A new report questions a fundamental premise of Key Biscayne’s response to climate change, suggesting that a series of limited, localized flooding projects using existing drainage lines may be preferable to the massively expensive course of action being pursued by the island’s administration, estimated to cost $320 million village-wide.
Already, the report is causing some leaders to reconsider the pathway for Zone 1 of the Big Dig project, which is 100% designed by the AECOM firm and is ready to be sent out to bid. The GIT Consulting report will be the focus of a Village Workshop meeting Thursday.
“In engineering, we have a saying, there’s 1,000 ways to skin a cat,” said Council Member Fernando Vazquez, an environmental engineer who has — up until now — been solidly behind the large pump system recommended by his former firm, AECOM. “Perhaps we are in a position of re-imagining how we should approach drainage.”
He continued: “I am opening the door to allow this to present itself and see what it allows.”
If Vazquez were to add his voice to longtime Big Dig critic Ed London, another council member, it could delay further the Resilient Infrastructure Adaptation Program, the project’s formal name.
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A supermajority of five votes is required to borrow funds under the Village Charter. Council Member Michael Bracken has also raised questions about the AECOM plan, but has sided with the majority in approving spending so far.
But Steve Williamson, the village manager and former Army Corps of Engineers officer who has made Zone 1 his signature project, said Sunday that while he doesn’t question engineer Giorgio Tachiev’s reasoning, he’s not sold that it is a practical alternative.
The document, obtained through a public records request by the Independent, was commissioned by the Village Council to investigate an alternative to digging trenches, burying huge new pipes, and building pumping stations to move water off the land and into Biscayne Bay. Phase one of the project has an $80 million estimate, a price that has drawn increasing criticism and concern.
“It’s the time horizon,” Williamson said, saying GIT’s concept might not be as adaptable as the AECOM approach which can stretch to 2060. He asked if residents will want to pay for another round of stormwater upgrades a decade or two from now.
Williamson also said he’s not sure there will be a sufficient number of locations to site eight or more storage wells.
By contrast, Tachiev’s GIT suggests a different response to increasing rainfall and sea levels. It focuses on a less expensive, targeted system. It would use smaller pumps to move water into underground storage wells that would in turn use the existing set of drainage pipes to more slowly move the water into the Bay.
“A distributed system … provides a more flexible and cost-efficient means of routing stormwater from localized depressions, managing groundwater–surface-water interactions, and meeting water-quality requirements,” the report states.
The 95-page report stops short of a formal recommendation — that’s for a later phase. But it does discuss in intricate complexity — with charts and algebraic equations — the mechanism of how streets actually flood in major rain events. It stresses that rainwater just doesn’t fall — it moves in currents up, down, and crossways across island streets, and is pressured by tidal forces. These patterns and loops can reverse themselves during the day as tide levels change and create “micro-basins” that can be up to 3 feet deep.
“He’s looking at that significantly and how the tide variates with groundwater, which is not what AECOM was doing,” Vazquez said.
The way the village floods, the report argues, is grounds for rethinking the Big Dig’s centralized approach to reducing flood risk, wrote Tachiev, GIT’s principal officer. Tachiev, who was the engineer for the Village’s last set of stormwater projects, said that the current system designed by the AECOM firm may not be as effective as a spot approach.
“The presence of micro-basins underscores the need for localized interventions, such as distributed pump stations and drainage wells, which directly address sub-basin ponding characteristics and reduce reliance on long, flat conveyance pathways,” the report states.
Williamson said he expects that GIT will have a more detailed feasibility document by April, far into the planning for the 2027 Village budget. And he noted that the availability of state and federal funds is another factor to be considered, as Gov. Ron DeSantis and state GOP leaders consider major changes to the property tax system.
“That’s a risk,” Williamson said, especially if one of the more aggressive tax proposals is eventually adopted by Florida voters. “We may not be doing either one of them, depending on what decision Tallahassee makes, and so I certainly hope saner heads prevail.”
This story was originally published in the Key Biscayne Independent, a WLRN News partner.
