Cave collapse caused 22-foot-deep hole west of Round Rock

Cave collapsed and damaged a water line in the Brushy Creek MUD area on Feb. 8, 2018. (KXAN Photo)
Cave collapsed and damaged a water line in the Brushy Creek MUD area on Feb. 8, 2018. (KXAN Photo)

WILLIAMSON COUNTY, Texas (KXAN) — Residents in a Williamson County neighborhood woke up Thursday morning to find a 22-foot-deep hole outside.

Neighbors reported hearing what they thought was thunder at around 3 a.m. Thursday, then they called the utility district because the water went out.

Ten homes in the area of Woods of Brushy Creek subdivision are without water due to a broken water line in the 8400 block of Cambria Drive, which is north of State Highway 45. Brushy Creek MUD says the roof of a cave collapsed at the intersection of Cambria Drive and Ephraim Road. The collapse broke the water line, which left nearly a dozen customers without water for most of the day. The utility district refers to this cave as a “void” and as a “karst feature.”

The initial examination of the karst feature shows the limestone bed that forms the cave ceiling is thinner where the utility lines were installed. Williamson County officials say it’s still not clear what caused the collapse or whether the utility lines played a role, but they did note that outside the area where the utility lines are located, the cave ceiling is stable.

“It looks like the roof of the cave just collapsed and when it collapsed it broke our water line and also exposed a natural gas line,” said Mike Petter, general manager for Brushy Creek MUD. He expects the road there will be closed for a few weeks.

Cave found underneath Cambrian in the Brushy Creek neighborhood on Feb. 8, 2018. (Photographer not known)
Cave found underneath Cambrian in the Brushy Creek neighborhood on Feb. 8, 2018. (Photographer not known)

While the utility district encounters caves often, this is the first time they’ve seen a neighborhood cave of this size and a spontaneous collapse like this, Petter said. KXAN asked Petter if homeowners should be worried about the safety of their homes.

“There are probably a lot of homes in Brushy Creek that are built over cave features and we’ve seen that and it will really take an engineer to look at the stability,” he responded, adding that engineers would be headed in to evaluate the cave on Friday. Brushy Creek MUD says their initial review shows the cave is 22 feet deep, 40-50 feet wide and 170 feet long.

The cave is closed up now to keep curious people out of harm’s way, but a look at the KXAN photo gallery will give you an idea of what the cave looked like before it was sealed.

Cambrian Environmental Services sent two scientists into the cave to help map it out. A growing crowd of neighbors looked on as the scientists returned to the surface carrying a stalactite and details from the inside of the cave.

“We don’t know if this could spread, we definitely don’t want children in the area,” said Andrew Johnson, president of the neighborhood HOA.

To be clear, Johnson feels safe living there and is confident in the repair work to the street knowing that any corrective action the county or the utility district makes will have to be approved by the TCEQ.

Johnson said that caves have been located during construction sites at developments nearby.

“It’s the name of the game, Central Texas is built on a lot of different limestone shelves, it just the geology we live with in the area,” Johnson said. He explained that there are limestone quarries and well-known caves in the area nearby.

But many in the neighborhood had lived there for years and had never been told there were caves beneath their homes, including Julie Slimm who has lived there for 22 years.

“It’s a little worrisome because you don’t know if it’s gonna happen again somewhere else,” Slimm said.

A few years ago her house had to be lifted — an inspector told her it had tilted because of normal impact from rain and ground shifts.

“So we didn’t even think about it, but now I’m thinking could there be a cave where we live?” she said.

“I asked my husband do you think our homeowner’s insurance covers this, do you think there’s such a thing as cave insurance under the house?” said another neighbor, Michelle Mitchell, who has lived in the neighborhood for 17 years.

“We could have a cave club, go spelunking together maybe,” Mitchell laughed.

One woman who didn’t want to be identified told KXAN she moved to the neighborhood in 1986 and was one of the first couple of people to move into the development. The cave was open then and she and her husband would walk down into it to collect rocks. She hadn’t thought about it since then but wondered Thursday why the cave hadn’t been filled when the houses were built on top of it.

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