36-month dam safety study ahead for Eagle Mountain Dam in Texas

Tarrant Regional Water District (TRWD) is spending $1 million during the next three years for a team from the University of Texas at Arlington to study if recent earthquakes in the area have had any impact on dam safety at Eagle Mountain Dam in Tarrant County, Texas.

A team of graduate students led by a veteran dam safety engineer from university’s engineering department will primarily study the affect of three factors: “liquefaction, dynamic slope stability, and lateral spreading.”

Eagle Mountain Dam and Lake are located about five miles northwest of Fort Worth, on the West Fork Trinity River just north of Lake Worth in northwestern Tarrant County.

Two large embankment dams impound Eagle Mountain Lake. Since 2013, Azle and Reno — towns near the dams — have experienced several earthquakes, the highest magnitude measuring 4.0.

Published reports indicate one of the TRWD dam safety engineers, Louie Verreault, said, “We hear these stories from southern California. They have a 6.0 earthquake, and suddenly, a dam failed. Well, we need to know what the impact is from the smaller ones.”

The main dam is 85 feet in height by 4,400 feet in length and the spillway dam (saddle dam) is 60 feet in height by 3,480 feet in length. The dams were completed in 1932 and began impounding water in 1934 for water supply, irrigation, flood control and recreational purposes. The facility is one of the largest raw-water suppliers in Texas, serving more than 1.7 million people in North Central Texas.

In 2007, TRWD asked Parsons Brinckerhoff Inc. to perform a comprehensive seepage and stability assessment of both dams at Eagle Mountain Lake as part of a proactive management strategy for its existing infrastructure, according to the Association of State Dam Safety Officials (ASDSO). “Although there were no indications of concern, TRWD wanted to assess each dam to provide confidence in another 80-plus years of service.”

In 2014, ASDSO awarded TRWD and Parsons Brinckerhoff its National Rehabilitation Project of the Year for their work to rehabilitate Eagle Mountain Lake’s spillway dam.

Verreault said the work conducted during the next 36 months would also help TRWD develop a framework to assess if future tremors might pose risks.

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Gregory B. Poindexter formerly was an associate editor for HydroWorld.com.

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