Environmental Engineering Reference
In-Depth Information
urban or industrial areas. This situation occurs worldwide wherever current or past land use includes
industries that used 1,4-dioxane or 1,4-dioxane-stabilized methyl chloroform, or industries that
produce 1,4-dioxane as a by-product (see Chapter 2). Clearly, a coherent strategy is needed to
perform screening-level testing of drinking water sources of 1,4-dioxane.
10.2.2 USEPA' S C ONTAMINANT C ANDIDATE L IST I NCLUDES 1,4-D IOXANE
As described in Section 6.1.1, the CCL includes contaminants judged by USEPA staff and a commit-
tee of experts to warrant further evaluation due to known toxicity, prevalence and magnitude of
occurrence, and persistence and mobility. 1,4-Dioxane was included on the i nal CCL3, a list of 104
chemicals pared down from about 7500 chemicals reviewed by USEPA's staff and expert commit-
tees. USEPA's mandate is to issue a formal decision on whether to initiate a process to develop a
national primary drinking water regulation for a specii c contaminant. USEPA is required by law to
make regulatory determinations for at least i ve contaminants from the most recent CCL every
i ve years; however, the CCL list does not directly require monitoring. A related program, the
Unregulated Compound Monitoring Requirement (UCMR) program, requires monitoring of selected
contaminants that may be present in drinking water but do not have health-based drinking water
standards. The UCMR list is revised every i ve years and is largely based on the CCL.
The Safe Drinking Water Act Amendments of 1996 stipulate that no more than 30 contaminants
are included on the UCMR list per i ve-year cycle. 1,4-Dioxane is not included on the current cycle
(UCMR2 from 2007 to 2010) (USEPA, 2008). It is therefore unlikely that USEPA will require
monitoring for 1,4-dioxane anytime soon; however, to prepare for eventual monitoring needs for
both USEPA's drinking water and Superfund programs, USEPA has developed a new analytical
method for 1,4-dioxane analysis, Method 522 (see Section 4.5.7). While USEPA's drinking
water programs do not yet require that water utilities monitor their supply wells for 1,4-dioxane,
some water utilities have decided to monitor for 1,4-dioxane voluntarily due to known releases of
1,4-dioxane at solvent contamination sites lying within the zones of contribution to the selected
wells. Voluntary monitoring has detected 1,4-dioxane in numerous public water supply wells. It is
therefore important that water utilities and state drinking water regulatory agencies maintain a
detailed awareness of groundwater contamination investigations near supply wells.
10.2.3 I NTEGRATING A WARENESS OF G ROUNDWATER C LEANUPS TO P RIORITIZE 1,4-D IOXANE
M ONITORING IN W ATER S UPPLY W ELL S AMPLING P ROGRAMS
Water utilities operating municipal water supply wells are required to monitor water quality by state
agencies charged with regulating drinking water. Monitoring requirements typically include a list of
analytes and a schedule setting the monitoring frequency. Monitoring frequency is typically increased
following detection of a contaminant. The baseline monitoring frequency for VOCs and SVOCs—the
suites of analytes that would include analysis of 1,4-dioxane—is usually once every three years; hence,
water utilities typically monitor one-third of their wells for VOCs and SVOCs each year. State agencies
have been very effective at managing water utility compliance with required monitoring programs, and
water utilities have been diligent at implementing the programs. While some water utilities have volun-
tarily added contaminants to the monitoring list, most water utilities are inclined to follow the require-
ments of the state regulatory agency and let the regulators determine whether additional contaminants
should be included. Those water utilities that choose to monitor for unregulated contaminants are chal-
lenged to justify exploratory monitoring to their ratepayers, who may protest when asked to pay for
discretionary monitoring or research projects. Some water utilities do not monitor for unregulated con-
taminants simply because it is not required. Many water utilities are reluctant to independently deter-
mine whether there is cause to test for a given contaminant as they are not in a position to take on the
responsibility for determining health risks. This perspective is summarized by the question, “If you
don't want to i nd something, why would you test for it?” Most water utilities prefer to await an ofi cial
Search WWH ::




Custom Search