CORVALLIS, Ore. (AP) -- Additional measures have been put in place to contain the bentonite pumped into the Marys River as a result of a pipeline drilling mishap while a slew of regulatory agencies scrambled to assess the environmental threat and hammer out a cleanup plan.
A still-undetermined amount of the mineral -- also known as drilling mud -- entered the river near Pioneer Park in downtown Corvallis, where HDD Co. has been boring a hole for a new NW Natural gas pipeline.
The bentonite release happened sometime before 1 p.m. Thursday, when the problem was discovered. HDD immediately halted drilling operations and quickly rigged a containment boom across the river.
On Friday morning, workers erected a more substantial 30-by-60-foot fence of black plastic sheeting around the spill site, cordoning off the hole in the river bottom where the bentonite had punched through. The water inside the fence was a milky greenish-brown, and a pale plume of the same shade continued to flow downstream toward the Willamette, despite the containment efforts.
Bentonite is a kind of clay that has a huge variety of uses in everything from household cleaners to food additives to kitty litter. In directional drilling applications, it is mixed with water to form drilling mud, a combination lubricant and sealant that makes boring through rock and soil easier.
NW Natural officials said they still weren't sure exactly how much bentonite was released or when it first got into the river. Some local residents have reported seeing discoloration in the Marys as early as Sunday.
Mike Hayward, an environmental manager for the gas company, said the drilling crew was working about 400 feet away from the river when the accidental release was discovered. He said the bentonite slurry sometimes can force its way out to the surface in unexpected directions during the drilling process, moving through fissures or weaknesses in the subsurface material.
"The mud will find the path of least resistance," he said. "It's under pressure."
The drilling is part of a 9-mile pipeline project aimed at expanding the natural gas supply into Corvallis. The $17 million Corvallis Loop, as the project is known, has been under construction since April of last year.
The route runs west from Riverside Drive in Albany along the south side of Highway 34, then crosses underneath the Willamette River at Orleans Natural Area. From there it goes under Pioneer and Avery parks before turning north along 35th Street to end at the Oregon State University Energy Center.
In the process, the pipeline also crosses beneath the Marys River "two or three times," according to Hayward.
He said the pipeline route had been investigated in advance using vertical bores to sample soil types and compaction levels, but he also noted that it was impossible to know exactly what conditions exist deep beneath the surface. In many parts of the route, the bore hole for the new 12-inch pipe is 50 to 100 feet underground.
Officials of both NW Natural and HDD Co. said nothing but bentonite and water had been pumped into the bore hole and emphasized that the material should be no cause for alarm.
"That's why we use the product -- it's one of the environmentally safest products (available)," NW Natural spokeswoman Melissa Moore said.
Neil Swope of HDD emphasized that bentonite is completely different from industrial lubricants such as petroleum.
"There are no lubricants being used and no pollutants getting into the river," he said.
The two companies are working with various regulatory agencies to develop a cleanup plan for the bentonite spill, and drilling operations will be suspended until the plan is in place, Hayward said.
He added that the containment fence will remain until the end of the project, and the bentonite likely would be removed at some point.
The U.S. Army Corps of Engineers and three state agencies -- the Department of State Lands, Department of Environmental Quality and Department of Fish and Wildlife -- all were still gathering information about the bentonite release on Friday.
Alex Farrand, a fish biologist with ODFW, visited the site Friday afternoon and said he saw no dead fish.
"Fish can get away," he said. "So they're not going to be too affected."
He said bentonite can coat the gills of fish and other aquatic organisms. For less mobile creatures such as mussels, snails, crayfish and certain insects, that can be a real threat.
"It's going to coat the bottom (of the river), and it's the biota that's on the bottom and can't escape that might have problems."
Humans shouldn't have much to worry about from the bentonite release, said Charlie Fautin, deputy administrator of the Benton County Health Department, although anyone swimming in that stretch of the Marys River should wash thoroughly afterwards.
But he said he'd feel better about the situation if one of the regulatory agencies involved took water samples for independent testing.
"I'd couch everything in the caveat that we don't know the full constituents of that spill," Fautin said. "I'd like some assurance there aren't any other chemicals."