Andersen Air Force Base

Overview

Andersen Air Force Base covers about 20,000 acres at the northern end of Guam. It was placed on the EPA Superfund list, known as the National Priorities List (NPL), in 1992. The base sits directly above the Northern Guam Lens Aquifer, a sole-source aquifer that supplies drinking water to at least 70 percent of island residents. Cleanup is divided into 23 operable units, each targeting a different geographic area or type of contamination. A Federal Facilities Agreement signed in 1993 set the legal framework for investigations and cleanup work.

Contaminants found in soil include heavy metals such as arsenic, lead, chromium, and cadmium, along with pesticide residues like DDT, dieldrin, and chlordane. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), asbestos, chlorinated dioxins and furans, and beryllium are also present. Groundwater is contaminated with tetrachloroethene and trichloroethene near the Main Base and Marbo Soils areas. PCBs have also been found in fish tissue. Unexploded ordnance debris adds another layer of concern across parts of the base.

The U.S. Air Force is the lead agency for cleanup, with oversight from the EPA and Guam EPA. Most contaminated soils have been excavated and removed or have restricted access. The main base landfill was closed in 1994 with a protective cover. Seventy-one of eighty-one groundwater investigation and remedial action sites have been addressed. At the MARBO Operable Unit, deep aquifer trichloroethene contamination near the saltwater interface cannot be cleaned without risking saltwater intrusion into the drinking water zone. The remedy there relies on institutional controls, long-term monitoring, and contingency plans for wellhead treatment. The Harmon Operable Unit has been cleaned to unrestricted reuse levels, and the Urunao unit finished cleanup in 2009. No drinking water wells exist in contaminated areas, so contaminated groundwater is not available for consumption. Assessments confirm that human exposure is currently under control across the entire site, with no unacceptable exposure pathways identified. Groundwater migration is also stabilized.

Physical construction is not yet complete across the whole site. A final sitewide remedy decision is estimated between August and October 2027. The most recent five-year review was completed on September 30, 2024. Eleven areas within the base have Land Use Controls restricting access and prohibiting incompatible uses such as residential development. The site has not yet been deleted from the NPL or declared ready for anticipated reuse.

Community members with questions can contact the EPA Remedial Project Manager or the Community Involvement Coordinator. Documentation including five-year review reports and publicly available records can also be accessed through the EPA or the site's Public Information Repository.