Ground Water Quality Standard 1,4-Dioxane; CAS Registry #123-91-1

In accordance with the New Jersey Ground Water Quality Standards rules at N.J.A.C. 7:9C-1.7, the New Jersey Department of Environmental Protection (NJDEP) has developed an interim specific ground water quality criterion of 0.4 μg/L and PQL of 0.1 μg/L for 1,4-Dioxane.  Pursuant to N.J.A.C. 7:9C-1.9 (c), the applicable constituent standard is 0.4 μg/L.  

1,4-Dioxane is used as a solvent, a laboratory reagent and as a trace contaminant in the manufacture of cosmetics.  Its primary use was as a stabilizer of the solvent 1,1,1-Trichloroethane (TCA) (CAS Registry # 71-55-6) and it is often detected in association with TCA.  In the lab, low levels of 1,4-Dioxane is difficult to detect, especially when chlorinated solvents are present.  For the laboratory to obtain the PQL or standard, a separate analytical run is required for low level compounds.

This new interim 1,4-Dioxane standard is an order of magnitude change (over 10 times the previous standard).  The ramifications of this are that all cases within the Site Remediation Program (SRP) are required to re-evaluate whether this new standard constitutes a new compound of concern requiring further investigation, delineation and remediation.
NJDEP has estimated that there are approximately 155 cases in the SRP that have TCA as a compound of concern.  Of these cases, NJDEP estimates less than half may have 1,4-Dioxane present above the standard.  Of these cases, approximately 24 are subject to the May 7, 2016 remedial investigation deadline.

The LSRP should evaluate the laboratory data to determine whether 1,4-Dioxane is reported as not detected with a reporting limit of 4 µg/l or less.  If this data exists, using the 10x rule, further investigation is not required.  If the data does not exist, further investigation is required.  Unfortunately, scientific analysis of the movement of 1,4-Dioxane in groundwater suggests this compound becomes a leading edge of the contaminant plume, moving further and faster than other compounds.  This may result in the need for additional delineation, receptor evaluation and sentinel wells.  This change could also trigger a new evaluation of previously remediated sites or sites at which a permitted engineering control is in place.

For SRP cases subject to the May 7, 2016 deadline this becomes a new unexpected challenge.  LSRPs and the regulated community are requesting that the NJDEP provide relief for special cases involving 1,4-Dioxane.For more information on the NJDEP’s November 25, 2015 revised Interim Ground Water Quality Standards, including 1,4-Dioxane, see:

If you have questions regarding this standard, please contact:

Rick Shoyer, LSRP