Southwest Texas is a dry place and fast-growing place. That’s a double-edged problem that the San Marcos Water Treatment Plant is helping to solve.

The plant, in the City of San Marcos, is operated by the Guadalupe-Blanco River Authority through a 1997 regional agreement to serve people along the Interstate 35 corridor between San Antonio and Austin.

“So that agreement was forward thinking,” says Jerry Sharp, San Marcos plant manager (who has retired since his interview for this article). “That was why we expanded the plant in 2006.” Growth had begun before the 2006 expansion: From 2010-18, the population of Hays County, which includes San Marcos, increased 41% according to the U.S. Census Bureau. Cities around San Marcos saw water demand increasing slowly but steadily. Through the authority, San Marcos is a water wholesaler to other area utilities.

Surface and ground sources

Although Canyon Lake reservoir is the official source for the plant, raw water doesn’t come directly from there. Instead, a 30-inch pipeline brings water 23 miles from Lake Dunlap, which like Canyon Lake was created by a dam on the Guadalupe River.

Raw water is injected with chlorine dioxide and then with coagulant. It flows through flocculation and sedimentation tanks, which are round upflow clarifiers with tube settlers. Water then passes through standard sand and anthracite filter media. Chlorine is added before delivery to storage and distribution.

San Marcos maintains wells as a backup supply, and last August those wells became necessary. “We had a high-service pump that went to ground, and that kicked the main breaker for the plant,” Sharp says. “The emergency generator (Cummins Power Products) came on, but the fault had taken out another breaker between the generator and our main breaker, so we were getting no power, even with the generator running.

“The Guadalupe-Blanco River Authority has an electrical crew and we had them come in. They figured out that the fail-safe breaker between the line and the generator had faulted also. Once we got that reset, everything came back up.”

It was a relatively simple fix once the electricians discovered what breaker to reset: “We didn’t know that breaker was tied into that system — but we do now. So it was a learning process.” When the plant went down at about 1 a.m., pressure in the distribution system also fell, and the SCADA system (Lookout from National Instruments) automatically switched to one of the wells.

The priority of the plant is to fill the storage tanks for San Marcos and other customers, which handle their own distribution systems. But the electrical failure didn’t simply interrupt the overnight filling of tanks. “It’s not your typical system where you pump your water during the day and then at night you refill tanks,” Sharp says. “They use as much water here at night as they do during the day. It’s pumping 24/7 here.”

The difference in San Marcos is industry that works third shifts and irrigation that is done at night to reduce evaporative losses.

Impact of rainfall

Turbidity is a key challenge for the San Marcos plant’s team. “A lot of rivers around here are spring-fed,” Sharp says. “So when we get a little bit of rain, we end up in a flood event — some big, some small. But every time we end up with excess water running into Lake Dunlap, it changes the water quality coming in as far as the alkalinity, pH and organic loading on the clarifiers.”

That means jar tests and adjusting chemical feeds based on lab results. Team members have learned the plant well and have a good idea of how to change the system to compensate for problems, yet every rainfall still brings some surprise. “There’s been so much expansion and so much growth that a lot of people are building on the watershed,” Sharp says. “What used to be open property with watershed into the rivers is now populated. That’s just the price of growth here.”

In 2011, San Marcos had temperatures above 100 degrees F for 96 days straight. The authority and all its utility customers have water conservation plans for those cases, and all the customers have wells they can draw from. The utilities issue water restrictions based on their groundwater levels, while the authority does so depending on the water level in the reservoir. Building codes include mandates for low-flow toilets and showerheads.

The plant expansion completed in 2006 should be adequate to meet demand for several years, Sharp says. The economic downturn of 2008 stalled development, and that added about three years to the expected life of the expansion. In 2019 the plant produced 16 to 17 mgd during the summer pumping season, which begins in May. In the next three to five years, the plant may begin touching its 21 mgd design capacity. There is space on site for further expansion.

Stellar performance

Evidence of how well the San Marcos team knows its plant is a second five-year award from the Texas Optimization Program, a way for water plants to improve their product quality. The TOP is a voluntary way for utilities to challenge themselves to do better. “It’s based on filtration, your filtered water quality and your finished water quality,” Sharp says.

The national limit for turbidity is 0.3 NTU. In the optimization program, the maximum is 0.1 NTU. The program monitors filtration, backwash, spikes after backwash and settled water quality.

“This plant is so well designed that we decided we could meet the rigorous criteria that the Texas Commission on Environmental Quality requires for the program,” Sharp says. San Marcos joined the program in 2007 and has been a member ever since. The San Marcos plant’s team had set its own goal of being optimized, and the TOP coincided with that goal.

“We went through several years of just learning to operate this type of system,” Sharp says. “The upflow clarifiers are a little bit different animal than your rectangular settling basins or even the round settling basins. And we spent a lot of years optimizing this plant also.”

Up to the challenge

“There are some people, I’ve been told, for whom the TOP and the paperwork and the rigor of having to achieve 0.1 NTU just gets to be too much or they don’t have the people on board that we do, who enjoy a challenge. Because it is a challenge; it’s not something you could readily do without knowing how to get the most efficiency out of your plant.”

In 2007 the team felt it had the plant figured out and the expansion was done. “And it turned out to be really beneficial to our customers,” Sharp says. “It’s about our customers and supplying them with the highest-quality water that’s possible with surface water.”

Although the Texas Commission on Environmental Quality will help find coaches for plants that need them, the San Marcos plant’s team members worked out everything on their own. When Sharp and the original group of operators joined the plant in 1999, they had never seen such equipment: digital chemical feed pumps (Watson-Marlow Fluid Technology Group), flow pacing and automated valves.

“I came from a totally manually operated plant, and a lot of the guys who came here did too. It was a chore, but we stuck with it and learned each and every piece of equipment and the best way to operate it. We took our time, and over time it really worked out.”

The plant is staffed 24/7. The people who keep it running smoothly today are John Gerland, chief operator; Tommy Walenta, operator; Leroy Garza; Richard Valadez; Thomas Scott; Guy Caffey; and Cory Sibley.

“We have a really good team of people,” Sharp says. The atmosphere is team based, and staff members meet once a month to discuss safety and other issues. “Everyone carries their own weight, and everyone likes everyone else. This is probably the best group we’ve had in the 20 years I’ve been here.”

Competing with oil

When Jerry Sharp came to the San Marcos Water Treatment Plant in 1999, he joined two local people and three others who were recruited, like himself, from elsewhere in Texas. He is the only remaining member of the group that started the newly built plant, and it’s less likely these days that operators can be recruited from elsewhere.

“When you have an opening, it’s getting harder and harder to find someone who’s certified in the water business,” Sharp says. “I don’t see that many people getting into the water business anymore.” Even if the authority finds potential employees, the question is whether they will relocate and how much commitment they have to a water career.

The problem involves both mindset and competition from other industries. “There is still the oil field here in Texas, and that does purport to be more money,” Sharp says. “It’s less stable than the water business, but we have had people leave here to go to the oil fields.” 

Oil work is also much more physical, while water work is much more mental. The Guadalupe-Blanco River Authority Human Resources Department does all the recruiting, although Sharp does interviews. To expand the pool of candidates, the authority is starting an internship program. 

There is already an internship for the laboratory and the accounting department, and the authority is working with high schools and colleges to set up one for the water and wastewater treatment plants.