Norwich — A plan by Norwich Public Utilities to build a new 2.5-million-gallon water tank on Park Center Road in Mohegan Park was approved Tuesday after a brief public hearing by the Commission on the City Plan.

The new ground-based tank, half the size and 35 feet taller than the existing 45-year-old, 5-million-gallon tank on the same property.

The new tank, costing $2.5 million, is expected to be built in fall and be online next spring.

NPU officials said the smaller, taller tank will allow better circulation and use of the stored water. Water should be “turned over” into the system two to three times per day.

Because of its size and the low height of the existing tank, the 5 million gallons essentially sits unused unless NPU officials manually draw down the system, NPU water system manager Mark Decker said.

Water in the old tank will be used and not replenished until it is nearly empty and then drained. The tank will be demolished and the new tank built on the existing footprint.

A security fence and electronic security surveillance are planned. With surrounding tall trees, the new tank will not be visible beyond the immediate area, said project engineer Peter Calderazzo of Dewberry Engineers Inc.

“Unless you're standing in front of the tank, you're really not going to get a sense of the tank being there,” Calderazzo said.