The Harris County Toll Road Authority plans to take a three-week pause in construction on the new Houston Ship Channel Bridge along the Sam Houston Tollway so engineers can agree on a solution to a possible design flaw found nearly 20 months into the project.

The $1 billion bridge — the costliest infrastructure project in the county’s history — was designed by the Dallas office of FIGG Bridge Group. The company, based in Florida, came under scrutiny when its Tallahassee office designed a pedestrian bridge that collapsed in February 2018 at Florida International University, killing six. FIGG and its consultants were held responsible for the collapse.

“Errors in bridge design, inadequate peer review and poor engineering judgment led to the collapse of this bridge,” National Transportation Safety Board Chairman Robert Sumwalt said three months ago when findings were released.

Weeks after the collapse, HCTRA officials said they were sticking with FIGG as designers of the new Ship Channel Bridge. Still, last March, Harris County approved a $2.6 million contract with COWI, an international consulting and engineering firm, to review the FIGG designs.

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Late last year, COWI approached FIGG with the design concern, and both started working on a solution, said John Tyler, deputy director of the Harris County Toll Road Authority and the agency’s chief engineer. The construction pause, he said, will allow for the two companies to finalize the plan for the solution developed by FIGG and approved by COWI and restart work.

“We wanted to have the design agreed to before we proceeded,” Tyler said.

This is the second delay confirmed on a Texas span so officials could double-check FIGG’s design. In November, despite previously saying it was satisfied by the company’s performance, the Texas Department of Transportation suspended construction of the new Harbor Bridge in Corpus Christi, citing the Florida bridge investigation and the need to review FIGG’s work.

The company, in a statement, said it is “working collaboratively to satisfy both COWI’s and FIGG's reviews.”

FIGG officials said “it is typical for two independent engineers to have some differences.”

The Ship Channel Bridge delay affects only the construction of the two massive pylons that support the bridge as it spans the channel, Tyler said. All construction related to the approaches and widening of the tollway on both sides of the bridge will continue unaffected, he said.

The potential flaw involves the load capabilities of the pylon design, and whether a specific part of the tower adheres to best engineering practices as the curved part of the pylon rises. Tyler said the point in question is about 60 feet in the air, well below the roadway where vehicles will cross the busy Ship Channel.

The hiccup could delay the bridge’s opening day, despite having four years to go.

“Until we get to the end, we don’t know, but it could delay,” Tyler said.

“We are committed to this bridge, and the bridge is under construction,” said Harris County Precinct 2 Commissioner Adrian Garcia. “… That said, we cannot compromise on any issues related to public safety.”

Replacing the current ship channel bridge is a monumental task, which will compete in size with the region’s largest monument. The towers of the new bridge — really two bridges that will be built inches from one another — will rise to 514 feet, 53 feet shy of the San Jacinto National Monument just upstream along the channel.

The towering curvy concrete pylons are firmly planted on massive concrete bases, anchored by concrete shafts driven 240 feet into the boggy Texas turf along the ship channel.

Cables strung through the towers will support the roadway, built with pre-cast segments away from the pylons. The road will remain about 175 feet above the ship channel, around the height of the current bridge.

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What is different about the bridges will be the distance between the supports. The current bridge’s center columns sit just inside the ship channel itself, 750 feet apart. The new bridge’s pylons are outside the channel, with a quarter mile between them.

That wider space allows for a major Port of Houston priority: deepening the channel and allowing for more room for ships to maneuver.

The new bridge will also have capacity to carry far more vehicles, where officials expect demand to surge by 2035 to about 158,000 vehicles daily, up from the 60,000 that use the bridge now.

The current delay, and any ensuing delay to the schedule of opening the bridges, is unlikely to have an effect on the port, spokeswoman Lisa Ashley said.

“It does not cause us any major concern at this point because it is so early in the process,” Ashley said.

Construction of the Ship Channel Bridge began in April 2018, after more than five years of discussion and planning. At the time, county government was vastly different: Garcia had yet to take charge of Precinct 2, and Harris County Judge Lina Hidalgo was months from her upset win over then-judge Ed Emmett.

Garcia said that although he was not involved in the project’s development, it is his responsibility to make sure “it doesn’t become a money pit.”

“Do I want to see this bridge built? Yes,” Garcia said. “But we’ve got to make sure we don’t turn a blind eye to any concerns.”

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Though Garcia and Hidalgo have in the past year balked at the massive cost of the bridge and said the county needs to focus more on transit and alternatives to more freeways, the bridge remains a major priority for some commuters. A new bridge is needed because businesses rely on trucking to and from the Port of Houston and safer operations of the ship channel itself.

“It also allows us to widen it, which is a huge deal,” Precinct 3 Commissioner Steve Radack said of the ship-clogged channel. “This bridge is necessary and extremely important.”

BRIDGE BUSINESS Three companies have a large role in the construction and design of the new Ship Channel Bridge: Figg Engineering Group, designers The company is known for some of the most striking, complex spans in the United States, including the existing Ship Channel Bridge, the Veterans Memorial Bridge in Port Arthur and the new Harbor Bridge in Corpus Christi, currently under construction. Traylor Brothers, bridge builders Anyone who drives freeways in the Houston area likely has driven on Traylor’s work at some point. The company’s bridge division, part of the larger Indiana-based firm, built the Galveston Causeway and the raised the portion of Interstate 45 through downtown, commonly called the Pierce Elevated. Zachry Construction, general road builders San Antonio-based Zachry is one of the state’s largest road builders, responsible for the ongoing widening of the Sam Houston Tollway and the latest segments of the Grand Parkway from U.S. 290 to U.S. 59/Interstate 69 near Kingwood.

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He called any attempt to scale back or cancel parts of the bridge project “ridiculous.” Contracts for the design and construction are signed, construction is underway and everyone is demanding a safer bridge with more capacity, he said.

“You end up basically paying $700 million and having nothing to show for it,” Radack said.

dug.begley@chron.com