New Jersey Zinc/Mobil Chemical

Site Summary
August 2012

DePue, Illinois
Bureau County
Illinois EPA 0110300003
Rockford Region

Site Description

Total Acreage: 950
Lead Agency: Illinois EPA

NPL Listing: June 9, 1999
Congressional District 11
House 76 / Senate 38

The DePue/New Jersey Zinc/Mobil Chemical Corporation site is located along the north side of the Village of DePue and constitutes roughly one half of the village land mass. Initial plans for investigation and cleanup of the site were organized by unit, e.g., plant site soils, Interim Water Treatment Plant, Phosphogypsum Stack, Zinc Slag Pile, Lithipone Ridges and South Ditch. As the cleanup plans for the South Ditch progressed, this organization was found to be inappropriate for the complex site and the site was divided into five operable units (OUs) for investigation and remediation:

  • OU 1: South Ditch Contaminated Sediments
  • OU 2: Phosphogypsum Stack
  • OU 3: Former Plant Site Area (FPSA)
  • OU 4: Off-site Soils
  • OU 5: DePue Lake Sediments and the Flood Plain

The South Ditch, OU 1, is a drainage canal that feeds into Lake DePue and received discharges of contaminated groundwater and surface water from the site. The northern 120 to 150 feet of the ditch is incised into fill consisting of placed soil and slag material. The remainder of the ditch traverses marshy lowlands adjacent to Lake DePue. These discharges resulted in unnatural sediment containing total metals in concentrations up to 200,000 mg/kg each of copper and zinc. Pursuant to a 2003 Record of Decision, removal of contaminated sediment from the South Ditch was accomplished in 2005. The ditch and its immediate vicinity is included in the Lake DePue investigation.

The Phosphogypsum Stack, OU 2, is a large waste pile of phosphogypsum (resulting from conversion of phosphate rock into diammonium phosphate fertilizer), and its associated water control structures including drainage swales, clearwater dam, and constructed treatment wetland. The stack has been partly covered with native prairie vegetation and partly covered with fescue grass. A groundwater investigation is ongoing.

The FPSA, OU 3, includes the plant site property and adjacent bluffs. The Interim Water Treatment Plant, which treats and discharges treated surface and groundwater, is located in one of the former plant buildings. Soil and groundwater investigations are ongoing.

Off –site soils within the surrounding community, OU 4, have yet to be investigated systematically, though some select properties have been sampled. This investigation is to begin in 2012.

Lake, DePue a 524-acre backwater lake and the floodplain, OU 5, have been the focus of intense study in recent years. Recreational use of the lake has been degraded by accumulation of sediment from the Illinois River. (see

The remedial investigation has been recently completed and risk assessments (human health and ecological) are currently under review. The next step will be a Feasibility Study.

Site History

Mineral Point Zinc Company originally developed the site in 1905 as a primary zinc smelter producing slab zinc for use in the automobile and appliance industries. In addition, the site has at various times been the location of sulfuric acid manufacturing, paint pigment production, ammonium phosphate fertilizer manufacturing, refining and recovery of secondary metals from zinc ore (e.g., cadmium), secondary zinc smelting and zinc dust production. Between 1905 and 1989, portions of the site were owned and operated by New Jersey Zinc Company, Mobil Oil Corporation, Gulf & Western Industries, Horsehead Industries, and the Zinc Corporation of America. In 1990, the facility ceased operation and shortly after that, New Jersey Zinc demolished most of the remaining structures. Through various corporate mergers, acquisitions and the bankruptcy of Horsehead, responsibility for the site has fallen to Viacom International Incorporated/CBS and the ExxonMobil Corporation. These two companies have formed an entity known as "The DePue Group," which collectively represents the potentially responsible parties (PRPs) for the site. In 1995, the DePue Group entered into an interim consent order with Illinois EPA and the Illinois Attorney General's Office (IAGO) for investigation of the site and evaluation of possible remedial actions.

Investigative History / Contaminants

Environmental concerns were created by waste disposal activities and discharges from the former smelter, sulfuric acid plant, paint pigment plant and the diammonium phosphate fertilizer plant. These activities produced a primary zinc smelter slag pile in excess of 702,000 cubic yards or 570,000 tons; several ridges of paint pigment plant waste, sometimes referred to as the lithipone ridges, containing in excess of 64,000 tons; a veneer of industrial waste varying from 6 inches to several feet over the entire 195-acre former plant site; a more than 140-acre Phosphogypsum Stack; discharges of wastewater and sediment to DePue Lake; and many other impoundments and waste piles. Significant discharges of metals to groundwater and surface water have occurred. All sources were found to contain elevated levels of metals including zinc, lead, arsenic, cadmium, chromium, and copper. In addition to metals contamination, there are elevated concentrations of sulfate, ammonia, and other compounds in the groundwater and surface water. The following investigations and actions have taken place.

  • December 1980 - A preliminary assessment was completed.
  • July 1983 - A second preliminary assessment was conducted.
  • March 1992 - The Illinois EPA conducted an expanded site inspection.
  • 1994 to 1996 – perimeter air monitoring study to verify airborne metals were not being released off-site
  • 1995 to 1997 - The Remedial Investigation/Feasibility Study (RI/FS) for the South Ditch was conducted.
  • 1999 – A site-wide remedial investigation work plan was developed and approved. Site efforts were re-organized into separate efforts for each operable unit; however, this work plan has provided the basis for much of the work in OU3.
  • 2006 – 2007 – Soil sampling from the DePue area was conducted to establish background conditions and support the forthcoming off-site soils investigation.
  • 2006 - 2009 – The remedial investigation for DePue Lake was conducted.
  • 2000 – 2011 – The hydrogeologic investigation of the Phosphogypsum Stack was initiated and is in its last stages of data collection, including sampling in off-site areas.
  • 2007 – 2011 – Consistent with the 1999 work plan, a remedial investigation for the plant area is currently underway and is in its last stages of data collection, including data collection in off-site areas.

Human Health Risks

Human health risks from the site have been formally evaluated at OUs 1 and 5 to date. For both OUs, metals are responsible for human health risks. Metals will likely be significant contributors to any potential risks from OUs 3 and 4.

The sediments in the South Ditch were determined to exceed the U.S. EPA's acceptable risk range for soil ingestion and dust inhalation for both child trespassers and on-site construction workers under current and potential future exposures. These sediments were removed from the South Ditch in 2005.. The risk assessment for OU5 is currently under review and its conclusions are not yet finalized.

Ecological Risks

Ecological risks from the site have been formally evaluated at OUs 1 and 5 to date. For both OUs, metals are primarily responsible for ecological risks. Lake DePue has a fish advisory for carp, white bass, and channel catfish due to detections of PCBs in fish tissue samples. In addition, there is a state-wide fish advisory for methyl mercury in predator fish. The site is not thought to be a significant contributor to the lake of PCBs and methyl mercury.

Results of the benthic organism testing indicated acute toxicity of South Ditch sediments to the test organisms. Numerous fish species, great blue herons, egrets and certain other waterfowl rely on these benthic organisms as food sources. In addition, some waterfowl, (e.g., mallard ducks) are dabblers and could ingest the contaminated sediments. These sediments were removed from the South Ditch in 2005.

The Lake DePue ecological risk assessment is currently under review and its conclusions are not yet finalized.

Remediation Acitvities

The major sources of contamination from the New Jersey Zinc site have been intercepted and prevented from entering DePue Lake. The following remedial activities have been completed:

  • In the 1980s, constructed a permeable reactive barrier south of the Zinc Slag Pile, known as the Iron-Rich Material trenches, to remove zinc and copper from the groundwater
  • Construction and operation of an Interim Water Treatment Plant to collect and treat contaminated runoff that previously flowed uncontrolled to the South Ditch
  • Construction of Surface Water Redirection and Protection System to segregate water in a 40-acre off-site drainage basin from contact with waste on the Plant Site
  • Reestablishment of vegetation on most of the plant site to mitigate dust generation and migration
  • Capping the Phosphogypsum Stack
  • Excavation of grossly contaminated unnatural sediments in the South Ditch. Contaminated sediments were placed in an on-site corrective action management unit (CAMU) on the plant site.

Completed in 1994:

  • Installed six more shallow piezometers
  • Initiated daily dust inspections and dust suppression with water truck
  • Fenced the plant site area
  • Implemented perimeter air monitoring plan
  • Implemented draft dust suppression plan
  • Regrading of Phosphogypsum Stack continued
  • Seeded northwest quadrant of Phosphogypsum Stack
  • Initiated sampling for PM-10 (10 micron) dust

Completed in 1995:

  • Regrading of Phosphogypsum Stack continued
  • Began conceptual design of Interim Water Treatment Plant
  • Submitted work plan for South Ditch Focused RI/FS
  • Submitted South Ditch Corridor Hydrogeologic Study technical memo
  • Submitted Plan for Collection and Treatment of Water
  • Authorized work for design of sump and piping for Interim Water Treatment Plant

Completed in 1996:

  • Continued placement of compost and final grading on Phosphogypsum Stack
  • Completed second treatability study for Interim Water Treatment Plant
  • Conducted field work for South Ditch Focused RI/FS
  • Completed construction of South Interceptor Trench

Completed in 1997:

  • Construction of the Interim Water Treatment Plant

Completed in 1998:

  • Modified Lift Station so it would operate during a 25-year flood
  • Began work on phased Site-Wide RI Work Plan
  • Conducted biweekly sampling of Outfall 002 at Phosphogypsum Stack
  • Submitted Site-Wide Remedial Investigation Work Plan for Soil and Groundwater to IEPA on 4/30/99
  • Updated RI schedule and submitted it in the 4/30/99 Site-Wide RI Work Plan. Table 1 shows status of deliverables.

Completed in 1999:

  • Interim Water Treatment Plant filter upgrade

Completed in 2000:

  • Regrading of the southwest evaporation basin in the Phosphogypsum Stack Area
  • Groundwater sampling for the Phase 1 Remedial Investigation
  • Discharge from Interim Water Treatment Plant diverted to Illinois River
  • Completed stormwater management improvements north and south of Route 29
  • Conducted four rounds of groundwater sampling for the Site-Wide Remedial Investigation

Completed in 2001:

  • Scoping documents for the Presumptive Remedy at the South Ditch
  • Closure work for the Phosphogypsum Stack Area

Completed in 2002:

  • IEPA preparation of the Proposed Plan for the South Ditch
  • Review of Surface Water Flow Patterns Work Plan; first submittal was rejected by IEPA
  • Submittal of Draft Phase 1 RI Report for Soil and Groundwater

Completed in 2003:

  • Ongoing field work in accordance with the Closure Plan for the Phosphogypsum Stack Area
  • Issued Record of Decision for the South Ditch
  • Revised Contaminants of Potential Concern Screening Process

Completed in 2004:

  • Lower Swale Investigation Plan reviewed and work implemented
  • Removed beaver dams from South Ditch
  • Remedial Design/Remedial Action Design for the South Ditch
  • Final Surface Water Flow Patterns Work Plan
  • Ongoing revisions to RI Report Phase 1 Soil and Groundwater
  • Corrective Action Management Unit (CAMU) Investigation Work Plan
  • Proposed Approach for Screening Ecological Contaminants of potential Concern

Completed in 2005:

  • Closure and final grading of the 4th and final pond at the 140-acre Phosphogypsum Stack
  • Completion of the earthwork components of a 2+ acre treatment wetlands to supplement water treatment at the Phosphogypsum Stack
  • Construction of a 2.5-acre Corrective Action Management Unit (CAMU) at the plant site for storage of 8,000 cubic yards of contaminated sediments from the South Ditch Remedial Action
  • First-round assessment of the 17 properties of specific interest from past Illinois Department of Public Health sampling
  • Preliminary drafting of the Off-Site Soils and DePue Lake RI work plans

Completed in 2006:

  • Re-vegetation of the Phosphogypsum Stack, including pilot testing of native prairie grass establishment on approximately 75 acres
  • The completion of the Phosphogypsum Stack treatment wetland
  • Second-round Removal Action Assessment of 6 or 8 private off-site properties that continue to present potential but lower levels of specific interest
  • Phase I Plant Site RI Report
  • Completed DePue Lake (OU5) Floodplain Soil Sampling Technical Memorandum

Completed in 2007:

  • RI sampling of Operable Unit 5 (DePue Lake)(some data gaps were identified)
  • Reseeding of several areas in the Phosphogypsum area to address lack of viable prairie grass cover
  • Repaired erosion problems caused by excessive precipitation in OU 2
  • Constructed test plots at OU2
  • Submitted Phase II RI WP Quality Assurance Project Plan (QAPP) Addendum
  • Inspected and redeveloped OU 3 wells, and issued Technical Memorandum
  • Completed surface water sampling at OU 3
  • Initiated groundwater sampling pursuant to the Phase II RI WP at OU 3
  • Excavated Iron-Rich Material (IRM) Trench test pits at OU 3
  • Completed Phase II RIWP drilling at OU 3
  • Completed background soil sampling at OU 4
  • Completed RI Sediment Sampling Technical Memorandum for OU 5
  • Completed DePue Lake (OU5) Biological Sampling Technical Memorandum

Completed in 2008:

  • Completed Phase III Work Plan for OU 2
  • Conducted well pumping tests in OU 3 monitoring wells
  • Completed Background Soil Sampling Report for OU 4
  • Completed Phase II RI WP test pits along the southern property boundary of OU 3

Completed in 2009:

  • DePue Lake RI
  • Installation of 11 additional groundwater monitoring wells
  • Planting of a native shrub hedge around the Phosphogypsum Stack wetland as an alternative to traditional chain-link fencing
  • Processed 24 million gallons of groundwater through the interim water treatment plant and removed 229,000 pounds of zinc, copper and manganese

Completed in 2010:

  • Finalized the Removal Action Level Assessment Report for off-site soils (OU 4)
  • Conducted a controlled burn of the prairie established on the Phosphogypsum Stack
  • Conducted a 5-Year Review of the South Ditch (OU 1) remedy
  • Sampled the railroad right-of-way to investigate impacts of previous discharges from the former Lithopone Plant
  • Completed the Phase III Groundwater Investigation Work Plan for OU 3 and installed 14 wells in eight locations between the former plant site and DePue Lake, to determine extent of potential groundwater contamination
  • Completed two quarters of sampling (of four scheduled quarterly sampling events) of the Phase III Groundwater Investigation wells for OU 3
  • Initiated work on the DePue Lake Human Health Risk Assessment
  • Initiated work on the DePue Lake Ecological Risk Assessment
  • Implemented IRM Trench evaluation in accordance with Phase II RI WP
  • Initiated Geotube Pilot Study at the interim water treatment plant
  • Collected samples to fill data gaps in the DePue Lake RI.
  • Completed field sampling for the Phase III Phosphogypsum Stack extent of groundwater contamination study
  • Conducted a public meeting for re-establishment of the Citizens’ Advisory Group (CAG)

Completed in 2011:

  • Completed DePue Lake (OU5) Floodplain Supplemental Soil Sampling Technical Memorandum
  • Issued Fact Sheet #14
  • Finalized Removal Action Limit Assessment Report for OU4, off-site soils
  • Installed additional wells associated with phosphogypsum stack to determine extent of contamination
  • Conducted test pits at the six-acre municipal dump area near the South Ditch

Completed in 2012:

  • Completed groundwater sampling activities associated with phosphogypsum stack and submitted Comprehensive Hydrogeological Report
  • Submitted Remedial Investigation Report for OU3
  • Submitted Design Study for OU4

Future Remedial Acitvities

  • Complete the Lake DePue Human Health and Ecological Risk Assessments and initiate the Feasibility Study
  • Complete sampling and remediation of Operable Unit 4, off-site soils
  • Complete the remedial investigation for OU3, former plant area, and initiate a Feasibility Study or Design Study

Reuse Efforts

The Village of DePue was awarded a grant of services in July 2002 by the U. S. EPA. The purpose of the grant was to assist the community in developing a set of future land use recommendations for the DePue/New Jersey Zinc/Mobil Chemical Superfund site. The consultant team guiding this process was E2 Inc. who, after meeting twice with Village officials and residents, released a project report in August 2004 with the following recommendations:

  • Adapt the former New Jersey Zinc plant facility as a museum of history and industry that showcases DePue’s natural and industrial heritage
  • Promote DePue as a tourist destination and emphasize ecotourism
  • Create recreational opportunities at the site and link the site to regional recreational amenities
  • Provide opportunities for ecological restoration, wildlife habitat enhancements and general environmental education
  • Create new economic opportunities in DePue

The report outlines challenges to site reuse and resources that can help DePue reach its redevelopment goals.

Illinois EPA provided a $50,000 Brownfields Grant to the Village of DePue to hire a contractor.

Litigation History

In August 2006, the Village posted Notices to Abate Nuisance at the site. The notices ordered Exxon to remove the materials and clean the site of all contaminants to the satisfaction of the Village within ten days. If Exxon failed to comply within ten days, the notices required Exxon to pay a nuisance fine of $ 750 per day until the site cleanup was complete and the site was removed from the NPL. The notices did not define the terms "materials" or "contaminant". In 2007, the Village of DePue filed a complaint against Exxon in Illinois state court, asserting that Exxon had violated and continued to be in violation of the Village's nuisance ordinance. It sought three forms of relief: a judgment declaring that Exxon had violated the ordinance, daily fines of up to $ 750 for that alleged violation and injunctive relief requiring Exxon immediately to clean the site and have it removed from the NPL. Exxon moved the case to U.S. District Court and filed a motion to dismiss the complaint because the causes of action stated in the complaint were preempted by federal and state law. The district court agreed. In 2008, the Village of DePue appealed the District Court's decision to the U.S. Court of Appeals, 7th Circuit and the District Court's verdict was affirmed because the Village's claims are preempted by Illinois law.

On September 8, 2008, the Village of DePue enacted a new ordinance against hazardous waste, and on November 4, 2008, the Village became a home-rule municipality under the Illinois constitution. The Village filed a new suit in Illinois circuit court, making claims against the PRPs based on the new ordinance. The PRPs moved the case to U.S. District Court, which dismissed the Village's claims because the new ordinance was an invalid exercise of home-rule authority under the Illinois constitution. The Court also dismissed the Village's common law trespass and nuisance claims. The Village filed an amended complaint on July 27, 2009, re-alleging its trespass and nuisance claims under Illinois law. The District Court dismissed this complaint on May 12, 2010. The Village is currently pursuing an appeal.

Current Issues

Illinois EPA restored the information repository at the Selby Township Library by providing the documents on compact disc. The Illinois EPA's site file has been digitized in order to facilitate future responses to Freedom of Information Act requests. Draft documents are being provided to the Village of DePue and the CAG for their review and comment.

Illinois EPA has engaged the Hispanic community of DePue through meetings at St. Mary's Church. Beginning in June 2012, the DePue Citizens Advisory Group (CAG) began holding some of their meetings in the evening. The new meeting time has resulted in more public participation.

Illinois EPA is working with U.S. EPA and the DePue Group to develop remediation processes, including presumptive remedies, for OU3 (Former Plant Site Area) and OU4 (off-site soils) that meet the requirements of the interim consent order, the National Contingency Plan and U.S. EPA guidance.


Charlene Falco
Illinois EPA Project Manager
(217) 785-2891