Rio Vista Falls maintenance project continues with completion expected in mid May

Maintenance work at Rio Vista Falls is expected to continue until mid May following several delays caused by vandalism, weather and additional work needed on the project. 

City of San Marcos Senior Engineer Greg Schwarz said the project was delayed from its original March timeframe because of challenges of dewatering the river to allow access for construction as well vandalism to the barriers keeping the water out of the work area. 

“Anytime we get rain, that causes delays,” Schwarz said. “Then there was just more work. We can’t always see everything. We did our best to inspect it underwater but more things needed to be addressed. We also had the pipes underground [to move water around the project], some of the joints were leaking and they were leaking enough … and they were flowing pretty good so we had to figure out what was going on and how to address that. I think one of the big things is just that dewatering this was a challenge and keeping it dry enough to construct.”

Additional work needed on the project and delays are estimated to cost the city an additional $100,000. The project, which is being done by Austin Filter Systems Inc. Construction, was originally expected to cost the city approximately $970,000. 

Maintenance work is being conducted to address instream structures and bank improvements. According to the City of San Marcos, underwater voids and undercuts formed in the bank and instream structures throughout the Rio Vista Falls area and required maintenance. 

The Rio Vista Falls area was reconfigured from a single dam into three sets of rapids, outline pool area and decorative boulders in 2006. Prior to the currently ongoing project, maintenance hadn’t been done to the area since its original construction, according to the city. Additionally, the city said strong currents and three major flooding events impacted the structures since their installation.

The work being done consists of repairing voids, undercutting and deepening the foundation toe of the bank and instream structures. An additional protective layer of rock armoring has been installed around the foundation.

“Things were just slowly starting to fall apart,” Schwarz said. “The voids would just get bigger and bigger and then rocks would start to collapse. What’s really dangerous is what had developed was there’s tunneling of water underneath the structure where a little whirlpool starts to form upstream … It’s super dangerous. We noticed it  and we did a quick repair on it like a Band Aid to last us through until we could get to this project.”

The Rio Vista Falls project has been conducted in multiple phases, which included installing  temporary chain link construction fencing and rope connected safety buoys within the river to prevent the public from entering the construction area. Work also included the installation of erosion control measures to prevent sediment from entering the river. The river was then dewatered from the area around Rio Vista Falls, which included the removal and relocation of  fauna, including the endangered fountain darter. 

“When we dewatered it, we had aquatic biologists come in and use nets to remove all the turtles and fish, and in particular any fountain darters which are endangered, and relocate them into the river,” Schwarz said. “Anytime we get a big rain event and water comes over and it fills this back up and we think there’s a connection to the river where fish and wildlife got back in then we pump it back down and we call them back out and do it again. That’s happened quite a few times.” 

Following dewatering, key stages of the project include the construction of the repairs, reintroduction of river flow back into Rio Vista Falls and the construction’s completion.

Schwarz said the goal is to complete the project by mid May. 

“They’re working 10 hour days, six days a week. I think working with the consultants that we worked with they’ve come up with a solution that’s really going to make this area last much longer than the previous original improvements lasted,” Schwarz said. “We shouldn’t be back in this situation for a long time doing this expensive of work.”  

Schwarz also said the project will help keep a balanced river ecosystem.  

“I think there’s issues with erosion and failing banks. Sediment in the river can be an issue for aquatic species and not just fish but also plants,” Schwarz said. “So, making sure we have stable banks and banks that are not eroding is important. I think too, having a resource where the public can access the river in a way that’s not greatly impactful and allows other areas to remain more natural, if you provide specific locations where the public can come and enjoy the river that allows for other areas of the river to keep it much more natural.”

Following completion of the Rio Vista Falls project, additional work will be done upstream at Pyramid Park/Dog Beach to address similar issues, Schwarz said. But the river will remain half open for residents and visitors to access the river across the bank at City Park. 

“Near the water’s edge [at Dog Beach] a lot of the stones are fine but there’s maybe half the stones at the water’s edge are turning over and falling in the river,” Schwarz said. “Similar issues are happening there where the stones are getting undermined so we need to go in with this exact same process of putting a deeper foundation … But it’s the kind of thing that we noticed it early and we’re going to address it. Time wise, it won't take nearly as long as it’s taken to do this. Of course, the river will be half open so they’ll be able to dewater just the portion around Dog Beach.”