In 2006, three Austin-area municipalities formed a local government corporation called the Brushy Creek Regional Utility Authority with the goal of designing, financing, and building a new regional water system to deliver raw water from Lake Travis.
Today, those cities—Cedar Park, Round Rock and Leander—are now in the midst of seeing their goals become reality. When complete, the new facility will consist of a 105-million-gallon-per-day regional water treatment plant, as well as a wastewater collection system to help feed two of the existing plants of the cities In addition, a new purified water transmission system—now in its second phase of construction—will distribute treated water to more than 500,000 people in the three participating cities.
Construction of the underground suction chamber, which includes six well shafts.
Photo courtesy of Brushy Creek Regional Utility Authority
The first $190 million construction phase, completed in 2012, included the construction of a temporary floating pump station on Lake Travis that will remain until the deep water intake and pump station are completed, currently scheduled for 2027. It was also delivered through the first phase. a 78-inch-diameter by 5.1-mile-long raw water line connecting Lake Travis to the regional treatment plant, an initial phase of the 105 mgd regional multiphase facility, and a raw water line 78 inches in diameter by 7.5 miles. a long pipe of treated water leading to each of the three towns, said Sam Roberts, CEO of the Brushy Creek Regional Services Authority.
“The main drivers of 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, build a 145 mgd dam deep enough in 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 in a statement to ENR.
In addition, Roberts said the $250 million Phase 2 raw water supply system, currently about 40 percent complete and targeting completion in 2027, will provide approximately two miles of 11-foot-diameter tunnel at depths of up to 400 feet below the surface. along with two fixed dam structures located near the deepest part of Lake Travis with the ability to draw water at multiple levels. The project will also include the construction of a 145 mgd wastewater pumping station located on the shore of Lake Travis with a main shaft 300 feet deep by 32 feet in diameter and an underground suction chamber and 10 miles of major upgrades to the electric transmission. infrastructure
A joint venture of Thalle Construction Co. and SAK is leading the construction of the expanding project. The lead design work is a joint venture of Walker Partners and Freese & Nichols, with assistance from lead subconsultants Schnabel Engineering and K Friese + Associates.
An early view of the project’s TBM, before Miss Chelsea began the many miles of tunneling required.
Photo courtesy of Brushy Creek Regional Utility Authority
Not just another water plant
Roberts explained that the two-mile-long intake tunnel, which features two blind intake shafts to allow water to be drawn from different levels of the lake, sets this project apart from others.
Listing the main differences in an email to ENR, Roberts noted that the pumping station will supply water to three different treatment plants through two separate pumping systems and another tunnel deep under the lake bed. In addition, the project uses high-capacity submersible pumps of up to 3,600 horsepower to accommodate shaft depths of approximately 300 vertical feet.
Adding to the list of challenges, Roberts noted the “remote site with narrow, winding roads and steep slopes that require considerable coordination for large deliveries and specific operations; construction adjacent to a public park; and an endangered species preserve of extinction requiring significant permitting and public engagement; wells below the lake floodplain requiring complex work sequencing to avoid flooding; large power demand in a remote location requiring more than $25 million power upgrades; and acquisition of 100 easements to expand a substation and build 10 miles of new overhead distribution lines.”
The main shaft site, very close to Lake Travis, and the project’s three floating pump stations.
Photo courtesy of Brushy Creek Regional Utility Authority
Important 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 using boring machines nearly 9,000 feet in one direction while verifying the survey to connect with other installed drilled shafts proved a headache, Roberts said, adding that the termination of the vertical axis under the floodplain before a lake rise. the water levels that would have flooded the project site were another stressful part of the project.
Even basic needs proved particularly difficult at times. For example, it was difficult to provide power to the pump station site so workers could operate, Roberts said.
Candelaria, with Thalle, agreed that some of the logistics of the project proved more difficult than expected, such as sending equipment to the site. The treatment plant is being built on property that is surrounded by a large residential development consisting of expensive homes. The narrow, two-lane streets, which stretch for about four miles, proved problematic for daytime use, so most heavy machinery was brought in during off-peak hours.
Among the heavy equipment that would cross these two-lane streets was a 500-ton crane truck to remove marine construction equipment from the lake, including 85 modular pontoons, as well as a 400-ton crawler crane and full deep-diving equipment. facility, Thalle’s Candelaria said.
Roberts said finding the materials needed for the project challenged the contractors, specifically the stainless steel, which had to be procured through global sources, which required some adjustments prior to contractor bids.
Both engineers cited regulatory agency regulations that prohibit any runoff generated through the construction of the lake’s taps from entering the lake as additional problems.
Technology is playing its part in construction of Phase 2, which is about halfway through, Candelaria said.
The giant shaft has been built using the blind hole technique and the tunnel lining, which should be installed by the end of 2024, used modular drilling template structures to accommodate varying levels of the lake A tunnel lining is currently being placed within the project and should be fully installed by the end of 2024.
A detailed survey was verified multiple times by third parties using the latest gyroscopic survey technology to ensure accuracy, Roberts said.
“BCRUA also coordinated with the local power company years in advance to build a temporary utility on site that could meet the contractor’s power requirements during construction and prior to the development of a larger power supply project large that will bring energy to the site for the operation of the facility,” he said.
Smith believes the team is well on its way to achieving its goals of “finishing on time and on budget, minimizing impacts to the surrounding community, maintaining quality to minimize maintenance efforts for the design life of the facilities and maintain a safe work environment.”
