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HomeMy WebLinkAbout20a Stormwater Basin Calcs. 8-14-2020 Town Pump 6 Lounge Stormwater Calculations Retention Basin Calculation of Required Volume for Storm Retention Pond (Reference: Bozeman Stormwater Master Plan - 1982) Design Rainfall Freq. 10 year(see page III -5 of master plan) OF coefficient a 0.64 OF coefficient b OF coefficient n 0.65 Post-development Calculations C Areas (ft): Landscape 1,431 0.20 Impervious 29,934 0.90 Total: 31,365 Retention Pond Calculations: Q = CIA C = 0.87 (post-development) I = 0.41 in/hr(10-yr, 2-hr storm) A= 0.72 acres Q = 0.25 cfs required retention storage(ft3)= 1,835 ft" Volume held between contours: Cumulative Contour Area (ft) Delta V(ft3) Volume (ft) 4697.75 20 4698.00 1,068 136 136 4698.50 1,328 599 735 4699.00 1,325 663 1,398 4699.50 1,960 821 2,220 0NTA&�'� Design storage at IS depth (ft3)= 2,220 s: CFIRIS • • - BUDESKIKI - 'J3 NO. 08 P ��w Ott` ,EtJg;�aC?~�: Town Pump 6 Lounge Stormwater Retention Basin Calculations