HomeMy WebLinkAboutPARKING AT 620 S. LEMAY AVE. - MJA/FDP - FDP150009 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTDRAINAGE REPORT
FOR
Parking at 620 S. Lemay Avenue
620 S. Lemay
Fort Collins, CO 80524
Prepared for:
CS Design, Inc.
2519 S. Shields St. #129
Fort Collins, CO 80526
Prepared by:
www.quality-engineering.com
1501 Academy Court, #201
Fort Collins, Colorado 80524
(970) 416-7891
QE Project No: 1060-003
Date: April 29, 2015
Parking at 620 S. Lemay Avenue
FINAL DRAINAGE REPORT
ENGINEER’S CERTIFICATION
I hereby certify that this Final Drainage Report for the design of stormwater management
facilities for the Parking at 620 S. Lemay Avenue Project 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 owners thereof.
Cody Geisendorfer, P.E.
Registered Professional Engineer
State of Colorado No. 41326
I. Table of Contents
I. GENERAL LOCATION AND DESCRIPTION ......................................... 1
A. Location .................................................................................................................... 1
B. Description of Property ........................................................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS .................................................. 2
A. Major Basin Description ......................................................................................... 2
B. Sub-Basin Description ............................................................................................. 2
III. DRAINAGE CRITERIA ............................................................................... 3
A. Regulations ............................................................................................................... 3
B. Implementation of the “Four Step Process” .......................................................... 3
C. Development Criteria Reference and Constraints ................................................ 4
D. Hydrological Criteria............................................................................................... 4
E. Hydraulic Criteria ................................................................................................... 5
F. Modifications of Criteria ......................................................................................... 5
IV. DRAINAGE FACILITY DESIGN ............................................................... 5
A. General Concept....................................................................................................... 5
B. Specific Details ......................................................................................................... 6
C. Rain Garden/Detention Pond.................................................................................. 6
V. CONCLUSIONS ............................................................................................. 7
A. Compliance with Standards .................................................................................... 7
B. Drainage Concept..................................................................................................... 7
VI. REFERENCES ............................................................................................... 7
VII. APPENDICES
A. Hydrologic Computations
Vicinity Map
FEMA FIRM Exhibit
USGS Soil Map
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO-3 Recommended Percentage Imperviousness Values
Rational Method Calculated Composite C Tables
Rational Method Calculated Imperviousness
Rational Method Calculated Flows
B. Hydraulic Computations
Rain Garden Outlet Area Inlet Calculations
Rain Garden Outlet Pipe Calculations
C. Water Quality Design Calculations
UD BMP Rain Garden Calculations
D. Standard Operating Procedures
Standard Operating Procedures
I. GENERAL LOCATION AND DESCRIPTION
A. Location
The proposed site is located in the northwest quarter (NW ¼) of the northwest quarter
(NW ¼) of Section 18, Township 7 North, Range 68 West of the 6th P.M. in Larimer
County, Colorado. Specifically, the property is located at the southeast corner of Poudre
River Drive and Hoffman Mill Road. More generally, the property is located at the
northeast corner of Lemay Avenue and Riverside Avenue. The property address is 620 S.
Lemay Avenue, Fort Collins, Colorado, 80524. (Please see the vicinity map located in
the Appendix A).
B. Description of Property
The property is parcel number 8718200035 of the Poudre River Business Park and is
currently 0.99 acres of undeveloped land surrounded by undeveloped property to the
north and east, medical offices to the northwest, Concentra Urgent Care to the west, and
East Laurel St. to the south. Hoffman Mill Road is located directly west of the property
and acts as its only access. Both existing Hoffman Mill Road and Poudre River Drive are
paved with curb, gutter, sidewalk, and utilities installed. Hoffman Mill Road to the
southwest and E. Laurel Street to the south of the property are unpaved, gravel roads. E.
Laurel Street is a private street.
The existing property is mainly natural vegetation that has no general drainage patterns.
It appears that onsite flows pond and infiltrate, without leaving the site. Existing
Hoffman Mill Road drains north to the existing inlet, where it is conveyed to the Poudre
River. Existing Poudre River Drive drains east towards the existing storm inlet, where it
joins flows from Hoffman Mill Road. There are generally no offsite flows that drain
toward the property. The entire site is located entirely outside of any 100-year flood
plain (see FIRMETTE in Appendix A).
According to the NRCS soils map survey, the native soils consist of the Type “B” soils.
These soils consist of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils produce
moderate infiltration rates when thoroughly wet.
There are no irrigation facilities located within the proposed site area.
The proposed development will consist of the construction of a 37 space parking lot that
will act as overflow parking for the Concentra Urgent Care directly across Hoffman Mill
Road. The parking lot will be paved asphalt with curb and gutter. Parking stalls will
consist of pervious pavers. A rain garden will be installed on the northwest corner of the
proposed site.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
The proposed site is located within the Cache la Poudre River Basin. The basin is a major
tributary to the South Platte River and the major confluence of many of Fort Collins’ sub-
basins. As determined in the Final Drainage Report for Poudre River Business Park, First
Filing, onsite detention is not required due to the close proximity to the Cache la Poudre
River.
The Poudre River Business Park, First Filing development installed the storm drain system
along Poudre River Drive, including the curb inlets and storm pipe that conveys flow north
to the Poudre River. This 24” ADS pipe (downstream of the 620 S. Lemay system) has a
capacity of 23 cfs. Once the pipe reaches capacity, onsite detention will be required for
future developments within the Poudre River Business Park. The Poudre River Business
Park, First Filing uses 7.98 cfs of the 23 cfs. The Poudre River Business Park, Second
Filing produces an additional 5.92 cfs of flow into this system. The Poudre River Business
Park, Third Filing produces an additional 1.0 cfs into this system. The total receiving flow
of the storm system from the first three filings is 14.9 cfs; allowing for an additional 8.1 cfs
of flow into the existing storm system before the system is at capacity and onsite detention
is required.
B. Sub-Basin Description
Historically, most of the site ponds and infiltrates within the property. The surrounding
roads are at a high elevation than the proposed site, so no historic flows drain to these roads.
The developed site is delineated into one sub-basin, with a rain garden designed to provide
the required water quality capture volume.
Sub-basin B1, (0.99 acres), consists of asphalt/concrete, landscaped area, and natural
vegetation. Rainfall travels via overland flow from the center of the parking area to the
exterior of the lot, where it will concentrate in valley pans and will be conveyed to the rain
garden where the WQCV is treated. Overland flow will also infiltrate the permeable pavers
in the parking stalls, where it will be treated.
Sub-basin OS1 accounts for the south half of the Poudre River Drive extension. Rainfall in
this basin will travel via overland flow where it will concentrate in gutter flow and travel
west to the existing curb inlet on the southeast side of Poudre River Drive and Hoffman Mill
Road.
Sub-basin OS2 accounts for the Hoffman Mill Road extension. Rainfall in this basin will
travel via overland flow where it will concentrate in gutter flow and travel south where it
will meet the existing Hoffman Mill Road and will be conveyed as it has historically.
The total additional flow to the existing storm sewer system is 5.55 cfs; less than the
maximum allowable increase of 8.1 cfs. Therefore, the downstream existing storm system
will still be under capacity even with the inclusion of the entire 100-year flow.
Currently, offsite flows do not enter the site property. This will not change after the site has
been developed.
III. DRAINAGE CRITERIA
A. Regulations
Drainage design criteria specified in the City of Fort Collins Storm Drainage Design Criteria
and Construction Standards manual (FCSDCM) and the Urban Storm Drainage Criteria
Manual, Volume 3 by the Urban Drainage and Flood Control District (UDFCD) have been
referenced in the preparation of this study.
B. Implementation of the “Four Step Process”
The overall stormwater management strategy employed with this parking lot expansion
project utilizes the “Four Step Process” to minimize adverse impacts of urbanization on
receiving waters. The following is a description of how the proposed development has
incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to
reduce the stormwater impacts of this development is the site selection itself. By selecting a
site with historically undetained runoff, the burden of development will be significantly less
with a WQCV pond. Also, for Basin B1, permeable pavers and rain gardens are used to
convey the runoff from impervious surfaces, reducing the effects of imperviousness.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV)
with Slow Release. Urban development will cause stormwater runoff to increase from the
site. The primary water quality will occur in the rain garden on the northwest side of the lot.
Refer to the map pocket for rain garden and permeable paver details and cross-sections. The
rain garden and permeable pavers will increase water quality and promote infiltration.
Step 3 – Stabilize Drainageways. The Poudre River is the governing drainageway for the
proposed site. The proposed project indirectly helps achieve a better stabilized drainageway
nonetheless. By improving the water quality and increasing infiltration, the likelihood of
bed and bank erosion from this site is greatly reduced.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The Parking at 620 S. Lemay Avenue site contains a plethora of source control BMPs.
Permeable Pavement Systems: Flow from the parking lot will directly flow into the void
area of the pavers avoiding any extra pollutant-flow contact time. Additional flow from the
sidewalks will be captured by the pavers and be treated before an underdrain system
transfers flow to the Rain Garden.
Rain Garden: All Unconnected Impervious Areas (UIA) are drained through the on-site
rain garden, reducing the impact of the impervious areas on water quality. The rain garden
will increase the water quality of released flows, and will aid in the infiltration of these
capture flows.
C. Development Criteria Reference and Constraints
The criteria used as the basis for analysis and design of stormwater management
improvements for this site are those found in the references cited.
To the knowledge of the author, there are no other capital drainage improvements planned
for this portion of the Poudre River Business Park; aside from those referred to above, that
would constrain or otherwise influence the design of the stormwater improvements for this
site.
D. Hydrological Criteria
Stormwater runoff from the respective sub-basins of the site is analyzed for storms with 2-
year and 100-year return frequencies.
Due to the relatively small aggregate area of the tributary drainage sub-basins, the Rational
Method was chosen for use in the design of the stormwater management improvements.
The Rational Method provides that:
Q = CIA, where:
Q = Design flow in cubic feet per second (cfs)
C = Coefficient of runoff for the area under consideration
I = Rainfall intensity for the design storm duration (in/hr)
A = Area of the drainage sub-basin under consideration (ac)
Peak flows were calculated using the Rational Method for the 2-year and 100-year storm
events. This software uses the local 1-hour rainfall depth and Fort Collins rainfall
intensities developed calculate rainfall intensities as a function of the time of concentration.
These values were obtained by the City of Fort Collins Rainfall Intensity-Duration-
Frequency (IDF) curve/table; Figure 3-1 and Table 3-1a, and can be found in the Appendix.
Additionally, per City of Fort Collins, the coefficients have been multiplied by the
appropriate storm factors.
Percent imperviousness values were taken from Table RO-3, Recommended Percentage
Imperviousness Values, UDCM (See Appendix). Soils of hydrologic soil type “B”
dominate the site. Onsite runoff was calculated to determine the runoff differential between
existing and developed conditions for use in sizing the rain garden as required by the
FCSDM. The hydrologic basin parameters and runoff rates are included in the Appendices
and include quantification of the allowable volume reduction.
The USDFCD software UD-BMP v3.03 was used to calculate the required WQCV and the
size for the proposed rain garden.
The design worksheets included in the Appendices to this Final Drainage Report present
documentation of the hydrologic calculations for the on-site storm drainage systems.
E. Hydraulic Criteria
Within this development, all runoff will be conveyed on the surface, initially as sheet flow
and subsequently as concentrated flow in shallow pans and gutters. The assessment of
required capacity and the sizing of the respective components of the drainage system are
based on the anticipated runoff from the 100-year storm event.
The surface runoff will culminate into the rain garden at the northwest portion of the site.
The pond outlet will consist of a 100-year drop inlet outlet structure. Flows above the
required WQCV will be released into the storm system via this outlet.
F. Modifications of Criteria
There are no modifications or variances requested in connection with the design of the
stormwater management for the Parking at 620 S. Lemay Avenue site development.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
The storm drainage system is designed to safely convey developed storm flows by sheet
flow and concentrated pan, underdrain, and gutter flow to the rain garden located at the
northwest corner of the property. The rain garden has been sized for the total required
WQCV and will safely release all flows greater than this into the storm system, as intended
to per the Poudre River Business Park, Filing One.
The design worksheets included in the Appendices to this Final Drainage Report present
details of the hydrologic and hydraulic calculations pertinent to the design of the on-site
storm drainage system. A drainage plan, showing the proposed development of the site and
developed drainage patterns is included in the map pocket following the Appendices.
B. Specific Details
There are a number of collection and conveyance scenarios within the drainage regime
associated with this development. The respective scenarios are described below.
Sub-basin B1, (0.99 acres), consists of asphalt/concrete, landscaped area, and natural
vegetation. Rainfall travels via overland flow from the center of the parking area to the
exterior of the lot, where it will concentrate in valley pans and will be conveyed to the rain
garden at a minimum of 0.6% slope, where the WQCV is treated. Overland flow will also
infiltrate the permeable pavers in the parking stalls, where it will be treated. The 100-year
flow is released via a 24” drop inlet into the back of the existing curb inlet located on the
south side of Poudre River Drive. After treatment within the rain garden and the permeable
pavers, the WQCV will also be released into the back of the curb inlet, where it will be
eventually be conveyed to the Poudre River. Sub-basin B1 produces a 100-year flow of
4.29 cfs. If the paver system overflows due to clogging, the runoff will be directed to the
rain garden where it will be treated and released through the outlet structure.
Sub-basin OS1 accounts for the south half of the Poudre River Drive extension. Rainfall in
this basin will travel via overland flow where it will concentrate in gutter flow and travel
west to the existing curb inlet on the southeast side of Poudre River Drive and Hoffman Mill
Road. From this inlet, flow will be conveyed through the existing system to the Poudre
River. Sub-basin OS1 produces a 100-year flow of 1.26 cfs.
Sub-basin OS2 accounts for the Hoffman Mill Road extension. Rainfall in this basin will
travel via overland flow where it will concentrate in gutter flow and travel south where it
meets the existing Hoffman Mill Road. From this point, it will be conveyed as it has
historically. Sub-basin OS2 produces a 100-year flow of 0.88 cfs.
C. Rain Garden
The rain garden has been designed to accommodate volume and release requirements for the
proposed site in its entirety. The WQCV required is 490 cubic feet. The WQCV infiltrates
completely through the rain garden media. At a depth of 5 inches, the rain garden requires a
flat surface area of 327 square feet; a flat surface area of 390 square feet has been provided.
The outlet structure has been designed to release the flows above the WQCV into the storm
sewer system. A 6” PVC underdrain will be installed beneath the rain garden. A detail of
this rain garden has been provided in the attached map pockets.
The entire overflow from the rain garden and the permeable pavers will be conveyed
through the rain garden outlet structure and to the existing storm system to the north. This
existing storm sewer system has the capacity to convey the entire 100-year flow from the
proposed development.
There will be no new facilities required offsite for the conveyance of the minor or major
flows to the Poudre River.
V. CONCLUSIONS
A. Compliance with Standards
The drainage design for the Parking at 620 S. Lemay Avenue is in compliance with the
requirements of the City of Fort Collins Storm Drainage Design Criteria and Construction
Standards Manual as well as the City’s floodplain regulations. The criteria and
recommendations of the Urban Storm Drainage Criteria Manual are also reflected in the
design of the drainage systems.
B. Drainage Concept
The drainage design for the Parking at 620 S. Lemay Avenue will be adequate to safely
convey onsite and offsite flows through the development. Development of the site, as
proposed, should have a beneficial impact on water quality in downstream drainage
facilities and drainage ways by reducing and delaying the initial discharge of runoff from
the site such that sediments and other potential pollutants typically carried by this first flush
are removed from the flow.
VI. REFERENCES
“City of Fort Collins Stormwater Criteria Manual”, City of Fort Collins, Adopted December
2011
“City of Fort Collins Municipal Code”, Chapter 10 – Flood Protection and Prevention City of
Fort Collins, 1987
Urban Storm Drainage Criteria Manual, Volumes 1, 2, and 3, Urban Drainage and Flood Control
District, April 2008
VII. APPENDICIES
APPENDIX A: Hydrologic Computations
Vicinity Map
FEMA FIRM Exhibit
USGS Soil Map
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO-3 Recommended Percentage Imperviousness Values
Rational Method Calculated Composite C Tables
Rational Method Calculated Imperviousness
Rational Method Calculated Flows
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DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
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.
C K 1 . 31 i 3 1 . 44 i 2 1 . 135 i 0 . 12
A A for CA 0, otherwise CA = 0 (RO-6)
C K 0 . 858 i 3 0 . 786 i 2 0 . 774 i 0 . 04
CD CD (RO-7)
C 2
B A CD
C C
2007-01 RO-9
Urban Drainage and Flood Control District
Composite C Values
620 S. LEMAY AVE. PARKING EXPANSION
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Roofs (acres) Lawns (acres) Total Area Minor (2-YR) Major (100-YR)
(C = 0.95) (C = 0.95) (C = 0.50) (C = 0.95) (C = 0.15) (acres) Composite "C" Composite "C" (Cf x C)
P1 E1 0.00 0.00 0.00 0.00 0.99 0.99 0.15 0.19
D1 B1 0.35 0.06 0.00 0.00 0.59 0.99 0.48 0.59
D2 OS1 0.07 0.03 0.00 0.00 0.02 0.13 0.80 0.99
D3 OS2 0.05 0.02 0.00 0.00 0.04 0.11 0.66 0.83
Notes:
Composite C values obtained from Table R0-11
Major Storm Runoff factored per Table R0-12
Developed
Design Point Basin(s)
Existing
MAP 620 LEMAY_City of Fort Collins Rational Method.xlsx 5/5/2015
Impeviousness
620 S. LEMAY PARKING EXPANSION
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Roofs (acres) Lawns (acres) Total Area Percent
(I = 100) (I = 100) (I = 40) (I = 90) (I = 0) (acres) Imperviousness
P1 E1 0.000 0.000 0.0000 0.0000 0.9900 0.9900 0%
D1 B1 0.35 0.06 0.00 0.00 0.59 0.99 41%
D2 OS1 0.07 0.03 0.00 0.00 0.02 0.13 81%
D3 OS2 0.05 0.02 0.00 0.00 0.04 0.11 64%
Notes:
Percent Impervious Values per Table R0-3, Urban Drainage Manual
Developed
Design Point Basin (s)
Existing
CAG 620 LEMAY_City of Fort Collins Rational Method.xlsx 5/5/2015
Basin Flow Calculations
620 S. LEMAY PARKING EXPANSION
Area Minor Major
(acres) Composite "C" Composite "C" Length (ft) Slope (%)
Minor tov
(min)a
Major tov
(min)a Length (ft)
Slope
(%)
Channel
Type
Velocity
(fps)c tt (min)
Minor TC
(min)
Major TC (min) 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr
P1 E1 0.9900 0.15 0.19 175 0.82 25.11 24.12 0 0.00 HM 0.00 0.00 25.11 24.12 1.43 2.44 5.09 0.21 0.36 0.94
D1 B1 0.9900 0.48 0.59 123 1.00 12.93 10.48 113 1.00 PA 2.00 0.9417 13.88 11.42 1.92 3.29 7.29 0.90 1.55 4.29
D2 OS1 0.1275 0.80 0.99 18 2.00 1.92 0.67 97 0.50 PA 1.41 1.1373 5.00 5.00 2.85 4.87 9.95 0.29 0.49 1.26
D3 OS2 0.1070 0.66 0.83 36 2.00 3.91 2.43 70 0.50 PA 1.41 0.8250 5.00 5.00 2.85 4.87 9.95 0.20 0.34 0.88
D4 - - - - - - - - - - - - - - - - - - 1.39 2.39 6.43
Notes:
a
b
HM = Heavy Meadow, TF = Tillage/field, PL = Short pasture and lawns, BG = Nearly bare ground, GW = Grassed Waterway, PA = Paved Areas
c
Velocity alues from Figure 3-3/Table RO-2 Estimate of Average Flow Velocity for use with the Rational Method
Design
Point
Developed
Existing
Initial/Overland Time Final TC Intensity (in/hr) Basin Flows (cfs)
Basin (s)
Travel Time
1 / 3
1 . 87 ( 1 . 1 ) 1 / 2
S
CC D
t f
ov
−
=
CAG 620 LEMAY_City of Fort Collins Rational Method.xlsx 5/5/2015
APPENDIX B: Hydraulic Computations
Rain Garden Outlet Area Inlet Calculation
Rain Garden Outlet Pipe Calculation
4.29
0.32
RAIN GARDEN OUTLET
Hydraulic Analysis Report
Project Data
Project Title:
Designer:
Project Date: Wednesday, March 04, 2015
Project Units: U.S. Customary Units
Notes:
Channel Analysis: RAIN GARDEN OUTLET PIPE
Notes:
Input Parameters
Channel Type: Circular
Pipe Diameter: 1.2500 ft
Longitudinal Slope: 0.0249 ft/ft
Manning's n: 0.0120
Flow: 4.2900 cfs
Result Parameters
Depth: 0.5409 ft
Area of Flow: 0.5088 ft^2
Wetted Perimeter: 1.7947 ft
Average Velocity: 8.4323 ft/s
Top Width: 1.2386 ft
Froude Number: 2.3186
Critical Depth: 0.8386 ft
Critical Velocity: 4.9010 ft/s
Critical Slope: 0.0060 ft/ft
Critical Top Width: 1.1747 ft
Calculated Max Shear Stress: 0.8404 lb/ft^2
Calculated Avg Shear Stress: 0.4404 lb/ft^2
APPENDIX C: Water Quality Design Calculations
UD BMP Rain Garden Calculations
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 41.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.410
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.15 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 43,124 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 524.6 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 = 5 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 = 350 sq ft
D) Actual Flat Surface Area AActual = 390 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 2445 sq ft
F) Rain Garden Total Volume VT= 591 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 1.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 525 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.61 in
Design Procedure Form: Rain Garden (RG)
MAP
QUALITY ENGINEERING
March 4, 2015
620 S. LEMAY AVE.PARKING EXPANSION
FORT COLLINS, COLORADO
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_RAIN GARDEN.xlsm, RG 3/4/2015, 3:49 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)
MAP
QUALITY ENGINEERING
March 4, 2015
620 S. LEMAY AVE.PARKING EXPANSION
FORT COLLINS, COLORADO
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_RAIN GARDEN.xlsm, RG 3/4/2015, 3:49 PM
APPENDIX D: Standard Operating Procedures
Standard Operating Procedures
Page 1 of 2
STANDARD OPERATING PROCEDURES (SOPs)
Parking at 620 S. Lemay Avenue, Fort Collins, CO
A. PURPOSE
In order for physical stormwater Best Management Practices (BMPs) to be effective, proper
maintenance is critical. Maintenance includes both routinely scheduled activities, as well as non-
routine repairs that may be required after large storms, or as a result of other unforeseen problems.
Standard Operating Procedures (SOPs) should clearly identify BMP Maintenance responsibility.
BMP maintenance is typically the responsibility of the entity owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is
allocated for maintenance is critical to the long-term success of BMPs. Maintenance responsibility
may be assigned either publicly or privately. For this project, the privately owned BMPs shown in
Section B below are to be maintained by the property owner, homeowner’s association (HOA), or
property manager.
B. BMPS SUBJECT TO SOP REQUIREMENTS
The following stormwater facilities contained within the Parking at 620 S. Lemay Avenue project are
subject to SOP requirements:
- Rain Garden Detention Basin (RG)
- Storm Sewers and Tree Roots
- Permeable Pavers (PP)
The location of said facilities can be found on the Site Plan, Landscape Plans, and Utility Plans for
Parking at 620 S. Lemay Avenue.
C. SITE-SPECIFIC STANDARD OPERATING PROCEDURES
Inspection and maintenance procedures and frequencies, specific maintenance requirements and
activities, as well as BMP-specific constraints and considerations shall follow the guidelines outlined
in volume 3 of the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage
Criteria Manual, latest revision. The Storm Sewer maintenance procedures follow. The Storm Sewer
Lines (Table 1), Rain Garden (Table 2), and Permeable Pavers (Table 3) maintenance plans are as
follows:
Storm Sewer Lines Maintenance Plan
The storm sewer lines are located in close proximity to many trees. The situation is unavoidable;
therefore, special maintenance has been identified to ensure these storm drain systems perform as
they were designed. In addition, Inlets and outlet rip-rap will need to be maintained.
Page 2 of 2
Table 1 – Routine Storm Sewer Line Maintenance
Required Action Maintenance Objective Frequency of Action
Line Inspections
Use a video camera to inspect the
condition of the storm sewer
pipes. Cleanout pipes as needed.
If the integrity of the pipe is
compromised, then repair the
damaged section(s).
Routine -Annual inspection of
hydraulic and structural facilities.
Also check for obvious problems
during routine maintenance visits,
especially for plugging of outlets.
Inlet Inspections
Inspect and clean inlet weirs and
boxes of any debris.
Routine – Annual inspection of
inlets to ensure proper operation
and prevent plugging.
Riprap Outlet Protection
Inspections
Maintain riprap (rock) storm
sewer outlet protection to ensure
proper operation.
Routine – Annual inspection of
riprap to replace dislodged stones,
remove debris, etc.
Rain Garden Maintenance Plan
Table 2 – Routine EDB Maintenance (Summary from Table EDB-1, Chapter 6 of UDFCD)
Required Action Maintenance Objective Frequency of Action
Lawn mowing and Lawn care
Occasional mowing to limit
unwanted vegetation. Maintain
irrigated turf grass as 2 to 4 inches
tall and non-irrigated native turf
grasses at 4 to 6 inches.
Routine - Depending on aesthetic
requirements.
Sediment, Debris, and Litter
removal
Removal of sediment, debris, and
litter from the entire pond to
minimize outlet clogging and
improve aesthetics.
Routine - Including just before
annual storm seasons (April and
May), end of storm season after
leaves have fallen, and following
significant rainfall events.
Major Pond Sediment removal*
Remove accumulated sediment from
the bottom of the basin.
Non-routine - Performed when
sediment accumulation occupies 20
percent of the WQCV. This may vary
considerably, but expect to do this
every 10 to 20 years, as necessary per
inspection if no construction activities
Page 3 of 2
Permeable Paver Maintenance Plan
Table 3 – Routine EDB Maintenance (Summary from Table PPS-1, Chapter 6 of UDFCD)
Required Action Maintenance Objective Frequency of Action
Snow Removal
Remove snow and ice from the
pavement system by plowing.
Conventional plowing should not
cause damage to the pavement.
Do not use sand.
Routine – After all snow storms.
Debris Removal, Sweeping, and
Vacuuming
Removal of sediment, debris, and
litter from the pavement system to
minimize clogging and improve
aesthetics.
Routine – Broom sweep
frequently (weekly or monthly)
and vacuum sweep as needed
(monthly or yearly).
Full and Partial Replacement of
Pavement or Infill Material
If surface is completely clogged and
rendering a minimal surface
infiltration rate, restoration of surface
infiltration can be achieved by
removing the first 1” of soiled
aggregate infill with a vacuum
sweeper. After cleaning, refill with
clean aggregate infill material.
Non-routine – Perform as needed.
00 10' 20' 40'
1"=20'
DRAINAGE PLAN
FOR BURIED UTILITY INFORMATION
THREE (3) BUSINESS DAYS
BEFORE YOU DIG
CALL 811
(OR 1-800-922-1987)
UTILITY NOTIFICATION
CENTER OF COLORADO (UNCC)
WWW.UNCC.ORG
R
CITY OF FORT COLLINS, COLORADO
UTILITY PLAN APPROVAL
C4.0
PARKING AT 620 S. LEMAY AVE.
620 S. LEMAY AVENUE
FORT COLLINS, CO 80524
POUDRE RIVER BUSINESS PARK, FOURTH FILING
C8.5
PARKING AT 620 S. LEMAY AVE.
620 S. LEMAY AVENUE
FORT COLLINS, CO 80524
POUDRE RIVER BUSINESS PARK, FOURTH FILING
5.04" Ponding Depth
(MODIFED) BIORETENTION / BIOSWALE CROSS SECTION
6" Perforated PVC Pipe
10" Thick Layer of CDOT No. 4
Aggregate
EL. = 4954.00
EL. = 4954.42
(MODIFED) INTERLOCKING CONCRETE PAVERS CROSS SECTION
6" Perforated PVC Pipe Sub-Drain
12" Layer of #2
Rock Sub-Base
6" Layer of #57
Base
Elev. = 4957.14
Inv Elev. = 4955.27
Elev. = 4956.27
Elev. = 4956.77
take place in the tributary watershed.
More often if they do.
Inspections
Inspect basins to insure that the basin
continues to function as initially
intended. Examine the outlet for
clogging, erosion, slumping,
excessive sedimentation levels,
overgrowth, embankment and
spillway integrity and damage to any
structural element.
Every two to five years.
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