9909 2ND AVE W 2018-08-01 - Laserfiche WebLink

DETENTION VAULT 1 Dimensions Bottom Area Volume Sediment Chamber Size-Modeled 56'x 4'x 6' 224 sf 1,344 cf Detention Chamber Size-Modeled 42'x 24'x 4.5' 1,008 sf 4,536 cf Detention Chamber Size with 30% 56'x 24'x 4.5' 1,344 sf 6,048 cf Correction Factor-Designed The second proposed detention vault(Vault 2) will be located between units 13, 14& 15 under the proposed driveway. It will have a control structure designed to release peak runoff at pre- developed runoff rates of 50%of the 2-year and 100%of the 10-year and 100-year storm events. The control structure will be located outside the vault and be accessible from the proposed driveway. Vault 2 is composed of two chambers. Stormwater entering the vault goes into the first chamber sized to provide sediment treatment for the stormwater. From the first chamber the water exits the vault and is filtered by two Contech Catchbasin Stormfilters. Stormwater then enters the second vault chamber from the filter and is detained until it can be released at pre-developed rates. The storm filter will provide water treatment for Basin 2 and the site frontage only. The table below summarizes the design for Vault 2. DETENTION VAULT 2 Dimensions Bottom Area Volume Sediment Chamber Size-Modeled 82'x 4'x 4.6' 328 sf 1,509 cf Detention Chamber Size-Modeled 54'x 24'x 1,296 sf 6,804 cf 5.25' Detention Chamber Size with 30% 72'x 24'x 1,688 sf 9,072 cf Correction Factor- Designed 5.25' After exiting the vault control structures, stormwater will flow east to level spreaders bordering the onsite wetland. Water quality-Water quality treatment will be provided for a 6-month peak flow rate calculated as 74% of a 2-yr design storm event. Released runoff will flow through a Contech Stormfilter. The Stormfilter cartridge vault configuration will provide water quality treatment for the runoff in accordance with DOE requirements and will remove approximately 80% of the pollutants in the runoff from the drainage area. 6