An Austin federal judge has rejected a legal challenge to three Southwest Austin road projects, according to transportation officials.

The upshot, according to Mike Heiligenstein, executive director of the Central Texas Regional Mobility Authority, is that the agency can continue construction of the Texas 45 Southwest toll road, which began in November, and resume planning for toll lanes that would be added to eight miles of South MoPac Boulevard (Loop 1).

Heiligenstein also said that the ruling Friday by U.S. District Judge Lee Yeakel gives the Texas Department of Transportation clearance to build the South MoPac underpasses planned at Slaughter Lane and La Crosse Avenue.

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However, the Save Our Springs Alliance and the Center for Biological Diversity had filed a separate lawsuit regarding that project. It was not immediately clear if Friday’s ruling affects that challenge, in which the environmental groups contend the underpass projects could harm the protected salamanders and the golden-cheeked warbler in the critically sensitive Barton Springs recharge zone.

"We are of course disappointed but not surprised," said Bill Bunch, executive director of the Save Our Springs Alliance, in an email. "We will likely be appealing promptly and seeking expedited hearing by the U.S. 5th Circuit Court of Appeals."

Yeakel’s ruling Friday rejected all claims in the lawsuit filed in February 2016 by the SOS Alliance and 11 other plaintiffs, including the Save Barton Creek Association, Clean Water Action, singer Jerry Jeff Walker and former Austin Mayors Frank Cooksey and Carole Keeton.

That lawsuit’s primary contention was that all three projects – Texas 45 Southwest, South MoPac and the underpass project – are interdependent and should have been the subject of a single environmental study.

Instead, TxDOT conducted separate studies of Texas 45 Southwest and the underpass project, and the mobility authority is doing a study on the South MoPac toll lanes.

"If three large and connected highway projects, pursued simultaneously as one integrated project within an extremely vulnerable area, need not be studied together," Bunch said, "then key mandates from both Congress and the U.S. Supreme Court calling for comprehensive environmental studies are rendered largely meaningless when it comes to highway projects in Texas."

The plaintiffs argued that reviewing all three together would force TxDOT to analyze how the projects affect each other — Texas 45 Southwest will generate additional traffic on South MoPac, for instance, and vice versa. If the judge would have ordered a single environmental study, that would have delayed the projects for years.

Yeakel had conducted a one-day trial March 22 on the lawsuit and a ruling had been pending since then. Yeakel, backed up by a later ruling by a three-judge panel of the 5th Circuit, last fall had declined to issue an injunction preventing the start of clearing and construction on Texas 45 Southwest. That work began Nov. 8 and a contractor for the mobility authority began building a bridge over Bear Creek in the middle of the 3.60-mile-long stretch of the tollway that will connect South MoPac to FM 1626.

Heiligenstein said that, under the current schedule, the four-lane tollway should open to traffic by the middle of 2019.