May 10, 2007
Seeping Seawater Threatens Florida’s Drinking Supply
With the drought elevating a perpetual problem into a critical concern, state water managers are poised today to impose severe new restrictions to combat a seeping front of sea water that threatens the water supply for hundreds of thousands of coastal residents.
All residents in Broward and Palm Beach counties would be ordered to slash lawn watering to once a week. Utilities in Hallandale Beach, Dania Beach, Lantana and Lake Worth could face shutting down wells where chloride readings, a red flag for salt water intrusion, have been rising for weeks.Water managers defend such unprecedented steps as necessary to avert more disruptive and expensive damage -- salt contamination of coastal well fields that could force some cities to abandon primary drinking wells or install new treatment systems. At least eight more well fields, from South Miami-Dade to Palm Beach, also are considered "at risk" if groundwater levels fall low enough to allow an underground wedge of sea water to push deeper inland.
'A HUGE CONCERN'
"The threat of salt water intrusion is a huge concern," said Jesus Rodriguez, spokesman for the South Florida Water Management District, which oversees the water supply for 16 counties.
The district's governing board will meet today in West Palm Beach to consider staff recommendations that would tighten what already rank as the toughest water-use restrictions in South Florida history.
While wildfires and wilted lawns, marshes and crops are the most visible effects of the 17-month long drought, salt intrusion looms as a major threat to the regional water supply -- already so low that drought effects could linger for years, even with a good rainy season.
If wells get too salty to supply water that meets state health standards, it could force cities to look for others sources and further strain a scare resource.
"Once that [salt] creeps in there, it could be years for the wells to be brought back on line," Rodriguez said. "The scenario is a grim one. We could be talking about bottled water for the municipalities for a long time."
The latest proposed cutbacks could prove costly for Broward and Palm Beach residents, particularly in four cities ordered to shut down major water supply wells.
In Dania Beach, public services director Dominic Orlando said the city still will be able to supply some 12,000 residents with water despite shutting down its two main wells just west of Ravenswood Road. But buying, blending and chemically treating water from Broward County and Hollywood will cost the city $100,000 more a month, an expense residents will see reflected in water bills.
"If we turn off our wells, just to break even we have to implement a surcharge of 60-plus percent," said Orlando. He argued that daily monitoring and a gradual decrease in pumping could protect the city's wells without punishing residents' pocketbooks.
"Just to tell us to shut down your system, geez, that's absurd," he said.
Under the proposal, Miami-Dade would remain on twice-weekly watering restrictions -- for now. Above average rainfall in the county has buoyed levels in the southern portions of the Biscayne Aquifer, South Florida's primary source of drinking water.
Still, the district considers a string of wells in South Miami-Dade, including ones that serve Florida City, the Florida Keys, Homestead and parts of the county, at potential risk because they're close to the salt water intrusion line. "Right now, we're sort of on alert and certainly needing to conserve as a hedge against what may or may not happen over the next couple of months," said Doug Yoder, assistant director of Miami-Dade's Water and Sewer Department.
WAITING FOR RAIN
Though Broward and eastern Palm Beach also tap the Biscayne Aquifer, conditions are much drier there, Rodriguez said. Rainfall, despite a promising start in May, has remained well below average for a year and a half and groundwater levels continue to drop -- with no help of replenishment until the rainy season kicks in.
Lake Okeechobee serves as the region's storage reservoir, but at 9.42 feet above sea level Wednesday, it is too low to help. Last month, the district also capped withdrawals from the Everglades water conservation areas west of the suburbs, though water managers have asked federal permission to override environmental regulations to do emergency recharges of well fields.
The problem is that plunging groundwater levels along the coast could weaken what hydrologists call the "head" that holds back, or more accurately, slows ocean waters that have been creeping underground for decades.
The heavier salt water tends to wedge under the fresh water, forcing it inland and shrinking the aquifer's coastal boundary.
So far, salt concentrations, measured in chloride readings, remain below state health standards at the at-risk wells. But water managers say cutting local demand is a key to keeping things that way. That's why they're ordering the four most vulnerable cities to shut down pumping, Rodriquez said. A well pulling millions of gallons of water out of the ground can create a so-called cone of influence that helps pull salt water inland.
"We don't want to find ourselves in a scenario in a few weeks down the road where we're having to face a much more critical situation," Rodriguez said.
Intrusion is not a new concern. Utilities have been battling it since the 1930s, when new drainage canals and well fields pulled salt water deep into the Miami River.
In 1946, salinity-control gates were installed and the salt water pushed back. But a "blob" still remains trapped underground near Miami Springs, said Scott Prinos, a supervisory hydrologist for the U.S. Geological Survey.
Over the years, engineers have learned to control the intrusion, but not stop it completely. The line has shifted in and out after droughts or heavy rains, but enough salt water has crept inland deep enough to turn a number of private and public wells brackish or too salty to use for drinking water.
The current intrusion line snakes six miles into deep Southeastern Miami-Dade, the result largely of drainage canals altering the flow of freshwater marshes. Though the line is thinner in Broward, a few miles at its widest, the risk is greater because more coastal wells were sunk near beachside cities.
Dania Beach, said Orlando, was already scouting locations for new wells farther inland. Drought concerns have expedited the search and upped investments in the water system. A contractor started drilling test wells Monday. The city also is constructing a huge new storage tank and a treatment plant that can handle more water from Broward.
He doesn't think there is any threat taps will run dry.
"The issue, I think, is that provided water is going to be a lot more expensive," said Orlando.
Miami Herald staff writer Jennifer Mooney Piedra contributed to this story.