Mining operations may be concerned about slides, but what about the demand for road materials? Local | Local

As dramatic as it appears, a large crack along Rattlesnake Hill — the ridge separating Union Gap from the Lower Valley — isn’t expected to cause disaster anytime soon, experts say.

So far, the slow-moving landslide hasn’t presented as much of a threat as a rock slide near the Nile in 2009, which buried a half-mile stretch of State Route 410 near Nile and rerouted the Naches River. 

It is a reminder that another rock slide occurred on Yakima Ridge in 1980s. This divides Yakima, Selah.

Though varying in magnitude, all three disturbances have one thing in common — adjacent gravel mining operations.

There’s nothing definitive saying mining operations caused those slides, experts say.

Those aren’t the only concerns surrounding mining operations. Operators seeking expansion of mining operations often cause neighbors to complain about noise, dust, and increased truck traffic.

But one thing is certain: there’s a real need for aggregate in Yakima County.

Demand for aggregate

The Washington State Department of Transportation officials say there’s an estimated $40 million in road construction and maintenance projects this year alone in Yakima County.

Half of the projects consist of repaving roads with the rest being bridge and deck rehabilitation, said Troy Suing, DOT’s regional administrator for planning and program management. Suing stated that three bridges will be built in North Yakima this year on U.S. Highway 12, Interstate 82, and the North First Street ramp.

All work is done by private contractors. The state or county will usually choose the lowest bid.

According to him, local material helps keep costs down by reducing transportation costs.

Tommy Carroll, Yakima County Planning Officer, said that years ago, the county identified all areas that were suitable for mineral resource overlays. This designation allows property owners and landowners to seek a mining license and begin gravel mining operations.

Operators must provide a complete site plan to the county, including the locations of the mine, stock piles, and the office.

Often times mines are cut into ridges because that’s where the best aggregate is at, Carroll said.

He said that you have to take a chance when mining into a side of the ridge.

“It’s hard sometimes to determine integrity of a ridge,” he said. “We have no mechanism to drill into the side of it to determine geology.”

Ridges

In October 2017, the crack at Rattlesnake Hill had been discovered and an investigation was initiated.

Columbia Asphalt and Gravel operates a gravel mine at the base of the crack. They have moved operations to the east and away from the areas of concern.

It’s not clear whether mining caused the crack.

Steve Reidel, a former adjunct geology professor at Washington State University’s Tri-Cities campus, doesn’t think so.

He claimed that the crack was formed from one of many old faults that were formed millions of years ago. He stated that water can get into weak areas of the rock and eventually it will slide.

However, there hasn’t been much recent movement there, he said.

“I don’t think it’s ever going to be anything worse that it is,” he said. “Last time I looked, it was just barely moving. We have a joke over here that it’s a constipated landslide.”

Reidel stated that the slide appears to be moving into the gravel mining rather than down the slopes where Interstate 82 is and the Yakima River are below.

“It looks like everything is just stopping at the quarry, it all seems to be backing up there,” he said.

“It looks like the quarry is stopping the main movement. This is why we call it a constipated slide.”

Information of this “slow moving slide” can be found on the state Department of Natural Resources website.

Rattlesnake hill is less dramatic than the one on State Route 410, near Nile, on Oct. 11, 2009.

This slide buried a half mile stretch of 410 and rerouted River Naches.

Some believed the slide was related to mining at nearby rock quarry, according to Newell Campbell, who used to teach geology at Yakima Valley Community College.

“It was a small operation and it was a huge slide,” Campbell said. “I don’t think it was that much of a factor.”

The recollection sparked Campbell’s memory of another much smaller slide that occurred on Yakima Ridge in the 1980s.

That slide, which may have been caused by mining or a road installation, was about 100 yards across halfway up the ridge’s south side and blocked an irrigation ditch, Campbell said.

“They got in there and fixed that,” he said.

Push comes to shove

Granite Northwest Construction has been mining the Yakima Ridge. However operations are suspended because the company entered settlement talks. The tribe sued the mining firm, claiming the entire ridge is cultural property that should be protected.

Granite is now getting aggregate from DTG’s mine on Rocky Top in west Yakima.

According to Planning Official Carroll, the company has an operation agreement in place with DTG. The area is legally permitted.

“They’re following the permit and everything,” Carroll said.

But Columbia Asphalt hasn’t been as fortunate. The company is working with DNR and has decided to cease operations at Rattlesnake Ridge, and doesn’t anticipate mining the site anytime soon, said company spokesman K.C. Klosterman.

“Whether that’s 10 years, or 20 years or 30 years, we’re totally going to put that in the hands of the Department of Natural Resources and that will determine whether the site is ever mined again,” he said.

Klosterman stated that the company is seeking other areas to mine, preferably on flat ground, rather than ridges to meet its material demand.

“We need those aggregates for road maintenance and road development preservation, and we will be eventually bringing other aggregate resource sites to the market, but likely they’ll be sand and gravel instead of quarried stone,” he said.