A Dam in Distress | SierraSun.com
YOUR AD HERE »

A Dam in Distress

Seth Lightcap/Sierra SunVerne Brown, project geologist for the US Army Corps of Engineers, inspects core samples taken from beneath the Martis Dam on Wednesday near Truckee.
ALL |

The Army Corps of Engineers geologist sifted the clay and silt through his fingers as he stood near Martis Creek Dam, skillfully differentiating the materials by touch.Verne Brown was evaluating the 35-year-old earthen flood-control dam last week after earlier inspections had found worrisome leaks.But it wasnt suspect silts or clays that prompted the Corps to categorize the Martis dam as extremely high risk, Brown said.Instead, the geologist blamed Martis Valleys coarse glacial deposits of sand, gravel, and boulders for allowing water to seep under the dam.In the initial investigation in the 60s they decided this is the best site for a dam, Brown said. Although in hindsight maybe not.The worst-case scenario would be the seepage to increase and exceed the dams out-flow, at which point the dam could fail from the bottom up, said Ronn Rose of the Corps Dam Safety Assurance Program.Its in the highest-risk category for a dam, Rose said. Martis is one of just six dams in the country identified as the nations riskiest, he added.The dams ranking comes not only from the probability of failure, but also the consequences downstream, which in this case is the flooding of the Truckee River Canyon and a large part of Reno, Rose said.While the problem has gained extra scrutiny the last few years, a series of test fillings of the dam since its 1972 construction have all indicated seepage, that could potentially undermine the dams integrity in an unlikely flood event, Rose said.Weve known this is a problem since 1973, Rose said. Failure has been initiated; each time there was a test fill it made it worse.Compounding the problem is a series of fault lines underneath and near the dam, Rose said. The Corps is still investigating whether or not the faults are active.Studies to explore the full scope of the seepage issue began earlier this year, with $1.5 million budgeted for core-sample drilling, and an estimated $2 million next year for geological surveys, Rose said.After that, an optimistic and rough timeline would continue study to 2011, design work in 2012-13, and construction of whatever remedial designs are chosen in 2014-15, he said.Thats accelerated; it may not seem it, but 10 years is light speed, Rose said.Potential solutions range from repairing the dam to completely removing it, but Rose said a decision is still far away.The dam was originally built for flood control on the Truckee River, said Corps Project Manager Veronica Petrovsky. The earthen dam provides 30 percent of Renos flood control, and also protects the communities of Glenshire, Boca, Hirschdale, Floriston and Mystic, according to a Corps of Engineers presentation.The potential for water storage was added to the dams design at the last minute, and still hasnt been taken advantage of, she said.We wouldnt sacrifice the flood control capabilities for water storage, she said.While some informal requests for water storage have come from the Reno area, Petrovsky said the Truckee Meadows Water Authority has shied away once the seepage issues surfaced.Until a solution is reached, authorities will keep the reservoir at a minimum level, Rose said, which minimizes risk but does not eliminate it in the case of an extreme flood event.


Support Local Journalism

 

Support Local Journalism

Readers around Lake Tahoe, Truckee, and beyond make the Sierra Sun's work possible. Your financial contribution supports our efforts to deliver quality, locally relevant journalism.

Now more than ever, your support is critical to help us keep our community informed about the evolving coronavirus pandemic and the impact it is having locally. Every contribution, however large or small, will make a difference.

Your donation will help us continue to cover COVID-19 and our other vital local news.

For tax deductible donations, click here.

Start a dialogue, stay on topic and be civil.
If you don't follow the rules, your comment may be deleted.

User Legend: iconModerator iconTrusted User