Site Name:

Portsmouth Gaseous Diffusion Plant

Location:

Piketon, OH

Period of
Operation:

Spring 1997 (operated for one month)

Cleanup
Type:

Field demonstration

Technology:
In Situ Chemical Oxidation
- Demonstration used a pair of parallel horizontal wells - one to extract groundwater (6 gpm) and one to reinject after addition of potassium permanganate (KMnO₄)
- Each well had a 200 ft screened section located in a 5 ft thick silty, gravel aquifer in the center of a plume
- Crystalline KMnO₄ was added to the extracted groundwater and reinjected into the downgradient well 90 ft from the extraction well; a total of 206,000 gals of KMnO₄ solution was injected
- Oxidant solution (~2% KMnO₄) was recirculated for one month
- Delivery of oxidant solution was not uniform throughout the horizontal well; a subsequent injection of KMnO₄ was made into a nearby vertical well for 8 days to enhance delivery
- System shutdowns were due to heavy rains, well-screen clogging, and repairs

Cleanup Authority:
RCRA Corrective Action

Contaminants:
Chlorinated solvents
- Initial TCE concentrations in groundwater averaged 176.7 mg/L

Waste Source:
Leaks from USTs

Type/Quantity of Media Treated:
Groundwater (in situ)
- The Gallia sand and gravel unit was the target for the demonstration
- DNAPL compounds (mostly TCE) were located 25-35 ft bgs, 12 ft below top of water table
- Area of contamination approximately 90 ft by 220 ft by 6 ft (119,000 ft³) containing 272.7 lbs of TCE

Purpose/Significance of Application:
Demonstrate in situ chemical oxidation for treating chlorinated solvents

Regulatory Requirements/Cleanup Goals:
- Evaluate performance of the technology in degrading TCE
- No specific cleanup goals were identified

Results:
- Average concentrations of TCE were 176.7 mg/L before treatment, 110 mg/L at completion of treatment, and 41 mg/L two weeks after recirculation ended; concentrations increased to 65 mg/L at 8 weeks and 103 mg/L at 12 weeks after recirculation ended
- Immediately after recirculation ended, concentrations of TCE were low (BDL to low ug/L) in monitoring wells where KMnO₄ was also detected
- Residual concentrations of KMnO₄ were detected at nine monitoring well locations 19 months after the demonstration ended

Cost Factors:
- The estimated cost for the demonstration was $562,000, consisting of project management ($67,440), pre-demonstration characterization ($162,980), remediation operations/oxidant recirculation ($162,980), resistivity monitoring ($67,440), and post-demonstration characterization and demobilization ($101,160)
- Projected costs for use of the technology at a full-scale were $516,360, to treat a hot spot area of 22.9 acres in the central portion of the X-701B plume; this corresponds to $64/yd³

Description:
The Portsmouth Gaseous Diffusion Plant (PORTS), located 80 miles south of Columbus, Ohio, is a 3,714-acre DOE reservation. It was constructed between 1952 and 1956 and enriches uranium for electrical power generation. The X-701B site, located in the northeastern area of PORTS, contains an unlined 200 ft by 50 ft holding pond. The pond was used from 1954 to 1988 for neutralization and settling of metal-bearing acidic wastewater and solvent-contaminated solutions. During a RCRA Facility Investigation, TCE was detected in a groundwater sample at 700 mg/L.

A field demonstration of in situ chemical oxidation was conducted at PORTS using a pair of parallel horizontal wells one for extraction and one for reinjection. Crystalline KMnO₄ was added to extracted groundwater and reinjected into the downgradient well 90 ft from the extraction well; a total of 206,000 gals of KMnO₄ solution was injected and recirculated for one month. Results showed that immediately after recirculation ended, concentrations of TCE were low (BDL to low ug/L) at those locations where KMnO₄ was detected in the monitoring well. However, oxidant addition was not uniform and average concentrations were higher - 110 mg/L at completion of treatment, and 41 mg/L two weeks after recirculation ended. The researchers concluded that the number and pattern of extraction and injections wells must be designed to ensure maximum coverage of the treatment zone.

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