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Groundwater testing to begin next week in Algona

Dave Hill - Courtesy photo
Dave Hill
— image credit: Courtesy photo

Vapor intrusion testing is expected to start next week on most of the first homes in northern Algona whose owners had agreed to groundwater testing to determine if pollution is releasing vapors that could rise through the soil and into their homes.

Owners of selected homes in northern Algona received letters in June from the Washington Department Ecology and information inviting them to participate.

The DOE is directing the work and The Boeing Co. is carrying it out and paying for it.

It's all part of an ongoing investigation into an area of groundwater contamination that started on property owned by The Boeing Company in Auburn.

Some of the 23 homes initially selected aren't being tested, according to Algona Mayor Dave Hill.

"One homeowner has refused the testing, and several have not yet responded," Hill said in a release. "Some homes that completed the initial survey have not returned the release, so they are not scheduled at this time to receive the testing. Many of the homeowners changed the release form, which caused an additional delay while Boeing reviewed and accepted the changes."

Several weeks will pass from the time of the VI test before the homeowner receives a letter reporting the results of the test.

Investigators hope to determine the location, size and impacts of the underground contamination – primarily trichloroethene (TCE) and vinyl chloride (VC) – caused by past releases of solvent chemicals.

TCE and VC in groundwater at the water table can release small amounts of vapor into the soil. The vapors rise toward the ground surface through gaps between soil particles in concentrations that normally produce no noticeable odor.

Soil vapors that reach building foundations may pass from soil into interior building spaces under certain conditions, and can accumulate in indoor air or other enclosed areas, such as crawl spaces. This process is called vapor intrusion. TCE or VC vapors, in high enough concentrations over time, can place people at risk for cancer and other illnesses.

Whether the vapors enter the building – and if they do, how much they affect indoor air quality – depends on several factors, among them how contaminated the groundwater is at the water table, soil conditions above the water table, the type of foundation a building has – slab, crawl space or basement – and the structure's ventilation.

According to DOE spokesman Larry Altose, a related study in parts of Algona collected samples of underground water at 49 locations as part of the effort to map the contaminated area. Sampling data showed the presence of solvent chemicals at the water table at 14 locations in an area just west of Chicago Avenue, between Boundary Boulevard and Ninth Avenue North. The concentrations of TCE and VC at the water table in this area could be enough to release vapors into the soil.

Because of this, Altose said, the DOE has directed Boeing to sample indoor air at homes in this area.

One other location – along Junction Boulevard, south of 9th Avenue – showed the chemicals to be present 25 feet below the ground, too deep, Altose said, to impact indoor air.

Samples from the study's 34 remaining sites showed no detection of TCE or VC.

Ecology may select additional buildings for evaluation based on findings from the first set of buildings and on further evaluation of underground water study results in Algona.

Ecology and the Washington Department of Health will review all indoor air sampling results. If the two agencies determine that vapor intrusion from the contaminated groundwater is causing potentially harmful levels of TCE or VC in indoor air, Ecology will direct Boeing to propose to any affected property owner an "interim action" to achieve acceptable indoor air levels as quickly as possible. Such measures would continue to operate until follow-up monitoring ensures that vapor intrusion no longer takes place.

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