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Low Temperature Thermal Desorption at Longhorn Army Ammunition Plant, Karnack, Texas

Site Name:

Longhorn Army Ammunition Plant


Karnack, Texas

Period of

- Proof of Performance Test, February 1997
- Full-Scale Operation, February to December 1997


Interim Remedial Action


Bryan Smith
Radian International LLC
Longhorn Army Ammunition Plant
P.O. Box 107
Karnack, TX 75661
(903) 679-3448

On-Site Low Temperature Thermal Desorption (LTTD)
- Soil was fed through a vibrating screen to remove large debris
- Soil passed counter-current to hot combustion gases in one of two parallel LTTD units
- Soil was heated between 350 and 650 °F so VOCs desorbed into the gas stream.
- The gas stream from each LTTD unit passed through a baghouse and then the two streams were combined.
- The combined gas stream was preheated to 680 °F prior to entering the catalytic oxidizer where desorbed VOCs in the gas stream were destroyed
- Hot gases exiting the oxidizer passed through a heat exchanger, multi-stage quench and packed bed scrubber
- Solids exiting the thermal desorption units and baghouses were stockpiled for compliance sampling

Cleanup Authority:
CERCLA and State ROD date - May 1995

Regulatory Points of Contact:
Chris Villarreal
U.S. EPA Region 6
1445 Ross Avenue, Suite 1200
Dallas, TX 75202-2733
(214) 665-6758

Diane Poteet
Superfund Investigation,
12100 Park 35 Circle, Bldg. D
Austin, TX 78753
Project Management:
Jonna Polk
USACE, Tulsa District
1645 South 101st Avenue
Tulsa, OK 74128-4629

Oscar Linebaugh
USACE, Ft. Worth District
Eastern Area Office
(318) 676-3365 x225

David Tolbert
Longhorn/Louisiana Army
Ammunition Plant
Highway 80 East, Gate 4
Doyline, LA 71055
(903) 679-2054

Organic Compounds - Volatiles (Halogenated)
- Trichlororethylene (TCE) and Methylene Chloride
- Maximum concentrations in mg/kg - TCE (1,000 mg/kg) and Methylene Chloride (742 mg/kg)

Waste Source:
Open burning, incineration, evaporation, and burial of pyrotechnic and combustible solvent wastes

Type/Quantity of Media Treated:
Soil (ex situ)
- 32,293 cubic yards (51,669 tons) of soil
- Average Clay Content: 31.5 %
- Mean Particle Size: 0.032 mm
- Average Moisture Content: 17.5 %
- Bulk Soil Density: 1.6 tons per cubic yard

Purpose/Significance of Application:
To mitigate potential risks posed by high concentrations of chlorinated solvents in the site soil and source materials

Regulatory Requirements/Cleanup Goals:
- If TCE or methylene chloride concentrations in the soil were below 40 mg/kg, the treatment objective was to reduce the concentrations to 2 mg/kg or lower.
- If TCE or methylene chloride concentrations in the soil exceeded 40 mg/kg, the treatment objective was to reduce the concentrations by at least 95%.
- Air emission requirements included control of total chemical emissions, particulate matter and 2,3,7,8-tetrachlorinated dibenzo-p-dioxin toxic equivalents in the stack gas.

- Sampling of treated soil indicated that all soil cleanup goals were met.
- Emissions data from the Proof of Performance test and full-scale operations indicated that all emissions standards were met.

Cost Factors:
- The total cost for this project was $4,886,978.
- The total cost for treatment was $151 per cubic yard ($95 per ton) of contaminated material.

Burning Ground No. 3 was operational from 1955 to 1997. The site was used for the treatment, storage, and disposal of pyrotechnic and combustible solvent wastes including open burning, incineration, evaporation and burial. Site investigations indicated the presence of high concentrations of chlorinated solvents and heavy metals in subsurface soils and shallow groundwater at the site. In addition, buried sawdust and other solvent-contaminated wastes were encountered. A ROD was signed in May 1995, specifying LTTD as the remedial technology for addressing soil contamination at the site. Site soil cleanup goals were specified in the ROD.

Mobilization and set-up of the soil treatment plant (STP) occurred in January 1997. System start-up and shake down and the Proof of Performance test were conducted in February 1997. After successfully demonstrating that the STP could meet performance requirements, the STP was put into full production. Soil/source material excavation and full-scale operation of treatment system was performed between February and December 1997. The STP consisted of a counter-current, LTTD system followed by a low-temperature, catalytic oxidation system to treat the LTTD off-gas. After confirming that treated soil met the cleanup criteria, the soil was used as general fill material for landfill caps at two sites at the LHAAP. Demobilization of the STP from the site was completed in January 1998 and site restoration was completed by June 1998.