2918-25 STORMWATER final 4_1_25.doc.pdf

re than nine (9.0) square inches; ii. Where the municipality agrees that the standards would cause inadequate hydraulic performance that could not practicably be overcome by using additional or larger storm drain inlets; iii. Where flows from the water quality design storm as specified in N.J.A.C. 7:8 are conveyed through any device (e.g., end of pipe netting facility,

31 manufactured treatment device, or a catch basin hood) that is designed, at a minimum, to prevent delivery of all solid and floatable materials that could not pass through one of the following: a. A rectangular space four and five-eighths (4.625) inches long and one and one-half (1.5) inches wide (this option does not apply for outfall netting facilities); or b. A bar screen having a bar spacing of 0.5 inches. Note that these exemptions do not authorize any infringement of requirements in the Residential Site Improvement Standards for bicycle safe grates in new residential development (N.J.A.C. 5:21-4.18(b)2 and 7.4(b)1). iv. Where flows are conveyed through a trash rack that has parallel bars with one inch (1 inch) spacing between the bars, to the elevation of the Water Quality Design Storm as specified in N.J.A.C. 7:8; or v. Where the New Jersey Department of Environmental Protection determines, pursuant to the New Jersey Register of Historic Places Rules at N.J.A.C. 7:4- 7.2(c), that action to meet this standard is an undertaking that constitutes an encroachment or will damage or destroy the New Jersey Register listed historic property. § 25-29.8—Safety Standards for Stormwater Management Basins: A. This section sets forth requirements to protect public safety through the proper design and operation of stormwater management BMPs. This section applies to any new stormwater management BMP. B. The provisions of this section are not intended to preempt more stringent municipal or county safety requirements for new or existing stormwater management BMPs. Municipal and county stormwater management plans and ordinances may, pursuant to their authority, require existing stormwater management BMPs to be retrofitted to meet one or more of the safety standards in § 25-29.8C1, C2, and C3 for trash racks, overflow grates, and escape provisions at outlet structures. C. Requirements for Trash Racks, Overflow Grates and Escape Provisions 1. A trash rack is a device designed to catch trash and debris and prevent the clogging of outlet structures. Trash racks shall be installed at the intake to the outlet from the Stormwater management BMP to ensure proper functioning of the BMP outlets in accordance with the following: i. The trash rack shall have parallel bars, with no greater than six-inch spacing between the bars; ii. The trash rack shall be designed so as not to

the BMP outlets in accordance with the following: i. The trash rack shall have parallel bars, with no greater than six-inch spacing between the bars; ii. The trash rack shall be designed so as not to adversely affect the hydraulic performance of the outlet pipe or structure; iii. The average velocity of flow through a clean trash rack is not to exceed 2.5 feet per second under the full range of stage and discharge. Velocity is to be computed based on the net area of opening through the rack; and

32 iv. The trash rack shall be constructed of rigid, durable, and corrosion resistant material and designed to withstand a perpendicular live loading of 300 pounds per square foot. 2. An overflow grate is designed to prevent obstruction of the overflow structure. If an outlet structure has an overflow grate, such grate shall meet the following requirements: i. The overflow grate shall be secured to the outlet structure but removable for emergencies and maintenance. ii. The overflow grate spacing shall be no greater than two inches across the smallest dimension iii. The overflow grate shall be constructed and installed to be rigid, durable, and corrosion resistant, and shall be designed to withstand a perpendicular live loading of 300 pounds per square foot. 3. Stormwater management BMPs shall include escape provisions as follows: i. If a stormwater management BMP has an outlet structure, escape provisions shall be incorporated in or on the structure. Escape provisions include the installation of permanent ladders, steps, rungs, or other features that provide easily accessible means of egress from stormwater management BMPs. With the prior approval of the municipality pursuant to § 25-29.8C, a free-standing outlet structure may be exempted from this requirement; ii. Safety ledges shall be constructed on the slopes of all new stormwater management BMPs having a permanent pool of water deeper than two and one-half feet. Safety ledges shall be comprised of two steps. Each step shall be four to six feet in width. One step shall be located approximately two and one-half feet below the permanent water surface, and the second step shall be located one to one and one-half feet above the permanent water surface. See § 25-29.8E for an illustration of safety ledges in a stormwater management BMP; and iii. In new stormwater management BMPs, the maximum interior slope for an earthen dam, embankment, or berm shall not be steeper than three horizontals to one vertical. D. Variance or Exemption from Safety Standard A variance or exemption from the safety standards for stormwater management BMPs may be granted only upon a written finding by the municipality that the variance or exemption will not constitute a threat to public safety. E. Safety Ledge Illustration Elevation View –Basin Safety Ledge Configuration

33 § 25-29.9—Stormwater Management Requirement for Minor Development A. The stormwater runoff requirements applicable to Minor Developments are as follows: 1) For each square foot of increased impervious surface, six inches per square foot of stormwater shall be managed using green infrastructure practices set out in Table 7 below or such other measures as may be required by the municipal engineer of which the retention storm must be retained on site using green infrastructure. 2) All such development shall be subject to review by the municipal engineer to determine that all stormwater runoff created by the development is adequately controlled in accordance with the standards of this ordinance. 3) In such cases where it is determined that the outflow from the stormwater management system will impact an adjacent property, the outflow shall be directed to a storm sewer, swale, or other suitable stormwater runoff conveyance measure. 4) If the municipal engineer determines that the outflow from the stormwater management system may potentially damage an adjoining property and the out flow cannot be safely directed to a storm sewer, swale, or other suitable stormwater runoff conveyance measure, the stormwater runoff from the development shall be retained on-site at a rate of four inches of storage for each square foot of new impervious surface using green infrastructure practices or such other measures as may be required by the municipal engineer. 5) If the applicant cannot comply with § 25-29.9A above, the proposal should be redesigned or reduced in scope so that the stormwater management measures do not damage an adjoining property.

34 Table 7 Minor Development BMP Grass Swale Green Roof Pervious Paving System Small-Scale Bioretention Basin Small-Scale Infiltration Basin Small-Scale Sand Filter Vegetative Filter Strip Cistern Dry Well* (* The use of dry wells is allowed only where the other listed methods cannot feasibly meet the requirements of this section.) 6) Table 8 Provides presumptive rain garden sizes that can be installed to manage New Jersey’s Water Quality Design Storm on minor developments. Table 8 Rain Garden Table Drainage Area Rain Garden Size Clay Soil (soil amendments needed) Silty Soil Sandy Soil 500 ft2 200 ft2 100 ft2 75 ft2 750 ft2 350 ft2 150 ft2 112 ft2 1,000 ft2 400 ft2 200 ft2 149 ft2 1,500 ft2 600 ft2 300 ft2 224 ft2 2,000 ft2 800 ft2 400 ft2 299 ft2 (Source: Rain Garden Manual of New Jersey, Rutgers Water Resource Programs. Rain garden size based on New Jersey’s Water Quality Design Storm – 1.25 inches of rain over 2 hours) 7) The stormwater management feature shall be protected from future development by conservation easement, deed restriction, or other acceptable measures. 8) Waivers. A waiver from strict compliance with § 25-29.9 may be granted by the Township Engineer for those projects where an applicant has demonstrated the inability or impracticability of strictest compliance with the stormwater management requirements in that section. No waiver shall be granted if the runoff compliance is less than the 10-year rainfall event. 9) The use of a BMP is subject to soil suitability and approval of the Township Engineer.

35 § 25-29.10 -Requirements for a Site Development Stormwater Plan: Major Development A. Submission of Site Development Stormwater Plan 1. Whenever an applicant seeks municipal approval of a development subject to this ordinance, the applicant shall submit all the required components of the Checklist for the Site Development Stormwater Plan at § 25-29.10C below as part of the submission of the application for approval. 2. The applicant shall demonstrate that the project meets the standards set forth in this ordinance. 3. The applicant shall submit [specify number] copies of the materials listed in the checklist for site development stormwater plans in accordance with § 25-29.10C of this ordinance. B. Site Development Stormwater Plan Approval The applicant's Site Development project shall be reviewed as a part of the review process by the municipal board or official from which municipal approval is sought. That municipal board or official shall consult the municipality’s review engineer to determine if all the checklist requirements have been satisfied and to determine if the project meets the standards set forth in this ordinance. C. Submission of Site Development Stormwater Plan The following information shall be required: 1. Topographic Base Map The reviewing engineer may require upstream tributary drainage system information as necessary. It is recommended that the topographic base map of the site be submitted which extends a minimum of 200 feet beyond the limits of the proposed development, at a scale of 1"=200' or greater, showing 2-foot contour intervals. The map as appropriate may indicate the following: existing surface water drainage, shorelines, steep slopes, soils, erodible soils, perennial or intermittent streams that drain into or upstream of the Category One waters, wetlands and flood plains along with their appropriate buffer strips, marshlands and other wetlands, pervious or vegetative surfaces, existing man-made structures, roads, bearing and distances of property lines, and significant natural and manmade features not otherwise shown. 2. Environmental Site Analysis A written and graphic description of the natural and man-made features of the site and its surroundings shall be submitted. This description shall include a discussion of soil conditions, slopes, wetlands, waterways and vegetation on the site. Particular attention should be given

te and its surroundings shall be submitted. This description shall include a discussion of soil conditions, slopes, wetlands, waterways and vegetation on the site. Particular attention should be given to unique, unusual, or environmentally sensitive features and to those that provide particular opportunities or constraints for development. The map shall indicate the following: existing surface water drainage, shorelines, steep slopes, soils, erodible soils, springs, seeps, intermittent

36 or perennial streams, wetlands, and flood plains along with their appropriate buffer strips, marshlands and other wetlands, forests, and core forests, pervious or vegetative surfaces, existing man-made structures, roads, bearing and distances of property lines, and significant natural and manmade features not otherwise shown. 3. Project Description and Site Plans A map (or maps) at the scale of the topographical base map indicating the location of existing and proposed buildings roads, parking areas, utilities, structural facilities for stormwater management and sediment control, and other permanent structures. The map(s) shall also clearly show areas where alterations will occur in the natural terrain and cover, including lawns and other landscaping, and seasonal high groundwater elevations. A written description of the site plan and justification for proposed changes in natural conditions shall also be provided. 4. Land Use Planning and Source Control Plan This plan shall provide a demonstration of how the goals and standards of § 25- 29.3 through § 25-29.5 are being met. The focus of this plan shall be to describe how the site is being developed to meet the objective of controlling groundwater recharge, stormwater quality and stormwater quantity problems at the source by land management and source controls whenever possible. 5. Stormwater Management Facilities Map The following information, illustrated on a map of the same scale as the topographic base map, shall be included: i. Total area to be disturbed, paved or built upon, proposed surface contours, land area to be occupied by the stormwater management facilities and the type of vegetation thereon, and details of the proposed plan to control and dispose of stormwater. ii. Details of all stormwater management facility designs, during and after construction, including discharge provisions, discharge capacity for each outlet at different levels of detention and emergency spillway provisions with maximum discharge capacity of each spillway. iii. Location and results of all test pits, overlaid with the location of all BMPS. The SHWT, depth of mottling observed, and bottom elevation of the BMP shall be listed in a comprehensive chart. iv. Map of predevelopment and post development drainage areas v. Map demonstrating the contributory drainage area for each BMP. 6. Calculations i. Comprehensive hydrologic

ed in a comprehensive chart. iv. Map of predevelopment and post development drainage areas v. Map demonstrating the contributory drainage area for each BMP. 6. Calculations i. Comprehensive hydrologic and hydraulic design calculations for the pre- development and post-development conditions for the design storms specified in § 25-29.4 of this ordinance. ii. When the proposed stormwater management control measures depend on the hydrologic properties of soils or require certain separation from the