1920 MERRILL CREEK PKY 2018-01-01 MF Import

( � SCS VVESTERN WASHINGTON RUNOFF CURVE NUMBERS 1 SCS WESTEFiN WASHINGTON RUNOFF CURVE NUMBERS (Publ(shed by SCS in 1982) I RunoH curve numbers for selected agricultura�, suburban and urban�and use for Type tA rainfall dlstribulion, 24•hour storm durallon. CURVE NUMBERS BY i � HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D � Cultivated land(1): winter condillon 86 91 94 95 Mountain open areds: low growing brush and grasstands 74 82 89 92 I Meadow or pasture: 65 7B �S 09 Wood or lorest land: 's d r o der seco 42 64 76 87 Wo or orest a : 55 72 81 86 � rchard: with cover crop 94 Open spaces, lawns, parks, golf courses, cemeteries, landsca in . I go condition: grass cover on 75% or more o(lhe area 60 80 86 90 lair condil(on: grass cover on 50% to 75°h o(Ihe area 77 85 90 92 I Grevel roads and parking lots 76 BS 89 91 Oirt roads and p�rking lots 72 82 H7 89 m ervious su aces vemeni roo s e c. 98 pen water bodies: lakes, wetlan s, po s, etc. t00 100 100 100 Single Family Residential (2) � Dwelling Unit/Gross Acre °h Impervious (3) J 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected � 2.0 DU/GA 25 lor pervious and � 2.5 DU/GA 30 impervious portion ` 3.0 DU/GA 34 of the site or basin r � 3.5 DU/GA 38 • 4.0 DU/GA � 42 � I 4.5 DU/GA 46 W 5.0 DU/GA 4B 5.5 DU/GA 50 � 6.0 DU/GA 52 � I 6.5 DU/GA b4 ' 7.0 DU/GA 56 � Planned unit deveiopments, % impervious Z I condominiums, apanments, must be computed commercial business and � industrial areas. I (�) For a more detailed description ol agricutlural land use curve numbers refer to National Engineering � Handbook, Section 4, Hydrdogy, Chapter 9,August 1972. (2) Assumes roof and driveway runoH is direcled into street/storm system � (3) The remaining pervious areas (lawn) are considered to be in good condition lor these curve numbers. � � I �