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Water Treatment

The city has two water treatment plants, treating approximately 6 billion gallons of drinking water per year. This water is delivered through 450 miles of pipeline to homes and businesses within the 26 square mile service area (see map) and is used for drinking water and other residential use, irrigation, and firefighting. Average water use is 10 million gallons per day in the winter and 28 million gallons per day in the summer.

Betasso Water Treatment Plant is located in the foothills west of Boulder and treats water from North Boulder Creek and Barker Reservoir, which is fed by Middle Boulder Creek. 

Boulder Reservoir Water Treatment Plant treats water from Carter Lake, which is part of the larger Colorado-Big Thompson water system operated by Northern Colorado Water Conservancy District



Water Treatment Process


Chlorine can be added at different locations in the treatment process to kill disease causing microorganisms and prevent microorganisms from growing during the water treatment process. This is usually done before filtration.


Coagulants are added to the water to aid in particulate removal. Aluminum sulfate is used as the coagulant at the Betasso Water Plant, while aluminum sulfate and a polymer are used at the Boulder Reservoir Treatment Plant. At the coagulant feed point, the water is mixed rapidly too distribute the chemicals evenly. The coagulant breaks down repelling forces between small suspended particles. This rapid mix is followed by a slow mix. During the slow mix, the suspended particles begin to form larger collections of solids called "floc." This process is called "flocculation."


Water then goes into four basins at Betasso where the larger, heavier, floc particles settle to the bottom. The Boulder Reservoir Treatment Plant uses Dissolved Air Flotation, or DAF units. DAF is a physical process where microbubbles attach themselves to particles in the water and float them to the surface where they form a removable, floating sludge blanket.


After the sedimentation process, the water flows to the filters where the smaller floc particles are filtered from the water.


After filtration, just enough chlorine is added to the water to keep the piping system and storage reservoirs in the City of Boulder free from pathogens and to maintain a residual to the tap as required by state law.

Corrosion Control

At the Betasso Water Treatment Plant, calcium hydroxide (lime) and carbon dioxide are added to the water after filtration to raise the alkalinity (buffering capacity) and pH of the water to make it less corrosive to pipes. At the Boulder Reservoir Water Treatment Plant, alkalinity and pH are consistent with Betasso's water.


Fluoride is a mineral that is naturally found in air, soil, water, plants and foods. Boulder's water sources contain small amounts of natural fluoride. The city also adds fluoride to the drinking water to achieve a target level of 0.7 mg/L, which is based on 2015 federal and state guidance. The City of Boulder continues to pay close attention to scientific and regulatory developments and, as always, will comply with all regulatory changes.

Schedule a Tour

Due to COVID-19 restrictions, the Boulder Water Treatment Plants are currently not accepting reservations for tours. Our team is committed to public safety and is using an abundance of caution to keep facilities staffed and operational 24/7 to ensure safe, reliable water and wastewater services. For more information, click here.  

Free tours are available Monday through Friday, 9 a.m. to 4 p.m. Two weeks notice is required.  To schedule a tour, please submit the "Tour Request Form" below on this webpage. Please note that tours at Betasso Water Treatment Plant are not available until after the capital improvement projects have completed.

Professional Tours

  • Tours can accommodate a minimum of 5 and maximum of 20 visitors per available tour guide.
    • Requests for larger groups will need to be approved by management to ensure safety and the group may be split up into smaller groups.
    • Single individuals will likely be added to the next available group tour.
  • Tour days and times may vary based on staff availability and facility priorities.
  • Tours are available on a first-come, first-served basis.  Requested dates are not always guaranteed.
  • A standard tour may take at least one hour to complete and requires walking throughout the tour.
  • A full, in-depth tour may take up to two hours and can include a half-hour presentation, followed by a walking tour. This is based on availability of operators.
  • Attire: closed-toe shoes only.  Please no heeled shoes, sandals or flip-flops. Dress appropriately for outdoor conditions. You will be touring an industrial site and there is some walking outdoors.
  • Tour groups that arrive unprepared or without the required number of chaperones may be denied a tour.
  • The City of Boulder adheres to strict ‘no smoking’ and ‘zero waste’ policies.  Please, no smoking, littering, eating, or drinking during the tour.  Plant staff can advise on local meeting spaces suitable for group lunches before or after the tour.
  • Restrooms and drinking fountains are available on-site at the beginning and end of the tour.
  • Please do not touch the equipment without permission. 
  • Staff reserve the right to end a tour at any time. Safety is our first priority.
  • Questions are welcome and encouraged!

School Group/ Youth Tours

  • The minimum participant age is 9 years-old (fourth grade)
  • Chaperones are required for school/ youth group tours with participants who are 18 years of age and younger.
    • Grades 4 and 5: 1 chaperone for every 5 students
    • Grades 6 through 8: 1 chaperone for every 8 students
    • High school: one chaperone for every 10 students
  • Chaperones will be expected to manage the participants to ensure optimal safety.