Installation Date:
03/01/1996

Contaminants:
Trichloroethene

Reactive Media:
Fe⁰

Construction:
Horizontal Well

Point of Contact:
Thomas C. Houk
Portsmouth Gaseous Diffusion Plant
Tel: 614-897-6502
Fax: 614-897-3800
Email: uk9@ornl.gov
3930 US Route 23S
Piketon , OH 45661

A pilot-scale field test of reactive media (zero-valent iron) for degrading trichloroethylene (TCE) in ground water is currently in place at the X-625 Groundwater Treatment Facility at the U.S. Department of Energy's (DOE) Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. Influent concentrations of TCE for the treatment facility range from 70 to 150 µg/L. Contamination resulted from past waste disposal practices at the plant.

The uppermost layer underlying the site is composed of approximately 30 ft of silt. The contaminated aquifer resides below this layer within a 2- to 10-ft layer of silty gravel and has a hydraulic conductivity of approximately 20 ft/day. Bedrock is 32-40 ft below ground surface (bgs).

The X-625 facility consists of a 500-ft horizontal well that collects TCE-contaminated ground water from within the silty-gravel aquifer underlying the treatment area at a depth of 30 ft. This ground water is fed into a building constructed at an elevation that is 3-5 ft below bedrock. The ground water then is distributed through a series of canisters filled with zero-valent iron (Fe⁰). The flow rate into the facility has been less than 1gpm. The facility is currently being converted to accommodate a higher ground-water flow rate (5 gpm). After conversion, treatment will be through zero-valent iron in the form of foamed pellets. Electrochemical enhancement by passing a current through the iron media also is being considered.

Testing of the Fe⁰ filings was conducted from March 1996 through March 1998. Results indicated a reduction of TCE concentrations to less than 5 µg/L after passage through the treatment system. Reductions in the hydraulic conductivity of the iron media due to mineral precipitation (e.g., iron oxides and iron sulfides) were observed. The life of the reactive media will be dependent on high Fe⁰ corrosion rates influenced by the high sulfate levels in the ground water.

Future sampling plans will be developed during conversion to the higher flow rate, which is expected to be completed by October 1998.

SITE-SPECIFIC REFERENCES