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11 Basin Information and Lag Time Computation 11 <br />Project Title: Parkdale Granite Quarry <br />Catchment ID: C <br />1. Catchment Hydrologic Data <br />Catchment ID = C <br />Area = 50.65 <br />Area = 0.0791 <br />Percent Imperviousness = 5.00 <br />NRCS Soil Type = D <br />II. Analysis of Flow Time (Time of Concentration Tc) for a Catchment <br />Using SCS Lag Equation (1975) <br />Developed for small (<2000 acres) watersheds <br />Equation assumes Tc = 1.67*Basin Lag <br />Tc = 100L°'8[(1000/CN)-9]17 / (1900So.) <br />Avg. slope for longest watercourse S = 15.8 <br />SCS Curve No. CN = 84 <br />Length of Water Course L = 2,714 <br />Tc = 16 <br />Acres <br />Square Miles <br />A, B, C, or D <br />Land use assumed to be Posture/Range in FAIR condition <br />feet <br />minutes