Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Valley Wood Preserving, Inc.
EPA #: CAD063020143
City: 1½ miles southeast of Turlock
Congressional District: 18
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Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 06/24/88
Final Date: 03/31/89
The Valley Wood Preserving, Inc. (VWP) Superfund site, a former wood preserving facility, is located at 2237 South Golden State Boulevard on the southeast side of Turlock, California. In 1973, VWP began wood preserving operations that involved pressure-treating wood with a water-based solution containing chromium, copper and arsenic. Wood preserving operations at the site ceased in 1979 because these activities had resulted in on-site soil and groundwater contamination and off-site groundwater contamination. The contaminants of concern at the site include hexavalent chromium and arsenic.
In 1989, EPA added the site to the National Priorities List and became the lead regulatory agency for cleanup of the site. On September 27, 1991, EPA issued a Record of Decision (ROD) identifying cleanup remedies for contaminated soil and groundwater. This cleanup plan was updated in 1994, 2003 and again in 2007. VWP has implemented soil and groundwater cleanup activities at the site, including excavation and off-site disposal of contaminated soil. Currently, only residual levels of groundwater contamination remain at the site.
Contaminants and Risks
- Soil and Sludges
Prior to cleanup activities, soil and groundwater were contaminated with hexavalent chromium and arsenic. Currently, only a localized plume of low-level contamination remains in shallow groundwater at the site. This contamination is being addressed as the final cleanup remedy at the site. As a result of cleanup actions, there are currently no threats to drinking water supplies, and the remaining low levels of soil contamination are safe for industrial and commercial uses of the property.
Who is Involved
This site is being addressed through Federal and potentially responsible parties' actions.
Investigation and Cleanup Activities
The cleanup at this site involved emergency actions and a long-term remedial cleanup of the entire site. Currently, only residual groundwater contamination remains to be addressed.
Emergency Actions: After closing the site, the company excavated and disposed of approximately 1,500 cubic yards of contaminated soil. During initial groundwater cleanup from 1979 to 1983, approximately 70,000,000 gallons of chromium-contaminated groundwater were extracted. The groundwater was treated by an electrochemical treatment process and then discharged to paved depressions for evaporation. The purpose of this action was to retard plume movement and to protect domestic wells downgradient from the site. Additionally, Valley Wood Preserving removed sludge from the tank that would be used to hold water from pumping for testing; drilled several wells, originally used for monitoring, and later used for groundwater extraction; removed underground storage tanks; and drilled three deep wells as an alternate source of drinking water for three homes.
EPA selected cleanup plans for soil and groundwater in the September 1991 ROD. The cleanup plan was modified in 1994, 2003 and in 2007.
Groundwater: The initial groundwater cleanup plan involved extracting contaminated groundwater, treating it above-ground with an electrochemical process to reduce the hexavalent chromium to trivalent chromium (a non-toxic, less mobile form of chromium), followed by additional treatment using activated alumina to remove residual arsenic. The treated groundwater was discharged into an infiltration pond on the VWP property, where the water eventually seeped back into the subsurface.
EPA modified the groundwater remedial action on December 9, 1994, in an Explanation of Significant Differences (ESD). The ESD modified the groundwater cleanup plan by allowing in-situ groundwater treatment through a site-wide pilot study. An in-situ treatment is an active underground treatment to reduce concentrations of remaining contamination. The ESD also proposed adding the technology to the groundwater remedy if the desired results of the pilot study were achieved. The in-situ treatment pilot study consisted of reinjecting treated groundwater into the aquifer and saturated soil in order to reduce hexavalent chromium concentrations in subsurface soil and groundwater. During the pilot study, VWP continued to operate the pump and treat system for groundwater consistent with the initial cleanup plan, but rather than discharging the treated water into the infiltration ponds, VWP amended the treated water with calcium polysulfide (an ionic reductant) and reinjected it into the groundwater through a series of injection wells. The added calcium polysulfide reductant reacted with the hexavalent chromium, in-situ, reducing it to trivalent chromium, the less toxic and less soluble form of chromium. Trivalent chromium precipitated out of the groundwater onto subsurface soil particles and remains in the subsurface at the site, where it no longer poses a threat to groundwater quality.
During the pilot study, residual calcium polysulfide from the in-situ treatment mobilized arsenic and manganese, and also generated sulfate, temporarily and locally causing increased concentrations of these contaminants in groundwater beneath the site and down gradient of the VWP property. These temporary and localized concentration increases were expected as part of the pilot study.
The in-situ treatment of hexavalent chromium effectively reduced concentrations in groundwater such that EPA determined that the groundwater extraction system could be shut down. The groundwater treatment system has been dismantled and removed from the site. Currently, low levels of hexavalent chromium and arsenic remain in groundwater at levels above cleanup goals.
EPA modified the groundwater remedial action again on March 30, 2007, in a second ROD Amendment. This ROD Amendment #2 modifies the previously selected groundwater remedy for treating contaminated groundwater at the Site. The revisions affect both the groundwater cleanup standards and cleanup methodology selected in the 1991 ROD and revisions.
The groundwater remedy outlined in this ROD Amendment #2 provides for: a) in-situ treatment to address residual levels of arsenic contamination in groundwater beneath and downgradient of the Site, b) monitored natural attenuation to address residual hexavalent chromium, any remaining levels of arsenic following the in-situ treatment, and secondary contaminants generated by the in-situ treatment, and c) a revised cleanup goal of 10 micrograms per liter (µg/L) for arsenic in groundwater impacted by Site activities.
Soil: The 1991 Record of Decision selected a cleanup plan for soil which was amended in September 2003 when EPA issued a ROD Amendment. The soil remedy initially selected in the ROD was to excavate the contaminated soil, fix and stabilize the hazardous substances with a stabilizing agent and backfill the fixed soils into the excavated areas. The ROD Amendment revised the cleanup standards for soil consistent with the expected future industrial use of the property. It also revised the cleanup plan to require excavation and off-site disposal of contaminated soil that exceeded the revised cleanup standards. A deed restriction was also required to restrict the land use activities on the VWP property to industrial use. All soil cleanup actions have been completed at the site.
In 1989, the EPA and Valley Wood Preserving entered into a Consent Order which required the company to conduct emergency actions including the on-site removal and treatment of contaminated groundwater. The potentially responsible parties continued to extract and treat groundwater in accordance with the Consent Order until the system was dismantled in 2004. In 1990, Valley Wood Preserving and the EPA entered into a Consent Order requiring the company to conduct an investigation of the site. In 2004, EPA issued a Unilateral Administrative Order to Valley Wood Preserving to design and implement the soil remedy. The Work Plan included removal of contaminated soil from the property, off-site disposal, and back-filling with clean material. EPA issued a Unilateral Administrative Order to Valley Wood Preserving in September 2007 to design and implement the final groundwater remedy. The Work Plan for implementing the final groundwater remedy includes in-situ treatment to address residuals arsenic contamination in groundwater followed by Monitored Natural Attenuation to address any remaining arsenic, hexavalent chromium and secondary constituents of interest that are the result of in-situ treatment process.
Cleanup Results to Date
Removing tanks, contaminated soil, and treating groundwater have significantly reduced the potential for exposure to site contaminants at the Valley Wood Preserving, Inc. site.
When EPA’s cleanup remedy leaves some waste in place or the remedy will take longer than five years to complete, the Superfund law requires an evaluation of the protectiveness of remedial systems every five years. The purpose of the five-year review is to evaluate how the constructed remedy is operating and to measure the progress towards achieving the Site’s cleanup objectives. Because there are still traces of groundwater contamination, five-year reviews will continue until the contaminant levels have met remedial goals and the groundwater has been restored to a level that supports its designated beneficial uses.
The First Five-Year Review Report, completed in September 2009, found that the remedies implemented at the Valley Wood Preserving site pursuant to the Record of Decision and Amendments are protective of human health and the environment. For details, please refer to the First Five-Year Review Report below in the Documents and Reports section. EPA will continue to monitor the Site and conduct additional Five-Year reviews.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
Online information about the PRPs for the site is not yet available.
Documents and Reports
If you have any comments or concerns about Valley Wood's Site cleanup plan, EPA is always interested in hearing from you. Please contact Project Manager Marie Lacey or Community Involvement Coordinator Dana Barton at the numbers below. If you would like to be added to our mailing list and receive future fact sheets, please contact Dana Barton.
Public Information Repositories
The public information repositories for the site are at the following locations:
Stanislaus County Library
550 Minaret Avenue
Turlock, CA 95380
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
Department of Toxic Substances Control
8800 Cal Center Drive, Suite 3
Sacramento, CA 95826
After Hours (Emergency Response)