No Use Crying Over Spilled PERC
The Ohio Voluntary Action Program gives companies a simpler solution for cleaning up brownfields.
- By Joe Lorenz, David Vicarel
- Dec 01, 2004
PCE--the acronym used in the hazardous materials industry for tetrachloroethene--is a common dry-cleaning solvent that does wonders for getting clothes clean. Unfortunately, it can wreak havoc on the environment. That is exactly what the owner of a neighborhood shopping mall in Ohio found out when selling the property.
A previous dry cleaner disposed waste fluid containing PCE into floor drains inside the shopping center, and in the early 1980s a PCE supplier spilled some of the chemical onto the parking lot outside the building while refilling the dry cleaner's PCE tank. The PCE leaked from the underground drain lines. Because it is heavier than water, it also penetrated cracks in the asphalt pavement.
When it came time to sell the property in 2000, the prospective buyer chose to conduct a standard environmental assessment, and PCE was discovered in soil and groundwater on the property. The process of having an assessment completed before purchasing a commercial property is an important step because purchasing a site also means purchasing the environmental liability, if any, associated with the property.
When the potential buyer backed out of the sale because of the environmental hazards, the owner of the property elected to remediate the property under the Voluntary Action Program. (VAP provides guidelines for investigating and remediating property without direct involvement of the Ohio EPA. When Ohio EPA is satisfied applicable cleanup standards have been achieved at a property, it grants a No Further Action Status for the property and issues a Covenant Not to Sue to the property owner, stipulating that the state will not require further environmental work at the property as long as the property use does not change significantly.)
In addition, by choosing to address the situation voluntarily, the shopping center's owner avoided a more costly remediation effort down the road by eliminating the potential for the PCE to spread across the site as groundwater flowed away from the spill area.
The property owner contracted with an environmental and design engineering consulting firm to confirm the findings of the buyer's environmental assessment and to devise a plan for remediation. The evaluation revealed not only was PCE in the soil beneath the former dry cleaner, but also there was a plume of PCE in groundwater that was moving toward a residential neighborhood.
The consultant developed the plan and defined the scope and parameters for remediation. The firm recommended an environmental contracting company to conduct the actual excavation, and that firm was chosen to remove the contaminated soil after a review of numerous bids for the project. The consultant's role was to manage the overall project, evaluate soil and groundwater analytical data, prepare reports, and communicate with Ohio EPA.
As in most environmental cleanup projects requiring excavation, the true extent of the PCE-containing soil could not be fully ascertained until the actual digging began. Factors such as the type of soil, geology, and the direction and speed of the groundwater had an impact and could not be assessed until ground was broken. Digging began at the source area, or the area where the PCE spill actually occurred. From there, the crew excavated until all PCE-containing soil was removed.
During a project, both the environmental engineer and the environmental contractor must have the experience to react to situations as they are uncovered. In the field, workers often have to come up with innovative solutions to unique circumstances as they arise, and the shopping center project presented a few of its own.
Because the source area was known, the crew was able to begin excavating there. The back walls of the store were removed and digging began. However, the PCE-containing soil extended further into the ground than originally assumed; the team needed to remove earth to depths of approximately 12 feet below ground. The excavation process took approximately three months to complete.
Above Ground Matters, Too
Even while the state of the ground below a site affects the project, so do structural features of buildings on the site. With the shopping center project, the actual footprint of the former dry cleaner measured about 60 feet wide by 150 feet long. This dictated the type of equipment that could be used for the job.
In particular, ceiling heights of only 12 feet made it impossible to use regular-sized excavation equipment. The excavation crew used mini-excavators to do the actual digging. Two types of buckets were employed to move soil from the excavation area to trucks waiting outside and then safely to a hazardous waste landfill.
Another challenge presented itself when the crew discovered the contamination in the soil extended beyond the physical walls of the building. Because the structural integrity of the walls needed to be preserved, digging underneath the walls was performed section by section. Excavation moved around the perimeter of the building, one area at a time. At each step, sections of the wall had to be secured before digging took place beneath the wall footers to prevent the walls from sagging or being damaged. The crew dug underneath the existing footers, supported the roof beams, and poured new concrete footers to support the walls. After work was completed in one area, the footers were secured and backfilled before exposing another section of the wall.
During this process, a soil vapor extraction system was added to help vent PCE vapors that could migrate into the shopping center building.
To address PCE in groundwater, the consultant installed a remediation system and deployed a patented enhanced bioremediation technology to convert the PCE and its breakdown products into innocuous end products. Groundwater remediation began in August 2002; by August 2004, the system had remediated groundwater across nearly the entire site. Remediation is expected to be completed in 2007, if not sooner.
Putting Safety First
In any environmental hazard remediation, safety is a concern. Safety issues are heightened with PCE because the chemical is volatile and, when exposed to air, produces vapors that can be hazardous. In addition to following all precautions and meeting all standards set forth by OSHA, the two firms took additional precautions to ensure the safety of work crews, shoppers, and employees inside the mall.
Because the excavation site also was the site of an active mall, it was critical to manage the area carefully and avoid spreading PCE waste, vapors, or fumes.
The first step was completely enclosing the excavation site with heavy plastic sheets. A negative-pressure environment was created to keep vapors from entering the mall through air vents and to protect the workers within the site. Air quality was monitored continuously during the excavation. This ensured the workers were protected and were required to wear respirators only when airborne PCE concentrations reached hazardous levels.
The workers also had vapor-suppressing foam on site in the event significantly elevated PCE concentrations were detected in the work area. Spraying the foam on the soil eliminates PCE-containing vapors. At the end of each workday, the crew sprayed the foam on any area of exposed soil to help prevent vapors from building up during the night.
Throughout this complicated environmental cleanup, many factors helped ensure a successful outcome. First, the choice of the property owner to address the problem voluntarily was critical. The ability of consultant and contractor to react to challenges in the field throughout the project was key. And, of course, safety was crucial.
Today, the property owners can look forward to an environmentally safe site that should present no hazards to future sales.
This article originally appeared in the December 2004 issue of Occupational Health & Safety.