HARRIS COUNTY (Covering Katy News) - Since Hurricane Harvey decimated the Houston area there has been a great deal of talk about building flood tunnels to carry stormwater from the Houston area to the Houston Ship Channel. Now the Harris County Flood Control District is revealing that it's been working with a team of underground construction experts to take an initial look at the feasibility of constructing large-diameter, deep tunnels to move stormwater.
Underground tunnels could supplement existing bayou and creek capacity to reduce flooding in Harris County. The study was the first phase of a multi-phase test. It looks at the amount of water that could be carried by tunnels, the cost of building tunnels, and whether our soil can support the tunnels. The study is also looking at flood tunnels that are in place in other locations around the world.
Washington, D.C., currently has two large underground tunnels that were built in part for flood mitigation purposes.
"Our analysis of the geotechnical conditions indicate that the soil and groundwater conditions in Harris County are similar to Washington, D.C., and could potentially be even better for tunneling," said Brian Gettinger of tunneling services company Freese and Nichols. "This is a key factor in the phase-one study as it validates that large-diameter, deep tunnels are constructible in Harris County."
The deep tunnel concept has similarities to a 1996 Flood Control District feasibility study that considered a trenched box culvert system along the Interstate 10 right of way. Unlike the 1996 study, the large-diameter tunnel concept has the potential to convey much larger flow rates and to convey the flow all the way into the Houston Ship Channel.
Preliminary estimates prepared during the phase-one study show that 10-mile-long, 25- and 40-foot-diameter tunnels would cost approximately $1 billion and $1.5 billion, respectively, to construct.
Harris County Flood Control District funded the phase-one study through a $320,000 grant from the U.S. Economic Development Administration and an $80,000 cost-share from the Flood Control District's 2018 Bond Program. Considerations for the next phase of the study are currently in development.