Maintenance work on Rio Vista Falls, which has caused a portion of the San Marcos River to be closed since October, will continue through mid-May.

The closure runs from above the falls in Rio Vista Park and under the bridge at Cheatham Street. The $966,000 project initially was projected to be completed in March, but delays—some of which resulted from vandalism to the blue water-filled barriers used to drain the river and divert water for foundation work on the river bed—have extended the timeline of the project, said Greg Schwarz, a senior engineer with San Marcos Capital Improvements and Engineering.

He said the project, which is being completed by Austin Filter Systems Inc. Construction, might end up costing up to $100,000 over the initial amount due in part to those delays.

“On several occasions, they've been sliced overnight, and the contractor comes back, and the work area is filled with water, so he's got to patch those barriers, reset everything up and pump water out,” Schwarz said.

In 2006, the city initially transformed the area from a single dam into three sets of rapids. No maintenance to Rio Vista Falls has occurred since, according to a press release. The structures have endured strong rapids and three major flooding event in that time, and that created underwater voids, undercuts to the bank and instream structures.

The scope of the project includes deepening the foundation toe of the bank and instream structures and adding a protective layer of rock around the foundation. Work is mostly complete on the two rapid structures that are more upstream, but the downstream structure is requiring added work, Schwarz said.

“We had concerns about its integrity and lasting for many years in the future. It also had a unique characteristic to where it kind of directed, concentrated flow towards the left bank, left bank as if you're looking downstream. And we think that that contributed to the failure of that bank,” Schwarz said. “We are now in the process, the contractor is in the process of redoing that chute. And once he does that, he has a little more bank work to do in that area, and then they will be done and finished with the project.”

While most of the work on Rio Vista Falls is underwater and foundational in nature, most of the work will go unnoticed once the falls reopen, Schwarz said. The third chute downstream, however, will have notable changes with a slight change in flow allowing for a walking path for pedestrians due to better stabilization on the right bank.

“There is a connection between the most upstream structure and the middle structure, and there's also a connection between the middle structure and the downstream structure and also a connection between the downstream structure and the Cheatham Bridge area,” Schwarz said. “So that'll be something that will be new for people to experience.”

Another portion of the river will be closed off upstream once the Rio Vista Falls project is complete at Pyramid Park/Dog Beach, Schwarz said, though for that project, half the width of the river will be closed off and dewatered for structural work on the bank. The opposite bank at City Park will be open and flowing for river access. That project is anticipated to take less than two months to complete.