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Fact Sheet 14

Fact Sheet #14

February 2011

Bureau County, DePue, Illinois


The purpose of this fact sheet is to update the residents of DePue and other interested parties about activities associated with the New Jersey Zinc/Mobil Chemical Superfund site (Site) to answer questions and clarify statements that have recently been circulating about the Site. Charged as the responsible regulatory agency, the Illinois EPA works to maintain an open and transparent dialogue with all stakeholders while ensuring the site is remediated and managed under applicable state and federal laws and regulations.

Frequently Asked Questions

I’ve heard there is a new citizens’ group in DePue pertaining to the Site?

Yes, The Illinois EPA held an informational Community Advisory Group (CAG) meeting on November 17, 2010. A CAG serves as a public forum that allows citizens of a community to discuss their needs and concerns relating to the Superfund decision making process. This provides the community a voice in the Superfund process. A CAG committee has been established and they have elected their officers. The CAG Leadership indicated that they would meet again sometime in early 2011, however, no meeting date has been set at this time.

Because of the complexity of the site, the Illinois EPA organized the site into five Operable Units (OU’s):

  1. OU1 – The South Ditch Sediment
  2. OU2 – The Phosphogypsum Stack
  3. OU3 – The Former Plant Site Area (FPSA)
  4. OU4 – Off-Site Soils
  5. OU5 – DePue Lake Sediments and Floodplain

This is the second CAG formed for this site. The first CAG operated from 1997 to 2002 and was terminated at the request of the CAG members.

Has the remediation schedule for the DePue site been updated?

As new information becomes available, schedules are updated to reflect the progress that has been made and challenges that have arisen. The master site schedule was last published in the summer of 2009. Since that time, significant additional data have been collected, including: results from the railroad right-of-way to assess impacts from the former lithopone plant, results from the groundwater investigation in the former plant site area; and results from the DePue Lake human health and ecological risk assessments.

Activities anticipated for 2011 include:

  • Completion of the DePue Lake human health and ecological risk assessments and start the feasibility study for DePue Lake
  • Complete and evaluate the hydrogeologic study for the phosphogypsum stack
  • Evaluate future surface use options for the phosphogypsum stack
  • Begin the remedial investigation for off-site soils
  • Submit the draft Phase 2 Remedial Investigation (RI) groundwater report for the former plant site

The master site schedule is being updated and will be available in the near future.

Is this Site really the 14th worst Superfund site in the U.S.?

Illinois EPA agrees this Site is one of the most complex Superfund sites in Illinois, but does not consider it the most contaminated. For example, other Illinois Superfund sites have more toxic chemicals, and other Illinois Superfund sites have caused contamination of community drinking water supplies.

The Site is not ranked as the 14th worst Superfund site in the U.S. It appears that the “14th worst” claim is based on someone’s inappropriate evaluation of the hazard ranking score USEPA uses to determine if a site is eligible for the National Priorities List (NPL or Superfund). The purpose of the hazard ranking assessment process is to determine if a site qualifies for listing on the NPL. Sites with scores greater than 28.5 qualify for being listed on the NPL. USEPA does not use the scores to rank sites relative to each other and does not designate sites as “the worst, second worst, third worst, etc.” because that would be an improper use of the score. The Hazard Ranking System (HRS) score is often prepared before very much is known about the site. Scores are not necessarily based on the same quantity and quality of data, and cannot be directly compared to each other.

Why is the DePue Group allowed to manage the contamination rather than to remove it?

Containment of wastes in place is a standard remediation strategy for low toxicity, high volume wastes, such as the primary zinc slag pile. Unless there is a very compelling health or environmental reason for removing the waste from where it is located, it is less disruptive to contain the waste at the site than to move it to another location. Illinois’ existing landfill capacity would not easily accommodate the 750,000 tons of primary zinc slag that are estimated to be present at the Site and the act of trucking it to another location would create additional safety risks. In order for wastes to be considered for on-site containment, proper investigations and engineering design must first be conducted so the final remediation is protective.

Are metals, from the Site, the reason people say we shouldn’t eat the fish from DePue Lake?

No. The 2011 fish advisory for DePue Lake cautions people to limit their consumption of carp, white bass and channel catfish due to the presence of polychlorinated biphenyls (PCBs) in the fish and mercury in predatory fish. The Illinois River also has a fish advisory for these same species for the same reasons. Fish advisories are based on fish sampled for 14 chemicals, including pesticides, mercury (in predator fish only) and PCBs. DePue Lake’s first fish advisory was in 2006, and an advisory has been issued every year since then. In 2010, white bass were added to the advisory. The Site is not believed to be a significant contributor of these contaminants that have resulted in the fish advisories in DePue Lake.

While metals are not on the list of the 14 chemicals that the Illinois Department of Public Health analyzes as part of its Fish Advisory Program, fish from DePue Lake were analyzed for metals as part of the Lake Remedial Investigation in 2008. The type of fish analyzed were those that people are most likely to eat: freshwater drum, bluegill, bullhead, carp, and catfish. While several metals were detected in fish tissues, none were at levels that posed a risk to adults or children.

For more information on the fish advisories, go to, or contact IDPH at (217) 782-5830.

Why is DePue Lake filling with silt?

DePue Lake is an oxbow lake created by a channel change in the Illinois River. Over time, oxbow lakes become shallower due to deposition of sediment from the surrounding area and from the river.

Historical survey data indicate an overall rate of siltation of DePue Lake of roughly 2-3 centimeters (cm) or one inch per year (ISWS/ISGS 2002) with deeper portions of the lake silting in more rapidly, up to 8 cm/year (about 3 inches/year). A more recent study conducted on behalf of the DePue Group indicates an overall sedimentation rate of 0.89 inch/year (Arcadis 2009). In some areas of the lake, sediments have accumulated to a thickness of 10 feet. As a former oxbow, DePue Lake has a finite life expectancy and will continue to silt in and eventually become part of the floodplain, as do all oxbow lakes.

For more information on oxbow lakes, refer to the following websites:

Will the DePue Group dredge DePue Lake?

The DePue Group is legally responsible only for contamination emanating from the Site. When a remedy is selected for contaminated lake sediment, the remedial action will address only the levels of contamination deemed unacceptable for exposure to soil, sediment and surface water by people, plants or animals. Dredging this contaminated sediment is one possible way to address the contamination. However, other technological options may be available.

Why does the Interim Water Treatment Plant flood and dump contaminated water into DePue Lake?

Treated effluent from the Interim Water Treatment Plant discharges to the Illinois River, not to DePue Lake. On occasion in the past, extremely heavy precipitation events have caused flooding of the lift station and the bypass of water around the Interim Water Treatment Plant and discharge to DePue Lake. This happened a few times a year until the surface water controls along the bluff line were installed in 1998. Since then, there have been only a few bypass events which were caused by the record and near-record river stages during September and December 2008, and March 2009. These events are related to extreme conditions and rarely occur.

According to a petition that is circulating in the DePue community and surrounding areas, the 1995 Interim Consent Order requires removal of the slag pile. Is that accurate?

No. The Interim Consent Order requires the DePue Group to conduct a focused Remedial Investigation for the Primary Zinc Slag Pile. Following that, the DePue Group will have the option of proceeding with a Feasibility Study or submitting a Conceptual Presumptive Remedy Document and a later Design Study, which would define parameters for in-place closure of the Primary Zinc Slag Pile.

Who is the State’s new project manager for the Site?

The Illinois EPA has designated Charlene Falco as the new project manager for Site. Ms. Falco will be managing the project from Illinois EPA’s Springfield office, where she has worked for almost 20 years.

For more information, you may contact:

Jay A. Timm

Community Relations Coord.

Office of Community Relations

Illinois EPA

(217) 557-4972
Charlene Falco

Project Manager

Illinois EPA

(217) 785-2891