Project Summary

This project constructed a new 42 million gallon per day water treatment plant for the City of Anacortes.  The new treatment facility treats water from the Skagit River and serves the 56,000 customers in the City of Anacortes, La Conner, nearby Whidbey Island, and two oil refineries on Fidalgo Island. 

The new facility aims to increase capacity, reliability and water quality with a new pretreatment facility, filter facility, pump stations, operations and control center, chemical facility, clear well, and electrical upgrades.

Construction occurred at the site of the existing treatment plant facility and included a new 2.1 million-gallon water storage tank. IMCO self-performed critical construction activities including piping tie-ins to the existing plant within very small working windows to limit the impact to the existing plant, temporary dewatering system capable of pumping 15 MGD, and pile driving 360 steel pipe piles, each 100-feet in length.  IMCO placed 14,000 cubic yards or structural concrete for tanks and buildings and installed all yard piping including 54-inch ductile iron and 48-inch welded steel pipe systems.  IMCO crews installed all mechanical process systems and piping, five 1,000-horse power high lift turbine pumps, generators for temporary power.  IMCO designed and installed the fuel system to run generators for seven consecutive days.



Mount Vernon, WA


City of Anacortes

Contract Amount

$56 Million


HDR Engineering, Inc.

Construction Manager

MWH Americas


March 2011 - May 2013