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SOUNDVIEW TECHNOLOGY CENTER EVERETT, WA <br /> ESC ANALYSIS AND DESIGN <br /> Trapping Sediment <br /> Structural control measures will be used to reduce erosion and retain sediment on the construction site. <br /> The control measures will be selected to fit specific site and seasonal conditions. <br /> The following structural items will be used to control erosion and sedimentation processes: <br /> • Stabilized construction entrances <br /> • Filter fabric fences <br /> • Catch Basin Inlet Sediment Protection <br /> • Proper Cover measures <br /> • Temporary swales <br /> • Sediment pond/vault <br /> • Rock check dam <br /> Weekly inspection of the erosion control measures will be required during construction. Any sediment <br /> buildup shall be removed and disposed of off-site. <br /> Vehicle tracking of mud off-site shall be avoided. Installation of a stabilized construction entrance will be <br /> installed at a location to enter the site. The entrances are a minimum requirement and may be <br /> supplemented if tracking of mud onto public streets becomes excessive. In the event that mud is tracked <br /> off site, it shall be swept up and disposed of off-site on a daily basis. Depending on the amount of <br /> tracked mud, a vehicle road sweeper may be required. <br /> Because vegetative cover is the most important form of erosion control, construction practices must adhere <br /> to stringent cover requirements. More specifically, the contractor will not be allowed to leave soils open for <br /> more than 14 days and, in some cases, immediate seeding will be required season dependent. <br /> Phase 1 —TESC Ponds <br /> A temporary sediment ponds are proposed during construction to collect, contain and control release of <br /> any site runoff during construction. The ponds will be constructed prior to construction of the permanent <br /> vaults. Three ponds are proposed, one for each basin (A, B, and Q. The sediment structure is sized <br /> according to design specifications per Section BMPC241:Temporary Sediment Pond of the DOE Manual. <br /> Using WWHM2012, the 10-year, flow based on the developed conditions. Below are the results: <br /> TESC Pond— Basin A <br /> Tributary Area: 6.13 acres (to vault#4) <br /> Flow Frequency <br /> Flow(cfs) 0701 <br /> 2 Year = 1.2369 <br /> 5 Year = 1. 6630 <br /> 10 Year = 1.9667 <br /> 25 Year = 2.3758 <br /> 50 Year = 2. 6995 <br /> 100 Year = 3.0398 <br /> 10-year flowrate: 1.97 CFS <br /> The required surface area was calculated using the following equation: <br /> SA = 2 x Q 7o/0.00096 <br /> SEPTEMBER 23, 2022 STORMWATER DRAINAGE REPORT PAGE 39 <br />