AUSTIN (KXAN) — Workers discovered another cave beneath a Round Rock Independent School District high school while doing utility work at the end of June.

Round Rock ISD uploaded photos of what it calls “cave No. 19” on Thursday, showing stalactites and stalagmites in the space. It said on Facebook that the cave is the biggest yet, adding that it was discovered about two weeks ago when the contractor and city were doing water line utility work. 

“There is an extensive cave system underneath the school, which was built in the 1980s, but 19 have been found during construction,” said Jenny Caputo with Round Rock ISD.

McNeil High School at 5720 McNeil Dr. is going through a series of renovations. Phase One includes upgrades to special education, administration and fine arts buildings. These updates experienced delays because of caves found to the west of campus, some of which had an endangered species of spider inside.

The district eventually came to an agreement with the U.S. Fish and Wildlife Service to continue work.

Terry Worcester, the chief operating officer at Round Rock ISD, said that the district is working with engineers and environmentalists to determine how safe the caves are and what steps may need to be taken to address that. “There’s a protocol for all of those findings,” Worcester said, “and we follow those very, very closely.”

The Texas Commission on Environmental Quality already sent staff members to view the cave and coordinate with crews working at the site, according to Brian McGovern with TCEQ media relations. 

He also said that McNeil High School is located over the Recharge Zone of the Edwards Aquifer, and is required to comply with certain requirements regarding sensitive features discovered during construction.

TCEQ rules require holders of approved Edwards Aquifer protection plans to immediately notify the regional office of any sensitive features discovered during construction:

Regulated activity in the vicinity of the feature must be suspended. Regulated activity may not proceed until the agency has reviewed a geologic assessment report prepared by the responsible party’s geologist, and approved methods proposed by a Texas licensed professional engineer to protect the sensitive feature and the aquifer from adverse impacts. 

Round Rock ISD is unsure how much more the caves are going to cost the district to address since the process is ongoing, according to Worcester. He added that construction is still moving ahead at the high school. Crews are expected to complete the improvements to the special education addition by November. 

In 2015, cave discoveries and equipment failure caused delays in a water line construction on McNeil Drive.