N.J. Admin. Code § 7:7-12.6

Current through Register Vol. 56, No. 24, December 18, 2024

Section 7:7-12.6 - Maintenance dredging

(a) Maintenance dredging is the periodic removal of accumulated sediment from previously legally dredged navigation and access channels, marinas, lagoons, canals, or boat moorings for the purpose of safe navigation.

1. For a project to be considered maintenance dredging, the applicant shall demonstrate through historical data, including, but not limited to, previously issued dredging permits, previous dredging contracts, historic bathymetric surveys, and/or aerial photography that:

i. The proposed dredge area is limited to the same length and width as a previous dredging operation;

ii. The proposed water depth is the same as a previous dredging operation or as historical water depths within the proposed dredge area; and

iii. The proposed dredge area has historically been used for navigation or mooring of vessels requiring the proposed water depth.

(b) Maintenance dredging and the management of the dredged material shall be conducted in accordance with Appendix G.

(c) Maintenance dredging is conditionally acceptable to the authorized depth, length, and width within all general water areas to ensure that adequate water depth is available for safe navigation, provided:

1. An acceptable dredged material placement site, with sufficient capacity will be used (see N.J.A.C. 7:7-12.9, Dredged material disposal in water areas, N.J.A.C. 7:7-15.12, Dredged material placement on land, and Appendix G). The Department will make an acceptable use determination for the beneficial use of dredged material in accordance with Appendix G;

2. Pre-dredging chemical and physical analysis of the dredged material, including water quality predictive analyses for surface water and ground water may be required where the Department suspects contamination of sediments. Additional testing, such as bioaccumulation and bioassay testing of sediments, may also be required as needed to determine the acceptability of the proposed placement site for the dredged material. The results of these tests will be used to determine if contaminants may be resuspended at the dredging site and what methods may be needed to control their escape. The results will also be used to determine acceptability of the proposed dredged material placement method and site;

3. Turbidity concentrations (that is, suspended sediments) and other water quality parameters at, downstream, and upstream of the dredging site, and discharges from dredged material management areas (see N.J.A.C. 7:7-9.49) shall meet applicable Surface Water Quality Standards at N.J.A.C. 7:9B. The Department may require the permittee to conduct biological, physical, and chemical water quality monitoring before, during, and after dredging and disposal operations to ensure that water quality standards are not exceeded;

4. If predicted water quality parameters are likely to exceed Surface Water Quality Standards at N.J.A.C. 7:9B, or Ground Water Quality Standards at N.J.A.C. 7:9C, or if pre-dredging chemical analysis of dredged material, including surface or ground water quality predictive analyses, reveals significant contamination, the Department will work cooperatively with the applicant to fashion acceptable control measures and will impose seasonal restrictions under specific circumstances identified at (c)7 below;

5. For mechanical dredges, deploying silt curtains at the dredging site may be required, if feasible based on site conditions as provided in Appendix G. Where the use of silt curtains is infeasible, dredging using closed watertight buckets or lateral digging buckets may be required. The Department may also require the use of additional best management practices when highly contaminated sediments are to be dredged in accordance with Appendix G;

6. For hydraulic dredges, specific operational procedures designed to minimize water quality impacts, such as removal of the cutter head, flushing of pipeline sections prior to disconnection, or limitations on depth of successive cuts, may be required;

7. The Department may authorize dredging on a seasonally restricted basis only, in waterways characterized by the following:

i. Known spawning, wintering or nursery areas of shortnose sturgeon, winter flounder, Atlantic sturgeon, alewife, blueback herring, striped bass, white perch or blue crab;

ii. Water bodies downstream of known anadromous fish spawning sites under N.J.A.C. 7:7-9.5, Finfish migratory pathways, where the predicted turbidity plume will encompass the entire cross-sectional area of the water body, thus forming a potential blockage to upstream migration;

iii. Areas of contaminated sediments with high levels of fecal coliform and/or streptococcus bacteria, and/or hazardous substances adjacent to (upstream or downstream) State approved shellfishing waters and public or private bathing beaches; or

iv. Areas within 1,000 meters or less of oyster beds as defined in N.J.A.C. 7:7-9.2; and

8. Maintenance dredging side slopes shall not be steeper than three vertical to one horizontal adjacent to wetlands to prevent undermining and/or sloughing of the wetlands.

(d) Reprofiling consists of the movement of sediments from a specific area of a berth or channel to a specific adjacent and deeper location, without removing the sediments from the water body. Reprofiling is prohibited in all water areas, except the New York-New Jersey Harbor Area of Region 1, as described in Appendix G, excluding the Raritan Bay and its tributaries east of the Cheesequake Creek, provided:

1. The applicant has demonstrated that there is no other available dredged material management alternative;

2. The project involves the movement of less than 5,000 cubic yards of material;

3. The depth of the sediments to be moved by the reprofiling operation is limited to three feet;

4. The adjacent deep water area into which the sediments will be moved has sufficient capacity to accommodate the relocated sediments in a stable manner, without interfering with the use of adjacent navigation channels or berths; and

5. The reprofiling is performed by dragging a steel beam or pipe across the berth and/or channel bottom, thereby leveling accumulated sediment to a uniform, specified depth. Alternative procedures will be considered only under special instances where the use of a drag bar is impractical due to limited space in the project area.

(e) Propwash dredging, which is the movement of sediment by resuspending accumulated material by scouring the bottom with boat propellers or specially designed equipment with propellers, is prohibited.

(f) Rationale: Maintenance dredging is necessary to provide for the safe navigation of State and Federal navigation channels and to provide access to marinas, docks, ports, and other appropriate water dependent development. Safe navigation is critical to the State's recreational and commercial boating industry and marine commerce. However, maintenance dredging must be carried out in such a way that special areas and other identified environmentally sensitive areas are not unnecessarily disturbed.

Potential water column impacts vary with each type of dredging method employed, that is, mechanical or hydraulic. Mechanical methods have been documented to release more suspended sediments at the dredging site than hydraulic methods. Hydraulic dredging causes greater mixing of sediments with water which is an important consideration when dredging contaminated sites, since slurry water is usually released into the water body.

Previously dredged areas typically accumulate black muds high in clay and silt, detritus, and other organics and, if sources are present, toxic heavy metals, petroleum, and chlorinated hydrocarbons. The majority of potentially toxic contaminants are closely bound to fine grained sediment particles and may or may not be available for uptake by aquatic organisms. Bioaccumulation testing is necessary to determine if there is contaminant uptake.

Presently available equipment and operational practices can contain or reduce off site movement of suspended particles. Efficiency and applicability of control equipment depends on hydrologic conditions at the site.

The information available on aquatic species responses and/or mortality due to dredge-induced water quality changes is incomplete. It is known however that egg and larval forms of aquatic biota are more sensitive than adult stages. American oyster eggs and larvae are known to be sensitive to turbidity levels and durations that typically occur at mechanical dredging sites. Turbidity is known to block upstream migration of striped bass. Turbidity may, therefore, block other anadromous species during spring upstream migration.

Little information exists on the resuspension of fecal bacteria in contaminated sediments. The potential exists that a dredging turbidity plume could carry fecal bacteria into harvestable shellfish beds or human bathing beaches. This may result in unacceptable human health hazards.

Aquatic finfish and blue crabs which winter in New Jersey's estuarine and tidal waters are lethargic at cold water temperatures. Large scale mechanical or hydraulic dredging could entrain and kill significant numbers, since they would not be able to evacuate a dredging area.

Reprofiling is generally prohibited under this chapter because it merely moves dredged material rather than removing it from the system. Ultimately, this material is likely to have to be removed, resulting in handling the material twice and increasing the impacts associated with the movement of the accumulated sediment. Reprofiling is acceptable under limited circumstances as an interim measure in the New York-New Jersey Harbor Area when other management techniques are unavailable, as it will allow existing maritime uses to continue operation while a more permanent solution is sought.

Propwash dredging is indiscriminate, releasing sediment into the water column with no control to minimize impacts on water quality, or control of the fate of the resuspended sediment. Sediment resuspended in this manner could smother shellfish beds, submerged vegetation habitats, and result in the loss of navigability in adjacent berths and channels. Thus propwash dredging is prohibited under these rules.

N.J. Admin. Code § 7:7-12.6

Renumbered from 7:7E-4.6 by 47 N.J.R. 1392(a), effective 7/6/2015