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The Triana/Tennessee River site is located in in Morgan, Madison and Limestone counties in northern Alabama. The site includes an 11-mile reach of the Huntsville Spring Branch and Indian Creek tributaries of the Tennessee River. The site is located completely within the Wheeler National Wildlife Refuge and the Redstone Arsenal. Created in 1938, the Refuge provides important habitat for migrating birds as well as many other bird species, while the Arsenal is home to the U.S. Army Aviation and Missile Command and other defense-related agencies. From 1947 to 1970, Olin operated a pesticide manufacturing plant within the U.S. Army's Redstone Arsenal and discharged wastewater into Huntsville Spring Branch. The primary contaminants of concern are dichloro-diphenyl-trichloroethane (DDT) and its breakdown products. Access to the site is highly restricted given its location within the perimeter of the Redstone Arsenal.
In 1983, U.S. Environmental Protection Agency (EPA) listed the site on the National Priorities List (NPL) because of contaminated soil, sediment, surface water, and fish in Huntsville Spring Branch and Indian Creek. EPA, the Alabama Department of Environmental Management (ADEM) and the Olin Corporation (Olin), the site’s potentially responsible party (PRP), have investigated site conditions and taken steps to clean up the site in order to protect people and the environment from contamination.
What Has Been Done to Clean Up the Site?
In 1983, the State of Alabama, EPA and the site’s PRP, Olin Corporation, entered into a legal agreement, referred to as a Consent Decree (CD), requiring that the PRP carry out a cleanup plan to address contamination in fish tissue. The 1983 Consent Decree also created a Review Panel to provide oversight of site activities. The Review Panel includes representatives from the U.S. Fish and Wildlife Service, the Tennessee Valley Authority, EPA, the U.S. Army, and the State of Alabama. Remedial actions called for by the 1983 cleanup plan included:
- backfilling and burial of contaminated material in part of the stream channel;
- digging a new channel to re-route the stream; and,
- construction of diversion structures to prevent the stream from flowing to the former channel, while also diverting stormwater runoff to prevent flow across the filled channel.
The cleanup plan in the 1983 CD called for annual fish monitoring to be conducted as follows:
- Three reaches of water were defined as A, B, and C;
- Largemouth bass, channel catfish, and smallmouth buffalo would be sampled in each reach until continued attainment of the DDT performance standard of 5 parts per million (ppm) in fish fillets. Continued attainment was defined as three consecutive years of attaining the 5 ppm performance standard.
- After all three fish species had achieved continued attainment of the performance standard of 5 ppm in each reach, the 1983 Consent Decree then called for cancellation of fish sampling for seven years, after which each fish species in each reach would be sampled again.
In 1987, the PRP completed the cleanup actions detailed in the 1983 Consent Decree, effectively isolating at least 95 percent of the DDT estimated to be in Reach A.
The PRP stopped groundwater sampling in 1997 because sampling did not detect any significant groundwater impacts.
In 1988, annual fish monitoring began:
- In 1994, largemouth bass had achieved continued attainment of the performance standard in all three reaches A, B, and C;
- In 2003, channel catfish had achieved continued attainment of the performance standard in all three reaches A, B, and C; and,
- In 2015, smallmouth buffalo had achieved continued attainment of the DDT performance standard in all three reaches A, B, and C.
In 2015, with the continued attainment of the performance standard for smallmouth buffalo in Reach A, the annual fish monitoring requirements of the 1983 Consent Decree were met.
EPA, ADEM, and the site’s PRP also conduct Five-Year Reviews of the site to ensure that the site remedy remains protective of of people and the environment. The fifth review of the site was conducted in 2015 and concluded that response actions at the site function as intended pursuant to the 1983 Consent Decree, and that the remedy continues to be protective of human health and the environment.
What Is the Current Site Status?
The next Five-Year Review will be conducted by EPA in 2020.
In 2015, with the continued attainment of the performance standard for smallmouth buffalo in Reach A, the annual fish monitoring requirements were met. Pursuant to the 1983 Consent Decree, fish sampling has been discontinued for seven years, after which fish will be sampled in all three reaches again. This fish sampling event will take place in 2022.