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The Water Division is committed to providing our community with safe and dependable drinking water. Activities range from patrolling the City's 36 square mile Mill Creek Watershed, to providing disinfection, and ultimately delivery to the customer.


To ensure the safety of your building water system and devices after a prolonged shutdown, please visit the Centers for Disease Control and Prevention website to receive guidance.

To request a new connection to the City's water system and applicable permit information, contact Development Services at 509.524.4710.

To report a water leak, please contact the Water Distribution Division. To report an issue after normal business hours, please call the non-emergency dispatch number.

If you would like the City to contact you if a potential water leak is detected, make sure your utility billing account is updated with current contact information. Please visit this page to sign up to be notified by phone or email if the City detects unusually high water use.

Water brochure February 2020

Folleto de la División de Agua    


Water Treatment/Hydro Power Generation


The City has two sources of water available to meet water demands. The primary source is a 36 square mile area forming the "Mill Creek Watershed". At its upper end lies the headwaters of Mill Creek. The Watershed area is protected. It is closed to the public allowing only limited access in coordination with the U.S. Forest Service. It is patrolled by a City Watershed Attendant and United States Forest Service personnel.
Water from Mill Creek is piped 14.5 miles to the City's Water Treatment Plant where it is treated using sedimentation, ozone, and chlorine to meet State and Federal Drinking Water Quality Standards before entering the distribution system.

The Mill Creek Watershed supplies 88-90% of the City's water need. In addition to this primary source, the City also has seven deep (800-1400') basalt wells used to supplement supply when stream levels decline in summer months. In an emergency, these wells would completely supply the city's needs. Wells are typically used when:

  • Surface water quality has changed due to weather events.
  • During the summer to meet increased water demands or when stream levels are low.


The City's Water Treatment Plant is capable of producing 24 million gallons of water daily that meets or exceeds Environmental Protection Agency and Department of Health Drinking Water Standards. Quality assurance is provided through stringent lab and system monitoring and testing.  Water is treated by using a roughing sand flow filter and is disinfected using UV light. The City maintains a state certified microbial laboratory at the Treatment Plant which provides efficient and timely water testing, testing results, and allows for rapid adjustments in treatment operations to consistent maintain water quality.

Hydro Power Generation

All water that passes through our Treatment Plant from the Mill Creek Watershed also passes through a hydropower generator which produces 13,500 megawatts of electricity annually (sufficient to power approximately 1,500 homes). Revenue from the generated power is used to offset operation and maintenance costs.

What is the City's plan to provide water should there be fire in the Mill Creek Watershed?

If a fire should occur in the Mill Creek Watershed, water from the creek will continue to be used until it no longer can be treated to meet Federal and State Drinking Water Standards. Should a fire impact water quality in Mill Creek, the City can provide 100% of the city's needs with well water. The deep basalt aquifer from where the water is pumped has sufficient supply to meet the City of Walla Walla's demand for 10 years or longer when supplemented by the City's Aquifer Storage and Recovery (ASR) Program. The ASR program stores water in the aquifer with treated Mill Creek water that meets Federal and State Drinking Water Quality Standards.

How will the City's ability to provide water from the Mill Creek Watershed be impacted if it should become unavoidable that fire retardant is used within the Watershed?

If the USFS determines it is necessary that fire retardant be applied within the Mill Creek Watershed, an avoidance zone of 300' on either side of Mill Creek will be maintained. If determined necessary, the city can switch to groundwater as a precautionary measure whenever the use of fire retardant is anticipated. Fire retardant contains nitrogen which spurs algae growth if it enters a water body.

Further information regarding the environmental impacts of fire retardant can be found at: 

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