An environmental clean-up at a gas station usually involves removal of underground storage tanks (USTs) and/or pump islands, excavation of contaminated soils, installation of monitoring wells, and possibly a ground-water remediation system. In most cases, the contamination remains shallow because petroleum is lighter than water and is a “floater.” Because petroleum floats, ground water limits its vertical migration. These physical properties of petroleum make remediation relatively easy in most situations (on the order of $100,000 to $750,000).
What about dry cleaners?
They are usually a small operation in a strip shopping center. How bad could contamination from such a small enterprise be? To answer this question we need to consider the properties of dry cleaning fluid: specifically PCE. A release from a dry cleaner can be from a variety of sources.
For example:
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Disposal of used PCE to a septic system
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A leaky public sanitary sewer system
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Leaky dry cleaning machines
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Dumping of waste PCE out the back door (even dumpsters used only for dry cleaner filters have been implicated as sources of ground water contamination.)
PCE is both relatively insoluble in water and denser than water (often referred to as a dense non-aqueous phase liquid or DNAPL). These two properties cause the PCE to sink through the water table in relatively cohesive globules. This means the ground water does not prevent the downward migration of PCE, as it does petroleum. The PCE will travel downward through the ground water until it hits a physical barrier, such as a clay layer or a bedrock trap, where the PCE will accumulate. Though PCE is “relatively” insoluble in water, it is soluble enough that the pools or globules of PCE will bleed off a dissolved plume at levels that greatly exceed drinking water standards. To make matters worse, the dissolved plume is typically easy enough to find, but the pool or pools of PCE causing the dissolved plume are usually very difficult to locate.
Okay, so what does this all mean? Basically, you have to be careful when evaluating a release at a dry cleaning site. You have to “think” like the PCE – where is the nice low spot where it will accumulate?
Once the extent of contamination is known, the costs of remediation can vary greatly depending on the strategy pursued. We have seen instances where our competitors have insisted that the overlying building(s) required demolition in order to address soil contamination. In both of these cases, we were able to save the building and remediate the impacts to state standards.
Final note:
U.S. EPA recently revised their estimated carcinogenic risk potential for PCE. Use of the new PCE toxicity factors may indicate that less remediation is required to meet risk-based remediation goals. The overall reduction in assumed PCE cancer toxicity may increase the redevelopment of dry cleaning facilities and manufacturing facilities plagued by PCE contamination that were previously considered unusable. Contaminated properties may be redeveloped with fewer deed restrictions, and property values may increase.
While Roux Associates can’t promise you an inexpensive remediation, we can promise you a cost effective remediation. Due to the sinking nature of PCE, cleanup of dry cleaner sites often can be several millions of dollars. So don’t let size fool you. Remediation of a small neighborhood dry cleaner can cost more than several gasoline stations put together, particularly if it was in business before the mid-1980s.
If you are involved with a dry cleaner redevelopment or remediation, we would be glad to review it with you and discuss options for managing the site. Roux Associates has implemented remedial actions at several dozen dry cleaners in 8 states. We can help you identify the most cost-effective strategy.
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