In 2005, the City of Cookeville, Tennessee, hired CTI Engineers, Inc. (CTI) to develop a long-term master plan for expansion of the City’s existing 15-MGD water treatment plant. The resultant study examined both conventional and membrane filtration alternatives. A water consumption demand of 22.5 MGD was determined as the needed capacity for the year 2025, and cost estimates were prepared for facilities sized to meet that demand.

Implementation of the water treatment plant expansion to 22.5 MGD will be accomplished in phases. The first phase began in late 2006 when Cookeville entered into a design contract with CTI for expansion of the existing raw water intake.

The existing raw water intake is on Center Hill Lake, a 23,060-acre lake of the U.S. Army Corps of Engineers built in 1948. The existing intake included two 3.75-MGD vertical turbine pumps and two 7.5-MGD vertical turbine pumps, for a firm capacity of 15.0 MGD. Unfortunately, because of piping restrictions, wear and tear, and low lake elevations, the output from the intake was limited to approximately 14.5 MGD, thus reducing the potential potable water output from the existing water treatment plant, which was only 85 percent efficient.

The expanded raw water intake provides a firm capacity of 22.5 MGD, even at the lowest lake levels. To provide that capacity, a new traveling water screen with fiberglass mesh baskets was installed along with four new vertical turbine pumps, each rated at 7.5-MGD.

Pump control was accomplished with electric-actuated check valves and VFDs. The entire raw water intake is monitored and controlled through a supervisory control and data acquisition (SCADA) system connected by fiberoptic cable to the water treatment plant control room.

To obtain the most economical electrical equipment while providing the capability for emergency operation utilizing a portable stand-by generator, the entire incoming electrical service was replaced, changing from 2,300 volts to 480 volts. A new electrical building was constructed adjacent to the existing pump building to house the new switchgear, transfer switch, and variable frequency drives for each of the four pumps.
The chemical feed facilities were doubled in size to provide facilities for feeding hydrogen peroxide, gaseous chlorine, and/or potassium permanganate.

W&O Construction Company of Livingston, Tennessee, completed the project within 20 days of project schedule at a cost of $3,373,979.

The expanded facility was placed into full service in early March 2009. Along with a recovery membrane facility completed in July 2008, the new facilities allow the existing Cookeville water treatment plant to produce as much as 17 MGD. This provides the city with “breathing room” as far as plant capacity is concerned while they plan future implementation of high-service pump replacement, to be followed by expansion of the treatment and filtration components of the existing water treatment plant.