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� � <br />/ /I � ' � / �'� <br />Auguat 3, 1988 <br />NELSON DISTRIBUTING COMPANY: HIGHLAND STREET SITE PLAN <br />STORM MATER DETENTION AND RUNOFF CALCULATIONS <br />Prepered by DOML Fnginesr: <br />16770 NE 79th Street, Suite 202 <br />Redmond, WA. 98052-4436 c206) A69-2670 <br />1. <br />2. <br />3. <br />4. <br />ON-SITE DET6NTION REGUIREMENTS: <br />.1 Dr�inagQ area: 200' X avg. 130'= 26.000 SF <br />= 0. 60 Ac. <br />.2 De�ign Storm Criteria: u�e "Combined gever, <br />outeide dorntovn; thereior pru-developm�nt <br />is 10 y��r sEorm; po�t-development is 10 <br />ye�r storw. <br />ALLOMABLE RfiL6ASE RATE: <br />OK' <br />D�C <br />.1 Exittinq ground slope per topo survey is 1.3X <br />.2 Exislinq ground cover is compact�d bare earth <br />and qravel. <br />.3 P��k r�t• o£ .unoii (irom Table 4) ior slopes <br />up to 2X = 0.72 CFS/AC. OK <br />DETENTION STORAGE REOUIRED: <br />.1 Site de�iqn yi�lds 0.34 AC impervious and 0.26 AC <br />unahanqed •arth/qravel. <br />.2 Storsqe t��rth/gravel�: 0.26 X N/A = 0.00 CFS D� <br />.4` <br />.3 Storaq� fimp�rvioue): 0.34 X 97 CFS/AC = 33 CFi <br />CONCLUSION: <br />.1 Required detention 19 almoot negliqible, and can be <br />aeeommodated within the on-site 9torm piping <br />syatem. <br />4. RUNOFF CALCULATIONS: <br />1 Rational iormula calculations: <br />A = 0.60 Acr=s <br />