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HomeMy WebLinkAboutENGINES & ENERGY CONVERSION LAB - BDR - BDR120006 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTNonetheless, with the additional detention volume, the existing direct overland flows will be decreased. All stormwater routed to the west will be collected into a water quality grass swale and intercepted by an area inlet. The area inlet is sized to collect the additional 100-year flows created by site improvements within this area. The runoff is discharged through public stormwater infrastructure already in place and outfalls into the river at an existing location. The existing rooftops are proposed to be treated through the use of inlet snouts and bio-skirts. This will allow water quality improvement to the existing building as well. The subject property is located within the FEMA regulatory floodplain for the Cache la Poudre River. The designated 100-year floodplain boundary crosses the site at the northwestern -most corner of the site. No site improvements or construction activity are proposed in or near this area. Therefore, Chapter 10 of the City of Fort Collins Municipal Code does not apply. In summary the proposed EECL Expansion is not expected to have an adverse effect on surrounding properties or the Cache la Poudre River. The 100-year direct overland flow will be decreased through the use of storm sewer and detention facilities. Water quality will be achieved through the use of a water quality pond, grass -lined swales and buffers, and inlet snouts and bio-skirts. No site improvements or construction activities will occur in or near the delineated FEMA 100-year floodplain, and no additional stormwater outfalls or other disturbance will occur to the stream bank. Please do not hesitate to contact me if you have questions or require additional information. Sincerely, Cody Snowdon Project Engineer NORTHERN ENGINEERING Drainage Letter Report Date: July 18, 2012 ADDRESS: PHONE:970.221.4158 WEBSITE: 200 S. College Ave. Suite 10 www.northernengineering.com Fort Collins, CO 80524 FAX: 970.221.4159 Project: Engines and Energy Conversion Lab Expansion Fort Collins, Colorado Attn: Mr. Wes Lamarque City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 Dear Wes: Project No. 207-007 This letter serves to address the stormwater impacts of the proposed Engines and Energy Conversion Lab (EECL) Expansion at 430 North College Avenue. The EECL site is located in the northeast quarter of Section 12, Township 7 North, Range 69 West of the 6`h Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. More specifically, the project site is located on the east side of College Avenue, and is bordered to the north by the Cache la Poudre River, and to the south and southeast by Burlington Northern Railroad. The subject property currently consists of the main lab and two other outbuildings with associated drives and equipment. The only access to the property is located at the southwest corner of the site and wraps around the south of the main lab to a parking area located behind the building. The area in front of the lab is well landscaped with various trees and bluegrass. The areas to the north, south and east consist of a mixture of native and non-native vegetation and gravel. The existing site is graded to convey stormwater away from the existing building with the ultimate destination being the Poudre River. The area in front of the building routes stormwater through a low gradient swale within the front 'Historic Lawn' and discharges into the river at the northwest corner of the project. The south and southeast side of the building route stormwater overland to a low gradient swale running along the railroad and discharges into the river at the northeastern corner of the lot. The north and northeastern sides of the building route stormwater completely overland to the river along the northern property line. The proposed project will include a building addition and a front parking area. Removal of the two outbuildings and associated parking/drive aisles will occur to improve the regulated 200' river setback. With the removal of two existing buildings and existing parking areas, the increase in impervious area is minimal; however, stormwater improvements are proposed to ensure that direct overland flow to the river is not increased and that all stormwater is treated prior to leaving the site. The EECL Expansion is designed to maintain existing drainage patterns and discharge points into the river. All stormwater routed to the east will be collected in a water quality pond and discharged into the river through an existing 10" pipe. The proposed water quality pond has capacity to detain the 100-year detention volume. It should be noted that detention is not required due to the proximity to the river.