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As of May 28, 2008, U.S. EPA has collected 268 sub slab samples,219 from residential properties, and 49 from commercial/industrial properties. Fourty-one residential properties had sub slab results over MDH's screening level for PCE and/or TCE. Also, 12 commercial/industrial properties exceeded the MDH's screening levels.
EPA collected indoor air samples at 52 properties; 40 residential, 12 commercial. One residential property owner denied access for the indoor air sampling.
Indoor air sampling results showed exceedances to the MDH's indoor screening level for TCE and/or PCE at 8 residential properties. An additional 3 residential properties exceeded MDH's combined hazard index. Five commercial properties exceeded the MDH's indoor commercial screening levels.
A decision was made to offer a vapor abatement system to all residential properties with sub slab exceedances, regardless of the indoor air sampling results. Installation of vapor mitigation systems at these properties began on March 17, and as of today, 37 systems have been installed, 2 are scheduled for next week, and 1 is pending scheduling.
Abatement system performance sampling began, and as of today 24 properties have been sampled. All properties will be sampled 30 and 90 days after system installation. Of the 24 properties already sampled for the 30 days performance, none showed exceedances to the indoor air screening levels. Two are still showing exceedances to the sub slab screening levels. These 2 properties will be re-evaluated after the 90 days performance sample.
Also, during this reporting period, 5 deep wells were drilled, as part of the ongoing groundwater investigation.
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