Construction of the underground suction chamber, which includes six well shafts.
Photo courtesy Brushy Creek Regional Utility Authority

The $190-million first phase of construction—completed in 2012—included construction of an interim floating pump station on Lake Travis that will remain until the deep water intake and pump station are completed, currently planned for 2027. Also delivered via the first phase was a 78-in.-dia by 5.1-mile-long raw water line connecting Lake Travis to the regional treatment plant, an initial phase of the multiphase 105-mgd regional facility, and a 78-in.-dia by 7.5-mile-long treated water pipeline leading to each of the three cities, said Sam Roberts, general manager of the Brushy Creek Regional Utility Authority.

“The main drivers for the project are: first, to provide a safe, reliable and cost-effective regional water supply to the three fast-growing cities [in Texas] and, second, to construct a 145-mgd deep water intake far enough out into Lake Travis to significantly reduce the impact that severe droughts—common in Central Texas—have on our ability to draw water from the lake during prolonged drought events,” Roberts said via a statement to ENR.

Additionally, Roberts said that the $250-million Phase 2 Raw Water Delivery System—currently roughly 40% complete and targeting completion in 2027—will deliver approximately two miles of 11-ft-dia tunnel at depths of up to 400 ft below the surface, along with two fixed-intake structures located near the deepest part of Lake Travis with the ability to draw water at multiple levels. The project will also include construction of a 145-mgd raw water pumping station located on the shores of Lake Travis with a 300-ft-deep by 32-ft-dia main shaft and subterranean suction chamber and 10 miles of major upgrades to electrical transmission infrastructure.

A joint venture of Thalle Construction Co. and SAK is leading construction of the sprawling project. Leading design work is a joint venture of Walker Partners and Freese & Nichols, with assistance from major subconsultants Schnabel Engineering and K Friese + Associates.

An early view of the project’s tunnel boring machine, before Miss Chelsea commenced the many miles of required tunneling.
Photo courtesy Brushy Creek Regional Utility Authority

Not Just Another Water Plant

Roberts explained that the two-mile-long intake tunnel, which features two blind-bored intake shafts to allow water being drawn from different lake levels, sets this project apart from others.

Listing the major differences in an email to ENR, Roberts noted that the pump station will supply water to three different treatment plants through two separate pumping systems and another deep tunnel beneath the lake bed. Additionally, the project is utilizing high-capacity submersible pumps of up to 3,600 horsepower to accommodate shaft depths of approximately 300 vertical ft.

Adding to the list of challenges, Roberts noted the “remote site with narrow, winding roads and steep grades that require considerable coordination for large deliveries and concrete operations; construction adjacent to a public park; and an endangered species preserve requiring significant permitting and public engagement; shafts beneath the lake floodplain requiring complex work sequencing to prevent flooding; large power demand at a remote location requiring more than $25 million of power upgrades; and acquisition of 100 easements to expand a substation and construct 10 miles of new overhead distribution lines.”

The main shaft site, in close proximity to Lake Travis, and the project’s three floating pump stations.
Photo courtesy Brushy Creek Regional Utility Authority

Significant Challenges

Roberts and Michael Candelaria, senior project manager for Thalle Construction, said the scope of the project presents numerous challenges, ranging from marine work to logistics.

Excavating a tunnel via boring machines almost 9,000 ft in one direction while verifying the survey in order to connect with other installed drilled shafts proved a headache, said Roberts, adding that the completion of the vertical shaft beneath the floodplain in advance of a rise in lake water levels that would have inundated the project site was another stressful portion of the project.

Even fundamental necessities proved especially challenging at times. For instance, providing power to the pump station site in order for workers to be able to operate was difficult, Roberts said.

Candelaria, with Thalle, agreed that some of the project’s logistics proved more challenging than anticipated, such as sending equipment to the site. The treatment plant is being built on property that is surrounded by a large residential development comprised of expensive homes. The narrow, two-lane streets—stretching for about four miles—proved problematic for use during the day, so most heavy machinery was brought in during non-peak hours.

Among the heavy pieces of equipment that would traverse these two-lane streets were a 500-ton truck crane to remove marine construction equipment from the lake—including 85 modular pontoons—as well as a 400-ton crawler crane and a complete deep dive equipment setup, said Thalle’s Candelaria.

Finding the required materials for the project challenged contractors—specifically stainless steel, which had to be procured via global sources—calling for some adjustments prior to contractor bids, Roberts said.

Both engineers mentioned regulatory agency regulations that prohibit any spoils generated via construction of the lake taps from entering the lake as causing additional challenges.

Technology is playing its part in the construction of Phase 2, which is about halfway completed, Candelaria said.

The gigantic shaft has been constructed via blind bore technique, and the tunnel liner—which should be installed by the end of 2024—employed modular drill template structures to accommodate variable lake levels. A tunnel liner is currently being placed inside the project and should be completely installed by the end of 2024.

A detailed survey was verified several times by third parties with the latest gyroscopic survey technology to ensure accuracy, said Roberts.

“BCRUA also coordinated with the local power utility years in advance to construct a temporary service to the site that could meet the contractor’s power requirements during construction and prior to the development of a larger power supply project that will bring power to the site for operation of the facility,” he said.

Roberts believes the team is on track to meet its goals of “finish on time and on budget, minimize impacts to the surrounding community, maintain quality to minimize maintenance efforts for the facility design life and maintain a safe working environment.”