Cave system discovered underneath RM 620 construction project

Cave discoveries in Williamson County are not unusual during construction projects, said Kemble White, an environmental consultant for SWCA Environmental Consultants, a private firm hired by Williamson County to assess the environmental impacts of the RM 620 project. The recent cave discovery, however, is among the largest he said he has encountered during his career.

"Typically you get this kind of call and you find a little trench or cavity," White said. "About 1 percent of the time there is a cave where you can't see the whole thing and you have to make a map and go in and look around. This is more like the one-tenth of 1 percent where it is an actual cavern."

White said initial measurements of the cave show an underground complex measuring approximately 100 feet long and 60 feet wide, with ceilings as tall as 20 feet. The cave is divided into "four or five" chambers with separate entrance ways into each, he said.

"It's not Inner Space Cavern [in terms of size]," said White, in reference to the well-known limestone cavern formation near Georgetown. "It has some features that are certainly as pretty as anything within Inner Space Cavern. It is very well decorated. There are all sorts of formations."

White warned against the danger of people attempting to explore the newly discovered caves on their own.

"There are public safety concerns here, these things become attractive nuisances," he said. "We don't like to be super-specific because the next day people are going to be trying to dig their way in. They are not the safest thing in the world."

White said engineers from Williamson County, the Texas Department of Transportation, or TxDOT, the Texas Commission on Environmental Quality, or TCEQ, and the construction project team will be working together in the coming weeks to find a solution on how to resume construction on the road. Initial surveys of the cave system have not turned up any endangered species, so the next step is determining how to resume construction without disturbing the Edwards Aquifer that runs below the area.

"In this case, because of the size of the feature, everybody has to stop and take a breath and think about it a little bit more. We've got issues beyond the normal circumstances here," White said. "We will throw it all out on the table and try and figure out what is the most appropriate way to move forward. We are trying to balance the public safety and utility of the [RM] 620 roadway against the potential for aquifer contamination."

A representative for the TCEQ, which has final authority in approving projects that could potentially impact aquifer water quality and flow, said the state agency is waiting to receive a proposed plan before allowing construction to resume in the area near the cave.

"If the report details measures that will protect the cave and the Edwards Aquifer from adverse impacts to water quality, the agency will send our approval," TCEQ spokeswoman Andrea Morrow said. "[The] review can take up to a week after received."

Funded by the Williamson County Road Bond package at an estimated cost of $18.3 million, the current RM 620 project will add divided medians and dedicated left- and right-turn lanes to approximately two miles of roadway between Cornerwood and Wyoming Springs drives. Started in the spring, the project was scheduled for completion by fall 2014—a date Birkman believes can still be met despite the delay caused by the cave discovery.

"We will do what we can to move along," Birkman said. "But we are still a year and a half out on the [completion of] the project, so they assured me there is still work to be done on other parts and they have assured me they are still moving right along."