Common use of Watershed Data Summary Clause in Contracts

Watershed Data Summary. The following table summarizes the watershed data used to determine peak flows and runoff volumes required to design wet detention basin #1. Summary Data Elements Subwatershed A Subwatershed B (off-site) Pre-develop Post-develop Pre-develop Post-develop Watershed Areas (in acres) (see attached map) 41 acres 41 acres 26 26 Average Watershed Slopes (%) 2-8% 2-8% 3-6% 3-6% Land Uses (% of each) (see attached map) 75 ac. cropland 15 ac. brush 10 ac. woodland 110 ac. ½ ac. lots 5ac. brush 5 ac. woodlands 50% cropland 50% 1 acre lots 50% cropland 50% 1 acre lots Runoff Curve Numbers 68 x 75ac.= 5100 30 x 25ac.= 750 Net 5850\100 ac. RCN = 59 70 x 110 ac.= 7700 10 x 10 ac.= 100 Net 7800\120ac RCN = 65 RCN = 68 (state standard) RCN = 70 Conveyance Systems Types Grass waterway 50% grass swale 50% storm sewer 100% bare channel 100% grass swale Summary of Average Conveyance System Data 8’ bottom/4:1 ss 2’ depth/3% grade 2’ depth swale/3% 30” r/c sewer/2% (see calcs.) 15’ (w) top 1’ (d) parabolic 2% grade 2’ deep standard road ditch 2% grade Time of Concentration (Tc) (see attached map & worksheets) 1.1 hrs. .97 hrs. .74 hrs. .65 hrs. 25% of 2-yr 24-hr post-dev runoff volume N/A 2.29 ac. ft. N/A .19 ac. ft. 1-year/24 hour Runoff Volume N/A (.2” x 60 ac.) 1.0 ac. ft. N/A (.34” x 10 ac.) .28 ac. ft. 2-yr./24 hour Peak Flow (see attached hydrographs) 11.2 cfs 14.3 cfs 5.1 cfs 3.2 cfs 10-yr./24 hour Peak Flow 21 cfs 32 cfs 18.4 cfs 11.3 cfs 100-yr./24 hour Peak Flow 78 cfs 91 cfs 53 cfs 21 cfs Exhibit D (continued)

Watershed Data Summary. The following table summarizes the watershed data used to determine peak flows and runoff volumes required to design wet detention basin #1. Summary Data Elements Subwatershed A Subwatershed B (off-site) Pre-develop Post-develop Pre-develop Post-develop Watershed Areas (in acres) (see attached map) 41 acres 41 acres 26 26 Average Watershed Slopes (%) 2-8% 2-8% 3-6% 3-6% Land Uses (% of each) (see attached map) 75 ac. cropland 15 ac. brush 10 ac. woodland 110 ac. ½ ac. lots 5ac. brush 5 ac. woodlands 50% cropland 50% 1 acre lots 50% cropland 50% 1 acre lots Runoff Curve Numbers 68 x 75ac.= 5100 30 x 25ac.= 750 Net 5850\100 ac. RCN = 59 70 x 110 ac.= 7700 10 x 10 ac.= 100 Net 7800\120ac RCN = 65 RCN = 68 (state standard) RCN = 70 Conveyance Systems Types Grass waterway 50% grass swale 50% storm sewer 100% bare channel 100% grass swale Summary of Average Conveyance System Data 8’ bottom/4:1 ss 2’ depth/3% grade 2’ depth swale/3% 30” r/c sewer/2% (see calcs.) 15’ (w) top 1’ (d) parabolic 2% grade 2’ deep standard road ditch 2% grade Time of Concentration (Tc) (see attached map & worksheets) 1.1 hrs. .97 hrs. .74 hrs. .65 hrs. 25% of 2-yr 24-hr post-dev runoff volume N/A 2.29 ac. ft. N/A .19 ac. ft. 1-year/24 hour Runoff Volume N/A (.2” x 60 ac.) 1.0 acyr. ft. N/A (.34” x 10 ac.) .28 ac. ft. 2-yr./24 /24 hour Peak Flow (see attached hydrographs) 2.3 cfs 5.1 cfs 1.9 cfs 2.9 cfs 2-yr./24 hour Peak Flow 11.2 cfs 14.3 cfs 5.1 cfs 3.2 cfs 10-yr./24 hour Peak Flow 21 cfs 32 cfs 18.4 cfs 11.3 cfs 100-yr./24 hour Peak Flow 78 cfs 91 cfs 53 cfs 21 cfs Exhibit D (continued)