May 10, 2017

California Dam Scare Highlights Safety Issues in Texas

Reporting Texas

In February, heavy storms damaged the emergency spillway at the Oroville Dam on California’s Feather River, forcing more than 180,000 residents to leave their homes for several days until the river level fell.

The episode highlighted the dangers of dam failure, especially since many of the nation’s 90,000 dams are several decades old.

The issue is particularly relevant to Texas, which has more than 7,000 dams – the most of any state. Mansfield Dam, northwest of Austin, is the largest and one of six dams the Lower Colorado River Authority manages.

Could an Oroville-like dam failure happen here? Reporting Texas talked to dam safety experts and others about the situation.

Q: What is the status of dam safety in Texas?

 A: Texas hasn’t had a major dam failure since 1900, when the Austin Dam on Lake Austin collapsed, killing 18 people and destroying 100 homes. The dam was rebuilt and later renamed in honor of Austin Mayor Tom Miller.

But there have been less severe problems with dams, including some of the state’s largest, according to the Texas Commission on Environmental Quality, which is responsible for dam safety inspections.

In 2015, residents in the Dallas area were concerned about the condition of the Lewisville Lake Dam after heavy rains that May led to seepage, signaling possible weakening at the base of the dam.

The Army Corps of Engineers manages the dam, on the Elm Fork of the Trinity River, 34 miles upstream from Dallas. When the lake is full, the dam holds back 2.5 billion tons of water. Failure of the dam could affect more than 400,000 people.

The corps lists the dam as the eighth most dangerous in the country.

In the Houston area, the corps says the Barker and Addicks dams on Buffalo Bayou are considered “extremely high risk” primarily because of their proximity to the nation’s fourth-largest city. The dams, built in the 1940s, are undergoing $75 million in repairs.

In 2015, the Bastrop State Park Dam east of Austin failed, releasing 35 million gallons of water into the park and causing millions of dollars in damage. The dam, built a century ago, is considered a low-hazard dam because its failure would not endanger people or homes.

Q: Who is responsible for inspecting dams in Texas, and how often do inspections occur?

A: The Texas Commission on Environmental Quality (TCEQ) is the primary dam inspection agency for the state. The commission’s Dam Safety Program monitors both private and publicly owned dams.

Currently, the commission is focused only on high-hazard dams, which are inspected every five years, according to Robert Calderon, a TCEQ dam safety engineer based in Austin.

The agency will send engineers to inspect privately owned dams and make recommendations for maintenance, but the owner is responsible for paying for and carrying out the maintenance

The Army Corps of Engineers manages several major dams in Texas and does its own inspections on a regular schedule.

Q: What about the Highland Lakes dams?

A: The Lower Colorado River Authority (LCRA) manages the six dams along the river, from Buchanan Dam near Llano to the Tom Miller Dam on Lake Austin.

The LCRA’s operations staff conducts weekly and monthly internal inspections of the dams. Engineers inspect the exteriors of the dams annually.

In 2005, the LCRA completed a 16-year-long modernization project to bring dams up to current safety standards. Most of the dams that the LCRA monitors were built in the late 1930s and early 1940s.

Currently, the LCRA is working on a multiyear, multimillion-dollar project to rehabilitate the two largest dams along the Highland lakes, the Mansfield and Buchanan Dams, said Clara Tuma, a spokesperson for the LCRA.

“The project will modernize the floodgates to ensure continued reliable operations for generations to come,” she said.

None of the dams along the Highland Lakes has spillways like the one that failed at the Oroville Dam in California.

Q: What are the most common dam dangers?

A: Man-made structures like dams need regular maintenance. Problems that require more serious attention include erosion around spillways and/or cracks in the embankments, said Dorian French, a senior vice president at Brown and Gay Engineers in the Dallas area.

Droughts can cause cracks in dam structures. That’s an issue in Texas, which regularly experiences droughts that can last years. When severe storms and flooding follow droughts, they can cause problems.

Age also can make dams vulnerable to failure.

“There are always problems with any dam,” French said. “It’s a man-made structure.”

Q: How do I find out about dams in my area?

A: Finding out information about dams in your area is harder than you might imagine.

The Army Corps of Engineers maintains a national inventory of more than 90,000 dams. It includes those that are considered high or significant hazards – dams whose failure could lead to loss of life – and dams above a certain size.

In Texas, the inventory says that 5,443 of the 7,300 dams are low-risk.

The Texas Dam Safety Program can provide a list of dams in your county, but it will not include the risk classification.

Much information on dams is not public for national security reasons.