TxDOT planning for MoPac underpasses at Slaughter, La Crosse

Southwest Austin could have two major highway projects underway less than a year from now.

The Texas Department of Transportation on Thursday evening will host a public hearing at Bowie High School for what it calls its “MoPac intersection improvements” project: construction of MoPac Boulevard lanes underneath what would be newly built overpasses at Slaughter Lane and La Crosse Avenue.

After that hearing — a key milestone in the environmental assessment of the 2-mile, $46 million project — TxDOT officials expect to complete their review and get clearance for the work by the end of the year.

What TxDOT estimates is that two to three years of construction on the project, which is already fully funded by the agency, would commence by late spring 2016.

Construction of the Texas 45 Southwest tollway a few miles to the south is estimated to start about the same time.

The Texas 45 Southwest project should be complete by fall 2018, potentially a few months before the new MoPac underpasses allow drivers to bypass the lights at Slaughter and La Crosse, according to spokesman Rick L’Amie with the Central Texas Regional Mobility Authority. The authority was deputized by TxDOT to build and operate the tollway.

Once those underpasses on MoPac are complete, motorists would have expressway lanes all the way from FM 1626 near Manchaca to downtown Austin. However, commuters would likely spend the first couple of years working their way through yet another major construction project: the proposed addition of toll lanes to South MoPac from just north of Slaughter to Lady Bird Lake.

The mobility authority would also build the South MoPac toll lane project. TxDOT is handling the intersection project, which would not have tolls.

South MoPac’s existing four lanes are divided by huge medians in the vicinity of both Slaughter and La Crosse, with more than 400 feet of grass and greenery left fallow 23 years ago when South MoPac opened in that interval in anticipation of eventually extending the freeway lanes farther south.

TxDOT’s plans call for running the four-lane freeway about 25 feet below the current ground level at both Slaughter and La Crosse.

In addition, Slaughter at MoPac would become a “diverging diamond” intersection, a still-new approach that would have eastbound and westbound motorists in effect switch sides just before getting to MoPac. Traffic engineers say the approach, which then allows motorists to make both left and right turns without waiting on a light, moves cars more efficiently through highway interchanges.

The plans for MoPac underpasses at Slaughter and La Crosse, while still opposed by the Save Our Springs Alliance, appear to have solid support in Southwest Austin. At an October 2013 public meeting on the project, about two-thirds of the 127 comments submitted to TxDOT favored moving ahead, according to agency records. The traffic lights at Slaughter are a particular headache for the huge Circle C development, located mostly south and west of MoPac and Slaughter.

James Moseley, a Circle C resident, said that while many residents are concerned about the plan to build Texas 45 Southwest, most are in favor of building the underpasses.

“That’s going to speed up the traffic at those intersections,” he said.

Officials with the Lady Bird Johnson Wildflower Center, located just east of MoPac near La Crosse, had expressed reservations about the project at the 2013 hearing. Spokesman Lee Clippard said last week that those concerns, mostly over potential noise disturbing the peaceful getaway, have been assuaged.

“Because the main lanes are going to be beneath La Crosse, it buries that intersection, which in many ways will abate the noise,” Clippard said. “So that’s a good solution.”

Bill Bunch, executive director of Save Our Springs, said TxDOT could have alleviated the Slaughter and La Crosse traffic problems by installing so-called Michigan left turns, in which a driver turns right and makes a U-turn instead of a left turn, or with roundabouts.

But Bunch said his main problem with the intersection project is the same complaint he has raised about the separate environmental studies of the Texas 45 Southwest and South MoPac toll projects.

“They’re still chopping it up into pieces and pretending they’re not building a tolled loop from I-35 to Cesar Chavez,” Bunch said.

After being reminded there would be no toll lanes on the MoPac stretch from Slaughter to La Crosse, and for the next 2 miles to the south, Bunch responded, “Yes, but it leads into tolled lanes immediately south and immediately north.”

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