EPA ID# WA8570024200
EPA Region 10
Pierce County

9th Congressional District

Other Names: USAF - McChord Air Force Base, McChord Wash Rack Area
Last Update: May, 2010

Hide details for Site DescriptionSite Description

McChord Air Force Base is an active military base south of Tacoma, Washington, covering almost 4,600 acres. The base provides airlift services for troops, cargo, equipment, passengers, and mail. Since 1940, almost 500,000 gallons of hazardous substances have been used and disposed of on the base.

The Wash Rack/Treatment Area is a former aircraft washing facility located in the northern portion of the base. The site encompasses a paved area, where chemical solvents were used to remove oil, grease, and other foreign materials from airplanes, and two unlined leach pits that received contaminated runoff from the adjacent paved area.

The aquifer beneath the site supplies drinking water to McChord Air Force Base, the Lakewood Water District, and the American Lake Gardens development. American Lake Gardens is a separate National Priority List (NPL) site. Over 16,000 people live within three miles of the site and approximately 300 domestic wells are located within five miles of the base.

Site Responsibility: This site has been addressed through Federal actions.

NPL Listing HistoryDates
Proposed Date:10/15/1984
Removed Date:
Withdrawal Date:
Final Date:07/22/1987
Deleted Date:09/26/1996

Hide details for Threats and ContaminantsThreats and Contaminants

Media Affected: Groundwater
A layer of fuel sits on top of the groundwater table, covering an area of approximately 300,000 square feet. The fuel layer is primarily an oil emulsion, contaminated with benzene. Benzene levels in the groundwater have fallen below EPA-established safe drinking water levels.

Hide details for Cleanup ProgressCleanup Progress

In 1992, EPA completed an investigation to determine the type and extent of contamination at the base. Based on this investigation, it was decided that the best approach was passive removal of the fuel layer.

After beginning this action, it was found that the volume of the fuel layer had been overestimated. The original remedy was changed in 1994, to natural attenuation, whereby the contaminants naturally dissipate and degrade over time. Since 1994, benzene levels have remained below the action level indicated in the Record of Decision.

The site was deleted from the NPL on September 26, 1996. To ensure that the no unacceptable risk is posed by the site, the Washington State Department of Ecology (WDOE) still monitors the levels of petroleum hydrocarbons in the aquifer.

A five-year review was conducted in 2004 to verify that the revised remedy remains protective of human health and the environment. The assessment of this Five-Year Review found that the remedy is operating as intended by decision documents. Remediation levels for groundwater generally have been attained throughout the site, and no CERCLA hazardous substances have been left in place. Weathered, diesel-range total petroleum hydrocarbon (TPH) is the only contaminant that remains in place above Model Toxics Control Act (MTCA) cleanup levels. Future monitoring will be overseen by the Washington State Department of Ecology. As such, EPA determined that this report be considered the final Five-Year Review for the Wash rack/Treatment Area under CERCLA. No future Five Year Reviews will be conducted at this site.

Hide details for Regional ContactsRegional Contacts

SITE MANAGER(S):Nancy Harney (EPA Contact)
PHONE NUMBER:206-553-6635

Chuck Hinds (state)
Information pertaining to this site is housed at the following location(s):
McChord Air Force Base Library (Administrative Record)
Building 765, 62 CSG/SSL
Tacoma, WA 98438