Two San Antonio Water System tunnel-drilling projects are on the horizon, including one that utility staff are calling the “most costly and complex sewer pipeline project in San Antonio history.”
At its February meeting Tuesday, the SAWS board of trustees approved a $14.5 million engineering contract with Kimley-Horn and Associates to design a more than 5-mile sewage line around Joint Base San Antonio-Lackland on the Southwest Side. Replacing the existing sewer capacity with a larger line will help stop raw sewage from spilling into Leon Creek, especially during rains.
“The sun is shining, the birds are singing, the mountain laurel is blooming, and we’re going to be able to move forward with this project,” Director of Engineering Gail Hamrick-Pigg said at the meeting.
The board also heard an update on tunnel-drilling for a pipeline that will help incorporate water from SAWS’ Vista Ridge pipeline now under construction. That roughly 140-mile pipeline will begin delivering water from rural counties east of Austin in early 2020. Tunneling in the Stone Oak area is set to begin in March.
Construction on the three-year sewer project won’t begin until 2020, but it requires more arduous tunneling than is needed to integrate Vista Ridge. SAWS officials say the job involves using a massive underground boring machine, also called a mole, to drill a tunnel roughly 10 feet in diameter at depths up to 130 feet.
Similar devices were used in the 1990s to drill tunnels under downtown San Antonio to protect the area from flooding on the San Antonio River and San Pedro Creek.
Hamrick-Pigg said the sewer tunnel would follow U.S. Highway 90 west from Leon Creek, before taking a left and continuing underneath Southwest Military Drive, then returning to the creek area south of Lackland.
The existing sewage main that passes through Lackland is 4.5 feet in diameter. It’s one of the most spill-prone areas in the SAWS system, with frequent releases of raw sewage into areas draining to Leon Creek.
Sewage spills and leaks are a significant source of bacteria in local creeks and rivers. Bacteria remain the greatest threat to water quality in the San Antonio area and are the reason local waterways are not considered safe for swimming.
Of the major sewage spills SAWS had in 2018, 52 percent occurred in the Lackland area, Hamrick-Pigg said. She called the existing line “one of our most, if not the most, critical capacity constraint in our system.”
Hamrick-Pigg told the board the project’s scheduled completion in 2023 will help it SAWS meet a critical deadline for a 10-year, $1.4 billion consent decree with federal regulators. The decree, signed in 2013, is meant to reduce spills and leaks of raw sewage from the SAWS system.
The project would add a main 7.5 feet in diameter for most of that 5-mile area, she said. The new sewage capacity will serve about 500,000 SAWS sewer customers, she said.
Jeff Haby, SAWS’ vice president of production and treatment, said the original version of the sewer upgrade proposed around 10 years ago would have involved replacing the sewer line inside the boundaries of Lackland.
But accessing the base has proved difficult for SAWS crews, President and CEO Robert Puente said at the meeting.
“You might just have a crew sitting on the base for hours and hours, and then be told to go home because they will not let you on the base, for totally legitimate reasons,” Puente said.
A new agreement with the Air Force involves routing the new pipeline tunnel around the base and transferring the existing main to the Air Force, which will be responsible for maintaining it, SAWS officials said.
San Antonio Mayor Ron Nirenberg, a SAWS board member in his official capacity, participated in negotiations with Air Force officials and called the compromise an example of “cooperation between our military and the City of San Antonio in a way that protects taxpayers.”
The SAWS board also heard an update on tunneling necessary to complete the Central Water Integration Pipeline, which would bring Vista Ridge water into the SAWS network. Alissa Lockett, SAWS’ director of Vista Ridge integration, jokingly called it the “second most exciting tunnel” in the SAWS system, after the proposed sewer tunnel near Lackland.
Lockett told the board that crews with Guy F. Atkinson Construction are digging shafts at two locations north of Loop 1604. One of these shafts is at Agua Vista Station, where contractors have built two aboveground tanks to store water arriving from Vista Ridge. The other shaft is at Cornerstone Church at Loop 1604 and Stone Oak Parkway.
Atkinson won the $48 million contract for the job last fall, setting off a dispute with another firm that had submitted a lower bid. SAWS ultimately prevailed in court.
Two tunnel-boring machines are set to arrive in San Antonio from Germany and Ohio in late February and early March, Lockett said. These machines will begin at the shafts and drill to connect the tunnel, which will connect Agua Vista Station into an existing pipeline south of Loop 1604.
The tunnel, other new pipeline segments, and upgrades at SAWS’ Bitters and Maltsberger pump stations are necessary for SAWS to prepare its system for testing Vista Ridge water on Jan. 16, 2020. Vista Ridge water would begin flowing full-time on April 15, 2020.