Case Study: Dry Cleaners Site, Southern California
CL-Out® bioremediation was implemented at a dry cleaners in southern California to remove dry cleaning solvents from soil and ground water. After one application of CL-Out® bioremediation the total chlorinated solvents concentration in ground water was reduced by 90%. The contaminant concentrations in soil were also reduced by an average of 85%. The remediation provided immediate risk reduction including avoiding vapor intrusion by vinyl chloride
Project Design and Implementation
The dry cleaning solvent was found in an area around a dry cleaning machine. The solvent entered the soil below the building and percolated through the soil to a perched ground water zone and an underlying second ground water zone. The soil and sediments are interbedded alluvial and marine sediments with a high permeability. The site was close to the beach, and ground water is influenced by tidal fluctuations. The impacted soil volume was approximately 80 cubic yards. The area of ground water impact and treatment was approximately 2,000 square feet.
Based on the volumes of impacted soil and ground water, five drums of hydrated CL-Out® were used. Two drums were injected into the soil and perched ground water beneath the dry cleaning machine. Three drums were injected into the deeper ground water in the diffused area of the plume. The total injection volume was less than .1% of the pore volume of the treated soil and ground water.
CL-Out® bioremediation destroys chlorinated solvents by aerobic cometabolism. Dextrose was added to provide the carbon source to support microbial growth. EHC-OTM by Adventus was added to maintain the aerobic conditions to support cometabolism and prevent potential production of vinyl chloride by indigenous bacteria.
Post –treatment soil and ground water samples were taken approximately 30 days after the injection. The post-treatment soil samples were taken from locations adjacent to pretreatment sampling locations. The shallow soil samples all showed a decrease in solvent concentrations and no vinyl chloride was generated. Post-treatment ground water samples were obtained from existing monitoring wells and compared to previous sampling results. The perched ground water showed a decrease in PCE concentrations but a slight increase in TCE and DCE concentrations. The deeper ground water showed a decrease in all concentrations. Vinyl chloride was not detected in either the perched or deep ground water. The following table shows the contaminant concentration treads.
The 30-sampling results show that the site is progressing toward fast closure. Additional ground water treatment is unlikely to be necessary to achieve site closure after sufficient post-treatment monitoring.