HILLSBOROUGH COUNTY, FL -
Tampa Bay Water's regional reservoir is just shy of 8 years old and heavy machinery is now ripping apart its inner walls to begin the process of repairing and preventing widespread cracking.
In February, Kiewit Infrastructure Group's hydraulic hammers began the enormous task of breaking up the soil cement lining the 5 miles of the Bill Young Regional Reservoir's interior walls.
Large excavators continue ripping up the soil cement, dozers push it down the dam's steep banks and enormous dump trucks haul it off.
"It's a lot of work," Tampa Bay Water's engineering support manager, Jonathan Kennedy said.
The fix, as it is called, requires gutting the interior walls, removing the soil cement, the dirt below it, called the soil wedge, and a PVC geomembrane that lines the walls preventing seepage.
"In many ways this is like disassembling a layer cake and there's a lot of work to get down to the core before they can start the reconstruction," Kennedy said.
The reconstruction begins with Kiewit installing a drainage system. A new geomembrane which is being made in Spain, will be added, along with a new soil wedge and thicker, stronger soil cement.
"It's as though you had a car engine with a leaking gasket and the gasket itself is a relatively minor repair but you have to disassemble the engine in order to get to it," Kennedy added.
The work will keep the reservoir, which supplies roughly half of the drinking water for the Tampa bay community, off line at least until the end of the summer of 2014. The reservoir renovation will cost water customers in Hillsborough, Pinellas and Pasco counties $129 million dollars.
An 8 On Your Side investigation revealed in 2007 widespread cracking of the reservoir's soil cement. Video shot from Eagle 8 showed crews attempting repairs by pumping a cement-grout mixture into the cracking soil cement. Some of the cracks were 300 feet long.
At the time Tampa Bay Water project manager Amanda Rice indicated the repairs were nothing out of the ordinary.
"This is a route maintenance. Activity like this is conducted at all Tampa Bay Water facilities," Rice said.
The cracking turned out to be anything but routine. It spread and became worse. Gaps several inches wide and hundreds of feet long continued forming.
Repairs did not hold.
A portion of the soil cement lining the south wall collapsed. Tampa Bay Water insists the cracking never threatened the integrity of the reservoir's walls but did limit its ability to hold water.
At full capacity the reservoir holds 15.5 billion gallons of water.
Tampa Bay Water spent millions on repairs, investigating the cause and legal bills.
It determined the cracking was caused by water that became trapped in the soil wedge. During draw downs, water pressure would build up behind the soil cement and crack it.
The agency sued designer HDR Inc in federal court in 2012, claiming the company's reservoir design was flawed. A jury disagreed, saddling Tampa Bay Water with the cost of repairs.
"It's a $129 million dollar project which translates into a little over a dollar a month on the average bill," Kennedy said.
Kiewit is ramping up construction at the reservoir. It plans to have about 150 workers on site, working two shifts.
In order to increase efficiency, different stages of work will be going on in several areas of the facility.
Kennedy says Tampa Bay Water is shooting to put the reservoir back into partial service by the end of the summer of 2014.
"In order to do that (Kiewit's) going to be finishing the project from the bottom up so that we can get permission to put some water in the lower reaches while it finishes the construction of the upper reaches," he said.
Kennedy hopes to put about 8 billion gallons of water in the reservoir at that time, which would supply up to 90 million gallons of water a day to customers.
"The existing facility does not have a drain in its system, that was left out of the design, and by putting the drain into this design, we know that this project will be successful when it's complete," Kennedy said.
