Contaminants:
a-BHC, ß-BHC, 4,4'-DDD, 4,4'-DDT, m-Xylene, o-Xylene, p-Xylene, Ethylbenzene, g-BHC (Lindane), Methyl parathion

Reactive Media:
Activated carbon

Construction:
Funnel and Gate

Point of Contact:
Annie Godfrey
USEPA Region 4
Tel: 404-562-8919
Fax: 404-562-8896
Email: godfrey.annie@
epa.gov
61 Forsyth Street
Atlanta , GA 30303

A permeable reactive barrier (PRB) was installed in August 1998 at Operable Unit 1 of the Marzone site in Tifton, GA, to remediate ground water contaminated with pesticides and volatile organic compounds (VOCs). The Marzone facility was used as a pesticide formulation facility from 1950 until the 1980s.


A 1994 Record of Decision originally selected a pump-and-treat system to remediate the ground water. During remedial design activities, however, it was determined that an in situ treatment system such as a funnel-and-gate system may be a more appropriate technology for the specific site conditions. Ground-water contaminants of concern and their initial maximum concentrations are: alpha-hexachlorobenzene (BHC) (60 mg/L), beta-BHC (98.5 mg/L), DDD (7.6 mg/L), DDT (9.3 mg/L), xylene (94,000 mg/L), ethylbenzene (6,100 mg/L), lindane (54.6 mg/L) and methyl parathion (47 mg/L).

Soils in this area consist of a mixture of sand, sandy clay, and clay. A shallow aquifer is located at a depth of 7 ft and a deeper aquifer exists at approximately 25 ft. Hydraulic conductivity is estimated at 2.9-4.6 ft/day.

The modified funnel-and-gate system comprises a 400-ft barrier wall that was installed using a vibrating beam technology. A collection trench lined with geotextile and filled with granular drain material was constructed upgradient of and parallel to the barrier wall. Ground water collected in this trench moves by way of a slotted well screen and associated piping into treatment vaults containing approximately 1,800 pounds of activated carbon located between the collection trench and barrier wall. From the treatment vaults, ground water moves slowly (1-2 gal/min) by way of piping through the barrier wall and into a distribution trench of similar construction as the collection trench but running perpendicular to the barrier wall.

Design costs for the Marzone PRB system were $230,000. Installation costs, including construction, materials, and reactive material, are estimated at $520,000.

Cleanup goals for the contaminants of concern are: 0.00003 mg/L for alpha-BHC, 0.0001 mg/L for beta-BHC, 0.00077 mg/L for DDD, 0.00054 mg/L for DDT, 10 mg/L for xylene, 0.7 mg/L for ethylbenzene, 0.0002 mg/L for lindane, and 0.0039 mg/L for methyl parathion. Sampling of the treatment vault effluent is conducted on a monthly basis. Contaminant concentrations in the effluent have been below detection levels.

Lessons Learned

The funnel-and-gate system was selected for use because if offered less impact to the surrounding community than other treatment technologies, while being partially self-operational. Immediately after construction, flushing of the system was required every 3-4 weeks in order to maintain flow. Improvements were made to the system to allow venting of gas pockets which were forming in the system. The activated carbon vaults were also changed to an upflow configuration. Since these improvements were made, the system has been operating effectively.