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Reservoir's Flaws Costly To Repair

Tribune photo by JIM REED

Tampa Bay Water recently repaired these cracks in the C.W. Bill Young Regional Reservoir. The agency has spent $250,000 to fill the cracks with grout and plans to spend $1.million on equipment to monitor the earthen walls for several years to come. Engineers want to determine what is causing the cracks.

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By MIKE SALINERO, The Tampa Tribune

Published: December 9, 2007

Updated: 12/09/2007 12:17 am

LITHIA - Initially downplayed by Tampa Bay Water officials, the huge cracks in the walls of the C.W. Bill Young Regional Reservoir have turned into an expensive problem.

Questions about why the cracks opened and whether it could happen again remain unanswered a year after they were detected. Who will pay for the fix is also up in the air.

To date, the agency has spent $250,000 to fill the cracks with grout and plans to spend $1 million on equipment to monitor the earthen walls for several years to come.

"We want to make sure there isn't any dirt leaving the embankment and seeping out," said Tampa Bay Water's chief engineer, Jonathan Kennedy.

Engineers for the utility, which provides wholesale water to public utilities in Hillsborough, Pinellas and Pasco counties, and to Tampa, St. Petersburg and New Port Richey, say it's critical to determine the cause of the cracking so a lasting fix can be made.

They also want to know whether the cracks resulted from substandard work by the contractor that built the reservoir, Barnard Construction Co. of Bozeman, Mont.

"We can keep track of our costs and whether the cause is something that should have been prevented, and that will be part of the bill we will seek reimbursement for," Kennedy said.

Though Tampa Bay Water staff members discovered the cracks in December, the public didn't become aware of the problem until after a News Channel 8 report in August. Some of the utility's board members also said they were not told about them.

Engineers Labeled Cracks As 'Severe'

At that time, engineers with the utility and HDR of Omaha, Neb., the company that designed the reservoir, said the cracks in the walls were anticipated and reassured the public that the embankments were strong.

In the days that followed, state engineers who inspected the cracks called them "severe."

Records show Barnard was awarded an $86.37 million contract to build the reservoir in 2002 and that it was the lowest bid by about $8 million.

The soil-cement mixture used to cover the reservoir's earthen walls was made by mixing 8 percent to 9 percent cement with soils excavated during construction. Because the soil-cement does not contain gravel, its strength under compression is about one-tenth of typical concrete.

Tampa Bay Water chose the soil-cement mixture because it was less expensive than chunked rock called riprap, a common bank stabilizer.

Work was finished and the reservoir filled with water in 2005. It began supplementing the fresh water supply to Tampa Bay Water customers the next year. At capacity, the reservoir can hold 15 billion gallons, but is now at about 11 billion gallons because of 19 months of below-normal rainfall.

During Florida's typical wet-dry seasonal cycle, the reservoir drains throughout the winter and spring, then refills during summer and fall. The latest weather forecasts, however, are calling for a drier-than-normal winter and spring.

Tampa Bay Water engineers say they successfully stabilized the cracks they know about with the grout. More cracks could be lurking below the present water line, but engineers won't know until the reservoir drains.

"We sent divers down to put the lower instrumentation along the bank," Kennedy said. "The water is murky; it's too difficult for us to draw any conclusions from it."

Reservoir Is Under Warranty

One possible theory for the cracking - sinkhole activity - was ruled out by David Carrier, an engineer who studied the cracking for the Florida Department of Environmental Protection.

He said it's possible that pressure pushing out from the embankment cracked the soil-cement covering as the water level in the reservoir dropped. He added, however, that the rate of drawdown had not exceeded what the walls were designed to handle.

The reservoir is under warranty for defective workmanship. If serious flaws in the reservoir embankment are found to be the cause of the cracking, Barnard would be asked to pay repair costs.

In order to show defective construction, Tampa Bay Water engineers may have to monitor the embankments through several drain-and-fill cycles to see the effect of changing water pressures, Kennedy said.

Engineers will put in the final monitoring devices after the water reaches its low point in the spring.

Reporter Mike Salinero can be reached at (813) 259-8303 or msalinero@tampatrib.com.

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