Watertown 3 Million Gallon Reservoir Replacement

The Watertown Municipal Utilities (WMU) utilizes a 3 million gallon water storage reservoir, located at the Water Treatment Plant, for both water storage, and as a contact basin to achieve proper contact time (CT) for disinfection. The reservoir was constructed of steel, which experienced degradation and short-circuiting of the water flow that affected the CT and caused areas of the reservoir to have stagnant water. HR Green was retained to design and oversee the construction of a new wire-wound, prestressed, concrete reservoir with a steel diaphragm. The Watertown reservoir replacement design included:

1. Demolition of the steel reservoir and replacement with a 3 million gallon wire-wound, prestressed, concrete reservoir meeting the requirements of AWWA D110, Type III reservoir.
2. Evaluation of method to provide a plug flow through the reservoir to achieve required CT for disinfection and to eliminate areas of stagnant water within the reservoir.
3. Evaluation sizing and orientation of the reservoir to provide 3 million gallons of storage capacity while constraining the reservoir into an area limited in size by close proximity to a booster pump station, existing water main, the main entrance road for the Water Treatment Plant, and extents of the property line. The Watertown reservoir replacement height was also restricted to provide the reservoir on grade with a 4-ft berm while not exceeding height requirements of the nearby Watertown Regional Airport.