Like many neighborhood businesses, America's 30,000 drycleaners use solvents as an integral part of their daily operations.
The primary drycleaning solvent, perchloroethylene (perc), was introduced in the 1940s and 50s as an alternative to flammable petroleum-based solvents and now is used by the vast majority of drycleaning establishments.
The introduction of perc revolutionized the drycleaning process, allowing cleaners to locate closer to their customers to provide convenient, quality service.
Of perhaps even greater significance, however, was the development of advanced "dry-to-dry" equipment that followed the widespread use of perc. No longer did clothes have to be transferred from the washer to the dryer. Both steps could now be done in the same machine, which greatly increased the efficiency of the process.
Unfortunately, however, the widespread use of drycleaning solvents also may have led to low-level contamination of soil and groundwater at many facilities as a result of past, lawful waste management practices.
Because the contamination at drycleaning shops is generally minor, these sites are not included on any federal or state "Superfund" list and are rarely, if ever, the target of response actions by federal or state agencies. Increasingly, however, drycleaners have fallen victim to private party cleanup demands and cost recovery actions. These actions very' often affect both present and past owners of the drycleaning facility, regardless of the extent of their contribution to the contamination.
Causes of contamination
Soil and groundwater contamination at drycleaning facilities may have been caused by past management techniques for the disposal of wastewater and solvent wastes, conducted in compliance with the law. These techniques have been largely discontinued as a result of both government regulation and voluntary industry actions. In addition, the industry is committed to eliminating any potential for future contamination.
Wastewater
During the drycleaning process a certain amount of water is collected that has been in contact with the drycleaning solvent. For a typical drycleaner the quantity of this "contact" water may total about one to two gallons per week (50-100 gallons per year), although some cleaners may produce considerably more. Because the perc is not soluble, this water will contain less s than one-tenth of one percent (0.015 %) solvent under normal conditions. As a result, a typical cleaner loses only about 1 ounce of perc (2 tablespoons) to this, water a year.
Under EPA's "domestic sewer exclusion and most local sewer ordinances, drycleaners are able to discharge this water to tile sanitary sewer. In fact, until recently, sewer discharge was the only practical means of disposal of contact water. As a result of a July 1993 EPA decision that cleaners could evaporate this water however, drycleaners now have another option.
Contamination results not from the discharge of contact water, but from the leakage of this water from the sewer lines. Sewer lines, it turns out, are designed to leak. This leakage has increased over time, moreover, as the sewers get older and develop cracks.
Therefore, while drycleaners can control how much solvent is in their waste water, they have no control over what happens to this water after it is released to the sewers. As a result, the drycleaning industry has voluntarily committed to eliminating the discharge of contact water to sewers and encouraged regulatory agencies to prohibit it.
Drycleaning operations produce a certain quantity of waste material including used filters and filter materials, lint, and accumulated oils and other contaminants that contain varying although of perc.
Since the mid-1980s, most cleaners have been required to dispose of these wastes through a licensed and-federally permitted waste contract or. Prior to that time, however, these wastes could be lawfully discarded as ordinary solid waste. Even now, drycleaners that produce very small quantities of waste are not required to contract with a waste hauler.
Leakage of solvent from drycleaning wastes discarded as ordinary waste has been identified as a potential source of significant contamination. While this disposal practice was prevented at most cleaning facilities several years ago, existing federal law allows it to continue at some, very small facilities. In an effort to protect both the environment and these cleaners, the drycleaning industry his proposed that the federal government remove this exemption.
Spills of drycleaning solvent or solvent wastes are another potential source of contamination at cleaning facilities. While the likelihood of such spills has been 'greatly reduced in recent years, drycleaners and their suppliers are taking steps to prevent solvent released during a spill from reaching the soil. These proactive steps include installing containment troughs or berms around equipment, sealing, floors and floor drains, and developing alternative systems for delivery of perc to drycleaners.
Groundwater contamination stems from both natural and man-made sources, and is influenced by geographic location, geological characteristics, chemical composition, and the frequency and amount of precipitation.
Natural contaminants include chlorides, mineral salts, and radioactive materials that leach from subsurface layers. Potential man-made contaminants cover every facet of social agricultural, and industrial activity from septic tanks, to animal feedlots to well-drilling operations.
Once contaminants have percolate through the soil to reach the ground water, several factors influence the movement of contaminants in a aquifer, including the solubility and density of the contaminant and groundwater movement.
Some contaminants, such as salts, readily dissolve in water, while others like perc and many other organic materials are relatively insoluble. In general, a contaminant with low water solubility has low mobility in groundwater.
Insoluble substances that are lighter than water, such as hydrocarbons, will float on top of an aquifer and can spread through a large area as a thin film. Perc and other heavier insoluble substances tend to sink to the bottom of the aquifer and follow the slope of the confining layer.
Groundwater, and the contaminants within it, tend to move very slowly, with a typical flow rate of 100 feet per year. At such a rate, very little mixing or dispersion of contaminants occurs. As a result, even small amounts of solvent released at the surface can result in a measurable amount of contamination.
Moreover, contaminants tend to stay localized and form distinct plumes that gradually spread outward from the source. Consequently, two samples drawn from the same aquifer may show radically different concentrations.
Once a contaminated aquifer has been detected, it is necessary to decide what action, if any, should be taken. In a recent report, the National Research Council concluded that cleanup of contaminated groundwater is often not feasible. While natural dilution and microbial degradation of the contaminants does occur, these processes generally take a long time. When deciding whether, and to what extent, remedial action is appropriate, several factors come into play.
These factors include:Evaluating these and other parameters can assist planners in determining the potential threat to human health and the environment and, in so doing, prioritize the need for remediation among various contamination sites. In some cases, however, remediation may not be technically, possible. Furthermore, because of the variety of factors, costs can range from several thousand to several million dollars. Clearly, contamination remediation must be decided on a-case-by-case basis.
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Date created: 95.10.16 Last modified: 95.10.16 Hal Horning hhorning@pond.com