Laserfiche WebLink
Technical Information Report July 2015 <br /> Everett Public Storage <br /> 4.0 Stormwater Control Plan <br /> This project proposes to construct a self-storage building with parking and utility improvements as <br /> shown on Figure 3. New and revised parking stalls are proposed to be constructed at existing grade <br /> with minor cuts and fills. The revised parking areas have been designed to maintain the existing <br /> drainage pattern, with stormwater sheet flowing towards the northeast away from the proposed <br /> building and towards the proposed wet/detention vault. <br /> To the greatest extent possible, surface runoff from the revised parking area and the entire roof area <br /> will be directed to the proposed detention vault. The controlled flows from the proposed detention <br /> vaults will be discharged to the existing drainage system as shown on Figure 3. As shown in Section <br /> 4.3, this downstream system has adequate conveyance capacity from the flow control structure to <br /> the existing detention tank. <br /> Stormwater flow and water quality control for the proposed project will be provided by an <br /> underground, combined detention / wet vault. As briefly noted above, runoff from the site will be <br /> directed to the proposed detention vault prior to discharging to an existing catch basin. With the <br /> proposed detention facilities, the overall downstream flows from the site will be reduced and will not <br /> impact the downstream storm drainage system. <br /> The current site plan has been provided by PM Design Group, Inc. (Architect). (See Figure 3). As <br /> noted in the Minimum Requirements, any new and replaced impervious surfaces are subject to <br /> providing flow control. The following is a summary of the design parameters and required detention <br /> volumes: <br /> • Total disturbed area: Approximately 2.5 acre <br /> • Pre-developed (assumed forested): 100% pervious area <br /> • Developed impervious area = 2.13 Ac. (85% impervious) <br /> • Developed pervious area = 0.37 Ac. (landscape areas) <br /> • Required flow control detention volume = 42,695 cf (0.98 acre feet) <br /> • Required water quality treatment volume = 0.22 acre feet <br /> • Proposed size of the detention vault is: 40'x156'x10.7' <br /> Design 100-Year storage volume = 1.08 acre feet <br /> • Design 25-Year water surface = 426.92 <br /> • Design 100-Year water surface = 427.57 <br /> 14114 Everett Storage TIR Revised 0715.doe 12 <br />