When completely full, Lake Fort Smith's normal elevation will be 86 feet higher than that of the old lake, and cover approximately 1400 acres. The reservoir combines old Lake Fort Smith and old Lake Shepherd Springs further upstream in the Frog Bayou watershed. Photo: James Holland
With the population of Fort Smith, Ark., expected to double to 300,000 over the next 40 years, utilities director Steve Parke had to find a way to provide the growing community with drinking water without affecting current supplies.
The solution: simultaneously conduct the engineering, geotechnical testing, environmental studies, permitting, property acquisition, financing, and construction necessary to raise the city's 70-year-old earthen dam by 101 feet, combining two lake reservoirs into one and ensuring an adequate water supply through 2050.
During the project, water quality had to remain constant and the existing reservoirs had to remain in service to supply drinking water. To meet these criteria, Parke opted to construct the project in two phases under two separate contracts, a challenging and somewhat risky decision. Burns & McDonnell, Kansas City, Mo., handled the engineering and design portion of the project. The same national contractor, Granite Construction Co., won both bids, but it just as easily could have bid out to two different companies, says Parke.
“We used two separate contracts to reduce delays, including weather delays,” says Parke. For example, Burns & Mc-Donnell identified features that would mitigate rainfall delays while raising the embankment, so those were built first.
After awarding the first contract, Parke had to hope that the second contract (bid one year later) would come in on budget. The second contract was not awarded until the first phase of construction was well under way, giving engineers the necessary information to improve the design the second phase of construction. Though the bidding environment can change drastically in one year, costs remained within budget.
Some items were designed and bid out, and while that was under way, the next phase of the next section was designed. This gave Burns & McDonnell additional time to complete field investigations for the second contract's design to prevent potential contractor claims regarding unforeseen subsurface conditions.
While Burns & McDonnell could perform several tasks simultaneously, such as engineering design that began before sub-surface testing was complete, plans had to change as new information became available. The firm just had to “go with the flow” when this happened, and update accordingly.
“This fast-track approach saved time in project delivery, but required design adjustments as more technical data became available,” says Russel Titus, PE, project manager with Burns & McDonnell.
The results were worth the risk. A project that normally would have taken eight to 10 years was completed in five years.
Project:Lake Fort Smith Dam and Reservoir Enlargement
AEC firm: Burns & McDonnell
Cost: $180 million
Project delivery method: Design-bid-build
Date completed: August 2006
Size: 190-foot dam embankment, 225-foot tall intake tower for raw water supply and flow diversion, 1300-foot tunnel with dual 48-inch water lines
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