2610 W CASINO RD VERIZON 2025-07-25

Verizon Communications-Stormwater Site Plan Everett, WA Water Quality Despite the fact the site is currently developed, water quality is required to be provided for the new or replaced pollution generating surfaces. However, the proposed water quality facility has been sized to accommodate all the pollution generating and non-pollution generating surfaces. The areas used to calculate the size of the water quality facility are as shown in Table 5 below: Table 5 Water Quality Only areas affected by development included in calculations. Proposed SF AC Pervious 78,745 1.80 Impervious(PGIS& NPGIS) 318,504 7.32 TOTAL 397,249 9.12 To satisfy the project's water quality requirements, a pre-settling chamber and a Contech StormFilter Vault will be installed. A flow splitter will also be installed to allow higher flow events to bypass these structures. Basin Data j PCN Calc PTC Calc DCI-CN Calc DCI-TC Cale Compute Runoff for Design Event I Select Design Event: WQ •j Compute AMC for this Computation: Project AMC.2 AMC G AMC2 AMC3 Static Peak Rate: 1.8132 cfs Time to Peak: 480.00 min.(8.00 hrs) Hydrograph Vol: 28629.25 cf(0.6572 acft) ===>Computation is+1-99.9967%of theoretical for time step of 10.00 min Close I Apply SBUH methodology and StormShed software were used to calculate the site discharge and to size the proposed water quality facilities. Per the DOE Manual, the water quality flow rate is calculated from a rainfall that is 72% of the 2-year, 24-hour event. The rainfall for the 2-year, 24-hour event, per the City of Everett Stormwater Manual, is 1.55 inches. Therefore, the 6-month, 24-hour (water quality) event rainfall is 1.12 inches. The peak flow for the water quality event for the fully developed, 9.12 acre site is approximately 1.81 CFS and 28,629 CF of storage volume. PACLAND Job# 50183001 Page 21