HomeMy WebLinkAboutMULBERRY AND LEMAY CROSSINGS, 2ND FILING, PORTION OF LOT SIX, HOME DEPOT - PDP - 36-96J - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENTThe proposed development falls within the original design parameters of the Final Drainage
Analysis by CLC Associates, Inc. All storm sewer ponds have been constructed with
previous development and are currently operational. The site also contains several water
quality enhancements that were approved in lieu of extended detention. The proposed
building exceeds the City requirement of is inches above the BFE by 6 inches
(approximately 2 feet higher than the FEMA Base Flood Elevation). Therefore, additional
analysis of the proposed Home Depot development is not required.
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Mulberry and Lemay\Dots\Reports\HD249- na-Drainage Compliance Letter.doc
Galloway, Romero & Associates
Design Engineering Planning
5350 DTC Parkway
Greenwood Village, CO 80111
(303) 770-8884
FAX: (303) 770-3636
November 25, 2003
RE: Final Planned Unit Development — Major Amendment
Mulberry and Lemay Crossings Final P.U.D. — Filing No. 2, Lot 2
The Home Depot - Drainage Compliance Letter
This letter certifies that the Major Amendment to Mulberry and Lemay Crossings Final
Planned Unit Development, Filing No. 2, Lot 2 for the proposed Home Depot building and
Future Retail building is in compliance with the original Final Drainage Analysis by CLC
Associates, Inc., approved 6/21/00.
In the original CLC report, the area that makes up Lots 2 and 6 was comprised of eight full
basins and three partial basins. The eight full basins included Basins B8, B9, B10, B6-1, Cl,
C1-3, C2-1 and C4-1. The three partial basins included Basins C1-1, C1-2 and C3-2. All of
these basins were designed with a 100-year runoff coefficient of 1.00. The composite 100-
year runoff coefficient for the proposed Home Depot, Future Retail and existing retail on
Lots 2 and 6 is 0.85. Therefore, the proposed development is well within the designed limits
of the Final Drainage Analysis.
The original report addressed water quality and included several enhancements to the design,
which are currently in place. Most notable, the site features two "constructed" wetlands,
which act to remove Total Suspended Solids (TSS). The ponds are also long and thin which
allows the runoff longer contact time with the landscaped surface and tends to increase travel
time of the runoff from one end to the other, further increasing the settlement of particles.
Wetlands also enhance the biological activity associated with the breakdown of various
constituents. These enhancements were installed and approved in lieu of extended detention
as noted on page 4 of CLC's report which states that "additional enhancements, such as
wetlands plantings, are intended to compensate for traditional water quality capture volume
not accommodated in the Pond Bottoms."
Erosion Control measures will be installed during Construction Activities to minimize
erosion due to wind and runoff. Erosion control plans and notes have been included in the
Major Amendment planning set. The Site will be permanently stabilized with paving, sod,
mulch or landscape shrubs or trees.
The first floor of the Home Depot and the Future Retail buildings were designed to elevation
4935, approximately 2 feet higher than the Base Flood Elevation (BFE) according to FEMA
maps. The BFE has been shown on the Grading Plan included in the planning submittal.