SIX WEEK RBCA SAVING $300,000.00.
This site was an insurance claim in which
the plaintiff had proposed a site remediation with a cost of over $300,000.00. An analysis
of the physical setting and the type of contaminant involved indicated that a risk based
analysis was appropriate and that the site may have been able to be closed through a Risk
Based Corrective Action report (RBCA). The physical setting of the site was such that the
water table was at 70 feet below ground surface and in an area designated for
non-beneficial use of the groundwater. The soils plume was large and consisted mostly of
waste oil, with small amounts of benzene and tetrachloroethylene. Estimates were provided
for an above-ground treatment system or a dig-out and haul. Both estimates were for
approximately $300,000.00, which, with the standard overruns, would probably have gone to
over one-half of a million dollars.
An analysis of the site indicated that for
$30,000.00, a RBCA could be prepared and submitted to the regulatory authorities for
analysis and, perhaps, approval. Tasks that had to be completed were a three-dimensional
delineation of the plume at the subject property, an analysis of the transport of the
constituents of the plume to the water table, an analysis of the pathways and receptors
for the toxic compounds and a clear demonstration that no receptor would be adversely
impacted by the plume.
The drilling and sampling of the subject
property revealed a perching layer at 25 feet below grade that had very poor hydraulic
characteristics and that would retard the flow of the contaminants downward to the
groundwater. In fact, this slowing of the downward migration of the plume was such that
the plume would attenuate at the interface to below action levels for the chemicals
present. An analysis of the near-surface pathways demonstrated that the vapor pressure of
the plume was so low that there was no danger of vapor migration along a preferential
pathway to a receptor.
The last issue to address for this site
was the impact of a dig and haul. Utilizing the laboratory results and the toxicology of
the contaminants a deal was struck with a local landfill to take the soil as daily cover,
thus lowering the cost of disposal of the soils if they were dug up to below $ 10,000.00.
The RBCA was submitted to the regulatory
agency in charge of the site and a closure by RBCA was issued within two weeks. The
underlying case was settled at a nominal amount shortly thereafter.