HomeMy WebLinkAboutPROSPECT SPORTS CLUB - FDP240002 - SUBMITTAL DOCUMENTS - ROUND 2 - Responses (2)FINAL DRAINAGE REPORT
19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | 970-530-4044 | www.unitedcivil.com
P ROSPECT S PORTS
Lot 5
Prospect Park East P.U.D
Fort Collins, CO
Prepared for:
RB+B Architects, Inc.
315 E. Mountain Ave, Suite 100
Fort Collins, CO 80524
Date:
April 2 nd , 2024
Fort Collins Utilities Redlines
Water, Wastewater & Stormwater
Thank you for the opportunity to review the se plans.
I encourage you to contact me to discuss questions &
revisions prior to resubmittal.
dmogen@fcgov.com or 970-305-5989
Reviewed by:
Date :
Dan Mogen
04/26/2024
F INAL D RAINAGE R EPORT
P ROSPECT S PORTS
F ORT C OLLINS ,CO
i U22014_Drainage Report
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Prospect Sports
Fort Collins, Colorado
Project Number: U22014
Dear Staff:
United Civil Design Group, LLC. is pleased to submit this Preliminary Drainage Report for the Prospect Sports site in Fort
Collins, Colorado. In general, this report serves to document the stormwater impacts associated with the proposed
improvements related to the existing site.
We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in
the Fort Collins Stormwater Criteria Manual (FCSCM). This report was prepared in compliance with technical criteria set forth
in the Fort Collins Stormwater Criteria Manual.
If you should have any questions or comments as you review this report, please feel free to contact us at your convenience.
Sincerely,
United Civil Design Group
Nate Stroud, PE, LSIT
Project Manager
COMPLIANCE STATEMENT
I hereby attest that this report for the Final drainage design for Prospect Sports was prepared by me or under my direct
supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of
Fort Collins does not and will not assume liability for drainage facilities designed by others.
Registered Professional Engineer
State of Colorado No. 52985
update UCDG Response:Updated.
F INAL D RAINAGE R EPORT
P ROSPECT S PORTS
F ORT C OLLINS ,CO
6 U22014_Drainage Report
Basin EX1
Basin EX1 represents on-site runoff that drains to the existing property to the south and ultimately to the detention pond
within Tract A of the Prospect Park East P.U.D. There is a very small portion of this basin that has existing public concrete
sidewalk, but the majority of the existing site is undeveloped.
Proposed Basins
The following basins provide proposed drainage delineations for the site in its improved condition. Refer to Appendix A for
hydrology computations and Appendix B for calculations related to Water Quality, Low Impact Development, and other
hydraulic features.
Basin A
Sub-basins A1-A8 (see Drainage Plans attached) include the area of the site being collected by the proposed storm sewer
infrastructure and are a majority of the site. These basins consist of roofs, asphalt and concrete paving, and landscaping.
Runoff within these basins is conveyed to grass swales and bioretention ponds via sheet flow, curb, inlets, and storm sewer.
Ultimately runoff is conveyed through the proposed storm sewer to the existing lake/pond across Sharp Point and ultimately
released to the Cache La Poudre River.
Basin OS1
Basin OS1 represents the portion of the proposed site draining offsite to the south undetained. This basin consists of concrete
sidewalk, asphalt pavement, and landscaping. In its improved condition, this basin will continue to function as most of the
existing site did with conveying flows offsite to the south property and ultimately to the detention pond within Tract A of the
Prospect Park East P.U.D. There is also proposed asphalt offsite, to the south of Basin OS1 that will be conveyed to the south
with flows from Basin OS1. Although there are some pervious areas being directed to the south, it should be noted that the
original drainage report showed all of the developed site being conveyed south. Because of this and the minimal pervious
areas being conveyed south in the proposed condition, no negative impacts are foreseen.
Detention and Water Quality
No detention is being provided for the site due to previously discussed site constraints and as documented in the variance
request. However, water quality is provided and will be achieved through the use of bioretention ponds per the Fort Collins
Stormwater Criteria Manual.
Low Impact Development (LID)
In December of 2015, Fort Collins City Council adopted the revised Low Impact Development (LID) policy and criteria which
requires developments within City limits to meet certain enhanced stormwater treatment requirements in addition to more
standard treatment techniques. The proposed development will be required to meet the newly adopted LID criteria which
requires the following:
-Treat no less than 75% of any newly added impervious area using one or a combination of LID techniques.
-Treat no less than 50% of any newly added impervious area using one or a combination of LID techniques when at
least 25% of any newly added pavement is provided with permeable pavement.
The following measures are implemented with this proposed development:
I.Northern Bioretention Pond
Basins A5, A6, and A 8.1, combined for 5,905-sf of proposed composite impervious area, are designed to be conveyed
to the northern bioretention pond. The proposed impervious area treated through the bioretention ponds includes
roof areas, and landscaping. All bioretention ponds will be designed with underdrains which will be conveyed to the
proposed storm sewer onsite.
It should be noted that groundwater was encountered during boring for geotechnical analysis of the soil in December
of 2022. With the bioretention ponds, groundwater would have a negative impact on how the system functions as
it relates to water quality and LID purposes. After analyzing groundwater depths in this area, groundwater would
be at a depth of approximately 8 feet below existing ground, corresponding to an elevation of 4893.50. The bottom
impervious?impervious?
UCDG Response:Correct,
this has been updated.UCDG Response:Correct,
this has been updated.
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =27.1 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.271
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.11 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area)Area = 21,787 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =206 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 =6 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 =118 sq ft
D) Actual Flat Surface Area AActual =848 sq ft
E) Area at Design Depth (Top Surface Area)ATop =1900 sq ft
F) Rain Garden Total Volume VT=687 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 =0.5 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =206 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =7/16 in
Design Procedure Form: Rain Garden (RG)
NKS
United Civil Design Group
March 11, 2024
Prospect Park
North Bioretention Pond
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07 Bio Ponds north, RG 3/11/2024, 9:55 AM
please remove orifice
calc. FC does not
include orifices on the
underdrain.
UCDG Response:This has
been removed.
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)
NKS
United Civil Design Group
March 11, 2024
Prospect Park
North Bioretention Pond
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.07 Bio Ponds north, RG 3/11/2024, 9:55 AM
Complete?
UCDG Response:This has
been completed but excel
sheet would not let us
choose an option for both
#5 and #8,just one or the
other.We answered #5
and #8 will be a no.
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =52.3 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.523
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.17 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area)Area = 87,317 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =1,238 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 =913 sq ft
D) Actual Flat Surface Area AActual =998 sq ft
E) Area at Design Depth (Top Surface Area)ATop =2331 sq ft
F) Rain Garden Total Volume VT=1,665 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 =1.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =1,238 cu ft
iii) Orifice Diameter, 3/8" Minimum DO =15/16 in
Design Procedure Form: Rain Garden (RG)
NKS
United Civil Design Group
March 19, 2024
Prospect Park
Southern Bioretention Pond
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07 Bio Ponds south, RG 3/19/2024, 1:54 PM
please remove orifice
calc. FC does not
include orifices on the
underdrain.
UCDG Response:This has
been removed.