Fighting Off Flooding in the Florida Keys

BY Lindsey Ranayhossaini, Staff Writer

The Florida Keys have always been prone to flooding. The islands are a limestone archipelago, and the porous foundation, coupled with a low ground elevation, make the area extremely vulnerable to sea level rise and king tides.

But in 2015, what used to be referred to as “nuisance flooding” took a catastrophic shift when the usual double high tides were exacerbated by an offshore storm that pushed additional water from Florida Bay inshore. Each year, periods of flooding stretch longer and longer, and when the rains come, the water has nowhere to go on roads without a stormwater management system.

“It’s clear to us that it’s not a nuisance anymore,” said Rhonda Haag, chief resilience officer for Monroe County. “I don’t call it that anymore because it’s a slap in the face for the people who have a foot-and-a-half of water on the road. It’s a public problem.” Facing projections of up to 12 inches of sea level rise by 2040, Monroe County began work in 2015 on pilot studies in two communities – Twin Lakes in Key Largo and the Big Pine Key community of Sand. The studies assessed the 20-year tidal record to determine a target roadway elevation and necessary drainage improvements.

The Roadway Vulnerability Study

Furthering its pilot studies, Monroe County undertook a three-year analysis of its 311 miles of county roads. The purpose of the larger study, completed by HDR, WSP, and Erin L Deady, P.A., was to predict the amounts of water that the county could anticipate in the next 25 years, determine which roadways were most vulnerable to flooding from sea level rise and king tides, and estimate the cost of adapting those roads to manage the water.

When the study began, engineers treated all roadways with equal importance, collecting large amounts of data to inform which roadways most urgently needed adaptations and which could be repaired at a later time. The team relied on GIS data for a cost-effective alternative to visiting each of the 1,500 sites that would need to be evaluated.

“A lot of the resources and investment of time at the beginning went to collecting that data,” said Emilio Corrales, PE, project manager for HDR, Inc. “We had to make sure that we had the survey data on all the roadways so that when we started analyzing them we could analyze them equally.”

The team completed a two-step process to score each roadway’s structural integrity and vulnerability. In this first step of the process, roads were evaluated based on factors including surface inundation, groundwater elevation, storm surges, pavement conditions and a wind wave analysis.

The second step of the process required the team to evaluate each roadway’s criticality, assessing the human factors like density of homes and access to critical services. Roadways were given scores for each of the two steps, and the roadways that scored highest were deemed to be the most vulnerable to flooding.

What resulted from the study, which ended in 2023, was a plan offering conceptual designs for modifying 150 miles of roadway with an estimated total cost of $2.5 billion. Currently, $300 million worth of road adaptation projects are underway in varying phases of development.

Construction Challenges

Construction began in August on the Twin Lakes pilot project, with the Big Pine Key project in the bidding phase.

“Both of the projects have the same level of infrastructure to be implemented,” said Greg Corning, PE, senior civil engineer for WSP. “We’re raising the roadways to alleviate some of the sea level rise flooding through a stormwater system that didn’t exist previously. We're adding new pipes and new inlets along the roadways to capture that.”

The stormwater is routed through a pumped injection system that pushes the water approximately 120 feet below ground. With this new system in place, the county will be prepared for design rainfall events, as well as king tide events in the October timeframe.

During construction, the biggest challenge for engineers has been the implementation process, Corning said.

“We’re implementing these pilot projects in line with a lower level of elevation for these roadways that are in residential communities,” Corning said. “When you think about raising a roadway an extra foot above what the pilot projects are currently, that needs to be extended further out into those private properties. Obviously, some of the biggest challenges are easements for potential right-ofway acquisition for implementing the projects to allow for the roadway to be harmonized, basically connected, to those private properties.”

Engineers must also determine how to provide continued access to neighborhoods during construction, as well as implementing the projects within an existing utilities infrastructure. Some utilities must be relocated, and other utilities like power may want to move systems underground.

“We have to account for a new stormwater pipe in the ground; water, wastewater and now power wants to go underground,” Corning said.

“It’s just a challenge in terms of making sure that all that coordination is happening in the early design concepts that we’re working on right now, but also as we move into construction, ensuring that all those partners are part of the conversation moving forward.”

Funding Challenges

Implementation has not been the only area that has proven difficult in moving these roadway projects forward. Funding gaps have also created obstacles for Monroe County.

“The Big Pine project has been designed for several years already,” Haag said. “The original construction estimate was $7 million, $8 million at the most. We bid it out a couple years ago and it came in at $21 million, three times the original estimate. We thought that maybe there was some kind of error, so we rebid it. It came in even a little bit higher.”

For Twin Lakes, the original project estimate came in between $9 and $10 million, but the actual cost is $23.3 million, Haag said. Monroe County applied for state and federal funds based on original construction estimates and received a Resilient Florida grant for $3.9 million and a federal grant for $5.4 million through an appropriation.

“That was what added up to our original construction estimate, but lo and behold, when we bid it out it came to $24 million, so the county has now had to put in $13 million of our local funds,” Haag said.

“We can’t afford that for all of these road elevation projects. We did it for this because it was a pilot project and we needed to get it funded and under construction so that we can learn from it. But funding is going to be our biggest obstacle moving forward with the resilience program in Monroe County.”

The reasons for the discrepancies between the original construction estimates were rising material costs, as well as the challenges of working in a more remote environment like the Keys.

“As you move into more remote areas like the Florida Keys, it is more challenging to move equipment and materials down into the area,” Corning said. “It’s kind of hard to put your finger exactly on where this [high cost] comes from, in terms of whether it’s inflation or whether it’s just a way of doing business in the Keys.”

With large hurricanes hitting the west coast of Florida in recent years, many contractors have also concentrated their operations there.

The Future

“We’re going to be raising our estimates from here on out so that they can be more accurate, so when we’re applying for these grant funds we can be more accurate in the funds that we’re applying for so we’re not stuck with these shortfalls,” Haag said. “That said, we’re never going to be able to fund our projects with grant funds only. There’s going to have to be some contribution of local dollars or resident dollars to keep this program moving forward.”

Though roadway improvement projects promise to alleviate many of the Florida Keys’ flooding challenges, Monroe County needs an integrated concept for resilience, one that includes other factors like home elevation and managed retreat, Haag said. Engineering solutions are important, but so are policy solutions.

Still, Haag acknowledged that “the roads are probably the biggest piece of it.”

“Engineering is a big deal for the road elevation program,” Haag said. “Without that, we wouldn't be anywhere in the Keys – we wouldn't be resilient at all.”