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Fact Sheet 9c

Source Area 9/10

Remedial Investigation Results

Southeast Rockford Groundwater Contamination Superfund Project

February 2001

Rockford, Illinois

Background. Illinois Environmental Protection Agency (Illinois EPA) investigations have identified Area 9/10 as one of four major sources of groundwater (water beneath ground surface) contamination in the Southeast Rockford Groundwater Contamination Superfund project. The main chemicals of concern are industrial solvents that contaminated drinking water wells. The Illinois EPA conducted limited environmental investigations in Area 9/10 beginning in 1993, with fieldwork concluding in 1996. Because of restricted access, however, the Illinois EPA was not able to fully investigate Area 9/10.

Area 9/10 summary description. Area 9/10 has a history of industrial activity extending back at least to 1926 when the Rockford Milling Machine and Rockford Tool companies merged to become the Sundstrand Machine Tool Company. Other industries also have located in the area since that time.

Illinois State Geological Survey records show that sand and gravel extend to approximately 235 feet below ground surface where bedrock is encountered. The water table generally is encountered between 30 and 35 feet below ground surface. Much of Area 9/10 is covered by concrete or asphalt pavement. In Source Areas 4, 7 and 11, the groundwater flows generally to the northwest, but it changes direction east of Area 9/10 and flows to the southwest.

The main contaminants of concern. In Area 9/10, the main contaminants of concern are chlorinated compounds used as industrial solvents and related compounds. These chemicals include trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), perchloroethylene (PCE), 1,2-dichloroethylene, 1,1-dichloroethane and vinyl chloride. Chemicals associated with petroleum products such as benzene, ethylbenzene, toluene and xylene were also detected in small to moderate amounts. All of these chemicals are classified as volatile organic compounds (VOCs). They are called "volatile" because they vaporize (evaporate) readily and "organic" because they contain carbon. Results for different media (soil, groundwater, etc.) are summarized below.

Surface soil. Of the four Illinois EPA surface soil samples (0 to 6 inches) collected in Area 9/10, none showed chlorinated solvents. Low levels of semi-volatile compounds were found in three of the samples. These 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 in two of the samples. The concentrations of the semi-volatiles and dieldrin meet guidelines protective of those who only visit the site occasionally but exceed guidelines protective of someone living on the site.

Subsurface soil. According to available data, the highest level of contamination is suspected of being near and/or under the Hamilton Sundstrand facility. Because of limited access, however, the Illinois EPA was not able to conduct soil borings at these locations. The samples that Illinois EPA was able to collect show low levels of VOCs.

Soil gas. Since VOCs vaporize readily, vapors from subsurface contamination can accumulate in the air pockets between soil particles beneath the ground. The air and vapors found in these air pockets are called soil gas. Results of Illinois Area 9/10 soil gas sample analyses identified the following areas with distinctly high soil gas concentrations:

  • west and northwest of the Hamilton Sundstrand plant (the southeast corner of 23rd Avenue and 9th Street),

  • immediately south of the Hamilton Sundstrand plant and in the Rockford Products parking lot,

  • immediately north of the Rockford Products building on 9th Street,

  • the west end of the Nylint building

  • the Mid-states Industrial facility and

  • the intersection of 9th Street and Harrison Avenue

Soil borings in the six soil gas survey areas listed above did not confirm high concentrations of VOCs in soil. There are two possible explanations for this lack of correlation: (1) Soil gas is migrating from nearby contaminated soil that was not sampled; and/or (2) soil gas is migrating from contaminated groundwater beneath soil gas survey areas.

No indoor air analysis was performed in Area 9/10, because the area is mostly industrial and the homes that are near Area 9/10 appear to be outside of significant areas of groundwater contamination.

Groundwater. In Area 9/10, groundwater is flowing to the southwest. The results shown in the table below show concentrations in wells downgradient of Area 9/10 more than 1,000 times greater than concentrations in upgradient wells. Water flows from upgradient to downgradient so monitoring wells 202 and 203 are upgradient and monitoring well 201 is downgradient. See map on page 1 for monitoring well locations.

Upgradient Downgradient
MW 202 17 ppb MW 4 43 ppb MW 201 18,278 ppb
MW 203 9 ppb MW 5 28 ppb  
ppb =parts per billion. See map above for location of monitoring wells.

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 possible contamination. Water that does not meet 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 contamination is concentrated and continually releases chemicals into the groundwater and into the air pockets in the soil above the groundwater. The concentration of 12,000 ppb TCA in monitoring well 201 indicates that NAPL is probably present in Area 9/10 subsurface soils. The TCA drinking water standard is 200 ppb.

Next Steps. The Illinois EPA and U. S. EPA have proposed a plan to remedy Area 9/10 as well as the other three major sources of contamination for this project. For more information on all the studied remedies for Area 9/10 as well as the Area 9/10 proposed plan, see the enclosed Area 9/10 feasibility study/proposed plan fact sheet. You may also obtain more information on the entire project 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:

Tammy Mitchell

Community Relations Coord.

Illinois EPA

1021 N. Grand Ave. E.

Box 19276

Springfield, Illinois 62794-9276

Phone: (217) 524-2292
Thomas Williams

Project Manager

Illinois EPA

1021 N. Grand Ave. E.

Box 19276

Springfield, Illinois 62794-9276

Phone: (815) 223-1714

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

Rock River Branch

Rockford Public Library

3128 S. 11 th Street

Rockford, IL 61109


(Call for hours)
Ken-Rock Community Center

3218 S. 11th Street

Rockford, IL 61109


(Call for hours)

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.