2870 24 Amending and Supplementing Chapter 25 Section 29 of the Township of West Orange Municipal Code Stormwater Mgmt RedLined 2

20 rates of stormwater leaving the site for the current and projected 2-, 10-, and 100-year storm events, as defined and determined pursuant to § 25-29.5c and 5d respectively, of this ordinance, and that the increased volume or change in timing of stormwater runoff will not increase flood damage at or downstream of the site. This analysis shall include the analysis of impacts of existing land uses and projected land uses assuming full development under existing zoning and land use ordinances in the drainage area; iii. Design stormwater management measures so that the post-construction peak runoff rates for the current and projected 2-, 10-, and 100-year storm events, as defined and determined in § 25-29.5c and 5d,respectively, of this ordinance, are 50, 75 and 80 percent, respectively, of the pre-construction peak runoff rates. The percentages apply only to the post-construction stormwater runoff that is attributable to the portion of the site on which the proposed development or project is to be constructed; or iv. In tidal flood hazard areas, stormwater runoff quantity analysis in accordance with § 25-29.4r2(i), (ii), and (iii) above is required unless the design engineer demonstrates through hydrologic and hydraulic analysis that the increased volume, change in timing, or increased rate of the stormwater runoff, or any combination of the three will not result in additional flood damage below the point of discharge of the major development. No analysis is required if the stormwater is discharged directly into any ocean, bay, inlet, or the reach of any watercourse between its confluence with an ocean, bay, or inlet and downstream of the first water control structure. 3. The stormwater runoff quantity standards shall be applied at the site’s boundary to each abutting lot, roadway, watercourse, or receiving storm sewer system. Section V. Calculation of Stormwater Runoff and Groundwater Recharge: A. Stormwater runoff shall be calculated in accordance with the following: 1. The design engineer shall calculate runoff using the following method: (a) The USDA Natural Resources Conservation Service (NRCS) methodology, including the NRCS Runoff Equation and Dimensionless Unit Hydrograph, as described in Chapters 7, 9, 10, 15 and 16 Part 630, Hydrology National Engineering Handbook, incorporated herein by reference as amended and supplemented. This methodology is

nless Unit Hydrograph, as described in Chapters 7, 9, 10, 15 and 16 Part 630, Hydrology National Engineering Handbook, incorporated herein by reference as amended and supplemented. This methodology is additionally described in Technical Release 55 - Urban Hydrology for Small Watersheds (TR-55), dated June 1986, incorporated herein by reference as amended and supplemented. Information regarding the methodology is available from the Natural Resources Conservation Service website at: https://directives.sc.egov.usda.gov/viewerFS.aspx?hid=21422 or at United States Department of Agriculture Natural Resources Conservation Service, New Jersey State Office. Deleted: Section 5(C) and (D), Deleted: Section 5(C) and (D), Deleted: Deleted: 2.i, ii and iii Deleted: one of Deleted: (b) The Rational Method for peak flow and the Modified Rational Method for hydrograph computations. The rational and modified rational methods are described in Appendix A-9 Modified Rational Method” in the Standards for Soil Erosion and Sediment Control in New Jersey, January 2014. This document is available from the State Soil Conservation Committee or any of the Soil Conservation Districts listed in N.J.A.C. 2:190-1.3(a)3. The location, address, and telephone number for each Soil Conservation District is available from the State Soil Conservation Committee, PO Box 330, Trenton, New Jersey 08625. The document is also available at :http://www.nj.gov/agriculture/divisions/anr/pdf/ 2014NJSoilErosionControlSt andardsComplete.pdf¶