9606 19TH AVE SE McDONALDS 2018-01-02 MF Import

KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.5.2B SCS 1VESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve in for selected agricultural, suburban and urban land use for Type to rainfall distribution, 24-hour storm duration. LAND USE DESCRIPTION open areas: or pasture: vvooa or Iore5t renu. Wood or forest land: Orchard: Open spaces, lawns, parks, landscaping. good condition: fair condition: Dirt roads and parking lots condition low growing brush and undisturbed or older second growth young second growth or brush with cover crop courses, cemeteries, grass cover on 75% or more of the area grass cover on 50% to 75% of the area Impervious surfaces, pavement, roofs, etc. ponds. etc. Open water bodies: lakes, wetlands, p Dwelling Unit/Gross Acre % impervious (3) 1.0 DU/GA 20 1.5 DU/GA 25 25 2.0 DU/GA 30 2.5 DU/GA 34 3.0 DU/GA 38 3.5 DU/GA 42 a 4.0 DU/GA 46 4.5 DU/GA 48 5.0 DU/GA ! 50 5.5 DU/GA 52 6.0 DU/GA 54 6.5 DU/GA 56 56 7.o DU/GA Planned unit developments. % impervious must be computed condominiums, apartments, commercial business and industrial areas. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP A B µI D 86 91 94 95 74 82 89 92 65 78 Bus 89 IFR(6PK`J 42 64 76 81 55 72 81 86 81 88 a2 94 77 85 90 92 76 65 89 91 72 82 87 89 98 98 98 ml r. G�J. 100 100 100 100 Separate curve number shall be selected for pervious and impervious portion of the site or basin (1) For a more detailed description of aSricultural land use curve numbers refer to National tngineenny Handhook, Section 4, Hydrology, Chapter 9. August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. & 3.5.2-3 11/92 I