Washington State Department of Ecology - May 31, 2013
BELLEVUE – Owners of selected homes in northern Algona received letters this week inviting them to participate in an upcoming study to investigate whether groundwater pollution is releasing vapors that may rise through the soil and enter homes. The work is part of an ongoing investigation into an area of groundwater contamination that originates on property owned by The Boeing Company (Boeing) in Auburn.
The Washington Department of Ecology (Ecology) directs the investigation, which is conducted and paid for by Boeing. Investigators seek to determine the location, size and impacts of this underground contamination, which includes solvent chemicals, primarily trichloroethene (TCE) and vinyl chloride (VC), from past releases.
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 at 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. These include 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.
In April, 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 no presence of solvent chemicals at 34 of these locations. Chemicals were detected in water samples from 15 of the sampling sites.
Fourteen of these locations were in an area just west of Chicago Avenue, between Boundary Boulevard and Ninth Avenue North. One other location – along Junction Boulevard, south of 9th Avenue – showed the chemicals to be present 25 feet below the ground, too deep to impact indoor air.
Groundwater at the water table in the 14 northeastern Algona locations contained concentrations of TCE and VC that could release vapors into the soil. To determine whether this is happening, Ecology has directed Boeing to sample indoor air at homes in this area for TCE and VC vapors.
Ecology has sent a letter and information packet to 23 properties located in areas where TCE or VC was detected at concentrations above a threshold called the preliminary concern level (PCL). Ecology may select additional buildings for evaluation based on findings from the first set of buildings and from further evaluation of the underground water study results in Algona.
The letters to the homeowners ask permission to evaluate their homes for potential vapor intrusion. The evaluation will begin with a visual survey of each home by representatives of Ecology and Boeing’s environmental contractor. Later, with the resident’s permission, contractors will collect indoor air samples to send to a laboratory. The samples will be examined for the presence of TCE and VC.
Property owners – and tenants – who decide to participate will sign an access agreement with Boeing, allowing Boeing’s environmental contractor to enter the building to place and remove sampling equipment. Participation is voluntary and at no cost to the building’s owner or occupants.
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 the 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.
Ecology also has mailed to Algona residents general information about the indoor air assessment process, along with background information on vapor intrusion. That information is available online at https://fortress.wa.gov/ecy/gsp/Sitepage.aspx?csid=5049.
Ecology also has directed Boeing to make plans for a study to begin this summer into whether contaminants in high water table areas may be present in surface water, such as street ditches or ponds that form on private property.
The groundwater contamination does not affect public drinking water systems in the vicinity because the supply wells are located safe distances away from the contamination. Also, groundwater flow in the area carries the contamination from the Boeing property away from the supply wells.
Ecology will continue to provide updates on the investigation as information becomes available.
Ecology maintains updated information on the investigation at: https://fortress.wa.gov/ecy/gsp/Sitepage.aspx?csid=5049.
People with questions or comments about the investigation may contact Ecology at email@example.com.
For more information:
Boeing Auburn contaminated groundwater investigation (https://fortress.wa.gov/ecy/gsp/Sitepage.aspx?csid=5049)
Ecology’s social media (www.ecy.wa.gov/about/newmedia.html)
Larry Altose, Ecology media relations, 425-649-7009, firstname.lastname@example.org
Ed Jones, Ecology hazardous waste and toxics reduction program, 425-649-4449, email@example.com