Bee Cave City Council discussed and approved an engineering report providing a proposal for the low water crossing improvement project at Great Divide Drive.
How we got here
The current crossing at Great Divide Drive consists of three pipes with a capacity of about 60 cubic feet of water per second. However, a two-year rain event, like the storm the city faced in May 2019, moves about 2,800 cubic feet of water per second.
A two-year event is a storm, flood or rainfall event that has a 50% chance of occurring or being exceeded in any given year.
The Homestead neighborhood is only accessible through Great Divide Drive, creating challenges for residents and first responders to enter and exit the neighborhood when the low-water crossing floods.
In 2023, HDR Engineering, the contracted engineering firm for the project, presented two proposals to City Council for a bridge at the low-water crossing site.
One proposal consisted of constructing a 200-foot bridge, while the other included the use of eight culverts, or water tunnels.
Bee Cave Mayor Kara King made a motion to approve the construction of a 200-foot bridge, but it failed to pass due to concerns surrounding the effect on neighboring properties. No motion was made on the culvert option.
The details
Now, HDR Engineering is proposing a design that would incorporate nine bridge class box culverts, large-scale drainage structures, that could manage a two-year storm like the May 2019 event, according to city documents.
“We really keep the profile of the existing road… . It improves vehicular safety,” Brandon Metry, hydraulic coordinator at HDR Engineering, said. “Previously, the idea was, ‘We need a bridge,’ and now it’s shifting toward, ‘We are maintaining the low water crossing concept.’”
At the existing crossing at Great Divide Drive, it would take 25 minutes for water to rise and flood during a two-year storm event, whereas with the new proposal that timeframe would be extended to 55 minutes.
Water overtopping the road during a two-year storm event currently lasts 13 hours, whereas the new proposal would bring that time down to three hours, according to HDR Engineering.
What else
The total cost of the project, including construction cost, right-of-way acquisition and engineering, is approximately $1.16 million, per city documents.
“I feel confident that this gives us the best solution without impacting the neighbors,” King said. “[The proposal] is still a significant improvement over what we have now.”
The entirety of the project is expected to be completed in two years, with construction lasting for six months.
