This is according to the latest update from K. Friese & Associates, a civil engineering firm officials hired to provide a needs assessment regarding infrastructure improvements throughout the city.
Council took no action regarding the presentation, as the plan is still ongoing.
Caroline LaFollette of K. Friese said the firm decided to focus on 23 areas of interest and analyzed depths and velocities of water based on a 100-year storm event.
"We reordered the areas of interest so the downstream areas were first," LaFollette said, adding the projects included in the Oct. 16 presentation are preliminary concepts and not necessarily final.
The Oct. 16 presentation from K. Friese constitutes the second update from the civil engineering firm—the first was in July—to City Council. This one came with a cost estimate of $15.4 million, but information from K. Freise states certain costs are unknown and therefore not represented in the estimate.
Included in the initial cost estimate is construction, engineering and surveying, but not project-related costs such as additional infrastructure costs, permitting fees and obtaining rights of way and easements, according to K. Friese documents.
"The cost estimates are what we considered to be appropriate for the city of Rollingwood," LaFollette said, adding other costs associated with the assessment will be added in the final presentation to the city.
K. Friese representative Joe Cantalupo said in July some of the first actions the firm took involved field work to get a sense of what the city was looking at, as well as extensive public outreach. Survey respondents identified property flooding as one of the larger issues for the city, Cantalupo said.
As part of the Oct. 16 update, the K. Friese team refined areas of interest, developed project concepts, created high-level cost estimates, prioritized projects and developed detailed concepts for the city’s top projects, among other initiatives.
Of the 23 listed, the top five drainage improvement projects K. Friese initially identified are for areas within Bee Caves Road; Edgegrove Drive; Nixon Drive and Pleasant Roadway; Pleasant Drive; and Timberline and South Crest drives.
Cantalupo said in July because elements of the study are based on 100-year flood plains, the report is also considering an updated national rainfall study called Atlas 14. That study has shifted the definition of flood plains, meaning they now or could soon cover more land throughout the country, which could have implications for Rollingwood’s infrastructure improvement plan.
During the October 16 presentation, Cantalupo said some communities have adopted what are currently considered 500-year flood events as 100-year flood events. That strategy is pursuant to the findings of Atlas 14, and it is one standard Rollingwood officials could take in consideration of this needs assessment, he said.
"What you need to be aware of is that it will have a financial impact," Cantalupo said.
The next presentation from K. Friese regarding the infrastructure needs assessment has not yet been scheduled.