The International Information Center for Geotechnical Engineers

Thermal Desorption - Case Study: 34 Freeman's Bridge Road

History and Contamination

Located in Glenville, New York, the site is in an area comprised of both residential and commercial land uses. From the late 1940’s to 1972, the area was used by Kitchton Cooperage Company, which specialized in recycling drums and other containers from local industries. Usually containing nonhazardous waste, the barrels were emptied, repainted and prepared for reuse. When Kitchton sold the land in 1978, the next owner, Lyon’s Ventures, Inc. continued to use the land for waste disposal, but began accepting hazardous waste in addition to construction wastes and debris (Desnoyers, 2004).

 

In 1984, the New York State Department of Environmental Conservation (NYSDEC) deemed the site dangerous and considered it to be a Class 2 disposal site by the Registry of Inactive Hazardous Waste Disposal Sites. This classification was mostly due to the 80, 55-gallon drums of hazardous waste, which were stored on the property. Lyon’s Ventures, Inc. claimed to have properly disposed the drums at the direction of the NYSDEC and the classification was removed. Yet, in 1989, 80 “new” drums were discovered on the property, and the NYSDEC removed the drums and fined the owner. At this point, the site was considered to be safe since the drums no longer existed on the property (Desnoyers, 2004).

 

By 1996, the property was being considered for commercial development. When the area was investigated for potential contamination due to its questionable history, excessive contamination was discovered in the form of polychlorinated biphenyls (PCBs) in concentrations of 100 ppm or more in different areas of the property. Needless to say, commercial development was impossible under the current site conditions. The NYSDEC ordered an Immediate Investigation Work Assignment in June of the same year, and several test pits and monitoring wells were installed around the site. The results showed the PCBs existed in the surface soils (top 2 feet of soil strata) at concentrations of 33 ppm and in subsurface soils at 980 ppm. Overall in addition to PCBs, wastes around the site included volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), and metals. The groundwater was found to have wastes in the form of dissolved phase and non-aqueous phase liquids (NAPLs). The site was re-listed as a Class 2 site on the registry in December of 1996 (Desnoyers, 2004).

 

The site is located on the flood plain of the Mohawk River, which comes within 90 meters of the property line at its closest point (see Figure 5, below). The Mohawk River is considered a suitable drinking source, so remediation of the site was imperative. The soil stratum of the site includes fill at the top, fine-grained alluvium below, deep sand, glacial till, and finally bedrock. The fill is considered to be the major zone of contamination from the dumping while the area was owned by the Kitchton Cooperage Company (Desnoyers, 2004).

 

4

Figure 5: Aerial photo of 34 Freeman’s Road (Floess et al, 2011)

 

Remediation Solution and Design

The primary goals of the remediation process were to eliminate or acceptably reduce the exposures of people at the site to contaminants, and the migration of the contaminants into the greater environment. Thermal desorption was chosen as the best option due to an estimated small amount of contaminated materials transported on public thoroughfares, low landfill volume needed for disposal, and its comparable costs to other possible remediation methods (Floess et al, 2011).

 

In order to design an appropriate remediation plan, the distribution of the contaminants was mapped. First, concentrations of contaminants were measured by means of test pits and borings, along with geophysics to locate buried drums. A 50 foot by 50 foot grid was placed over the entire property and 2 foot vertical increments were extended below the ground surface. This created 50 by 50 by 2 foot boxes, which were categorized based on the concentration of contaminants. These categories included “Clean,” “Nonhazardous” for concentrations of PCBs less than 50 ppm, “Hazardous” for concentrations of PCBs greater than or equal to 50 ppm, and “Metals Containing Soils” for areas which were not treatable by thermal desorption. 50 ppm was chosen as the cutoff because the Toxic Substances Control Act (TSCA) defines concentrations greater than 50 ppm as hazardous. The treatment specifications for thermal desorption depend on whether the material is considered hazardous by the TSCA. About two-thirds of the contaminated volume was considered “Nonhazardous,” one-sixth was considered “Hazardous,” and the remaining sixth was considered to be “Metals Containing Soils” (Floess et al, 2011).

 

Environmental Soil Management, Inc. (ESMI) was hired to remediate the “Nonhazardous” soils and TD*X Associates, LLP was hired to remediate the “Hazardous” soils. Both firms were subcontractors to D.A. Collins Environmental Services, Inc. (Floess et al, 2011).

 

ESMI used direct heated thermal desorption to remove the contaminants. The material was fed into the rotating cylinder with a gas-fired burner which was heated to 510⁰ C at its entrance. The organic contaminants were transferred with the hot gas to an attached treatment system where it was filtered to release the hot gas and treat the contaminants. They were treated by a direct fired oxidizer to reduce them to carbon dioxide, water and a small amount of hydrochloric acid. The treated material was tested to ensure quality before being backfilled into the excavated area. ESMI successfully treated the materials to below the target ranges of less than 1 ppm total PCB and less than 10 ppm total carcinogenic SVOCs and total VOCs (Floess et al, 2011).

 

TD*X used indirect heated thermal desorption to treat the “Hazardous” soils. Like the direct thermal desorption, the material was fed into a dryer, except the entire cylinder was heated within a furnace so the material was heated by conduction. An inert nitrogen atmosphere was employed to transfer the contaminants to an attached gas treatment unit. There, they were condensed to a liquid so that they could be disposed of at a TSCA approved offsite facility. The gas treatment attachment also produced several extra byproducts: the non-condensable oxygen was recycled through the system for odor control and condensed water from soil moisture was used to cool the machinery. Nitrogen had to be added periodically to keep the balance of nitrogen and oxygen equal within the dryer. The treated soil was also tested to ensure quality control before being backfilled. TD*X also reached the target contamination goals of the project (Floess et al, 2011).

 

TD*X experienced problems with their design after a short amount of time. Due to roofing materials disposed in the dump, the condensed contaminants included a tar-like substance, which clogged the condensing machinery. TD*X developed a solution with their equipment, however it was found to increase cost and time of the remediation project. Based on these factors, the NYSDEC decided to simply transport the material for offsite disposal, contrary to the original plan (Floess et al, 2011).

 

Conclusion

Several sustainability factors were examined during the remediation processes, comparing the thermal desorption method to a simple landfill disposal method. These factors included emissions from fuel consumption, energy consumption, work accidents, and dust emissions. The study showed that thermal desorption used considerably more fuel (and resulted in more fuel emissions) than had the material simply been trucked to a landfill. However, accidents were considered to be much lower with thermal desorption assuming driving accidents could be considerably diminished. In addition, landfill space preservation and less roadway use was also viewed as a large advantage with this method (Floess et al, 2011).

 

The direct thermal desorption proved to be a very successful and viable option for remediating contaminated sites like 34 Freeman’s Bridge Road. Due to the unexpected roofing materials mixed in with the other contaminants, the indirect thermal desorption was not a satisfactory remediation technique for the “Hazardous” material. Had this waste been excluded from the project, the implementation would have been much more successful.

 

Add comment

NOTE: The symbol < is not allowed in comments. If you use it, the comment will not be published correctly.

Security code
Refresh
*Please insert the above-shown characters in the field below.