Ground Water Wells

In addition to water sources in the Green River Watershed, Tacoma Water owns 24 wells in and around Tacoma. Our wells pump water from aquifers, which are underground layers of water, saturated sand and gravel that collect local rainfall.

The majority of the groundwater we use comes from wells in the South Tacoma wellfield, which are critical to our future drinking water supply. We began developing these wells in the early 1900s and now have 14 within this wellfield. They pump from productive aquifers that stretch from north of the Nalley Valley all the way to Lakewood. Our wells can pump about 55 million gallons per day, and are used during the summer months to help meet peak water demand.

Protecting Our Groundwater Supply

Groundwater typically supplies about 5% of Tacoma’s water in the summer and supplements the supply from the Green River at other times of the year. We sample drinking water wells for bacteria and for traces of more than 150 different metals and chemicals. We also sample numerous dedicated monitoring wells.

Thousands of homes and hundreds of businesses are located above the aquifer that supplies the South Tacoma wellfield. Because of this, we work to educate area residents and businesses about ways to prevent drinking water contamination. If a groundwater well is contaminated, we must either treat the water or replace the well so that enough water would continue to be available for customers. These are difficult and expensive options, and we take our prevention and outreach efforts seriously.