Environmentally- Conscious Tollway Construction in Austin By Luke Carothers
The population of Austin, Texas has grown from just over 1.2 million in 2000 to over 2.2 million in 2019. This population explosion certainly increased prosperity in the city, as new communities are growing all over the Austin area. However, as the population boomed, Austin’s infrastructure has lagged behind, and it remains one of the largest cities with an underdeveloped highway infrastructure system. A few years ago, McCarthy Building Companies (McCarthy) devel- oped a plan for a four-lane tollway and bridge that would halve the commute time for many residents of the area. This 3.6-mile extension, called the SH45 SW project, would connect communities in southwest Austin to the downtown area. Furthermore, the project was designed with other needs of the communities in mind such as noise control and an out-of-sequence section of the highway that allows for the safe passage of school buses. Despite having a plan for the SH45 SW project, the team at McCarthy had to overcome some unique challenges to get the project under way, alleviating some of the problems plaguing Austin. Civil + Structural Engineer spoke with McCarthy project manager Chris Kelly about how they got the job done. McCarthy’s SH45 SW project had been on the books for a few years before being ultimately completed last year. According to Chris Kelly, the main reason for the delay in this much-needed piece of infrastruc- ture was environmental concerns. The project is surrounded by the Edwards Aquifer and its recharge zone, which supplies water for a large portion of Texans including San Antonio and part of Austin. After initially waiting a few years for approval on the project and ex- ecuting environmental studies, the team then had to contend with a lawsuit. The basis of the lawsuit was that there were other projects in the area that needed to be taken into account in terms of environmental impact. The lawsuit claimed that these environmental studies did not account for multiple local projects happening simultaneously. The aim of this lawsuit was not to stop the project but rather contended that more research was needed before proceeding. Even when the project was finally given the green light, the concern for environmental impact did not lessen, and the plan was continually re-evaluated and adjusted to minimalize the environmental impact. Environmentalists were constantly on the site, monitoring the project’s impact on the aquifer. A team of geologists also used on the site to monitor karst features and advise the team when digging.
This means that Kelly’s team had to practice some delicate construc- tion practices to ensure features such as karsts, which not only allow water to flow to the aquifer but also support important organisms, are not hurt in the process. Whenever the team of geologists identified a karst, the construction team had to move 50-feet back and barricade the area while the plan was reviewed and modified accordingly. The project also faced storage issues that were linked to environmen- tal concerns. Because of the nature of water flowing into the karsts, the team had to be aware of where they were storing materials in the event that rainwater would wash the materials into the karst, thereby contaminating the aquifer. This means that each night the crews would have to move materials and heavy equipment away from the site, sometimes moving incredibly heavy pieces of machinery such as cranes up to 300-ft away. These challenges, among others, made for slow going at times. The project was officially started in November 2016 and was concluded in June 2019. Despite the challenges at hand as well as some owner changes toward the end of the project, Kelly says the team finished the project ahead of schedule. Kelly also believes that the SH45 SW project is just the start of “mas- sive expansion” in the infrastructure of the Austin area, stating that this project can serve as a sort of guide for future infrastructure expansion in the area. This interview took place on July 2, 2020.
LUKE CAROTHERS is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at lcarothers@zweiggroup.com.
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november 2020
csengineermag.com
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