Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 12/30/82

Final Date: 09/08/83

Deleted Date:

Coast Wood Preserving is an eight-acre, active wood treatment facility located three miles south of Ukiah. Historically, Coast Wood Preserving used a solution of sodium dichromate, copper sulfate, and arsenic acid (CCA) to pressure-treat and preserve wood products. Over the years of operation, dripping and spillage of this chemical solution have contaminated the soil and groundwater on- and off-site. The Town of Ukiah has a population of approximately 13,300 people. There are two duplexes, two bunk houses, and six motel units located within 1/2 mile of the site. The motel units are used to house seasonal workers at a nearby packing facility. The land near the site is used for timber-related purposes, sewage treatment, pear orchards, and business and commercial facilities. The groundwater in the area supplies municipal, domestic, and agricultural water. Portions of the site are located over two streams 1/2 mile upstream from where they meet the Russian River. The river also supplies municipal, domestic, and agricultural water.

From 1971 to about 2004, CWP used a solution of sodium dichromate, copper sulfate, and arsenic acid (CCA solution) as wood treatment chemicals. The CCA chemicals were replaced by a mixture of Alkaline Copper Quat solution (ACQ) and Disodium Octoborate Tetrahydrate (DOT). Past operations have resulted in chromium and arsenic contamination of the soil underlying the facility. On January 31, 1972, Mendocino County raised questions about the possible discharge of CCA preservatives via runoff of rainwater. This was documented on February 23, 1972 by the California Department of Fish and Game, which notified the RWQCB that preservation solution was being discharged into tributaries of the Russian River. Waste Discharge Requirements and Cease and Desist orders were issued by RWQCB between 1972 and 1981 to control discharges to surface water. CWP began to conduct soil and groundwater investigations, including installation of a number of monitoring wells.

Contaminants and Risks

Contaminated Media

Groundwater

Soil and Sludges

Groundwater and soils are contaminated with heavy metals including chromium, arsenic, and copper. Drinking or coming into direct contact with on- and off-site runoff and contaminated groundwater used for drinking or agricultural purposes may pose a threat to human health. Since the areas of contaminated soil are covered with pavement, no direct contact with contaminated soil is expected. Public access to the site is prevented by a security fence that is locked after business hours.

Who is Involved

This site is being addressed through State and Coast Wood Preserving actions. Although the site is listed on the National Priorities List, the State is the lead regulatory agency for this site, and therefore is the primary contact.

Investigation and Cleanup Activities

The site is being addressed in two stages: immediate actions and a long-term remedial phase focusing on cleanup of the entire site.

Initial Actions

In 1981, the North Coast Regional Water Quality Control Board [the Board] issued an order requiring Coast Wood Preserving to establish measures to stop the release of toxic waste. Later that year, the company was referred to the Board for violation of the order. The Court subsequently issued an injunction, requiring that the company perform the site cleanup. It was later determined that Coast Wood Preserving was not complying with the injunction.

In 1983, Coast Wood Preserving, under EPA oversight, began pumping out the contaminated groundwater plume and storing it on site. Subsequently, the company built a slurry wall and an interceptor trench to prevent the off-site migration of contaminated groundwater. A groundwater extraction well was installed to pump the contaminated groundwater, and an injection well, where Coast Wood Preserving injected treated water, was built downgradient from the site. Other activities included grading and building berms to prevent surface water runoff from the operations area.

Cleanup Ongoing

In 1989, DTSC approved a cleanup plan at Coast Wood to address the cleanup of soil and groundwater contamination at the Site. The cleanup plan included hydraulic control of impacted groundwater using extraction wells, electrochemical treatment of extracted groundwater, recycling, reuse, and discharge of treated groundwater via an injection well and groundwater monitoring and sampling. The cleanup plan assumed that soil remediation would be conducted when the facility was closed. In 1999, the cleanup plan was amended to change the remedial action for groundwater from extraction and treatment to in situ reduction and fixation of hexavalent chromium using calcium polysulfide reductant.

In 2003, Coast Wood proposed remediation of soil contamination within accessible areas, while the plant was still in operation and upgrades were being made. In August 2003, DTSC issued an Explanation of Significant Differences (ESD) that revised the cleanup goals for hexavalent chromium and arsenic in soil to 42 milligrams per kilogram (mg/kg) and 27 mg/kg, respectively. The arsenic cleanup goal was established on the basis of a commercial /industrial setting and on an excess cancer risk of 10-5, while the hexavalent chromium cleanup goal in soil was established based on the prevention of exceedences of the California MCL in groundwater as a result of rainfall infiltration through contaminated soil. The revised cleanup plan also modified the timing and the scope of the soil remediation to include soil remediation within accessible areas while the plant was still in operation. The soil remediation was completed in February 2004 and about 2,965 tons of contaminated soil were disposed off-site at a permitted facility.

In 2005, more contaminated soil beneath a 330,000-gallon water tank at the former northern storm water tank farm, originally proposed to be completed following plant closure, was excavated. About 2,734 tons of contaminated soil were excavated and disposed offsite.

Between October 2002 and June 2004, Coast Wood submitted documents to the RWQCB to describe the changes to the existing operations. The operational changes included elimination of the wood treatment solution consisting of chromic acid, arsenic acid and copper oxide and replacement of those chemicals with ACQ including variants of ACQ such as copper ammonium carbonate solution (ACQ-C) and aqueous copper solution (ACQ-C2). Borate solution known as disodium octaborate tetrahydrate was also used together with ACQ as the new wood preservative mixture. On November 29, 2004, RWQCB issued a Waste Discharge Requirements Order (Order No. R1-2004-0094) to allow CWP to use the new wood preserving chemicals. It also permits Coast Wood to use other reducing agents, in addition to calcium polysulfide, such as ferrous or zero valent iron to treat soil and groundwater contaminated with hexavalent chromium.

According to the Combined Fourth Quarter and 2011 Annual Groundwater Monitoring report, two monitoring wells contained dissolved chromium above the California Maximum Contaminant Level (MCL) of 50 micrograms per liter, while three monitoring wells contained arsenic concentrations at or above the federal MCL of 10 micrograms per liter. The concentration of total dissolved chromium in the groundwater appears to show an overall decline while the concentration of arsenic declines in some areas. The arsenic and the chromium will continue to be monitored to see if the trends continue.

Cleanup Results to Date

Groundwater extraction and treatment, and construction of a slurry wall and berms, have been effective in controlling the spread of groundwater contamination, thereby reducing the potential for exposure to hazardous materials. The remedies for final soil cleanup at the Coast Wood Preserving site were completed in early 1990. Groundwater treatment will continue until established cleanup goals are met.

Four Five Year Reviews have been completed for the site -- in 1996, 2001, 2006 and 2011. These reviews found that the remedy is protective of human health and the environment. For details, please refer to the most recent Five Year Review report below in the Documents and Reports section. EPA will continue to monitor the site and conduct additional Five Year Reviews.