The former Ameren Central Illinois Public Service Superfund Site is located at 917 South Webster Street in Taylorville, Illinois. The Site is approximately 1.2 acres in size and along with two adjacent parcels also owned by Ameren make up an area of approximately 20.8 acres. The three parcels are subject to an Environmental Covenant (EC) with the Illinois EPA, restricting disturbance of soil and use of groundwater for potable purposes within the EC Area. The Site lies in a residential area adjacent to Manners Park. The site was designated as a "State-lead" enforcement case with Illinois EPA as the lead agency and United States Environmental Protection Agency (USEPA) Region 5 as support agency.
The former manufactured gas plant (MGP) was constructed in 1892 and was operated by the Taylorville Gas and Electric Company until it was purchased in 1912 by Ameren predecessor companies. Ameren predecessors operated the MGP from 1912 until 1932. The plant produced a low-quality gas from coal, which was used for lighting and heating. When the plant was closed, most of the above ground structures were torn down. Below ground tanks reportedly were filled with soil and miscellaneous materials and left in place. Groundwater at the Site was contaminated with polynuclear aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). The contaminants of concern (COCs) identified in groundwater include PAHs (8676 µg/L), benzene (4500 µg/L), toluene (7000 µg/L), ethyl benzene (680 µg/L), and total xylenes (5000 µg/L).
Various response actions were completed at the site, such as demolition and removal of all former MGP structures above and below ground, excavation, and offsite disposal of approximately 12,000 cubic yards of contaminated soil and sediments in the drainage swale; and backfilling of affected areas with clean soils. A pump and treat (P&T) system to address contaminated groundwater has been active on the site since 1995. In an effort to accelerate remediation, In-Situ Chemical Oxidation (ISCO) was applied to source materials in 2006-2007 and 2010-2012.
The Site is currently located within a fenced parcel owned by Ameren. The other areas of the parcel are utilized for the P&T facility and storage of remediation support materials. There is also an area of the parcel that consists of a former laydown yard for Ameren Illinois. There are currently no employees at the Site other than those that visit the Site to conduct sampling and/or maintenance of the wells and associated P&T system structures. It is anticipated that once fully remediated, the property can be redeveloped.
The Illinois EPA and Ameren are considering remedial alternatives to finish cleanup of the site and achieve Remedial Action Objectives. The existing P&T system, while effectively removing most of the groundwater contamination, would take an estimated 100 years or longer to meet the Illinois Groundwater Quality Standards. For this reason, the Illinois EPA is proposing additional remedial action to render the site usable in a more reasonable timeframe. The current preferred remedial alternative, pending public comment, is in situ solidification and stabilization (ISS).
For this alternative, the P&T system, including monitoring and extraction wells and associated piping, will be permanently removed so ISS can be implemented. For ISS, a slurry mixture of binding agents is developed and mixed with subsurface soil using large diameter augers. The mixture then cures and hardens in situ to form a stabilized, monolithic subsurface structure. Stabilization can also include mixing contaminated soil with other binding agents, which are intended to cause a chemical reaction with COCs to make them less likely to be released to the surrounding environment. The actual reagents to be utilized will be determined through a treatability study, which will evaluate various reagents in soil from the Site in a laboratory. The findings of the treatability study will support development of a Remedial Design to be reviewed and approved by Illinois EPA. After ISS is complete, the top 10 feet of ISS-mixed materials within the treated area will be excavated, properly disposed, and backfilled. Environmental monitoring to ensure protection of the public will occur during remedy implementation. Restoration of the disturbed area will include final grading, followed by application of grass seed. Administrative controls will be used to ensure the integrity of the remedy by prohibiting at depth disturbance of soils in the area of and immediately around the monolith.
For more information on the multiple alternatives considered, see the Focused Feasibility Study.
For more details on the specific rationale for selection of ISS see the Proposed Plan.
Illinois EPA encourages the public to review the Proposed Plan and the documents that make up the Administrative Record to gain a more comprehensive understanding of the Site and remediation activities that have been conducted. The Proposed Plan and Administrative Record for the Site can be accessed at the following location:
Taylorville Public Library
121 West Vine Street
Taylorville, IL 62568
Phone: (217) 824-4736
Illinois EPA maintains an Information Repository for the Site, which includes the full Site record. The Information Repository is available online at: