[Florida, US] Flood danger looms in state

Report points to problems with Okeechobee dike

WASHINGTON - Despite its great length and considerable girth, Florida's Herbert Hoover Dike surrounding Lake Okeechobee is the nation's next catastrophe in waiting.

A recent report by a small team of consultants cast significant doubt on the safety and stability of the 140-mile-long man-made barrier.

A closer examination of the 78-page document reveals a disturbing portrait of danger that is eerily reminiscent of the ''Hurricane Pam'' tabletop exercise organized by the Federal Emergency Management Agency that predicted the Hurricane Katrina disaster in New Orleans months before it happened, but was largely ignored.

''The condition of the dike has been deteriorating with time,'' said Leslie Bromwell, principal engineer for BCI Engineers and Scientists Inc. of Lakeland, who led the three-person technical review. ''During the last 10 years, many analyses had been made and reports written yet they didn't seem to be getting any significant attention. We became very concerned.''

The report was commissioned by the South Florida Water Management District, the government authority responsible for the elaborate plumbing system that provides water for six million people in 16 South Florida counties. Lake Okeechobee and its earthen dike is the heart of that system.

Time to take action
The report relied almost exclusively on the research and periodic reports of the U.S. Army Corps of Engineers, the agency that maintains the dike. However, corps officials criticized the consultants' work.

''I believe they used inflammatory language in that report that is irresponsible,'' said Col. Robert Carpenter, commander of the Jacksonville District of the U.S. Army Corps of Engineers, which oversees the agency's work in most of the state.

Some of the most alarming parts of the document were passages pulled directly from the pages of Army Corps of Engineers documents. For example, this sentence appeared in a 1998 corps report from a group described as a ''panel of eminent geotechnical specialists'':

''The panel considers the dike to be unsafe from a piping and erosion point of view and recommends that actions be taken without further delay.''

Carpenter did not dispute the accuracy of this or other excerpts contained in the consultants' report.

Release would flood towns
An uncontrolled release of water from the 730-square-mile lake would submerge vast areas of farmland and small towns around the lake where an estimated 40,000 people live. The flood could threaten the water supplies of the nearby urban corridors on both the Atlantic and Gulf coasts.

The basic problem with Herbert Hoover Dike is that it was built of porous materials like gravel, rock, limestone, sand and shell. The construction, which began in the 1930s, followed the accepted standards of the time for a temporary levee.

Unlike a hardened concrete dam, the earthen berm and its underlying foundation are vulnerable to erosion and seepage.

Years of rising and falling lake levels, storm surges and extreme drought have left the interior of the dike looking like ''Swiss cheese,'' laced with interconnected voids and open channels, according to Bromwell's team.

When the lake level rises above 18.5 feet, pressure from the wall of water against the dike's slope forces water through to the opposite side in a dangerous process called ''piping.''

Passing hurricanes can force the water to slosh and break even higher up the lakeside berm.

Severe piping can cause the slope to collapse and ultimately lead to total breach of the dike wall.

Using U.S. Army Corps of Engineers reports, the consultants documented an alarming series of near failures mostly along the berm segments facing the densely-populated counties of Palm Beach and Broward.

Another dike segment, the one facing Fort Myers and Naples, is considered nearly as fragile and prone to failure, according to the Army Corps' own investigations.

Preventing major failures
Bromwell's report praised Army Corps of Engineers teams for intervening with 100-percent effectiveness to prevent a catastrophic failure of the levee wall. The report, however, criticized the corps' dependence on emergency repairs as a long-term solution to the dike's ongoing problems.

''This cannot go on indefinitely,'' the report observed. ''A subtle but real danger associated with such situations is that over time and repeated close saves, they can come to be accepted as the norm.''

This section of the Herbert Hoover Dike report echoed the troubling findings of two other national tragedies - the Challenger and Columbia shuttle disasters that killed 14 astronauts.

In both of those events, investigators later blamed NASA for discounting repeated equipment malfunctions because they had yet to produce a catastrophic failure. That's an unfair comparison, said the Army Corps' Carpenter.

''Unlike (the shuttle) example, we have recognized we have a piping problem and we're spending $300 million to repair the known shortcomings in the dike,'' Carpenter said.

The Corps has begun a major repair project to strengthen 50 miles of dike slope over the next seven years at a cost of approximately $300 million, Carpenter said.

FOR MORE INFORMATION
www.saj.usace.army.mil/pao/hotTopics/hhdike.htm, U.S. Army Corps of Engineers Herbert Hoover Dike information page.

www.sfwmd.gov, South Florida Water Management District. Look under What's New for the Herbert Hoover Dike information page.

www.srh.noaa.gov/mfl/newpage/Okeechobee.html, National Weather Service history of the deadly 1928 Lake Okeechobee flood.

'NEAR FAILURES' OF THE HERBERT HOOVER DIKE

1995: Late summer and fall, lake level above 18 feet, near failure in nine locations, requiring emergency repairs. Excessive seepage, piping transport of dike material, sinkholes, sand boils and deltas were observed.

1998: Lake level above 18 feet, U.S. Army Corps of Engineers responded quickly to 94 separate problem spots.

2003: In March, dike slope distress reported near South Bay at lake elevation of 15.3 feet. In July, a vertical crack on the dike crest was observed in same segment, the first record of such an event.

2004: Dike slope distress reported between Belle Glade to north of Canal Point.

2005: Dike slope distress reported near Pahokee Airport.Years of rising and falling lake levels, storm surges and extreme drought have left the interior of the dike looking like ''Swiss cheese,'' laced with interconnected voids and open channels, according to Bromwell's team

_______________________________

link:
http://www.tallahassee.com/apps/pbcs.dll/article?AID=/20060514/NEWS01/60...

(In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes.)