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Halby Chemical

Wilmington, Delaware
Fact Sheet: December 1996

What is that smell?

Beginning on December 10, 1996, the Witco Corporation (Witco), a former owner of the Halby Chemical Site on Terminal Avenue, will begin test treating contaminated soil from the former lagoon area at the site. EPA and the Delaware Department of Natural Resources (DNREC) will oversee the treatment process. Although the process will include air emission controls, residents may notice unpleasant odors that result from the site contamination and the treatment process. The odor results from sulfide chemicals and is similar to rotten eggs. This smell is not harmful, just unpleasant.

The soil treatment study is scheduled to begin on December 10, 1996, and end on December 20, 1996.

Cleanup activities at the site


During many years of operation at the site, 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 which must be removed from the soils so that the property may be safely utilized.

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, mainly by bringing oxygen into contact with the chemicals.

Soil Treatment

As part of the on-going site clean-up plans, Witco soon will conduct a small-scale treatment project at the site. EPA and DNREC will oversee and monitor Witco's clean-up activities. 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.

Witco first will treat contaminated areas at the site approximately three feet wide, 12 feet long, and 12 feet deep, by exposing the soil to oxidizing chemicals. The oxidation process will transform the carbon disulfide into harmless compounds, such as carbon dioxide and sulfate salts.

Sulfide chemicals present during intermediate steps of the treatment process can be smelled. Witco also will place a hood, similar to a large tarp, over the test area to capture any gases that result from treating the soil. Witco will treat the gases 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 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 and will shut down operations if potentially harmful conditions occur.


If you have any questions or comments about the treatment project during site operations, please contact EPA at the office located at the Halby Chemical Site. Someone will be available to answer your questions during normal business hours; Monday through Friday, 8:00 a.m. to 5:00 p.m. The telephone number to EPA's on-site trailer is 1-302-427-8625

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