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
Source Area 7 Remedial Investigation Results - Southeast Rockford Groundwater Conta... Page 2 of 4
http://www.epa.state.il.us/community-relations/fact-sheets/southeast-rockford/southeast-ro... 5/25/2012
