21 Stormwater Mgmt Report_082025

4.3 Water Quality Controls As stated in the NJDEP Stormwater Management Regulations, the stormwater runoff quality standards are applicable when the development proposes an increase of one-quarter acre (10,890 square-feet) or more of regulated motor vehicle surfaces. The proposed development of the site will result in 0.18 acres (7,999 square-feet) of new motor vehicle surfaces. However, based on the West Orange Township Ordinance 2918-25 mentioned above in Section 1, 80% of the total suspended solids (TSS) must be removed for the net increase in motor vehicle surface. In order to satisfy this requirement, a pervious pavement system is proposed to treat 0.27 AC (11,639 SF). Motor Vehicle Surface Areas on site: Existing Motor Vehicle Surface Area: 1.96 Acres Proposed Motor Vehicle Surface Area: 2.14 Acres Net Increase in Motor Vehicle Surface Area: 2.14 Acres – 1.96 Acres = 0.18 Acres Required: Net Increase in Motor Vehicle Surface Area – 80% TSS Removal Treatment required [80% (0.18 Acres)] / 2.14 Acres = 6.72% Proposed: [80% (0.27 Acres)] / 2.14 Acres = 10.09% 10.09% Weighted Proposed TSS Removal Rate > 6.72% Required TSS Removal Rate As calculated the proposed weighted TSS removal rate is greater than the required rate; the project, as designed, meets the water quality requirement for the proposed development. 4.3.1 Pervious Paving Systems Pervious paving materials have been proposed as part of the overall site design and stormwater management system to reduce the impervious surface on site, provide 80% TSS removal for motor vehicle surfaces, and reduce the flow of runoff. The pervious paving systems have been designed to have a maximum ratio of additional inflow area to the pavement surface area of less than 3:1, a maximum surface slope of 5%, a storage bed that fully contains the water quality design storm runoff volume, and to discharge the design storm within 72 hours of a rain event. ▪ Stormwater Management Report for Proposed Retail Store▪ 6 ▪ August 2025 ▪