This site, located in Belle Gardens California was a former automotive service station. This facility, like many others in the United States, suffered from leaking underground storage tanks. The station was shut down, the tanks were removed and the site needed to be cleaned up. State and federal regulations normally require that contaminated soil must be cleaned or properly disposed of. In many cases, this one included, cleaning the soil was far less costly.
The site survey indicated that the volatile organic compounds (VOC's) were relatively high. A network of perforated pipes were installed in the contaminated soil. This would allow the VOC's to be removed from the soil using a process known as "Vapor Extraction". The first stage of the cleanup would involve using a thermal oxidizer to burn the hydrocarbons. As the VOC levels decrease, final site cleaning will be completed using carbon beds.
The thermal oxidizer was connected to the perforated pipe network. This device incorporates a large container of sand. The sand has electric calrod heaters that run through it. During initial startup, the bed of sand is heated to a very high temperature. At that point, the vacuum blower is started. The vacuum draws air through the contaminated soil removing the VOC's. This mixture of air and VOC's enter the heated bed of sand and burn, producing a substantial amount of heat. This heat keeps the sand hot enough to sustain the burning process without the use of the electric heaters. The thermal oxidizer is equipped with several valves. Two or more of the valves of the valves channel the inlet flow of the air and VOC's to different sides of the sand bed. This keeps the bed at a uniform temperature. The most important valve is the mixing valve, which acts like a carburetor on a car. The mixture must be adjusted so that the proper levels of VOC's are admitted to sustain the process, but not so many that combustion is incomplete.
R. L. Shields Associates was chosen to equip the thermal oxidizer with a controller for monitoring and controlling the clean-up process. The controller chosen was a Delta Controls Mini Controller. This allowed for off-site monitoring and control. Additionally, if an exception condition occurs, the operator could be paged to resolve the problem.
The controller was responsible for operating the various valves as well as monitoring the temperatures and datalogging. Site management requirements require extensive data for the state and federal authorities to show the progress of the cleanup. The Delta Mini Controller excelled in this area, logging temperatures, vacuum levels, etc. This information was later downloaded via telephone lines to A&M's computers to formulate the reports.
Following site closure, the equipment will be relocated to another site and the software will be customized for the next remediation project.
For more information on this project or Delta Controls, contact:R. L. Shields Associates, Inc.
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