The board of Tampa Bay Water has approved staff recommendations for an estimated $125-million repair program for the agency’s four-year-old, 15.5-billion-gallon C.W. “Bill” Young Regional Reservoir. The facility, which cost roughly $140 million to construct originally, has been experiencing significant cracking since late 2006. At the same time, the authority is moving ahead with a lawsuit against the three lead members of the project’s design and construction team: HDR of Omaha, Neb., the designer; Barnard Construction Co. of Bozeman, Mont., the contractor; and construction manager Construction Dynamics Group of Columbia, Md.
In late 2006, the agency discovered significant cracking along the reservoir’s interior lining. Tampa Bay Water reports that cracking has been found along roughly 40% of the reservoir’s interior lining. The problem areas were located in the soil-cement lining of the interior walls, which had been designed as an alternative erosion-control component of the reservoir.
The reservoir’s erosion-control layer consists of a layer of soil-cement that lines the structure’s interior, along with a soil wedge that lies between the soil-cement layer and geomembrane that protects the reservoir’s embankment. Last summer, Black & Veatch of Overland Park, Kan., started an investigation of the cracking problem. The firm found that water is becoming trapped in the soil wedge.
“The crux of the problem is the buildup of core pressures in that soil wedge,” says Jon Kennedy, manager of engineering and projects for Tampa Bay Water. “The water gets underneath the interior liner, and it’s trapped in between the soil-cement and the geomembrane cutoff wall. It’s putting tremendous pressure on that liner when we draw that reservoir down in the springtime.”
HDR added the soil wedge to its design upon the urging of the Florida Dept. of Environmental Protection. Agency officials have focused much of their public comments on HDR’s role in the project. However, Kennedy says, “Tampa Bay Water is looking not only at the design flaw but also those who constructed the facility and those who provided the construction inspection.”
The agency is considering three different approaches for repairs: adding drains to the soil wedge and replacing the soil-cement layer; adding weight to the existing structure to prevent further movement of the soil-cement layer and soil wedge; and removing the existing soil wedge and reapplying a well-drained, soil-cement, erosion-control layer directly on top of the geomembrane.
Kennedy says the $125-million cost figure is “an average of a number of different repair scenarios,” and is the figure the agency is including within its Fiscal Year 2010 budget.
Tampa Bay Water expects the repairs to start in 2012, and to last roughly two years. The reservoir will be empty during that period.
“In order to select the best solution for the best value, Tampa Bay Water will have a competitive design and construction process that will include an independent, expert peer-review group as part of the process,” Gerald Seeber, general manager of Tampa Bay Water, said in a press statement.
A spokesperson for HDR would only state: "HDR is fully cooperating with Tampa Bay Water to find a resolution that is agreeable to all parties. We cannot comment further at this time since litigation is pending."
Barnard Construction was contacted for this story, but did not return calls for comment. The contractor is currently working on a $61.7-million contract for the Peace River Regional Reservoir in DeSoto County, Fla., for the Peace River/Manasota Regional Water Supply Authority in Bradenton. That project, whose engineer is MWH Americas of Broomfield, Colo., also features a soil-cement lining but includes a drain.
“This is a critical facility to our system,” Kennedy says. “It absolutely has to function the way it was always intended to function, and it’s good that the board supported staff’s input on that.”