Residents, former plant workers and other stakeholders got a look at the Columbia Falls Aluminum Co. remedial investigation last week.

Well drilling and soil sampling has started in earnest, just downstream from massive landfills that sit above the defunct aluminum smelter.

All told, 43 monitoring wells will be drilled on the 900-acre site to determine the extent of contamination at the site. Previous test wells have shown high levels of cyanide in the groundwater north of the plant — well above the state threshold for drinking water.

The average well will be about 80 to 100 feet deep, but some will be deeper — 200 to 300 feet deep, said Mike Ritorto of Roux Associates, the firm in charge of the project. The Environmental Protection Agency has oversight of the project.

As of last week, three wells have been drilled. The company is also taking dozens of soil samples from surface to as deep as 12 feet. The entire effort is designed to determine the breadth and extent of contamination at the site.

The site has a mish-mash of dumps. Some of the landfills were engineered and approved for their era of design and construction. Others were simply covered up with dirt, according to former plant workers.

One site just above the plant was called the “black pond” noted former plant worker Shannon Stringer. It contained wet scrubber sludge from the plant’s pollution control system.

“We capped it with what’s on the ground,” Stringer recalled.

EPA project manager Mike Cirian said the complexity of the site is why it needs a thorough investigation.

“This is a good example of why we don’t just clean it up,” he said. “You’ve got to find out what’s under the ground.” 

Drilling will continue through the summer and is expected to be completed by September. Test America is doing all the tests and analysis. The first results should be public by next winter.