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HomeMy WebLinkAboutK 2 INDUSTRIAL PARK LOT 1 JB EXCAVATION PDP - 51 91C - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTSTORM DRAINAGE AND EROSION CONTROL REPORT FOR LOT 1 OF THE K-2 INDUSTRIAL PARK 1012 NORTHEAST FRONTAGE ROAD LOCATED IN THE BOXELDER CREEK BASIN PREPARED FOR J.B. EXCAVATING PREPARED BY STEWART & ASSOCIATES 103 SOUTH MELDRUM STREET P.O. BOX 429 FORT COLLINS, CO 80522 TEL. 970-482-9331 FAX. 970-482-9382 APRIL 18, 2001 Table of Contents Pages 1 and 2 Cover letter and text of report 3 Vicinity map 4 Historic site calculations 5 Developed site calculations 6 City FIRM map 7 County FIRM map 8 Elevation Certificate 9 Erosion Control Escrow Pocket Site Plan Grading and Drainage Plan a STEWART86SSOCIATES ' Consulting Engineers and Surveyors April 18, 2001 Mr. Basil Hamdan ' Stormwater Utilities City of Fort Collins P.O. Box 580 I Fort Collins, CO 80522-0580 Dear Basil, ' RE: 1012 Northeast Frontage Road Lot 1, K-2 Industrial Park Mr. Jim Bath of J.B. Excavating has purchased this site and plans to move is excavation operation onto the site. The existing site consists of 2.48 acres which has two existing buildings with some concrete sidewalks and the remainder of the site is gravel surfaced. The zoning department is requiring the installation of some additional pavement on the parking area and on the driveway to the existing building. We propose to remove some of the gravel surfacing on the front portion of the site and replace it with landscaping and vegetation. Enough of the gravel surface will be replaced with vegetation to maintain a composite runoff factor for the site at slightly less than the historic runoff factor which now exists. The site is located in the Boxelder Creek Drainage Basin, and is in Flood Zone A4. There are no new buildings or additions to the existing buildings proposed. There have been some landscaping berms constructed in areas where the gravel surfacing was removed. AYRES Associates has made an analysis of the impact of these berms on the water surface in the flood plain area, and found that the berms will not cause a rise in the flood water surface elevation. The existing site and also the proposed developed site drains from the southeast corner to the northwest comer. The runoff is into the East borrow ditch of the I-25 frontage road. There is a low sump area in this borrow ditch and in the adjoining property to the East of the borrow ditch. This low sump area extends to the north from the Lot 1 site. Given a large enough rainfall, this sump area would fill up and overflow to the south. The depth in the sump at overflow would be about 5 feet. Because there is no outflow for the runoff from the Lot 1 site, we propose to provide enough new landscaping and vegetation on the site to more than offset the added runoff caused by installing the required paved parking area and driveway. James H. Stewart and Associates, Inc. 103 S. Meldrum Street • P.O. Box 429 • Ft. Collins, CO 80522 970/482-9331 • Fax 970/482-9382 We are not providing onsite detention because of the proposed decrease in runoff from the site, and a variance is requested for this deviation from the City Stormwater Criteria. Also there are no water quality measures provided on the site and a variance is requested for this. The offsite sump area will act as a water quality settling basin. There is an offsite flow onto the Lot 1 site. This offsite flow will come from the property to the east. This offsite flow will have no adverse affect on the Lot 1 site, and will remain the same as it has been historically. The proposed development on Lot 1 will not effect the offsite flow. Erosion control will be provided during the installation of the landscaping and seeding on the west portion of the lot. A silt fence will be installed along the west fence line before beginning to remove the existing gravel in the landscaped area. Calculations are included in this report which show the historic existing runoff coefficient and runoff quantities, and those are compared to the proposed developed site runoff coefficient and runoff quantities. Also included is a copy of the FIRM map for this area. The FERM map dated March 18, 1996 indicates the site to be in Larimer County, but the property was annexed into Fort Collins in 1997 so copies of both the County and City FIRM maps have been included. A copy of the Elevation Certificate for the Lot 1 site is also included in this report. A plan of the Lot 1 site showing the proposed development and drainage patterns is included in the pocket of this report. This report for storm drainage and erosion control was prepared in accordance with the City of Fort Collins Criteria. Sincerely, Phillip I Robinson, P.E. & L.S. 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