Portland’s currently unfiltered Bull Run Watershed will undergo a $500-million project to add a facility filtering Portland’s water for the first time when it comes online by September 2027.

Brown and Caldwell won the contract to provide program management services for Portland Water Bureau’s Bull Run Filtration Project, which will include a plant that can filter 160 million gallons per day and the equipment to connect to the city’s existing supply system.

Portland water customers have received unfiltered water from the federally protected 102 square mile Bull Run Watershed for over a century, but traces of cryptosporidium, a potentially disease-causing microorganism, have led the Oregon Health Authority to revoke the water bureau’s treatment variance last year, leading to the new plant.

“Public health and safety is the bureau’s top priority,” says PWB program director David Peters in a statement. “This transformational opportunity for the city will further protect and improve our primary source of drinking water for the long-term benefit of our customers.”

The Portland Water Bureau first received a variance from the Oregon Health Authority in March 2012, based on results of a year-long intensive sampling for cryptosporidium showing a low occurrence of the organism in the Bull Run Watershed. That variance was revoked in May 2017 and led the city and health authority to enter into negotiations on how and when to filter Bull Run Watershed water.

The authority, in a statement to ENR, said the “possibility of disease-causing cryptosporidium exists even in a protected watershed like Bull Run.” The authority said it wants to work with the water bureau to ensure treatment gets installed as quickly as possible.

Brown and Caldwell will first run pilot testing and project definition work to determine the preferred treatment system before moving forward with permitting and detailed budget and scheduling. The firm does expect the water bureau to sign contractors in 2019 and following pilot testing and design, Brown and Caldwell expects construction to begin in late 2022. The Sept. 30, 2027, date of operation was agreed upon between the city and health authority.

The Portland City Council selected water filtration as the best way to handle cryptosporidium because they expect the process to remove an array of organisms from the water supply and potentially allow the city to use less chlorine disinfection in the future. Using less chlorine and removing more organic material could potentially result in fewer byproducts within Portland’s water.

The project will also provide more stability in the Portland drinking water. Without filtration, the Bull Run Watershed cannot be used when elevated turbidity or sediment enters the water, common during heavy storms or nearby fires. Filtration will remove sediments, as well as algae that can affect taste.

Follow Tim Newcomb on Twitter at @tdnewcomb.