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The 1,4-Dioxane Book

The Complete Reference
Introduction – What about 1,4-Dioxane?
Continues from previous

Opportunities to use solvent stabilizers as a forensic tool to solve contamination problems such as deconvoluting commingled plumes of a common solvent or determining the age of a release are examined in Chapter 9. In Chapter 10, the regulatory policy implications of the discovery of 1,4-dioxane at solvent release sites after cleanup has begun are discussed. 1,4-Dioxane is emblematic of “emerging contaminants,” a cast of chemicals that includes N-nitrosodimethylamine, 1,2,3-trichloropropane, perfluorooctanoic acids, perflorooctane sulfate compounds, and a number of others. The manner in which these compounds are addressed holds profound implications for the indirect potable reuse of recycled water—a critically important resource in the arid southwest—and the discharge of treated wastewater to freshwater bodies whose downstream uses include drinking water. The regulatory policy toward 1,4-dioxane, whether declared in written guidance or inferred from the practices of caseworkers on individual cases, is profiled in Chapter 10 as well. Gaps in the regulatory framework that facilitated the situation in which we now find ourselves—blindsided once again—are also examined in Chapter 10. Regulatory solutions via “green chemistry” and the European Union’s REACH (Registration, Evaluation and Authorization of Chemicals) program are discussed.


This book embodies a great deal of information on 1,4-dioxane, but how can this be of use to you? Let us make it tangible with some real-world examples that should convince you that what you do not yet know about 1,4-dioxane could indeed harm the interests of your client, employer, site owners, or investors, and not least, drinking water consumers. The mobility, persistence, and treatment challenges combine to make 1,4-dioxane a particularly vexing contaminant. It is more mobile than any other contaminant you are likely to find at solvent release sites. If you have worked at fuel-leak sites in the 1990s, you could think of 1,4-dioxane as “MTBE on steroids” to get a better sense of what this book is about. The mobility, persistence, and treatment of 1,4-dioxane in groundwater present formidable challenges to site characterization and remediation.

Because analytical methods for 1,4-dioxane were not widely available before the late 1990s, many solvent contamination site investigations did not include testing for 1,4-dioxane. Now that the analytical methods are available and more regulators have taken an interest in 1,4-dioxane, it is being discovered long after the extent of solvent plumes has been delineated, the treatment technology selected, the capture zone established, and the health risk assessment completed. The Record of Decision (RoD) or the equivalent regulatory cleanup decision has been established at many solvent release sites without consideration or examination of 1,4-dioxane. When 1,4-dioxane is later discovered, the adopted and implemented cleanup plan that was working just fine and well on the way to site closure can be turned upside down. In short, 1,4-dioxane has every potential to be, and has been, a “RoD reopener.”

Consider the experience of a consultant managing a San Jose, California, solvent recycling facility cleanup site. In 1998, the contracted laboratory inadvertently analyzed for an expanded list of analytes for a few site monitoring well samples and reported 1,4-dioxane at concentrations up to 56,000 μg/L. Analysis for 1,4-dioxane was not a site monitoring requirement; however, the regional Water Board requested that all results of tests performed at the site on an elective basis be reported, which the consultant conscientiously did. Follow-on sampling and analysis for 1,4-dioxane led to the discovery that the 1,4-dioxane plume had migrated much farther than the chlorinated solvent plume that had been the subject of the remedial investigation and cleanup, and that the maximum 1,4-dioxane concentration encountered was 340,000 μg/L. California’s Notification Level for 1,4-dioxane is 3 μg/L.