Revised Stormwater Management Report

DocuSign Envelope ID: DB0533B0-B14B-449D-A0A8-3B9C3C0DF5D9 Methodology The drainage for the development area of the property is calculated for the existing and proposed conditions for each of the three Points of Analysis. The proposed analysis is broken down into the overall un-detained in the analysis area and the flow to each of the stormwater management systems. The existing conditions for the site are considered wooded in good conditions per NJDEP guidance documents. Discharge rates for the existing conditions under the 2, 10 and 100-year storm events are calculated with The Hydrocad drainage program and the SCS TR-20 method. Hydrographs for the proposed conditions for areas detained and un-detained are developed. Allowable discharge rates for the detention system are calculated and the proposed hydrograph is routed through a proposed detention system until the desired discharge rate is achieved for each storm. Discussion Water Quality Each Drainage basin uses green technology to achieve the require 80% suspended solid removal rate. Small-scale infiltration basins are paired with a pre-treatment separator to achieve 90% removal rate. Chaptrer 9.8 permits non-GI Approved MTD’s to be used as pre-treatment as noted on page 10. “ Pretreatment may consist of a forebay or an BMPs found in chapter 9 or 11”. Porous pavement systems remove 80% per the BMP manual. The large-scale basin utilizes a green technology approved MTD ( filterra) at its inlets to achieve the water quality requirement. 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 results of the stormwater analysis for existing and proposed discharge are provided in the summary tables for each point of analysis. Detailed Hydrocad output is also included in the appendix of this report. Point of Analysis 1 (POA#1) PA#1 is the area of the site that drains to the Canoe Brook in the western portion of the property. The stormwater management systems designed for this are Large Scale Basin #1, and porous pavement systems 5&6. POA#1 (Point of Analysis) Existing Conditions Tc Computations. This drainage area is in a forested cover with very light underbrush due to

is are Large Scale Basin #1, and porous pavement systems 5&6. POA#1 (Point of Analysis) Existing Conditions Tc Computations. This drainage area is in a forested cover with very light underbrush due to deer over browsing. path of the existing conditions Tc is shown on the Existing Conditions Drainage Area Map. The Tc (Time of Concentration) is calculated in the Hydrocad program with the factors shown on the map and is as follows. 3 The