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Cryptosporidium and Future Treatment FAQs

Table of Contents:

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

Updated: Nov 1, 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.

What are common symptoms of Cryptosporidium infection?

Cryptosporidium is a microscopic parasite that can cause the disease cryptosporidiosis. Cryptosporidium can be spread in a number of ways, including ingestion of contaminated drinking or recreational water, exposure to unwashed hands, surfaces, or food that is contaminated by infected human or animal stool. Symptoms of cryptosporidiosis may include diarrhea, nausea, vomiting, stomach cramps, and fever. The symptoms can range from mild to severe. Cryptosporidiosis is not the only illness or condition that can cause these symptoms. These sympto

ms are common in the general population – up to 2 percent of the public can have similar symptoms on any given day (11,000 people in Portland). Health professionals recommend that you seek medical advice if you are experiencing these symptoms and they persist for more than a few days. Portland-area health departments monitor for indications of an increase in Cryptosporidium-related illness that could be related to drinking water. 

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.

Is our water safe to drink?

Yes. At this time, the bureau and public health partners at Multnomah County continue to believe Bull Run water is safe to drink. 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.

What happened?

Cryptosporidium has been detected from a series of samples collected in late October through November, at the Bull Run drinking water intake. These follow earlier low level detections  of Cryptosporidium in September and January through March 2017. The Portland Water Bureau is coordinating with public health officials and notifying the public of this detection. Updated results from continued monitoring can be found on the Cryptosporidium Treatment Variance Monitoring Results page.

What should the public do?

The general public is not being asked to take any additional precautions at this time. The City is working closely with the Multnomah County Health Department and State of Oregon Health Authority. Based on these detections, public health officials do not expect any health impacts for the general population from the detection of low amounts of Cryptosporidium. However, as always, people with severely weakened immune systems should seek advice from their health care provider.

What is Portland doing as a result of these detections?

As required by the conditions of the variance revocation order from OHA, the Portland Water Bureau has been testing at least 200 liters per week (53 gallons) from the source water intake for Cryptosporidium since May 2017. The Portland Water Bureau will conduct an investigation and additional testing to obtain more information about this Cryptosporidium detection. Additionally, the Portland Water Bureau is working in continued coordination with health officials to monitor public health surveillance data that tracks reported cases of illness from Cryptosporidium.

The Portland Water Bureau will install treatment technology to meet the treatment requirements for Cryptosporidium. On Aug. 2, 2017, the Portland City Council unanimously directed the Portland Water Bureau to pursue filtration to treat for Cryptosporidium. A schedule for construction of the plant will be in place by Nov. 22, 2017. 

The bureau continues to vigilantly monitor for Cryptosporidium, protect the watershed, notify the public, and work with its health partners to make the best decisions for public health.

Does Portland currently 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. After a series of detections for Cryptosporidium from January to March 2017, OHA notified the Portland Water Bureau that the variance would be revoked.

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 from 2009 to 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?

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 Sept. 22, 2017, or when a treatment plan and interim measures plan were approved, whichever was sooner. With a 60-day extension granted by OHA, a proposed compliance schedule and interim measures were submitted to OHA on Oct. 9, 2017, and the new revocation date is Nov. 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 inactivates 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 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, on Oct. 9, 2017, the bureau submitted

  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 Aug. 2, 2017.

It is adhering to the deadlines set forth in OHA’s Aug. 1, 2017, letter and submitted a compliance schedule and interim measures plan on Oct. 9, 2017. Nov. 22, 2017, shall be 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. Lusted Hill is located outside of the Bull Run Watershed.

Portland water system map

'What are the impacts of filtration on 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 filters. For conventional or direct filtration, alum and iron salts are the most common additives used in water treatment. These salts aid in the clumping of contaminants and other particles, making them easier to filter out of the water. Most of these additives are removed during the filtration process. At concentrations typically observed in drinking water, neither alum nor iron have been identified as harmful to human health.

How will treatment affect the taste of the water?

It is not yet known to what extend filtration will change the taste of the water, but filtration 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, further reducing occasional taste and odor issues.

What is the timeline?

The Portland Water Bureau submitted a proposed timeline to OHA on Oct. 9 and will work with regulators to agree upon a final schedule by Nov. 22. Planning for and constructing a filtration facility could possibly take 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 project will narrow specific cost estimates as planning and design continues.

The monthly water bill for the typical single family residential customer using 5 ccf a month in fiscal year 2017-2018 is $36.10. Click to learn how to read your sewer, stormwater, and water bill.

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


In Year 1 (2018)

In Year 10 (2028)

In Year 15 (2033)

For the average bill,
filtration will raise
monthly rates by...




These 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.