Drainage Report

The geotechnical investigation found that significant area of the site proposed AY limitations to groundwater recharge in the form of shallow bedrock. Approximately? acres 6fttie-Site where proposed building B and C are located has bedrock located on average 4 ft below grade. This site specific limiting factor make the estimation groundwater recharge of existing conditions with the standard analysis grossly conservative. _ It also limits the project's ability to provide small scale green infrastructure in proximity to the area of disturbance. The proposed design with green technology solutions at the lower section of the site adjacent to the wetlands area then mimics the natural conditions of the site by taking stormwater that does not recharge into bedrock and recharging it into the deeper running permeable soils at the base of the hill. We believe that modeling the natural conditions as proposed meets the intent of the regulations. Additional soil tests we recently performed in the proposed basin areas to verify the soil conditions in the exact location of the stormwater management systems. These tests were found to be very similar to the adjacent ones previously performed. The older tests are within the standards to locate the seasonal high groundwater table and the new testing provided more permeability data within the basin area. Water Quality The project proposes 8 small scale infiltration basins which take the discharge for the proposed developed area of the property. These small scale infiltration basins will have mechanical pretreatment in the form of a Cascade separator which removed 50% of the suspended solid prior to discharge to the small scale infiltration basin. The combination of the two devices in series results in the removal of 90% of the suspended solids from the stormwater. The project also proposes one large scale infiltration basin which has filterra stormwater treatment devices before each inlet in a vehicle surface area. Filterra is approved as green technology for the removal of 80% of the suspended solids from stormwater Two porous pavement systems are proposed to provide a green technology solution for water quality quantity and recharge making all aspects of the stormwater system green technology. Water Quantity The stormwater system proposed has been designed to reduce the discharge from the site for the 2-, 10- and

ty and recharge making all aspects of the stormwater system green technology. Water Quantity The stormwater system proposed has been designed to reduce the discharge from the site for the 2-, 10- and 100-year storms as required by the stormwater regulations. Each of the drainage/detention areas has been designed to control stormwater to below its current discharge rate. The routing of the basins do not include exfiltration in the quantity analysis. The results of the stormwater analysis for existing and proposed discharge are provided in the tables below. Detailed Hydrocad output is also included in this report. Detention Basin 1 Area Tc Computations. The existing conditions of the drainage area that is routed to Basin 1 a forested area with very light underbrush due to deer over browsing. The path of the existing conditions Tc is shown on the Existing Conditions Drainage Area Map. The Tc is calculated in the Hydrocad program with the factors shown on the map and is as follows. 3 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com