Environmental Progress - Spring 2001

Cleaning Up Under A High-Tech Tent

Specialized technology prevents escape of VOCs

Pilings were "pushed" into place to protect the levee.

Utility company AmerenCIPS recently developed a plan to remove soils contaminated with coal tar from a property it owns in the historic river town of Beardstown. While work was still being planned, local officials contacted the IEPA to ask that steps be taken to prevent air emissions from escaping during the remediation process. After discussions with the city, the utility company and the IEPA, AmerenCIPS amended their plan to include an innovative containment structure during remediation. The tent-like structure has impervious fabric walls and roof supported by metal framing. It is 132 by 132 feet, and is designed to withstand high winds and even snow storms. To control the vapors created by the excavating, a ventilating system maintains air at a lower pressure than the surrounding air. The air is then released to the outside through filters that capture dust and vapors from the tar, as well as exhaust from the excavating vehicles.

Coal tar a legacy of gas light era

In the early 1900s, manufactured gas plants processed coal to create coal gas to fuel gas lamps and to help heat homes. The byproduct of this process was coal tar, often later placed in on-site pits which were abandoned. This residue contains carcinogenic constituents, which migrated through the soil and groundwater. One such site was in Beardstown.

Air inside the tent is filtered before release.

In the cleanup, excavated soils are placed in covered and lined trucks for transport and disposal. The wheels of the trucks are washed before leaving the site, to decontaminate them. Excavated areas are filled with clean soil.

Although not required in the plan, AmerenCIPS also chose to remediate lead-contaminated soil on another area of the property under a similar structure.

Remediation at this site, and assembly of the structure, was somewhat restricted due to the proximity of the Illinois River. It was necessary to drive sheet piling along the levee to maintain its integrity during soil excavation. The sheet piling could not be driven in by normal means, but had to be hydraulically pushed. Driving it in might have damaged the levee.

The structure will be removed when work is finished. Groundwater monitoring beneath the site is scheduled to continue for three to five years to ensure that removing the source materials effectively removed the cause of any contamination to the groundwater.

AmerenCIPS intends to use the tent at other sites. After the area is backfilled and paved, the company will regain full use of the property.