HHD Rehabilitation project improves community safety

the invisible $2 billion dam safety project improving the safety of those living near Lake Okeechobee

Jacksonville District, U.S. Army Corps of Engineers
Published July 28, 2021
Updated: July 28, 2021
Contractors work to build a cutoff wall deep in the Herbert Hoover Dike, improving the safety of the people who live and work near Lake Okeechobee.

Contractors work to build a cutoff wall deep in the Herbert Hoover Dike, improving the safety of the people who live and work near Lake Okeechobee.

It’s the prettiest wall you will never see.

That’s because the beauty of the cutoff wall shoring up the Herbert Hoover Dike around Lake Okeechobee isn’t in its physical appearance. The beauty lies instead in how the wall hidden inside the 143-mile earthen dam can improve the lives of those living in South Florida.

The original dike began its life in 1915 when local residents made a pile along the shore of the lake consisting of dredged gravel, rock, limestone, sand and shells. The materials and methods had nothing in common with how a modern dam would be constructed. The dike allowed too much water to move through it, washing away material it as it traveled through the earthen dam.

“All earthen dams have water that flows through and underneath them – that’s what we call seepage,” said Tim Willadsen, project manager for the HHD rehabilitation project in the Programs and Project Management Division of the U.S. Army Corps of Engineers, Jacksonville District.

“With HHD, especially in the south, that water has specific paths that it flows through that potentially can pick up material and carry it,” Willadsen said. “Once you carry material out of the internal workings of a dam or its foundation, that’s when you are subject to collapse and catastrophic failure.”

It was that type of failure that led to the loss of thousands of lives during hurricanes in 1926 and 1928 when water overtopped the dam and flooded local communities. USACE was tasked with construction of a more robust levee around portions of the lake, and a 1947 hurricane led to Congressional authorization to build what was eventually the Herbert Hoover Dike visitors see today. Completed in the 1960s, the earthen dam still faced problems with seepage.

That’s where the invisible cutoff wall makes its appearance, or rather doesn’t make an appearance as it hides in plain sight.  To ensure water doesn’t take portions of the dike material with it, a wall is being built below grade to force that water to go deeper into the ground and slow it down enough that it can’t carry parts of the dike with it as it flows.

Since 2007, locals have watched as massive cranes and cutter heads have slowly crept along the top of the dike, but few have actually seen the results up close, because the wall is being constructed inside the dike. Reaching 60 feet deep in some locations, the wall is unseen by the thousands of people who walk or bike on the newly replaced Lake Okeechobee scenic trail that circles the lake atop the dike. Most have little idea that they are right on top of a $2 billion dam safety project that makes living around the lake safer.

Now, with the cutoff wall nearing its completion date of 2022, Floridians are beginning to find out what benefits that infrastructure investment is buying.

“The risk to the dike during high lake stages was one reason we changed the operating schedule for the lake in 2008,” said Tim Gysan, project manager for the Lake Okeechobee System Operating Manual project. “With dam safety addressed by the completion of the dike rehabilitation work, we have more flexibility in how we manage the lake, which can have huge benefits for stakeholders who live in South Florida.”

The HHD rehabilitation seems to be proving the adage that beauty is in the eye of the beholder. The LOSOM team is rewriting the manual for managing Lake Okeechobee with the enhanced flexibility a rehabilitated HHD provides, and the benefits from that revised manual will appear differently to stakeholders in different areas.

Those living in the shadow of HHD will enjoy less risk of disasters like the 1926 and 1928 hurricanes because the dike is stronger and more resilient. Every alternative reviewed so far scores well in performance measures related to dam safety.

Those who rely on the water in the lake – city utilities and agriculture, but also Everglades National Park and Florida Bay  – will see more water available in every alternative reviewed to date.

With the preliminary preferred alternative selected, the Caloosahatchee and St. Lucie Estuary communities will both benefit from a reduction in the highest volume flows under the current schedule, and the Caloosahatchee will see an increase in the optimal flows needed for salinity control during the dry season.

“We aren’t anywhere near to being done, but as we move into optimization, we believe we have a really good starting point from which to work,” Gysan said. “We will continue to focus on improving the preferred alternative through the fall of 2021, and be ready to go through the formal NEPA process and complete the project in time to use the new operations manual when the HHD rehab work is finished in 2022.”

Gysan cautioned that completing the HHD rehab and writing a new manual isn’t the final solution to all of the water management concerns stakeholders face.

“The flexibility of a rehabilitated dike is great, and there are definite benefits to be enjoyed with a new operating manual, but this isn’t a silver bullet for all the region’s concerns about lake management,” he said. “We still have limitations that can only be addressed by completing new infrastructure, including components of the Comprehensive Everglades Restoration Plan. But we do believe that when the HHD is done in 2022, this new operating manual is going to provide benefits to everyone and perform much better than our current regulation schedule can.”

To see the latest or learn how to join upcoming LOSOM meetings, visit the Jacksonville District website at https://www.saj.usace.army.mil/LOSOM/.