Pump and Treat
- Groundwater is extracted using 25 wells, located on- and off-site, at an average total pumping rate of 480 gpm
- Extracted groundwater is treated with oil/water separation, air stripping, and carbon adsorption, and discharged to a surface water under a NPDES permit
- ROD Date: 9/30/89
|EPA Point of Contact:|
Elizabeth Adams, RPM
U.S. EPA Region 9
75 Hawthorne St.
San Francisco, CA 94105
|State Point of Contact:|
Dr. Wei Lui
Central Coast Region
81 Higuera St., Ste. 200
San Luis Obispo, CA 93401-5427
Chlorinated solvents and volatiles - nonhalogenated
- Contaminants included 1,1-DCE, TCE, PCE, 1,1-DCA, 1,1,1-TCA, benzene, toluene, and xylene
- Maximum concentration for 1,1-DCE detected in 1983-1984 was 120 mcg/L
Accidental releases of chemicals to soil and groundwater from a RCRA-permitted facility.
Type/Quantity of Media Treated:
- 1,800 million gallons treated
- Groundwater is found at near ground surface at the site
- Extraction wells are located in 3 aquifers, which are influenced by production wells in the area
- Hydraulic conductivity ranges from 100 to 1,200 ft/day
Purpose/Significance of Application:
Met goals within seven years of operation; site had relatively high hydraulic conductivity and was located near high-volume agricultural wells.
Regulatory Requirements/Cleanup Goals:
Remedial goals were identified based on chemical-specific ARARs that included maximum contaminant levels (MCLs) and health-based restrictions. Remedial goals were established for 1,1-DCE (6 mcg/L), 1,1-DCA (5 mcg/L), TCE (3.2 mcg/L), PCE (0.7 mcg/L), benzene (0.7 mcg/L), toluene (20 mcg/L), and xylene (70 mcg/L).
A secondary goal of the system was to prevent migration of contaminants into the adjoining property.
- 1,1-DCE was identified as the index contaminant to identify compliance with remedial goals for this site. Monitoring results showed that concentrations of this contaminant decreased from as high as 120 mcg/L in 1986 to 4.8 mcg/L in 1994 and 6 mcg/L in 1995. From 1986 to 1992, 496 pounds of total VOCs had been removed from the groundwater.
- By 1987, monitoring data indicated that plume containment had been achieved. There had been some migration of contaminants noted in 1986, but an addition of five off-site wells in the deep aquifer in 1987 prevented further migration
Actual costs for pump and treat were $12,884,813 ($4,133,543 in capital and $8,751,270 in O&M), which correspond to $7 per 1,000 gallons of groundwater extracted and $26,000 per pound of contaminant removed.
The former Firestone facility operated as a tire manufacturing plant from 1963 until 1980. During pre-closure investigations of the facility's solid waste management units in 1983, 11 areas were investigated, and results showed that soil and groundwater were contaminated. A plume of VOCs was identified in the groundwater that extended 2.5 miles down-gradient. The site was placed on the NPL in July 1987 and a ROD was signed in September 1989.
The extraction system originally consisted of 25 wells installed both on- and off-site. In July 1987, five additional wells were installed off-site in the deep aquifer to prevent plume migration, and in October 1989, five additional wells were installed off-site in the intermediate zone to treat contamination in that area. The system design was performed using a computer model. The remedial goals at this site were met within approximately seven years of treatment. Site operators frequently adjusted the extraction system to maximize the removal of contaminants from the groundwater and maintain the highest possible level of contaminants in the influent stream to the treatment system.