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GeoInsighter Fall / Winter 2000 Newsletter
Volume 5 Number 3

Is 1,4-Dioxane the MTBE of Today's Chlorinated Solvent Sites?

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Like MTBE was at gasoline sites in the 1980s, 1,4-Dioxane is generally not considered a constituent of concern when evaluating chlorinated solvent sites under today's standard of practice, even though it is used as a stabilizer in chlorinated degreasing solvents such as 1,1,1?Trichloroethane (TCA) and Trichloroethene (TCE). Some regulatory agencies such as the United States Environmental Protection Agency (USEPA) and the Massachusetts Department of Environmental Protection (MADEP) are starting to focus on this compound as a constituent of concern at some sites. The USEPA has recognized 1,4-Dioxane in some of their guidance documents as a stabilizer in some chlorinated solvents that is more toxic and persistent in the environment than other solvent compounds under similar environmental conditions. The MADEP has recently requested that 1,4-Dioxane be included in the analytical suite for ground water sample analysis at some Massachusetts sites.

1,4-Dioxane is an ether used as a stabilizer in some chlorinated solvents. TCA and TCE reportedly contain 2 to 3.5 percent and approximately 1 percent of 1,4-Dioxane, respectively. It is also used as a solvent for varnishes, paints, dyes, and lacquers, as well as a reaction medium solvent in organic chemical manufacturing. Its relatively low Henry's Law constant and high solubility suggest that this chemical will readily dissolve in ground water, will not typically sorb to soil, and will not readily volatilize from ground water, thus making this compound more persistent in the environment than many other solvent compounds. Due to its physical and chemical characteristics, common treatment methods such as air stripping, carbon adsorption, and air sparging do not work well for 1,4-Dioxane. The reported treatment technology of choice for this compound is UV oxidation with hydrogen peroxide. 

There are no reported federal or New England State drinking water or other risk-based standards for 1,4-Dioxane. The MADEP ground water reportable concentrations are 1 and 10 milligrams per liter (mg/l) for RCGW-1 and RCGW-2 category ground water, respectively. Region III and Region IX of USEPA have established a risk-based concentration for tap water or a preliminary remedial goal of 6.1 micrograms per liter (ug/l). Florida has reportedly established a ground water guidance concentration of 5 ug/l for 1,4-Dioxane.

The decision to analyze ground water for this compound may depend upon the following:

1) the type of solvent released and the time of the release, if known;

2) state or federal regulatory requirements or policies regarding 1,4-Dioxane; and

3) whether you are a potentially responsible party to a solvent release, a potential buyer of a property where solvents were used, or the owner of a property hydraulically downgradient of a solvent release.

We will continue to track regulatory changes for this compound and provide updates in future newsletters.

Richard J. Wozmak, P.E., P.H., L.S.P., L.E.P.
 info@geoinc.com

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