Garney Construction Leads $927M P3 Project Building 142-Mile Vista Ridge Pipeline
Diversifying San Antonio’s Water Supply: Vista Ridge Pipeline and San Antonio Infrastructure Project Overcome Extensive Limestone Boring and Coordination Challenges to Meet Tight Deadline
To accommodate an additional 1 million residents expected in San Antonio, Texas, by 2040, the San Antonio Water System (SAWS) looked far and wide – 142 miles, to be exact – for an innovative solution to increase the area’s water supply.
Thanks to over 3,400 leases with landowners in Burleson County, the $927 million Vista Ridge Pipeline – one of the largest public-private partnership (P3) water projects in North America – will transport water 142 miles, across seven different counties, to $165 million of infrastructure SAWS built to integrate the new supply into their existing distribution system. The project will provide up to 50,000 acre-feet of water per year (20 percent of the area’s average annual demand) from the Carrizo and Simsboro Aquifers.
“This project came out of a Request for Competitive Sealed Proposals that SAWS advertised in 2011 to look for additional water supplies across Texas that could fill gaps in the water supply plan and meet water supply needs through 2060,” said Alissa Lockett, SAWS’ Director - Engineering. “Vista Ridge was an attractive option because it didn’t entail using a surface water source or the Edwards Aquifer we already used.”
The Vista Ridge P3 project, constructed via a design-build contract with Garney Construction, headquartered in Kansas City, Missouri, taps into drought-resistant aquifers with over 12 times the amount of water in all Texas lakes combined.
With miles of pipeline, several pumping and water treatment stations, and larger-than-normal storage tanks to build, Garney and the contractors working with SAWS (see “Key Project Personnel” sidebar) face tight schedules and many coordination challenges, including time-consuming tunnel boring through limestone. Work is scheduled for substantial completion by the end of this year, with water flowing by April 2020.
Crossing Three Rivers and 115 Roads
Project development and design for the Vista Ridge project began after SAWS signed the Water Transfer and Purchase Agreement in December 2014. “Originally, we were committed to be only the design-build construction contractor, but ultimately expanded our role and Garney P3 took a majority equity position in Vista Ridge LLC to help move the project forward,” said Bill Williams, Garney’s Director of Western Pipe Operations.
That transition took place when the original project lead, Abengoa S.A., headquartered in Seville, Spain, encountered financial challenges in their international operations. Garney became majority partner with 80 percent ownership, while Abengoa retained a silent 20 percent share.
In early 2017, Garney began the $540 million construction of the transmission pipeline, three pump stations, 18 wells, three concrete tanks with 4 million-gallon capacity, and one concrete tank with 10 million-gallon capacity.
Traditional equipment accomplished most of the digging for the pipeline. “The northern end of the project is a lot of sand and the middle section is a lot of clay,” Williams said. For those areas, Garney used a Caterpillar 390 Excavator.
Closer to San Antonio, though, the terrain features a couple inches of topsoil over limestone rock. To keep that section of work moving as quickly as possible, Garney utilized a Trencor 1860 Trencher, which makes an 8-foot-wide trench, 14.5 feet deep, in one pass.
“We started it very early in the project and as the trencher progressed, we laid and installed the pipe behind it,” Williams said. “In total, we dug approximately 20 miles with that trencher.”
Across the entire 142-mile expanse, the project includes 115 different road crossings, of which about 100 were tunneled rather than open cut. “We detoured traffic for some, but we tunneled a large quantity with a trenchless excavation under the roadway so we never impacted traffic,” Williams said.
The pipeline also intersected three rivers. “The crossings extended less than 400 feet long and were all completed with tunnel boring machines and trenchless technology underneath the rivers,” Williams added.
At the beginning of construction, Hurricane Harvey brought 20 inches of rainfall in just three days. “The good news is there wasn't any sustained damage to the project; there was just a few days’ delay until it dried out enough to work,” Williams said. “We made up time quickly and we’re actually a little ahead of schedule now.”
Infrastructure in a Hurry
After a change in plans, SAWS had to move quickly to stay on schedule with their Central Water Integration Pipeline, the infrastructure that will receive and distribute Vista Ridge water. They first looked at design-build delivery, but at the end of 2017 ran into issues agreeing on a price and ultimately went with a fast-tracked design-bid-build.
Lockett transferred from SAWS’ operational side to take the lead on the project in January 2018. “To keep things moving, we used the design engineer from the design-build team so they could hit the ground running, and the owner’s representative transitioned to program manager/construction manager,” she said.
SAWS divided the project into eight separate construction contracts, financed through municipal bonds and cash. In April 2018, just three months after Lockett took charge of the project, construction of a new, 10 million-gallon storage tank began. All eight contracts started construction by December 2018. In addition to the tank that will receive Vista Ridge water, SAWS’ projects include multiple pipeline segments to transport the water to customers, a new treatment facility/pump station, improvements at two existing pump stations, and rehabilitation of an existing ground storage tank.
“For the larger projects, we issued Requests for Competitive Sealed Proposals,” Lockett said. “Because of the complicated nature of the project and the criticality of the schedule, we didn’t necessarily pick the lowest-priced bid. We wanted to make sure we had contractors with a good track record who could get the work done on schedule.”
With the compressed timeline, “All of the contracts include strict deadlines and liquidated damages – higher than we would normally put on some of the jobs,” she added. “We also included incentive clauses in the two largest contracts to encourage getting the work done faster.”
Like Garney, SAWS’ team needed to dig through lots of limestone. Two tunnel boring machines – an 88-inch Robbins DS77-320 from Solon, Ohio, and a 101-inch Herrenknecht TBM2000XE from Germany – worked on two reaches concurrently. For both tunnels, the contractor, Guy F. Atkinson Construction, LLC, of Austin, Texas, dug a starter tunnel with an Antraquip AQMI50 Roadheader.
“With its trailing gear, the Robbins tunnel boring machine is almost 190 feet long,” Lockett explained. “They had to start the tunnel with the roadheader so they could assemble the tunnel boring machine in the shaft.”
Tight workspaces also created coordination challenges among contractors. To minimize problems, “We started the tank construction as early as possible to get them out of the way of the treatment plant contractor,” Lockett said. “The footprint for construction of the 10 million-gallon tank is quite large during wire winding, and we have less than 20 acres of property to construct the entire treatment facility.”
The prestressed concrete tank rises 81.5 feet above ground – the tallest ground storage tank in SAWS’ entire distribution system. “Since the Vista Ridge water comes from a much higher elevation, we’re able to capture the energy by keeping the tank tall,” Lockett explained. “The non-traditional height makes the tank a little more expensive, but the cost savings with that energy more than pays for the difference. The energy pushes the water through the treatment plant and into our distribution system primarily by gravity. We only needed a pump station to serve one area to the north.”
In January, SAWS and Garney will start testing the new infrastructure. “We face a very hard deadline next April when we start paying about $225,000 per day for the water, whether or not we have the facilities in place to take it,” Lockett said. “We need to get all these contractors to substantial completion by December so we’re ready for testing and running water through the facilities and pipelines.”
Vista Ridge LLC will operate the system for the next 30 years while SAWS pays for the water delivered, plus operating, maintenance, and utility costs. In 2050, ownership of water rights and the supply infrastructure transfers to SAWS.