Southeast Rockford Groundwater Contamination Superfund Project

Source Area 11
Remedial Investigation Results

Southeast Rockford Groundwater Contamination Superfund Project

February 2001

Rockford, Illinois

Background. Illinois Environmental Protection Agency (Illinois EPA) investigations in 1993 identified Area 11 as one of four major sources of groundwater (water beneath ground surface) contamina-tion in the Southeast Rockford Groundwater Contamination Superfund Project. In 1996, the Illinois EPA conducted more extensive investigations in Area 11 in preparation for developing a remedy for that area.

Summary of Area 11 investigation results. Area 11 is an old industrial area dating back to at least 1906. Past industries include Rockford Varnish, Rockford Coatings Corporation and Rockwell International Graphics. Some of these industries have documented use of chlorinated solvents, the main chemicals of concern for the project area. Past surface spills appear to have been the primary sources of Area 11 surface and subsurface soil as well as groundwater contamination.

Chlorinated industrial solvents found in the remainder of the Southeast Rockford Project were detected in some Area 11 samples at low concentrations. Non-chlorinated solvents, often associated with petroleum products, however, were found in such high concentrations in Area 11 that the detection limit of the analytical equipment had to be raised considerably. There may have been relatively high concentrations of chlorinated solvents in Area 11 samples, but they may not have been detected because of the high detection limit of the analytical equipment.

Illinois EPA soil borings indicate that at least 62 feet of sand and gravel lie underneath Area 11. Illinois State Geological Survey records, from a boring at 9th Street and Harrison Avenue, show sand and gravel extending to approximately 235 feet where bedrock is encountered. In 1993, the water table was between 20 and 25 feet beneath ground surface. In 1996, it was between 30 and 34 feet beneath ground surface. Groundwater is flowing to the northwest.

Chemicals detected in Area 11. Sample results indicate that the main contaminants detected in Area 11 are acetone and chemicals found in petroleum products--primarily ethyl benzene, toluene and xylene (ETX). Chlorinated solvents (the main chemicals of concern in the remainder of the project area) and ETX are classified as volatile organic compounds (VOCs). "Volatile" means the compounds vaporize (evaporate) readily and "organic" means they contain carbon. Results for different media (soil, groundwater, etc.) are summarized below.

Surface soil

Illinois EPA sample results did not show VOCs in the surface soil samples. Low levels of semi-volatile organic compounds were found in all seven surface soil samples collected in Area 11. The detected compounds are often associated with the burning of coal, gas and oil, as well as automobile exhaust and tobacco smoke. The pesticide dieldrin was also detected at low levels. The levels of the semi-volatiles and dieldrin meet guidelines protective of those who visit the site occasionally but exceed guidelines protective for residential use.

Subsurface soil

Investigations identified two distinct zones of subsurface contamination in Area 11. See above map. One zone is located in the western part of Area 11 beneath the building now occupied by Rohr Manufacturing. This zone also extends north and south of the building. The primary chemicals detected in this zone are acetone, toluene, ethyl benzene and xylene. The thickness of non-chlorinated VOC contamination in the western zone is between 12 to 24 feet. A second zone is near the above ground storage tanks close to the former Rockford Varnish building. The contamination in this second zone begins approximately 35 feet below ground surface and is estimated to extend approximately 10 feet. This zone includes high levels of toluene and xylene.

Non-aqueous phase liquids (free product)

Chemicals in water that are present in high enough concentrations to be undissolved in the water are called free product or non-aqueous phase liquid (NAPL). Chemicals that are heavier than water will sink to the bottom of the water table and are called dense NAPL or DNAPL. Chemicals, such as toluene, that are lighter than water will float on the water table and are called light NAPL or LNAPL. Soil samples in the western part of Area 11 between 39 and 43 feet below ground surface confirmed the LNAPL form of toluene, ethyl benzene and xylene in the upper portions of the water table. Samples from the zone beneath the above ground storage tanks also indicate, but do not positively confirm, the presence of LNAPL of the same compounds floating on top of the water table. Samples indicate that DNAPL is unlikely in either zone.

Soil Gas

Illinois EPA soil gas (vapors in air pockets beneath ground surface) sample results were similar to results from soil samples in the two zones of contamination in Area 11; that is, the concentrations of toluene, ethyl benzene and xylene were higher than the concentrations of chlorinated solvents. One notable exception was one soil gas sample taken on the southeast corner of the building now occupied by Rohr Manufacturing. This sample showed high levels of chlorinated solvents (1.049 parts per million). No indoor air analysis was performed in Area 11 because of the industrial nature of the area and the fact that there are no homes close by.

Groundwater

Samples from monitoring well IW10 (see map on page 1) showed 310,000 parts per billion (ppb) toluene. Monitoring well IW11 had 860 ppb 1,1,1-trichloroethane, 140,000 ppb toluene, 1,800 ppb ethyl benzene, and 8,000 ppb xylene. Toluene, ethyl benzene and xylene are predicted to degrade before or shortly after leaving Area 11 to the point where they meet federal drinking water standards. The Illinois EPA is proposing to install four additional monitoring wells in Area 11 to check this prediction. People with homes connected to the Rockford Public Water Supply do not have to worry about contamination of their drinking water. The Rockford Public Water Supply is regularly checked for potential contamination. Water that does not meet U.S. Environmental Protection Agency (U.S. EPA) drinking water standards is not distributed to the public.

Next Steps. The Illinois EPA and U. S. EPA have proposed a plan to remedy Area 11 as well as the other three major sources of contamination for this project. For more information on all the remedies studied for Area 11as well as the proposed plan for Area 11, see the enclosed feasibility study/proposed plan fact sheet.

For More Information:

Contacts: For more information about the project including fact sheets on the remedial investigation results, feasibility studies and proposed plans for each of the four major source areas, you may contact the Illinois EPA staff listed below:

Repositories: Full reports for the project may be reviewed at the following locations.

Administrative record file: The administrative record file is located at the Illinois EPA headquarters in Springfield, Illinois. Call 217-782-9878 for an appointment. The administrative record file will also be located on microfiche at the Main Branch of the Rockford Public Library at 215 N. Wyman in Rockford.