J_2024 05 09_West Orange Stormwater Management Plan

Stormwater Management Plan Revision 0 Site Conditions 3. The creation of one-quarter acre or more of “regulated motor vehicle surface” since March 2, 2021; or 4. A combination of 2 and 3 above that totals an area greater than one-quarter acre or more. This project will disturb 3.48 acres on site and will increase impervious surfacing by 0.76 acres. Within the new impervious area, 0.22 acres of regulated motor vehicle surfacing will be added. This site is defined as a major development as it exceeds the one-acre threshold and relates to specific design criteria as follows: GROUNDWATER RECHARGE – The project is located within a Metropolitan Planning Area (PA1) and is considered an Urban Redevelopment Area, therefore it is exempt from groundwater recharge requirements under N.J.A.C. 7:8-5.4(b)2. WATER QUALITY – As stated in N.J.A.C. 7:8-5.5, since the project increases regulated motor vehicle surface by less than 0.25 acres, the project does not need to satisfy NJDEP water quality requirements. WATER QUANTITY – The project was designed to meet N.J.A.C. 7:8-5.6(b)3 by demonstrating that post-construction peak runoff rates for the current and projected 2-, 10-, and 100-year storm events, as defined in N.J.A.C. 7:8-5.7(c) and (d), do not exceed 50%, 75% and 80% of the pre-construction peak runoff rates for the respective storm events. The pre-developed watersheds associated with the current topography have been delineated, as indicated on Exhibit A. The pre-developed watersheds are reflective of the post developed watersheds that are included in the March 2012 Stormwater Management Report, prepared by TRC Engineers, Inc (See Appendix E). The post-developed watersheds associated with this project’s station upgrades, has been presented on Exhibit B. 1.4 Soils According to the Web Soil Survey developed by the United States Department of Agriculture’s (USDA) Natural Resources Conservation Service, the soil groups present on site are URBONB, Urban land, Boonton substratum, and USBONB, Urban land, Boonton substratum – Boonton complex. URBONB is previously developed land with no recorded soil type, therefore Hydrologic Soil Group D was assumed for these areas. USBONB surrounds URBONB on the site, and is classified as soil type B. However, the assumption to analyze the USBONB areas as Hydrologic Soil Group D was confirmed appropriate by the subsurface investigation.

urrounds URBONB on the site, and is classified as soil type B. However, the assumption to analyze the USBONB areas as Hydrologic Soil Group D was confirmed appropriate by the subsurface investigation. Silty Clay and Clayey Silts were found below the gravel and fill sections, Public Service Electric & Gas Company 1-2 Burns & McDonnell