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Site Summary and Technical Overview, Part I
June, 1999

 

Overview

During the 40+ years that Hercules produced toxaphene in Brunswick, Georgia, pesticide waste was pumped into the Terry Creek area in the expectation it would dilute and disappear. However,  high concentrations are still found, and the contamination is extensive. Much of the toxaphene remains in the drainage, even though dumping was stopped over 25 years ago

Toxaphene coats the bottom, sides, banks, and islands of the Terry Creek Disposal Area. Toxaphene is found several feet deep in marsh sediments, and components of toxaphene are extracted from fin and shellfish that breed and forage in the marsh.

Toxaphene is a carcinogenic mixture of chemicals banned from use and manufacture two decades ago. The material is a "biocide," a broad-spectrum toxin that kills a diversity of animals including insects, fish, birds, and man. Toxaphene exerts lethal effects by enzyme inhibition and mutation, and possibly by steroid mimicry. It is extremely stable in the environment, with a half-life (time to break down) of around 10 years. Its breakdown products are potentially harmful as well. In the class of organochlorines, toxaphene is a mixture of several hundred different chemicals produced by treating and chlorinating pine tar.

Unfortunately, although the Environmental Protection Agency (EPA) has known of the problem at Terry Creek for a quarter century, historical site monitoring was conducted so poorly that we have no information on how fast toxaphene is undergoing natural attenuation, or even if it is breaking down.  Worse still, dredging operations were allowed to continue during this period, which has created additional problems of toxaphene distribution.

The Terry Creek Site is an estuary. Estuaries occur where fresh water from upland rivers mixes with ocean salt water. Plants and animals that live permanently in an estuary must be adapted to a life of changing salinity (salt concentration), temperature, current direction, and silt flow. During high tides the estuary may have mostly open-ocean species of fish, during low tide the fish populations may reflect the freshwater river system. Estuaries are recognized as the oceans "nurseries" since they often function as the primary breeding ground for open water species. The Terry Creek system is bordered by "wetlands" -- areas of mostly terrestrial plants and animals adapted to occasional flooding.  The scientific literature does not show another example of an estuary/wetland system polluted to this degree with a single complex pesticide. However, since the area is clearly a productive fishery, it is fair to assume that the site impacts a much broader area than just the local creeks. Additionally, the area is a forage zone for Federally protected waterfowl and turtles, both of which may be adversely affected.

Based on the historical descriptions in the Site Record, the marshes of the Terry Creek system were relatively undisturbed in the early part of this century. The area seems to have been a major source of shrimp, crabs, fish and shellfish. In the late 1930's, portions of the drainage were dredged to allow access of commercial vessels. This dredging was conducted by the U. S. Army Corps of Engineers (the USACE, or “Corps”) and the channels were maintained at irregular intervals until the present. The dredge spoils were placed as either spoil islands or spoil banks along the channel.

Hercules began manufacturing toxaphene at the current plant site in 1948. Toxaphene dumping into Dupree/Terry Creek occurred throughout the history of the product. Estimates are that 250-300 pounds per day were emptied directly into the estuary before 1972 when legislation forced Hercules to treat waste before it left the plant. Although there were some spills and overflows during the final years of toxaphene production, the amounts released between 1972 and 1980 seem to have been close to background levels. During the peak of toxaphene production and pollution of the Terry Creek system, the USACE dredged the waterways to relieve silting of the channels. Consequently, some toxaphene-contaminated silts were dredged and placed in spoil impoundments.

A network of berms and dikes occur within the marsh. These are constructed to reduce flooding of upland areas near the marsh. Weirs are also placed within the dikes to improve sediment settling. Weirs control water flow out of an impoundment area. By regulating the height of the weir drain, a ponding action allows sediments to settle out before water is released, resulting in cleaner water released to the system. A weir regulates water outflow between the Hercules Outfall ditch and Dupree Creek. Over the decades there have been numerous dike raisings, new berm constructions and dredging operations. Some of the construction used toxaphene contaminated soil, others did not. Extensive testing has not been performed in these areas to evaluate for the presence of pesticide. Dredging operations were in the Terry Creek portion of the estuary. Dupree Creek has apparently not been dredged, and toxin  occurrence has not been evaluated sufficiently in that portion of the creek.

The Back River forms the northeastern boundary of the site. Terry Creek forms the southern boundary, and the northwestern edge is Dupree Creek. The area is roughly triangular, with the southern edge parallel to Torras Causeway. 

Running into Dupree Creek from the Hercules plant is the "Outfall Ditch" where toxaphene and other waste from the Hercules Plant were released into the marsh. Toxaphene concentrations are high enough in this area to consider it a "source" of continued contamination. The Outfall Ditch merges with the marsh near the confluence of Dupree and Terry Creeks. This contamination zone extends eastward along the bed and banks of both creeks.

There are four spoil deposition areas. Area 1, the Main Dredge Spoil area is a 72 acre rectangular area between Terry and Dupree Creeks. Toxaphene concentrations in this area are as high as 240 ppm (parts-per-million) in surface samples, and in subsurface samples up to 430 ppm. The area is surrounded by a 22-foot high dike, built in two stages. The second round of construction likely used toxaphene contaminated dredge material. Three weirs drain water from the impoundment into the marsh along the Dupree creek border. There are no linings or other barriers to prevent toxaphene from migrating vertically beneath the site. 

Area 2, the Riverside Dredge Spoil Area, is adjacent to the residential housing along Norman and Crandall Streets, and Riverside Road. This area, about 52 acres, is parallel to the Back River. Pesticide concentrations in subsurface soil range to 23 ppm.

Area 3 comprises about 7 acres within a residential area on Terry Creek Drive, directly south of Area 1 and Terry Creek, parallel to Torras Causeway. Concentrations in this area are as high as 9 ppm.

Area 4 is the Carter’s Island Spoil Area, a small deposition area just south of the confluence of Terry Creek and the Back River. Toxaphene concentrations reach 100 ppm in this area.

There are nine trailers and four houses within Area 3; Areas 1, 2, and 4 are unpopulated. Some portions within Area 2 may be developed in the future.

There are two aquifers underlying the site. The main source of municipal drinking water used by local residents is the Upper Floridan aquifer, which appears unaffected by the site.  According to documents in the Repository, the shallower surficial aquifer is not utilized around the site. Documentation for this conclusion was not readily apparent, and some citizens have questioned the conclusion. However, it seems unlikely that toxaphene would migrate to the aquifer from the marsh site in sufficient amounts to constitute a hazard to any well in the area. Surface water, sediments, and local soils are the main concern. Air pollution is not now a problem, however depending on the choice of cleanup methods, air pollution may become a problem in the future. There are a number of other toxins in the system, consistent with the site being used for 60+ years as an industrial chemical dump. The range of these chemicals is poorly defined in site documents.

The site repository documents indicate legal complexities at this site.  It is not clear if these events are inhibiting the pace or nature of the cleanup. There appear to be some disputes over toxaphene origins and cleanup responsibility at this site. The Administrative Record shows correspondence from the Corps of Engineers disputing EPA claims that spoil impoundments controlled by the USACE are a "source" of toxaphene contaminated materials. Further, EPA suggests that toxaphene in the creek channels may come from Area 1 weirs that regulate water flow to Dupree Creek. The Corps disputes that.  A recent study seems to support the USACE’s position that toxaphene is confined within the berms of the Main Dredge Spoil Area.  There seem to be jurisdictional disputes over ownership of some lands impacted by toxaphene spoils placed on shore. Long-term residents all agree that dredge spoils, possibly containing toxaphene, were used to reduce wetland marsh areas. Some of these areas may now contain residences. The Record provides only general locations for these areas, the investigation appears poorly performed, incomplete and inconclusive.

Conclusions, Part I

The full extent of the contamination is poorly defined at this time. Based on the testing, there is contamination in residential neighborhoods bordering the marsh. Testing and information from local residents seems to support claims that dredge spoils were used to form residential areas. Thorough studies are still needed to better understand the scope of the problem.

Part 2 of this series will discuss toxaphene analysis and sampling at this site. It appears that some of the methodology used is compromising integrity of the assessment and may be under-representing the full extent of the problem.

Part 3 will discuss cleanup options for the dredging and treatment of the marsh.

  Written by R. Kevin Pegg, Ph.D.; edited by Dr. Mary S. Saunders. Copies of the newsletter are available from the GEC, at the Glynn County library, or at www.NucleicAssays.com/tags  on the Internet.

"This project has been funded wholly or partly by the U.S. Environmental Protection Agency under Assistance Agreement Number 1984482-98-0 to The Glynn Environmental Coalition, Inc. The contents of this document do not necessarily reflect the views and policies of the U.S. Environmental Protection agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use."

 
   
   

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