by Yilun Cheng, Houston Chronicle ProPublica is a nonprofit newsroom that investigates abuses of power. Sign up to receive our biggest stories as soon as theyre published. This article is co-published with the Houston Chronicle and The Texas Newsroom as part of an initiative to report on how power is wielded in Texas. Billionaire Elon Musk is taking issue with a recent investigation by the Houston Chronicle and The Texas Newsroom that raised questions about a flood tunnel project hes pitching to address Houstons chronic flooding woes. But experts said his response,which he did not explain to the newsrooms, isnt supported by facts or data.Last month, the newsrooms reported that Musks tunneling company, The Boring Co., has been lobbying elected officials for months to allow it to build tunnels under Houston for flood mitigation. Boring has proposed digging two 12-foot-wide tunnels beneath Buffalo Bayou the main waterway running through central Houston to carry stormwater out of neighborhoods and toward the Gulf of Mexico during major storms. Experts say, however, that larger tunnels, closer to 30 to 40 feet in diameter, could carry far more water and be more effective. Musk and representatives with Boring did not respond to interview requests or answer questions the newsrooms sent in advance of last months story about whether Borings smaller tunnels would be able to handle the scale of floodwater Houston is likely to encounter in the future. Instead, Musk waited until hours after the story published to post a response on X, the social media company hes owned since 2022.Boring Company tunnels will work and cost <10% of alternatives, his Aug. 28 post read. If more flow is needed, additional tunnels can be built and furthermore they can be route water from many parts of the city, not just one.The post was written in response to a post on X from U.S. Rep. Wesley Hunt, a Houston Republican who helped arrange private meetings with government officials in Harris County and across the state to sell them on Borings flood tunnel plan. Hunt also did not respond to questions from the newsrooms ahead of publication of the original story, but he weighed in on X after the story was published.A lifelong Houstonian and Texas Congressman spoke to the smartest man on planet earth about solving a generational flooding issue in our city that no one else will fix, Hunt wrote. Musks post offered no data or engineering explanation to back up his assertions. So the newsrooms examined his statements, comparing them against flood studies, and interviewed engineering experts, some of whom pointed out key technical and logistical challenges with the Boring plan.One of Musks claims is likely false, and the others are not yet possible to verify with certainty, according to the newsrooms examination.Again, when the newsrooms pressed Musk and Boring representatives to explain the tech billionaires claims, they did not respond. Nor did Hunt. Houstons Buffalo Bayou Park is visible from the roof of The Allen, a nearby condominium, in 2023. The bayou is the main waterway running through central Houston. (Kirk Sides/Houston Chronicle) Would Borings tunnels cost less than 10% of alternatives? Musks proposal carries a lower price tag than the estimated cost of the larger system the flood control district has spent years and millions of dollars studying.But thats partly because the two are strikingly different proposals. Hunts team has said Borings Buffalo Bayou project would cost $760 million, according to internal communications obtained by the newsrooms through public records requests.The countys flood control district, on the other hand, proposed in 2022 tunnels of 30 to 40 feet in diameter for that segment of the system at a price of about $4.6 billion.Since the project is still in the research phase, the county numbers are preliminary. But based on the figures available, Borings proposal would cost closer to one-sixth of the countys estimate not less than 10%, as Musks post suggested. So Musk seems to be exaggerating how much cheaper his system would be. Flood control experts also maintained that the reduced price is somewhat proportional to the reduced capacity of Borings narrower tunnels. Two 12-foot tunnels would provide less than one-fifth of the volume that a single 40-foot tunnel offers.That means they would divert less water from vulnerable areas than one large tunnel.Jim Blackburn, a Houston environmental lawyer and flood policy expert, said while Musks company deserves a fair hearing, cheaper does not automatically mean better.If its a smaller tunnel, then I would expect it to cost less, Blackburn said. Youve got to look at how much flood mitigation you get for the dollars you spend.Emily Woodell, a spokesperson for the Harris County Flood Control District, said the agency needs more information before it can weigh in on any of Musks claims. Wed have to do a lot of study before anything could even potentially move forward, so I wouldnt want to speculate, she said. Until we have a project or another study, wed point people to our website for the reports and data weve compiled to date. Can additional tunnels be built for more water flow? Musks post said if more floodwater needs to be moved, more tunnels can be added. Engineers said it is not that simple.Larry Dunbar, a veteran water resources engineer who has advised Houston-area governmental agencies on drainage issues, said based on size alone, it would take about 11 of Borings tunnels to carry the same amount of water as one large tunnel. Lined up side by side, with enough room between them to keep the ground stable, the full system could span hundreds of feet. That would require securing rights to more land and building more access points for maintenance, he said.And each new phase of construction might bring another round of reviews and mobilization costs, Dunbar said, undercutting the speed and affordability that Boring has touted as key advantages of its proposal. The issues start to just get more and more complicated, Dunbar said. Not that it cant be done, but just to kind of throw out there Oh, if we need more, well just do more well, theres a lot more to it than that.Harris County Commissioner Tom Ramsey, who has an engineering background, agreed. More tunnels would also mean more equipment to maintain, which could drive up long-term costs, Ramsey said.He added that the county would need to decide on the full plan at the outset so all system elements like pumps, drains and outfalls can be designed properly.It would not be simple to just add additional tunnels later, Ramsey said.John Blount, a former Harris County engineer who retired after more than three decades with the county, similarly dismissed Musks suggestion that Boring could just build more tunnels if the initial plan falls short.While working on other infrastructure projects, Blount said, he has come across a number of contractors capable of building tunnels large enough to handle the job properly the first time.You dont start small and figure it out later, he said. This whole concept of putting in 20% of what you need to see if its enough makes zero sense. Buffalo Bayou, which runs through the heart of Houston, floods after Hurricane Beryl made landfall on July 8, 2024. (Raquel Natalicchio/Houston Chronicle) Can Borings tunnels move water from other parts of the city, and will the tunnels work? Musk argued that Borings tunnels could be used in different parts of the city, not just along Buffalo Bayou. Some local officials agreed that Musks tunnels might actually work better for smaller watersheds that do not take on as much water as Buffalo Bayou.Ramsey said he supports exploring smaller tunnels for areas like Hunting and Halls bayous, which run through other parts of the city and also need resources to strengthen their flood protection. The county commissioner publicly called for a closer look at narrower tunnels during a commissioners court meeting in April, after Hunt had pitched him on Borings proposal in February.Its another tool in our toolbox to help mitigate flooding. And certainly with whats happening in the Hill Country, Ramsey said, referring to recent deadly floods in Central Texas, and what continues to happen in Harris County, we need as many tools as we can possibly get.Woodell, with the flood control district, told the newsrooms in August that the agency initially focused on large-diameter tunnels because engineering studies identified them as the most effective option for a countywide system.However, she said smaller tunnels could be a viable solution in certain areas. Since that idea had not been a focus of research, she added, more study would be needed before any such project could move forward.Colleen Gilbert, executive director of the Greens Bayou Coalition a nonprofit that works to protect neighborhoods near Greens Bayou, in northeast Houston said communities in her watershed are desperate for relief as well. They would welcome the massive storm tunnel once proposed by Harris County, she said, but even smaller tunnels would be better than nothing. We would be thrilled to have any and all possibilities looked at, Gilbert said. If Congressman Hunt and The Boring Co. are looking at this, we are delighted to hear it.Experts and officials the newsrooms interviewed, however, still took issue with Musks sweeping statement that Boring Company tunnels will work because it doesnt take into account complexities of the project or that success largely depends on what kind of system the county ultimately wants. In a two-page memo Boring sent to Hunts team in February and that was circulated among local officials in the county, the company framed the pitch as an innovative, cost-effective solution to Houstons chronic flooding.We are confident in our ability to execute this project successfully, wrote Jim Fitzgerald, Borings global head of business development.But Dunbar said the only way to evaluate Musks claim is to focus on the purpose of the stormwater tunnels. If the goal is to build as large a project as possible for the lowest price, Dunbar said, Borings proposal might fit the bill. But if the goal is to shield lives and property from another Hurricane Harvey-level flooding event, he believes the smaller-scale project simply does not measure up. You have to have some underlying reason why you build this tunnel, what youre trying to accomplish, Dunbar said. And I have not heard that Elon has given that answer.Rock Owens, retired Harris County attorney for environmental affairs who represented agencies including the flood control district, said he has seen local officials repeatedly greenlighting massive projects that were not well thought out and led to costly legal battles.He pointed, for instance, to flood control issues along White Oak Bayou in northwest Houston. In a lengthy legal battle that began in 1999, about 400 homeowners in the area blamed the county for approving upstream development without adequate flood control, which they said caused repeated flooding of their homes. The Texas Supreme Court ultimately ruled in favor of the county in 2016. But Owens said even unsuccessful lawsuits are costly and the kind of challenge that could have exposed the county to a substantial damages award.Musks ethos of moving fast and worrying about consequences later, Owens said, only heightens the risk.That works fine in the private sector, but not the public sector, he said. Were not looking at Mr. Musks personal fortune; were looking at the livelihood and lifelong investments of people who live here. Yilun Cheng is an investigative reporter with the Houston Chronicle. Reach her at yilun.cheng@houstonchronicle.com. Lauren McGaughy of The Texas Newsroom contributed reporting.