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Pumping Won't Bleed Wellfields Dry

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By NEIL JOHNSON | The Tampa Tribune

Published: March 28, 2009

Full-tilt pumping at wellfields in Pasco and Hillsborough counties will lower nearby lake levels and affect wetlands but likely won't bring a return to environmental damage seen before 2003, when the region's water supply relied solely on groundwater.

The lowered water levels will be a temporary setback to recovery around wellfields that started when Tampa Bay Water stopped siphoning 240 million gallons a day from the aquifer in 2003, said Michael Hancock, senior professional engineer for the Southwest Florida Water Management District.

"It should be a delay in progress rather than going back to any historic situation," he said.

A drought going into its third year has strangled river flows and cut the amount of surface water that formed part of the region's supply. That has forced Tampa Bay Water — which supplies Hillsborough, Pasco, Pinellas, Tampa, St. Petersburg and New Port Richey — to lean on wellfields.

This month, the utility had to shut down its depleted reservoir, meaning nearly all of the more than 200 million gallons of water used daily by customers in Hillsborough, Pinellas and Pasco must come from underground.

Meanwhile, mechanical problems will keep Tampa Bay Water's desalination plant limping at about two-thirds of its capacity until repairs are finished in April. Even at full throttle, the desalination plant can provide only about 10 percent of the region's water.

Until rains begin in June, the utility expects to take about 170 million gallons a day from 11 wellfields in northwest Hillsborough and south Pasco. The rest will come from desalination and wells scattered across central and southern Hillsborough.

When water is pumped from underground, its effects can be seen on the surface when lakes and swamps around the wellfields begin to dry.

During the last drought, the effects of pumping spread beyond the wellfields, so severely draining swamps that cypress trees toppled. Lakes went dry, and soil subsidence sent cracks through the walls of houses.

At the time, Tampa Bay Water was extracting an average of 240 million gallons a day from the wellfields.

"We're not predicted to pump near that much," said Alison Adams, senior manager for Tampa Bay Water.

"The last drought there were three years of continuous high pumping," she said. "There's a big difference now in the volume and duration."

After the last drought, Tampa Bay Water developed a plan to shift wellfield pumping among locations expected to cause the least environmental damage, said Hancock, the Swiftmud engineer.

Also since 2003, when the regional utility started using river water, the water management district known as Swiftmud has cut how much Tampa Bay Water could take from the wellfields, from 160 million gallons a day to 90 million gallons at the end of 2008.

That, Hancock said, has given swamps and lakes years to recover.

"Still, it's not a good situation," he said. "It's not where we want to be. Hopefully, all this is more of a short-term situation."

Reporter Neil Johnson can be reached at (813) 259-7731.

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