By JOHN HOWELL Intuition and a phone call appear to have saved taxpayers millions of dollars while ensuring residents have a dependable reservoir of water for the next 20 years if not longer. After inspection of the city's two water tanks in May with a
Intuition and a phone call appear to have saved taxpayers millions of dollars while ensuring residents have a dependable reservoir of water for the next 20 years if not longer.
After inspection of the city’s two water tanks in May with a total storage capacity of 12 million gallons revealed cracks, the city acted quickly to close the worst of the two tanks. Stantec, the engineering and consulting firm the Water Division uses, was called in. After analyzing conditions and the inspect report, it was recommended the concrete tanks built in 1971 be replaced with two 4 million-gallon steel tanks at a projected cost of $10 million.
That made sense to Terry DiPetrillo, director of the Water Division, who looked at photos of the tank after draining and saw what he believed were exposed sections of rebar used in construction. It appeared the integrity of the tank was compromised and the concrete was failing.
Yet, he wasn’t sure. “It just wasn’t right with us.” DiPetrillo said of the replacement plan.
“I wasn’t happy with just one report.”
He contacted DN Tanks, formerly Natgun of Wakefield, Massachusetts, that built the tanks. His first surprise was that rebar wasn’t used in the tanks. The company explained that like building a wooden barrel, panels of the tank were poured on site and then raised to be interlocked. Steel bans were then wrapped every half-inch around the exterior to strengthen the structure.
DiPetrillo said representatives from DN Tanks inspected the drained tank, determining what the earlier inspection turned up was “superficial cracking.” Nonetheless, bringing the tank back online was not recommended without taking corrective action.
DiPetrillo said the plan is to inject the cracks with a waterproof composite and then spray coat the interior of the tanks with elastomeric that will protect the concrete and provide some flexibility to account for any ground vibrations or movement.
In its inspection report received this week DN Tanks writes, “ Only minor concrete deterioration was observed along these cracks and there is no reinforcing steel present in the wall slots. It is our opinion that the presence of these cracks is not a structural concern.”
The report says “that overall, the tank is in good condition and has many years of service life remaining.” DN concludes the tank can be returned to service but recommends rehabilitation “to improve the overall operation and extend the life.”
The report estimates the tank “will continue to operate without future remedial work for a period of 20 years or more.”
The two Bald Hill Road tanks are the main source of pressure for the city’s system. A 102-inch aqueduct feeds the tanks from Providence Water Supply with a connecting line in Natick. The tanks also serve as a supply to the Kent County Water Authority, which buys the water that Warwick has bought from Providence at wholesale. Warwick also buys water from Kent County, which in addition to buying Providence water has its own wells, to provide service to Potowomut.
As for the cost of repairs and relining the two tanks, DiPetrillo said DN estimated $1.8 million. He said the division is preparing specifications to seek bids for the work that he hopes to complete within a year.
A portion of the cost of repairs would be shared by the Kent County Water Authority under an agreement to be worked between the two authorities.
“Whatever it (the total cost) is, it’s better than $10 million,” he said.
And going forward, he concludes, “the main infrastructure (of the water system) is sound. You have to maintain it.”