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The Diamond Alkali Superfund site includes the former manufacturing facility at 80-120 Lister Avenue in Newark, New Jersey, the Lower Passaic River Study Area (LPRSA), the Newark Bay Study Area, and the areal extent of contamination. The LPRSA includes the 17-mile tidal stretch of the river from Dundee Dam to Newark Bay, and tributaries. The Newark Bay Study Area includes Newark Bay and portions of the Hackensack River, Arthur Kill and Kill van Kull. The area surrounding the site is densely populated and heavily industrialized.

Production of DDT and other chemical products began at 80 Lister Avenue in the 1940s. In the 1950s and 1960s, the Diamond Alkali Company owned and operated the facility, manufacturing agricultural chemicals, including the herbicides used in the defoliant known as “Agent Orange,” among other products. A by-product of these manufacturing processes was 2,3,7,8-TCDD (dioxin), an extremely toxic chemical. In 1971, Diamond Alkali sold 80 Lister Avenue.

In 1983, sampling by the state of New Jersey and the EPA at and near 80 Lister Avenue and in the river revealed high levels of dioxin. The site was listed on the Superfund National Priorities List (NPL) in 1984. Dioxin, pesticides, and other hazardous substances were found in the soil and groundwater at 80-120 Lister Avenue; and dioxin, polychlorinated biphenyls (PCBs), metals, polycyclic aromatic hydrocarbons (PAHs), and pesticides were found in sediment in the Lower Passaic River.

New Jersey prohibits consumption of fish or shellfish from the Lower Passaic River and Newark Bay. Cleanup activities to date include immediate actions at 80-120 Lister Avenue and surrounding properties, removal actions in the Lower Passaic River, and the interim remedy for 80-120 Lister Avenue. In March 2016, EPA selected the remedy for the lower 8.3 miles of the Lower Passaic River. Additional investigations and planning for long-term cleanup are ongoing.

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What Has Been Done to Clean Up the Site?


In 1983, EPA and New Jersey Department of Environmental Protection (NJDEP) found high levels of dioxin at and in the vicinity of 80-120 Lister Avenue and in the Passaic River. Based on these investigations, EPA and NJDEP initiated several emergency response actions including: securing the properties at 80-120 Lister Avenue, covering the exposed soils to prevent migration and addressing dioxin found on nearby properties through excavation, vacuuming, and other means. EPA proposed the site for the NPL in September 1983, and it was finalized on September 21, 1984. In 1984, the Diamond Alkali Company (by then known as the Diamond Shamrock Company) acquired the property at 120 Lister Avenue, and in 1986, it repurchased 80 Lister Avenue. Shortly thereafter, Chemical Land Holdings, Inc. (now Tierra Solutions, Inc. (Tierra)) took title to both properties.

From 1984 to 1987, with oversight by NJDEP, Occidental Chemical Corporation (OCC), the corporate successor to the Diamond Alkali/Diamond Shamrock Company, completed a remedial investigation/feasibility study (RI/FS) for 80-120 Lister Avenue. The RI/FS showed that the 80-120 Lister Avenue properties were contaminated by a large number of hazardous substances including dioxin, semi-volatile and volatile compounds, herbicides, pesticides, PCBs, and metals. The contamination was widespread and affected soil, groundwater, air, surface water, and building structures. On August 1, 1987, EPA issued the Proposed Plan for 80-120 Lister Avenue, and on September 30, 1987, EPA selected an interim containment remedy for the Lister Avenue facility. The remedy consisted of capping, subsurface slurry walls and a flood wall, and a groundwater collection and treatment system. The remedy prevents exposure to contaminated soil and prevents further releases to the river. Construction of the remedy at the 80-120 Lister Avenue facility was carried out by OCC , under EPA oversight. Construction was completed in 2001.

In 1994, OCC signed an Administrative Order on Consent with EPA to investigate a six-mile stretch of the Lower Passaic River, with the work performed by Tierra on OCC’s behalf. This investigation found contaminants of concern that originated from the Diamond Alkali facility, in particular, 2,3,7,8-TCDD and pesticides, throughout the six miles, with the highest concentrations adjacent to the 80-120 Lister Avenue facility. This investigation also found many other contaminants of concern not necessarily linked to Diamond Alkali’s operations, and indicated that contaminated sediment moved into and out of the six-mile stretch, leading to the conclusion that a more comprehensive study was required. In 2002, EPA expanded the scope of the investigation to include the entire 17-mile LPRSA.

While working with OCC and Tierra on the Lister Avenue facility and the early studies of the river, EPA identified other potentially responsible parties (PRPs) for the Lower Passaic River besides OCC. A number of companies that owned or operated facilities from which hazardous substances were potentially discharged to the river formed the Cooperating Parties Group (CPG). In 2004, EPA signed a settlement agreement with the CPG in which the group agreed to pay for EPA to perform the RI/FS for the 17-mile LPRSA. The settlement agreement was amended in 2005 and 2007, adding more parties, for a total of over 70 parties.

Also in 2004, EPA and OCC signed an agreement in which OCC agreed to conduct a separate RI/FS of the Newark Bay Study Area (Newark Bay and portions of the Hackensack River, Arthur Kill and Kill van Kull), investigating the extent of dioxin contamination and co-located contaminants, with EPA oversight. Finally, also in 2004, EPA formed a partnership with the U.S. Army Corps of Engineers, New Jersey Department of Transportation, U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, and NJDEP to conduct a joint study of the LPRSA. The goal of the partnership was, to the extent possible, to integrate the RI/FS being performed under the Superfund program with a Feasibility Study under the Water Resources Development Act.

From 2004 to 2007, EPA investigated contamination in sediment and water of the Lower Passaic River, and investigated the major tributaries, combined sewer overflows and stormwater outfalls to the river. In 2007, the CPG entered into a new agreement with EPA in which the group agreed to take over the performance of the 17-mile LPRSA RI/FS from EPA. EPA provides oversight of the CPG’s performance of the 17-mile LPRSA RI/FS. During the course of the 17-mile study, EPA concluded that since the lower 8.3 miles of the river contain the bulk of the contaminated sediment which is the source of most of the risk associated with the Lower Passaic River, addressing this portion of the river first would better support the overall protection of human health and the environment. Because about 90 percent of fine-grained (and, therefore, more heavily contaminated) sediment is below river mile 8.3, EPA undertook a targeted RI and Focused Feasibility Study (FFS) of the lower 8.3 miles. EPA issued the Record of Decision which selected a remedy for the lower 8.3 miles of the Lower Passaic River on March 4, 2016.


EPA, in partnership with state and federal agencies, is addressing the site’s cleanup. Cleanup actions at the site were taken in 2001, 2012, and 2014. In 2001, the interim remedy at 80-120 Lister Avenue was completed. Occidental Chemical Corporation (OCC) performs operation and maintenance of the Lister Avenue remedy, and continues to monitor the performance of the remedy to assure the protectiveness of the actions taken to date. Pursuant to statutory Five-Year Reviews, EPA has been evaluating the protectiveness of the remedy since it was completed. The most recent Five-Year Review was completed in 2016. EPA is concluding an evaluation of the current availability of technologies that may be appropriate to address the contamination over the long term.

Cleanup activities in 2012 and 2014 included removal and disposal of contaminated sediment from two areas of the river. The 2012 Tierra Removal dredged the most concentrated inventory of dioxin-contaminated sediment from the Lower Passaic River adjacent to the 80-120 Lister Avenue facility. The 2014 River Mile 10.9 Removal dredged and capped a highly contaminated mudflat on the east bank of the river near Lyndhurst. 

EPA’s early outreach efforts included alerting the public about New Jersey’s prohibitions and advisories on fish and crab consumption for the tidal Passaic River and Newark Bay. Exposure to even low levels of contaminants through fish and crab consumption may have long-lasting health effects on people. The New Jersey fish and crab consumption prohibitions and advisories are based on the levels of mercury, PCBs, and dioxins in fish and crab. The NJDEP and New Jersey Department of Health have issued consumption advisories (available on the agencies’ web sites) to guide anglers and other members of the public if fish and crab are harvested from within New Jersey State waters.

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What Is the Current Site Status?

The Diamond Alkali site is being addressed by EPA in four operable units: the 80-120 Lister Avenue properties, the lower 8.3 miles of the Lower Passaic River, the 17-mile LPRSA, and the Newark Bay Study Area. The site is also being addressed in several stages: immediate actions and interim remedial actions on the land portion of the site, time critical and non-time critical removal actions in the Passaic River, a long-term remediation of the 17-mile LPRSA starting with remediation of the lower 8.3 miles, and a long-term remediation of Newark Bay.

Immediate Actions: The 1983 dioxin discovery led to the 80-120 Lister Avenue properties being secured by a fence and twenty-four hour security guard service. Exposed soils were covered with geofabric to prevent potential migration of contamination. Dioxin-contaminated soils and debris found on nearby properties were removed by excavation, vacuuming, and other means.

Interim Remedy: In 1987, EPA selected an interim remedy for the 80 and 120 Lister Avenue properties that included: (1) construction of a slurry wall and flood wall around the properties; (2) installation of a cap over the properties; and (3) pumping and treating of groundwater to reduce the migration of contaminated groundwater. Construction of the remedy was completed in 2001. Maintenance of the remedy is performed by Occidental Chemical Corporation (OCC), with EPA oversight. EPA performs periodic reviews of the protectiveness of the remedy.

Non-Time Critical Removal: In June 2008, EPA and OCC signed an agreement for a non-time-critical removal action to remove 200,000 cubic yards of contaminated sediment from the river adjacent to the 80-120 Lister Avenue facility. This action is referred to as the "Tierra Removal." Sediment at depth adjacent to the facility was found to have the highest levels of 2,3,7,8-TCDD measured in the river. Dredging, dewatering, and transporting off-site of the first 40,000 cubic yards of sediment (known as Phase 1 of the Tierra Removal) was completed in 2012. The agreement contemplates the siting and use of a confined disposal facility as a receptacle for the dredged materials from Phase 2 (160,000 cubic yards). However, this has not occurred and may no longer be practicable. EPA is integrating this work with the lower 8.3-mile remedy in a coordinated and consistent manner. Both phases of this removal action are considered source removal projects.

Time-Critical Removal: In June 2012, EPA and the Cooperating Parties Group (CPG) signed an agreement for a time-critical removal action to address the risks posed by high concentrations of dioxins, PCBs, and other contaminants found at the surface of a mudflat on the east bank of the river at River Mile 10.9 in Lyndhurst, New Jersey. This action is referred to as the "River Mile 10.9 Removal." The action involved placing an engineered cap over contaminated sediment, thereby reducing exposure and preventing migration of the contamination to other parts of the river. In order to ensure that the action did not make flooding worse, a sufficient volume of surface sediment was first dredged from the area to make space for the cap. The work began in 2013 and was substantially completed in 2014, with the exception of an area of contaminated sediment located above a utility pipeline that runs under the river. An investigation of this small area is ongoing. This time-critical removal action is not a final remedy; a final decision for the River Mile 10.9 Removal area will be made by EPA as part of the 17-mile LPRSA Record of Decision.

17-mile Lower Passaic River Study Area (LPRSA): The CPG performed sampling for the RI between 2008 and 2014. EPA  approved the CPG’s Baseline Human Health Risk Assessment and Baseline Ecological Risk Assessment (BERA) for the LPRSA, including a BERA for the discrete upper 9-mile reach, in July 2017 and June 2019, respectively. The final RI Report was submitted by the CPG in July 2019 and has been conditionally approved by EPA pending approval of the bioaccumulation model. The bioaccumulation model is an appendix to the RI that is still under development; the model is expected to be finalized and peer reviewed by approximately fall 2021. ,

In July 2017, the CPG proposed moving away from the original schedule for a final  ROD for the LPRSA, or upper 9 miles, and instead evaluating an interim remedy for source control. This would take advantage of cost efficiencies available if work can be undertaken in the upper 9 miles while the infrastructure constructed for the lower 8.3 remedy is in place, as well as reduce the disruption in the river and to the many communities along the river. Such an interim remedy would further incorporate an adaptive management approach into the site cleanup and would be integrated with the remedial action currently being designed for the lower 8.3 miles. EPA expects that an interim remedy that includes the cleanup of areas with elevated concentrations of contaminants (e.g. dioxins and PCBs) could result in expedited recovery of the river. An interim remedy for the upper nine miles, if selected, would not alter the previously selected cleanup for the lower 8.3 miles of the river. EPA projects that an interim remedy for source control that is initiated in late 2021 will be followed by some years of post-remedy monitoring, development of risk-based remedial goals and conclude in a final ROD. In August 2019, the CPG submitted a draft feasibility study for a possible interim remedy which is currently under EPA review.

As described above, concurrent with these river studies and removal actions, the sediment of the lower 8.3 miles of the river were found to be a major source of contamination to the rest of the river and Newark Bay. Therefore, EPA developed an RI/FFS to evaluate alternatives for an action to control this major source of contamination. The RI/FFS and a Proposed Plan describing EPA’s preferred alternative for remediating the sediment of the lower 8.3 miles were released for public comment in April 2014. During a four month public comment period, hundreds of comments were received. EPA carefully considered the comments and took them into account in developing the Record of Decision that was issued on March 4, 2016. The selected remedy for the sediment of the lower 8.3 miles includes an engineered cap that will be installed in the lower 8.3 miles, bank to bank. Before installation of the cap, approximately 3.5 million cubic yards of contaminated sediment will be dredged from the lower 8.3 miles, so that the cap does not make flooding worse and to accommodate continued commercial navigation in the 1.7 miles of the river closest to Newark Bay. The dredged materials will be barged to a sediment processing facility on the banks of the Passaic River or Newark Bay, dewatered and transported off-site to permitted facilities for disposal. The estimated cost of the remedy is $1.38 billion. In September 2016, EPA and OCC signed a legal agreement for OCC to perform the design of the lower 8.3-mile remedy, under EPA oversight. The design is underway.

Newark Bay Study Area: The RI/FS being conducted by OCC for Newark Bay and portions of the Hackensack, Arthur Kill and Kill van Kull is ongoing.

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