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® 0 • <br />Red Barn <br />Engineering Inc. <br />www. redbarn-engi ne eri ng. com <br />6610 NE 181st ST STE 2, KENMORE, WA 98028 <br />PHONE: (425) 419-4979 <br />TECHNICAL MEMORANDUM <br />DATE: 9/5/2018 <br />TO: Arnie Roshak <br />FROM: Rebekah Weston, PE <br />SUBJECT: 1020 N Broadway, PW 1804-004 SEWER CALCULATIONS PER ORANGE BOOK <br />The sewer calculations for the 1020 North Broadway project are based on 140 single -occupancy units <br />that assumes a building population of 200 people total (including retail, no restaurant). The peak flow <br />for the sanitary sewer is calculated as follows: <br />1) Population = 200 people <br />2) Average Daily Use = 100 gpd/capita (per Table G2-2 in the Orange Book) <br />3) Retail Space (non -Restaurant) = 1,910 SF <br />4) Average Daily Use = 200-300 gpd/1,000 SF <br />5) Peaking Factor = 4.1 (see below) <br />Qpeak_residential = Flow rate (gpm) x Population x Peaking Factor <br />(SF) <br />Qpeak_comm.ercial = Flow rate (gpm) x 1,000 Retail Space ce x Peaking Factor <br />SF <br />6) Peak Flow for the project results in the following: <br />100 <br />Qpeak_residential = 24 X 36 x 200 x 4.1 = 95 gpm <br />300 1,910 SF <br />Qpeak_commercial = 24 x 36 x 1,000 SF x 4.1 = 3 gpm <br />The combined peak flow is approximately 100 gpm. <br />1I� <br />37712018 <br />