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DRAINAGE STUDY Pham Residence) _ <br /> TMK (3) 7 — 5 — 022 : 161 <br /> Street Address: 75-197 Ala Onaona Street, Kailua-Kona, HI 96740 <br /> "Reference County of Hawaii Storm Drainage Standard (October 1970) <br /> *GIVEN: Intensity of 1-hr rainfall = 2.0 (in. /hr.) [Tm=10 yr.; see attachment 1] <br /> Pre-development Q• <br /> Not considered. <br /> Post-Development Q: <br /> Improved Area: 5,000 ft2 roof, parking and driveway area = 0.115 acre <br /> Runoff Coefficient = 0.95 <br /> Runoff Intensity = 5,2(in. /hr.) [1-hr rainfall = 2.0 inches] <br /> Length = 100 ft. ref: Storm Drainage Standard (plate 3, 4) <br /> Ground character = paved <br /> Percent slope = 1.0% (min) <br /> TC = 5.0 min. <br /> Qimproved = (0.95)(5.2)(0.115) = 0.568 (ft3/sec) <br /> Summary: Increase of 0.57 (ft3/sec) must be contained within project area. <br /> INSTALL: Seven (7) rock sumps as proposed by developer on plan. Rock <br /> Sumps shall be located so that development generated runoff is directed away <br /> from building foundation and towards each sump; Sumps shall dispose of all <br /> development generated runoff through means of subsurface infiltration. See <br /> attached for plan locations (NOTE: final location of sumps to be determined by <br /> General Building Contractor). Voids in sumps are encouraged (use large <br /> boulders) for effective drainage/percolation. <br /> The Engineer reserves the right to improve the drainage condition as necessary <br /> and/or warranted by County of Hawaii, Department of Public Works Engineer <br /> and/or Inspector. <br /> Date prepared <br /> This work was prepared by me or under my supervis�o}i and construction of this <br /> project will be under my observation. ���� <br /> PETER J.K. DAHLBERG, P.E. DRAINAGE STUDY ATTACHMENT <br /> PDAHLBERG@HAWA11.RR.C®M PRAM RESIDENCE 2 <br /> (808)895--6173 (3) 7 — 5 — 022 : 161 <br />