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FOR IMMEDIATE RELEASE
May 10, 2004

Contact: Michael Mann at 475-1623 or mmann@guamepa.govguam.net
Christopher Lund at 475-1621 or clund@guamepa.govguam.net

Guam EPA investigating water quality at NAS-1 well in Tiyan; current sampling results do not indicate immediate public health risk

The Guam Environmental Protection Agency (Guam EPA) continues to investigate the conditions at the NAS-1 well in Tiyan after learning last week that recent sampling results showed above-normal levels of total trihalomethanes (Total THM), a byproduct of the chlorination process. Guam EPA last week ensured that the well was taken off-line and asked the Guam Waterworks Authority (GWA) to turn over field operations records for the well to assist in the investigation.

"Although these above-normal levels of trihalomethanes do not pose an immediate public health risk, we are thoroughly investigating the problem to determine its cause and identify necessary corrective actions," said Guam EPA Administrator Fred M. Castro. "Guam EPA is committed to working with GWA to get this well back on-line, but we will not allow water from NAS-1 into the distribution system without first ensuring that any potential operational problems at the well have been corrected," he added.

Trihalomethanes (THM) are a group of four chemicals that are formed along with other disinfection byproducts when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic matter in water. U.S. EPA has established an annual average maximum contaminant level of 80 parts per billion (ppb) for Total THM in drinking water systems. Although it does not pose immediate health risks, some people who drink water containing trihalomethanes in excess of U.S. EPA's standard over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer.

The NAS-1 well in Tiyan has been providing water to the GWA distribution system since September of last year, when the Guam International Airport Authority (GIAA) completed the installation and testing of a granular activated carbon (GAC) filter system at the well to treat historical contamination of groundwater in the area. Tests have indicated the presence of trichloroethylene (TCE) in the groundwater near NAS-1 as a result of activities at the former Naval Air Station. GIAA assumed the responsibility to clean up the groundwater contamination when it took control of the Tiyan area. Because of this contamination and the special filter used to treat it, Guam EPA requires GWA and GIAA to test the water at NAS-1 monthly for over 50 chemical components.

The current above-normal Total THM levels at the NAS-1 well are not directly related to the historical TCE contamination, but may be related to the operation of the chlorination system and GAC filter.

Guam EPA safe drinking water personnel are investigating the operational history of the well, including the use and effectiveness of the GAC filter and the well's chlorination system. The investigation is expected to continue for at least one week. Guam EPA will announce the results of the investigation at its conclusion.

Although GWA has indicated that it would request permission from Guam EPA to bypass the GAC filter, that request has not yet been received. Guam EPA will thoroughly evaluate such a request if and when it is received to ensure that all water entering the distribution system meets the Guam Water Quality Standards and the standards set by U.S. EPA.



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URL: https://guamepa.govguam.net/programs/admin/news2004/051004.html
Last update: 10 May 2004

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