State environmental investigators are probing a potential discharge of liquid from a sewer line project that affected Robber Baron Cave Preserve, an endangered species refuge and a popular site for guided cave tours on San Antonio’s North Side.

On Nov. 7, a “significant” amount of fluid related to a sewer line repair project on Nacogdoches Road flowed into the cave, said Joe Ranzau, president of the Texas Cave Management Association (TCMA). The nonprofit has owned Robber Baron Cave at 155 Camellia Way since the 1980s.

“TMCA has a significant investment in Robber Baron Cave of thousands of volunteer hours, tens of thousands of dollars in grant money, and our own money in restoring it into a neighborhood park and cave preserve for endangered species,” Ranzau said. “It’s important to us.”

The exact nature of the liquid is unclear. Ranzau said it wasn’t raw sewage, though he described faint odors of sewer and chemicals around and inside the cave after the alleged discharge.

SAWS Vice President Donovan Burton said in an email Saturday that SAK Construction was installing a flexible liner inside a length of existing sewer pipe, a technique known as cured-in-place-pipe lining. SAK Construction representatives did not immediately respond to phone messages left with the company’s headquarters and a San Antonio-based project manager.

At this point, we continue to have dialogue with the various parties and as more information is presented, we will look at it further,” Burton said.

Officials with the Texas Commission on Environmental Quality, the State’s environmental regulator, confirmed that its San Antonio office had received a report of a spill at Robber Baron the afternoon of Nov. 7. As of Friday afternoon, its staff were still investigating the incident.

TCMA has retained consulting firm Zara Environmental to study the spill and take samples of the fluid, Ranzau said. As of Friday, TCMA had not yet received lab results.

“TCMA would expect SAWS and the contractor to take reasonable measures to remediate any contaminants found in the cave,” Ranzau said. “In addition, we may seek their assistance in remediating some of the surface damage that’s been caused.”

Ranzau shared photos with the San Antonio Report that show mud, leaves, small rocks, and other debris that have washed into two cave entrances. Other photos show fallen rock from the outside rim of the sinkhole surrounding the cave

The spill affects a cave explored by generations of cavers. Robber Baron is the longest known cave in Bexar County and is home to bat species as well as two endangered invertebrates – the Robber Baron Cave spider and the Robber Baron Cave harvestman, a member of an order of spider-like arachnids known as daddy longlegs. Both have only been observed at the cave.

Inside the cave, volunteers found “significant standing water” in a naturally formed room known as the Pavilion Room, located off the main entrance passage. In several parts of the cave, the liquid brought in outside debris, Ranzau said.

“It brought in a significant amount of material,” he said. “By material, I mean dirt, sand, and debris from the surface that isn’t normally in the cave,” which has a clay floor.

Asked about the incident last week, SAWS officials shared a Nov. 7 photo taken from across Nacogdoches Road. The photo shows a truck with a SAK Construction logo parked alongside the preserve.

A photo taken Nov. 7, 2020, from across Nacogdoches Street from the Robber Baron Cave preserve shows a SAK Construction truck and worker.
A photo taken Nov. 7 on Nacogdoches Road across from the Robber Baron Cave Preserve shows a SAK Construction truck and worker. Credit: Courtesy / San Antonio Water System

Burton, the SAWS executive, had said in a Nov. 9 email that the photo shows “dust and vapor” related to work on a manhole located between the sidewalk and the preserve’s fence line.

Ranzau said the discharge wasn’t merely water vapor and dust.

“There’s a significant amount of splatter on the leaves of the vegetation,” Ranzau said. “Steam doesn’t splatter. Basically, you’d have to have a waterfall effect of water coming down in order to cause the splatter.”


Brendan Gibbons

Brendan Gibbons

Brendan Gibbons is the San Antonio Report's environment and energy reporter.