Laserfiche WebLink
Verizon Communications-Stormwater Site Plan Everett,WA <br /> The StormFilter Vault was sized using the SBUH flow converted to an equivalent WWHM <br /> flow, as presented below, along with the sizing recommendations from Contech. <br /> WWHM Sizing <br /> Per the 2005 DOE Manual, Figure 9.6b provides the required ratio to apply to the water <br /> quality treatment flow rate. That chart specifies that for 6-month, 24-hour precipitation <br /> of 1.12 inches, the ratio (k) to apply is 2.80. The chart is shown below and the calculation <br /> showing this factor applied to the water quality flow rate is also shown below. <br /> 1.8132 CFS/2.80 — 0.65 CFS <br /> 0.65 CFS x 7.48 Gallon x 60 Seconds = 292 GPM <br /> Seconds 1 CF 1 Minute <br /> With WWHM sizing, the 27"-tall Contech StormFilter cartridges have a treatment flow rate <br /> of 11.25 GPM. Therefore, based on WWHM sizing, the number of cartridges required is: <br /> 292 GPM/ 11.25 GPM/cartridge = 26 cartridges <br /> This calculation is confirmed with the Contech Stormwater Treatment System Calculations, <br /> shown below. Therefore, this project proposes to provide 26-27" cartridges installed <br /> within an 8'x16' StormFilter Vault. <br /> SBUH Peak/WWHM Off-Line 16-min WQ Flow Ratio vs <br /> 6-Month Precipitation for 0%to 100%impervious Areas <br /> R 7.0 <br /> a 6.0 <br /> i 5.0 <br /> (K) 4.0 <br /> Z• .r •- o.M1110 I. .+ <br /> 2.0 l <br /> 1.0 <br /> 0.0 <br /> 0.0 0.5 1.0r'f2 1.5 2.0 2.5 3.0 3.5 4.0 <br /> 6-month,24-hr precipitation(72%of 2-year),Inches <br /> Figure 9.6b-Ratio of SSUH Peak1WQ Flow <br /> PACLAND Job#50183001 Page 22 <br />