The City of Mandan was faced with a failing 75 year old, 1 million gallon steel ground storage reservoir originally built on the Collins Avenue storage site. The reservoir was originally built near main street and established residential and commercial areas. In 2007, the reservoir experienced several leaks and the City was mandated by the North Dakota Department of Health to repair the tank. After performing minor repairs to no avail, the City quickly realized the precarious situation the aged tank posed for a dramatic failure.
Mandan procured AE2S to expedite a new reservoir to include site, operation, and connection to the existing system. Through a previous completed model, a preferred site was located on the south side of the City - in a location to solve multiple issues including service to growth areas, pressure and fire flow issues, and redundancy to the south side of town. AE2S fast tracked a system that included a compartmentalized 4 million gallon reservoir, a two mile 20-inch transmission pipe, and a 16-inch tie back water main. The reservoir as finished is a “tank within a tank” consisting of a 1.5 million gallon cast-in-place tank inside a 2.5 million gallon pre-stressed ground storage reservoir. The different size tanks allow the City incremental storage capacity to minimize water age issues and allow capacity fluctuations from seasonal service and expected city growth. The two compartments were also designed and installed to create a baffle configuration to prevent short circuiting in the circular tanks.
With the successful completion of this project, the City now has the potential tank failure issue behind them and a new highly operation-friendly concrete reservoir.