Consultants say bridge designs meet federal modeling standards; Laredo committee asks council for geomorphology and environmental studies on wall and buoy risks

Consultants from LJA Engineering and SEA briefed a City committee on international bridge expansions and hydraulic design criteria, telling members that the World Trade Bridge HEC‑RAS study is complete and that a hydraulic analysis for the Colombia Solidarity Bridge is scheduled. Committee members repeatedly pressed the presenters to incorporate the potential effects of a recently built state border wall and a proposed federal buoy system into the river modeling and agreed to ask City Council to initiate geomorphology and environmental studies.

"We're your prime engineering firm on the Columbia Solidarity International Bridge Expansion," said Melissa Monttoayor of LJA Engineering, who described the proposed Colombian expansion as a doubling of capacity from eight lanes to 16 by adding two new spans and separating commercial from passenger traffic. Sid Milky of SEA, the project's senior project manager for World Trade, outlined the firms' hydraulic approach and the regulatory review steps with the International Boundary and Water Commission (IBWC). "We believe we've adequately designed the bridges to account for any flood elevation that the HEC‑RAS model tells us is going to happen," Milky said, adding the team includes conservative debris allowances and scour designs where appropriate.

The presentation summarized key technical steps: field cross‑section surveys at the bridge centerline and roughly 500 feet upstream and downstream; insertion of proposed column locations and sizes into the IBWC HEC‑RAS model for the Laredo reach; comparison of pre‑ and post‑bridge design flood elevations and velocities; and iterative adjustments until IBWC and its Mexican counterpart CILA concur. Consultants said World Trade's HEC‑RAS run and conceptual plans are at an advanced stage and that Colombia's survey and hydraulic modeling are planned in the coming months.

Committee members and attendees raised two recurring concerns. First, some referenced an independent geomorphology report arguing that hundreds of miles of newly constructed walls and an extensive buoy system could change flow patterns, increase debris loads and accelerate scour in ways not captured in existing model runs. Second, multiple members said Homeland Security and Border Patrol technical plans for the buoy and wall systems had not been shared with the consulting teams.

"As a rule, my dealings with IBWC ... would never allow a wall of this size inside the 100‑year flood plane," said Steve Lamontia, a committee member who had earlier taken part in the roll call. Milky replied that the consultants have not been provided federal wall or buoy specifications and that HEC‑RAS inputs reflect the IBWC model they were given (an updated IBWC model through 2018), but that the team will ask IBWC how to account for floating buoy systems in the model.

Multiple committee members urged fuller independent study. Henry Solvenia asked which IBWC model version was being used and whether both IBWC and CILA concurred; Milky said the team used the most recent IBWC model available to them (the 2018 version) and expects the binational sections to compare and concur during the review process. Several committee participants emphasized community vulnerability and potential downstream impacts if wall or buoy installations alter water displacement or channel behavior during high flows.

To address the information gap, the committee moved to request that City Council begin—or provide a status update on—geomorphology and environmental studies that specifically consider the proposed wall and buoy system's impact on the Colombia and World Trade projects. Committee members agreed to present the status report to City Council and to pursue placement on the April 20 council agenda so the City can act or request the necessary studies.

The consultants stressed limitations: they said they follow IBWC criteria for HEC‑RAS inputs and that some modeling questions (for example, how a floating buoy field should be represented) are best answered by IBWC, the model custodian. The consultants also described bridge design elements meant to mitigate flood and debris risk—storm‑water capture vaults, larger drill‑shafts and column sizes sized to account for expected scour and debris pressures—and said these features are included in conceptual plans.

The committee's next procedural step is presentation of a status report to City Council asking for immediate geomorphology and environmental studies and for improved data sharing from federal agencies. The meeting closed after members confirmed next steps.

Sources: Committee meeting transcript; consultant presentation remarks by Melissa Monttoayor (LJA Engineering) and Sid Milky (SEA).