Water Treatment Plant Clearwell and Waterline


The City of Anacortes Public Works Department has contracted with IMCO Construction of Ferndale to construct a clearwell and raw waterline at the Water Treatment Plant alongside Skagit River in Mount Vernon. Both projects were designed by HDR Engineering.

Clearwell project:

Waterline project:

See more videos of the projects:


The water treatment plant has a design rated production capacity of 42 million gallons per day. The final step in treatment before pumping the finished water to distribution is chlorine contacting in a tank (commonly referred to as a clearwell).

WTP 2.1-million-gallon clearwell

Existing Clearwell

The new clearwell will be located east of the plant’s old sedimentation basin and will operate in parallel with the existing 2.1-million-gallon clearwell at the plant. It will have the same hydraulic elevations and a 2-million-gallon capacity. The second clearwell will provide for redundancy and greater reliability of treatment operations.

Second clearwell position

As part of the project, both the new and existing clearwells will have internal baffling installed to provide for adequate chlorine contacting efficiency and performance.

Baffling system

Raw Waterline

The raw waterline will run parallel to an existing 42-inch pipe coming from the plant’s intake station on the west side of Skagit River to the plant on the east side.

Raw water line

Intake Station

intake pic

2007 waterline installation

Pipe going into the ground 9-22-07

Like the existing pipe installed in 2007, the new line will be placed under the river using horizontal directional drilling. The new line will provide a redundancy of raw water supply and greater resiliency of its water supply system.