Harris County Flood Control District proposes tunnel idea to drain stormwaters

Downtown Houston is shown with Buffalo Bayou rising with floodwaters from Tropical Storm Harvey on Monday, Aug. 28, 2017, in Houston. ( Brett Coomer / Houston Chronicle ) Downtown Houston is shown with Buffalo Bayou rising with floodwaters from Tropical Storm Harvey on Monday, Aug. 28, 2017, in Houston. ( Brett Coomer / Houston Chronicle ) Photo: Brett Coomer, Staff / Houston Chronicle Photo: Brett Coomer, Staff / Houston Chronicle Image 1 of / 5 Caption Close Harris County Flood Control District proposes tunnel idea to drain stormwaters 1 / 5 Back to Gallery

The Harris County Flood Control District is exploring the possibility of building several massive, deep tunnels aimed at keeping storm water out of flood-prone neighborhoods and carry it underground for miles to the Houston Ship Channel during major storms.

Never before tried around Houston, the project likely would cost several billion dollars and it is not clear where the money would come from, officials said. Specialized machines methodically digging 100 to 200 feet underground would take several years to complete the tunnels, which would seek to drain floodwaters from bayous across the county.

Officials with the flood control district said the idea could be a bold answer to the devastation wrought by Hurricane Harvey, and dramatically improve Houston’s defenses against deadly floods where other strategies have fallen short.

"What the flood control district has been doing for decades doesn't occur fast enough or it doesn't have the benefits that the public really wants," said Matthew Zeve, director of operations at the flood control district. "We've been challenged to try to think of new ideas and new strategies and this is an answer to that challenge."

Commissioners Court is slated to vote Tuesday on whether to pursue a feasibility study to examine the tunnel proposal in detail, charting out the exact paths of the tunnels, where intake shafts would be located and how to address any environmental or structural constraints.

The full project envisions a network of tunnels across the county to carry water from several of Houston’s waterways, including White Oak Bayou, Hunting Bayou, Greens Bayou, Halls Bayou, Buffalo Bayou, Clear Creek and Cypress Creek. The goal under the plan would be for those waterways to be able to keep a 100-year storm event within their banks.

That would remove tens-of-thousands of homes and buildings from those waterways’ 100-year flood plains.

A 100-year storm refers to rainfall that has a 1 percent chance of occurring in any given year, and typically ranges from 12 to 14 inches in 24 hours. Houston has suffered a 500-year flood each of the last three years. A 500-year storm has a .2 percent chance of happening in any year.

A feasibility study is expected to cost around $400,000 and be completed by October.

News of the proposal fueled optimism and skepticism Friday — optimism that Harvey finally could force radical changes to Houston’s flood control strategy, and skepticism that such a monumental project could be accomplished when much less ambitious ideas have languished for decades.

Rep. John Culberson, R-Houston, said in a statement he is “encouraged” the flood control district “is thinking outside the box and plans to conduct a feasibility study on this proposal. It certainly seems like this type of project could be partially funded by FEMA hazard mitigation grants and, perhaps, through other federal sources, as well.”

Houston’s flood czar, drainage engineer and former city councilman Steve Costello, said the project could be a potential paradigm shift for the region’s flood risk.

“We’re trying to lower the risk; we’re never going to be able to totally eliminate the risk,” Costello said, referencing efforts to improve drainage through local projects. “Well, a tunnel system, quite possibly, could eliminate the risk.”

As expensive and complex as it would be - Costello said he was told it could cost perhaps $100 million per mile, in Houston’s soils - he said tunnels may be the most cost-effective way to achieve the gold standard of 100-year storm protection in every major channel.

Jim Thompson, regional CEO for engineering Giant AECOM, said the tunnels are “worthy projects” that warrant further study, but said officials ought to prioritize long-identified projects along bayous and city streets first.

“Would it provide the cure-all relief that everybody is seeking? No,” Thompson said. “Would it provide a noticeable decrease in flood levels and risk of flooding? The answer is possibly yes.”

Auggie Campbell, CEO of the West Houston Association, which has advocated for getting all local waterways to the 100-year standard, suspects it would be cheaper to buy adjacent properties and widen natural channels in areas where land is cheaper and tunnel in areas where buying every parcel would be prohibitively expensive.

The association concluded it would cost $6 billion to run a flood tunnel from the Addicks and Barker reservoirs to the Port of Houston, for instance, and decided excavating the reservoirs deeper was a better option.

“It’s going to cost about $75 million to $100 million a mile for these flood tunnels, and so there are places where that’s as cheap as it’s going to get,” Campbell said. “There are some places where our folks thought it’d be better to lay back the banks and make room for the bayous using natural channel design ... like on Sims Bayou.”

A spokesman for Harris County Judge Ed Emmett said “it will take a lot of persuading for (Emmett) to move forward with this in terms of whether this is a more cost-effective way than traditional methods to resolve some of the long-term, chronic flooding problems.”

“There’s no way that the county could move forward with this project on this scale, without significant help from the federal government and the state of Texas,” Emmett spokesman Joe Stinebaker said. “This is not a project at this point that the judge sees the county taking on alone.”

A spokeswoman for Gov. Greg Abbott said it was too early to comment on the idea.

Zeve said that compared to traditional methods of reducing flood risk — widening bayous, conducting buyouts — the tunnel project would displace and disrupt far less people. He said special machines could construct the tunnels without causing disruption on the surface, and that the flood control district could use existing interstate freeways and other major thoroughfares as routes the tunnels could follow.

While bold, the tunnel idea is not an unfamiliar concept.

In 1996, the flood control district commissioned a study that proposed a tunnel beneath Interstate 10 to carry water out of the reservoirs to a discharge point 12 miles east. The cost was estimated at $325 million to $400 million, but officials never moved forward with the project.

Other cities, including San Antonio, Austin and Chicago, have employed tunnel drainage systems. In February, Dallas voted to award a contract to Southland Mole JV to build a five-mile underground tunnel, 70 to 150 feet underground, that would provide drainage relief to the eastern parts of the city.

Harris County’s proposal by far would be the biggest.

David Conrad, a water resources policy consultant with the Association of State Food Plain Managers, said more and more jurisdictions are building tunnels to relieve flooding. He called the concept “tested.”

“It sure makes sense to me that the community would explore all the potentially viable options,” Conrad said. “The answers are probably a rather complex selection exercise.”

mihir.zaveri@chron.com

mike.morris@chron.com