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WWRC 85-03
Organic Contaminant Transport in Ground Water, Surface Water and Surface Water Sediments: A Case Study of a Wood-Treating Plant


Studies concerning the transport and fate of contaminants in the environment have typically been limited to single compounds. However, the greatest danger to water resources is most often posed by contaminant mixtures. Hazardous waste disposal facilities, chemical plants, oil refineries, etc., usually produce complex waste streams which may contact ground waters or surface waters. This report presents the results of a study conducted at a wood-treating facility located adjacent to the Laramie River in Laramie, Wyoming. Organic contaminants emanating from this facility include phenolics, polyaromatic hydrocarbons (PAH's), and pentachlorophenoi. Creosote, which is itself a complex mixture of organic compounds, is the main source of contamination at the site. This study was initiated in FY 1983 and continued with USDI funding for a second year through the summer of 1985.

The objectives of this study were to (1) initiate a literature review on contaminant transport models and develop a conceptual model of contaminant transport at the Laramie River site; (2) conduct laboratory (soil column) and field experiments to investigate oil/water emulsion migration through porous media; and (3) begin a field study analyzing contaminant fate in sediments downstream from the wood-treating facility. An additional aspect of this project was to supply the Wyoming Department of Environmental Quality (DEQ) with a summarization of these studies and to provide technical assistance and data review for the on-going litigation between the State of Wyoming and the owners of the wood-treating facility.

Currently, mathematical models are not readily available to effectively simulate the transport and fate of complex mixtures of organic compounds. This is especially true when these contaminants are in high concentrations producing a multi-phase solution. However, a conceptual model based on laboratory studies and site observations shows: (1) subsurface transport of contaminants as hydrocarbon fluids (oil), oil/water emulsions and dissolved in the aqueous phase; and (2) riverine transport of contaminants dissolved in water, sorbed to sediments, and as oil globules.

Experiments with glass columns packed with a uniform material (2 mm glass beads) indicates that even within a very homogeneous, isotropic matrix, oil/water mixtures cannot be expected to flow in a uniform manner. Creosote sludges and oils break up into globules and stringers with no uniform front of contamination. In addition these experiments have shown that contaminants within an oil/water emulsion move at a rate almost equal to that of chloride, while a single compound (naphthiene) shows a lag in breakthrough. These preliminary results indicate that with an emulsion there is sufficient interaction among the compounds in the fluid to overcome the retardation due to adsorption of the organic compounds to the glass beads.

Field studies and chemical analyses of sediments and fish clearly establish contamination of the Laramie River resulting from off-site migration of creosote from the wood-treating facility. However, comparison of contaminant levels from sediments taken in 1983 and 1985 as well as visual field observations indicate a significant decline in the organic contaminants in the Laramie River over the past three years. This decline can be attributed to changes in the flow regimes of the Laramie River as well a remedial actions taken by the personnel at the wood-treating facility.

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