Technology:
- Groundwater is extracted via two well fields located at the suspected main contaminant source area (The East Gate system), and from a line of wells located down gradient of the source areas (The I-5 system).
- Extracted groundwater is treated by air stripping.
- Treated groundwater is recharged to the subsurface via wells and infiltration galleries near each extraction area.
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Cleanup Authority:
EPA Record of Decision (ROD) signed on September 25, 1990
Regulatory Points of Contact:
Mr. Bob Kievit
U.S. EPA Region X
Washington Operations Office
300 Desmond Drive, Suite 102
Lacey, Washington 98503
(360) 753-9014 | Project Management:
Project Manager
Mr. Bill Goss
USACE, Seattle District
4735 Marginal Way, South |
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Contaminants:
Organic Compounds, Halogenated (Chlorinated Solvents) - TCE and DCE
Maximum TCE concentration in groundwater is greater than 100,000 µg/L
Waste Source: Disposal of waste solvents in surface trenches, including disposal of free liquids and disposal of drums containing liquid |
Waste Source:
Disposal of waste solvents in surface trenches, including disposal of free liquids and disposal of drums containing liquid |
Type/Quantity of Media Treated:
- 2.147 Million gallons of water extracted, treated and recharged as of 8/98
- 2772 pounds of TCE removed as of 9/97 |
Purpose/Significance of Application:
Application is successfully containing lateral migration of contaminants away from the site by extracting groundwater in the source area and down gradient of the source area. |
Regulatory Requirements/Cleanup Goals:
- Groundwater extracted at the Logistics Center Site is required to be treated to drinking water standards (MCLs) prior to recharge to the subsurface. These standards are as follows for the contaminants of concern: TCE - 5 µg/L; DCE - 70 µg/L.
- Air emissions from the treatment systems are required to be below 75 pounds per month (I-5) and 325 pounds per month (East Gate), respectively. |
Results:
- Effluent sampling at each air stripper indicates that TCE concentrations in the treated groundwater are consistently below the treatment requirement of 5 µg/L. Several samples collected during the first few months of operation for the East Gate system contained TCE in concentrations exceeding 5 µg/L, however, operations have since been modified to improve performance of this system. No results above MCLs have been observed since October 1995. TCE removal efficiencies for the air strippers have ranged from 96 percent to greater than 99 percent since start up in 1995.
- Air emissions have been below allowable limits for both treatment systems since since start up in 1995. |
Cost Factors:
The total cost incurred for design, construction and the first year of O&M for the two extraction and treatment systems was $5,208,000. The design cost was $1,251,000, and the construction cost was $3,528,000. |
Description:
The Logistics Center site at Fort Lewis covers 650 acres and is currently an active facility. The site was previously operated as an ordnance depot from 1942 to 1963 and has been operated as a non-aircraft maintenance facility since 1963. Groundwater at the Logistics Center has been contaminated with chlorinated organic compounds as the likely result of past disposal activities that included disposal of waste solvents in trenches excavated at the site. The principle contaminants of concern at the site are TCE and DCE.
In 1990, a ROD was signed for the Logistics Center Operable Unit specifying that the contaminant plume be monitored and reduced over time, and that migration of groundwater contamination from the site be minimized. In response to the ROD, it was determined that two extraction and treatment systems would be installed at the site. One system (the East Gate system) was designed to reduce the contaminant plume in the source area, and the other system (I-5) was designed to minimize off-site migration of contaminants. Both systems include treatment of contaminated groundwater using air stripping, followed by recharge of treated water to the subsurface. Recharge is accomplished using infiltration galleries located at each site and also by injection wells located at the East Gate site.
The treatment systems have been in operation since 1995, and it is anticipated that treatment will continue for 30 years. The treatment systems each consistently meet federal and local requirements for treatment of groundwater prior to recharge and for allowable air emissions. |
