Until 2009, a small city in the Texas Hill Country was faced with a large water problem. It found a way to solve the challenge, winning one of Texas’ highest environmental awards along the way.
Lago Vista was regularly buying twice as much water as it delivered to its customers from the Lower Colorado River Authority, partially due to flushing high levels of total trihalomethanes (TTHMs), a group of potentially carcinogenic contaminants, out of its ground storage tanks and distribution system. The city lost approximately 2.1 million gallons of water a year flushing its ground storage tanks.
Through an innovative ground storage tank and TTHM removal project along with distribution system improvements, the city has now reduced its TTHM levels and decreased its water loss by 50 percent.
For its efforts, Lago Vista won the 2019 Texas Environmental Excellence Award (TEEA) in the technical/technology category for its ground storage tank and TTHMs removal project. TEEA, an annual Texas Commission on Environmental Quality awards program, honors achievements in environmental preservation and protection. Since 1993, the program has honored more than 250 successful environmental projects and efforts.
The City of Lago Vista solved a water problem through an innovative ground storage tank and TTHM removal project along with distribution system improvements.
Regulated by the U.S. Environmental Protection Agency (EPA), TTHMs are odorless, gaseous byproducts of the chlorine used to disinfect drinking water.
Because of Lago Vista’s low population density, the city’s water is used slowly, causing the water to stay sitting in storage tanks longer than it would in more population-dense cities. When the water sits unmoving for too long, TTHM levels can increase.
Dave Stewart, Lago Vista’s capital improvement manager and inspector, said that prior to 2008, the city was flushing its tanks up to seven times a year to keep the TTHMs in the stored water below the EPA-mandated maximum contaminant level.
“Everybody thinks that chlorine is the most dangerous gas in the water industry,” Stewart said. “That’s not true. Trihalomethanes are the most dangerous because you can’t smell or taste them and, therefore, can unknowingly consume them.”
To combat the TTHM problem, Stewart and his team created a splash pump with a 1-inch discharge and two spray heads, which evolved into the current pump with a 2-inch discharge and six spray heads. Water from the spray heads splashes down on the water in the tank, and the impact of the water droplets on the water’s surface dissipates the TTHM gas, Stewart said.
The city also added floating, fused high-density polyethylene (HDPE) pipe tank mixers, which ensure a constant turnover of the water in the tanks. This helps reduce TTHM levels by eliminating dead zones in the tanks, Stewart said.
Everybody thinks that chlorine is the most dangerous gas in the water industry. That’s not true. Trihalomethanes are the most dangerous because you can’t smell or taste them and, therefore, can unknowingly consume them.
After making these changes, the city saw drastic reductions in the presence of TTHMs — from 175 milligrams per liter to 40 — in the water distribution system. Stewart said the city’s TTHM level is now just half of the maximum EPA containment level of 80 milligrams per liter that can be present in a water distribution system. Lower TTHM levels also means less water is lost because tank flushing is not necessary.
The revamped storage tanks aren’t the only factors that have helped reduce water loss. The city also began abandoning the use of legacy conventional pipes, which are prone to leaking, in favor of HDPE pipes. About 35 percent of the city’s water distribution pipes are now made of HDPE, meaning that they are monolithic from valve to valve and don’t let water leak at fused pipe joints. HDPE pipes are easy to work with, Stewart said, and save time, money and water.
Now we don’t have to flush the tanks in the summer anymore. In fact, we haven’t flushed any tanks at all since we put the tanks mixers and the splash pumps in the tanks. It is a 100 percent completely successful project.
Before implementing the ground storage tank and TTHM removal project, Stewart said the city was unable to keep water in the tanks for more than four weeks without needing to flush out the high levels of TTHMs that developed during the warmer months.
“Now we don’t have to flush the tanks in the summer anymore. In fact, we haven’t flushed any tanks at all since we put the tanks mixers and the splash pumps in the tanks,” Stewart said. “It is a 100 percent completely successful project.”
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As communications manager for TWRI, Kathy Wythe provides leadership for the institute's' communications, including a magazine, newsletters, brochures, social media, media relations and special projects.
Bianca was a communications student worker for the Texas Water Resources Institute, providing assistance to the communications team with the institutes’ publications, including Conservation Matters and txH2O magazine.