A local environmental group’s case against the transportation agency building the SH 45 SW toll road remains ongoing, and a ruling could be made this month, officials said. Despite receiving clearance to proceed with the project after a yearslong environmental study to ensure minimal impact to natural resources, the agency is facing a legal challenge to the project in a federal district court. The trial began March 22. Water watchdog group Save Our Springs Alliance argues the Central Texas Regional Mobility Authority ought to have reviewed several projects—the South MoPac underpass, proposed toll lanes on South MoPac and the SH 45 SW tollway—as three separate projects instead of one. Officials with the agency, however, said the environmental study was appropriately studied as one project. “We feel very strongly we have done probably everything possible in the technology and design world to make sure this project has little, if any, impact on any water-quality issues as possible,” Mobility Authority Executive Director Mike Heiligenstein said. Construction has been underway since November on the project to connect MoPac with FM 1626 on the border of Travis and Hays counties. The four-lane toll road expected to be complete by late 2019 is intended to provide traffic congestion relief to residents of the growing Hays County and southern Travis County populations. Measures will be put in place to minimize environmental impact, such as a surface drainage system that captures runoff from the roadway and holds it in a pond, which is equipped with impermeable liners. The road is also being aligned with as little excavation as possible to avoid affecting recharge of the Edwards Aquifer, Mobility Authority officials said. Charlotte Gilpin, an engineer with K. Friese & Associates, the firm that led the engineering of the project, said SH 45 SW will be “one of the most progressive roadway projects in terms of protecting water quality.” Save Our Springs Alliance Executive Director Bill Bunch said the construction of the toll road will introduce large amounts of sediment into the aquifer and affect the environmentally sensitive ecosystem. “We don’t know exactly where, when or how, but the odds are very high, based on highway spill data, that [spills] will occur if the road is completed as planned,” he said. Chuck Lesniak, the city’s environmental officer, said his staff studied whether the area impacted by the SH 45 SW construction could include Flint Ridge Cave, which sits between the construction area and Shady Hollow. Lesniak said Flint Ridge Cave provides a significant connection from the ground to the Edwards Aquifer below it. The aquifer provides drinking water for more than 50,000 people. The study shows how hazardous spills might affect water quality by injecting dye tracers near SH 45 SW’s path. During the study, staff recovered the dye in wells and at Barton Springs less than two days after the injection, proving flow from the roadway to the water source might be possible . Although the engineering team worked to incorporate the city’s suggestions, Gilpin said not all of the input was implemented in the final plan largely because of “gaps in data” the city applied to the road project. “What we are left with now is they are doing the best they can to continue carrying out the environmental vision of the city and to monitor outcomes,” she said. “We had a good collaboration with them to get to a place where we’re very near to achieving their standard.”