Editor’s note: Unless attributed otherwise, the information contained in this article was derived from the seven-volume Chemplex Superfund Draft Permit Administrative Record issued in June 2007. The record is available for review at the Clinton Public Library.

This information is being provided as residents prepare for a July 10 meeting at the Camanche Fire Station, where officials will answer questions from residents from 6:30 to 8:30 p.m. Today’s story will focus on remediation at the site, while Saturday’s story will be about the future of the area.

CLINTON — From approximately 1968 to 1978, tetrachloroethylene, also known as perchloroethylene or PCE, was used at the Chemplex polyethylene manufacturing plant and used PCE was disposed of in a landfill at the site.

In 1984, the Chemplex site was identified as a potentially uncontrolled hazardous waste site and proposed for the National Priorities List, a list of the worst hazardous waste sites as identified by Superfund. A 1984 EPA NPL site narrative says the company, along with consultants, conducted testing and discovered that groundwater downgradient of the landfill and the impoundment were contaminated with PCE, styrene, benzene, toluene and polynuclear aromatic hydrocarbons. Chemplex took measures to prevent future releases and began conducting “additional investigations to completely characterize releases from the landfill.” The facility filed a permit application for remediation and received Interim status under the Resource Conservation and Recovery Act.

The EPA NPL narrative states the EPA and the past and present owners of the Chemplex plant signed an Administrative Order on Consent in September of 1987 calling for a Remedial Investigation/Feasibility Study under the Comprehensive Environmental Response, Compensation and Liability Act or CERCLA, also known as “Superfund.” In 1988, the EPA proposed dropping the Chemplex site from the proposed NPL, because the site was subject to the corrective action authorities of the RCRA. In 1990, the EPA and the Potentially Responsible Parties signed a consent decree under CERCLA requiring the PRP’s to construct a system to pump and treat contaminated groundwater. The site was dropped from the NPL list in 1991.

An EPA fact sheet released in May 2006 details that the EPA divided the cleanup activities at the site into two phases, called operable units. Operable Unit 1 addressed groundwater on a site-wide basis and Operable Unit 2 addressed sources of groundwater contamination in the landfill area.

According to a Chemplex Superfund Draft Final Feasibility Study released Nov. 30, 2006 and completed by the science and engineering firm Erler and Kalinowski Inc. on behalf of ACC/GCC, the objectives of the remediation were three-fold including:

• prevent human exposure to volatile organic compounds in groundwater and accessible surface levels greater than a cumulative Hazard Index of 1.0 for non-carcinogenic risks and a cumulative incremental cancer risk exceeding the range of one in 10,000 to one in one million.

• limit exposure by potential ecological receptors in Rock Creek and downgradient surface waters, and

• prevent migration of site-related chemicals to downgradient areas where groundwater is considered to be usable as a potable water supply.

The Record of Decision for OU1 was issued in 1989 and selected to pump-and-treat groundwater at the landfill, as well as a debutanized aromatic concentrate storage area and a truck loading area. The EPA and the PRPs entered into a Consent Decree for OU2 in 1995. OU2 remedial actions included “constructing a low-permeability cover over the Chemplex landfill and performing landfill gas extraction to reduce VOC (volatile organic compound) mass remaining in the landfill material.” The OU2 Statement of Work established requirements for remediation of the soil contamination including the construction of caps or vegetative covers and the posting of warning signs. The caps and covers are inspected annually and repaired as needed. ACC/GCC continues to maintain the low-permeability landfill cover.

The landfill gas extraction system consisted of 55 LGE wells, a collection system for recovering floating product and a catalytic oxidizer for treating the vapor stream from the wells. The system operated from February 1998 to April 2003 and was shut down after all the active wells achieved four years of cumulative operation. During that period, the administrative record asserts the LGE system removed approximately 53,100 pounds of VOCs and about $32,700 pounds of five designated target compounds, including PCE, benzene, tolulene, ethylbenzene and xylene.

The OU1 remedy was intended to contain contaminated groundwater through extraction and treatment. The pump-and-treat system of several extraction and monitoring wells was constructed and became operational in 1994. Today, the system consists of 50 extraction wells. Extracted groundwater is treated in two streams, one designed to contain both polynuclear aromatic hydrocarbons and volatile organic compounds called the base neutral/acid or BNA stream, and the other to treat only VOCs. Both streams are passed through separate air strippers to remove VOCs, but the BNA stream also flows through granular activated carbon to remove PAHs. After treatment, the two streams are “combined and discharged to the Mississippi River through a permitted outfall shared with the neighboring Lyondell polyethylene plant.

In the late 1980s, the presence of PCE in the form of dense non-aqueous phase liquids or DNAPLs was inferred from site monitoring data. In 1991, the Record of Decision was modified by an Explanation of Significant Differences which established a Point of Compliance boundary and an area outside that boundary called the Attainment Area. The objective inside the POC was “removal and containment of chemical mass until these areas would no longer act as a source of groundwater contamination to the Attainment Area.”

Earlier this year, Nancy Swyers, remedial project manager for the United States Environmental Protection Agency Region 7, addressed the Camanche City Council. Swyers explained that DNAPLs do not dissolve rapidly in water and have flowed down into bedrock fractures, making the contamination hard to extract. She said efforts to dig the chemicals out could make the pollution more mobile. According to the Chemplex Superfund Draft Final Feasibility Study released Nov. 30, 2006 and completed by the science and engineering firm Erler and Kalinowski Inc. on behalf of ACC/GCC, “The groundwater extraction system, coupled with naturally downward vertical gradients in certain site areas, appears to pull PCE mass downward where it cannot be effectively recovered.” The draft FFS states that the affected groundwater is traveling through interconnected horizontal and vertical fractures which are “potentially providing a flow path for migrating groundwater” and “additional groundwater extraction will not appreciably accelerate the timeframe for site remediation by mass removal.”

Due to advances in the understanding of site conditions since the pump and treat remedy was implemented at the Chemplex site in the mid-1990s, the EPA began to reevaluate the remediation and look for more effective ways to treat the contamination. In a Five Year Review report of the site released in 2004, the EPA concluded that a plan was needed to address the inability of the current pump and treat system to contain contaminated groundwater in the designated area. The EPA requested that ACC/GCC prepare a Focused Feasibility Study to evaluate potential alternatives to the existing extraction and treatment system.

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