Cascade Groundwater Alliance

CGA is delivering groundwater with a new treatment system. You may notice a few changes to your water. These changes are normal, and your water remains safe to drink.

Water treatment changes

Surface water from Bull Run is treated with chloramine (a mix of chlorine and ammonia). When we switch to our new groundwater treatment system, we will use free chlorine treatment

Free chlorine is a common and effective method to treat water. Free Chlorine prevents germs while water travels through pipes to your tap.

What you may notice

A slight chlorine taste or smell at first. This should fade over time as the system adjusts.

Water quality

• Your drinking water meets or exceeds all state and federal safety standards.
• We regularly test the water to protect public health.
• You can compare your water quality before and after the groundwater transition in the CGA water quality chart. 

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.

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

Cost savings

• Portland’s new Bull Run treatment plant is estimated to cost $2.6 billion, impacting future rates.  
• Expanding our existing groundwater system was less expensive than the projected costs to rate payers with Portland's upgrade.
• Using our local groundwater source helps keep water rates more stable.

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.