The groundwater remediation project between two buildings near the East Gate entrance, in the area known as Operating Unit 2B, finally got underway after a long delay in startup since last spring.
During set up, one of the 30-foot-long steel electrodes driven into the ground to generate heat struck a plastic sewer line. The sewer line was not on any maps and was undetectable through scanning since it is not iron. Operation of the system began last month after a sewer line bypass was installed, and it will continue through May.
The contamination is from nearby aircraft maintenance operations that resulted in chlorinated solvents, used in cleaning aircraft parts, ending up deep underground in the groundwater. Of the three most common methods for cleaning up groundwater contaminated with solvents and fuels – pumping in neutralizing chemicals, heating up the ground to vaporize and extract the contamination, and bioremediation using microbes – the heat treatment method was chosen for this site because it is the fastest.
It takes weeks for the ground to get to the target temperature of 194 degrees, which is the temperature at which the solvent boils and turns to vapor. Pipes at ground level suck the vapor out of the ground and channel it through a large pipe to the granulated activated carbon filter system.
Other groundwater contamination nearby will be treated by a different method not yet announced. The Alameda Point electrical substation is near the other treatment area, and underground electrical lines leading every which way preclude the use of electrodes to heat the groundwater.
See also, “Cleaning up a toxic groundwater plume using heat.”