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HomeMy WebLinkAboutPEC120036 PRELIMINARY DRAINAGE REPORT by Marcin Engineering_received 110812MARCIN ENGINEERING LLC _____________________________________________________________________________________ PO Box 1062, Avon Colorado 81620 (970) 748-0274 November 7, 2012 Tom Kassmel, PE Town of Vail Engineer 75 S. Frontage Road Vail, CO 81657 RE: Town of Vail Golf and Nordic Clubhouse Remodel Preliminary Drainage Memo Dear Tom: This letter is to describe the overall drainage concepts that the design team is proposing for the Vail Golf and Nordic Clubhouse Remodel Project. The following concepts are incorporated into our current grading plan and will be confirmed via a formal drainage report as the project progress through the Town approval process: 1. Drainage from the Mountain to the South of the Project Site a) The drainage from the mountainside south of the Project has historically flooded the parking lot for this site. The worst of this flooding has historically occurred during the spring snowmelt runoff. This runoff comes down from the mountainside, crosses underneath Sunburst Drive in twin culverts, runs between the fourth and fifth houses east of the Project parking lot, and then is currently caught by the golf course service road and runs down the service road to the Project parking lot. The intent of our project, is to let this water run underneath the service road by installing culverts under the service road These pipes are currently called out as twin 24” HDPE culverts on Sheet C4.1. MARCIN will confirm these pipe sizes with calculations in the formal Drainage Report. b) Once this water is piped under the service road east of the project parking lot, the intent is to run the water in a newly constructed drainage ditch around the project as depicted on Sheet C4.1. This drainage ditch will be sized in the Drainage Report, but is preliminarily sized as being two feet deep with 4H:1V side slopes and a four foot flat bottom. These slopes will provide the ability to easily mow the ditch while mowing the surrounding golf course. The ditch will have to cross under the golf cart path with culverts and is currently depicted as going underneath one of the proposed driving range nets off the northeast corner of the building. c) As the ditch crosses in front of the north side of the Project, the ditch will pick up stormwater from the parking lot piping system and then the ditch will run northwest across the driving range and flow into the pond north of the driving range tee box. We have the proposed flowline of the ditch at the pond set two feet above the pond water surface elevation to account for two feet of freeboard in the pond. _____________________________________________________________________________________ PO Box 1062, Avon Colorado 81620 (970) 748-0274 2. Drainage from the Project Parking Lot and Building Area a) Drainage from the parking lot will be directed to the center of the parking lot and will flow down a valley pan in the center of the parking lot at the natural grade of the parking lot (ranging from 0.9% to 3%). b) At the north of the parking lot, the water will flow into a 2’x3’ valley inlet and the flow down into the drainage swale described above (see 1.c above). c) Three other inlets will catch water from the paved cart area west of the building and will drain into the same pipe system flowing north to the driving range ditch. The northerly inlet will tentatively be a naturalized ‘bioswale’ with appropriate plants to help filter sediment and chemicals in run-off while allowing infiltration back into the ground. If a ‘bioswale’ is not possible due to site constraints then a Stormceptor Water Quality Control Chamber that will treat the stormwater prior to releasing it onto the golf course will be considered in lieu of a bioswale.. d) All piping described here will be sized accordingly in the formal Drainage Report to be prepared by MARCIN. e) All other water that is not caught by the parking lot drainage system (i.e. on the south, east and north side of the building) will be graded to drain into the ditch system described in Item 1 above. The above concepts are how Marcin Engineering proposes to safely pass the rainfall and snowmelt drainage events through the site. MARCIN is open to further ideas on how to optimize these solutions and looks forward to working with the Project Team and the Town of Vail towards Construction Documents and building a successful project. Sincerely, MARCIN ENGINEERING LLC Paul Anderson, PE