BPA Tacoma Occidental Sludge

Environmental cleanup is complete at the site and the periodic review completed in 2020 shows that the cleanup work remains effective in protecting the health of people and the environment.

After cleanup, concentrations of metals (lead and arsenic) and volatile organic compounds (VOCs) remain in soil and groundwater above state cleanup levels. To prevent possible exposure to that contamination, an environmental covenant was filed for the site on January 19, 2001. The covenant prohibits any use or activity on the property that may interfere with the integrity of the cleanup. The covenant also requires groundwater monitoring for contaminants. 

When an environmental covenant exists for a cleanup site, Ecology reviews site conditions about every five years to ensure the long-term effectiveness of the cleanup action.

Ecology inspected the site on February 14, 2020. The current condition of the engineered cap and groundwater monitoring results show conditions at the site continue to eliminate possible exposure of people and the environment to contamination. Long-term groundwater monitoring continues on a regular basis.

From April 23 to May 24, 2020, Ecology held a comment period for the second periodic review to give the public an opportunity to comment on conditions at the site. One comment was received during the comment period. Ecology responded to the comment in a Responsiveness Summary.

The Second Periodic Review Report was finalized.

RELEVANT DOCUMENTS

• Second Periodic Review Report--Final.
• Responsiveness Summary.

The BPA Tacoma Occidental Sludge site is about 21 acres and located at the corner of Taylor Way and Highway 509 on the Tacoma tideflats. The property is the right-of-way, next to the Bonneville Power Administration (BPA) Tacoma substation. The site is undeveloped land zoned M-3 for heavy industrial use.

The area was used as a diary farm before 1942, when the substation was constructed and put into operation. Expansion of the substation continued through 1968.

In an effort to fill low lying areas, BPA allowed waste materials to be placed on the site in the 1960s and 1970s. About 18,000 cubic yards of lime sludge from the Occidental Chemical Corporation (OCC, then Hooker Chemical Company) plant were placed on the site. The sludge contained inorganic salts of calcium, volatile organic compounds (VOCs) and lead. In addition, about 400 cubic yards of baghouse dust and a bead-like waste product called "shot" were disposed at the site. Among other metals, the shot contained high concentrations of arsenic and lead. 

Investigations in 1990 to 1992 found arsenic, lead and volatile VOCs above cleanup levels in groundwater and soil at the site.

In 1997, BPA and OCC entered into a consent decree (legal agreement) with Ecology to clean up the site. The cleanup action consolidated 18,000 cubic yards of contaminated soil and sludge on-site into a containment facility. The containment is an engineered landfill with a cap over the contaminated soil. The cleanup was started in April 1997 and completed in August 1998. The capped landfill prevents human exposure to contaminated material. 

Twenty-two rounds of groundwater monitoring were tested from 1998 to 2019. Results show decreasing trends in VOCs concentrations in groundwater. As the VOCs concentrations have trended downwards, the number of wells monitored and variety of substances tested have been reduced. Currently, groundwater is being monitored for water quality and VOCs, including:

• Tetrachloroethylene (PCE, aka PERC).
• Trichloroethylene (TCE).
• cis 1,2-dichloroethene (DCE).
• Vinyl chloride (VC).
• Methylene chloride. 

An environmental covenant (EC) was recorded for the site on January 19, 2001. The covenant was required because the cleanup action left lead and arsenic concentrations above Method A and Method C cleanup levels in soil at the site.  

Among other restrictions, the EC:

• Prohibits activities that could result in the release of contaminants remaining on the site.
• Only allows the land to be used for industrial use.
• Does not allow groundwater from the site to be used for drinking or agricultural uses.
• Says that the property owner is responsible for maintaining the landfill and doing ongoing groundwater monitoring. 

Ecology conducted the first periodic review and held a public comment period in February-March, 2015. Ecology did not receive any comments. The first periodic review concluded that conditions at the site were satisfactory and continued to protect the health of people and the environment.