Southeast Rockford Groundwater Contamination Superfund Project

Source Area 7
Remedial Investigation Results

Southeast Rockford Groundwater Contamination Superfund Project

February 2001

Rockford, Illinois

Background. Illinois Environmental Protection Agency (Illinois EPA) investigations beginning in 1991 identified Area 7 as one of four major sources of groundwater (water beneath ground surface) contamination in the Southeast Rockford Groundwater Contamination Superfund project. In 1996, Illinois EPA conducted more extensive environmental investigations in the four major source areas in preparation for developing remedies for each of the areas.

Summary of Source Area 7 investigation results. Area 7 is a former unregulated disposal area evidently used for both household and industrial waste. Early aerial photographs of Area 7 show evidence of waste disposal and excavation from 1959 through 1970. The area, located north of Balsam Lane in Rockford, now contains a field, wooded areas and Ekberg Park. The depth of contamination varies from four feet below ground surface to at least 29 feet. Illinois EPA estimates that there are approximately 265,000 cubic yards of highly contaminated soil beneath the ground surface.

Illinois EPA soil borings show sands, silts and clay to bedrock. Bedrock varies between 35 and 135 feet below ground surface. The water table varies from 36 feet below ground surface south of the park, to 13 feet in the park and 2 feet near the creek. The groundwater flows to the northwest.

How was the area discovered? In 1991, Illinois EPA installed a monitoring well in Area 7 as part of a study to determine the source of private well contamination west of 20th Street. At the time of installation, it was thought that the Area 7 well was probably a "background" well. A background well is one installed in an uncontaminated area to be used for comparison to wells in contaminated areas. Groundwater samples in 1991, however, showed that the Area 7 well contained high levels of the same contaminants found in the private wells west of 20th Street. The Illinois EPA investigations since 1991 have confirmed that the area is a major source of groundwater contamination.

The main chemicals of concern. The main chemicals of concern in Area 7 are industrial solvents. The solvents are in a class of chemicals called volatile organic compounds (VOCs). They are called volatile because they vaporize (evaporate) rapidly and organic because they contain carbon. Chemicals of concern include 1,1,1-trichloroethane (TCA), trichloroethylene (TCE), perchloroethylene (PCE) and xylene. These chemicals are often found at lower concentrations in household products such as glues and solvents. Xylene and other compounds detected in Area 7 are also associated with petroleum products. Results for different media (soil, groundwater, etc.) are summarized below.

Surface Soil

No contaminants were detected at levels of concern in surface samples (0 to 6 inches). At 6 to 12 inches, there were samples that exceeded screening levels for VOCs, two semi-volatiles and two metals. The Illinois EPA evaluation determined that none of these samples, however, had contaminants present at levels of concern for people using the park.

Subsurface Soil

Illinois EPA sample results showed three subsurface soil "hot spots" as shown on the map on page 1. The VOCs found most often were TCA, PCE and TCE. These chemicals and others were found at concentrations substantially higher than cleanup objectives proposed for the area.

South of the basketball court. Illinois EPA samples south of the basketball court showed elevated levels between four and 28 feet beneath ground surface. A sample four feet beneath ground surface had 441 parts per million (ppm) total VOCs. A sample 15 feet beneath ground surface showed 1,019 ppm total VOCs, and a sample 20 feet below ground surface had 357 ppm total VOCs.

North of the playground. Tests in this area showed significant contamination from 3 to at least 28 feet below ground surface. Testing was not performed below 28 feet because of the risk of spreading the contamination deeper into the groundwater. Illinois EPA samples showed 627 ppm total VOCs at 4 feet below ground surface, 17 ppm at 11 feet below ground surface and 875 ppm at 25 feet below ground surface.

West of the tennis court. Illinois EPA samples showed 35 ppm total VOCs 20 feet below ground surface. Notable contamination was found between 19 to 23 feet below ground surface.

Test Pits

In June 1993, three test pits (large holes dug for investigation purposes) were excavated in Area 7 to a depth of 15 feet. The test pits revealed metal cans, glass bottles and miscellaneous trash. Soil samples showed PCE up to 22 ppm, TCA up to 4 ppm and TCE up to 3 ppm.

Groundwater

Illinois EPA sample results showed high levels of solvents in the groundwater with TCA up to 8,000 parts per billion (ppb). The drinking water standard for TCA is 200 ppb. Area residents who are using Rockford Public Water Supply, however, do not have to worry about the safety of their drinking water, because the Rockford Water Supply is regularly tested for possible contaminants. Water that violates U.S. Environmental Protection Agency (U.S. EPA) drinking water standards is not distributed to the public.

Non-Aqueous Phase Liquid (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). NAPL is of special concern, because it is concentrated and continually releases contaminants into the groundwater and into the air pockets in the soil above the groundwater. Chemicals, such as PCE, that are heavier than water will sink to the bottom of the water table and are called dense NAPL or DNAPL. Chemicals, such as xylene, that are lighter than water will float on water table and are called light NAPL or LNAPL.

Illinois EPA sample results indicate that there may be DNAPL in the area south of the basketball court. Other volatiles, which are lighter than water such as xylene, were also found in high concentrations in this area and may be floating on top of the water table (LNAPL). Sample results also indicate DNAPL is present in the area by the playground.

Soil Gas

Since VOCs evaporate (vaporize) readily, vapors from subsurface contamination can accumulate in the air pockets between soil particles beneath ground surface. The air and vapors found in these air pockets are called soil gas. In 1992, 1993 and 1996, the Illinois EPA conducted soil gas surveys of Area 7 by driving probes into the ground, withdrawing the air that accumulated in the air pockets (soil gas) and analyzing the air for VOCs. Results showed high levels of three VOCs in soil gas north of the playground and south of the basketball court. The three VOCs were TCA, PCE and TCE-all of which are industrial solvents.

The Illinois Department of Public Health (IDPH) evaluated air samples taken above ground in the park and concluded that VOCs detected in the above ground outdoor air were similar to levels found in an average urban community and were not a concern for people using the park.

The IDPH and the Illinois EPA tested the basement air in several homes around Area 7 in 1992 and 1993. IDPH concluded that the concentrations detected in basements near Area 7 were below levels of health concern. Since many of these chemicals are found in household products such as paints and glue, the source of detected levels could not be determined.

The U.S. EPA and Illinois EPA plan to repeat sampling of several homes near Area 7 during the design phase of the remedy-probably in 2001. These tests will make sure that levels have not increased and will provide data for U.S. EPA to compare to guidelines they are currently using.

Creek Sediments and Water

In 1996 and 1998, Illinois EPA collected surface water and sediment samples from an unnamed creek at the north end of Area 7.

The surface water samples showed low concentrations of VOCs at levels below U.S. EPA drinking water standards. Lead and antimony concentrations slightly exceeded concentrations set to protect people over a lifetime of exposure, drinking two liters of water every day. Lead and antimony are not among the main contaminants of concern in other parts of Area 7.

Sediment samples contained one VOC, 1,2-dichloropropane, which is not a common VOC found in other parts of Area 7. Sediment samples also contained semi-volatiles (such as fluoranthene, pyrene, benzo (a) anthracene, chrysene) that are often found in petroleum products but are not the main chemicals of concern in other parts of Area 7.

The Illinois EPA and U.S. EPA determined that it would be more efficient to further evaluate the creek running north of Area 7 during the design phase of the project. The design phase will likely occur in 2001. If that investigation identifies the need for remediation in addition to that outlined within the plan currently being proposed, the remedy would be appropriately altered. The public will be notified of this alteration. Depending upon the significance of the change in remedy, the agencies may be required to hold additional public meetings and allow public comment on the additional remedy.

Next Steps. The Illinois EPA and U. S. EPA have proposed a plan to remedy Area 7 as well as the other three major sources of contamination for this project. For more information on all the remedies studied for Area 7 and the Area 7 proposed plan, see the enclosed feasibility study/proposed plan fact sheet. You may also obtain more information from sources listed below.

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.