HomeMy WebLinkAbout221 EAST MOUNTAIN AVENUE - BASIC DEVELOPMENT REVIEW - BDR180012 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
April 25, 2018
Mr. Wes Lamarque
Fort Collins Utilities – Stormwater
700 Wood Street
Fort Collins, CO 80522
Re: 221 East Mountain
Preliminary Storm Drainage Letter
Dear Wes,
Please accept the following letter describing the storm drainage intent demonstrating the proposed site
improvement’s ability to comply with the City’s stormwater requirements.
INTRODUCTION
The 221 East Mountain is a redevelopment project proposed to construct a mixed-use condominium
building with supporting utility infrastructure and site accesses (pedestrian/vehicular). The site is located
at the southwest corner of the intersection of E. Mountain Ave and Mathews St. There is a 20’ public
alley to the south, and 10’ public alley along the west. The roadway frontages will be improved along E.
Mountain Ave and Mathews St, along with the alleys to the south and west. The legal description is as
follows: Lots 1 thru 6, Block 131, Town of Fort Collins, located in part of the Northwest Quarter of
Section 12, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County
of Larimer, State of Colorado. The property is addresses as 221 E. Mountain Ave.
A vicinity map is attached for reference.
EXISTING CONDITIONS
The project site is located within the Udall drainage basin. The existing site consists of a vehicle
maintenance shop/showroom, and a parking lot. The site is approximately 0.45 acres and is impervious
except for a 40 sqft gravel area near the existing vehicle entrance off of E. Mountain Ave. The site
generally slopes to the east at 1.0% grade. Approximately 4,250 sqft drains to E. Mountain Ave, and the
remaining drains to Mathew St. All existing improvements will be removed from the site to
accommodate the new construction. The existing southern alley is entirely paved and the existing western
alley appears to be unimproved.
We are not aware of any site-specific drainage studies for this site.
The project is not located within a FEMA mapped 100-yr floodplain and is not within a defined City of
Fort Collins floodplain.
221 East Mountain
Preliminary Storm Drainage Letter
April 25, 2018
Page 2 of 4
PROPOSED DEVELOPMENT
The prosed redevelopment improvements will consist of a constructing a 4-story mixed-use multi-family
condominium building, with below grade parking, and will include the supporting utility infrastructure
and pedestrian/vehicle accesses. The project is planned to be constructed in a single phase.
The project has zero setback requirements, encouraging zero-lot line construction. The proposed building
footprint is approximately 18,365 sqft, consuming 94% of the site. The improvements will generally be
100% impervious, consistent with the existing conditions. The proposed improvements are divided into 3
onsite drainage basins and 2 offsite drainage basins:
Basin D1 consists of the northwest quarter of the proposed roof area and the runoff will be conveyed
through storm drains to the existing inlet on E. Mountain Ave.
Basin D2 consists of the south half of the proposed roof area. Runoff from this basin will be piped to a
rain garden before discharging to the curb and gutter along Mathews street and conveyed to an existing
inlet.
Basin D3 consists of the northeast quarter of the proposed roof area. Similar to Basin D3, runoff from
this basin will be piped to a rain garden before discharging to the curb and gutter along Mathews street
and conveyed to an existing inlet.
Basin OS1 consists of the southern alley. The proposed drainage patterns of this basin will not change
from existing, draining along the improved alley east to Mathews Street.
Basin OS2 consists of the western alley. This alley will be paved and the runoff from this alley will be
collected in an area inlet and conveyed to the existing inlet on E. Mountain Ave.
The proposed improvements do not create an increase in impervious area over 5,000 sq-ft which would
require onsite detention. Standard water quality is provided downstream within the Udall Basin and is not
required onsite. A combination of a rain garden and tree planters are proposed to provide water quality
enhancement and are designed to satisfy the Low Impact Development (LID) requirements.
All calculations and exhibits are attached for reference.
LOW IMPACT DEVELOPMENT TECHNIQUES
In reference to the code requirements for implementation of Low Impact Development (LID) techniques,
the use of a bioretention rain garden and tree planters are necessary to satisfy these requirements. The rain
garden will promote infiltration while capturing fine sediment that drains off the impervious areas. The
tree planter will allow ponding and promote infiltration. A baffled sidewalk chase will direct runoff to the
rain garden and tree planters. When runoff rates exceed the infiltration rates of the rain gardens, runoff
will spill out the chase to the adjacent roadway curb and gutter. Due to the zero-lot line construction,
implementing LID features on site is not feasible. Similar to recent projects constructed in the vicinity of
this project, it is proposed that the LID features be constructed within the right-of-way. It is expected that
a right-of-way encroachment permit will be required and will specify the maintenance responsibility of
these features. Due to site and building constraints, approximately 70% of the site will be treated through
the proposed LID features. A Standard Operations Procedure will be provided at final design to assist in
ensuring that these BMPs will adequately perform over time.
221 East Mountain
Preliminary Storm Drainage Letter
April 25, 2018
Page 3 of 4
Below is a description of the 4 step process for selecting structural BMPs:
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 from majority of the building will be conveyed to rain gardens and tree planters via roof drains
and storm drains. The rain gardens and tree planters will slow runoff, promote infiltration, and filter
runoff prior to being released into the adjacent storm drain system.
Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release
The rain gardens and tree planters will provide a slow release by infiltration through the growing media.
A perforated pipe will drain the rain grades. Water quality capture volume is provided downstream
within the Udall Basin.
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 an existing
roadway and storm system, bank stabilization is unnecessary with this project.
Step 4: Implement Site Specific and Other Source Control BMPs
Proactively controlling pollutants at their source by preventing pollution rather than removing
contaminants once they have entered the stormwater system or receiving waters is important when
protecting storm systems and receiving waters. This can be accomplished through site specific needs
such as construction site runoff control, post-construction runoff control and pollution prevention / good
housekeeping. It will be the responsibility of the contractor to develop a procedural best management
practice for the site.
All calculations are attached for reference.
EROSION CONTROL
Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet protection, a
gravel construction entrance, seeding, mulch, and turf. The measures are designed to limit the overall
sediment yield increase due to construction as required by the City of Fort Collins. During overlot and
final grading the soil will be roughened and furrowed perpendicular to the prevailing winds.
During the performance of the work required by these specifications or any operations appurtenant
thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor,
equipment, materials, and means required. The Contractor shall carry out proper efficient measures
221 East Mountain
Preliminary Storm Drainage Letter
April 25, 2018
Page 4 of 4
wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from
his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing naissance to
persons. The Contractor will be held liable for any damage resulting from dust originating from his
operations under these specifications on right-of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-way.
Wherever construction vehicles access routes or intersect paved public roads, previsions must be made to
minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. Stabilized
construction entrances are required with base material consisting of 6” coarse aggregate. The contractor
will be responsible for clearing mud tracked onto city streets on a daily basis.
All temporary and permanent erosion and sediment control practices must be maintained and repaired as
needed to assure continued performance of their intended function. Silt fence and sediment control logs
will require periodic replacement. Maintenance is the responsibility of the contractor.
All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall not be
considered established until a ground cover is achieved which is demonstrated to be mature enough to
control soil erosion to the satisfaction of the City Inspector and to survive severe weather condition.
Thank you in advance for your time and if you have any questions or comments please contact me at
(970) 347-8917.
Sincerely,
Jason T. Claeys, P.E., LEED AP
Interwest Consulting Group
Attachments
SITE
MULBERRY STREET
COLLEGE AVE
LEMAY AVE
RIVERSIDE AVENUE
VINE DRIVE
PROJECT VICINITY MAP
N.T.S.
PROJECT VERTICAL DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK 1-13: SOUTHWEST CORNER OF COLLEGE AVE. AND
MAPLE ST., ON A CONCRETE TRAFFIC SIGNAL BASE.
ELEVATION = 4979.75 (NAVD88)
FORT COLLINS BENCHMARK 5-00: LOCATED ON THE TOP OF A CURB OF A SIGNAL POLE
BASE AT THE NORTHWEST CORNER OF LINDEN ST. AND JEFFERSON ST.
ELEVATION = 4978.05 (NAVD88)
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM. SURROUNDING
DEVELOPMENTS HAVE USED NGVD29 UNADJUSTED FOR THEIR VERTICAL DATUMS.
IF NGVD UNADJUSTED DATUM IS REQUIRED FOR ANY PURPOSE, THE FOLLOWING
EQUATION SHOULD BE USED:
NGVD UNADJUSTED = 4979.75 (NAVD88) - 3.17 = 4976.58
NGVD UNADJUSTED = 4978.05 (NAVD88) - 3.18 = 4974.87
Design Engineer:
Design Firm:
Project Number:
Date:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf
)
100% 0.95
2-year to
10-year
1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
0% 0.25
C2
to C10
C100
D1 4,892 0.11 280 4,611 0 0 0 90.6% 0.95 1.00
D2 9,659 0.22 555 9,104 0 0 0 90.6% 0.95 1.00
D3 4,946 0.11 296 4,649 0 0 0 90.6% 0.95 1.00
Overall 19,496 0.45 1,131 18,364 0 0 0 90.6% 0.25 0.31
OS1 1,296 0.03 1,296 0 0 0 0 100.0% 0.95 1.00
OS2 4,203 0.10 4,203 0 0 0 0 100.0% 0.95 1.00
221 East Mountain
DEVELOPED IMPERVIOUS AREA CALCULATION
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
BASINS:
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
J.Claeys
Interwest Consulting Group
1324-028-00
April 25, 2018
Land Use
Paved
Roof
Walks
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Gravel/Pavers
Lawns
(Heavy, 2-7% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
Weighted %
Impervious
A COMPOSITE
paved
(sq feet)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
Type of Travel
Surface
Cv
D1 D1 90.6% 0.95 0.112 51 0.0100 2.01 32 0.0100 Paved Areas 20 2.00 0.27 5.00 0.0100 5.00 5.00
D2 D2 90.6% 0.95 0.222 53 0.0100 2.04 108 0.0100 Paved Areas 20 2.00 0.90 5.00 0.0100 5.21 5.00
D3 D3 90.6% 0.95 0.114 52 0.0100 2.01 37 0.0100 Paved Areas 20 2.00 0.31 5.00 0.0100 5.00 5.00
OS1 OS1 100.0% 0.95 0.030 15 0.0595 0.60 188 0.0130 Paved Areas 20 2.28 1.38 5.00 0.0164 5.00 5.00
OS2 OS2 100.0% 0.95 0.096 9 0.0180 0.71 88 0.0153 Paved Areas 20 2.47 0.59 5.00 0.0156 5.00 5.00
-Urbanized Check Equation 6-5
April 25, 2018
221 East Mountain
DEVELOPED TIME OF CONCENTRATION
J.Claeys
Interwest Consulting Group
1324-028-00
LENGTH
(ft)
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Overland Flow Equations for City of Fort Collins - Storm Water Criteria Manual
SUB-BASIN DATA
INITIAL/OVERLAND TIME
(ti)
TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)
DESIGN
POINT
Sub-basin
%
Impervious
C2-10
AREA
(acres)
tt
(min)
OVERALL SLOPE
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (100-yr)
Type of Travel
Surface
Cv
D1 D1 90.6% 1.00 0.112 51 0.0100 1.34 32 0.0100 Paved Areas 20 2.00 0.27 5.00 0.0100 5.00 5.00
D2 D2 90.6% 1.00 0.222 53 0.0100 1.36 108 0.0100 Paved Areas 20 2.00 0.90 5.00 0.0100 5.21 5.00
D3 D3 90.6% 1.00 0.114 52 0.0100 1.34 37 0.0100 Paved Areas 20 2.00 0.31 5.00 0.0100 5.00 5.00
OS1 OS1 100.0% 1.00 0.030 15 0.0595 0.40 188 0.0130 Paved Areas 20 2.28 1.38 5.00 0.0164 5.00 5.00
OS2 OS2 100.0% 1.00 0.096 9 0.0180 0.47 88 0.0153 Paved Areas 20 2.47 0.59 5.00 0.0156 5.00 5.00
-Urbanized Check Equation 6-5
April 25, 2018
221 East Mountain
DEVELOPED TIME OF CONCENTRATION
J.Claeys
Interwest Consulting Group
1324-028-00
LENGTH
(ft)
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Overland Flow Equations for City of Fort Collins - Storm Water Criteria Manual
SUB-BASIN DATA
INITIAL/OVERLAND TIME
(ti)
TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)
DESIGN
POINT
Sub-basin
%
Impervious
C100
AREA
(acres)
tt
(min)
OVERALL SLOPE
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS: I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs) P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-2yr = 0.82 in
A n = Basin drainage area (ac) P 1-10yr = 1.40 in
P 1-100yr = 2.86 in
BASIN SUMMARY:
tc (min)
Runoff Coeff
(C2-10)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s) tc (min)
Runoff Coeff
(C2-10)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s) tc (min)
Runoff Coeff.
(C100)
C(A) (acres)
Intensity
(in/hr)
Q (ft3/s)
D1 D1 0.112 5.00 0.95 0.11 2.78 0.30 5.00 0.95 0.11 4.87 0.52 5.00 1.00 0.11 9.95 1.12
D2 D2 0.222 5.00 0.95 0.21 2.78 0.58 5.00 0.95 0.21 4.87 1.03 5.00 1.00 0.22 9.95 2.21
D3 D3 0.114 5.00 0.95 0.11 2.78 0.30 5.00 0.95 0.11 4.87 0.53 5.00 1.00 0.11 9.95 1.13
OS1 OS1 0.030 5.00 0.00 0.00 2.78 0.00 5.00 0.00 0.00 4.87 0.00 5.00 0.00 0.00 9.95 0.00
OS2 OS2 0.096 5.00 0.95 0.09 2.78 0.25 5.00 0.95 0.09 4.87 0.45 5.00 1.00 0.10 9.95 0.96
10-yr Peak Runoff 100-yr Peak Runoff
221 East Mountain
DEVELOPED PEAK RUNOFF
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
DESIGN CRITERIA:
Design
Point
Sub-basin Area (acres)
J.Claeys
Interwest Consulting Group
1324-028-00
April 25, 2018
2-yr Peak Runoff
Q n = C n I n A n
0.786651)
1
( 10 )
28 . 5
t c
P
I
+
=
1324-028-00 Rational Calcs (FC).xlsx Page 4 of 4 Interwest Consulting Group
Low Impact Development
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Low Impact Development Summary
Pavement Area Summary
1,131 sqft
0 sqft
0.0%
Developed Area Summary
19,496 sqft
Total Area required for Treatment (75%): 14,622 sqft
0 sqft
0 sqft
0 sqft
13,753 sqft
13,753 sqft
70.5%
221 East Mountain
Total New Impervious Area:
J.Claeys
Interwest Consulting Group
1324-028-00
April 25, 2018
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped impervious area using one or a combination of
LID techniques, or
- Treat at least 50% of any newly developed or redeveloped impervious area using one or a combination of
LID techniques when 25% of private driveable surfaces are permeable.
Total New Paved Area:
Permeable Paver Area:
Percent Pavement Area as Permeable Pavers:
Impervious Area Treated by Rain Garden:
Proposed Area of Pavers:
Additional Area Treated by Pavers:
Total Area Treated by Pavers:
Total Area Treated by LID:
Percent Site Area Treated by LID:
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 9,104 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 = 303.5 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 = 6 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 182 sq ft
D) Actual Flat Surface Area AActual = 183 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 183 sq ft
F) Rain Garden Total Volume VT= 92 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
Modified CoFC Rain Garden Section (12" Growing Media, 4" Pea Gravel
8" AASHTO Class 2)
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
J. Claeys
Interwest Consulting Group
April 25, 2018
221 East Mountain
Rain Garden (Basin D2)
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1324-028-00 UD-BMP_v3.06 (Basin D2).xlsm, RG 4/24/2018, 3:53 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)
J. Claeys
Interwest Consulting Group
April 25, 2018
221 East Mountain
Rain Garden (Basin D2)
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
1324-028-00 UD-BMP_v3.06 (Basin D2).xlsm, RG 4/24/2018, 3:53 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 4,946 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 = 164.9 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 = 6 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 99 sq ft
D) Actual Flat Surface Area AActual = 116 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 116 sq ft
F) Rain Garden Total Volume VT= 58 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
Modified CoFC Rain Garden Section (12" Growing Media, 4" Pea Gravel
8" AASHTO Class 2)
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
J. Claeys
Interwest Consulting Group
April 25, 2018
221 East Mountain
Rain Garden (Basin D3)
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1324-028-00 UD-BMP_v3.06 (Basin D3).xlsm, RG 4/24/2018, 3:54 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)
J. Claeys
Interwest Consulting Group
April 25, 2018
221 East Mountain
Rain Garden (Basin D3)
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
1324-028-00 UD-BMP_v3.06 (Basin D3).xlsm, RG 4/24/2018, 3:54 PM
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
��
=
1.87(1.1 − ��
��
) �
� �
1324-028-00 Rational Calcs (FC).xlsx Page 3 of 4 Interwest Consulting Group
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
��
=
1.87(1.1 − ��
��
) �
� �
1324-028-00 Rational Calcs (FC).xlsx Page 2 of 4 Interwest Consulting Group
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
1324-028-00 Rational Calcs (FC).xlsx Page 1 of 4 Interwest Consulting Group