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PACE) <br /> An Engineering Services Company <br /> Matrix 4— Proposed Area bypassing Tank <br /> Existing Land Cover Modeled Land Cover Area (acres) <br /> Landscaping C, Pasture, Mod 0.08 <br /> Roof Roof Tops, Flat 0.05 <br /> HMA Paving Parking, Mod 0.33 <br /> Total 0.46 <br /> 7.4 Flow Control System <br /> The proposed detention system has been located towards the high side of the site (west) <br /> because of the limited available depth of the public system. The bioretention area was <br /> not used in the calculations for meeting flow control compliance because the site is <br /> underlain by low permeability soils and it is anticipated to have minimal effect on the <br /> design calculations for the detention system. Detailed WWHM 2012 calculations have <br /> been provided demonstrating the proposed detention system meets Public Works Policy <br /> 2-11 in Appendix E. A summary of the design/construction parameters is provided <br /> below in Matrix#5. <br /> Matrix#5— Detention Tank Parameters <br /> Detention Tank Diameter 2.5 ft <br /> Tank Type Circular <br /> Length 30 feet (Use 20.57 feet min. See below) <br /> Riser Diameter 12 in <br /> Riser Height 2.4 feet <br /> Bottom Orifice#1 Diameter 1.50" <br /> Bottom Orifice#1 Elevation 0 ft <br /> Orifice#2 Diameter 0.50 in <br /> Orifice#2 Elevation 1.67 ft <br /> The following Calculations have been used to reduce the detention pipe length by <br /> accounting for the detention volume included in the control structure manhole. <br /> Total Detention Volume Required: <br /> VREQ = irr2L = 3.1415(1.25 ft)2 30 ft = 148 cf <br /> Volume Provided within 60" Dia. Manhole: <br /> VMH = rcr2H = 3.1415(2.5 ft)2 2.4 ft = 47 cf <br /> Volume required in Tank: <br /> VTANK = VREQ — VMH = 148 cf — 47 cf = 101 cf <br /> Tank Length Required: <br /> 101 cf <br /> LREQ = rc1.252 = 20.57ft <br /> Starbucks Page 12 <br /> Broadway and 10th Store <br /> Drainage Report <br /> May 2014 <br />