With Lake Okeechobee now topping 15 feet and still rising from Tropical Storm Isaac, federal engineers decided Tuesday to begin slowly draining the lake, opening gates that will send polluted waters down rivers on both coasts but ease pressure on its aging dike.
The move, which in the past has triggered foul fish-killing algae blooms in the sensitive estuaries of the Caloosahatchee River on the West Coast and the St. Lucie River on the East Coast, will begin on both sides of the lake at 7 a.m. Wednesday.
Lt. Col. Thomas Greco of the U.S. Army Corps of Engineers said the agency would try to minimize environmental impacts by starting with small volumes rather than the torrents of runoff laced with agricultural chemicals and nutrients that devastated both rivers after the hectic 2004 and 2005 hurricane seasons. The dumping also can raise salinity levels in estuaries, which can harm sea grass, oysters and other marine life.
“We’re actually releasing much less than what is authorized under the Lake Okeechobee regulation schedule,’’ said Greco, the Corps’ deputy commander for South Florida.
Under the Corps plan, the lake level is supposed to stay between 12.5 feet and 15.5 feet above sea level, rising and falling with rainfall. The goal is to balance the big lake’s often conflicting uses as a flood control basin, regional water reservoir and world-renowned fishing destination.
In the dry winter, it serves as a major source of water for surrounding sugar, citrus, sod and vegetable growers. In the wet summer, it handles runoff from hurricanes and storms like Isaac, which quickly filled a lake that had previously been running below normal. The lake has risen nearly three feet in the last month.
Greco said the lake’s massive dike, which is being beefed up with construction projects, is in good shape. Though the aging earthen levee has leaked during past storms, Greco said Isaac caused no problems and Corps studies suggest it would be safe with water levels up to 18 feet.
But because the lake is so near the 15.5-foot ceiling, there is little room left if another tropical system hits. The lake can rise much faster than the Corps can lower it. A foot of rain over the Kissimmee River basin to the north can boost lake levels as much as four feet in weeks, Greco said. It can take the Corps 75 days to drop it to that level again, barring other storms.
“Really what we’re looking at is preparing ourselves and make sure the conditions are right through the hurricane season,” he said.