17-3304 Mariner Avenue Tiyan Barrigada, Guam 96913
671.300.4751 671.300.4752

Total Maximum Daily Load (TMDL) for Chlordane and Dieldrin for Tumon Bay

Total Maximum Daily Load (TMDL) for Chlordane and Dieldrin for Tumon Bay

Pursuant to the Clean Water Act Section 303(d) and 40 CFR Part 130 the Guam Environmental Protection Agency (Guam EPA) seeks public comment on the draft Chlordane and Dieldrin TMDL for Tumon Bay.

The draft may be reviewed through April 18, 2024, Monday to Friday, 8:30 a.m. to 4:30 p.m. at the Guam EPA Administration Building located at 17-3304 Mariner Avenue Tiyan Barrigada, Guam. The report may also be viewed online by visiting epa.guam.gov/tumon.

Written comments DUE BY April 18, 2024
Written comments must be received by the agency via hand delivery or mail and must be addressed to: Administrator, c/o Guam EPA 17-3304 Mariner Avenue Barrigada, Guam 96913-1617. Written comments may be emailed to: margaret.aguilar@epa.guam.gov, Subject: Chlordane and Dieldrin Total Maximum Daily Load (TMDLs) for Tumon Bay.

Comments must include the name, mailing address and email address of the commenter. Written comments must be received, or postmarked no later that 5 p.m. on April 18, 2024. Facsimile submissions will not be accepted. Written comments received by the respective deadline will be reviewed and may be incorporated into a modification of the draft report. For more information, please contact Margaret Aguilar at 671.300.4787 or margaret.aguilar@epa.guam.gov

The Clean Water Act requires states, territories and authorized tribes to identify and list those waters within their boundaries that are water quality-limited, to prioritize them, and to develop TMDLs for the pollutants of concern.

• Water quality-limited waters are waterbodies that do not meet applicable water quality standards or are not expected to meet applicable standards after application of technology-based effluent limitations for point sources.

A TMDL (Total Maximum Daily Load) is the allowable load of a specific pollutant that can be discharged into a waterbody and meet water quality standards.

• Guam’s marine waters are characterized as “good” overall; however, Tumon Bay has been listed as impaired due to dieldrin and total chlordane levels for over two decades (Guam EPA, 2020).

Dieldrin and total chlordane fail to attain the consumption designated use1 and contribute to impairment of the aquatic life use (M-2 marine waters) as listed in the table below.

ChlordanePesticidesConsumptionAquatic life harvesting
Aquatic LifeFish, shell fish and wildlife protection and propagation
DieldrinPesticidesConsumptionAquatic life harvesting
Aquatic LifeFish, shell fish and wildlife protection and propagation

Sampling over the years has been conducted by PCR Environmental, Inc., the University of Guam Water Environmental Research Institute (WERI) in collaboration with Guam Waterworks Authority (GWA), and the military, among others. These studies have typically evaluated inputs to the Bay, in particular groundwater wells in the Northern Guam Lens Aquifer (NGLA) and the freshwater springs that discharge at several locations at or near Tumon Bay beaches.

A recent study for GEPA and EPA Region 9 sampled springs discharging into the Bay as well as many marine locations, seven sediment locations, and four fish species (PG, 2020). Analysis of these data indicate that the chlordane and dieldrin impairments persist in the Bay; however, inputs of the pollutants of concern into the Bay from the springs have decreased.

TMDLs are developed for dieldrin and total chlordane because the latest sampling study supported the continued impairment status for the parameters of concern.

1 The Water Quality Standards regulation requires states, territories and authorized tribes to specify goals and expectations for how each water body is used. Typical designated uses include: Protection and propagation of fish, shellfish and wildlife, Recreation, Public drinking water supply, Agricultural, industrial, navigational and other purposes.

Accessibility Toolbar