Drilling for a well in the Edwards Aquifer was the source of the sediment that came up at Barton Springs Pool this week, forcing the iconic South Austin swimming hole to close for three days, city officials said Friday.

The pool will reopen to the public at 5 a.m. Saturday, the city said.

Thain Maurer with the city's Watershed Protection Department said the water is safe for swimming and that lab tests showed only high calcium levels that would have come from the drilling. The water quality has returned to normal, and the city has issued a stop work order on the drilling and issued a citation against the responsible party, he said.

The city would not disclose who was doing the drilling or where exactly it was occurring since it is an active court case but said the entity had a permit from the state to drill in the Barton Springs Zone of the Edwards Aquifer, a large expanse of land that includes areas south of Texas 45 and west of Manchaca. Drilling occurs often in this area, Maurer said.

Water cloudiness at Barton Springs Pool is a window into potential contamination of the vast, underground segment of the Barton Springs portion of the Edwards Aquifer, one on which well-owners and a prominent endangered species depend.

At least 50,000 people in southern Travis and eastern Hays counties depend on water from the Barton Springs segment of the aquifer, and the area around the springs is the only known habitat for the endangered Barton Springs salamander.

Maurer said lifeguards at Barton Springs Pool first noticed something wrong with the water on Tuesday night, when a reddish brown substance was coming out of the springs. At 12:20 p.m. the next day, a large white plume came from out of the main spring near the diving board, he said, which prompted the city to close the pool. That plume cleared within a few hours.

However, on Thursday at around the same time, another tan-colored plume came out of the springs, Maurer said. When it happened the second time, it confirmed it wasn't just a single random event, he said.

"We were a little better able to focus our efforts and later that afternoon some of our staff identified what they thought was the problem, did some interviews and got very high confidence on the source," Maurer said.

The responsible party has been cited for discharge of sediment from a construction site and could face monetary penalties. However, officials were not able to speculate about what that would include.

No one in the city has any knowledge of something like this — sediment coming into the pool from the groundwater — ever happening before, Maurer said. The pool has been closed because of cloudy waters before, but the cause had always been related to rain events and sediment washing into the area from creeks upstream.

American-Statesman staff writer Asher Price contributed to this report.