Skip sidebar navigation
Environmental Services

Cascade Groundwater Alliance

In spring 2026, Gresham's primary water source switched to groundwater.

Safe, reliable, locally sourced water   

Gresham’s transition to a locally owned system provides safe, reliable drinking water while protecting customers from the higher long-term costs. We test the water regularly to ensure it meets all state and federal drinking water standards. 

If you have questions about your water, call 503-226-2525 or send us your comments using our online form.

Groundwater information 

About Our Groundwater

Where your water comes from

  • Groundwater comes from rain that soaks into the ground and is stored between layers of sand, gravel, and rock. These underground layers are called aquifers. 
  • Gresham’s water comes from the Sand and Gravel Aquifer, located about 600 to 1,400 feet below the ground.
  • The aquifer has thick underground layers, about 50 to 200 feet thick. Because the aquifer sits deep below the ground, it does not pose a risk of sinkholes.
  • This deep aquifer covers roughly 300 square miles (roughly the size of two Portlands).  
  • The Sand and Gravel Aquifer is the oldest and deepest aquifer in the Portland basin.

 A reliable, sustainable supply 

  • Rain and river water naturally replenish the aquifer. 
  • The water slowly moves underground from higher areas toward the Columbia River. Because the aquifer is made of sand and gravel, water can move and refill it over time.
  • Scientists have studied the Sand and Gravel aquifer for many years, confirming there is enough water to meet future water demand.
  • Water systems are carefully managed, so the aquifer can refill naturally.

Groundwater use

  • More than one million people in the Portland metro area rely on the Sand and Gravel Aquifer, including Fairview, Troutdale, and Wood Village.
  • Gresham has been delivering groundwater, especially during higher demand, in the summer months. 
Cost

Cost savings

Keeping water affordable was a central reason Gresham expanded our existing groundwater source. The City partnered with Rockwood People’s Utility District to share the cost of transitioning to a locally owned groundwater system. 

Portland’s new Bull Run treatment plant is estimated to cost $2.6 billion. Based on conservative estimates, continuing to purchase Bull Run water would have cost Gresham approximately $7.5 million more per year by 2030.

By comparison, expanding and operating our own groundwater system will save over 25% per year. Those savings will help keep water rates lower and more stable for Gresham residents. 

Rates

  • Water rates are not expected to go down with this switch to groundwater. Using groundwater provides more stability over time.
  • Council approved a five-year water utility rate package that started Jan. 1, 2023. The rate increases cover water, stormwater and wastewater service and help pay for expanding the groundwater system.
  • Water rates cover the full cost of providing safe drinking water, including building, operating, and maintaining the water system.  Learn more about Gresham utility rates.

Customer assistance

We are committed to helping customers who need support with their water bills. Assistance programs are available for qualifying households. Learn more about our utility financial assistance program.

Water Treatment

Groundwater has different natural characteristics and we use a different treatment process than Bull Run water. As a result, you may notice changes in how your water tastes, smells, or appears. These differences do not mean the water is unsafe. Gresham’s drinking water is regularly tested and meets all state and federal drinking water standards. 

Water treatment changes 

  •  Bull Run water is disinfected with a combination of chlorine and ammonia. Gresham’s groundwater is treated with only chlorine. The addition of ammonia is no longer necessary with our smaller groundwater system size.
  • Both types of disinfection maintain safe drinking water from the water treatment plant to your home.
  • Oregon drinking water rules require public water providers to regularly monitor disinfectant levels.  

What you may notice 

Gresham’s groundwater contains more naturally occurring minerals than Bull Run water. You may notice:

  • A chlorine taste or smell.
  • A different mineral taste.
  • White spots on dishes, glassware or fixtures.
  • Mineral buildup on faucets, showerheads or appliances over time.
  • Soap or shampoo may lather differently. 

These are common effects of differences in water treatment and mineral content and do not indicate that the water is unsafe.  

Water Hardness

What is water hardness?

Groundwater has more minerals like calcium and magnesium. This makes the water harder. Hard water is safe to drink, but you may notice:

  • Spots on dishes or glassware. 
  • Soap may not lather as much.
  • Possible build-up on fixtures over time.  

Water hardness is measured by grains per gallon (GPG). Hard water contains more mineral grains. Our groundwater is rated soft to moderately hard.

Groundwater questions

Do you have questions about the City's recently completed transition to local groundwater? Check out our Frequently Asked Questions page to find answers to the most commonly asked questions we've received or send a question to our water team.

  • Project Background
  • Project Funding
  • Resources
Project Background

Planning for the future

In 2020, City Council approved moving forward with the Cascade Groundwater project. This was a long-term decision to manage rate increases and provide a safe, reliable water supply for the future.

The Cascade Groundwater Alliance (CGA) is a partnership between the City and the Rockwood Water People’s Utility District.The Alliance was formed to share the cost of expanding our groundwater system. 

Work to expand our groundwater system

Groundwater wells

Nine wells will pump groundwater from Sand and Gravel Aquifer – over 600 feet below ground. To add water capacity, five new wells were drilled:

  • Cascade Well 6: 223rd Avenue
  • Cascade Well 7: 202nd and Glisan
  • Cascade Well 8: 141st Avenue
  • Cascade Well 9: Kirk Park
  • Cascade Well 10: North Gresham Elementary.

Water treatment

Three state-of-the-art treatment plants will ensure our water meets state and federal quality standards.

Gresham’s commitment to water quality was recognized in 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.

Water Pipeline

10 miles of larger diameter water pipe will carry water from wells to treatment plants to storage and delivery. 

Water storage

Three modern storage tanks will ensure there is enough water year-round and for emergencies.

Project Funding

Investing in our water system 

The Cascade Groundwater Alliance share the cost to build and operate the new groundwater system. Gresham invested about $70 million over five years to build wells, treatment plants, and pipelines that bring groundwater to your home. 

Federal funding support 

We are using low-cost federal funding to help lower costs for customers. This includes: 

  • A $34 million federal loan (WIFIA program) that helps reduce interest costs  
  • A $4.5 million forgivable loan to help pay for water treatment improvements  

These funding tools help reduce the overall cost of the project for customers. 

Resources

Documents 

Water quality

The City manages water quality programs to protect and monitor drinking water. 

State and Federal guidelines