Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Selma Treating Co.
EPA #: CAD029452141
City: 1/2 mile from Selma
Congressional District: 20
Other Names: Selma Pressure Treating Company Saw Mill Properties
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Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 12/30/82
Final Date: 09/08/83
The 18-acre Selma Treating Company site (Site) includes a 3 to 4 acre wood treatment facility and 14 acres of an adjacent vineyard that were used for site drainage. The facilities on-site have been used by a series of owners to treat lumber products almost continuously since 1936. Historically, at least two methods of wood preservation have been used on-site. Before 1965, lumber was dipped into a mixture of pentachlorophenol (PCP) and oil, and then was dried on open racks, letting the excess liquid drip off. In 1965, the Site moved to a pressure-treating process, which consisted of two basic steps: conditioning the wood to reduce moisture content and increase permeability, and infusing the wood with chemical preservatives.
From 1936 to 1971, chemical wastes from the treatment plant were disposed of on-site in percolation ditches, dry wells, an unlined pond, and a sludge pit. Chemical preservatives also were released to the ground, particularly in the wood treatment area, as a result of spillage, dripping, and leaking. Waste fluids were released through pipelines that ran along the boundaries of the vineyard into off-site drainage areas and ditches.
In 1971, after the Regional Water Quality Control Board (RWQCB) determined that the releases presented a serious threat, the Selma Treating Company was required to install an effluent recovery system.
In 1981, the Selma Treating Company filed for bankruptcy. In 1982, Sawmill Properties, Inc. acquired the facility with the stipulation that Selma Leasing Company continue to accept responsibility for Site cleanup.
The groundwater aquifers beneath the Site provide
the only source of potable irrigation water and drinking water in the area for residents and farm workers living and working outside of the City of Selma limits. City of Selma residents and workers have access to a public drinking water system provided by California Water System that meets federal and state drinking water standards.
Contaminants and Risks
- Soil and Sludges
The Site is a former wood treatment facility. Site groundwater is contaminated with chromium. Site soils are contaminated with PCP, volatile organic compounds (VOCs), and heavy metals, such as chromium, arsenic, and copper. People who ingest or have dermal contact with contaminated groundwater may be at risk for adverse health effects.
The soil cleanup has been completed.
Who is Involved
This Site is being addressed through Federal and State actions. On October 1, 2009, the State of California Department of Toxic Substances Control (DTSC) became the lead regulatory agency for the Site. EPA is leading a remedial investigation to cleanup the chromium groundwater plume. EPA conducts a Five-Year Review to evaluate the effectiveness and protectiveness of the remedy.
Investigation and Cleanup Activities
Site cleanup is being addressed in two stages: initial actions and a long-term remedial phase focusing on the cleanup of the entire Site.
Initial Actions: In 1982, Sawmill Properties installed concrete drip drying pads and run-off containment
berms, and instituted operational controls to prevent further soil and groundwater contamination.
Soil Remedy: The selected soils remedy in the 1988 Record of Decision (ROD) included:
- Excavation of contaminated soil exceeding cleanup goals (13,000 cubic yards);
- Mixing soils with a fixative agent to harden and stabilize contaminated soil;
- Placement of the soils into a repository cell on-site;
- Placement of a RCRA Cap on top of the fixed soils to provide additional protection from surface disturbance and water infiltration; and
- Abandonment of six dry wells.
The U.S. Army Corps of Engineers (USACE), under an Interagency Agreement (IAG) with EPA, performed this remediation work between 1991 and 1993. Contaminated soils were excavated from an on-site unlined pond, sludge pit, percolation ditches, and dry wells used to drain surface run-off from the treated wood storage areas of the Site. Additionally, off-site soil areas affected by Site contaminants were excavated and stabilized on-site.
Based on data collected for remedial design during the soil remedial action, EPA determined that additional soil remediation work was needed beyond that done under the 1988 ROD, and an explanation of significant differences (ESD) for more excavation and more stringent cleanup standards was completed in 1993. The ESD for the soil remedy included a more stringent cleanup standard for arsenic
([25 parts per million (ppm)] ), a cleanup standard for pentachlorophenol in soils (17 ppm), additional areas of soil contamination requiring cleanup, and documentation of compliance with Resource Conservation and Recovery Act (RCRA) Land Disposal Restrictions.
Work under this ESD was performed in 1999 by USACE and included excavation of an additional 5,000 cubic yards of soil from areas within and just outside the plant property where drainage and spillage from treatment operations had deposited Site contaminants on public right of ways and adjacent properties. The excavated soil was stockpiled on-site and the excavation area was backfilled with clean soil.
In 1997, EPA entered into another IAG with the USACE Rapid Response Program, to install a perimeter fence and perform demolition of portions of the on-site wood treatment facility.
Final Soil Remedy Construction Activities (September 2003 ROD Amendment):
- Uncover and remove excess soils from the existing on-site RCRA soil repository cell to prepare it to receive additional contaminated soil;
- Place the previously stockpiled (5,000 cubic yards) soil into the soil repository;
- Excavate up to 5 feet of surface and below surface soils (total volume removed was approximately 25,000 cubic yards) and backfill and grade the excavated areas with clean soil;
- Install a RCRA geo-composite clay liner and soil/vegetative cap on the soil repository;
- Install a 5.4 acre asphalt RCRA cap on the east end of the plant property to cover the excavated area and contain the contaminated soils below five feet; and
- Operate and maintain the RCRA caps for a period of one year.
The excavation, backfill, and reinstallation of the RCRA cap on the soil impoundment cell was completed in November 2003 and the asphalt RCRA Cap was completed in May 2004. The final construction inspection by EPA and the State was conducted on June 10, 2004.
Land use restrictions placed on portions of the Site covered by the asphalt cap and RCRA cap. A land use covenant dated June 2006 between Selma Pressure Treating, the current owner, and DTSC is in place.
In the 1988 ROD, the selected remedy for chromium in groundwater consisted of constructing and operating a groundwater extraction and treatment system to convert hexavalent chromium to trivalent chromium, the disposal of treated and tested groundwater by re-injection into the aquifer, and the disposal of sludge generated by the treatment process.
In 1997 a second ESD was completed for the use of percolation ponds instead of re-injection. The groundwater extraction and treatment system including eight extraction wells was installed from May-August 1998, and the post construction inspections and operational tests were conducted in September 1998. The treatment system began full operation at 200 gallons per minute (gpm) in late September 1998. Additional, ongoing groundwater system optimization is occurring at the Site as part of the long-term cleanup activities.
Bench-scale tests completed in early 2005 showed results that supported the use of molasses to increase the metabolism of naturally occurring microorganisms to produce a biologically enhanced, chemically reducing environment. Use of microorganisms in-situ, or in-situ bioremediation (ISB), is a cost-effective remedial technology at the Site and will result in a large cost savings over time. An ESD in 2005 adopted full-scale use of ISB to optimize groundwater remediation at the Site.
In 2005, an ISB Pilot Test (Phase 1) was completed within the shallow chromium contamination source area at the Site. The Pilot Test used direct injection methods and ISB groundwater treatment was expanded to other portions of the chromium-contaminated plume.
After further delineation efforts, Phase 1A ISB was expanded in 2005-2006 to encompass areas immediately surrounding the Phase 1 Pilot Study area. Phase 2 ISB was also divided into two sub-phases with Phase 2A being delineated, designed and implemented in early-2006. The depth of the chromium plume within the Phase 2A area was the limit of the capability of using the direct push, direct injection methodology at this Site.
Phase 2B ISB, which began operations mid-2006, was utilizing a recirculation methodology to introduce the ISB into the chromium plume. ISB recirculation methods are longer term by nature and are more effective on deeper plume areas. An additional substance, sodium lactate, which was also bench-tested in 2005 concurrently with molasses, was used successfully during Phase 2B. Lactate lasts longer and was added to the process to improve reduction of residual (hexavalent) chromium within zones of lower hydraulic conductivity. Phase 3 began operation in October 2007 to treat the hexavalent chromium plume under Highway 99 and is ongoing.
The use of ISB technology in the source and downgradient plume areas has been successful in reducing chromium concentrations at the Site. The earlier extraction wells which were installed connected to the conventional groundwater treatment plant in 1998 have been disconnected and re-routed and connected to the ISB treatment system.
Cleanup Results to Date
DTSC has responsibility for ongoing operations and maintenance of the soil and groundwater remedies. The soil cleanup is completed. The groundwater remedy was optimized to use in-situ bioremediation to treat hexavalent chromium in groundwater.
EPA will issue the Fourth Five-Year Review Report in 2016. The Third Five Year Review Report was completed on September 28, 2011. To review this document, either click on the DTSC link - http://www.envirostor.dtsc.ca.gov/public/profile_report.asp?global_id=10240051# - or scroll down to "Technical Documents" below.
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.
The PRPs for this Site are bankrupt or no longer viable.
Documents and Reports
Public Information Repositories
The public information repositories for the site are at the following locations:
Fresno County Library - Selma Branch
2200 Selma Street,
Selma, CA 93662
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
Sacramento, CA 95826-3200
After Hours (Emergency Response)