MINNEAPOLIS, Minn. - Progress has been made on the study assessing the possible presence of soil vapors under homes and buildings in the Como neighborhood of Minneapolis, under the oversight of the Minnesota Pollution Control Agency (MPCA).
“We appreciate the cooperation we’ve received from homeowners, and we’re pleased with the initial progress of the testing,” said Tom Forsythe, vice president, Global Communications for General Mills, “though more remains to be done.
“Some homes have been found to have levels above the screening level set by the MPCA, and have already been offered vapor ventilation systems,” Forsythe explained. “Others are below, but more homes remain to be tested."
More than half of the 200 property owners in the testing area have agreed to allow the tests to determine whether trichloroethylene vapor may be present beneath their basement floor or slab. If vapor is present above the screening level set by the MPCA, homeowners will be offered a vapor ventilation system at the expense of General Mills. Such systems, identical to radon mitigation systems, are “a proven solution to radon and vapor intrusion problems,” according to the Minnesota Department of Health (MDH)
Of the approximately 200 properties in the study area, 108 homeowners have completed access agreements to allow the testing. Through today, 85 homes in the area have been sampled.
Results are being shared with homeowners directly, both by phone and by mail, as soon as they are received from the independent laboratory analyzing the sample. To date, 65 samples have been analyzed. All 65 homeowners have received phone calls. Test results are also mailed to homeowners within 24 hours.
So far, 42 homeowners have been offered vapor ventilation systems. Twenty-three homeowners have scheduled design meetings, a step that precedes the system installation, to meet with a licensed contractor who will design and install the vapor ventilation system in their home. Two systems have been installed.
Of the remaining homes tested, 27 homes were below the screening levels set by the MPCA. Fourteen of the 27 tested below 2 micrograms per cubic meter of air, a level at which no further testing is considered necessary by MPCA and MDH. Thirteen homes tested below 20, but above 2 micrograms per cubic meter. All thirteen will be retested. If a second sample confirms the level is below 20 micrograms per cubic meter of air, no further testing would be necessary in those homes, and no vapor ventilation system would be required.
Sixteen test results are awaiting analysis at the independent laboratory, which analyzes samples on a 24-to 48-hour turnaround.
Trichloroethylene, or TCE, is a common industrial solvent and degreaser. It may also be found in household products such as wood finishes, adhesives, paint removers, lubricants, and cleaners.
TCE may be present in the study area in shallow-level groundwater (non-drinking water) as a result of historic waste disposal activities at 2010 East Hennepin Avenue, a site owned by General Mills from approximately 1930 until 1977. Beginning in the 1940s, until the early 1960s, solvents were disposed in a manner customary for the times in an absorption pit located in the southeast corner of the property.
General Mills sold the site in 1977, but the discovery of TCE in the soil at the historic disposal site in the early 1980s led to extensive clean-up activities. The disposal area was excavated and the soil was removed. Extraction and treatment of shallow-level groundwater (non-drinking water) to stabilize and contain the migration of TCE also began in 1985, and continued for 25 years.
Based on extensive groundwater testing over many years, data demonstrated that TCE concentrations had declined to below established cleanup levels for the site. Drinking water supplies were not impacted, and with approval from the MPCA the shallow-level groundwater treatment systems were shut down in September 2010. Soil vapor testing was conducted as part of this process, and in September, 2013, TCE vapors were found in the soil gas in several samples taken on public rights-of-way in the area, prompting this study. General Mills has been addressing and mitigating TCE in the area for more than 30 years, under the oversight of the MPCA, the records of which are and always have been public. The matter has been covered in the media.
The cost of offered vapor ventilation systems would be fully paid for by General Mills, along with the costs of future maintenance. Such systems are a proven solution to radon and vapor intrusion problems, according to the Minnesota Department of Health.
“We are making progress, but there are a number of homes and buildings still to be sampled,” said Forsythe. “We encourage property owners to sign the access agreement to allow a sample to be taken, and we continue to hope that homeowners will allow us to install a vapor ventilation system, if indicated. We want to make this right for any impacted homeowner.”
The company will continue to provide updates as the study progresses.