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HomeMy WebLinkAboutFile Documents.1230 Snowbunny Ln.0116.2019 (39).ARBKEngineering 1_0001-2020-BCHO_1230 Snowbunny Page: 1 Author: pjm File Name: Valentine Residence Drainage Memo.pdf Impervious area of 1133sf x 1.23 (design storm runoff) = 1,394cf of storage. Is there a typo here? Valentine Residence Drainage Memo.pdf (3) Page: 3 Author: pjm File Name: Valentine Residence Drainage Memo.pdf This drywell detail does not meet COA URMP drywell standards. Chapter 8 requires a two chamber drywell if WQCV is being treated by this BMP. Page: 3 Author: pjm File Name: Valentine Residence Drainage Memo.pdf Provide a plan that calls out elevations of tie ins to the drywell, sump and rim elevations, etc. All pertinent information for asbuilt review. D SPRINGS 118 West Sixth St, Suite 200 | Glenwood Springs, CO 81601 | 970.945.1004 Page | 1 overall drainage patterns, the site slopes generally from southwest to northeast. Due to the he house, the drainage patterns have been split into two major catchments, east of the house ich is west of the house. Detention requirements are being handled by soil berms at the low east and west sides of the house. Water quality is being treated by a combination of avers, tree credits, and grass buffers. An existing drywell in the SW basin was being utilized ality treatment. This drywell was being fed by a trench drain at the bottom of the driveway at nterface. Additionally, a portion of the roof runoff in the SW basin is directed to the drywell. r investigation, the existing drywell was found to be inadequate and inoperable in its current kely that sediment build up and improper maintenance has led to its failure. The drywell has ed in the same location with a new precast concrete drywell with dimensions 10’ deep and 4’ se of a drywell has been recommended by HP Kumar based on a percolation test done at the ember 24, 2018. ed drywell possesses the ability to store runoff in excess of 125 cubic feet. Without a elease, the drywell must be sized for 1.5 times the WQCV and the entire storm runoff COA URMP. For this basin, the required WQCV is 21.8 cubic feet with a required drywell hly 33 cubic feet. Basin 6 has an impervious area of 1133 square feet contributing to the ultiplying this area by the one-hour storm duration requires the drywell to be 116 cubic feet of than the proposed drywell storage volume. The proposed drywell is oversized based on rywell size criteria set forth by the URMP. Considerations of the timeline of this project, ier to install a standard drywell rather than submit for a formal variance. This treatment does not include the gravel pack surrounding the exterior of the drywell. Impervious area of 1133sf x 1.23 (design storm runoff) = 1,394cf of storage. Is there a typo here? This drywell detail does not meet COA URMP drywell standards. Chapter 8 requires a two chamber drywell if WQCV is being treated by this BMP. Provide a plan that calls out elevations of tie ins to the drywell, sump and rim elevations, etc. All pertinent information for asbuilt review. The 1394 cubic feet needs to be divided by 12 - the storm intensity is in inches. This will give the 116 cubic feet that is mentioned in the report The runoff diverted to the drywell will be from the roof which should have no sediment. The drywell will not have two chambers for this reason. Screens for the gutters and downspouts will be required to remove large organic matter (leave/sticks) that could clog the drywell with extended use. Addendum plan shows rim elevation for drywell, sump, and inlet pipe inverts.