Standards for structural stormwater management measures are as follows:
Structural stormwater management measures shall be designed to factor into the design the existing site conditions which may cause the measure to fail, have an adverse effect on water quality or quantity, or cause harm or damage to persons or property, 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; existing or former mines; significant land filling; and the presence of solution-prone carbonate rocks (limestone) and related karst topography.
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 § 296-24.
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. The measures are to be sequenced in the site development process so that erosion control standards are met and so the measure is not compromised or impaired by construction runoff.
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.
Stormwater management basins shall be designed to meet the minimum safety standards for stormwater management basins at Article VIII.
Where tailwater will affect the hydraulic performance of a stormwater management measure, the design engineer shall include such effects in the measure's design.
Stormwater management measure guidelines are available in the New Jersey Stormwater Best Management Practices Manual and other documents as described in Article VI. Other stormwater management measures may be utilized, provided that the design engineer demonstrates to the satisfaction of the review agency that the proposed measure and its design will accomplish the required water quantity, groundwater recharge and water quality design and performance standards established by Article IV of this chapter.
Manufactured treatment devices may be used to meet the requirements of Article IV of this chapter, provided that the pollutant removal rates are verified by the New Jersey Corporation for Advanced Technology and certified by the Department.
Nonverified manufactured treatment devices may also be used for purposes other than underground discharge of stormwater, where such devices provide a clear benefit to stormwater quality or flow control in a manner that facilitates improved nonstructural stormwater management controls on the site, or avoids the need for approval of off-site mitigation. The benefits of proposed nonverified manufactured treatment devices must be proved to the satisfaction of the review agency.
Manufactured treatment devices may be used only where the maintenance plan required by Article X ensures that the manufactured device will be properly maintained for its functional lifespan and will be replaced as needed with management measures that are at least as effective as the original manufactured treatment device working in accordance with manufacturer's specifications.