7720 TIMBER HILL DR 2016-01-01 MF Import

- l: ING COUNTY, w' ASHINGTON, SURFACE WATER DESIGN MANUAL TAIILEJ.S?Q SCSIVESTERNWASHINGTON RUNOFFCURVENUMBERS SCS WESTERN WASHINGTON NUNOFF CURVE NUMBERS (PuWi;hed by SCS in 1982) RunoH curve numbers lor selected agricultural, suburban and urhan land use for Type tA rainfall distrihution, 2a•hour storm duration. CURVE NUMBERS BY HYDROLOGIC S GROUP LAND USE DESCRIPTION A B C D Cultivated land(t): winter contluion 86 91 45 95 Mountain open arezs: iow growing brush and g2sslands 74 82 89 92 Meadow or pasture: 65 76 85 89 Wood or lorest land: unCisturbed or older second growth <Z 6s 76 B1 Wood or lorest land: young second growth or brush 55 72 Bt 86 Orchard: with tover crop 8� BB 92 94 Open spaces, lawns, parks, golf wurses, cemeteries, landswping. good condition: gress cover on 75% or more of the area 68 80 � 90 fair cond'¢ion: g25s cover on 50'6 to 75°G ot [he area 77 85 � 92 Gravel roads and parking lots ]6 BS 89 dt Dirt roads and parking lots 72 82 87 89 Impervious surtaces, pavement, rcofs. elc. 9B 98 98 98 Open water bodies: lakes, we�lands, ponds, etc. 100 100 t00 Singfe FamllyResidential (Z) Dwelling Unit/Gross Acre 56 Impervious (9) 1.0 DU/GA t5 Separate curve number t.5 OU/GA 20 shall be selected 2.0 DU/GA 25 for penious anG 2.5 OU/GA �0 imperviaus portion �.0 DU/GA �4 of the site or basin J.5 DU/GA 38 0.0 DU/GA <2 4.5 DU/GA <& 5.0 DU/GA a8 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 5a 7.0 DU/GA 56 Pianned unit develapments. 96 impervious condominiums, apartments, must be computed Commercial business and industrial areas. (t) For a more detailed descrip�ion of agricultc:al land use curve numbers refer to National Engineering Hand600k, Section a, Hydrology. Chapter 9. August 1972. (2) Assumes roof and driveway runoH is directed into street/stortn system. (J) The remaining pervious arcas (lawn) are considered !o be in good condition for these curve num6ers. � 3.5.2-3 tl/9� �/2�{