HomeMy WebLinkAboutSite Certifications - 05/22/2020
May 19, 2020
Dan Mogen, EI, CFM
Development Review Engineer
City of Fort Collins
281 North College Ave
Fort Collins, CO 80524
RE: 424 Pine St. - Teaching Tree Exterior Improvements - Drainage Certification Letter
Mr. Mogen,
This letter is provided to verify the as-constructed site conditions for the exterior improvements at Teaching
Tree (424 Pine St) meet the requirements of the approved drainage plans. As-built spot elevations were
provided to me on 5/1/2020 from Saunders Heath and are marked on the attached plan. I conducted a
physical inspection of project site on May 5, 2020.
Based upon my review of the as-constructed elevations and my observations during the site visit, the
following items are noted:
1) The northern playground sidewalk “loop” is constructed at approx. 0.2’ higher than shown on the
approved plans. However, the drainage concept is not altered in a significant manner and drainage
is expected to be adequate.
2) The exterior concrete on the north-east side of the building at the existing AC condenser units was
not removed and replaced as proposed. The new sidewalk has been lowered to achieve drainage of
this area.
3) Seeding of disturbed areas outside of the fence is yet to be completed. I understand that Saunders
Heath has discussed this with the City and the landscape contractor will be seeding these areas.
4) The concrete headwall for the underdrain has not yet been installed. Contractor is scheduled to
install this during some other minor remaining concrete work to be completed at the project site.
5) As shown in the attached record drawing, the smaller “toddler” playground was converted to rubber
surface and the segment of underdrain was removed. This change occurred to reduce the amount
of earthwork required in areas of contaminated soils. We had previously discussed this at a meeting
with you on 8/5/2019 and no concerns with this modification were noted.
I conclude, based upon the attached information and personal site visit, that the site has been constructed
in satisfactory compliance with the drainage plans. The variations noted are not expected to negatively
impact the overall drainage intent of the site. The completed drainage certification and record drawings are
attached.
Please let me know if you have any questions or comments.
Respectfully Submitted,
PROFESSIONAL ENGINEERING CONSULTANTS, PA
Scott M. Turnbull, P.E.
05/19/2020
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 = 2,300 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =77 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 = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =46 sq ft
D) Actual Flat Surface Area AActual =1310 sq ft
E) Area at Design Depth (Top Surface Area)ATop =1310 sq ft
F) Rain Garden Total Volume VT=1,310 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
Engineered wood mulch playground surface (12" min depth).
No vegetation will be planted in filter 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 =ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
S Turnbull
PEC
May 19, 2020
Teaching Tree - AS-BUILT
424 Pine St Fort Collins CO
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07 - AS BUILT.xlsm, RG 5/19/2020, 9:38 AM
As-Built Conditions
represent removal of one
mulched play surface
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?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
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)
S Turnbull
PEC
May 19, 2020
Teaching Tree - AS-BUILT
424 Pine St Fort Collins CO
Rain garden concept applied to wood mulch playground areas. No outlet orrifice restriction to be provided per City direction. Impervious liner to be provided
in order to separate contaminated soils and groundwater from the underdrain systems.
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 - AS BUILT.xlsm, RG 5/19/2020, 9:38 AM
No vegetation/ plantings
Drain pipe daylights at
headwall w/ conc apron for
energy dissipation
No vegetation/ plantings
11278
4965.74
MWEL
11278
4965.74
MWEL
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Job Number:
Drawn By:
Project Issue Date:
970 | 672 | 6570
Fort Collins, CO 80525
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2 9/6/2019 ASI #5
REPLACED MULCH PLAY SURFACE
WITH POURED RUBBER SURFACE.
REMOVED UNDERDRAIN SEGMENT
TO THIS PLAY AREA.
5/11/2020 RECORD DRAWING
MATCHED EXISTING ELEVATIONS
RECORD DRAWING
NOTE: ALL ELEVATIONS MARKED WITH RED
TEXT CORRESPOND TO AS-BUILT
CONDITIONS BASED ON INFORMATION
PROVIDED BY THE CONTRACTOR 5/1/2020.
AS-BUILT CONDITIONS WERE NOT
MEASURED FOR ALL SPOT ELEVATIONS
SHOWN ON THE DESIGN.
INSTALLED PIPE IS 4" DIA.