Environmental Engineering Reference
In-Depth Information
specii cally iron-reducing, sulfate-reducing, and methanogenic conditions (Arcadis-BBL, 2007c).
The presence of reducing geochemical conditions in all monitored zones is supported by low dis-
solved oxygen concentrations (less than 1.0 mg/L), negative ORP (oxidation-reduction potential)
values, abundant naturally occurring organic carbon in site groundwater, elevated suli de concen-
trations (above 500 mg/L), and elevated methane concentrations (above 50 ppb in some groundwa-
ter samples). The lack of further degradation products beyond cis -1,2-DCE (i.e., vinyl chloride,
ethene) in most monitoring wells suggests that natural biodegradation of chlorinated ethenes may
be stalled, possibly owing to the presence of excessive alternative electron acceptors such as sulfate
and chloride (Arcadis-BBL, 2007c).
SiREM laboratories used polymerase chain reaction (PCR) tests to determine whether indige-
nous Dehalococcoides , an ethene-degrading microbe, was present. SiREM also performed bio-
stimulation tests on-site groundwater augmented with EOS™ as an electron donor, with and without
bioaugmentation using a proprietary bacterial culture, KB-1™. * The fact that the Dehalococcoides
assay on two tested samples was negative indicated that bioaugmentation would be necessary; how-
ever, site data are indicative of active reductive dechlorination. The widespread and persistent
occurrence of 1,4-dioxane, in conjunction with evidence of chemically reducing conditions, which
are the opposite of the aerobic conditions that 1,4-dioxane-degrading bacteria generally require,
suggested that geochemical conditions do not favor natural biodegradation of 1,4-dioxane.
8.4.4 C OMMUNITY R ESPONSE
Communication with the Tallevast community has been a major challenge for the regulators and the
responsible party due in large part to the dynamic nature of characterizing a plume and the late
discovery of 1,4-dioxane. Because some community members felt that they should have been
informed of the site investigation earlier, these residents were not inclined to trust the assurances
they received that their concerns would be addressed. Local newspaper articles suggest that resi-
dents viewed much of the information they received through a lens of distrust. The events that fol-
lowed the initial discovery of contamination in private wells apparently strengthened the residents'
assumptions that they were not being told the full story of the contamination. These events include
the chlorinated solvent plume's turning out to be much larger than originally determined, the dis-
covery of 1,4-dioxane in 2006, inconsistent laboratory results, and a health study by FDOH that
mistakenly used incorrect data.
Tallevast residents formed a citizen action group called FOCUS—Family Oriented Community
United Strong. FOCUS was successful in obtaining substantial funding from the responsible party
to retain an independent consultant to review and advise community members on the content of
technical documents in lay terms. The independent consultant also performed additional soil and
groundwater sampling and a supplemental health risk assessment and participated in technical strat-
egy discussions with the responsible party and regulators. The Vice President of FOCUS, Ms Wanda
Washington, provided the local newspapers with a series of insightful quotations that underscore the
challenges that regulators and responsible parties face when plumes affect private wells. These
quotes are included here not to malign the FDEP, FDOH, the responsible party, or their consultants;
rather, the quotes are provided to emphasize the dilemma faced by regulators, responsible parties,
consultants, and the community alike when 1,4-dioxane contamination is discovered late in the
cycle of site investigation and remediation.
Regarding the expanding plume, Ms Washington provided this comment:
“These experts get up and talk about my safety and welfare and say everybody is OK,” said Wanda
Washington, vice president of Tallevast's community group FOCUS. “Then they draw this 50-acre plot,
* EOS™ is an emulsii ed edible oil used to stimulate anaerobic biodegradation of chlorinated solvents and other contami-
nants; KB-1 Dechlorinator (KB-1™) is a natural microbial culture used to introduce Dehalococcoides organisms to sites
where they are absent to promote the complete dechlorination of PCE, TCE, DCE, and vinyl chloride in groundwater.
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