Town of St. John, IN
St. John, the second fastest growing community in Indiana, enlisted the help of Robinson Engineering, LTD. to solve the problem of low water pressure in the Town’s water system. After evaluating the situation and considering various alternatives, the decision was made to raise the overflow elevation of two existing elevated tanks by 35’ in order to increase water pressure by approximately 15 psi within the Town. Raising the existing elevated tanks would eliminate the need for new booster stations, pressure-reducing valves, and all future operation and maintenance costs.
This complexity and magnitude of raising elevated tanks from 105 to 140 feet required the use of multiple cranes rated up to 500-ton capacity. The project was so notable that it was featured as an article in the December 26, 2005, issue of Construction Digest.
The first tank raised was on October 1, 2005, completed in less than 13 hours. The weather had to be perfect to raise the 425,000-pound sphere and riser. The contractor prepared the elevated tank by installing lifting lugs, rigging and partially cutting the riser pipe. The morning of the lift, the contractor pre-stressed the cranes to approximately 120% the lifting weight. After the cranes passed the lifting test, the riser pipe was cut and the water sphere was lifted 65 feet into the air. The contractor used three 300-ton lattice cranes to lift the sphere. A smaller all terrain crane moved in place to install the 35’ long, 91,000 pound riser. When the riser was fitted into place, the contractor welded the lower section of the riser to the upper section of the cone. After the riser was secured to the cone the sphere was lowered to the upper section of the riser for final welding.
The second tank that was raised was a 500,000-gallon Hack Street elevated tank. Because the tank was a multi-legged tank, the contractor chose to pick up the entire tank and legs. After the tank was raised approximately 40’ the contractor installed 35’ leg extensions to each of the six legs. The weight of the tank that was raised was approximately 250,000 pounds. The lifting was accommodated by two mobile 500-ton hydraulic cranes. The site was very tight because of the large trees surrounding the tank area. When the tank and legs were in the air, a smaller more mobile 210-ton crane lifted the 35’ leg extensions to be bolted into place and set on the existing foundations. The tank was lifted on October 26, 2005, in approximately 10 hours.