Rahway Arch Site Remediation Project
Project Update through 2018
Site Remediation - Remediation of the Rahway Arch Site consists of:
- Engineering controls, comprised of an engineered fill cap system that will eliminate direct contact hazards, stabilize the impoundments and berms, control and manage stormwater, eliminate infiltration into the groundwater and the Rahway River and eliminate the on-site safety hazards
- Administrative controls, including a deed restriction and remedial action permits
- Riparian area enhancement
A Licensed Site Remediation Professional (LSRP) is overseeing the site remediation activities.
Cap Installation - Installation of the cap system began in 2015 and is currently ongoing. The cap system is being installed by Soil Safe Incorporated, using recycled soil manufactured into engineered fill at a dedicated, temporary on-site Class B recycling facility. Placement of fair drainage material (a higher permeability base layer that allows the pore water pressure to dissipate) has been completed in Impounds 2, 3, 4 and 6 and is ongoing in Impounds 1 and 5. Lifts of reduced permeability cap material have been placed in Impounds 2, 3, 4 and 6 and will soon be commencing in Impounds 1 and 5. Cap material is being placed in accordance with the geotechnical specifications, with rest periods between the lifts to allow excess pore water pressure to dissipate and maintain the stability of the site.
The berms bordering the Rahway have been widened and strengthened with the engineered fill. The west side of Impound 3 has been raised in accordance with the remedial design, and this area is no longer subject to inundation by high tide water levels in the Rahway River.
Stormwater Management – The capped site will contain four stormwater management basins. Because of the low permeability cap system, these basins have been designed to manage all of the precipitation as runoff. Stormwater Management Basin B (Impound 3) has been completed and is functioning as designed. The other basins are being constructed as the cap installation proceeds.
Site Cleanup – All of the wood waste that had been left on the site has been removed. Flotsam, deposited by Hurricane Sandy and other storms, has been collected and removed, including from the adjacent wetlands. All of the waste has been sent to approved solid waste disposal facilities.
Environmental Testing – Prior to placement in the cap, the engineered fill material is tested and must be approved by the LSRP before it is placed to ensure that it meets the environmental requirements contained in the RAW. The engineered fill must meet current Residential Remediation Standards (NJAC 7:26D) for all parameters except two pre-existing PAH compounds, benzo(a)pyrene and dibenz(a,h)anthracene. During the site investigation these compounds were measured at elevated concentrations throughout the site.
Over 950 samples of engineered fill material have been collected to date. All of the material received at the facility was conditionally pre-approved in accordance with the DEP approved protocol; and importantly, all the manufactured product placed in the cap has been tested and meets the fill use criteria in the RAW. No soil has had to be removed for off-site disposal. The concentrations of the two PAH compounds that can exceed Residential Standards are significantly below the limits established by the RAW.
Geotechnical Monitoring – The geotechnical design developed from the Geotechnical Investigation included a plan for monitoring the site during installation of the cap to ensure that the berms and the site would remain stable throughout the remedial action and into the future. Monitoring included multiple settlement plates, inclinometers and piezometers.
Geotechnical monitoring has been ongoing since the start of cap installation under the direction of the geotechnical professional engineer. Settlement is occurring slowly, as anticipated, as the waste materials and underlying native layers compress under the cap. This slow compression results in increasing strength and stability of these underlying strata. In general, the shear strength of the underlying strata has increased between 200 to 300 pounds per square foot (psf). The results are in line with the anticipated results developed from the geotechnical modeling performed prior to the start of the remedial action.
Groundwater and Surface Water Monitoring – Periodic groundwater and surface water monitoring are being conducted throughout the remediation project. While the results of the testing naturally fluctuate with tides, season and other factors, no statistically significant changes have been observed in groundwater or surface water quality as the site is being capped.
Groundwater elevation is also being monitored. Prior to the start of the remediation, groundwater was mounded under the site because of the rainwater infiltration and recharge that percolated through the contaminated sludge in the open impoundments. This infiltration is being reduced by the cap and the mounding has decreased. A slight increase in the groundwater elevation in the shallow perimeter monitoring wells has been observed, likely from the reduction in groundwater mounding.
Riparian Area Enhancement – As part of the remedial action, riparian areas outside the limits of remediation are being enhanced. This enhancement consists of removing non-native invasive species and replacing them with native trees, shrubs and grasses that will improve the quality of the habitat in these riparian areas. To date, most of the invasive species have been eliminated. Plantings will occur in 2019 and 2020 prior to the fish spawning moratorium periods.
Summary – Remediation of the Rahway Arch site is progressing as planned and is on schedule. The environmental quality of the engineered fill being used in the cap is better than was anticipated at the time the RAW was developed. The site is stable and is becoming stronger and more stable as the remediation progresses. Monitoring is showing that the environment is being protected and the area is being enhanced.
The Borough of Carteret has designated the site a Redevelopment Zone. The State of New Jersey has designated it as both an Urban Enterprise Zone and an Economic Opportunity Zone. When the remediation is complete, the Rahway Arch site will be a valuable asset to both the Borough of Carteret and the State of New Jersey.