Stormwater Report 1

Table 6 – Overall Peak Runoff Rates – Future Projected Rainfall Existing Site Existing Site Proposed Site Proposed Site Storm Event Peak Runoff Runoff Volume Peak Runoff Runoff Volume 2 Year 11.28 cfs 53,349 cf 11.12 cfs 52,402 cf 10 Year 18.49 cfs 88,329 cf 18.33 cfs 87,232 cf 100 Year 34.83 cfs 169,002 cf 34.70 cfs 167,752 cf WATER QUALITY Since the proposed development does not result in a net increase of ¼ of an acre or more of impervious surface, the water quality aspect of the Stormwater Management Rules is not required. GROUNDWATER RECHARGE The site is located within the Metropolitan Planning Area. No groundwater recharge is required for the site. A map from Geo Web showing the site within this planning area can be found in the appendix of this report. STORM SEWER COMPUTATIONS A storm sewer system has been designed to collect the runoff associated with the proposed parking areas, drive aisles, walkways, and lawn areas. The pipes are designed to carry the flows for the 25-year storm. The rational method was used to calculate runoff rates. Manning’s equation was used to determine the capacity of each system. Storm Sewer Computations are included in the appendix of this report. Also, Fig.-3 shows the drainage areas to each inlet. The entire site is mapped with soils considered Hydrologic Group D (See attached Appendix for Soil Map). For this analysis, all the drainage areas were assumed to have 0.99 as a Runoff Coefficient (C value), which is the most conservative value. CONCLUSION The proposed improvements meet all of the stormwater management regulations for both the Township of West Orange as well as the NJDEP. The stormwater quantity is satisfied through the use of non-structural strategies, specifically the reduction in impervious surfaces. The 7