CLEARWATER — Nearly two years after discovering long cracks in the wall of Tampa Bay Water's $146-million reservoir, and after spending $700,000 investigating the problem, engineers still don't know the cause.
Even when they do figure it out, repairing the problem might require keeping the reservoir less than half-full for several years.
The reservoir — the largest in Florida — is supposed to hold 15-billion gallons of water for use by customers in Pinellas, Pasco and Hillsborough counties. But for now it contains only 6.5-billion gallons, and it's likely to stay that way while the search for the cause of the cracks goes on — followed by any repairs.
"It could need to be in the interim mode for several years," engineer Jon Kennedy told the Tampa Bay Water board Monday. "We're in step one of four, which could take several years."
But Tampa Bay Water officials insisted repeatedly that the residents living around the reservoir in rural Hillsborough County shouldn't worry about a breach opening in the walls and flooding their homes.
"The reservoir is safe," said Tampa Bay Water Chairwoman Susan Latvala, a Pinellas County commissioner.
The regional utility opened the reservoir, named for U.S. Rep. C.W. Bill Young, in June 2005, as a place to store water skimmed from the Alafia River, Hillsborough River and Tampa Bypass Canal. Water demand during the 2007 drought drained the reservoir to just 2.4-billion gallons a year ago. Since then, though, the utility has been able to build the water level back up.
The reservoir's ability to save the region during such dire times made it stand out as a success for the wholesale utility, which for years was plagued with embarrassing problems with its dysfunctional 25-million-gallon-a-day desalination plant and, to a lesser extent, its 66-million-gallon- a-day surface-water treatment plant.
However, the cracks in the reservoir's walls have posed a new head-scratching mystery for the utility.
The walls consist of an earthen embankment as wide as a football field at its base, averaging about 50 feet high, with an impermeable membrane buried in the embankment to prevent leaks.
The cracks in the layer of the reservoir wall formed from a mixture of soil and cement were discovered in December 2006. An independent inspector hired by the state Department of Environmental Protection reported that the cracks were up to 400 feet long and up to 15 1/2 inches deep.
The cracks have occurred in the soil-cement on the inside surface of the reservoir wall, Kennedy told the board. Below that is a layer of soil 10 to 25 feet deep between the soil-cement layer and the impermeable membrane, then more soil in the embankment.
"Both us and the DEP agree that the reservoir is totally safe even if it's full," Kennedy said. However, to facilitate the search for why the walls cracked, Tampa Bay Water and the DEP have agreed to keep the reservoir only half-full.
Although the utility hired crews to fill in the cracks with a special type of grout, many of the cracks opened again in the spring, according to the utility's staff.
Testing appears to have ruled out sinkholes and other possible theories for the cause have not panned out, either.
While the search continues for the cause and cure of the cracks, several utility board members wanted to make sure that whoever might be responsible for the problem would be held accountable.
Their attorney, Richard Lottspeich, told them he couldn't tell them anything about that yet, explaining that "we're at a delicate time" in negotiations. Hillsborough County Commissioner Al Higginbotham told Lottspeich he planned to be on his back about making sure the utility didn't get stuck with shoddy workmanship, but he and other board members agreed to hold off pointing fingers.
"I'm not making any wild allegations of professional negligence yet," said New Port Richey Mayor Scott McPherson, one of the utility's board members.