1808 MERRILL CREEK PKY 2016-01-01 MF Import

SCS�YESTERNWAS111NGTON RUNOFECURVENUMQERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS In 1982) RunoH curve numbers for selected agricultural, suburban and urban land use for Type tA rainfall distribution, 24•hour storm duretion. — CURVE NUMBERS BY � HYDROLOGIC SOIL GROUP lAND USE DESCRIPTION A B C D Cultivated land(t): winter conditlon �' 91 � 95 Mountafn open areas: low growing brush and grasslands 74 82 89 92 Meadow or pasture: 65 7B 85 89 Wood or torest land: 's u bed r o de s o 4�' � 76 81 55 72 87 86 or orest a 94 rc . with cover crop Open spaces, lawns, parks, goll courses, cemeteries, landsca in . � go condition: grass cover on 75% or more of the area � � � � Ifair condition: grass cover on 50% l0 75% oi the area �� 85 90 9Z Gravel roads and parking lots � 76 BS 89 91 Dirt roads and parking lots 72 B2 87 89 m ervious su aces vement roo s etc. 98 . pen water bodies: lakes, wetlan s, pon s, elc. 100 100 100 t00 Single Family Residential (2) W Owelling Unit/Gross Acre �+ Impervious (3) . J 1.0 DU/GA 75 Separate curve number M 1.5 DU/GA 20 shall be selected W 2.0 DU/GA 25 for 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 � 4.5 DU/GA 46 � . W 5.0 DU/GA 48 � M 5.5 DU/GA 50 {�� 6.0 DU/GA `'2 � 6.5 DU/GA �4 7.0 DU/GA 56 = Planned uni[developments, °h impervious � Z condomtniums, apanments, must be compuled commercial business and W industrial areas. \ / (1) For a more detailed descripiion of agricultural land use curve numbers reter lo National Engineering � Handbook, Section 4, Hydrology, Chapter 9,August 1972. � (2) Assumes roof and driveway runotl is directed into street/storm system. (3) The remaining pervious areas Qawn) are considered to be in good condi�ion for these curve numbers. I ` V � �