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Environmental Services

Water Quality

Providing customers with safe, reliable, and affordable drinking water, now and in the future.

Expanded groundwater system

This spring, Gresham will deliver groundwater as its main water source. The Cascade Groundwater Alliance (CGA) expanded the groundwater system to increase water supply, storage and treatment. 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). To learn more about water hardness, visit the US Geological Survey (USGS).

The switch to groundwater

While we switch from surface water (City of Portland Bull Run water supply) to groundwater, your water is still safe to drink. You may notice a few small changes:

  • Groundwater has more natural minerals which may effect the appearance of the water.
  • You may experience a slight change in smell and taste as the City switches water disinfection methods.

Customer experience

During and after the switch to groundwater you may experience:

  • You may notice a small change in taste and smell of the water. 
  • Soap may not lather as well due to harder water.
  • There may be scale and spots on dishes after drying.
  • Possible film on shower doors.
  • Water Quality Report
  • Drinking Water Sources
  • Groundwater Safety
Water Quality Report

Water Quality Report 2025

  • 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 2025 Drinking Water Quality Report contains results from the 2024 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.

Drinking Water Sources

Gresham’s drinking water comes from three sources.

Spring 2026: 100% groundwater

  • Gresham will switch from Bull Run water as a primary source of water to Cascade Groundwater. 
  • Gresham will use Bull Run and Calumbia South Shore water as back-up sources.

Cascade Well Field

Cascade, managed by Rockwood PUD and the City, taps into the Sand and Gravel Aquifer. Currently, this groundwater is used to supplement our supply from the Portland Water Bureau. 
In 2020, the City and Rockwood Water People’s Utility District formed the Cascade Groundwater Alliance to expand Gresham’s groundwater system together. Cascade ground water will be the primary water source for Gresham in spring 2026. Learn more about the Cascade Groundwater Alliance.

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
Groundwater Safety

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