New Water Source Supplies McNeil Island

March 22, 2023

By Emily Boone (email) Communications Office

After seven years of planning, drilling and testing, McNeil Island has a new water source. Recently, staff from the Department of Corrections (DOC), Department of Health (DOH), Department of Social and Health Services (DSHS) and KPFF Consulting Engineers gathered for a ribbon-cutting ceremony at the new well pump and treatment site.

The previous potable water system supplying McNeil Island came from Butterworth Reservoir, a manmade lake held back by a dam that was built in the 1940s. This system required manually turning the treatment system on and off daily to produce clean water. When the Department of Ecology determined the dam was possibly unstable, work began to plan a new water system for the island.

An evaluation was conducted, and a new groundwater source was developed through the means of a well. Drilling for the well began in January 2018. A test well was drilled to 740 feet and pump tests and water quality tests were conducted and determined that it had enough capacity to support the new system.

After the well was drilled, design and approvals were obtained through DOH to use the new groundwater source, and a treatment system was designed and approved by DOH to treat for secondary contaminants.

“This is a public health operation that has come to fruition,” said Derek Pell, Regional Manager for Drinking Water at DOH.

The system capacity is 250 gallons per minute and the existing 1-million-gallon reservoir tank built in 2004 is still operational and adequate to run the entire island. Unlike the previous manually operated system, the new system is fully automated with a backup generator for the well pumps and treatment building, as well as the existing fire pump building.

“This new system is leaps and bounds above what’s been on the island for 80 years,” said Clint Pierpoint of KPFF Consulting Engineers. “It should be a great resource for years to come.”