Laserfiche WebLink
engineering p c <br /> Table 2—Eastern TDA Developed Areas <br /> ` x-:2 "£- <br /> r �1"OpOS$CNC.O�dlt1o11S <br /> Eastern TD�Q Developed Ara g quareFeet Acres <br /> New PGIS 671 0.02 <br /> Replaced PGIS 799 0.02 <br /> New Non PGIS 10,810 0.25 <br /> Replaced Non PGIS 4,219 0.10 <br /> Removed Impervious 7,482 0.17 <br /> Net New Impervious Surface 3,999 0.09 <br /> (Total New—Removed) <br /> Table 3—Western TDA Developed Areas <br /> r gc Erl;y " ?n .la;77 ., CO,p Sfjf�„�'rOC,- <br /> ste5 <br /> ; Wern TDA"DeveA <br /> loped rea SF y Aeres <br /> • <br /> New PGIS 1,610 0.04 <br /> Replaced PGIS 0 0.00 <br /> New Non PGIS 3,166 0.07 <br /> Replaced Non PGIS 0 0.00 <br /> Removed Impervious 474 0.01 <br /> Net New Impervious Surface <br /> (Total New—Removed) 4,302 0.10 <br /> In accordance with minimum requirement#5,the project will apply on-site stormwater <br /> management BMPs including BMP 12.20 Soil Amendments, Quality and Depth by amending on- <br /> site disturbed soils in place;BMP 12:50 Downspout Dispersion Systems through the use of splash <br /> blocks to disperse downspouts where feasible; and BMP 12.70 Sheet Flow Dispersion along the <br /> proposed loading driveway. Where sheet flow dispersion is infeasible area drains will collect <br /> runoff and convey the flows to the storm drain system. <br /> E. Stormwater Treatment Plan <br /> The project has less than 5,000 SF of new and replaced pollution generating impervious surface in <br /> both threshold discharge areas,therefore treatment facilities are not required per Table 2.1 of <br /> section 2.2.6 of the Everett Stormwater Management Manual. <br /> F. Conveyance Analysis <br /> It was determined that the most capacity constraining pipe is the existing 6-inch concrete pipe <br /> connecting the southern drainage network to the existing storm manhole. The 100-year peak runoff <br /> rate from the tributary basin was determined using WWHM4 with 15-minute a timestep. The full <br /> flow capacity of the pipe was determined using Manning's equation.The 100-year peak flow to the <br /> pipe was 0.58 cfs and the pipe full capacity was 0.61 cfs, demonstrating that the pipe has adequate <br /> LPD Engineering, PLIC Page 9 Mukilteo School District Teaching and Learning Center <br /> Stormwater Site Plan,July 22, 2014; Revised August 25, 2014 <br />