HomeMy WebLinkAboutDrainage Reports - 01/20/2023 (2)Drainage Report
for
Canvas Credit Union
319 South Meldrum Street
Fort Collins, CO 80521
Prepared by: Nicholas Andersen
Reviewed by: Mike Beach, P.E.
Project #:21 011 012
Dated: December 28, 2022
541 East Garden Drive, Unit N, Windsor, CO 80550
(970) 663 4552 EMAIL: mbeach@ridgetopeng.com
City of Fort Collins Approved Plans
Approved by:
Date:
2 |P a g e
Section Page
1. Project Engineers Certification .......................................................................................3
2. Project Location & Overview ...........................................................................................4
3. Drainage Design Criteria ..................................................................................................5
4. Hydraulic Calculations......................................................................................................6
5. Facility Design..................................................................................................................7
6. Conclusion.......................................................................................................................8
7. References.......................................................................................................................8
Appendix A Site Vicinity Map
Appendix B Flood Insurance Rate Map
Appendix C NRCS Soils Map
Appendix D Hydrologic Criteria
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO 3 Recommended Percentage Imperviousness Values
Appendix E Hydraulic Calculations
Runoff Coefficients & Imperviousness
Time of Concentration SF 2
Rational Method Runoff Flows SF 3 (2 Year Event)
Rational Method Runoff Flows SF 3 (10 Year Event)
Rational Method Runoff Flows SF 3 (100 Year Event)
Rain Garden Calculations
LID Summary
Drain Times
Appendix F Maps
Drainage Plan/Subbasin Map
Appendix G References
Table of Contents
3 |P a g e
Section 1: PROJECT ENGINEERS CERTIFICATION
I hereby attest that this Final Drainage Report for the design of stormwater management
facilities for Canvas Credit Union on 319 S Meldrum St. was prepared by me, or under my direct
supervision, in accordance with the provisions of the City of Fort Collins Storm Drainage Design
Criteria and Construction Standards for the responsible parties thereof.
__________________________
Mike Beach, P.E.
Registered Professional Engineer
State of Colorado No. 45088
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Section 2: Project Location & Overview
Location
The sites address is 319 Meldrum St, Fort Collins, CO; which is described as Lot 2, Canyon Place,
City of Fort Collins, County of Larimer, State of Colorado. For Recording purposes: Part of the
Southeast Quarter of Section 11, Township 7 N, R 69 W of the 6
th PM.
Located along the west side of Meldrum St. and southeast of Canyon Ave, the site is described
as above and contains 0.65 acres of developed land. (See Appendix A Site Vicinity Map)
This site is located in the Old Town Basin, which generally flows west to east and is completely
urbanized. A master plan update is currently underway to improve drainage in the area and
prevent flooding.
Existing Condition
The existing site is covered by an existing building (~5,340 SF) and parking that mainly flows
runoff to the southeast. Stormwater runoff collects into existing stormwater infrastructure
around the site. The water then flows to the east <1 mile into the Udall Water Quality Facility.
This facility qualifies for standard water quality treatment of the site.
Proposed Condition
The intent of the development is to construct a new building of approximately 3,858 SF,
concrete parking, curb and gutter, drive thru, and landscaping. The city requires that all new or
modified impervious areas have standard water quality treatment and Low impact
development (LID) to treat runoff. As the site already releases to a facility with water quality
treatment, only LID is proposed. A rain garden is proposed to treat 75% of the new/modified
impervious areas.
Floodplain
FEMA Floodplain mapping in this neighborhood is located on map panel 08069C0979H,
Effective May 2, 2012, however it appears the subject property is located in Zone X, which is
outside the 100 year floodplain. Portions of the property are in the City designated Old Town
100 year and Moderate Risk Floodplain, per The Old Town Master Drainage Plan, dated July 11,
2003. Project shall comply with Chapter 10 of City Municipal Code.
Existing Soils
The Natural Resource Conservation Service mapped the historic soils on the site as Fort Collins
loam. The Hydrologic Class is Type CSoils. (Appendix C NRCS Soils Map)
5 |P a g e
Section 3: Drainage Design Criteria
Reference Manuals
Storm drainage design criteria is defined in the City of Fort Collins Storm Water Criteria
Manual (FCSWCM) and Amendments, which references to the Urban Drainage and Flood
Control District(UDFCD) and the Urban Storm Drainage Criteria Manual(USDCM), Volumes
1, 2, and 3, dated 2008 with revisions (the Manual), are used and referenced in this report.
Low Impact Development (LID) Requirements
The proposed development is required to meet the Citys current Land Use Code, which
includes:
50% of the newly added or modified impervious area must be treated by LID
techniques and 25% of new paved areas must be pervious.
75% of all newly added or modified impervious area must be treated by LID
techniques.
Four Step Process
The City of Fort Collins has adopted the Four Step Processthat is recommended in Volume 3
of the USDCM for selecting BMPs in urban redevelopment areas. The goal of this process is to
minimize adverse impacts on receiving waters. The following describe how each step of the
process are incorporated in the proposed development:
Step 1 Employ Runoff Reduction Practices
By selecting a site that was developed and that currently does not have water quality
treatment, the impacts of the proposed development will be less due to the addition of LID
practices. The project proposes to install a rain garden with underdrains to aid in conveyance
and infiltration opportunities which will reduce the effects of the added impervious area from
the development of the site.
Step 2 Water Quality Capture Volume (WQCV)
In order to reduce the sediment load and other pollutants leaving the site, it is important to
provide WQCV to minimize the downstream impacts. This project proposes to provide rain
garden prior to the stormwater entering the stormwater system and detention pond. These
facilities are sized to release at or below the historic runoff rates.
Step 3 Stabilize Drainageways
Since this site is in close proximity to Poudre River it is important to take this step into
consideration. By providing stormwater detention and water quality and lowering the historic
runoff and providing a metered outflow the project impacts to the drainageway are essentially
reduced. The majority of the drainageway leaving the site is already stabilized.
6 |P a g e
Step 4 Implement Site Specific and Other Source Control BMPs
The proposed project will contain the following BMPs:
Rain Garden: All runoff from the project site will be directed into and through the
proposed BMP facilities prior to leaving the site. Rain gardens utilize native plants that
act as sponges to reduce the amount of stormwater runoff and absorb contaminants.
Maintenance: In order for BMPs to remain effective proper maintenance needs are
required. Scheduled visual inspections and routine repair after larger storm events are
critical in the maintenance and effectiveness of the installed BMPs.The sites owner will
be advised of these practices during installation in order to maximize the efficiency of
the installed BMPs.
Section 4: Hydraulic Calculations
Criteria
Runoff criteria for the proposed sites was analyzed for the 2 YR, 10 YR, and 100 YR storm
events. The Rational Method is being used for the design of the proposed improvements.
Rainfall Intensities used in the proposed design were determined as a function of the Time of
Concertation for each subbasin. The values used were determined by the City of Fort Collins
Rainfall Intensity/Duration/Frequency curve (Figure 3.4 1 and Table 3.4 1 (see Appendix D).
Imperviousness
Values from Table 4.1 3 (Fort Collins Amendment to the USDCM) were used in determining the
sites imperviousness. The overall proposed site improvements and landscaping equate to a
total disturbed Imperviousness of 75.8%.
Time of Concentration & Runoff Coefficient
The onsite area was separated into three (3) subbasins with slopes varying between 0.5% to
3.0%. The calculated Time of Concentration (TC) for each subbasin are listed in Appendix E. See
Basin Map in Appendix F for more information.
WQCV
The UD BMP_v3.07 (UDFCD) spreadsheet was used to calculate the required Rain Garden water
quality capture volume. See Appendix E for design information. Open Grated Nyloplast
structures (or equivalent) tied to the detention pond will be installed one foot above the
bottom of the Rain Gardens that will accept flows above the required WQCV.
7 |P a g e
Section 5: Facility Design
The proposed improvements will reduce the amount of impervious area; however, measures
have been included in the design to minimize the amount of stormwater released from the site.
The site was broken into three developed subbasins for water quality purposes; Subbasin 1
(0.228 acres), Subbasin 2 (0.306 acres), and Subbasin Pond (0.112 acres). See Appendix E for
breakdown of the different area types for each subbasin and Appendix F for the Subbasin Map.
Subbasin 1 contains half of the proposed building and the north half of the existing parking
lot. This basin will continue to flow to the right of way as it has in the existing condition.
Subbasin 2 contains half of the building and the majority of the modified impervious areas. All
areas drain to the east. LID practices for this subbasin will be provided via a rain garden. The
rain garden will outlet to the existing stormwater system in the right of way.
Subbasin 3 contains the south half of the existing parking lot. This basin will continue to flow
into a storm inlet in the parking lot as it has in the existing condition.
See table 1 below for basin breakdown.
Basin Area
(ac)
Imperviousness
(%)
2 yr Runoff
(cfs)
10 yr Runoff
(cfs)
100 yr Runoff
(cfs)
1 0.228 78.3 0.4 0.8 1.8
2 0.306 72.5 0.5 0.9 2.4
3 0.112 79.5 0.2 0.4 0.9
8 |P a g e
Section 6: Conclusions
All computations that have been reviewed or completed within this report are in compliance
with the City of Fort Collins Storm Drainage Design Criteria and Construction Standards manual
and the Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual
Volumes 1, 2, & 3.
The proposed drainage concepts presented in this report and on the construction plans
adequately provides for water quality treatment of impervious areas by collecting storm events
within the proposed rain garden.
Section 7: References
The Natural Resource Conservation Service Soil Survey for Larimer County and the WSS
website.
FEMA FIRM map panel 08069C0979H Effective 5/12/2012.
City of Fort Collins Stormwater Criteria Manualdated December 2018
Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual
(UDFCD), Volumes 1, 2, and 3, dated 2008 with revisions (the Manual).
w Appendix A
Site Vicinity Map
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VICINITY MAP �
1" = 1000'
Appendix B
Flood Insurance Rate Map
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Hydrologic Soil Group—Larimer County Area,Colorado
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
35 Fort Collins loam, 0 to 3 C 0.8 100.0%
percent slopes
Totals for Area of Interest 0.8 100.0%
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
u� Natural Resources Web Soil Survey 4/13/2022
� Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group—Larimer County Area,Colorado
Tie-break Rule: Higher
u� Natural Resources Web Soil Survey 4/13/2022
� Conservation Service National Cooperative Soil Survey Page 4 of 4
Appendix D
Hydrologic Criteria
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 8
Table 3.4-1. IDF Table for Rational Method
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
5 2.85 4.87 9.95 39 1.09 1.86 3.8
6 2.67 4.56 9.31 40 1.07 1.83 3.74
7 2.52 4.31 8.80 41 1.05 1.80 3.68
8 2.40 4.10 8.38 42 1.04 1.77 3.62
9 2.30 3.93 8.03 43 1.02 1.74 3.56
10 2.21 3.78 7.72 44 1.01 1.72 3.51
11 2.13 3.63 7.42 45 0.99 1.69 3.46
12 2.05 3.50 7.16 46 0.98 1.67 3.41
13 1.98 3.39 6.92 47 0.96 1.64 3.36
14 1.92 3.29 6.71 48 0.95 1.62 3.31
15 1.87 3.19 6.52 49 0.94 1.6 3.27
16 1.81 3.08 6.30 50 0.92 1.58 3.23
17 1.75 2.99 6.10 51 0.91 1.56 3.18
18 1.70 2.90 5.92 52 0.9 1.54 3.14
19 1.65 2.82 5.75 53 0.89 1.52 3.10
20 1.61 2.74 5.60 54 0.88 1.50 3.07
21 1.56 2.67 5.46 55 0.87 1.48 3.03
22 1.53 2.61 5.32 56 0.86 1.47 2.99
23 1.49 2.55 5.20 57 0.85 1.45 2.96
24 1.46 2.49 5.09 58 0.84 1.43 2.92
25 1.43 2.44 4.98 59 0.83 1.42 2.89
26 1.4 2.39 4.87 60 0.82 1.4 2.86
27 1.37 2.34 4.78 65 0.78 1.32 2.71
28 1.34 2.29 4.69 70 0.73 1.25 2.59
29 1.32 2.25 4.60 75 0.70 1.19 2.48
30 1.30 2.21 4.52 80 0.66 1.14 2.38
31 1.27 2.16 4.42 85 0.64 1.09 2.29
32 1.24 2.12 4.33 90 0.61 1.05 2.21
33 1.22 2.08 4.24 95 0.58 1.01 2.13
34 1.19 2.04 4.16 100 0.56 0.97 2.06
35 1.17 2.00 4.08 105 0.54 0.94 2.00
36 1.15 1.96 4.01 110 0.52 0.91 1.94
37 1.16 1.93 3.93 115 0.51 0.88 1.88
38 1.11 1.89 3.87 120 0.49 0.86 1.84
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 9
Figure 3.4-1. Rainfall IDF Curve – Fort Collins
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
4.0 SWMM
4.1 Input Parameters
Page 10
4.0 SWMM
This section is for project sites that require the use of the Stormwater Management Model (SWMM) to
determine storm hydrograph routing and is the only method that is able to assess the overall
performance of multiple detention basins in parallel or in series in a particular project site or watershed.
Reference: The theory and methodology for reservoir routing is not covered in this Manual
as this subject is well described in many hydrology reference books. The EPA SWMM
Reference Manuals, dated January 2016, have been utilized in preparing the information in
this section of the Manual.
4.1 Input Parameters
Table 4.1-1 provides required input values to be used for SWMM modeling.
Basin and conveyance element parameters must be computed based on the physical characteristics of
the site.
Table 4.1-1. SWMM Input Parameters
Depth of Storage
Impervious Areas 0.1 inches
Pervious Areas 0.3 inches
Infiltration Parameters
Maximum 0.51 in/hr
Minimum 0.50 in/hr
Decay Rate
0.0018 in/sec or
6.48 in/hr
Zero Detention Depth 1%
Manning's "n"
Pervious Surfaces 0.250
Impervious Surfaces 0.016
For Overall Drainage Plan (ODP) and Project Development Plan (PDP) submittals, when surface types
may not yet be known, land uses may be used to estimate impervious percentages. Table 4.1-2 lists the
percent imperviousness for common types of land uses in the City.
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
4.0 SWMM
4.1 Input Parameters
Page 11
Table 4.1-2. Land Use - Percent Impervious
Land Use
Percent Impervious
(%)
Residential
Urban Estate 30
Low Density 50
Medium Density 70
High Density 90
Commercial
Commercial 80
Industrial 90
Undeveloped
Open Lands, Transition 20
Greenbelts, Agriculture 2
Offsite Flow Analysis (when
Land Use not defined) 45
Reference: For further guidance regarding zoning classifications, refer to the Land Use
Code, Article 4.
For Final Plan (FP) submittals, impervious values must be based on the proposed land surface types.
Refer to Table 4.1-3 for recommended percent impervious values.
Table 4.1-3. Surface Type – Percent Impervious
Surface Type
Percent Impervious
(%)
Hardscape or Hard Surface
Asphalt, Concrete 100
Rooftop 90
Recycled Asphalt 80
Gravel 40
Pavers 40
Landscape or Pervious Surface
Playgrounds 25
Lawns, Sandy soil 2
Lawns, Clayey soil 2
Appendix E
Hydraulic Calculations
Weighted Runoff CoefficientsCalculated By: JKSProject : Canvas Credit UnionChecked By: MRBJob Number: -Date: 7/7/2022Proposed/IMP% Soil Types: Fort Collins Loam, 0-3 %Existing Roof90Concrete Drive/Walk90Landscaping2Hydrologic Grouping:Type C/DGravel40Multi-family (attached)75Runoff Coefficients:C = KcCommercial50 Kc(2year) = 0.83i^1.122Undeveloped Historical2 Kc(5year) = 0.82i+0.035Kc(10year) = 0.74i+0.132Kc(100year) = 0.41i+0.484Proposed Basins (proposed conditions)Land Use (Acres) Weighted Runoff CoefficientTotal ConcreteBasin Area RoofDrive/WalkLandscape Gravel Residential Pavers C2 C5 C10 C100 %Imp10.23 0.05 0.15 0.03 0.00 0.00 0.00 0.63 0.67 0.68 0.80 78.320.31 0.04 0.20 0.06 0.00 0.00 0.00 0.58 0.62 0.63 0.78 72.530.11 0.00 0.10 0.01 0.00 0.00 0.00 0.64 0.68 0.69 0.81 79.5
STANDARD FORM SF-2TIME OF CONCENTRATIONSUBDIVISION: Canvas Credit UnionCALCULATED BY: JKS DATE: 7/7/2022SUB-BASIN INITIAL/OVERLAND TRAVEL TIME tc CHECKFINAL REMARKSDATATIME (ti) (tt) (URBANIZED BASINS)tcDESIG:C5AREA LENGTH SLOPEtiLENGTH SLOPE VEL.ttCOMP.TOT. LENGTH tc=(L/180)+10Ac Ft % Min Ft % FPS MintcFt Min Min(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)1.000.67 0.23 35 1.5 0.9 110 1.5 2.0 0.9 1.8 145 10.8 5.02.000.62 0.31 20 1.0 0.8 90 0.5 2.0 0.8 1.6 110 10.6 5.03.000.68 0.11 10 2.0 0.4 50 2 2.0 0.4 0.8 60 10.3 5.0
CALCULATED BY : JKSSTANDARD FORM SF-3 JOB NO:-DATE:REV:STORM DRAINAGE SYSTEM DESIGN PROJECT:Canvas Credit UnionCHECKED BY: MRB(RATIONAL METHOD PROCEDURE) DESIGN STORM:2-YEAR DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIMEBASINDESIGNPOINTAREADESIGNAREA(AC)RUNOFFCOEFF tc(MIN)C * A(AC)IIN/HRQ(CFS)tc(MIN)(C * A)(AC)I(IN/HR)Q(CFS)SLOPE(%)STREETFLOW (CFS)DESIGNFLOW (CFS)SLOPE(%)PIPESIZELENGTH(FT)VELOCITY(FPS)tt(MIN)REMARKS (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1237/7/20220.23 0.63 5.0 0.14 2.85 0.40.31 0.58 5.0 0.18 2.85 0.50.11 0.64 5.0 0.07 2.85 0.2Page 1 2-YEAR
CALCULATED BY : RSBSTANDARD FORM SF-3 JOB NO:-DATE:REV:STORM DRAINAGE SYSTEM DESIGN PROJECT:Canvas Credit UnionCHECKED BY: MRB(RATIONAL METHOD PROCEDURE) DESIGN STORM:10-YEAR DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIMEBASINDESIGNPOINTAREADESIGNAREA(AC)RUNOFFCOEFF tc(MIN)C * A(AC)IIN/HRQ(CFS)tc(MIN)(C * A)(AC)I(IN/HR)Q(CFS)SLOPE(%)STREETFLOW (CFS)DESIGNFLOW (CFS)SLOPE(%)PIPESIZELENGTH(FT)VELOCITY(FPS)tt(MIN)REMARKS (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1230.31 0.63 5.0 0.19 4.87 0.90.23 0.68 5.0 0.15 4.87 0.80.08 4.87 0.40.11 0.69 5.07/7/2022Page 1 10-YEAR
CALCULATED BY : JKSSTANDARD FORM SF-3 JOB NO: -DATE:REV:STORM DRAINAGE SYSTEM DESIGN PROJECT:Canvas Credit UnionCHECKED BY: MRB(RATIONAL METHOD PROCEDURE) DESIGN STORM:100-YEAR DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIMEBASINDESIGNPOINTAREADESIGNAREA(AC)RUNOFFCOEFF tc(MIN)C * A(AC)IIN/HRQ(CFS)tc(MIN)(C * A)(AC)I(IN/HR)Q(CFS)SLOPE(%)STREETFLOW (CFS)DESIGNFLOW (CFS)SLOPE(%)PIPESIZELENGTH(FT)VELOCITY(FPS)tt(MIN)REMARKS (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1230.11 0.81 5.0 0.09 9.95 0.99.95 2.40.31 0.78 5.0 0.247/7/20220.23 0.80 5.0 0.18 9.95 1.8Page 1 100-YEAR
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =72.5 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.725
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 = 13,345 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =255 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 = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =194 sq ft
D) Actual Flat Surface Area AActual =207 sq ft
E) Area at Design Depth (Top Surface Area)ATop =517 sq ft
F) Rain Garden Total Volume VT=362 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =1.5 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =255 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =3/8 in
Design Procedure Form: Rain Garden (RG)
JKS
Ridgetop Engineering
July 7, 2022
Canvas Credit Union Meldrum
Fort Collins, CO
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
Pond.xlsm, RG 7/7/2022, 2:06 PM
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)
JKS
Ridgetop Engineering
July 7, 2022
Canvas Credit Union Meldrum
Fort Collins, CO
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
Pond.xlsm, RG 7/7/2022, 2:06 PM
14 |P a g e
Appendix F
Maps
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