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Soil vapor investigation preliminary results

What are VOCs?

VOCs are a group of chemicals used in solvents, paints and dry-cleaning fluid. Breathing low levels of VOCs for long periods may cause an increase in health risks.

What is Trichloroethylene (TCE)?

What is PCE? - see tetrachloroethylene (PCE is another name for tetrachloroethylene.)

February 6, 2008

As of February 5, EPA has received signed access agreements from 219 property owners (187 residential, 29 commercial/industrial) for installation of basement sub-slab soil-vapor monitoring probes. Thus far, 216 of these have been installed.

Since January 28, sub-slab samples have been collected at 212 properties (184 residential/29 commercial/industrial). Of these, 40 sub-slab samples (32 residential/8 commercial/industrial) exceeded Minnesota Department of Public Health's screening level for one or more of 15 volatile organic compounds, primarily TCE or PCE. The two chemicals are commonly found in dry cleaning fluids and industrial degreasers. Thus far, EPA has no evidence that VOC soil vapors are reaching the 40 properties with exceedances.

Next Steps: On February 5, EPA began an effort to take indoor air samples at the 40 properties with exceedances. This involves installation of three separate SUMMA canisters in basements and first floors, where the cannisters collect air over a 24-hour period. EPA's TAGA bus mobile laboratory will also draw air samples from the 40 properties. Off-site laboratory analysis of these samples takes approximately one week. If the additional sampling confirms there are high VOC levels reaching indoor air at any of the residential properties, EPA will design and install vapor extraction systems at no cost to residents. If high levels are confirmed at commercial/industrial properties, EPA will consult with any private environmental contractors hired by the property owners.

EPA will post another update in mid-February.

Questions about the project may be directed to


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