[Added 10-19-2006 by Ord. No. 2006-35; amended 12-18-2008 by Ord. No. 2008-41]
A. Standards for structural stormwater management measures are as follows:
(1) Structural stormwater management measures shall be designed to take into account the existing site conditions, including, for example, environmentally critical areas; wetlands; flood-prone areas; slopes; depth to seasonal high water table; soil type, permeability and texture; drainage area and drainage patterns; and the presence of solution-prone carbonate rocks (limestone).
(2) Structural stormwater management measures shall be designed to minimize maintenance, facilitate maintenance and repairs, and ensure proper functioning. Trash racks shall be installed at the intake to the outlet structure as appropriate, and shall have parallel bars with one-inch spacing between the bars to the elevation of the water quality design storm. For elevations higher than the water quality design storm, the parallel bars at the outlet structure shall be spaced no greater than 1/3 the width of the diameter of the orifice or 1/3 the width of the weir, with a minimum spacing between bars of one inch and a maximum spacing between bars of six inches. In addition, the design of trash racks must comply with the requirements of § 220-154B.
(3) Structural stormwater management measures shall be designed, constructed, and installed to be strong, durable, and corrosion resistant. Measures that are consistent with the relevant portions of the Residential Site Improvement Standards at N.J.A.C. 5:21-7.3, 5:21-7.4, and 5:21-7.5 shall be deemed to meet this requirement.
(4) At the intake to the outlet from the stormwater management basin, the orifice size shall be a minimum of 2 1/2 inches in diameter.
(5) Stormwater management basins shall be designed to meet the minimum safety standards for stormwater management basins at § 220-154.
B. Stormwater management measure guidelines are available in the New Jersey Stormwater Best Management Practices Manual. Other stormwater management measures may be utilized provided the design engineer demonstrates that the proposed measure and its design will accomplish the required water quantity, groundwater recharge and water quality design and performance standards established by § 220-150.
C. Manufactured treatment devices may be used to meet the requirements of § 220-150, provided the pollutant removal rates are verified by the New Jersey Corporation for Advanced Technology and certified by the Department.
D. Standards for stormwater collection systems.
(1) Velocities in closed conduits at design flow shall be at least two feet per second but not more than 10 feet per second.
(2) No pipe size in the storm drainage system shall be less than 15 inches in diameter.
(3) All discharge pipes shall terminate with a precast concrete flared end section or a cast-in-place concrete headwall with or without wingwalls as conditions dictate.
(4) The spacing of inlets shall be such that surface water shall not flow for more than 500 feet or the quantity of water is such that it causes ponding of water deeper than two inches at Type B and Type E inlets, whichever is the lesser distance. If, due to the slope of the approach prior to the inlet, 80% of the stormwater does not enter the inlet, decreased spacing and depth of water permissible shall be required. Sufficient inlets will be placed to eliminate any flow exceeding two cubic feet per second across any roadway intersection or pedestrian crosswalk.
(5) Dished gutters shall be permitted at any street intersection on rural and local streets and at the intersection of rural and local streets with minor collector streets and at the intersection of minor collector streets with major collector streets where the street of the lower classification is to be officially designated and signed as a stop street. In such cases, the dished gutter shall cross only the street of the lower classification. At the intersections of primary and secondary arterial streets and major collector streets, sufficient catch basins, at the discretion of the reviewing agency, shall be installed at each street intersection to avoid gutter overflow and at low points in the street grade, and dished gutters shall not be permitted.
(6) Manhole spacing shall increase with pipe size. The maximum spacing shall be 500 feet for 15 to 18 inches; 600 feet for 21 to 36 inches; and 700 feet for 42 inches and greater.
[Added 12-18-2008 by Ord. No. 2008-41]
A. Storm sewer.
(1) Materials used in the construction of storm sewers shall be constructed of reinforced concrete, ductile iron, corrugated aluminum or corrugated steel unless site and other conditions dictate otherwise. Reinforced converted pipe shall be used unless the applicant can demonstrate that the use of other materials will be more beneficial due to the proposed installation. Cost will not be a consideration in this analysis. Specifications referred to, such as American Standards Association, American Society for Testing and Materials, American Water Works Association, etc., should be the latest revision.
(2) Reinforced concrete pipe.
(a) Circular reinforced concrete pipe and fittings shall meet the requirements of ASTM C-76.
(b) Elliptical reinforced concrete pipe shall meet the requirements of ASTM C-507.
(c) Joint design and joint material for circular pipe shall conform to ASTM C-443.
(d) Joints for elliptical pipe shall be bell and spigot or tongue and groove, sealed with butyl, rubber tape or external sealing bands conforming to ASTM C-877.
(e) All pipe shall be Class III unless a stronger pipe (i.e., higher class) is indicated to be necessary.
(f) The minimum depth of cover over the concrete pipe shall be as designated by the American Concrete Pipe Association.
(3) Ductile iron pipe. Ductile iron pipe shall be centrifugally cast in metal or sand-lined molds to ANSI A21.51-1976 (AWWA C151-76). The joints shall conform to AWWA C111. Pipe shall be furnished with flanges where connections to flange fittings are required. Pipe should be Class 50 (minimum). The outside of the pipe should be coated with a uniform thickness of hot-applied coal tar coating and the inside lined cement in accordance with AWWA C104. Ductile iron pipe shall be installed with Class C ordinary bedding.
(4) Corrugated aluminum pipe. Within the public right-of-way and where severe topographic conditions or the desire to minimize the destruction of trees and vegetation exist, corrugated aluminum pipe, pipe arch or helical corrugated pipe may be used. The material shall comply with the Standard Specifications for Corrugated Aluminum Alloy Culvert and Under Drain AASHTO Designation M196 or the Standard Specification for Aluminum Alloy Helical Pipe AASHTO Designation M-211. The minimum thickness of the aluminum pipe to be used shall be:
(a) Less than twenty-four-inch diameter or equivalent, 0.075 inch (fourteen-gauge).
(b) Twenty-four-inch diameter and less than forty-eight-inch diameter or equivalent, 0.105 inch (twelve-gauge).
(c) Forty-eight-inch but less than seventy-two-inch diameter or equivalent, 0.135 inch (ten-gauge).
(d) Seventy-two-inch diameter or equivalent and larger, 0.164 inch (eight-gauge).
(5) Corrugated steel pipe. Corrugated steel pipe may be used in place of corrugated aluminum and shall meet the requirements of AASHTO Specification M36. Coupling bands and special sections shall also conform to AASHTO M-36. All corrugated steel pipe shall be bituminous coated in accordance with AASHTO M-19O, Type A minimum.
(6) Pipe bedding shall be provided as specified in Design and Construction of Sanitary and Storm Sewers, ASCE Manuals and Reports on Engineering Practice Number 37, prepared by A Joint Committee of the Society of Civil Engineers and the Water Pollution Control Federation, New York, 1969.
B. Inlets, catch basins and manholes.
(1) Inlets, catch basins and manholes shall be designed in accordance with State Highway Department Standard Plans and Specifications. Frames shall be Campbell Foundry Company Pattern Number 2541, 2548, with eight-inch curb face, and 3432, 3440, for Type E inlets, or approved equal. All grates are to be bicycle grates.
(2) Manholes and catch basins shall be precast concrete, brick or concrete block, coated with two coats of portland cement mortar.
(3) If precast manhole barrels and cones are used, they shall conform to ASTM Specification C-473 with round rubber gasketed joints, conforming to ASTM Specification C-923. Maximum absorption shall be 8% in accordance with ASTM Specification C-478, Method A.
(4) If precast manholes are utilized, the top riser section shall terminate less than one foot below the finished grade and the manhole cover shall be flush with the finished grade.
(5) Manhole frames and covers shall be of cast iron conforming to ASTM Specification A-48 Class 30 and be suitable for H-20 loading capacity. All manhole covers in rights-of-way or in remote areas shall be provided with a locking device. The letters "Year 19 ____" and the words "STORM SEWER" shall be cast integrally in the cover.
C. Principal outlet structures.
(1) Outlet structures should be designed to facilitate outlet operation and maintenance as the water level rises and to permit clearing either during or after a storm. Structural support members, steps, rungs or ladders should be provided to allow easy escape opportunities for a child or an adult without having these support members, ladders, etc., impede the clearing of trash from the outlet structure or the upward movement of trash as the water level rises.
(2) The use of thin metal plates for trash rack bars, hand-hold supports, sharp crested weirs or orifices are prohibited because of the potential for accidents. Wire mesh fabric is similarly prohibited due to its poor suitability for trash clearance.
(3) Any outlet protective facility should have lockable hinged connections providing adequate access to thoroughly clean the area enclosed by the structure and to facilitate removal of accumulated debris and sediment around the outlet structure.
(4) All outlet structures shall be structurally sound and shall be designed to withstand, without failure or permanent deformation, all structural loads, hydrostatic, dynamic or otherwise, which impact upon it during the design life of the installation. They shall be maintenance free to the maximum extent possible.
[Added 10-19-2006 by Ord. No. 2006-35; amended 12-18-2008 by Ord. No. 2008-41]
A. Technical guidance for stormwater management measures can be found in the documents listed at Subsection A(1) and (2) below, which are available from Maps and Publications, New Jersey Department of Environmental Protection, 428 East State Street, P.O. Box 420, Trenton, New Jersey 08625; telephone (609) 777-1038.
(1) Guidelines for stormwater management measures are contained in the New Jersey Stormwater Best Management Practices Manual, as amended. Information is provided on stormwater management measures such as bioretention systems, constructed stormwater wetlands, dry wells, extended detention basins, infiltration structures, manufactured treatment devices, pervious paving, sand filters, vegetative filter strips, and wet ponds.
(2) The New Jersey Department of Environmental Protection Stormwater Management Facilities Maintenance Manual, as amended.
B. Additional technical guidance for stormwater management measures can be obtained from the following:
(1) The Standards for Soil Erosion and Sediment Control in New Jersey, promulgated by the State Soil Conservation Committee and incorporated into N.J.A.C. 2:90. Copies of these standards may be obtained by contacting the State Soil Conservation Committee or any of the Soil Conservation Districts listed in N.J.A.C. 2:90-1.3(a)4. The location, address, and telephone number of each Soil Conservation District may be obtained from the State Soil Conservation Committee, P.O. Box 330, Trenton, New Jersey 08625; (609) 292-5540;
(2) The Rutgers Cooperative Extension Service, 732-932-9306; and
(3) The Soil Conservation Districts listed in N.J.A.C. 2:90-1.3(a)4. The location, address, and telephone number of each Soil Conservation District may be obtained from the State Soil Conservation Committee, P.O. Box 330, Trenton, New Jersey 08625; (609) 292-5540.
[Added 10-19-2006 by Ord. No. 2006-35; amended 12-18-2008 by Ord. No. 2008-41]
A. This section sets forth requirements to protect public safety through the proper design and operation of stormwater management basins. This section applies to any new stormwater management basin. The provisions of this section are not intended to preempt more stringent municipal or county safety requirements for new or existing stormwater management basins. Marlboro Township and Monmouth County stormwater management plans and ordinances may, pursuant to their authority, require existing stormwater management basins to be retrofitted to meet one or more of the safety standards in § 220-154B(1), (2) and (3) for trash racks, overflow grates, and escape provisions at outlet structures.
B. 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 basin to ensure proper functioning of the basin outlets in accordance with the following:
(a) The trash rack shall have parallel bars, with no greater than six-inch spacing between the bars.
(b) The trash rack shall be designed so as not to adversely affect the hydraulic performance of the outlet pipe or structure.
(c) 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 on the basis of the net area of opening through the rack.
(d) The trash rack 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.
(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:
(a) The overflow grate shall be secured to the outlet structure but removable for emergencies and maintenance.
(b) The overflow grate spacing shall be no less than two inches across the smallest dimension.
(c) 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) For purposes of this Subsection B(3), "escape provisions" means the permanent installation of ladders, steps, rungs, or other features that provide easily accessible means of egress from stormwater management basins. Stormwater management basins shall include escape provisions as follows:
(a) If a stormwater management basin has an outlet structure, escape provisions shall be incorporated in or on the structure. With the prior approval of the reviewing agency identified in § 220-154C, a freestanding outlet structure may be exempted from this requirement.
(b) Safety ledges shall be constructed on the slopes of all new stormwater management basins having a permanent pool of water deeper than 2 1/2 feet. Such safety ledges shall be comprised of two steps. Each step shall be four feet to six feet in width. One step shall be located approximately 2 1/2 feet below the permanent water surface, and the second step shall be located one foot to 1 1/2 feet above the permanent water surface. See § 220-154D for an illustration of safety ledges in a stormwater management basin.
(c) In new stormwater management basins, the maximum interior slope for an earthen dam, embankment, or berm shall not be steeper than three horizontal to one vertical.
C. Variance or exemption from safety standards. A variance or exemption from the safety standards for stormwater management basins may be granted only upon a written finding by the appropriate reviewing agency, the Township of Marlboro, the County of Monmouth or the Department that the variance or exemption will not constitute a threat to public safety.
D. Illustration of safety ledges in a new stormwater management basin.
[Added 10-19-2006 by Ord. No. 2006-35; amended 12-18-2008 by Ord. No. 2008-41]
A. Submission of site development stormwater plan.
(1) Whenever an applicant seeks municipal approval of a development subject to §§ 220-147 through 220-158, the applicant shall submit all of the required components of the checklist for the site development stormwater plan at Subsection C below as part of the submission of the applicant's application for subdivision or site plan approval.
(2) The applicant shall demonstrate that the project meets the standards set forth in §§ 220-147 through 220-158.
(3) The applicant shall submit 15 copies of the materials listed in the checklist for site development stormwater plans in accordance with Subsection C.
B. Site development stormwater plan approval. The applicant's site development project shall be reviewed as a part of the subdivision or site plan review process by the municipal board or official from which municipal approval is sought. That municipal board or official shall consult the engineer retained by the Planning and/or Zoning Board (as appropriate) to determine if all of the checklist requirements have been satisfied and to determine if the project meets the standards set forth in §§ 220-147 through 220-158.
C. Checklist requirements. The following information shall be required:
(1) Topographic base map. The Township 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 one inch equals 200 feet or greater, showing two-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 floodplains 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 man-made 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 environs. This description should 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.
(3) Project description and site plan(s): 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 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 of proposed changes in natural conditions may also be provided.
(4) Land use planning and source control plan. This plan shall provide a demonstration of how the goals and standards of §§ 220-149 through 220-152 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:
(a) Total area to be 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.
(b) 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.
(6) Calculations.
(a) Comprehensive hydrologic and hydraulic design calculations for the predevelopment and postdevelopment conditions for the design storms specified in § 220-150.
(b) When the proposed stormwater management control measures (e.g., infiltration basins) depend on the hydrologic properties of soils, then a soils report shall be submitted. The soils report shall be based on on-site boring logs or soil pit profiles. The number and location of required soil borings or soil pits shall be determined based on what is needed to determine the suitability and distribution of soils present at the location of the control measure.
(7) Maintenance and repair plan. The design and planning of the stormwater management facility shall meet the maintenance requirements of § 220-156.
(8) Waiver from submission requirements. The Township Engineer or, if applicable, Board Engineer in consultation with the Township Engineer, may waive submission of any of the requirements in Subsection C(1) through (6) when it can be demonstrated that the information requested is impossible to obtain or it would create a hardship on the applicant to obtain and its absence will not materially affect the review process.
