The city has two water treatment plants, treating approximately 6 billion gallons of drinking water per year.
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 Barker and Silver Reservoirs, which are fed by Middle Boulder Creek and North Boulder Creek.
Betasso is currently being upgraded to replace aging equipment and support updated treatment processes.
Tours of the Betasso Plant are on hold through the end of 2024 due to construction and will resume in early 2025.
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.
Pre-Disinfection
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.
Coagulation
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."
Sedimentation
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.
Filtration
After the sedimentation process, the water flows to the filters where the smaller floc particles are filtered from the water.
Post-Disinfection
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
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.
