Drainage Report

es ACS Small scale Infiltration basins are listed as green technology for quantity in Tablé-S<2>witty'preamices Luc treatment. Quantity without exfiltration EXISTING Permitted DETENTION | OVERLAND | TOTAL (CFS) (CFS) (CFS) (CFS) (CFS) 2YR 1.79 90 0.9 74 83 10 YR 4.35 3.05 87 1.34 2.21 100 YR 10.09 8.07 4.35 2.65 7.0 Water Quality Small scale infiltration basins are listed as green technology for water quality when provided with pre- treatment. Basin 3 has a pre-treatment of a Cascade separator which provides 50% removal and the small-scale infiltration basin in series with it provides a total suspended solid removal of 90% Groundwater Recharge Groundwater recharge is achieved through the sand bottom in the small-scale infiltration basins. The 2 year storm volume routed to the basin is recharged. A spreadsheet showing the total compliance to the standard for groundwater recharge is included on page 14 Test pit G1 &G2 was excavated to a depth of 15 and 16 ft with no evidence of groundwater. The surface grade of this test pit is 538.0 making the bottom of the excavation 522.0. The basin bottom is set at elevation 528 making any groundwater in this area in excess of 6 ft below the bottom of the basin. Small-scale Infiltration basins with pre-treatment are listed as a green technology solution for groundwater recharge in table 5-2. Separate routing of the 2 year storm with exfiltration is provided to allow calculation of the total recharge in the recharge spreadsheet. Detention Basin 4 Area Tc Computations The Existing Area of Basin 4 contributing area is 96981 sf of Woods in good condition. The initial 100 LF is sheet flow with a slope of .5% in woods with light underbrush. The next segment is shallow concentrated flow 90 If with a slope of 4% through woods with light underbrush. There is no discernable channel in the field along this path that would change the categorization of the flow type. Tc = 15.9 min. Proposed Tc - Sheet Flow 100 LF @5.2% grass cover Tc= 6.4 min Shallow concentrated flow 100 If @ 3% Tc=.6 min, grass cover Pipe Flow 309 If of 15 inch pipe @ 2.61% N=0.01 Tc1 min Total Tc= 8 min Un-detained Area associated with Basin 4. Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com