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HomeMy WebLinkAboutMULBERRY AND LEMAY CROSSINGS, 2ND FILING, HOME DEPOT - MAJOR AMENDMENT - 36-96I/L - 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 18 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. Sincerely, Galloway, Ro ro & As ociates i 4 r Jon . Andresen Jr., \\FILESRVR\clients\HomeDepot\HD149-HD249-HD449 - HD Store #NW0066 - Store Development - Ft. Collins, CO - NEC Mulberry and Lemay\Dots\Reports\HD249-jna-Drainage Compliance Letter.doc Galloway, Romero & Associates Design Engineering Planning 5350 OTC 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 Cl-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.