Other Projects at West Parish: Transmission and Raw Water Conveyance Improvements

While work continues on the new treatment plant, some other critical projects are also underway at West Parish Filters. This article focuses on the largest of those, the 42-inch Transmission Main Energy Dissipation Valve and Raw Water Conveyance Improvement Project (or “42”” for short).

A complete energy dissipating valve assembly

The project includes the repair of a two-mile segment of the 42” raw water transmission main that conveys water from Cobble Mountain Reservoir, and its associated energy dissipation valve (EDV). This pipeline segment was damaged in 2019 when a valve failed, interrupting one of the main routes that carries raw water from the reservoir to West Parish Filters.

This picture shows that the “EDV” is actually three valves in parallel. One of them, the axial control valve, is shown here being lowered into the structure.

An EDV is designed to reduce the high pressure created by water traveling downhill from the reservoir to the plant, preventing water hammers, vibration, and other stresses on the infrastructure.

Construction of the EDV facility adjacent to the Sedimentation Basin, which holds raw water prior to entering the plant (West Parish Filters is in the upper left distance).

Roof slab reinforcement installation

The project is now nearing completion, with the pipeline expected to return to service in spring 2026. Reactivating this pipeline will restore a redundant path for raw water to both the existing and the new treatment plant, providing operational flexibility and allowing the Commission to perform proactive maintenance more easily.