MOSES LAKE WELLFIELD CONTAMINATION WASHINGTON EPA ID# WAD988466355

EPA Region 10 Grant County Moses Lake 4th Congressional District Other Names:

Last Update: October, 2009

Site Description

The Moses Lake Wellfield Contamination site is located about three miles northwest of the city of Moses Lake, Washington, in unincorporated Grant County. The Site encompasses potential source areas around the former Larson Air Force Base, and is currently the home of the Grant County International Airport. Potential source areas are scattered throughout the area, and approximately 1000 acres of groundwater are contaminated with trichloroethylene (TCE). The contamination is the result of operations of the former Larson Air Force Base and industrial activities associated with the aircraft industry. There are multiple potentially contaminated soil waste sites and several groundwater plumes of TCE that pose a threat to human health and the environment. TCE is a solvent used by industries to remove grease. EPA considers TCE highly likely to cause cancer in people. The contaminated groundwater plumes lie beneath and extend south from the former Larson Air Force Base.

The U.S. Air Force used the base for a variety of purposes from 1942 until it was deactivated in 1963. Since 1966, when the base was disbanded and put up for sale, a variety of entities have acquired properties of the former base. The Port of Moses Lake acquired the largest parcel of property for use as the Grant County Airport. Other properties include commercial facilities and residences. The area surrounding the site is residential, agricultural, and commercial.

The groundwater contamination was initially identified in 1988 by the Washington Department of Health during routine sampling of municipal drinking water wells. A number of municipal and private wells have contamination above EPA and state drinking water standards. Two of the contaminated municipal wells were part of a blended system that provides drinking water to approximately 5,000 people. The City of Moses Lake redeveloped their well system soon after the discovery of TCE to obtain clean groundwater from a deeper source. Between 1989 and 1993 the City fixed the three contaminated wells on the former base by deepening the wells. In 2003, EPA and the U.S. Army Corps of Engineers (USACE) completed deepening a groundwater well for a 100-home residential development served by the Skyline Water System. Both of these efforts occurred within the Moses Lake Wellfield Contamination site, and in both cases, clean groundwater was obtained from a deeper source. The Corps and EPA continue to test a representative set of wells (up to 80) at the site. Based on this sampling, five homes have had whole-house filters installed at their wells to remove TCE from the water.

The Remedial Investigation/Feasibility Study (RI/FS) process was completed in 2007. Several TCE groundwater plumes were identified as well as multiple soil contamination areas, some of which are suspected to contain TCE and may contribute to groundwater contamination. EPA issued a Proposed Cleanup Plan for public comment on January 7, 2008. Public comment closed on March 7, 2008. EPA is reviewing public comments and preparing a Responsiveness Summary. EPA will issue its Record of Decision later in 2008.

Site Responsibility: This site is being addressed through federal actions.

NPL Listing History	Dates
Proposed Date:	07/29/1991
Removed Date:
Withdrawal Date:
Final Date:	10/14/1992
Deleted Date:

Threats and Contaminants

Media Affected: Groundwater
Approximately 1000 acres of groundwater are contaminated with TCE. The safe level for TCE in drinking water is set at 5 parts per billion (ppb). The contaminated groundwater at this site contains TCE concentrations above 5 ppb and some areas contain TCE above 80 ppb. Moses Lake municipal drinking water wells were contaminated. The Skyline water system, a private water system with approximately 100 connections, was also contaminated. The Skyline backup well remains contaminated. Direct contact with or ingestion of contaminated groundwater posed a health risk until EPA and USACE recently completed the deeper Skyline well. At this time TCE exposures via groundwater contact, ingestion, and inhalation appear to be controlled for all known groundwater pathways. However, future development could result in new TCE exposures.

Soils - Besides groundwater contamination at the Moses Lake site, there are issues associated with landfills, waste discharge areas, and other potentially hazardous constituent source areas. For example, even though it may not be possible to directly link any specific TCE source area at the former Larson Air Force Base to specific TCE plumes in groundwater, many other hazardous constituents are often located within each source area, so that future development may need to be managed to prevent exposures. Each area where hazardous constituents are located at the site must be considered in this context, and an appropriate remedy selected. The only areas of the site where no further action may be warranted are those where EPA determines hazardous constituents will not pose an unacceptable risk under reasonably anticipated future land-use scenarios.


Cleanup Progress

Short-Term and Removal Actions: The City of Moses Lake voluntarily closed or relocated contaminated municipal wells to a deeper uncontaminated aquifer soon after TCE was detected. Bottled water was provided to Skyline Water Company users for many years until the new Skyline well was completed in September 2003. Therefore, both City of Moses Lake and Skyline Water Company users are protected from TCE exposure. In 2002 TCE was discovered in a sump and soils at the liquid oxygen facility. The sump and contaminated soils were removed by the USACE under an interim remedial action.

Long-Term Actions: Under an interagency agreement with EPA, USACE has completed most of the field work for an RI/FS at the site. EPA will issue the Proposed Plan for the overall remedy for the site for a 60-day public comment period beginning January 7, 2008. The proposed cleanup is expected to cost about $31 million and calls for:
· pumping out the most highly contaminated water and treating it to remove TCE;
· cleaning up the contaminated soil areas by removing soils contaminated above safe levels;
· restoring the groundwater to its highest beneficial use as a drinking water source; and
· requiring local land use restrictions such as changes to local ordinances, zoning, and property easements to protect the public from contaminated groundwater and soils.


Regional Contacts

SITE MANAGER(S):	Rod Lobos
E-MAIL ADDRESS:	lobos.rod@epa.gov
PHONE NUMBER:	509-376-3749
COMMUNITY INVOLVEMENT COORDINATOR:	Suzanne Skadowski
E-MAIL ADDRESS	skadowski.suzanne@epa.gov
PHONE NUMBER:	206-553-6689 or 800-424-4372

Information pertaining to this site is housed at the following location(s):
Moses Lake Superfund Site webpage: http://yosemite.epa.gov/r10/cleanup.nsf/9f3c21896330b4898825687b007a0f33/2f3ffa55a450a0728825653100688c3a?OpenDocument

Big Bend Community College Library
7662 Chanute Street, Building 1800
Moses Lake, WA 98837-3299
(509) 793-2350

EPA Region 10 Superfund Records Center (Administrative Records)
1200 Sixth Avenue, Suite 900
Seattle, WA 98101
(206) 553-4494