Gravel quarry near landslide ordered to halt mining

Federal and state regulators have ordered a halt to all operations at a Yakima County gravel mine at the toe of the landslide that buried a portion of Highway 410 last month.

An emergency order issued Thursday by the state Department of Natural Resources (DNR) says any excavation at Simmons & Son Hauling and Rock Crushing could set off another landslide and poses "an immediate danger to the public health, safety or welfare or the environment."

The quarry was mostly buried by the slide, one of the biggest to ever hit a state roadway. The cause of the slide remains unknown, but some experts say the mine's operations could have been a factor in destabilizing the slope.

The federal Mine Safety & Health Administration (MSHA) also issued an order that prohibits anyone from entering the mine site. MSHA earlier said the mine could resume work but changed its mind.

According to the DNR order, the owners of the mine 10 miles west of the town of Naches had started clearing away debris from the toe, or tip, of the landslide and were preparing to resume excavation.

"We felt we needed to act quickly," said state geologist Dave Norman, of the DNR.

Removing material from the toe of an active landslide is a "wretched" idea, said University of Washington geologist and landslide expert David Montgomery. "In the grocery store, you don't pull the oranges off the bottom of the pile."

The landscape around the pit is deformed and shot through with cracks and fissures, all indicative of instability, the DNR order says. Several homes, a section of Highway 410 and the Naches River could be hit if the ground gives way again.

Members of the Simmons family, which owns the mine, did not return phone calls Thursday.

The Oct. 11 landslide affected more than 80 acres and covered a quarter-mile-section of Highway 410. State transportation officials say it will probably be a year before the roadway can be rerouted and rebuilt. The slide forced the Naches River from its banks and damaged and flooded the Nile Loop Road, the major access route for about 600 residents.

DNR warned the mine operators in 2005 that the slopes above the pit showed signs of sliding, including a 10-foot-wide fissure and leaning trees. The Simmons family hired an engineer, who analyzed the slope stability and concluded the mine was not responsible for the slippage.

But Norman says that report was not acceptable because the contractor did not drill bore holes or make other measurements to truly evaluate the landslide risk.

In order to start mining again, the owners would need to conduct a thorough analysis and show that the operation won't set off more slides, Norman said.

Feds reverse decision

The federal MSHA inspected the mine after the landslide, and originally gave the go-ahead for the owners to dig out some buried equipment and resume mining on the southeast toe of the landslide. But the agency changed its mind, public-affairs director Amy Louviere said in an e-mail.

"After further review MSHA decided that until we could determine the stability of the slide no work on recovery or mining would be allowed," she wrote.

Federal regulators inspect gravel mines twice a year, focusing mainly on the health and safety of workers.

DNR's authority over mines extends mainly to reclamation: the process of filling in pits and replanting vegetation after mining stops. It's rare for DNR to shut down a mine, but Norman said the agency has the power to act because the landslide so altered the gravel mine that its previous reclamation plan is no longer valid.

"You have to have stable slopes for good reclamation," Norman said.

The gravel mine produces aggregate for road-building.

Yakima County records show that before the Oct. 11 slide, the quarry was producing some of the material for a project to resurface the Nile Loop Road.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com