Pasco Sanitary Landfill (PSL)

The Pasco Sanitary Landfill (PSL) is located near Pasco, Washington and covers an area of 250 acres. It has a history of open burning dumping from 1958 to 1971, followed by sanitary landfilling starting in 1972. The landfill area was not lined, and hazardous wastes were also disposed of on part of the site between 1972 and 1975. As a result of these activities, the groundwater beneath and downstream of the site has been contaminated with volatile organic compounds (VOCs).

To address the contamination, a remedial investigation was conducted, which included the implementation of a Soil Vapor Extraction (SVE) system. The SVE system involves drilling extraction wells into the contaminated soil above the water table. The depth of these wells varied between 20 to 30 feet. The wells are equipped with a blower or vacuum pump that creates a vacuum, and they are heated to a temperature of 1500 degrees using a conductor. This vacuum pulls air and vapors through the soil and up the wells to the ground surface for treatment. On-site, there is a treatment plant where the vapors are treated before being transported.

To ensure the efficiency of the cleanup process, it is important to prevent the vacuum from pulling in clean air from above. This is achieved by paving or covering the ground with a tarp. Additionally, a vapor barrier is placed directly over the soil, and Class II Cellular Concrete is used as insulation at a depth of 15 inches. This insulation material has a high air content, providing significant insulating properties. A Class V cellular concrete with a strength of 300 PSI is used as a working surface to allow for equipment maneuverability and the extraction process.

Overall, the SVE system and the use of cellular concrete help to ensure worker safety, maintain temperature control, and facilitate the efficient extraction and treatment of vapors from the contaminated soil at the Pasco Sanitary Landfill.