More than a decade after declaring an “Imminent and Substantial Endangerment” to public health from contaminated groundwater near the Mad River, the State Department of Toxic Substances Control (DTSC) is finally resuming work to determine the extent of the dioxin plume and to plan next steps to protect the region’s drinking water.

In December 2020, DTSC approved a contract with SHN Consulting Engineers and Geologists to identify how far contamination has spread toward Mad River from the former McNamara & Peepe Lumber Mill. The site is between Arcata and Blue Lake, about one mile upstream of the drinking water supplies for nearly 90,000 people in the Humboldt Bay area. This includes Arcata, Eureka, McKinleyville, Blue Lake, and the Samoa Peninsula. 

The plan will include sampling both groundwater and surface water for contaminants to determine the current extent of the pollution plume. The results will inform next steps to prevent toxic chemicals from reaching Mad River. The mill’s contaminants include the wood preservative pentachlorophenol, known as PCP or penta, which was banned in the 1980s for most uses due to high concentrations of dioxins – some of the most toxic and persistent chemicals ever manufactured.

These actions come two years after the DTSC decertified the 1998 cleanup, which involved “capping” the hotspot with concrete in an effort to prevent rainwater from mobilizing toxic chemicals further into groundwater and/or into Mad River. The cap failure is linked to a 15-foot rise in groundwater elevation, which has brought groundwater into contact with contaminated soil below the cap. This rise in groundwater is likely the result of the 2002 closure of an on-site well that the mill had pumped for decades. 

DTSC took responsibility for the cleanup in the 1990s, when the current landowner, Blue Lake Forest Products, filed for bankruptcy protection. McNamara & Peepe had previously also filed for bankruptcy protection, leaving the State to manage the toxic byproducts of these for-profit ventures.

In the late 1960s, two PCP spills at McNamara & Peepe and an adjacent mill killed at least 10,000 Mad River steelhead. By some accounts, these spills killed all the fish in Mad River from Glendale all the way to its mouth near McKinleyville. 

In 2005, high levels of PCP were detected beyond the cap, moving toward an unnamed tributary of Hall Creek, a salmon-bearing stream that flows into Mad River. The 2008 ‘Imminent and Substantial Endangerment Determination’ declared that a response action was necessary because a release or threatened release of a hazardous substance may cause an imminent and substantial endangerment to public health, welfare, or the environment.

Since 2008, sampling was conducted and reports written, but it wasn’t until 2018 that DTSC decided the cap had failed to contain the contamination. A new cleanup plan, expected in 2019, was delayed to March 2021. Groundwater and surface water sampling in the next few months will help identify next steps. This move by the State follows two years of correspondence by the Humboldt Bay Municipal Water District urging the DTSC to sample in preparation for implementing a renewed clean-up plan for the toxic contamination at the site.

The Water District’s General Manager, John Friedenbach said, “We have been monitoring this site and DTSC for decades. Given the failure of DTSC’s Remedial Action Plan, we have increased our pressure on DTSC to design and implement a viable cleanup plan to safeguard the water supply for the Humboldt County residents that we serve.”

Humboldt Baykeeper will be closely monitoring sampling efforts as well as plans for cleaning up and containing the contamination before it reaches Mad River. Working with Baykeeper’s scientific experts, Blue Lake Rancheria, Glendale residents, Humboldt Bay Municipal Water District, and others, we will keep the public informed while ensuring that our drinking water and the environment receive the best possible protections from degradation by these legacy pollutants.

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