A poisoned paradise: Report cites dieldrin and chlordane contamination in Tumon Bay

By Mar-Vic Cagurangan

The clear blue skies, the calm turquoise sea water and the pristine white-sand beaches form a breathtaking combination that makes Tumon Bay postcard-perfect. But lurking behind Guam’s idyllic shoreline is a quiet danger.

“Tumon Bay has been listed as impaired due to dieldrin and total chlordane levels for over two decades,” according to a January 2024 report prepared by PG Environmental LLC for the Guam Environmental Protection Agency.

While GEPA has lifted its “do not drink without treatment” advisory for dieldrin contamination at Guam Waterworks Authority’s production wells in Dededo and Yigo, the presence of dieldrin and chlordane in Tumon Bay has been drowned in silence.

“Dieldrin and total chlordane fail to attain the consumption-designated use and contribute to impairment of the aquatic-life use,” states the report, which identifies military installations as possible sources of the contamination.

Dieldrin was discontinued in 1987 and chlordane in 1988. Both were used as pesticides, termite and agricultural pest control until they were banned. The U.S. Environmental Protection Agency listed both chemical products as “probable human carcinogens.” The federal agency cited an occupational study, which showed a link between chlordane exposure and non-Hodgkin's lymphoma.

While several Guam waterways have been flagged as threatened by pollutants, Tumon Bay has been ranked a high-priority site for Total Maximum Daily Load (TMDL) calculation, a tool under the Clean Water Act to attain water quality standards.

According to the PCR report, Tumon Bay has been designated as “M2,” which sets certain restrictions on water activities. According to the GEPA, water in this category “requires sufficient quality to allow for the propagation and survival of marine organisms, particularly shellfish and other similarly harvested aquatic organisms, corals and other reef-related resources and whole-body contact recreation.”

It is not clear, however, whether the dieldrin and chlordane contamination in Tumon Bay has been addressed. (GEPA and GWA did not respond to our request for comment or update on the report.)

The 2024 report said Tumon Bay was also listed for tetrachloroethylene, trichloroethylene , antimony and arsenic. “However, current monitoring data

for Tumon Bay indicates the applicable water quality standards for these

ollutants have been attained, and GEPA is undertaking to delist Tumon Bay

for these pollutants.”

Tumon Bay receives discharges from groundwater wells in the Northern Guam lens aquifer and freshwater springs. The PCR report identified military installations as potential sources of pollution to Tumon Bay due to their proximity to the northern aquifer. 

Andersen Air Force Base, the U.S. Naval Computer and Telecommunications Station and the newly opened Marine Corps Base Camp Blaz are located in the northern part of Guam.

“Military installations utilize or have historically applied numerous

contaminants that may be introduced to the environment.

Chlordane and dieldrin are now banned but could have been used in prior landscaping or maintenance activities as pesticides,” the report said.

Photo courtesy of Bobby Jacobsen/PCR

PCR noted that military installations were notorious for poor disposal of hazardous materials. “Specifically, Andersen AFB was reported to improperly discharge pollutants into storm drains or the ground, and elevated levels of all the constituents of concern were observed in dumping grounds in and around Marbo Annex,” the report said. “Elevated levels of PCE were also observed in the Tumon-Maui Well from 1990 to 1997 while the well was active.”  

While many pollution sources have either been remedied or may no longer be active, PCR noted that legacy contamination may persist in the aquifer and in Tumon Bay itself.

Landfills are also suspected of being another source of water pollution. “In the northern portion of Guam, the underlying geology can facilitate the transport of leachate from landfills or dumping sites to the northern aquifer, where it can ultimately reach the bay,” the report said.

Modeled after Waikiki in Hawaii, Tumon Bay became Guam's primary tourism hub in the 1960s following the opening of the Pacific Islands Hotel in 1962, which triggered a wave of construction that continued in the succeeding decades. Nonstop development transformed the once low-density coastal area into a commercial zone.

In 1999, the Guam Department of Agriculture designated Tumon Bay as a marine preserve in response to declining fish stocks. The designation limits the types of boating and fishing activities in the bay.  “However, it is possible that 

fish from Tumon Bay are part of the diet of subsistence fishers in the area and are also consumed by recreational fishers,” the PCR report said.

Over the years, EPA, GEPA, Andersen Air Force Base and the Water Environmental Research Institute has sampled springs, sediment locations, and fish species along Tumon Bay to measure toxic pollutants. Polluted waters are subject to quality criteria for “aquatic life protection in saltwater” and 

“protection of human health for consumption of organisms only.”

The specimen collected at Gun Beach—one of the 14 marine stations that were sampled in 2020—had a chlordane concentration of 0.053 µg/L, exceeding the 0.004 µg/L threshold for aquatic life protection, and the criterion to protect human health, the report said.

“The high chlordane concentrations measured in the fish tissue samples suggest that bioaccumulation may be causing persistent issues in the bay or that legacy sediment or other sources, represented by the single marine sample exceedance,

are causing ongoing contamination," the report said.

While the other 13 chlordane samples were below water quality criteria, nine had dieldrin concentrations that exceeded the criteria at 64 percent.

The dieldrin concentrations identified four Air Force samples as exceeding the water quality criteria (15 percent), at least one GWA sample exceeding the WQC and an exceedance in 2021 at the Tumon-Maui Well.

“Due to the ecological, economical and recreational importance of Tumon Bay, its health and condition are a priority for the island,” the report said.

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