TAMPA — As Tampa Bay Water prepares to spend millions to fix its cracking reservoir in eastern Hillsborough County, the question remains: How does it know this fix will work, and that it's not just throwing good money after bad?
Early estimates put the repair costs at $125 million. The 15 billion-gallon above-ground reservoir, the first of its kind in Florida, cost $146 million to build.
Water officials say they'll pull together a team of experts from across the country to review plans for the repairs.
"We'll have many eyes looking at the job rather than just the engineers who work for Tampa Bay Water," said the utility's general manager, Gerald Seeber.
The panel will include reservoir owners and operators, regulators from other states, academics and representatives from the Army Corps of Engineers.
"None of our engineers are experts at this," said Jon Kennedy, Tampa Bay Water's senior manager of engineering and projects.
When the utility was building the reservoir, it relied solely on its designer, HDR Engineering, and the Florida Department of Environmental Protection, to guarantee the project would work.
Utility officials now think water built up in a layer of soil between an impermeable membrane in the reservoir's embankment and a layer of soil-cement that lines its basin, and this caused cracks in the soil cement.
Repairs might include removing the middle layer, installing a drainage system to relieve pressure behind the soil cement, weighing down the lining, or a combination of all three.
Kennedy said Tampa Bay Water hopes to learn from what happens at a 6 billion-gallon above-ground reservoir in DeSoto County managed by the Peace River Manasota Regional Water Supply Authority. That reservoir is set to begin operating next month.
Designed by MWH Americas, it has a drainage system to prevent water buildup, said Pat Lehman, executive director of the Peace River authority.
Engineers also made some adjustments to the soil cement lining after problems emerged at the reservoir in Hillsborough.
"A lot of things have been learned from the Tampa Bay experience," Lehman said.
The DEP has required the authority to closely monitor water accumulation behind the soil cement.
"By collecting that data, we will be able to monitor the effectiveness of that drained system and compare it to our system that's undrained," Kennedy said.
The utility opened the C.W. Bill Young Regional Reservoir in June 2005 as a place to store water skimmed from the Alafia River, Hillsborough River and Tampa Bypass Canal.
The cracks were discovered 18 months later.
The utility's board voted last year to sue HDR Engineering, which designed the reservoir; Barnard Construction Co., which built it; and Construction Dynamics Group, which oversaw the construction. The board also fired HDR from its job of filing monitoring reports on the reservoir. The federal case is set for trial in 2011.
Intended to hold 15 billion gallons of water and provide 25 percent of the region's drinking water, the reservoir will be closed for two years beginning in June 2012 while repairs are made.
Janet Zink can be reached at firstname.lastname@example.org or (813) 226-3401.