Water Quality

Water Quality Report 2026

• Each year the City of Gresham provides the Drinking Water Quality Report to all of its customers.
• The report contains important information about Gresham’s drinking water and water system.
• The 2026 Drinking Water Quality Report contains results from the 2025 calendar year.
• Request a paper copy or translation of the report by calling 503-618-2525.

Outstanding Performer Award 2025

Gresham received an Oregon Health Authority award for excellence in treating, storing and delivering drinking water. We are committed to providing safe, high-quality water to the community.

Gresham’s drinking water comes from three sources. Gresham switched from Bull Run water as a primary source of water to Cascade Groundwater. Gresham will use Bull Run and Columbia South Shore water as back-up sources.

Cascade groundwater

The Cascade Groundwater Alliance (CGA) expanded the groundwater system to increase water supply, storage and treatment. The Cascade well field, managed by Rockwood PUD and the City, taps into the Sand and Gravel Aquifer.

Cascade groundwater meets all state and federal treatment and water quality standards. About groundwater:

• Cascade groundwater comes from a deep, naturally protected Sand and Gravel Aquifer.
• Groundwater contains more naturally occurring minerals, including magnesium, calcium and silica. 
• These minerals make the groundwater moderately hard (58-108 m/GL).

For information about Cascade Groundwater water quality, visit Rockwood PUD. 

Bull Run Watershed

Located in a protected area of the Mt. Hood National Forest, managed by the Portland Water Bureau. Learn more about Bull Run.

Visit the Portland Water Bureau to learn more about Portland's water testing and water quality report. 

Columbia South Shore Well Field

Columbia South Shore, managed by Portland Water Bureau, is used on occasion to supplement the Bull Run. Groundwater from these wells comes from three different aquifers:     

• Blue Lake Aquifer
• Troutdale Sandstone Aquifer
• Sand and Gravel Aquifer

Keep our groundwater safe

Join the City in protecting groundwater, our secondary source of drinking water. Groundwater is runoff from rain or other precipitation that soaks into soil, filling cracks in beds or rock deep underground, called aquifers.

The deep aquifers that are the primary sources of water supply have natural geologic protection from pollutants present at the land surface. Portland, Gresham, and Fairview work together to protect the well field.

How you can help

• Take care when storing or disposing household chemicals. Never pour them down a storm drain. 
• Know if your older home has an underground heating oil tank. Check underground storage tanks for leaks.
• Report chemical spills and illegal dumping.
• Businesses have specific requirements for storing and using chemicals and is managed by the Groundwater Protection Program.