Installation Date:
01/08/1999

Contaminants:
Trichloroethene

Reactive Media:
Granular Fe⁰

Cost:
$200,000

Construction:
Continuous Jetted Wall with Overlapping Panels

Point of Contact:
Richard C. Landis
DuPont Corporate Remediation Group
Tel: 302-892-7452
Fax: 302-892-7641
Email: Richard.C.Landis@
USA.DuPont.com
Barley Mill Plaza/ 27-2288
P.O. Box 80027
Wilmington , DE 19880-0027

A full-scale pilot demonstration of a permeable reactive barrier (PRB) was installed at a DuPont plant in Kinston, NC in 1999. A jetted PRB design was chosen because the presence of numerous underground utilities along the wall alignment made trenching impractical. The 300-ft-wide and 800-ft-long plume contained trichloroethylene (TCE) in concentrations of 10-300 µg/L. The range of TCE concentrations in the soil was 10-100 mg/L.

The facility sits on a 650-acre site with a water-bearing zone from 5-15 ft below ground surface. The hydraulic conductivity is 0.39 × 10^-3 in/sec and the ground-water velocity range is 0.05-0.1 ft/day. The plume is in shallow sand with a delineated 30-ft × 30-ft compact source zone of unknown origin.

The PRB is 375 ft long and 15 ft deep. The center 100 ft of the PRB is 4 in thick and the wings on both sides are 2 in thick. The reactive media consists of 100 tons of granular cast iron -30/+70 mesh. In addition to the PRB, the project also featured jetting of a clay/Fe⁰ slurry directly into the source zone. Installation costs, including construction and materials, totaled approximately $200,000. This does not include treatment of the source zone.

The cleanup goal was based on the North Carolina ground-water standard of 2.8 µg/L for the plume. The source treatment reduced the TCE mass by 95%. The decrease in downgradient concentrations and the PRB performance are still under investigation. However, 13 of the 16 previously contaminated Geoprobe locations indicate non-detectable levels of TCE. Sampling is conducted quarterly.

A pump-and-treat system installed prior to 1999 and operating downgradient of the PRB is affecting the velocity through the PRB and its performance. DuPont is working out an agreement with the state to shut down the pump-and-treat system for one year in order to observe the PRB under ambient flow conditions.

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