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<br />I <br /> <br />I <br /> <br />I <br /> <br />B. QUALITY <br />OF RUNOFF <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />The purity or quality of the stormwater will <br />decrease. This will be due to sediment, oils, <br />and other foreign materials which will likely be- <br />come a part of the runoff. <br /> <br />The American Society of Civil Engineers has estab- <br />lished the following criteria for storm water <br />runoff from various land uses. <br /> <br /> QUALITY PARAMETERS <br /> IMPEAVI. BOO lBS! N lBS! P leSI PO, lBSI <br /> OUSNESS ACRE! ACREI ACRE! ACRE! ERO SION TEMPERATURE <br />LAND USE (OEGREEI YEAR YEAR YEAR YEAR CHANGE <br />NATURAL ~ <br />FORESTS lOW SMAll .89 .089 .3 lON V/// <br />(GRASSlANOSI '/. <br />AGRICUl TURE 2.<. .92. HIGH <br />tFARMS) lOW 2' 3.E3 POTE NTlAL SMAll <br />FEEOlOTS HIGH VARYING 'NITH ANI~.'':''L TY~E, HIGH <br /> DENSITY & MANAGEME.NT PnACTICES. POTE NTlAL SMALL <br />SINGLE FAMilY lOW. 5.9 .6 .2 .6 VARIES WITH <br />AESIOrr.NTlAL MEDIUM DEGREE OF COVER <br /> REMOVED AND <br />MULTI.FAMILY SURFACES HEATED. <br />RESIDENTIAL MEDIUM 14. 2.5 .57 2.1 o 0 <br /> IS to 15 >> <br />COMMERCIAL HIGH 43 2.4 \.3 3.9 <br />INDUSTRIAL VERY <br /> HIGH 23.4 3.3 .55 1.7 <br />RESOURCE VARIES WITH METHODOLOGY AND rAANAGEMENT <br />EXTRACTION PRACTICES <br />RECREATION VARIES WITH INTENSITY OF USE-EXTREMol Y <br /> SENSITIVE TO O'JERUSE. <br />URBAN 1\ ROAD I 30,000- I <br />CONS T RUCT ION 150,000 <br /> TONS!ACRE <br /> <br />Utilizing these criteria, for a commercial area, <br />(impervious) of 3.96 acres, and developed grassland <br />(pervious assumed 80% of single family residential) <br />of 2.49 acres for the overall development, the pro- <br />jected values of the resulting pollutant are: <br /> <br />Nitrogen 10.69 #/year <br />Dissolved Phosporus 5.55 #/year <br /> <br />The Rice Creek Watershed District has adopted a <br />criteria which indicates that one acre of grassy <br />marshland will assimilate 20 #/acre/year of <br /> <br />V-4 <br /> <br />_J <br />