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The 1,4-Dioxane Book

The Complete Reference

Dave Matthews, a colleague of mine at the Santa Clara Valley Water District, asked me this question in November 2000, shortly after I began working there to provide stakeholder oversight on solvent release cases. He had read somewhere that it is an additive to the widely used degreasing solvent methyl chloroform (1,1,1-trichloroethane) and noted that he was not aware of any testing for 1,4-dioxane at a large aerospace facility with multiple solvent release sites in San Jose. I had never heard of 1,4-dioxane, so I requested “a few hours” from my supervisor, Jim Crowley, in order to do some research. Jim was quick to embrace the idea as he too was curious about the potential for solvent stabilizers to degrade groundwater, a critical resource for Silicon Valley’s water supply. Silicon Valley has an abundance of electronics firms—printed circuit board manufacturers, “wafer fabs” (semiconductor production plants), memory chip producers, and much more—all of which use chlorinated solvents, including many that use methyl chloroform. Thus began the pursuit that led to the 2001 Solvent Stabilizers White Paper in which I assembled a wide range of information on 1,4-dioxane that proved to be useful to regulators and remedial project managers dealing with solvent release sites. I thought this pursuit would end with the White Paper, but that was only the beginning.

After I presented the White Paper at a 2001 symposium hosted by the Groundwater Resources Association of California (GRAC), I posted it online. Eventually, groundwater professionals from around the country and several from overseas downloaded the paper and followed up with e-mail and telephone inquiries. These e-mails provided a wealth of additional information on how 1,4-dioxane was showing up in different types of industrial groundwater contamination sites, how it was migrating through groundwater in different hydrogeologic settings, and how different states were regulating 1,4-dioxane.

The White Paper also led to three key surveys for the presence of 1,4-dioxane at solvent release sites. First, the San Francisco Bay Water Board (SFBWB) asked for 1,4-dioxane analyses at 15 Silicon Valley sites known to have used and released methyl chloroform. 1,4-Dioxane was found at 12 sites, mostly at low concentrations; however, concentrations at some sites exceeded 1000 micrograms per liter (μg/L). The aerospace facility for which the 1,4-dioxane question was first asked proved to have widespread 1,4-dioxane contamination: one monitoring well had a concentration of 11,000 μg/L. Second, the chief geologist of the Department of Toxic Substances Controls (DTSC), Brian Lewis, arranged for his agency to conduct a sampling survey for 1,4-dioxane at about three dozen sites; it was found at more than half. Brian Lewis also arranged the third effort, in which I was invited to participate in a series of monthly teleconferences of the U.S. Environmental Protection Agency (USEPA) Superfund Groundwater Forum, which culminated in an informal survey of existing 1,4-dioxane data in Superfund case files nationwide. More than 50 Superfund sites had 1,4-dioxane detections, some at very high concentrations; however, groundwater at most of the more than 2000 Superfund cases had not been analyzed for 1,4-dioxane.

The Superfund Groundwater Forum discussions of 1,4-dioxane led USEPA Region 3 to recommend testing for 1,4-dioxane in 2003 at Bally, Pennsylvania, where water from a solvent-contaminated municipal well was being treated using air stripping, and the treated effluent was distributed to supply the town’s drinking water. The municipal well was located a 1000 ft from a facility that produced urethane panels for refrigeration insulation and had discharged spent solvent waste to unlined lagoons between 1960 and 1965. The well test showed that 1,4-dioxane was not removed by air stripping. The initial detections in the air stripper effluent that was pumped into the water system were as high as 60 μg/L.