Tampa Bay's Desal Dogfight

The Southwest Florida Water Management District needed new sources that were cost-effective, drought-proof and environmentally acceptable. In 1997, the District had identified reverse osmosis (RO) seawater desalination as the best alternative. Technological advances had made desal more cost effective, and various techniques had been proven in water-scarce regions like the Middle East. With an $85 million commitment in District co-funding, the plant was expected to produce the cheapest (at $2.49 per thousand gallons) desalinated sea water in the world, supplying ten percent of the region's water needs.

The plant was to be located south of Tampa, near Apollo Beach. A second plant was scheduled for construction later, near Tarpon Springs. Environmental impacts had to be assessed prior to permitting. How the first plant might affect Tampa Bay would depend in part on "flush rate." A University of South Florida authority concluded the bay has a flush rate of 8 to 10 days. Earlier studies had shown that it takes at least 10 times longer. Incredibly, there's still no consensus on how long it takes Tampa Bay's estimated 924 billion gallons to enter and exit.

Both Gannon/Bayside and Big Bend are in a heavily industrialized sector of Tampa Bay known as Hillsborough Bay. Fed by two rivers, you'd expect Hillsborough Bay to teem with rod-bending gamefish. But decades of dredging and pollution have hit it hard. A mapping study in 1979 revealed less than one acre of seagrass in all of Hillsborough Bay, a net loss, since 1950, of roughly 2,700 acres. Thanks mainly to improved water quality there's now about 200 acres. Local guides say the fishing has improved.

The site chosen for the Tampa Bay Desalination Plant was an empty field adjacent to Big Bend. It seemed a logical choice: Power available for the desal process, and existing canals for water supply and discharge.

To cool its coal-fired generators, Big Bend extracts 1.4 billion gallons of sea water from Tampa Bay every day. As warm sea water left the power station, the desal plant would siphon off 44 million gallons per day. Modern seawater desal plants achieve about 60 percent efficiency; for every 44 gallons the Tampa Bay plant took in, it would produce 25 gallons of drinking water, and 19 gallons of effluent water. The effluent, now twice as salty as before, would be blended back into the discharge from the power station and flow out into Hillsborough Bay.

Construction began in 2001. Public reaction was like the water in the discharge canals-lukewarm. Local anglers and fishing guides suspected Tampa Bay Water had swapped one environmental nightmare-wellfield overpumping-for another. If the salinity was altered in Hillsborough Bay it was bound to hurt fishing. Many gamefish frequent low salinity wetlands at different points in their lives. Juvenile snook congregate in estuaries, where they feed on small freshwater minnows like mosquito fish. Big Bend is near the mouth of the Alafia River. Salinity in that sector of the bay is low, ranging from roughly 16 to 26 ppt. According to Capt. Doug Metko, of the Florida Guides Association, "Juvenile fish are going to be affected by this, to what degree we're not sure." Even a small change in salinity could disrupt the entire food chain.

When plans for the plant were finalized in 1999, concerned citizens organized to fight it, forming SOBAC, or Save Our Bays, Air and Canals. SOBAC volunteers weren't opposed to seawater desal, but they were adamantly opposed to the plant's location at Big Bend. They believed it should be built on the Gulf of Mexico, and the salty effluent piped to sea. Although SOBAC's lawsuit failed, the questions it raised will keep the attention of scientists and government agencies focused on the bay for years to come.

The Tampa Bay plant was scheduled to go on line in 2003. Problems with pretreatment filters surfaced almost immediately, forcing the plant to miss performance deadlines in January, March and June. Design firm Covanta blamed Asian green mussels for fouling its RO filters, an excuse later debunked. When it missed its final deadline in September, 2003, Tampa Bay Water declared Covanta in default of its contract. Covanta responded by declaring bankruptcy.

Construction of the Tarpon Springs facility was postponed, probably for many years, possibly for good.

So how long will it take to put things right? About 20 months, according to Kenneth Herd, the plant's Engineering & Projects Manager. Three companies have qualified to fix the failed pretreatment process.

Tampa Bay Water has vowed to spend $1 million per year monitoring the plant's environmental impact. Ongoing baywide monitoring will also be conducted by a number of state and federal agencies.

I asked Herd what Tampa Bay Water would do if monitoring revealed that it was harming the bay.

He responded without hesitation: "We'd shut it down."

FS