Electrical Resistance Heating—Lockformer ERH Case Study

The Lockformer Company located at 711 W. Ogden Ave in Lisle, Illinois is currently conducting a Superfund Removal Action pursuant to a Unilateral Administrative Order which was issued by U.S. EPA. Lockformer and their consultant Clayton Group Services and subcontractor Thermal Remediation Systems have proposed to utilize Electric Resistive Heating (ERH) in conjunction with Soil Vapor Extraction (SVE) to remediate soil which is contaminated with Trichloroethylene (TCE).

The selection of ERH was proposed by Clayton after the initial review and proposal to use dig and haul technology with off-site disposal. Off-site disposal of TCE contaminated soil is limited due to land disposal restrictions and high costs for incineration. On-Site thermal desorption was not considered due to the large volume of contaminated soil and proximity to residences. Delineation sampling indicated soil contamination above the Removal Action Levels to depths greater than 50 feet which are beyond the limits of soil excavation.

The upper clay till/fill which is above the removal action objective of 8.9 ppm of TCE will be treated in-situ using the ERH technology. Soil Vapor Extraction (SVE) has been proposed to remediate the TCE contaminated soil in the underlying sand and gravel unit. The Lockformer Work Plan was approved by U.S. EPA in September of 2002 and a pilot scale SVE system was installed and operated and full scale design of the ERH system and SVE system have been submitted and are under review.

The governmental parties and their contractors provided a detailed comments regarding air monitoring of all of the systems due to the close proximity of neighboring residents. Lockformer and Clayton will provide continuous hydrocarbon analysis of stack emissions along with vapor phase monitoring of the off-gas treatment system (granular activated carbon). Additional air monitoring will include, work zone monitoring with a Miran spectrophotometer, site perimeter and neighborhood monitoring will be conducted with summa canisters during system operation. This detailed air monitoring plan will ensure protection to the Lockformer employees and neighboring residents.

The governmental parties and their contractors provided detailed comments on the Lockformer Work Plan to monitor the ERH systems. Of particular concern was the installation of monitoring probes to sense temperature and vapor migration in the area where ERH treatment will be conducted. This monitoring will be conducted to evaluate lateral or horizontal migration of TCE vapors. The governmental parties demanded the operation of the SVE system in conjunction with ERH to extract any vapors which may migrate horizontally or vertically. The installation of a plenum constructed of asphalt with horizontal vapor extraction pipes was designed to minimize any vapor migration to the atmosphere. These controls were all necessary due to the protection of Lockformer employees, residences, and remediation workers.

The delineation of the horizontal and vertical extent of contamination prior to conducting ERH or SVE is critical in treating contaminated soils in-situ. Lockformer and their consultant Clayton Group utilized a conventional drill rig and grid sampling to delineate the TCE contamination. The use of direct push technology using membrane interface probes (MIP) mounted or soil gas probes may be utilized to minimize costs and speed the delineation of the contaminated areas.

Conclusion

The use of Electric Resistive Heating in conjunction with Soil Vapor Extraction to treat TCE contaminated soil in-situ has been proposed and approved by U.S. EPA at the Lockformer Removal Action. The initiation of monitoring and engineering controls to evaluate and prevent lateral or vertical movement of the TCE vapor phase was a major concern of the regulatory agencies involved in this project. Air Monitoring of the stack emissions, site work zones, perimeter and neighborhood will be required during the operation of the systems to assure proper health protection to the Lockformer employees, neighboring residences, and remediation workers. Safety fail safe procedures such as perimeter fencing, security, and ERH zone fencing with shut down systems are necessary to prevent any accidents during the remediation. Previous case studies presented to U.S. EPA have shown that the ERH technology is capable of treating similar low permeability soil down to the Removal Action Objective chosen for this site (8.9ppm for TCE). The ERH system is currently being installed at the Lockformer site and should be operational by March of 2003.