Everyone has probably heard the old Dutch folk tale about a small boy who stuck his finger in a leaking dike to stop the flow of water, saving his town from being flooded.
The U.S. Army Corps of Engineers can only wish dike repair could be so simple. In September 2007, the Corps began a project to help prevent breaches in Lake Okeechobee’s aging 143-mi. (230 km) dike. The project has been divided into eight reaches or sections and the first phase of the rehabilitation work was completed in July. Scheduled completion date is 2030 and by the time it’s finished, the cost will be approximately $1 billion.
“What we’re doing is rehabilitating the dike, which is about 143 miles surrounding Lake Okeechobee up to the authorized level of protection,” said Mike Rogalski, a project manager for the Corps.
The rehabilitation plan includes building a cutoff wall through the middle of the earthen dike and adding a landslide feature, such as a seepage berm, around the outside to reinforce the structure and stop erosion.
Lake Okeechobee is the second largest freshwater lake in the country and the largest lake in Florida. It’s part of the Kissimmee-Okeechobee-Everglades system. Originally a saltwater lake, it was eventually replaced by fresh water from rainfall. Today, the lake provides drinking water for people living around it and is a backup water supply for 8 million people living along Florida’s lower east coast. It also serves as a source irrigation for a $1.5 billion-a-year agricultural industry that produces sugar cane, winter vegetables, citrus and rice.
The first embankments around the lake were built by locals in 1915.
Hurricane tides swamped the embankments in 1928, killing more than 2,800 people. The Corps began building the dike in the 1930s under the River and Harbor Act using hydraulic dredge and dragline techniques that concentrated deposits of pervious shell, rock and gravel within the dike. The hydraulic dredging methods used to construct the first levees were fully acceptable in the 1930s and ’40s; however, due to an improved understanding of material properties and seepage mechanisms, those same methods would not be acceptable today.
In 1948, Congress passed the Flood Control Act, authorizing the first phase of the Central and South Florida Project, a comprehensive plan to provide flood and storm damage reduction and other water control benefits in that part of the state.
“Originally, it was just built around the northern and southern shores of Lake Okeechobee,” Rogalski said. “In the 1950s the dike was continued around the entire lake and the project was completed in the early 1960s.”
After completion, the dike was named the Herbert Hoover Dike.
Rogalski said in the early 1990s, the Corps was asked to study the current condition of the dike and it was determined there was a need for some repair work in certain areas.
“In 2000, Congress approved the funds to go back and do some of these fixes,” Rogalski said. “What we’ve done is broken the Herbert Hoover Dike into eight reaches or segments where we do the rehabilitation. The first segment we’re working on is located on the southeastern shore. It’s about a 22-mi. length of reach that runs from the C44 canal— Port Mayaca — to Belle Blade.”
According to Rogalski, construction on the first reach included installing a cutoff wall within the crest of the dike. The cutoff wall is about 27 to 36 in. (69 to 91 cm) thick and runs 50 to 60 ft. (15 to 18 m) in depth depending on the location, which changes as they move along the dike.
In 2007, the Corps issued multiple award task orders, which allowed it to issue contracts. Three contractors — Odenton, Md.-based Hayward Baker Inc.; Bauer Foundation Corp., a German firm that has an office in Clearwater, Fla., and Treviicos South, an Italian company with an office in Boston.
The Corps sought the world’s foremost cutoff wall construction experts and awarded three performance-based contracts that do not dictate technique. Potentially, all three contractors can work simultaneously. Once awarded a task order, a contractor must construct a 500-ft. (152 m) demonstration panel to prove the technique and finished panel meets rigorous engineering standards. Engineers test the panel prior to, during and after construction. Corps contractor Hayward Baker successfully completed a panel near Port Mayaca in April, and finished constructing a 3,500-ft. (1,100 m) section of wall in August.
The Corps recently awarded a $28.9 million contract to Bauer Foundation for construction of a second wall, a 3.5-mi. (5.6 km) long wall that runs from the dike crest, through foundation, to a depth of about 70 ft. (21 m).
A third contract was awarded to Treviicos South. The base contract includes construction of a 500-ft. (152.4 m) demonstration section, with options for construction of four additional sections totaling 3.2 mi. (5.1 km) at a cost of $38.6 million.
“These companies have installed cutoff walls for various purposes throughout the world,” Rogalski said. “Each has a different type of technology to install the wall, but the way we have the contract, it’s based on performance specifications, which means they have to meet certain strength [and] permeability requirements that the Corps has established.”
Currently, Hayward Baker is putting the finishing touches on the first reach by restoring the crest of the dike to preconstruction conditions.
Jim Hussin, director of Hayward Baker, said to build the cutoff wall, the firm used technology it learned in Japan.
“We were the first contractor to perform that work,” Hussin said. “The way we constructed that wall was an innovative way in the U.S., using technology we brought over from Japan. We create the wall by mixing the soil in place with cement.”
Hussin said his crew operates a batch plant on site using a trench cutting and remixing deep (TRD) wall machine that mixes the cement mix. Once the cement is mixed, it uses a modified crawler crane, one of only two in the United States.
“Instead of a big boom on the front it has a large hydraulic motor that drives a vertical post that looks like a big chain saw,” Hussin said.
“There’s not a whole lot of these machines in the world. Most are in Japan.”
Rogalski said the machine digs down from the top of the dike and mixes cement with the foundation soil in a continuous trench.
“It looks like a hydraulic cutting and mixing arm,” Rogalski said. “It does the trench cutting like a big vertical chain saw.”
Other equipment on site includes much of the standard fare — trucks, a crane, bulldozers and backhoes.
Rogalski said the three contractors are doing most of the work, but it has hired subcontractors to do additional soil testing. On any given day, there might be 20 workers onsite, not including designers, geo-tech field workers and dam inspectors.
While this job has plenty of challenges, Rogalski said juggling four different phases at once tops his list.
“We’re installing the cutoff wall and we’re also doing design on the land side,” Rogalski said. “We’re building a berm and dealing with different methods of rehabilitation. Then there’s the environmental requirements.”
Hussin agreed coordinating all the phases and the environmental impacts provide daily hurdles, but just making sure the job is done right is his biggest challenge.
“The biggest thing is all the quality control the Corps has in place to make sure the wall is going to perform as specified,” Hussin said. “To test samples in the core we have to set up in the center of the wall and go down full depth in the center. The wall is not very wide but we have to make sure there’s a good quality core.”
While the cutoff wall portion of the project will have little construction impact on the surrounding community, the benefits will be substantial, making the area much safer during hurricanes and other storms that bring a lot of rain.
“Most of the work is on top of the Herbert Hoover Dike,” Rogalski said. “There’s a scenic trail around the top and there might be some disturbance there, but otherwise there won’t be much impact on the public. There might be some land acquisition outside the federal government’s footprint, but that’s about it.”
One thing that helped construction during the past year has been low lake levels, which were about 3 ft. (0.9 m) below normal. But what’s good for construction has caused an economic strain on businesses dependent on lake water.
In 2006, dike safety concerns prompted the Corps to lower the lake in anticipation of hurricane season. Instead of hurricanes, Florida had two years of below normal rainfall, leaving the lake at historic lows.
The Corps likes to keep the water level between 12.5 and 15.5 ft. (3.8 and 4.7 m) above sea level. Limited potential for dike failure can happen at 17.25 ft. (5.3 m). At 18.5 ft. (5.6 m), the Corps said there is a 55 percent probability the dike will breach.
For agricultural growers on the south side of the lake who use the water for irrigation, that raised some concerns. Along with the drought and the new water level, marinas, fishing guides and other tourist-related businesses found themselves struggling.
Channels through the lake that usually provide a route between Florida’s coasts have been too low for sailboats, barges and yachts that bring customers. Jim Sheehan, whose company operates the Pahokee city marina and campground, said if the water levels are going to remain low, those channels should be dredged to help restore boat traffic, an idea the Corps isn’t planning to address anytime soon, as it said droughts are extreme, but temporary, conditions.
Rogalski said it has done some minimal dirt moving as part of the berm construction.
“We’re on schedule according to what we’ve planned at this point,” Rogalski said. “It’s scheduled for completion in 2030, but that depends on rehabilitation of future reaches. It could be quicker.”
At this point, Rogalski said, the Corps has a fourth task order in the proposal stage and should award a new contract by the end of October. Hussin said his company wants to be part of that reach, too.
“We’ve got the next phase coming up for bid and we’ll submit a package,” Hussin said.
As Rogalski looks forward, the Corps will “continue awarding task orders, continue working on the cutoff wall, continue working on landscape design and look at future reaches.” CEG