All stormwater management system installations shall be inspected during the time of construction as outlined in Chapter 324, Site Plan Review, Article III, § 324-17. All stormwater management systems and storm networks shall be inspected on an annual basis for compliance with this chapter and the NJDEP regulations.
As used in this chapter, the following terms shall have the meanings indicated:
- STORMWATER MANAGEMENT SYSTEM
- Any type of detention, retention or infiltration facility designed to manage the rate and volume of stormwater runoff.
- DETENTION FACILITY
- A stormwater management system which temporarily impounds runoff and discharges it through an hydraulic outlet structure to a downstream conveyance system. While a certain amount of outflow may also occur via infiltration through the surrounding soil, such amounts are negligible when compared to the outlet structure discharge rates and are, therefore, not considered in the facility's design. Since a detention facility impounds runoff only temporarily, it is normally dry during nonrainfall periods. (Taken from New Jersey Department of Environmental Protection Stormwater Management Facilities Maintenance Manual, June 1989.)
- INFILTRATION FACILITY
- A stormwater management system which temporarily impounds runoff and discharges it via infiltration through the surrounding soil. While an infiltration facility may also be equipped with an outlet structure to discharge impounded runoff, such discharge is normally reserved for overflow and other emergency conditions. Since an infiltration facility impounds runoff only temporarily, it is normally dry during nonrainfall periods. (Taken from New Jersey Department of Environmental Protection Stormwater Management Facilities Maintenance Manual, June 1989.)
- RETENTION FACILITY
- A stormwater management system which, similar to a detention facility, temporarily impounds runoff and discharges its outflow through an hydraulic structure to a downstream conveyance system. Unlike a detention facility, however, a retention facility also includes a permanent impoundment and, therefore, is normally wet, even during nonrainfall periods. Storm runoff inflows are temporarily stored above this permanent impoundment. (Taken from New Jersey Department of Environmental Protection Stormwater Management Facilities Maintenance Manual, June 1989.)
- SUBSURFACE STORMWATER MANAGEMENT SYSTEM
- A detention facility constructed below the ground surface usually constructed of piping, concrete vaults or the void space in stone.
All stormwater management systems shall be designed in accordance with Chapter 324, Site Plan Review, Article IV, §§ 324-23 through 324-29, or Chapter 400, Zoning, Article V, § 400-34, and shall be designed following all NJDEP regulations utilizing the techniques and BMPs outlined in the NJDEP stormwater regulations.
Existing lakes, ponds, swales or wetland areas (including buffer areas) shall not be permitted to act as a stormwater management system in any manner whatsoever.
Detention and retention basins must be constructed to minimize sediment, pollutants and any other detrimental effects upon adjoining or downstream wetlands, ditches, swales and other types of water bodies. Detention and retention basins must be constructed utilizing best management practices and techniques and shall include bioengineering methods such as sedimentation areas, biofilters and aquatic beach areas. Prior to the design of all stormwater management systems, soil borings and/or backhoe test pits shall be performed in the presence of the Municipal Engineer to verify subsurface soil conditions.
Wetlands vegetation in the form of mature trees, shrubs and grasses must be incorporated in the basin design and must be shown on an appropriate landscaping plan. The plan shall be subject to review and comment by the Gibbsboro Environmental Commission.
Existing inlet structures must be properly labeled to meet NJDEP standards. New inlet castings must meet NJDEP BMP standards.
All proposed stormwater management systems are to have a postconstruction inspection prior to final acceptance by the Borough. Final inspection shall be performed by the Municipal Engineer.
All silt is to be removed from retention or detention basins before final basin grading and permanent stabilization.
A postconstruction percolation test will be required in the basin bottom to verify previously determined percolation rates.
All retention or detention basin side slopes as well as the basin bottom shall be properly stabilized with permanent stabilization.
All stormwater piping and inlets which feed retention, detention or subsurface basins shall be cleaned of all sand, silt and debris before final acceptance.
All subsurface stormwater management systems shall be cleaned of all sand, silt and debris before final acceptance.
A written stormwater maintenance plan must be prepared and shall be part of the subdivision or site plan approval process. The plan shall follow the guidelines and procedures listed in the NJDEP stormwater regulations.
All streets must be swept prior to acceptance.
A cash contribution by the developer shall be provided to establish a basin maintenance trust for the Borough for those stormwater management systems to be dedicated to or to be maintained by the municipality. Contributions will be required to be deposited into an interest-bearing reinvestment trust established for the sole purpose of future stormwater management system maintenance and repair.
Contributions for the maintenance of detention and retention basins shall be in accordance with the following schedule. The schedule is subject to an annual review by the Planning Board Engineer and shall be adjusted according to the current rates for basin lawn care.
Contributions for subsurface stormwater management systems shall be determined by the Borough Engineer and the Planning Board on a case-by-case basis.
Contributions must be posted within the municipality at the time of the submittal of the performance bond.
All proposed basins, regardless of ownership, must have a dedicated access from the public right-of-way. The access should include a stabilized hard surface suitable for the passage of maintenance and inspection equipment and vehicles. The access must be secure by means of gates or an equivalent, and locks and keys shall be provided to the municipality.
Annual inspection of existing basins not maintained by the municipality is required and must include checking for obstructions and the removal of debris and accumulated particles such as silt and sediment.
Annual inspection shall include:
Removal of all accumulated silt and debris from stone riprap energy dissipater aprons associated with basin inflow pipes; replacement of stone riprap if necessary.
Removal of debris from outflow structure orifices, weirs, overflow grating, inlets and piping, etc.
All landscaping shall be properly trimmed, mulched and maintained. Dead landscaping shall be replaced in accordance with the approved subdivision plan and/or approval by the Mayor and Council of the Borough.
All fencing which is broken, deteriorated, missing or out of alignment must be replaced and/or repaired.
Mowing of the grass on a regular basis is required to ensure the aesthetic and hydraulic quality of the basin.
Mowing should be performed when grass is between four inches and six inches high. The grass should never be allowed to exceed six inches in height.
All clippings must be removed from the basin immediately following mowing.
Removal of leaves from the basin during the fall is also required.
In order to ensure proper function of all basins, every five years each basin bottom shall be scarified to a depth of four inches to remove sediments and silts. Then, four inches of granular topsoil must be added and the surface reseeded as detailed previously.
At no time after final basin grading and permanent stabilization should any equipment be allowed to operate within the basin which could smear or compact the soils leading to a reduction in the percolation rate. This includes mowing and the annual removal of accumulated silt.
Property owners and homeowners' associations who have lakes or ponds which are classified as dam structures or which fall under the guidelines of the New Jersey Department of Environmental Protection Dam Safety Section must also meet the minimum requirements of that state agency.