HomeMy WebLinkAboutSUNSHINE HOUSE AT BUCKING HORSE - MJA190001 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENTFORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158
GREELEY: 820 8 th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com
January 23, 2019
City of Fort Collins - Stormwater
700 Wood Street
Fort Collins, Colorado 80524
RE: Bucking Horse Filing Two - Major Amendment
Fort Collins, Colorado
Dear Staff:
Bucking Horse Filing Two - Major Amendment (Sunshine House) is a proposal to change the
previously approved working farm to a daycare facility. The revised project will include a revised
building footprint and updated flatwork for the building’s new intended use. The existing concrete
parking lot will also be expanded slightly to add approximately six (6) parking spaces.
Drainage Patterns
The proposed site improvements will not alter the existing designed drainage patterns that were
approved with the original project. Drainage in the parking lot will generally flow to a series of inlets
in the middle of the lot and will be conveyed to Pond 215 via the existing storm drain. Runoff from
the building and playground will drain to Pond 215 via sheet flow or via a series of area drains and
swales.
Site Imperviousness
The previously approved impervious area of the site was 43,135 square feet. The proposed
impervious area of the Major Amendment is 42,399 square feet. This results in a net decrease of
736 square feet of impervious area.
Detention and Water Quality
The reduction in overall imperviousness noted above indicates that the detention volume originally
provided in Pond 215 will continue to be adequate and that no additional onsite detention will be
required. The decrease in impervious area also ensures that the water quality volume provided in
Pond 215 will also be able to serve the updated project.
Low Impact Development (LID)
Since the approval of Bucking Horse Filing Two, the City has adopted Low Impact Development
(LID) requirements that specify that either 75% of all newly added impermeable areas receive water
quality treatment from a LID facility OR 50% of new pavements be treated by a LID method along
with 25% of drivable surfaces being permeable pavers. Since the parking area for this project has
already been built, there are inherent difficulties meeting the exact requirements. However,
discussions with staff have acknowledged that the parking area is the area with the highest
pollutant loads and the highest priority for LID treatment. With that in mind, rain gardens have
FORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158
GREELEY: 820 8 th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com
been added to the center islands that will treat approximately 38% of the impervious areas onsite.
While a large portion of the remaining site will not receive LID treatment from a specific LID facility,
additional treatment will occur. In particular, the roof downspouts will discharge into landscaped
swales that will allow for the settling of particulates prior to entering the storm drain system. Also,
paved areas in the playground area will sheet flow across large, flat grass areas which will allow for
treatment of stormwater runoff from those areas.
Erosion and Sediment Control
During construction, the Contractor will follow the appropriate and applicable City of Fort Collins
standards for erosion and sediment control. This project disturbs more than 10,000 sf and is
contained in the originally approved Erosion Control Report. No changes to that report are needed
as a result of the changes proposed with this Major Amendment. Post construction water quality
and erosion control will be achieved by a fully established and stabilized site. All areas disturbed
during construction will receive permanent hardscape, landscape, or building structure.
Floodplains
This project falls within the FEMA 500-yr floodplain for the Poudre River. Normally, a Childcare
facility would not be allowed within this area, however, a waiver has been granted by the City
Water Board acknowledging that the proposed building is located several feet above the 500-yr
BFE. As such, future remapping using updated data is expected to show that the project site is
located outside of the actual 500-yr floodplain limit.
Conclusions
The proposed grading concept closely matches the original drainage patterns and decreases overall
site imperviousness and additional detention and water quality is proven to be unnecessary. The
project meets the city requirements for Low Impact Development treatment. Therefore, it is my
professional opinion that Bucking Horse Filing Two Major Amendment (Sunshine House) satisfies all
applicable stormwater criteria and will effectively limit potential damage associated with its
stormwater runoff.
Please do not hesitate to contact me if you have questions or require additional information.
Sincerely,
Andy Reese
Project Manager
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4
20 SF
CLASSROOM
9
HALL
11
1149 SF
BARN
12
6"
114 SF
OFFICE
15
115 SF
OFFICE
16
WOMENS
17
MENS
18
371 SF
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MILES HOUSE AVENUE
RAIN GARDEN
PROVIDED VOLUME: 585 CU. FT.
TREATMENT AREA: 15,494 SF
BUCKING HORSE FILING TWO -
MAJOR AMENDMENT
SHEET NO:
D:\PROJECTS\687-007\DWG\DRNG\687-007_LID.DWG
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
DRAWING REFERENCE:
LID TREATMENT EXHIBIT B. Ruch
1 in = 40 ft
January 23, 2019 LID-1
DRAWN BY:
SCALE:
ISSUED:
( IN FEET )
0
1 INCH = 40 FEET
40 40
LEGEND
UNTREATED AREA
RAIN GARDEN AREA
RAIN GARDEN
TREATMENT AREA
BUCKING HORSE FILING TWO - MAJOR AMENDMENT ON-SITE LID TREATMENT
Project Summary
Total Impervious Area 40,852 sf
Target Treatment Percentage 75%
Minimum Area to be Treated by LID
measures 30,639.00
sf
Rain Garden
Total Rain Garden Treatment Area 15,494 sf
Total Treatment Area 15,494 sf
Percent Total Project Area Treated 37.9%
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 = 15,494 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 516 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 = 9 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 = 310 sq ft
D) Actual Flat Surface Area AActual = 450 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 955 sq ft
F) Rain Garden Total Volume VT= 527 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 = 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)
A. Reese
Northern Engineering
January 23, 2019
Bucking Horse Sunshine House (Bucking Horse Filing 2 Major Amendment)
Fort Collins, CO
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.06_RG WQVol.xlsm, RG 1/23/2019, 9:43 AM
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
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
A. Reese
Northern Engineering
January 23, 2019
Bucking Horse Sunshine House (Bucking Horse Filing 2 Major Amendment)
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
UD-BMP_v3.06_RG WQVol.xlsm, RG 1/23/2019, 9:43 AM
TRACTOR / EQUIP.
STORAGE
19
COW MILKING
20
MILKING PREP
21
JAN.
22
MECH.
23
MILES HOUSE AVENUE
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MILES HOUSE AVENUE
ROOFTOP
CONCRETE
GRAVEL
SURFACE
AREA (SF) % IMPERV.
IMPERV.
AREA (SF)
6,478
36,657
0
100%
100%
40%
TOTALS 43,135 TOTAL= 43,135
ROOFTOP
CONCRETE
ASPHALT
SURFACE
AREA (SF) % IMPERV.
IMPERV.
AREA (SF)
11,501
30,898
0
100%
100%
100%
TOTALS 42,399 TOTAL= 42,399
PREVIOUSLY APPROVED PROPOSED
6,478 11,501
36,657
0
30,898
0
D:\PROJECTS\687-007\DWG\DRNG\687-007_IMPERVIOUS.DWG
BUCKING HORSE FILING TWO - MAJOR AMENDMENT
FORT COLLINS
COLORADO
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
DESCRIPTION
EXISTING VS. PROPOSED
IMPERVIOUS AREA
DRAWN BY
B. RUCH
DATE
JANUARY 23, 2019
PROJECT
838-024 SK-C1
SCALE DRAWING
1"=60'
( IN FEET )
0
1 INCH = 60 FEET
60 60
ASPHALT 0 100% 0
GRAVEL 0 40% 0