Dam Pump Rehabilitation

CHARLES RIVER DAM PUMP REHABILITATION

In 1910, the state of Massachusetts built a dam on the Charles River to prevent tidal flooding of lowlands, sewers, and drains along the lower reach of the Charles River. In 1978, a project was awarded for building a new $61.3 million dam, which is located 2,250 feet below the old Charles River Dam, and is managed and maintained by the MA Department of Conservation and Recreation. Since the new dam was constructed nearly 45 years ago now, parts of the structure have recently begun to show signs of aging and deterioration. When dealing with aging infrastructure, preservation is typically the goal for structures that hold a piece of history, such as this dam.

The turbine pump suction bell is a vital piece of the dam’s moving parts. Vertical turbine pumps consist of a motor, discharge head, and at least one rotating impeller attached to a shaft that directs water into a diffuser casing known as a bowl. Water enters the pump through a bell-shaped component known as the suction bell. This dam’s turbine suction bell showed obvious signs of wear as the metal started to corrode and heavy seaweed and barnacle growth attached.

Fortunately, contractor Savy & Sons was able to provide a rehabilitation solution that presented significant cost savings and minimal downtime. Being the job site was 40″ below water level,  Savy & Sons started the project in the winter months. Working closely with the customer to coordinate all logistics on the project, they had to get creative with how the equipment was staged, and the order of operations were performed due to the location and limited working space. Savy & Sons constructed a full containment around the upper and lower portions of the bell to isolate all work from the surrounding areas and installed a dehumidification and heating unit in the work zone to control the climate of the working area during the winter months. Custom-built scaffolding was placed on top of the veins inside the suction bell/pump to allow access to the inside, and a small man lift was dropped into the bell’s vault by a crane to allow access to the exterior for the repair work.

Savy & Sons began the rehabilitation process by using a vapor blasting unit to remove all rust, scale, and existing tar coating from the interior and exterior of the pump. To safely remove and contain the waste, a vacuum truck and hose were used to remove all debris and media from the work zone in accordance with local and federal environmental laws.

Following that, they worked on restoring the metal loss by filling all pitting with a Belzona Super Metal product and applying a zinc-rich primer and two coats of Belzona 5811, a two-part epoxy coating that provides outstanding chemical resistance and protects equipment operating in aqueous systems from the effects of corrosion. Finally, after the coating had dried, Savy & Sons, in collaboration with an inspector, performed various dry film thickness and holiday testing for quality assurance, and the turbine pump suction bell rehabilitation was completed.