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HomeMy WebLinkAboutA - Z PARTY RENTAL - FDP - 11-99A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTC3) Offsite Sub -basin "A" is the Northwesterly half of the existing industrial building on Lots 1, 2, 3 and 4 of Riverside Subdivision, Seventh Filing. The Northwesterly half of the roof of the building drains to four down spouts on the Northwest side of the building. There also is an asphalt driveway between the building and the property line which also sheet flows onto this site. The Southwesterly 30.00 feet of the Union Pacific Railroad right-of-way drains into the Pitkin Outfall Channel undetained. This 30.00 foot strip has historically drained into the Channel and therefore the runoff was not calculated as it does not affect this site. The Pitkin Outfall Channel was designed by the City of Fort Collins in 1981. The proposed finish floor elevation is 1.00 foot higher than the spillway over the railroad which will mitigate the flooding potential on this site from the Pitkin Outfall Channel. EROSION CONTROL: The site is in the moderate rainfall erodibility zone and in the moderate wind erodibility zone. The erosion control measures will be to not disturb the Pitkin Outfall Channel at the rear of the lot and to place a silt fence along the Northeasterly property line and along the Southwesterly line of the Pitkin Outfall channel at the rear of the site. Also gravel base material will be placed on a part of the site to raise the effectiveness to the required level. Extended detention ponds for water quality will be constructed for both Basins II and III. The phasing of the construction will be, to first strip the site and then rough grade the site including building the pad for the structure. The two extended detention ponds will also be graded at that time but will not be functional until the walls on the Channel side of the ponds are constructed. Secondly the gravel base will be placed on the staging area. Thirdly the concrete foundation will be constructed. Then the asphalt parking area and the concrete slab and walks will be constructed. The last erosion control measure will be the landscaping. This phasing is shown on the Construction Sequence. The stormwater runoff calculations and the extended detention and erosion control calculations are included as a part of this report. Also the Grading, Drainage and Erosion Control Plan is enclosed as a part of this report. This drainage report and the design of the drainage system are in compliance with the City of Fort Collins Storm Drainage specifications and criteria. If you have any questions regarding this report, please call. Sincerely, (2 l' 5028 Richard A. Rutherford, P.E. & L.S. RAR/meh dy�. E �. STEWART&ASSOCIATES Consulting Engineers and Surveyors December 15, 1999 Mr. Basil Harridan Storm Water Utility City of Fort Collins ` P.O. Box 580 Fort Collins, CO 80522-0580 Dear Basil, The following is the storm drainage report for A-Z Party Rental which will be on Lots 5, 6, 7, 8, 9 & 10, Riverside Subdivision, Seventh Filing, City of Fort Collins, Colorado. The site contains 0.99 acres and is in the Spring Creek Major Drainage Basin. The site is bounded on the Southwest by Riverside Avenue, on the Northwest by the Pitkin Outfall Channel, on the Northeast by the Union Pacific Railroad and on the Southeast by an existing industrial building. The site slopes from front to rear (Southwest to Northeast) at an approximate grade of 1.6%. The ground cover is weeds and gravel. The owners are proposing to construct a commercial building with asphalt parking and loading areas. A dock high loading area is also included. The historic site is divided into two sub -basins. Historic Sub -basin I is the Northeasterly half of the Riverside Avenue asphalt and the existing sidewalk which drains Northwesterly to the existing pan which flows to the Pitkin Outfall Channel on the Northwest side of this site. Historic Sub -basin II is the lot and the land between the back of the existing sidewalk along Riverside Avenue and the front property line. Historic Sub -basin II drains Northeasterly to the existing Pitkin Outfall Channel at the rear of the lot. The developed site is divided into four sub -basins. Developed Sub -basin I is the Northeasterly half of Riverside Avenue to the back of the existing sidewalk. Developed Sub -basin I will drain, undetained, Northwesterly to the existing pan which flows to the Pitkin Outfall Channel. Developed Sub -basin II is the Southeasterly half of the proposed building and the parking and loading areas on the Southeasterly side of the proposed building. Developed Sub -basin II will drain Southeasterly to the proposed Extended Detention Pond A. Developed Sub -basin III is the Northwesterly half of the building and the land between the front of the building and the sidewalk. It also includes the land between the Northwest side of the building and the property line. Developed Sub -basin III drains in a proposed pan to Extended Detention Pond B. Developed Sub -basin IV is the existing Pitkin Outfall Channel at the rear of the site. 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 U) �1 a(id p, . =.. . en ..0 .:. VICINITY MAP SCALE: 1 "= 1000' INDEX 1 Vicinity Map 2-3 Text of Report 4-9 Storm Water Runoff Calculations 10 Drainage Table 11-13 Swale & Channel Capacity Calculations 14 Rip Rap Calculations 15-19 Erosion Control Calculations 20-26 Water Quality Calculations Pocket Grading,Plan and Drainage & Erosion Control Plan v FINAL DRAINAGE REPORT FOR A-Z PARTY RENTAL SPRING CREEK DRAINAGE BASIN PREPARED FOR A-Z PARTY RENTAL DECEMBER 15, 1999 PREPARED BY STEWART & ASSOCIATES, INC. 103 SOUTH MELDRUM STREET P.O. BOX 429 FORT COLLINS, CO 80521 TEL. 970-482-9331 FAX.970-482-9382