UPDATED Oct. 9, 10:53 a.m.
Travis County commissioners met today and received information on estimated fiscal impacts to the 2017 bond projects, should they choose to revise construction plans based on recently published rainfall intensity data. While no action was taken today, further updates and possible decisions are expected over the coming months.
“We’re leading by example because we have to,” County Judge Sarah Eckhardt said. “Of course we will be early adopters. We have a lot of people who will be impacted.”
Original post: Oct. 5, 2:00 p.m.
In light of rainfall intensity data published by the
National Oceanic and Atmospheric Administration Sept. 27, Travis County commissioners will consider taking a vote Oct. 9 on whether to alter construction plans for the county’s 2017 bond projects. The decision could increase the cost by approximately $31 million for these projects alone, and would likely delay the overall timeline as well.
“There will be costs associated with this either way,” Travis County Judge Sarah Eckhardt said July 31, when the commissioners
voted to assess possible early adoption of new standards. “I would prefer the costs be financial rather than in lives.”
In Nov. 2017, voters approved a
$185 million bond for roadway and park improvements. The county also committed $94.9 million to critical safety projects that do not require voter approval. Cost estimates for these projects, collectively referred to as the 2017-2022 bond program, were based on rainfall data prior to Atlas 14—the NOAA study that uses new rainfall intensities to define a 25, 100 and 500-year storm.
The existing definition of a 100-year storm is based on decades-old data. The new data, which was collected through 2017, defines a local 100-year event as 13 inches in a 24-hour period, which is approximately the current 500-year rate.
Rainfall intensity data is used by FEMA to produce flood insurance rate maps and by engineers to design detention ponds, storm sewers and road side drainage systems. Atlas 14 data for Austin and Travis County suggests drainage systems will need to be bigger to handle the newly redefined events.
Public and private sector development projects will feel the pinch as associated costs rise. K Friese and Associates—a civil engineering consulting group contracted by Travis County as the general engineering consultant for the bond projects—predicts an 11 percent increase, or about $31 million, to the total cost of the 2017 package. Individual components of the projects, like bridges and storm drains, could see a 15 to 30 percent cost increase if commissioners vote to adopt the new standards.
It will take years for flood modeling to reflect the new understanding of rainfall intensities. However, the vote on Tuesday could solidify the commissioners' July 31 intention to evaluate proactive steps to amend development standards ahead of the new models.
