Pump and Treat and Vertical Barrier Wall -
- Groundwater is extracted on-site using 15 wells at an average total pumping rate of 190 gpm; this water is treated with air stripping and reinjected through an infiltration system
- Prior to 1996, groundwater was extracted using 210 shallow, vacuum-operated recovery well points
- A slurry wall (vertical barrier wall), 40 ft deep, encloses the 13-acre site
- Groundwater is extracted off-site using 3 wells at an average total pumping rate of 40 gpm; this water is treated with filtration and air stripping prior to reinjection or discharge to a POTW
- ROD Date: 9/85
|EPA Point of Contact:|
Lee Marshall, RPM
U.S. EPA Region 10
1200 Sixth Avenue(ECL-116)
Seattle, WA 98010
|State Point of Contact:|
Christopher Maurer, P.E.
Washington Department of Ecology
20015 72nd Avenue
South Kent, Washington 98032
Chlorinated solvents; volatiles - nonhalogenated (toluene); PAHs; and metals
- Maximum initial concentrations of chlorinated solvents and metals were trans-1,2-DCE (390 mg/L), TCE (250 mg/L), cadmium (2.5 mg/L), nickel (280 mg/L), and zinc (510 mg/L)
Unauthorized dumping, spills, and leaks from surface impoundments
Type/Quantity of Media Treated:
- 974 million gallons treated as of December 1996
- LNAPL observed and DNAPL suspected in groundwater at this site
- Groundwater is found at 5-10 ft bgs
- Extraction wells are located in 2 aquifers; the aquifers are influenced by a nearby surface water
- Hydraulic conductivity ranges from 1 to 100 ft/day
Purpose/Significance of Application:
Met goals for off-site plume within eight years of operation; shallow well points replaced recently with deeper wells to provide for containment; relatively large and expensive system.
Regulatory Requirements/Cleanup Goals:
- Groundwater cleanup goals were established in terms of surface water quality goals for Mill Creek (adjacent to the site), based on federal ambient water quality criteria. These goals were required to be met within three years. Surface water goals were established for cadmium (1.1 mcg/L), chromium (207 mcg/L), copper (11.8 mcg/L), lead (3.2 mcg/L), mercury (0.012 mcg/L), nickel (158 mcg/L), silver (0.12 mcg/L), zinc (120 mcg/L), cyanide (5.2 mcg/L), and hardness (100 mcg/L).
- Remedial goals for the off-site aquifer were established for cis-1,2-DCE (70 mcg/L) and trans-1,2-DCE (70 mcg/L). - An ESD, issued in 1995, changed the focus of the remediation from site restoration to containment.
- Monthly monitoring data indicated that the surface water quality in Mill Creek met the established criteria by mid-1990. Further, concentrations for TCE, vinyl chloride, and zinc decreased in on-site wells by two orders of magnitude from 19888 to 1995. However, elevated concentrations of contaminants remain in on-site wells. As of June 1995, concentrations were reported as high as TCE (55,200 mcg/L), DCE (14,600 mcg/L), vinyl chloride (5,490 mcg/L), cadmium (1,360 mcg/L), and zinc (117,000 mcg/L).
- The system achieved the cleanup goal for DCE in all three of the extraction wells located in the off-site plume. Concentrations of DCE have decreased in the off-site plume from above 2,000 mcg/L in 1988 to less than 70 mcg/L in January 1996. In addition, containment for the off-site plume has been achieved.
- A total of 102,000 pounds of contaminants have been removed from the groundwater during eight years of operation.
Actual costs for pump and treat were $48,730,000 ($16,032,629 in capital, including the slurry wall, and $32,697,483 in O&M), which correspond to $50 per 1,000 gallons of groundwater extracted and $478 per pound of contaminant removed.
This site operated as a waste processing facility from 1961 to 1983. Over 400 businesses transported industrial wastes to the site to be stored, reclaimed, or buried. Processes used at the site included recovery of metals from sludges and liquid wastes, spent solvent recovery, reprocessing of pickle liquor, and waste oil reclamation. In March 1981, during a RCRA audit, EPA first discovered violations of regulations governing waste storage, drum management, surface impoundments, and waste piles. Remedial investigations were conducted between 1983 and 1985. An initial ROD was issued in September 1985, and an amended ROD in September 1986.
Groundwater is extracted on-site using 15 well; this water is treated with air stripping and reinjected through an infiltration system. Prior to 1996, groundwater was extracted using 210 shallow, vacuum-operated recovery well points. Groundwater is extracted off-site using 3 wells; this water is treated with filtration and air stripping prior to reinjection or discharge to a POTW. The original approach to this site was an aggressive effort to fully restore the site to original conditions within seven years. Restoration was a priority and high costs were incurred to achieve this goal, including high operating costs. After eight years of pump and treat, the goal of restoration was changed to containment based on the technical impracticability of achieving full restoration.