Could an earthquake topple the stacks?

By Robert Gray – El Paso Inc. staff writer

  • The short stack as seen from the tall stackThe short stack as seen from the tall stack.

As local non-profit Save the Stacks rushes to prove it is safe to leave the giant, 828-foot stack standing as a monument on the site of the former Asarco copper smelter, some are beginning to wonder: Could an earthquake cause the stacks to collapse with catastrophic results?

Those concerned cite a statistic that there is a 16-percent chance of a major earthquake within 50 miles of El Paso in the next 50 years.

El Paso Inc. put the question to Dr. Diane Doser, an earthquake expert in the Department of Geological Sciences at the University of Texas at El Paso.

The first thing to know, Doser says, is there are a lot of reasons why predicting earthquakes, difficult anywhere, is particularly problematic in this region.

“It’s not like a weather report. You know, ‘This week we have a 50-percent chance of slight earthquakes,’ ” she says.

Instead, predicting earthquakes in this region is fraught with peril.

Earthquakes that can be felt occur here only every decade or two, and the last time an earthquake was strong enough to alarm people was probably in 1931. The largest earthquake known to have occurred in Texas was centered more than 100 miles east of El Paso near Van Horn and caused little damage here.

Before that, an earthquake in 1887 caused people to rush out of buildings but little more, Doser says.

It is also very difficult to use radiocarbon dating to determine when past earthquakes occurred because of how the soil has developed here, without a lot of carbon. So researchers can only determine when an historic earthquake took place using carbon dating with a rather sizeable margin of error: plus or minus 1,000 years.

Then there is the U.S.-Mexico border. While there are probably important geological structures to study in Chihuahua, it’s hard, if not impossible, to get funding to study them, Doser says. It all leaves earthquake researchers with little historical data to work with, which is an important part of predicting future earthquakes.

The best she can conclude is, “Our chances are higher than other parts of Texas, but still very low.”

The second thing to know, Doser says, is the stack, put up in 1966, would not have been built with earthquakes in mind.

The science of earthquakes has progressed a good deal in 46 years, Doser says. And it wasn’t until the late 1960s that a seismograph was located here, in a lab at the university.

No warranty

That statistic – a 16-percent chance of an earthquake in the next 50 years – appears to come from a 2009 earthquake probability calculator on the U.S. Geological Survey website. Doser says it’s important to point out the data come with a very big disclaimer:

“Although this information is a product of the U.S. Geological Survey, we provide no warranty, expressed or implied, as to the accuracy of the data contained therein. This tool is not a substitute for technical subject-matter knowledge,” it reads.

Robert Ardovino, a founder of Save the Stacks, says the group has hired an engineer with that “technical subject-matter knowledge” who will determine if it is safe to leave the stack standing, using soil sample data and a soon-to-be published report by Atlanta-based Industrial Access.

The loose-knit community group working to save the stacks maintains they are iconic landmarks, valuable as monuments to America’s industrial heritage and El Paso’s history, and can be safely preserved.

“We, too, want solid, strong stacks. We are going to be standing under them with our families one day, too,” Ardovino says.

Engineers with Industrial Access conducted a painstaking visual inspection of the inside and outside of the stacks last month, rapelling down them on ropes.

Early indications are that the stacks are in good condition. The final report is expected in the next couple weeks.

The gigantic 828-foot stack and the smaller 610-foot stack tower over the property that was once the site of the Asarco copper smelter and is now the site of a massive remediation effort.

Houston-based commercial brokerage Transwestern is handling the sale of the property, according to site trustee Roberto Puga, who has discretion over the cleanup and sale of the property.

Engineers will resume planning the demolition of the two stacks in a month, he says, if Save the Stacks cannot prove it’s safe to leave them standing and find an entity that would become responsible for their maintenance and the liability.

The standard he set is high, Puga says.

“The consequences of a failure of the stacks is huge,” he says.

As for the Texas Commission on Environmental Quality, spokesperson Terry Clawson said in an email statement the agency doesn’t have a position on the preservation of the stacks, “so long as the result is consistent with the goals of the trust.”