Pump and Treat with activated sludge for extracted groundwater; in situ bioremediation for contaminated groundwater
- Active remediation conducted from January 1992 through December 1995 consisted of extraction and above-ground treatment, enhanced aquifer flushing through pressure injection of clean water, and accelerated in situ bioremediation through the addition of oxygen, phosphorus, and nitrate.
- Source control was achieved by installation of cutoff (sheet-pile) walls around lagoon and DNAPL source areas.
- Since December 1995, active pumping was stopped and natural attenuation has been used to reduce remaining concentrations of contaminants. Limited pumping began in March 1998.
- ROD Date: 3/24/88
|EPA Point of Contact:|
Ernest Franke, RPM
U.S. EPA Region 6
1445 Ross Avenue
Dallas, TX 75202-2733
State Point of Contact:
ARCO Chemical Company
FLTG Project Coordinator
15010 FM 2100, Ste. 200
Crosby, TX 77532
Chlorinated solvents and Volatiles - nonhalogenated
- Contaminants of concern in the groundwater were benzene, toluene, chloroform, 1,2-DCA, and vinyl chloride
- Initial maximum concentrations were benzene (19,000 mcg/L), 1,2-DCA (920,000 mcg/L), and vinyl chloride (8,200 mcg/L)
Unlined disposal pit (lagoon)
Type/Quantity of Media Treated:
- 306 million gallons of groundwater and surface treated as of December 1995
- Groundwater is found at 10-12 ft bgs
- Extraction wells are located in two aquifers
- Hydraulic conductivity ranges from 0.283 to 2.835 ft/day
Purpose/Significance of Application:
Regulatory requirements for this site based on use of modeling results to show effects of natural attenuation at the site boundary 10 years after pump and treat completed.
Regulatory Requirements/Cleanup Goals:
- According to the 1988 ROD, "groundwater recovery and treatment will continue until modeling shows that a reduction in the concentration of volatile organics to a level which attains the 10-6 human health criteria at the site boundary can be achieved through natural attenuation in 10 years or less." In response, remedial goals were established for vinyl chloride (2 mcg/L), benzene (5 mcg/L), toluene (1,000 mcg/L), 1,2-DCA (100 mcg/L), and chloroform (100 mcg/L).
- A primary goal of the remedial system was plume containment, accompanied by in situ bioremediation and source control using sheet-pile walls.
- A modeling study conducted in late 1995 demonstrated that natural attenuation would reduce groundwater contaminant concentrations below the remedial goals at the site boundary within 10 years after system shut-off. As a result, EPA allowed the groundwater recovery and treatment operations to be shut down in December 1995.
- Average concentrations of 1,2-DCA, vinyl chloride, and benzene had been reduced to approximately 1 ug/L in the twp aquifers at the site by October 1995. As of December 1995, the pump and treat system had removed 517,000 pounds of contaminants (measured as TOC) from the groundwater. No data were available to quantify the amount of contaminants destroyed through bioremediation.
Actual costs for pump and treat and in situ bioremediation were $33,689,000 ($15,487,000 in capital and $18,202,000 in O&M), which correspond to $110 per 1,000 gallons of groundwater extracted and $15 per pound of contaminant removed. The unit cost does not account for the amount of contaminants destroyed through bioremediation.
The French Limited site was used for sand mining in the 1960s and 1970s. During the period from 1966 through 1971, the site was permitted to accept industrial waste material for disposal in a seven-acre lagoon created from an open sand pit. About 80 million gallons of waste material was disposed of in the main waste lagoon. The facility's permit was revoked and the site was closed in 1973. The site was placed on the NPL in 1981, and a remedial investigation was performed at the site from 1983 to 1986 through a cooperative agreement. A ROD was signed in May 1987, and amended in March 1988.
Active remediation was conducted at the site from January 1992 through December 1995 by groundwater extraction and above-ground treatment, enhanced aquifer flushing through pressure injection of clean water, and accelerated in situ bioremediation through the addition of oxygen, phosphorus, and nitrate. Source control was achieved by installation of sheet-pile walls around lagoon and DNAPL source areas. As of December 1995, active pumping was stopped and natural attenuation has been used to reduce remaining concentrations of contaminants. Limited pumping began in March 1998.