1808 MERRILL CREEK PKY 2016-01-01 MF Import

KING COUNTY, WASF' VGTON, SURFACE WATE 7ESIGN MANUqL TABLE JS.2a SCS�VESTERN WASHINGTON RUNOFF CURVE NUMDERS . '� ,. SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (PuWished by SCS in 1982) RunoM curve numbers lor selected agdcultural, suburban and urban land use br Type 1 A ralniall dist�ibulion, 24•hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated larx!(t): winter condRion 86 91 94 95 Mountain open areas: low growing brush and gresslands 74 82 69 92 Meadow or pasture: 65 7g g, gg Wood or taes[IarW: undisturbed or older second growth 42 64 76 et Woad a�aen la^d: young second growth or brush 55 72 8� 86 ��b� with cover aop 8� � 92 94 Open apacea,lawns, partcs, gdf courses, cemetedes, Iandscaping. . good condftlon: grass cover on 75% or more of the area 68 80 8(t gp (air condklon: grass cover on 50% to 75%of the area 77 85 90 92 � Gravel roads and parking lots 76 &5 89 91 Dirt roads and pa�Icing lots • 72 82 87 89 , ��•� � Impervious suAaces, pavement, roofs, etc. 98 98 98 98 � _, Open water bodles: lakes, weqar�ds, ponds, etc. 100 100 100 700 , Single Famtly Residential (2) _, Dwellfng UnR/Gross Acre % Impervfous (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 2.0 DU/CaA 25 to pervious aM 2.5 DU/GA 30 Impervious portion 3.0 OU/GA 34 of the sfte or basin 3.5 OU/GA . 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 OU/GA 54 ' 7.0 DU/GA 56 Planned unh developments, % impervioua condominiums, apartments, must be computed "' commerclal business and Industriai areas. (t) For a more detaiied description of agricultural land use curve numbers refer to NaHonal Engineering ��+ Handbook, Section 4, Hydrdogy, Chapter 9, August 1972. (2) Assumes roof erxf driveway runoH is directed into street/storm system. (3) The remalning pervlous areas Qawn) are considered to be in good condition for these curve numbers. ,� � 3.5.2-3 t1/92