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Home My WebLink AboutARBOR PLAZA SOUNDTRACK CAR AUDIO INSTALL - PDP/FDP - 13-00 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTc" ` Erosion Control Design — The Sound Track Audio Install site lies within moderate rainfall and wind erodability zones per City of Fort Collins zone maps. Potential for erosion exists as construction commences and until paving and landscaping are completed. The site is required to meet a rainfall erosion - performance standard of 79 during construction, and a performance standard of 93 after construction. Because the site is less than 1 acre, wind erodability will not be addressed. Overlot grading will begin in May of 2000. Paving should be installed within 12 weeks of the overlot grading, and permanent landscaping should follow as soon as possible after paving is complete. Prior to construction silt fencing will be installed around the entire site. Basin B3 will drain to inlets interior to the site. These facilities will be installed within approximately 8 weeks. During construction straw bale dikes will protect these inlets, and the Stormceptor unit itself will be immediately functional to prevent sediment from entering the New Mercer Ditch box culvert. Landscaped areas will be protected with erosion mats once the building walls are erected. At completion of construction, the entire site will be hard -surfaces or landscaped. : Erosion Control Security — Temporary erosion control measures: Measure Unit t Unit Cost Total Silt fence LF 1600. 0.73 $1168 Erosion mat SY 985 1.11 $1181 _ Straw bale dike EA 2 90 180 Total $2529 • Security = $2529 x 1.5 = $3794 Conclusion — All design and computations have been completed in compliance with the City of Fort Collins storm drainage design criteria. The site does not substantially change existing drainage pattern. All site drainage will be directed to Mail Creek through existing and new storm sewers. Erosion control measures will protect the storm sewer system and Mail Creek from excessive water -born sediment. The project will also be scheduled to minimize the time bare ground is exposed to the elements. 3 Introduction This report is submitted as a Project Development Plan drainage and erosion control report for Ultimate Electronics, an unplatted parcel in Arbor Plaza, Fort Collins, Colorado. The parcel is 0.89 acres, of which 0.57 acres are undeveloped and 0.32 acres have been developed as surrounding curb, gutter and asphalt street. The site is bounded on the north by Amigos PUD, on the northeast by Soundtrack PUD, on the east by Fazoli's PUD, on the southeast by Ethan Allen PUD and on the west by South Mason Street. The majority of the site currently drains to an area drain on the east end of Fazoli's parking lot. The project proposes to collect runoff from a majority of the site, including a truck dock, and pass it through a Stormceptor manhole prior to discharging into the existing New Mercer Ditch concrete box culvert which runs through the site. The Ultimate Electronics site will develop the last 0.50-acre within an otherwise developed 1.23 acre basin. No detention is required on the site, due to its proximity to the New Mercer Ditch box culvert, but BMP's will address - stormwater quality. This consists of a proprietary manhole that will treat low flow events by separation of oils and sediment, while allowing high flow events to bypass into the New Mercer Ditch box culvert. Prior to entering the Stormceptor manhole, flows will travel over a turf area, removing a portion of the sediment. Historic Off -Site Drainage — There is currently no off -site drainage. Proposed Off -Site Drainage — There is no proposed off -site drainage. Historic On -Site Drainage - The majority of the site currently drains to Area Drain 2, on the east end of Fazoli's parking lot. A minority of the site drains to Curb Inlet 3 in South Mason Street adjacent to the site. Proposed On -Site Drainage — Installation of landscaping will cause a net decrease in the discharge into Curb Inlet 3. Likewise, proposed grading of the site will cause a net decrease in the discharge into Area Drain 2. Truck dock runoff and a majority of the developed storm runoff from the proposed development of 0.50 acres will be collected in area drains and directed through a Stormceptor manhole in the parking lot and discharged into the adjacent New Mercer Ditch box culvert. Drainage Design Criteria — Drainage criteria are based on the City of Fort Collins Storm Drainage Design Criteria, and calculations use the rational method. Detention Storage — The developer requests a variance from the required on - site detention. As infill development on a small parcel, the entire site has been used. However the flows are being treated with 2 BMP's to insure the quality of the water leaving the site. Best Management Practice — Development requires implementation of a BMP to treat low flow storm runoff from the site. The site has a particular need to treat the runoff from the depressed truck dock. Because the elevation of the truck dock drain prevents use of a landscaped surface for collection and sedimentation, it is proposed to use the proprietary product "Stormceptor". This is a prefabricated manhole having a collection chamber beneath the inverts of the pipes. A weir within the manhole directs low flows into the sedimentation chamber, which is also configured to provide a space for oils to collect. Higher flows overtop the internal weir, passing through to the storm drain outlet, which is the New Mercer Box Culvert on the site. Configuration of the manhole allows flows up to 0.63 cfs to pass through the chamber. Flows in access of this will begin to bypass the chamber. The recommended "Stormceptor" size for this site provides sediment capacity of 115 c.f. and oil capacity of 240 gal. These elements are pumped separately from access through the manhole lid. The developer or current operator of the site will be responsible for pumping the manhole as needed. The size specified is estimated to need pumping approximately once a year, but this schedule could vary depending on maintenance of the site. Additionally, the area drain to the Stormceptor will be located in a turf area, allowing some filtering of sediment load prior to entering the Stormceptor. 2 TABLE OF CONTENTS Page No. INTRODUCTION ............................................. HISTORIC OFF -SITE DRAINAGE ........................ PROPOSED OFF -SITE DRAINAGE ....................... HISTORIC ON -SITE DRAINAGE ......................... PROPOSED ON -SITE DRAINAGE ........................ DRAINAGE DESIGN CRITERIA ........................... DETENTION STORAGE ..................................... BEST MANAGAMENT PRACTICE ........................ EROSION CONTROL ......................................... . CONCLUSION................................................. APPENDIX — DRAINAGE CALCULATIONS EROSION CONTROL CALCULATIONS 1. 1. I. 2. 3. ij Final Drainage and Erosion Control Report Arbor Plaza Sound Track Car Audio Install December 11, 2000 Prepared for: Ultimate Electronics Prepared by: EDAW Inc. 240 East Mountain Avenue Fort Collins, CO 80524 (970) 484-6073 . Job No. 9F062 4 ' EDAW INC P ' F 240 EAST MOUNTAIN AVENUE December 11, 2000 i FORT COLLINS COLORADO " Mr. Basil Hamdan ' 80524 City of Fort Collins i Stormwater Utility 700 Wood Street TEL 970 484 6073 Fort Collins, CO 80524 FAX 970 484 8518 - Re: Final Drainage and Erosion Control Report for www.edaw.cem Arbor Plaza Sound Track Car Audio Install UNITED STATES EUROPE AUSTRALIA 6 ASIA V Dear Basil: We are pleased to submit for your review and approval this Final Drainage and Erosion Control Report for Arbor Plaza Sound Track Car Audio Install. We appreciate your consideration in reviewing this submittal. Please call if you have questions. Best Regards, ALLY, Kay Force Design Engineer cc: Encl. DESIGN, PLANNING AND ENVIRONMENTS WORLDWIDE