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Halby Chemical

Fact Sheet: April 1997

Treatability Study Update

Beginning on April 14, 1997, the Witco Corporation (Witco), a former owner of the Halby Chemical Site on Terminal Avenue, will continue testing treatment methods to address the contaminated soil from the former lagoon area at the site. Phase One of the treatability study, conducted in December 1996, involved treating the contaminated soil with an oxidizing chemical. Phase Two will run through mid-May1997.

The U.S. Environmental Protection Agency (EPA) and the Delaware Department of Natural Resources and Environmental Control (DNREC) will oversee the treatment study. The study includes air emission controls, however, residents may notice unpleasant odors resulting from the site contamination and the treatment process. The odor comes from sulfide chemicals and is similar to rotten eggs. This smell is not harmful, just unpleasant. The Phase One study activities did not produce an odor.

The soil treatment study is scheduled to begin on April 14, 1997, and end in mid-May 1997.

Clean-Up Activities At The Site

Background

During many years of site operations, carbon disulfide spilled into an on-site lagoon. Carbon disulfide is a heavy chemical that, like oil, does not mix with water. Because the carbon disulfide is heavier than water, it sank to the bottom of the lagoon and seeped into the soil below. Carbon disulfide is a hazardous compound that must be removed from the soils to improve the environment so that the property may be reused safely.

Laboratory experiments have shown that carbon disulfide can be removed from the soil by a treatment process called oxidation. The treatment process changes the carbon disulfide into two harmless compounds, carbon dioxide and sulfate salts, by bringing oxygen into contact with the chemical.

Soil Treatment

As part of the on-going site clean-up plans, Phase Two of the small-scale treatment project will be implemented at the site. EPA and DNREC will oversee and monitor Witco's clean-up activities. A primary objective of the treatability study is to establish the best method for bringing the oxygen into contact with the carbon disulfide-contaminated soil. The small-scale project will help determine if the treatment process can be used on a larger scale to treat all the carbon disulfide-contaminated soils.

During Phase One activities performed in December 1996, the effectiveness of injecting the oxidizing chemical into the contaminated soil without physically mixing the soil was evaluated. Phase Two tests include mixing the soil as the oxidizing chemical is applied. This will help determine whether mixing makes the process more effective.

Contaminated areas at the site approximately 3 feet wide, 10 feet long, and 12 feet deep, will be treated by mixing the oxidizing chemical into the contaminated soil. The oxidation process transforms the carbon disulfide into harmless compounds, such as carbon dioxide and sodium sulfate.

Sulfide chemicals present during intermediate steps of the treatment process can be smelled. Witco will place a hood, similar to a large tarp, over the test area to capture any gases that result from treating the soil. The gases will be treated in an air treatment device as an extra precaution so that no harmful levels will be released. Unfortunately, people can smell sulfide compounds at concentrations thousands of times lower than harmful levels. Depending upon the wind direction, residents may be able to smell low levels of sulfides, which have an odor similar to rotten eggs.

Air Monitoring

EPA, DNREC, and Witco have arranged for roving teams of air specialists to travel throughout the community during the treatment process. These teams will collect air samples from nearby neighborhoods to ensure that harmful substances are not reaching the air in the community. In addition, Witco will sample the air at the site using a continuous air monitoring device. EPA will be at the site during soil treatment activities and will shut down operations if potentially harmful conditions occur.

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