Hoyle Tanner has provided consulting engineering services to the Newfields Village Water & Sewer District for over 30 years. Newfield’s tank was 83’ high and 22’ in diameter for a total storage volume of 235,000 gallons of which only the top 20% was considered available due to minimum pressure considerations under normal demand conditions. Built in 1942 with welded steel construction, the tank was the only distribution storage tank in the system. NHDES required Newfields to develop an action plan for the tank which had exhibited pinhole leaks periodically and was in need of exterior recoating.
As a first step, Hoyle Tanner coordinated a detailed tank inspection performed by Utility Service Company. Hoyle Tanner worked with the District to implement a temporary operating system, based on hydraulic distribution system modeling, while the tank was drained and out of service leaving the system temporarily without distribution storage.
The inspection confirmed that the tank not only needed new interior and exterior coatings but that structural repairs would be needed to fix extensive pitting and corrosion to restore lost tank wall thickness. The Newfields tank exterior coating was also found to contain lead.
Using this information, Hoyle Tanner prepared a CAP (Capital Action Plan) for the Newfields tank evaluating three options:
1 Repair and recoat the tank following the inspection recommendations;
2 Replace the existing tank at its current location;
3 Replace the existing tank at an alternative location owned by the District.
Option 1, rehabilitation, was found to be more expensive than replacement (and the rehabilitated tank would still be 70 years old). A location analysis was performed using Hoyle Tanner’s distribution system hydraulic model of the Newfields system. Although moving the tank to the Option 3 location would result in a lower, wider, less expensive tank, fire flow capacity in the town center would be reduced without extensive piping upgrades. Replacement of the existing water storage tank at the current location was recommended as the lowest-cost solution. The new tank would include a mixing system to improve water quality. NHDES quickly approved the CAP and outside funding was secured for the proposed new tank fencing.
After considering different tank types and costs, the replacement tank was bid using a glass-fused, bolted steel design. After the new tank was placed in service, the old tank was demolished, and site work was completed. The final tank construction cost including existing tank demolition was $549,900.
- Capital Action Plan
- Tank Inspection Coordination
- Bidding Assistance
- Construction Administration
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