Despite Lake Okeechobee dumping, dike danger continues to rise
08/07/2013 7:51 PM
08/08/2013 11:22 AM
Lake Okeechobee keeps rising — and so do worries about an aging dike the U.S. Army Corps of Engineers ranks among the most vulnerable to failure in the country.
With the massive lake swollen by a more than a month of heavy rain, the Corps cranked the flood gates open to “maximum” two weeks ago. That move infuriated residents on both coasts, coursing billions of gallons of foul nutrient-laced runoff down two rivers, but it also managed to at least slow the rate of rise.
So far, however, it hasn’t been nearly enough to reverse a troubling climb. Even with South Florida dodging the wettest remnants of Tropical Storm Dorian last week, daily storms continue to slowly push water levels up and put pressure on the 143-mile-long Herbert Hoover Dike.
The Corps held a news conference Wednesday to insist federal engineers are doing everything they can to minimize environmental impacts while protecting public safety but cautioned that nature, particularly the tropics, may play the biggest role in whether the lake will reach the dike’s danger zone over the next few months.
“We still have several months left in the wet season. We still have not reached the peak of the hurricane season,’’ said Lt. Col. Tom Greco, the Corps’ deputy district commander for South Florida. “We’re taking that very seriously.’’
Lake water levels were set to top 16 feet sometime Wednesday. That’s just six inches short of a mark that triggers the Corps to move from weekly to daily inspections of a massive but nearly 80-year-old mound built out of sand, shell, rock and peat. Despite some $300 million-plus in on-going repairs, sections remain highly vulnerable to high water and storm damage, weakened over the decades by internal erosion.
At current rates, Greco said, the lake will hit 16.5 feet in about two weeks. Unless the lake slows, projections show a 50-50 chance it could top 18 feet in coming months, which would significantly raise the risk of a potentially disastrous breach.
Emergency managers and leaders in Pahokee, Belle Glade and a string of other small towns in the shadow of the dike are monitoring water levels daily and consulting with the Corps and the South Florida Water Management District, which runs the regional flood control system.
“We’re starting to get nervous,’’ said Palm Beach County Administrator Robert Weisman. “It’s added a whole new level of risk in that area. You can’t drain water of the lake quickly enough if there is a substantial rainfall.”
The lake, which doubles as a flood control and water supply reservoir for the sugar industry, has risen 1.27 feet over the last 30 days. In the past, hurricane and tropical storms have raised lake levels twice as fast and experts are forecasting an active next few months.
Since 2006, when an alarming report by state engineering consultants pronounced the dike “a grave and imminent danger,” the Corps has shored up the dike’s most vulnerable stretch from Port Mayaca to Belle Glade with a cement-like internal dam engineers call a “curtain wall.” The agency also is overhauling or planning to beef up half of the lake’s 32 drainage culverts, considered high-risk spots.
The Corps adopted a new scheme to protect the levee by keeping a lake that doubles as a flood control and water supply reservoir at lower levels, aiming to have it rise and fall seasonally from 12.5 feet to 15.5 feet.
At its current level, the Corps considers the risk of a breach minimal and Greco said that surveys showed no significant increases in seepage. But, with the lake more than two feet above its historic average for this time of year and more than three feet above where the Corps wants it, risks will only rise through hurricane season.
According to a 2000 Corps study, the risks of a dike failure rise significantly at 17 feet. At 18 feet, the probability is 45 percent. At 20, a breach somewhere along the dike is likely, with damaging and potentially deadly flooding. Those probabilities didn’t take into account the most recent repairs, but even with those, the Corps still rates the dike among a handful of the most high-risk in the nation.
The lake has topped 18 feet a handful of times in the past. It peaked at 18.8 feet in 1995, an event that opened serious leaks at nine spots along the south and southeast shorelines, and again topped 18 feet after a string of hurricanes in 2004. In 2005, Hurricane Wilma chewed a chunk from the dike near the Pahokee airport. The Corps cited an old repair job that failed and said the dike was not at risk of a breach.
With or without storms, the Corps expects to continue dumping water down the St. Lucie and Caloosahatchee Rivers for the foreseeable future.
The surge of polluted water, high in phosphorus and other agricultural chemicals, has added to local runoff that has fouled waters on both coasts, angering residents, tourists, environmentalists and local political leaders. Besides killing oysters and sea grass, the dumping has triggered a toxic algae bloom in the St. Lucie River and warnings from health authorities to stay out of the water.
State agencies on Wednesday released a joint statement saying that state and local governments had already spent more than a half-billion dollars to reduce pollution impacts from local runoff and were looking for solutions to address “complex environmental and public health issues’’ that balanced flood control, water quality and water supply needs
Greco said the Corps was working with water managers and state agencies for potential solutions, including putting more water into already brimming Everglades water conservation areas, but public safety concerns about the dike have forced dumping “that isn’t popular but is necessary.”
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