Pump and Treat
- Groundwater is extracted using 6 wells at an average total pumping rate of 60 gpm
- Extracted groundwater is treated for Cr removal with chemical treatment (ferrous ion, produced on site), pH adjustment, flocculation, precipitation, and multimedia filtration
- Treated groundwater is reinjected through 6 injection wells
- ROD Date: 9/8/86
|EPA Point of Contact:|
Ernest Franke, RPM
U.S. EPA Region 6
First Interstate Bank Tower
at Fountain Place
1445 Ross Avenue, Suite 1200
Dallas, TX 75202-2733
|State Point of Contact:|
Texas Natural Resources
P.O. Box 13087
Austin, TX 78711
Heavy Metals (Chromium)
- Maximum concentration of Cr detected during 1985 sampling event was 72 mg/L
Improper disposal practices
Type/Quantity of Media Treated:
- 125 million gallons treated as of January 1998
- Groundwater is found at 30-45 ft bgs
- Extraction wells are located in 1 aquifer, which is influenced by production wells in the area
- Hydraulic conductivity ranges from 1.7 to 5.1 ft/day
Purpose/Significance of Application:
Includes on-site treatment for chromium; relatively low groundwater flow; contamination in one aquifer
Regulatory Requirements/Cleanup Goals:
- Remediate groundwater so that chromium levels are less than the maximum contaminant level (MCL) or primary drinking water standard.
- Prior to 1990, the drinking water standard for chromium was 0.05 mg/L; in 1990, EPA revised the drinking water standard to 0.10 mg/L.
- Treated effluent that is reinjected into the aquifer must have a chromium level of less than 0.05 mg/L.
- The remedial system was required to create an inward gradient toward the site to contain the plume.
- Groundwater monitoring results indicate that chromium concentrations have been reduced compared to initial levels, but not to levels below the cleanup goal of 0.10 mg/L.
- Average chromium concentrations were reduced by 48% from January 1992 to January 1997.
- From December 1993 to 1996, 1,143 pounds of chromium have been removed from the groundwater.
- Treated effluent has met the required performance standard throughout treatment.
- Plume containment has been achieved since 1995; this was achieved after two monitoring wells were converted to recovery wells, and two other recovery wells were taken off line.
- Actual costs for the P&T application were approximately $2,742,000 ($1,954,000 in capital and $728,000 in O&M), which correspond to $30 per 1,000 gallons of groundwater extracted and $2,400 per pound of contaminant removed.
- The ROD specified that the ferrous iron used in the treatment system be produced electrochemically, which limited the number of vendors to two and potentially increased the cost of the treatment system.
- The costs for design, construction, and operation of the P&T system were split 90:10 by EPA and TNRCC, respectively.
Metal plating and chrome plating facilities operated at this site from 1954 to 1977, producing chromium- and other metals-containing wastewater. In 1977, the TNRCC investigated citizen complaints of poor drinking water quality in private wells and discovered elevated levels of chromium in the groundwater. The chromium contamination was attributed to the discharge of chromium-containing wastewater into unlined dirt ponds, directly to the soils, and into a septic tank drain field; contaminants also are suspected to have migrated to the aquifer through an abandoned open well bore on the site. The Odessa I site was added to the NPL in September 1984, and a ROD for OU 2 was signed in September 1986. OU 1, not addressed by this case study, concerned providing for an alternate water supply to replace water previously supplied by contaminated wells.
The extraction system used at this site consisted of six extraction wells constructed in the Trinity Sand Aquifer to a depth of 138 ft bgs, each with a design yield of 14,400 gpd. Extracted groundwater was treated with ferrous iron (produced on site in an electrochemical cell), pH adjustment and aeration, clarification, and multi-media filtration. While chromium concentrations have been reduced to below the MCL in three wells, as of December 1996, groundwater cleanup goals have not been achieved throughout the site.
There were several startup problems that delayed full-scale operation at this site, including clogging of injection wells and filters by iron and calcium. These problems were solved through system modification and no longer interfere with operations.