
105
553.9
5
3.1
1000
106
15000
1 560
344.9
5
0.6
1000
107
20210
1 505
463.9
5
0.9
10DO
108
8340
108
191.5
5
3.9
1000
109
8940
109
205.4
11
5.0
1000
110
54100
568
1241
5
0.7
1000
111
21740
7111
499.1
5
2.8
1000
112
11300
572
207.3
5
5.3
800
113
34600
113
476.6
5
4.1
600
114
6550
114
120.1
5
2.5
800
115
17650
561
405.1
5
3.5
1000
116
15650
116
359.1
5
0.7
1000
119
47660
119
1094
5
2.8
1000
120
12200
575
224.7
7
2.1
800
121.1
8760
7121
201.2
5
0.8
1000
121.21
21500
4121.21
147.3
52
0.8
300
121.22
6451
7121
148.1
5
0.8
1000
121.3
10540
7121
121
19
0.8
500
122.1
14160
7122
97.5
85
0.8
300
122.2
5370
4122.2
37
1 55
0.8
300
1.23.1
20160
7123
462.8
6
0.5
1000
123.21
6100
4123.21
42
41
0.5
300
123.22
15300
4123.22
105.4
41
0.5
300
123.23
4290
7123
49.2
41
0.5
500
123.3
9980
7123
114.5
18
0.5
500
123.4
21770
4123.4
149.9
28
0.5
300
123.5
16670
4123.5
114.8
39
0.5
300
124.1
18690
124
429
1 5
1.5
1000
124.2
7584
7317
174.1
5
1.S
1000
124.3
2380
7317
54.6
5
1.5
1000
125
17500
125
241.7
5
5.6
600
126
29600
7126
579.6
5
2.2
1000
127
18620
7127
427.3
8
2.2
1000
128
19650
128
270.7
5
6.7
600
129
46850
7129
860.4
5
4.2
800
130
21450
578
492.4
5
0.9
1000
131.1
1810
7131
41.5
5
1 0.7
1000
131.2
8740
7131
60.2
44
0.7
300
132
375B0
7132
258.8
45
0.7
300
133
8310
7133
144.547
5
2.4
760
134
42760
7134
833.451
5
3.0
850
135
11700
135
268.7
5
1.4
1000
136
18290
7136
419.8
5
1.5
1000
137
13300
7137
305.5
5
0.9
1000
138
7240
138
166.1 1
5 1
1.4
1000
139
6250
7139
143.4
5
0.5
1000
140
9790
7140
67.4
5
5.0
300
]41.1
14240
141
326.8
5
0.7
1000
141.2
19760
4141.2
136.1
52
0.7
300
142
46800
142
752
5
7.1
700
143
37700
582
865.6
5
5.0
1000
144
9040
144
207.5
5
2.5
1000
BasinlD
Width
Outlet
Area
Imper
Slope
Overland
Flow Length
(ft)
(Ac)
(%j
(%)
(ft)
145
9000
145
165.4
13
6.7
800
146
20260
586
465.2
5
0.7
1000
147
8310
147
190.8
5
2.7
1000
148
9460
7148
217.2
5
1.5
1000
149
18230
7149
1 418.5
5
0.9
1000
150
42840
150
688.4
5
8.0
700
151
18790
7151
431.4
5
3.5
1000
152
26050
152
597.9
5
1.3
1000
154
4421
588
101.5
5
0.6
1000
155
3990
155
91.5
5
2.5
1000
156
3750
156
60.3
5
4.0
700
157
33650
7157
681.072
5
3.4
880
158
45450
158
1043
5
0.7
1000
159
28300
7159
649
5
0.8
1000
160
6830
160
156.7
5
1.0
1000
162
58216
162
1336.46
5
4.7
1000
163
29972
7163
688.076
5
3.4
1000
164
2070
164
47.5
5
2.7
1000
165
15163
7165
348.101
5
1.1
1000
166
13050
7166
299.6
5
1.8
1000
167
14720
167
338
5
2.6
1000
168
14509
168
333.081
5
3.2
1000
169
17390
7169
399.3
5
2,0
1000
170
6970
170
159.9
5
5.0
1000
171
19670
171
226.1
5
5.0
500
172
17300
592
397.3
5
2.7
1000
173
12550
595
288
5
1.5
1000
174
16782
174
385.269
5
2.6
1000
175
12210
7175
280.3
5
1.5
1000
176
17500
176
401.8
5
1.0
1000
177
24910
177
571.8
5
2.1
1000
178
25540
178
586.4
5
1.4
1000
179
49790
7179
1143
5
2.3
1000
181
32416
599
744.16
5
2.6
1000
182
25300
7182
580.8
5
2.1
1000
183
42305
183
971.188
5
5.3
1000
184
12134
184
278.566
5
2.5
1000
186
3662.57
186
84.15
5
4.0
1000
188
13173
188
302.4
5
0.6
1000
190
43060
190
989
21
2.4
5000
191
53656
191
1231.77
19
0.9
1000
192
61320
192
1407
19
1.1
1000
193
34630
493
398
30
1.2
500
194
18590
194
299
11
1 2.0
700
195
30240
195
694
11
0.9
1000
196
75077
196
1723.52
5
1.0
5000
200
1460
826
33.6
5
1.6
1000
201
3220
437
14.8
5
2.0
200
202
98097
403
2252
36
6.0
1000
301
33670
301
773.643
5
1.0
1000
302
24071
302
552.596
5
1.5
1000
O
N
O
O
C
O
O
N
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a
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�3
c
ca
E
a
a
LO
M
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O
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to
[TITLE]
INP file created
on 12/26/2013 2:17:35
PM by tmartin with inpPINS version
0.0.2.0
Title/Notes:
[OPTIONS]
FLOW_UNITS
CFS
INFILTRATION
HORTON
FLOW_ROUTING
KINWAVE
START —DATE
O1/28/2013
START_TIME
00:00:00
REPORT —START —DATE
O1/28/2013
REPORT_START_TIME
00:00:00
END —DATE
O1/30/2013
END_TIME
06:00:00
SWEEP —START
O1/01
SWEEP —END
12/31
DRY —DAYS
0
REPORT —STEP
00:01:00
WET —STEP
00:01:00
DRY —STEP
01:00:00
ROUTING_STEP
0:00:30
ALLOW_PONDING
NO
INERTIAL_DAMPING
PARTIAL
VARIABLE_STEP
0.75
LENGTHENING_STEP
0
MIN_SURFAREA
0
NORMAL_FLOW_LIMITED
BOTH
SKIP_STEADY_STATE
NO
FORCE_MAIN_EQUATION
D-W
LINK_OFFSETS
DEPTH
MIN_SLOPE
0
[EVAPORATION]
;;Type
..----------
Parameters
----------
CONSTANT
0
DRY —ONLY NO
[RAINGAGES]
Rain Time
Snow Data
;;Name
Type Intrvl
--------- ------
Catch Source
----------------
--------------
1'
INTENSITY 0:05
1 TIMESERIES 1
2
INTENSITY 0:05
1 TIMESERIES 2
3
INTENSITY 0:05
1 TIMESERIES 3
[SUBCATCHMENTS]
Total Pcnt.
Pcnt. Curb
Snow
;;Name
Raingage Outlet Area Impery
Width
--------------
Slope Length
--------------------------------
Pack
----------------
SB8
1
808
36.9
53
8040
9.1
0
SB80
1
80
34.9
5
4350
0.3
0
SB81
1
934
139.2
5
6060
0.5
0
SB83
1
83
32.7
5
2370
0.8
0
SB84
1
563
26
5
1130
0.5
0
SB85
1
785
98
5
4270
0.3
0
SB86.1
1
564
90.3
8
3930
0.6
0
;Sunflower
Development
SB86.2
1
486.2
36
80
10450
0.6
0
;Clydesdale
Development
SB86.3
1
486.3
120.2
45
17440 0.6 0
SB87 1 617 46.1828 73
6710 0.5 0
29000
0.6
0
SB89
1
933
38158
1.1
0
SB9
1
809
1930
0.7
0
SB90
1
790
15180
0.7
0
SB91
1
943
1900
0.1
0
SB92
1
92
3300
4
0
SB93
1
565
5100
0.9
0
SB94
1
539
6500
0.8
0
SB95
1
795
16220
2.5
0
SB96
1
918
2750
2.1
0
SB97
1
544
4780
1.4
0
SB98
1
98
1870
1.7
0
SB99
1
799
4700
1.1
0
[SUBAREAS]
;;Subcatchment
N-Impery
N-Pery
--------------
RouteTo
PctRouted
----------
-
171.324
46
22.1
23
174.621
32
43.5
5
68.5
5
104.901
5
149.624
5
372.4
5
63.0725
5
109.786
5
25.7
5
108.1
5
S-Impery S-Pery PctZero
------------------------------
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N
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0
0
0
0
0
0
0
0
0
0
0
0
0
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0
0
0
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[TITLE]
;;Project Title/Notes
Box_Elder_100(CE),INP file created on 9/13/2016 by eschneider with ICG
SWMM version 5.1.010
Lot 13 the Amended Plat of Lots 13 and 14, Interchange Business Park
(GRIT)
[OPTIONS]
;;Option
Value
FLOW UNITS
CFS
INFILTRATION
HORTON
FLOW_ROUTING
KINWAVE
LINK_OFFSETS
DEPTH
MIN_SLOPE
0
ALLOW_PONDING
NO
SKIP_STEADY_STATE
NO
START —DATE,
01/28/2013
START_TIME
00:00:00
REPORT —START —DATE
O1/28/2013
REPORT_START_TIME
00:00:00
END DATE
O1/30/2013
END_TIME
06:00:00
SWEEP —START
O1/01
SWEEP —END
12/31
DRY —DAYS
0
REPORT —STEP
00:01:00
WET —STEP
00:01:00
DRY —STEP
01:00:00
ROUTING STEP
0:00:30
INERTIAL_DAMPING
PARTIAL
NORMAL_ FLOW_ LIMITED
BOTH
FORCE_MAIN_EQUATION
D-W
VARIABLE STEP
0.75
LENGTHENING_STEP
0
MIN_SURFAREA
0
MAX_TRIALS
0
HEAD —TOLERANCE
0
SYS_FLOW _TOL
5
LAT_FLOW_TOL
5
MINIMUM STEP
0.5
THREADS
1
[EVAPORATION]
;;Data Source Parameters
..-------------- ----------------
CONSTANT 0
DRY —ONLY NO
[RAINGAGES]
;;Name Format Interval SCF Source
-------------- --------- ------ ----------------
1� INTENSITY 0:05 1 TIMESERIES 1
SB76 2
477
2163
24
94220 3 0
SB77 2
475
1180
25
51400 6 0
S378 2
768
1470
5
64030 1.9 0
SB79 2
79
1401.5
5
61051 1.3 0
;non -tributary area
SB8 1
808
36.9
53
9.1 0
SB80 1
80
34.9
5
0.3 0
SB81 1
934
139.2
5
0.5 0
SB83 1
83
32.7
5
0.8 0
SB84 1
563
26
5
0.5 0
S385 1
785
98
5
0.3 0
SB86.1 1
564
90.3
8
0.6 0
;Sunflower Development
SB86.2 1
486.2
36
80
10450 0.6 0
;Clydesdale Development
SB86.3 1
486.3
120.2
45
17440 06 0
8040
4350
6060
2370
1130
4270
3930
SB87 1 617 45.0028 73 6710
0.5 0
SB88
1
yjU
13J.J
7U
29000
0.6
0
SB89
1
933
171.324
46
38158
1.1
0
SB9
1
809
22.1
23
1930
0.7
0
SB90
1
790
174.621
32
15180
0.7
0
SB91
1
943
43.5
5
1900
0.1
0
SB92
1
92
68.5
5
3300
4
0
SB93
1
565
104.901
5
5100
0.9
0
SB94
1
539
149.624
5
6500
0.8
0
SB95
1
795
372.4
5
16220
2.5
0
SB96
1
918
63.0725
5
2750
2.1
0
SB97
1
544
109.786
5
4780
1.4
0
SB98 1 98 25.7 5 1870
1.7 0
SB99 1 799 108.1 5 4700
1.1 0
B87(GRIT) 1 617 1.18 15
162.15 1.16 0
[SUBAREAS]
;;Subcatchment
N-Impery
N-Pery
S-Impery
S-Pery
PctZero
RouteTo PctRouted
;;------------------------
----------
----------
- --
---------- -
-------------------
SB10
0.016
0.25
0.1
0.3
1
OUTLET
SB100
0.016
0.25
0.1
0.3
1
OUTLET
SB101
0.016
0.25
0.1
0.3
1
OUTLET
SB102
0.016
0.25
0.1
0.3
OUTLET
SB103
0.016
0.25
0.1
0.3
OUTLET
SB104
0.016
0.25
0.1
0.3
1
OUTLET
SB105
0.016
0.25
0.1
0.3
1
OUTLET
SB106
0.016
0.25
0.1
0.3
1
OUTLET
SB107
0.016
0.25
0.1
0.3
1
OUTLET
SB108
0.016
0.25
0.1
0.3
1
OUTLET
SB109
0.016
0.25
0.1
0.3
1
OUTLET
SBll
0.016
0.25
0.1
0.3
1
OUTLET
SB110
0.016
0.25
0.1
0.3
1
OUTLET
SB111
0.016
0.25
0.1
0.3
1
OUTLET
SB112
0.016
0.25
0.1
0.3
1
OUTLET
SB113
0.016
0.25
0.1
0.3
1
OUTLET
SB114
0.016
0.25
0.1
0.3
1
OUTLET
SB115
0.016
0.25
0.1
0.3
1
OUTLET
SB116
0.016
0.25
0.1
0.3
1
OUTLET
SB119
0.016
0.25
0.1
0.3
1
OUTLET
SB12
0.016
0.25
0.1
0.3
1
OUTLET
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[TITLE]
;;Project Title/Notes
Box_Elder_100(PROP),INP file created on 9/13/2016 by eschneider with ICG
SWMM version 5.1.010
Lot 13 the Amended Plat of Lots 13 and 14, Interchange Business Park
(GRIT)
[OPTIONS]
;;Option
Value
FLOW_UNITS
CFS
INFILTRATION
HORTON
FLOW_ROUTING
KINWAVE
LINK_OFFSETS
DEPTH
MIN_SLOPE
0
ALLOW_PONDING
NO
SKIP_STEADY_STATE
NO
START —DATE
O1/28/2013
START_TIME
00:00:00
REPORT —START —DATE
O1/28/2013
REPORT_START_TIME
00:00:00
END —DATE
O1/30/2013
END_TIME
06:00:00
SWEEP —START
O1/01
SWEEP —END
12/31
DRY —DAYS
0
REPORT —STEP
00:01:00
WET —STEP
00:01:00
DRY —STEP
01:00:00
ROUTING STEP
0:00:30
INERTIAL_DAMPING
PARTIAL
NORMAL_ FLOW_ LIMITED
BOTH
FORCE_MAIN_EQUATION
D-W
VARIABLE_STEP
0.75
LENGTHENING_STEP
0
MIN_SURFAREA
0
MAX_TRIALS
0
HEAD —TOLERANCE
0
SYS_FLOW _TOL
5
LAT_FLOW_TOL
5
MINIMUM_STEP
0.5
THREADS
1
[EVAPORATION]
;;Data Source Parameters
..-------------- ----------------
CONSTANT 0
DRY —ONLY NO
[RAINGAGES]
;;Name Format Interval SCF Source
-------------- --------- ------ ----------------
1� INTENSITY 0:05 1 TIMESERIES 1
SB76
2
94220
3
0
SB77
2
51400
6
0
SB78
2
64030
1.9
0
SB79
2
61051
1.3
0
;non -tributary
area
SB8
1
9.1
0
SB80
1
0.3
0
SB81
1
0.5
0
SB83
1
0.8
0
SB84
1
0.5
0
SB85
1
0.3
0
SB86.1
1
0.6
0
;Sunflower Development
SB86.2
1
10450
0.6
0
;Clydesdale Development
SB86.3
1
17440
0.6
0
477
2163
24
475
1180
25
768
1470
5
79
1401.5
5
808
36.9
53
8040
80
34.9
5
4350
934
139.2
5
6060
83
32.7
5
2370
563
26
5
1130
785
98
5
4270
564
90.3
8
3930
486.2
36
80
486.3
120.2
45
SB88
1
930
133.3
90
29000
0.6
0
SB89
1
933
171.324
46
38158
1.1
0
SB9
1
809
22.1
23
1930
0.7
0
SB90
1
790
174.621
32
15180
0.7
0
SB91
1
943
43.5
5
1900
0.1
0
SB92
1
92
68.5
5
3300
4
0
SB93
1
565
104.901
5
5100
0.9
0
SB94
1
539
149.624
5
6500
0.8
0
SB95
1
795
372.4
5
16220
2.5
0
SB96
1
918
63.0725
5
2750
2.1
0
SB97
1
544
109.786
5
4780
1.4
0
SB98 1 98 25.7 5 1870
1.7 0
SB99 1 799 108.1 5 4700
1.1 0
SB87(GRIT) 1 617 1.18 90
162.15 1.16 0
[SUBAREAS]
;;Subcatchment
N-Impery
N-Pery
S-Impery
S-Pery
PctZero
RouteTo PctRouted
..------------------------
-------
----
----------
----------
--------- ----------
SB10
0.016
0.25
0.1
0.3
1
OUTLET
SB100
0.016
0.25
0.1
0.3
1
OUTLET
SB101
0.016
0.25
0.1
0.3
1
OUTLET
SB102
0.016
0.25
0.1
0.3
1
OUTLET
SB103
0.016
0.25
0.1
0.3
1
OUTLET
SB104
0.016
0.25
0.1
0.3
1
OUTLET
SB105
0.016
0.25
0.1
0.3
1
OUTLET
SB106
0.016
0.25
0.1
0.3
1
OUTLET
SB107
0.016
0.25
0.1
0.3
1
OUTLET
SB108
0.016
0.25
0.1
0.3
1
OUTLET
SB109
0.016
0.25
0.1
0.3
1
OUTLET
SBll
0.016
0.25
0.1
0.3
1
OUTLET
SB110
0.016
0.25
0.1
0.3
1
OUTLET
SB111
0.016
0.25
0.1
0.3
1
OUTLET
SB112
0.016
0.25
0.1
0.3
1
OUTLET
SB113
0.016
0.25
0.1
0.3
1
OUTLET
SB114
0.016
0.25
0.1
0.3
1
OUTLET
SB115
0.016
0.25
0.1
0.3
1
OUTLET
SB116
0.016
0.25
0.1
0.3
1
OUTLET
SB119
0.016
0.25
0.1
0.3
1
OUTLET
SB12
0.016
0.25
0.1
0.3
1
OUTLET
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APPENDIX F
FLOODPLAIN INFORMATION
' AND
CITY OF FORT COLLINS FLOODPLAIN REVIEW CHECKLIST FOR 100%
' SUBMITTALS
F
FEMA Flood Risk Man
High Risk
_FEMA Floodway - Area of 100-year floodplain with greatest depths and
fastest velocities.
FEMA Flood Fringe - May Include:
- Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AC, and AH)
- Areas of City 100-year floodplain including ponding areas and sheet
flow areas with average depths of 1-3 feet.
There is a 1% annual chance that these areas will be flooded.
Moderate Risk
May include:
- Areas of FEMA 500-year floodplain (FEMA Zone X-shaded).
- Areas of FEMA or City 100-year floodplain (sheet flow) with
average depths of less than 1 foot. n
-Areas protected by levees from the 100-year flood. JJe��
Low Risk W+E
Areas outside of FEMA and City mapped 100-year and 500-year
F—IFloodplains. Local drainage problems may still exist. S
This information is based on the Federal Emergency Management
Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of
Fort Collins Master Drainageway Plans. This letter does not imply
that the referenced property will or will not be free from flooding or
damage. A property not in the Special Flood Hazard Area or in a
City Designated Floodplain may be damaged by a flood greater
than that predicted on the map or from a local drainage problem
not shown on the map. This map does not create liability on the
part of the City. or any officer or employee thereof, for any damage
that results from reliance on this information.
All floodplain boundaries
are approximate. City of
Fort Collins
GIS
0 so 100 200 300 aoo
Feet
Printed: 07/13/2016
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LOT 13, THE AMENDED PLAT OF LOTS 13 AND 14,
' INTERCHANGE BUSINESS PARK
City of Fort Collins Floodplain Review Checklist
' 100 % Development Review Submittals
Instructions: Complete this checklist by marking all boxes that have been adequately
completed. Put an "NA" next to any items that are not applicable to this particular
submittal. Any boxes that are left blank and do not have an "NA" marked next to them
are considered incomplete.
Date of Review: Reviewer's Name:
' Plat Man
❑ The following required items are on the plat:
❑ 100-year floodplain boundary
❑ City
❑ FEMA
' ❑ Floodway boundary
❑ City
❑ FEMA
❑ The benchmark number and elevation of benchmark
❑ These items match the FIRM. (FEMA Basin)
❑ These items match the Master Plan. (City Basin)
❑ The benchmark number and elevation match with those published in the City of Fort
Collins benchmark system.
Site Plan
The following required items are on the site plan:
' ❑ 100-year floodplain boundary- FEMA and City
❑ 500-year floodplain boundary (if proposed structure is a "critical facility"
and a 500-year floodplain is mapped)
' ❑ Floodway boundary
❑ Erosion buffer zones
❑ Restrictions related to use (ie. critical facility or no residential use of lower
floor if floodproffed mixed use structure)
Drainage and/or Grading Plan (or a separate Floodplain Sheet if it is too cluttered on
' Drainage and Grading Plan)
The following required items are on the drainage and/or grading plan:
' IR 100-year floodplain boundary- FEMA and City
NA 500-year floodplain boundary (if proposed structure is a "critical facility"
and a 500-year floodplain is mapped)
® Floodway boundary
IRA Erosion buffer zones
® Cross-section locations
® BFE lines
NA Lowest floor elevation of structures (bottom of basement or crawl space is
considered the lowest floor)
X The floodplain and floodway boundaries are in the correct location and labeled
properly.
' 5d The cross-section and BFE lines are in the correct location and labeled properly.
® Elevations are referenced to the appropriate datum:
N FEMA basins — list in both NGVD 29 and NAVD 88
RA City basins — list only in NGVD 29
' W Floodway regulations have been met.
X No fill in the floodway unless a hydraulic analysis shows "no -rise".
® No manufactured homes, except in an existing park, can be placed in the
floodway.
R No changing a nonconforming non-residential or mixed use structure to a
residential structure.
' 9 Landscaping meets requirements for no encroachment in the floodway
without a hydraulic analysis to show "no -rise".
N No storage of materials or equipment.
R A note is on the plans about the above floodway restrictions.
N Critical facilities regulations have been met:
9 100 year —no life safety, emergency response or hazardous material
critical facilities
NA 500 year Poudre — no life safety or emergency response critical facilities
NA Any pedestrian bridges in the floodway that are not able to pass the 100-year flow are
' designed to be "break -away".
NA Fences in the floodway will not block conveyance. Example: split -rail fence cabled
together to not float, flap at bottom of privacy fence to allow water through (flap at
BFE or above).
NA Any items in the floodway that can float (Example: picnic tables, bike racks, etc.) are
noted as being anchored.
' NA Erosion Buffer Zone requirements have been met:
❑ Design of any allowed development minimizes disturbance to.channel bed
and banks.
❑
No structures allowed.
❑
No additions to existing structures allowed.
'
❑
Any fencing is split -rail design and break -away, but cabled. Must be
oriented parallel to general flow direction.
❑
No detention or water quality ponds.
❑
No bike or pedestrian paths or trails except as required to cross streams or
waterways.
❑
Road, bicycle and pedestrian bridges must span erosion buffer zone.
'
❑
No fill.
❑
No outdoor storage of non-residential materials or equipment.
❑
No driveways or parking areas.
'
❑
No irrigated vegetation and non-native trees, grasses, or shrubs.
❑
No utilities except as necessary to cross streams or waterways.
❑
No grading or excavation except as required for permitted activities in
'
erosion buffer zone.
❑
No construction traffic except as required for permitted activities in
erosion buffer zone.
'
❑
Any construction in the erosion buffer zone shows that it will not impact
the channel stability.
tNA
A note is on the plans about the above erosion buffer zone restrictions.
WA Any necessary
floodplain modeling has been submitted and approved. All modeling
'
must follow
the City's floodplain modeling guidelines.
'
Special Poudre River Regulations
RA Poudre River Floodway Regulations have been met.
❑
No construction of new residential, non-residential or mixed -use
'
structures.
❑
No redevelopment of residential, non-residential or mixed -use structures.
❑
No additions to residential, non-residential or mixed -use structures.
'
❑
No fill unless hydraulic analysis shows "no -rise".
WA Poudre River floodplain regulations have been met
'
❑
No construction of new residential or mixed -use structures
❑
No additions to residential structures
❑
No additions to mixed -use structures if there is an expansion in the
'
residential -use area of the structure.
❑
No floatable materials on non-residential sites
'
Information Related to Structures in the Floodplain
'
WA For structures in the floodplain, a table is shown that lists the following: Floodplain Use Permit only for
Landscaping and Pavement
❑
City BFE at upstream end of structure
t
❑
FEMA BFE at upstream end of structure (if different than City BFE)
❑ Regulatory flood protection elevation
❑ Lowest floor elevation (bottom of basement or crawl space is considered
lowest floor)
❑ Floodproofing elevation for non-residential structures (if applicable)
❑ Garage slab elevation
❑ HVAC elevation
WA The BFE at upstream end of structures are correct based on interpolation between the
cross -sections.
bd The regulatory flood protection elevation is correct.
W The lowest floor and HVAC are at or above the regulatory flood protection elevation.
® Elevations are referenced to the appropriate datum:
® FEMA basins — list in both NGVD 29 and NAVD 88
WA City basins — list only in NGVD 29
WA A typical drawing detail is included for each foundation type proposed (slab -on -
grade, basement, crawl space) showing the elevation of the HVAC and lowest floor
elevation (which includes bottom of the basement or crawl space) relative to the BFE.
WA If garage is not elevated to the regulatory flood protection elevation, then a drawing
detail is included showing vent placement, size, and number.
❑ There is 1 square inch of venting for every 1 square foot of enclosed area.
' ❑ The bottom of the venting is not higher than 1 foot above grade.
❑ The venting is on at least two sides, preferably on upstream and
downstream sides. (Does not have to be divided equally).
' @A If a non-residential structure is to be floodproofed, one of these conditions is met:
❑ All requirements on separate sheet titled "Floodproofing Guidelines" have
' been met.
❑ If floodproofing information is not submitted as part of the plans, then a
note is on the plans stating that floodproofing information will be
' submitted at the time of the building permit application.
HA For manufactured homes, all submittal requirements on separate sheet titled
' "Installation of a Mobile Home Located in a Floodplain: Submittal Requirements"
have been met.
' pA If the floodplain use permit is not going to be submitted until the building permit is
applied for, then a note is on the plans stating that the floodplain use permit will be
submitted at the time of building permit application.
9A A note is on the plans stating that a FEMA elevation or floodproofing certificate will
be completed and approved before the CO is issued. This is required even if property
' is only in a City floodplain.
Drainage Report
' X The site is described as being in the floodplain. Floodplain name and if the floodplain
is a FEMA or City -designated is described. Any floodway or erosion buffer zones on
' the site are described.
' Jl The FEMA FIRM panel # and date and/or the Master Plan information is cited.
® A copy of the FIRM panel with the site location marked is included in the report.
BA If a floodplain modeling report has been submitted, that report is referenced. The
reason for the floodplain modeling report is described.
NA If a FEMA CLOMR or LOMR has been approved for the site, the case number is
referenced. The reason for the CLOMR or LOMR is described.
NA If a FEMA LOMR is required after construction, this is stated in the report.
N The location of the structures relative to the floodplain is described. If there is both a
FEMA and a City floodplain on the site, the location of the structures relative to both
is described.
' WA The use of the structures is described. This is to determine if the structure is
residential, non-residential, or mixed -use. Also, structures in all 100-year and Poudre
' River 500-year floodplains cannot be used as a critical facility. (See Chapter 10 of
City Code for definitions.)
' N The report describes how the development is in compliance with the applicable
floodplain regulation (Chapter 10 of City Code). (Examples: elevation of lowest floor
above regulatory flood protection elevation, floodproofing, floodway regulation,
' erosion buffer zone regulation, no -rise, etc.)
0A The type of foundation construction for the structures (i.e. slab -on -grade, crawl space,
' basement, etc.) is discussed in the report.
QA The type of foundation matches with the lowest floor elevations and grading plan.
' 0A If any of the garages are not going to be elevated above the regulatory flood
protection elevation, the hydraulic venting requirements are discussed.
0A For structures in the floodplain, a table is included (same table as on the
Drainage/Grading Plan) that lists the following:
❑ City BFE at upstream end of structure
❑ FEMA BFE at upstream end of structure (if different than City BFE)
' ❑ Regulatory flood protection elevation
❑ Lowest floor elevation (bottom of basement or crawl space is considered
lowest floor)
' ❑ Floodproofing elevation for non-residential structures (if applicable)
❑ Garage slab elevation
❑ HVAC elevation
tX Elevations are referenced to the appropriate datum:
❑ FEMA basins — list in both NGVD 29 and NAVD 88
❑ City basins — list only in NGVD 29
0A If the floodplain use permit is not going to be submitted until the building permit is
applied for, then a note must be included in the report that states the permit will be
submitted at the time of building permit application.
BA If floodproofing information is not submitted as part of the plans, then a note must be
in the report stating that floodproofing information will be submitted at the time of
the building permit application.
9A A note is in the report stating that a FEMA elevation or floodproofing certificate will
be completed and approved before the CO is issued.
W In the compliance section, Chapter 10 of City Code is listed.
Floodplain Use Permit
50 Floodplain Use Permit has been submitted for each structure. Floodplain Use Permit only for
Landscaping and Pavement
N Permit fee has been submitted
® All information on permit matches the plans
N All information on permit meets floodplain regulations
FEMA CLOMR Approval
NA FEMA has approved any necessary CLOMRs.
Additional Comments:
Terms to Note
Lowest Floor Elevation — Elevation of the lowest floor of the lowest enclosed area
(including bottom of basement or crawlspace). This is not the same as finished floor. The
lowest floor should be distinguished from finished floor on plans and reports.
Re ug latory Flood Protection Elevation — For all floodplains except the Poudre River, the
' regulatory flood protection elevation is eighteen (18) inches above the base flood
elevation. For the Poudre River floodplain, the regulatory flood protection elevation is
twenty-four (24) inches above the base flood elevation. If there is both a FEMA and a
City BFE, the higher BFE should be used to determine the regulatory flood protection
elevation.
Additional floodplain terminology is defined in Chapter 10 of City Code.
' NOTE: Issues specific to individual sites may arise that result in additional
requirements. These will be discussed during initial meetings with the applicant.
[1
APPENDIX G
SOILS INFORMATION, FIGURES, TABLES
AND
EXCERPTS FROM REPORTS
G
' 10.00
9.00
t
1
8.00
t 7.00
m
L
Lycc 6.00
C
Z 5.00
i
:; 4.00
J
Q
LL
= 3.00
2.00
1.00
0.00 +_
0.00
RAINFALL INTENSITY -DURATION -FREQUENCY CURVE
10.00 20.00 30.00 40.00 50.00
STORM DURATION (minutes)
1-2-year stone - - - 10-Year Storrs 100-Year Storm
Figure RA-16 - City of Fort Collins
Rainfall Intensity -Duration -Frequency Curves
60.00
' (C)
Volume 1, Chapter S — Runoff:
(1)
Section 1.0 is deleted in its entirety.
(2)
A new Section 1.1 is added, to read as follows:
1.1
Runoff Methodolo¢ies
(a) There are two runoff determination methodologies that are approved by the City, the Rational Method and the
Stormwater Management Model (SWMM). The City is the determining authority with respect to the appropriate
'
methodology to use under different circumstances. Early contact with the City is encouraged for the timely determi-
nation of the appropriate runoff methodology to use.
(b) The Rational Method may only be used to determine the runoff from drainage basins that are less than ninety (90)
'
acres in size. The Stormwater Management Model (SWMM) must be used to model drainage basin areas of ninety
(90) acres or more.
(c) All runoff calculations made in the design of both 2-year and 100-year drainage systems must be included with
'
the Storm Drainage Report and all storm drainage facilities designed must be shown on Storm Drainage Plans.
(3)
A new Section 2.8 is added, to read as follows:
2.8
Rational Method Runoff Coefficients
(a) The runoff coefficients to be used in the Rational Method can be determined based on either zoning classifica-
tions or the types of surfaces on the drainage area. Zoning classifications may be used to estimate flow rates and vol-
umes for an Overall Drainage Plan (ODP) submittal, if the types of surfaces are not known. Table RO-10 lists the
runoff coefficients for common types of zoning classifications in the city of Fort Collins.
27
(b) For a Project Plan or Final Plan submittal, runoff coefficients based on the proposed land surface types must be
used. Since the actual runoff coefficients may be different from those specified in Table RO-10, Table RO-11 lists
coefficients for the different types of land surfaces. The runoff coefficient used for design must be based on the actual
conditions of the proposed site.
Table RO-10
Rational Method Minor Storm Runoff Coefficients for Zoning Classifications
Description ojArea or Zoning
Coefficient
R-F
0.3
U-E
0.3
L-M-In
0.55
R-L, N-C-L
0.6
M-M-N, N-C-M
0.65
N-C-B
0.7
Business:
C-C-N, C-C-R, C-N, N-C, C-S
0.95
R-D-R, C-C, C-L
0.95
D, C
0.95
H-C
0.95
C-S
0.95
Industrial:
E
0.85
1
0.95
Undeveloped:
R-C, T
0.2
P-O-L
015
For guidance regarding zoning districts and classifications of such districts please refer to Article Four of the City Land Use Code, as amended.
Table RO-11
Rational Method Runoff Coefficients for Composite Analysis
Character of Surface
Runoff Coefficient
Streets, parking lots, drives:
Asphalt
0.95
Concrete
0.95
Gravel
0.5
Roofs
0.95
Recycled asphalt
0.8
Lawns, sandy soil:
Flat <2%
0.1
Average 2 to 7%
0.15
Steep >7%
0.2
Lawns, heavy soil:
Flat <2%
0.2
Average 2 to 7%
0.25
Steep >7%
0.35
(4) A new Section 2.9 is added, to read as follows:
28
' 2.9 Composite Runoff Coefficient
Drainage sub -basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cas-
es a composite runoff coefficient must be calculated for any given drainage sub -basin.
The composite runoff coefficient is obtained using the following formula:
n
C = i=t (RO-8)
A,
Where:
' C = Composite Runoff Coefficient
Ci = Runoff Coefficient for Specific Area (A)
Ai = Area of Surface with Runoff Coefficient of Ci, acres or feet2
n = Number of different surfaces to be considered
At = Total Area over which C is applicable, acres or feet2
(5) Anew Section 2.10 is added, to read as follows:
2.10 Runoff Coefficient Adjustment for Infreauent Storms
The runoff coefficients provided in tables RO-10 and RO-11 are appropriate for use with the 2-year storm event. For
storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infil-
tration, depression retention, evapo-transpiration and other losses that have a proportionally smaller effect on storm
runoff. This adjustment is applied to the composite runoff coefficient.
These frequency adjustment factors are found in Table RO-12.
Table RO-12
Rational Method Runoff Coefficients for Composite Analysis
Sloan Return Period (years)
Frequency Factor Cf
2 to 10
1.00
11 to 25
1.10
26 to 50
1.20
51 to 100
1.25
Note: The product of C times Cf cannot exceed the value of 1; in the cases where it does, a value of 1 must be used.
(6) Section 3.1 is deleted in its entirety.
(7) Section 3.2 is deleted in its entirety.
(8) Section 3.3 is deleted in its entirety.
(9) A new Section 4.3 is added, to read as follows:
4.3 Computer Modeling Practices
(a) For circumstances requiring computer modeling, the design storm hydrographs must be determined using the
Stormwater Management Model (SWMM). Basin and conveyance element parameters must be computed based on
the physical characteristics of the site.
(b) Refer to the SWMM Users' Manual for appropriate modeling methodology, practices and development. The Us-
ers' Manual can be found on the Environmental Protection Agency (EPA) website
://www.Mmy/ednrmnrl/modelstswmn-/index.W).
' (c) It is the responsibility of the design engineer to verify that all of the models used in the design meet all current
City criteria and regulations.
29
' DRAINAGE CRITERIA MANUAL (V. 1)
Table RO-3—Recommended Percentage Imperviousness Values
Land Use or
Surface Characteristics
Percentage
Imperviousness
Business:
Commercial areas
95
Neighborhood areas
85
Residential:
Single-family
`
Multi -unit (detached)
60
Multi -unit (attached)
75
Half -acre lot or larger
`
Apartments
80
Industrial:
Light areas
80
Heavy areas
90
Parks, cemeteries
5
Playgrounds
10
Schools
50
Railroad yard areas
15
Undeveloped Areas:
Historic flow analysis
2
Greenbelts, agricultural
2
Off -site flow analysis
(when land use not defined)
45
Streets:
Paved
100
Gravel(packed)
40
Drive and walks
90
Roofs
90
Lawns, sandy soil
0
Lawns, clayey soil
0
See Figures RO-3 through RO-5 for percentage imperviousness.
RUNOFF
CA = KA + (1.31i'-1.44i' + 1.135i - 0.12) for CA >: 0, otherwise CA = 0 (RO-6)
CCD = KCD + (0.858i' - 0.786i2 + 0.774i + 0.04) (RO-7)
CB = (CA + CcD )I2
2007-01 RO-9
Urban Drainage and Flood Control District
40° 3443 N
4T 34 37' N
Hydrologic Soil Group—Larimer County Area, Colorado
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Conservation Service National Cooperative Soil Survey
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Hydrologic Soil Group
Hydrologic Soil Group —Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
34
Fort Collins loam, 0 to 1
B
0.0
0.0%
percent slopes
Larimer-Stoneham
36.5%
62
B
0.6
complex, 3 to 10
percent slopes
73
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C
1.0
59.7%
percent slopes
81
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A
0.1
3.8%
to 1 percent slopes
Totals for Area of Interest
1.8
100.0%
i ;OA Natural Resources Web Soil Survey 7/13/2016
i Conservation Service National Cooperative Soil Survey Page 3 of 4
IHydrologic Soil Group—Larimer County Area, Colorado
GRIT
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
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.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie -break Rule: Higher
usDA Natural Resources Web Soil Survey 7/13/2016
i Conservation Service National Cooperative Soil Survey Page 4 of 4