likely cause 
of quake

Though a precise connection can’t yet be drawn, all signs are pointing to a deep-well injection project by the Bureau of Reclamation as the genesis of an unusually large earthquake felt across the region Wednesday evening.

The quake — revised down to 3.9 magnitude Wednesday, from an initial reading of 4.3 magnitude — was located five miles northwest of Bedrock, where the federal agency operates its Paradox Valley Salinity Control Facility.

At the time of the quake, 9:47 p.m., engineers at the facility were injecting salt brine into their well 16,000 feet below the surface, according to officials.

“The quake was felt by workers at the facility and some residents in the area, and our employees shut down the facility at 9:50 p.m.,” said Justyn Hock, spokeswoman for the Bureau of Reclamation’s Grand Junction office.

“We don’t know about the earthquake yesterday — what caused it — but we can tell you that we have caused earthquakes before,” Hock said Thursday. “This is one of the biggest ones that we’ve had out there.”

In fact, it may have been the biggest.

The facility — which has been removing water from the Colorado River, evaporating salt and turning it into brine, then injecting it deep into the earth since the mid-1990s — has recorded countless seismic shifts since its inception.

The biggest temblor recorded at the facility was a 4.3 magnitude quake measured in May 2000, but Hock said engineers believe that was most likely a quake in the high-threes range. In that case, the quake was measured in close proximity to the facility, and readings tend to be on the high side then, Hock said.

An accurate 3.9 magnitude quake was measured at the facility in 2004, she said.

She also said the bureau is in the process of evaluating all of its collected information and is always tweaking its operating procedures as officials learn more about their activities.

“One of (the procedures) is, if there is an earthquake felt, that we shut down,” Hock said. The Paradox de-salinization project is unique in the country, and removes 110,000 tons of salt from the Colorado River every year.

Water users downriver, including from Mexico and California, require certain salinity levels in their usage agreements. Paradox is positioned along a massive salt dome, a perfect spot to remove the salt the Colorado River picks up by flowing nearby.


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