Negotiating Reduced Monitoring Requirements for Delaware River Dredging

Industrial Petrochemical Company, Delaware

Weston Solutions, Inc. (WESTON^®) negotiated reasonable and environmentally protective monitoring and operational requirements with the Delaware Department of Natural Resources and Environmental Control (DNREC) for clamshell dredging in the Delaware River for a confidential industrial client. The client, who relied on WESTON’s expertise with new DNREC permitting requirements, had two major objectives: to ensure its maintenance dredging project would be completed on schedule, and to protect aquatic resources from the potential risk presented by elevated turbidity levels.

This industrial client operates a barge berth and cooling water intake on the Delaware River that are dredged every 3 years. When the project was initiated, the berth and intake had jointly accumulated approximately 50,000 cubic yards of sediments, which restricted berthing depth and intake flow rates.

Prior to contacting WESTON, the client had already performed sediment characterization and received a Delaware 401 Water Quality Certificate (WQC) and Subaqueous Lands Permit from DNREC; however, DNREC‘s Water Quality Certificate included new real-time monitoring requirements. These new mandates, driven by recent changes in state water quality regulations, specified that dredging should be discontinued when certain water quality parameters were reached, including a criterion for turbidity measured 100 feet from the dredge. The permit did not specify several crucial sampling parameters, such as sampling depth, sampling frequency, and sampling duration. Overall, the client believed that the newly imposed monitoring requirements were vague, and the stringent turbidity requirements would prevent the dredging from being completed.

WESTON’s Experience Helps Solidify Plan

To negotiate a more concrete and realistic monitoring plan with DNREC, WESTON performed the following five tasks:

• Compiled historical information, chemical data, and profiles on the turbidity and total suspended solids (TSS) levels from clamshell dredging
• Modeled turbidity/TSS plumes from clamshell dredging in predominantly silty sediments
• Determined the sensitive species and aquatic receptors present in the proposed project area
• Presented results from above tasks to DNREC and provided recommendations for a monitoring plan
• Suggested operational modifications for the clamshell dredge to minimize turbidity

WESTON conducted a detailed literature review and compiled the results from various dredging events that included turbidity and/or TSS studies. WESTON evaluated the results and determined which studies were most similar to Delaware River conditions at the project site, based on river width and flow rate, sediment characteristics, and dredging methodology. WESTON summarized the results of the various studies for our client and DNREC, and tabulated the monitoring results for turbidity and TSS. The literature analysis clearly indicated that the state’s turbidity requirement in the permit could not be met for clamshell dredging.

To further verify the results, WESTON modeled the turbidity plume caused by clamshell dredging using the "DREDGE" component of the Automated Dredging and Disposal Alternatives Modeling System (ADDAMS) developed by the U.S. Army Engineer Research and Development Center (ERDC). The model uses site characteristics, near- and far-field characteristics, dredging methods, and transport method data to predict sediment resuspension and containment release by the dredge. Using the model output, WESTON created a monitoring plan for turbidity that would accurately characterize the spatial and temporal extent of the turbidity plume.

WESTON also used the model to evaluate how various dredging operational practices would affect turbidity levels. With a goal of minimizing turbidity, WESTON evaluated various dredging cycle times, bucket sizes, clamshell bucket type, and use of an environmental bucket, and how these factors would affect the turbidity plume. WESTON coupled this modeling output with information from dredging contractors on the effect the operational practices would have on dredging duration and cost. WESTON determined which practices would have the greatest impact on turbidity, with the least impact on dredging duration and cost.

WESTON presented the results of the literature search, sensitive species evaluation, and modeling efforts to DNREC on behalf of the client. DNREC personnel were receptive to the presentation, and noted their appreciation of both the level of detail and scientific basis for our client’s request to modify the monitoring plan in permit.

Permit Modifications Smooth Project Flow

Based on WESTON’s efforts and recommendations, DNREC modified the permit requirements and approved the proposed monitoring plan. DNREC was pleased by the client’s willingness to modify dredging operations to reduce turbidity, and the client was pleased that DNREC was willing to adjust the monitoring and cessation requirements. Overall, all parties’ needs were satisfied by the negotiated permit. Furthermore, WESTON continued to strengthen its strong relationship with DNREC coastal zone and subaqueous lands regulators. Following negotiations, the client successfully completed its dredging project without a single interruption in the operation of the dredge.