Drainage Report

BGO) Basin 2-5 Tc me Basin 2-5 collects runoff from the roof of building A. The Tc was computed with i . Sheet Flow 100 LF @ 1% on roof Te = 1 min Anderson Consutting Servioes LLC Pipe Flow 920 If of 12 inch pipe @ 4.1% N=0.01 Tc3 min Total Tc= 4.5 min Basin 2-6 Tc Basin 2-6 collects water from the roof and patio of building C. The Tc was computed with the following factors. Sheet Flow 100 If on roof s=1%, Tc= 1.5 min Shallow concentrated flow 40 LF @ 1% Te =.3 min Pipe flow 1622 LF s=3.7 % n= 0.01, 12 inch pipe tc= 4.8 min Total Tc = 6.6 min Un-detained Area associated with Basin 2. These are small areas at the perimeter of the drainage area that have minimal distance to travel before exiting the area of analysis. The longest path is Sheet flow 36 If @ 16% over grass Tc=4 min Detention basins 2-1 though 2-6 collects water from the east of drainage area 1 that drains to the Canoe Brook Tributary. The existing conditions have been modeled with a coverage as wood is good condition as required by the standards with NOAA type D rainfall curves. This area previously designed as one large scale infiltration basin has been redesigned to be 6 small scale infiltration basins with distinct drainage areas smaller than the 2.5-acre limit as required by the definition of a small scale infiltration basin. The table below outlines the results of the routing for this area without exfiltration. Small scale Infiltration basins are listed as green technology for quality, quantity and recharge in Table 5-2 EXISTING | Permitted | OL 2-1 2-2 2-3 2-4 2-5 2-6 TOTAL 2yr 5.69 2.85 91 0.4 11 15 11 19 18 1.69 10 yr_| 13.90 9.73 1.98 44 61 75 62 64 68 5.72 100 32.35 25.88 4.26 2.50 2.02 2.26 2.06 1.16 1.27 16.53 yr Water Quality Water quality in drainage area 2 is provided with a pre-treatment cascade separator prior to flowing into the small-scale infiltration basins. Table 5-1 lists small-scale infiltration basins as green technology for water quality, quantity, and groundwater recharge. Total removal from the separator and small scale infiltration basin is 90% 6 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com