Skip to Main Content View Text-Only

Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.


1120 SW Fifth Ave, Suite 600, Portland, OR 97204

More Contact Info

Subscribe to RSS feed

Most Recent

View More

Cryptosporidium Treatment FAQ

Table of Contents:

Main | How We Got Here | What’s Next? | How Will This Impact My Bill? | Cryptosporidium Treatment FAQs

Updated: Aug. 4, 2017

What is Cryptosporidium

Cryptosporidium is a microscopic parasite that lives in the intestines of infected animals or humans. An oocyst (oh-sist) refers to the resting stage of a single Cryptosporidium organism. The oocyst has a protective shell-like structure that protects the organism from harsh environmental conditions, such as chlorine disinfection. Many types of Cryptosporidium exist, but not all are known to cause illness in humans.

Does Portland treat for Cryptosporidium?

No. On March 14, 2012, the Oregon Health Authority (OHA) issued the Portland Water Bureau a 10-year variance from treating Bull Run drinking water for Cryptosporidium. As a result of the variance, the bureau was the only surface water system in the country that did not have to treat for Cryptosporidium. The treatment variance was issued in accordance with federal and state regulations.

Why was the Portland Water Bureau granted a treatment variance?

In 2011, Portland Water Bureau demonstrated to OHA that the Bull Run water source is of such high quality that no additional treatment for Cryptosporidium would be necessary to protect public health. Extensive water quality monitoring in 2009–2010 showed that the average Cryptosporidium concentration was below the EPA’s variance threshold of 0.075 oocysts per 1,000 liters, which is equivalent to the level of public health protection that a system with treatment would provide.

The Bull Run Watershed has stringent watershed protections, a natural environment that limits contamination, and is protected from the most common Cryptosporidium sources such as human waste and livestock.

What has changed?

The data has changed. Current data indicates that Portland can no longer demonstrate Bull Run water is below the EPA-determined level for treatment.

Starting in January 2017 and continuing through March 2017, the bureau detected low levels of Cryptosporidium in several raw water samples from the Bull Run Watershed. A total of 19 individual Cryptosporidium oocysts were detected over this timeframe—the first detections since December 2011.

On May 19, 2017, the bureau received a letter from OHA, the bureau’s regulatory authority, revoking the variance. The original revocation date was September 22, 2017, or when a treatment plan and interim measures plan were approved, whichever was sooner. With the 60-day extension granted by OHA, the new compliance schedule is due October 11, 2017, and the new revocation date is November 22, 2017.

What considerations went into this decision by Council?

To respond to OHA’s decision to revoke the variance, Council originally had two treatment options to weigh:

Ultraviolet (UV) treatment. UV deactivates Cryptosporidium and met the near-term regulatory requirements, but offered no other benefits against other risks to the water supply. It was the lowest price option.

Filtration. Filtration met regulatory requirements and had additional benefits, but came with a higher price.

Benefits of UV Benefits of Filtration
  • Treats only for Cryptosporidium
  • Treats for Cryptosporidium
  • Removes other pathogens
  • Reduces disinfection byproducts
  • Addresses high turbidity caused by storms, earthquakes, landslides, or fires
  • Potentially increases the water supply
  • Addresses potential algae issues
  • Keeps sediment out of the distribution system
  • Reduces reliance on groundwater


A third option of “UV Plus” was offered by Mayor Ted Wheeler at the June 27, 2017, work session. He requested the bureau examine an option of implementing UV now, and then setting aside a savings fund for eventual upgrades to UV facilities or a filtration plant in the future.

The Portland Water Bureau provided information on treatment options to City Council, local and state health officials, community stakeholders, and the media. For the month leading up to the Council decision, the Water Bureau solicited comments from the public via an online comments submission page. The results were delivered to City Council.

Ultimately, Council unanimously decided on filtration. Many Commissioners cited the long-term benefits as a deciding factor.

Is our water safe to drink?

Yes. The bureau’s regulator and public health partners agree that the risk to public health remains low. Ongoing public health surveillance has not shown any increase in Cryptosporidium-related illness. As always, people with severely weakened immune systems should seek specific advice from their health care providers about drinking water.

Is the bureau in compliance with the Safe Drinking Water Act?

Yes, the Portland Water Bureau continues to adhere to all state and federal drinking water regulations. To remain in compliance, by October 11, 2017, the bureau will submit

  1. A description of which Cryptosporidium treatment technology the Portland Water Bureau intends to pursue.
  2. A detailed proposed schedule of when the treatment will be in place.
  3. Measures the Portland Water Bureau intends to take to reduce the risk of the public's exposure to Cryptosporidium until treatment is in place.
  4. A proposed sampling schedule for Cryptosporidium at the intake until treatment is in place.

What does the City intend to do now to comply with Cryptosporidium regulations?

The bureau will construct a water filtration plant, per the decision of City Council on August 2, 2017.

It will adhere to the deadlines set forth in OHA’s August 1, 2017, letter: submission of a compliance schedule and interim measures plan by October 11, 2017 and recognizing November 22, 2017, as the revocation effective date if the plan is not approved earlier than that.

Where would the treatment facilities be located?

There has not yet been a thorough assessment of the location of a filtration facility but near the bureau’s Lusted Hill facility is the most likely location.

What would the impacts of development be for the watershed?

A filtration plant would not be located within the watershed. Included in the Portland City Council’s decision on August 2, 2017, the bureau was directed to continue its efforts and advocacy in keeping the Bull Run Watershed protected.

Are chemicals added to drinking water by filtration?

Filtration removes Cryptosporidium and other contaminants by pushing water through a membrane or water settling through sand or charcoal. For conventional or direct filtration, aluminum and iron salts are the most commonly used coagulants in water treatment. Aluminum does have a secondary maximum contaminant level (SMCL) for aesthetic purposes of 0.05–0.2 mg/L. Iron is also a naturally occurring compound and also has a SMCL of 0.3 mg/L for aesthetic purposes.

At concentrations typically observed in drinking water, neither aluminum nor iron have been identified as harmful to human health.

Coagulants cause materials such as organics, bacteria and other particles to clump together prior to being filtered out of the water (the clumps formed are typically called flocs). Depending on the type of filtration selected, a polymer may also be added to enhance floc formation.

These treatment residuals—the chemical coagulants and particles attached to them—are removed before the water enters the drinking water system.

How will treatment affect the taste of the water?

It is not yet known to what extent this will change the taste of the water, but it can remove algae that have been known to cause unpleasant taste and odor in the summer and may allow the bureau to use less chlorine.

What is the timeline?

Planning for and constructing a filtration facility would take approximately 10–12 years.

How much will filtration cost? How will this impact rates?

There will not be any impacts to rates in 2017.

The estimated cost to design and construct filtration is between $350 and $500 million. As is the case with large capital projects such as this, decisions on matters such as treatment method, size of plant, construction timeline, and other major decision points throughout the 10–12 year project will narrow specific cost estimates as planning and design continues.

Using the most expensive cost estimate of $500 million, bureau modeling shows:


In Year 1 (2018)

In Year 10 (2028)

In Year 15 (2023)

For the average bill,
filtration will raise rates
each month by...




Again, please note that the impact-to-ratepayer estimates above use the most expensive design options and most conservative financial assumptions. They also exclude any rate stabilizing efforts or cost offset programs. Estimates represent the highest possible cost scenario and are expected to come down.

What happens if the bureau has another detection of Cryptosporidium before the treatment facility is operational?

The Water Bureau will take measures to reduce the risk of the public’s exposure to Cryptosporidium until filtration is in place. These measures will be at least as protective as the measures that were required under Portland's treatment variance issued by OHA. The bureau will continue frequent monitoring for Cryptosporidium at the raw water intake, environmental inspections, tributary monitoring, and wildlife analysis. It will continue to work closely with state and county health officials to monitor public health surveillance data. The bureau will continue to take any appropriate precautionary actions, including the substitution of the Columbia South Shore groundwater source for the Bull Run when practicable and should such actions become necessary based on public health surveillance data, Cryptosporidium DNA testing results, or other relevant findings from watershed investigations.

As the bureau demonstrated in early 2017, it will be ready to respond if necessary. The bureau will continue to vigilantly monitor for Cryptosporidium, continue to protect the watershed, notify the public, and work with its health partners to make the best decisions for public health.

What precautions can customers take at home to reduce their risk of exposure to Cryptosporidium until treatment is in place? Can I use my own filter?

Yes, you can use a filter. Make sure that it is labeled and certified to remove Cryptosporidium and is NSF/ANSI 53 or 58 rated. Look for the language “cyst reduction” or “cyst removal”. Reverse osmosis and carbon filters are the most common types of filters available. Make sure that the manufacturer states “absolute” pore size of 1 micron or smaller. If the brand only states “nominal” pore size of 1 micron, then it may not remove all Cryptosporidium. Because the filter cartridges collect Cryptosporidium, it is recommended that they are replaced by a person that is not immuno-compromised while wearing gloves. Follow the manufacturer's recommended filter cartridge replacement schedule.