As Broward County officials favor building a new bridge for trains to cross downtown Fort Lauderdale’s New River, they’re raising fresh questions about a second option — the feasibility of creating a train tunnel instead.

Some key questions about the tunnel focus on the risk of excavating underground, the environmental and traffic impacts, as well as the costs to buy private property, according to a four-page memo recently sent by Kevin Kelleher, Broward’s assistant county administrator, to the city of Fort Lauderdale.

“While the conceptual design of a new, shorter tunnel alternative presented by the city’s consultants initially appears to offer certain advantages, the county has identified several concerns that have not been addressed and could significantly increase the estimated cost of a tunnel and otherwise further confirm our Board of Commissioners’ view that a tunnel alternative is not feasible,” Kelleher wrote.

The county has been in talks with the city of Fort Lauderdale — with an aim toward upgrading how trains get past the New River, and bolstering the region’s growing railroad network. But disagreement has loomed large about what the best plan would be. Some leaders in the city of Fort Lauderdale are still hoping that a tunnel is the answer.

Fort Lauderdale Mayor Dean Trantalis, who has championed the tunnel, considers the county’s latest memo as a way to try to end the other idea. “The county administration has their head in the sand and has no interest in listening to alternatives to the New River crossing,” he said. “They seem to think their way is the only way. They would rather do something now than do something right.”

Here’s a look at the county’s recent concerns about the tunnel idea.

Private property

There already exists a New River drawbridge in downtown Fort Lauderdale, erected in 1978. The cross sections of a new shorter, shallower tunnel could mean tunnel borings end up passing through piles that support the existing New River train bridge. “The city’s consultants indicated the possibility of placing new piles and removing impacted existing piles,” the memo says.

A tunnel would need to be built outside the right-of-way, which means it would require private property acquisition. And that “would add significant costs and time delays to the tunnel design and construction process,” Kelleher wrote.

Unless Brightline and the Florida East Coast Railway agree to modify the infrastructure that’s already existing, “the latest tunnel proposal cannot be confirmed as technically or financially feasible,” he wrote.

Flooding and other tunnel challenges

The county urged the city to study flooding and other “risks caused by tunneling through fragile geological formations in close proximity to new and historic buildings.”

The county’s memo brought up the June 2021 collapse at Champlain Towers South that left 98 people dead in Surfside. Investigators with the National Institute of Standards and Technology have been looking into two dozen different scenarios and potential contributing factors that could explain why the building collapsed, including vibrations from nearby construction.

Kelleher’s memo cited concerns about any potential vibrations that could come from creating a tunnel. “The risks of ground movement/settlement caused by vibrations during excavation are of particular concern, given the recent Champlain Towers disaster in Surfside, Miami-Dade,” Kelleher wrote.

Flooding remains a prevalent concern in South Florida, demonstrated on April 12 last year when a storm system dumped nearly 26 inches of rain within 12 hours in the Fort Lauderdale area. “The risk of flooding is high in the area proposed for the new tunnel and was clearly demonstrated during last year’s serious flooding event,” Kelleher wrote.

PortMiami has a tunnel that’s designed to improve traffic in downtown Miami. Broward County recommended obtaining “complete cost information” for PortMiami tunnel’s flood gates, as well as similar projects, “to confirm what those actuals costs may be” for such a tunnel in Fort Lauderdale.

Environmental and traffic impacts

An estimated 10,000 dump trucks would be needed for a tunnel project. Residents will see a “significant disruption to their quality of life during an extended construction period,” Kelleher wrote.

Kelleher wrote that during the construction of the PortMiami tunnel, the processing and disposal of excavated materials was challenging, “including some materials that may be contaminated by hazardous substances.”

Although the originally specified staging area of Sistrunk Park to keep excavated materials was “premature” and could be substituted by other locations, “the anticipated impacts associated with the processing and transfer of excavated materials in the vicinity of the tunnel portals, including de-watering, treatment of any contaminated material, and the traffic impacts caused by the large number of dump trucks (estimated at 10,000 or more) that would need to circulate in the vicinity of the staging areas during construction, would need to be addressed, which would likely add more costs and time to the proposed project,” he wrote.

He said it was also important that residents in the area know that it could “likely cause significant disruption to their quality of life during an extended construction period.”

Station design

While previous cost estimates for the tunnel and bridge alternatives included the cost of a commuter rail station in the vicinity of the existing downtown Fort Lauderdale station of Brightline, the county said the city’s consultants only included the cost of a new underground Brightline station, leaving out cost estimates for a commuter rail station.

To compare “apples to apples,” it is necessary to account for these differences, either adding commuter rail station costs to tunnel estimates, or removing these costs from any past or future bridge cost estimates, Kelleher wrote.

Moving forward

Government officials do agree they need to move forward with plans for a regional mass transit system that will get people out of their cars and transport them from Palm Beach County to Miami-Dade County and all points in between.

All nine Broward county commissioners and three Fort Lauderdale commissioners have previously made it clear they prefer a bridge, saying it will be much cheaper than a tunnel.

But while the Fort Lauderdale commission agreed last month to accept a train bridge over the New River, it was only on the condition a tunnel is not feasible.

But right after that vote, all five commissioners agreed to pay the outside consultant BDO USA up to $325,000 to research the costs of building a tunnel along with the eminent-domain costs related to building a bridge through the downtown. (At a City Commission last month, officials discussed how the train bridge plan could face its own hurdles due to the potentially high costs from buying private property.)

According to BDO, a tunnel can be built for $880 million without requiring the taking of private land. The consultant’s preliminary report came out earlier this month, and a more thorough report is expected.

Still, the Fort Lauderdale consultant’s proposed plan creates “potential right-of-way issues and other potential structural issues, as well as a lack of addressing resiliency and other environmental concerns,” said county spokesman Gregory Meyer. “To date, there has not been an alternative tunnel option that is technically feasible, cost effective or financially responsible to pursue as an option.”

Broward Commissioner Lamar Fisher said the county is expected to continue to push for the bridge and he would need to know financing is available to change his mind otherwise. “Commuter rail must happen, there’s no alternative,” he said.

Mayor Trantalis said of the city-county relations: “We’re trying to work on this in good faith, and we don’t feel the county administration is acting in the same way.” Business interests also have stepped forward in favor of the tunnel.

According to state transportation officials, a 3.25-mile tunnel from Southwest 15th Street to Sunrise Boulevard would cost $3 billion — six times the cost of a $500 million bridge.

Trantalis says he thinks the tunnel can be done cheaper. He said a bridge would ruin the downtown, and that a tunnel is best for both commuters fighting gridlock on the road and boaters who would have to wait on a drawbridge.

Kelleher, the county’s assistant administrator, warned about the perils of the two governmental bodies working independently, writing in his memo: “We were surprised to hear that the city’s consultants are being asked to review grant funding and other financing opportunities for tunnels. … On a related note, we are also concerned about the risk of sending conflicting signals to potential federal and state funding agencies for a county project, especially as we continue to hear about the city’s plans to seek grant funding from federal and/or state agencies in the April 2024 timeframe.”

Fort Lauderdale Commissioner Steve Glassman said he feels the two governments are “talking past each other.”

“It’s almost like the sides are digging in,” he said.

But he knows what his constituents tell him: “The residents are adamant they do not want a bridge, adamant. We have to explore all possibilities. This is a legacy project. The citizens of Fort Lauderdale do not want to see a bridge through their neighborhoods.

“I wish we worked more collaboratively. This is too important.”

Lisa J. Huriash can be reached at . Follow on X, formerly Twitter, @LisaHuriash