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The City of Portland, Oregon

Portland Water Bureau

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Groundwater: Portland’s Buried Treasure

Many Portlanders are familiar with the Bull Run Watershed – Portland’s main water supply of fresh, clean water – tucked away in the protected wilderness of the Mt. Hood National Forest. But did you know that Portland also has a second supply of high-quality water?

The Columbia South Shore Well Field

The Columbia South Shore Well Field

The Columbia South Shore Well Field (CSSWF) is used as a secondary source to the Bull Run Watershed, during an annual maintenance operation, in the summer when the region’s demand increases or when the Bull Run cannot be used, such as in the winter when heavy rains can cause turbidity to rise in the Bull Run. Over the past 10 years, Portland has used anywhere from 0.01 to 5.8 billion gallons of groundwater annually.

The CSSWF is the second largest drinking water source in the State of Oregon, with about half of the daily capacity of Portland’s Bull Run supply. Currently, the Portland Water Bureau is serving one hundred percent groundwater.

Groundwater Water Quality

The groundwater from Portland’s production wells meets or exceeds all safe drinking water standards, so it’s treated similarly to the water from the Bull Run with chlorine, ammonia, and sodium hydroxide.

Groundwater quality is closely monitored at individual drinking water wells, and at the inlet and outlet of the Groundwater Pump Station. This is where groundwater blended from individual wells enters the distribution system.

How Much Groundwater Is There?

Colubmbia South Shore Well Field AquifersThe short answer is: a lot! The detailed answer is that the Columbia South Shore Well Field can sustainably produce about 80 million gallons of safe drinking water per day. The City holds water rights that would allow about another 200 million gallons per day of groundwater to be pumped for future municipal use.

Protecting the Groundwater Supply

Groundwater Protection Area"The Columbia South Shore Well Field is right here in town, so we all play a role in preserving this vital drinking water source,” says Doug Wise, Groundwater Protection Program Manager with the Water Bureau’s Resource Protection and Planning Group.

See below for several ways you can help protect our groundwater supply:

Learn more about how the Portland Water Bureau’s Groundwater Protection Program is working to keep the groundwater supply safe at

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