Air Sparging and Soil Vapor Extraction at Landfill 4, Fort Lewis, Washington

Site Name:

Fort Lewis


Tacoma, Washington

Period of

Remedial Action


Remedial Action


Fred Luck, P.E.
Garry Struthers Associates, Inc.
3150 Richards Road, Suite 100
Bellevue, WA 98005-4446
(206) 519-0300

Soil vapor extraction (SVE) and air sparging (AS):

- A pilot test of three SVE wells and one AS well was operated from December 5 through 15, 1994.
- The full system consisted of six SVE, five AS wells, ten vadose zone piezometers, three dissolved oxygen sensor wells, and four passive air injection wells.
- The SVE wells were piped through a set of parallel treatment systems each consisting of a vapor/water separator, a blower, and two GAC canisters connected in series.
- Operations included various combinations of extraction and sparge flow rates, and use of injection wells.

Cleanup Authority:
The cleanup at Landfill 4 is being performed in accordance with a Federal Facilities Agreement between the Department of the Army, EPA, and the Washington Department of Ecology, and a ROD signed October 15, 1993.

Regulatory Point of Contact:
Bob Kievit
EPA Remedial Project Manager
Region 10
300 Desmend Drive Suite 102
Lacey, Washington 98503
(360) 753-9014
USACE Contacts:
Kira Lynch and Bill Goss
U.S. Army Corps of Engineers
Seattle District
P.O. Box 3755
Seattle, Washington 98124
(206) 764-6918 (Lynch)
(206) 764-6682 (Goss)

Volatiles (halogenated), and metals (manganese). Maximum concentrations of halogenated constituents in soil gas were: 4.1 mg/m3 dichloroethene, 1.6 mg/m3 trichloroethene, and 0.2 mg/m3 vinyl chloride. Maximum concentrations of halogenated constituents in groundwater were 7 µg/L dichloroethene, 79 µg/L trichloroethene, and 7.8 µg/L vinyl chloride. Manganese was detected in groundwater at concentrations up to 13 mg/L.

Waste Source:
Leaks and spills of solvent waste to soil surfaces on and near Landfill 4; unlined liquid waste disposal pits

Type/Quantity of Media Treated:
In situ soil (both saturated and unsaturated) - volume not determined
- Sandy gravel to sandy silty gravel
- Moisture content (unsaturated soil), 9-12%

Purpose/Significance of Application:
Application of a combination of innovative technologies to treat halogenated organic contamination in situ in both soil and groundwater.

Regulatory Requirements/Cleanup Goals:
- The ROD specified four objectives for the remedy: to prevent exposure to contaminated groundwater, to restore the contaminated groundwater to its beneficial use, to minimize movement of contaminants from soil to groundwater, and to prevent exposure to the contents of the landfill.
- No soil cleanup levels were identified in the available reference material.
- The cleanup levels established for groundwater in the upper aquifer beneath the site were: TCE - 5 µg/L and vinyl chloride - 1 µg/L.
- Monitoring for manganese in groundwater also was required for areas of the site.

- Pilot test and startup phases of the remediation were used to determine the optimum system parameters for the treatment system.
It was estimated that approximately 60 pounds of TCE were removed from as of October 30, 1997.
- Although the impact of the AS system on the degradation of TCE was not conclusively determined, it was recommended that the AS system be operated until an impact/benefit analysis for the system is completed.
- It was concluded that an additional hot spot of TCE contamination may be located upgradient and out of the area of influence of the remediation system.

Cost Factors:
- The total cost of the pilot study for this application was $241,000.
- The negotiated cost for the full-scale remediation system was $2,017,006

Ft. Lewis began operation in 1917. The Landfill 4 area consists of approximately 52 acres, which is divided into three cells located adjacent to a former gravel pit. These cells were used from the early 1950s to the late 1960s, reportedly, for the disposal of refuse, including domestic and light industrial solid waste and construction debris. After disposal activities was ceased, the landfill was covered with native material and has since been overgrown with vegetation.

Site investigations beginning in 1988 identified chlorinated hydrocarbon and metal contamination in the groundwater beneath the landfill. An RI/FS, conducted in 1993, led to the ROD for the site signed on October 15, 1993, which prescribed a remedy consisting of SVE and AS and monitoring of groundwater for manganese.

An SVE/AS pilot test was conducted at the site in December 1994 and the full-scale SVE/AS system was put on line in October 1996. The system had removed approximately 60 pounds of TCE (in soil gas) from the subsurface as of October 31, 1997, and currently continues to operate.