Northern Health has determined that the City has now met criteria to downgrade the Boil Water Notice to a Water Quality Advisory. The City’s flushing program, initiated to help fast-track the downgrading of the Notice, has also ended this afternoon. If residents continue to see a milky quality or sediment in their water, please run cold water, preferably through your bathtub or laundry sink taps, until it is cleared.
For more information on precautions to take during a Water Quality Advisory, please skip to the lower half of this notice.
Why is the City able to Downgrade the Notice?
The City has met the condition to, “Demonstrate 3 weeks of satisfactory consecutive results showing that the raw water shows no detection for Cryptosporidium using method EPA1623 from an approved lab (this must be achieved at a minimum sampling frequency of 2 samples per week separated 24h+ apart from one another and results must be received within 96h of sampling) with an ongoing sampling program for Cryptosporidium and Giardia approved by the Environmental Health Officer. The operator must achieve the appropriate Contact Time (CT) value to deactivate the Giardia present at Shawatlan Lake with a post treatment Giardia cyst viability/infectivity audit program approved by the Environmental Health Officer.”
We have now had 5 or more consecutive clear samples for Cryptosporidium with our approved testing facility. The presence of Cryptosporidium was a primary motivation for the Notice, as it cannot be effectively treated with the City’s available treatment method of chlorination. There is no standardized “Maximum Allowable Concentration” for Giardia in drinking water guidelines, as its potential risk depends on the parameters of a community’s treatment system. Giardia can be deactivated (rendered harmless) with our available chlorination treatment, when it is above a certain level.
Rather than looking at a standardized maximum concentration, the City and Northern Health are using a new sophisticated statistical system called a Quantitative Microbial Risk Assessment (QMRA) provided by Health Canada that determines how effective our municipal water system is in deactivating Giardia if it is found to be present in our raw water supply (Shawatlan Lake). This program essentially identifies what level of Giardia is treatable with our available chlorination system. The model takes into account the specific parameters of our treatment system, including contact time water has with chlorine, the concentration of chlorine applied, temperature, and pH. Results from this statistical model show that during the course of the Boil Water Notice Giardia has remained within treatable limits, which, following multiple clear results for Cryptosporidium, is why we are able to downgrade the Notice to an Advisory.
What Monitoring will Continue?
The condition in place with Northern Health to meet treatable limits is also combined with a post treatment Giardia cyst viability/infectivity monitoring program approved by the Environmental Health Officer. The monitoring program, which tests for both Giardia and Cryptosporidium, will continue at a frequency of twice a week for the foreseeable future, until Northern Health determines it is safe to reduce frequency. Northern Health is currently working to determine an appropriate test schedule over the longer term.
In addition, health care providers will also continue to monitor for any illnesses directly related to water quality. Over the course of the advisory, and the months leading up to it, there was no outbreak of illness related to cryptosporidium or Giardia, which indicates that the Notice has been effective in ensuring positive health outcomes. Furthermore, the City’s test of the sewer system also did not test positive for Cryptosporidium or Giardia, further indication that there was no outbreak of illness.
What does a Water Quality Advisory Mean and Who Should Continue to Take Precautions?
A Water Quality Advisory does remain in place as a precaution for those considered most ‘at risk’. A Water Quality Advisory indicates a level of risk associated with consuming the drinking water, but the conditions do not warrant a boil water notice or do-not-use water notice. It is the lowest level notification, and is issued as a precautionary measure (particularly to those with compromised immune systems that they should take appropriate steps, such as boiling their water prior to consuming).
As per Northern Health guidance, some risk may remain for particularly at-risk people such as newborns, the elderly and people with weakened immune systems.
The following sensitive customers should be careful when ingesting the water:
- Children and infants under the age of 2 years
- The elderly (65 years of age and older)
- People with weakened immune systems (if unsure consult with a physician)
For these sensitive customers, as a precaution, all water intended for the following uses should be boiled for 1 minute.
- Washing fruits and vegetables
- Making beverages or ice
- Brushing teeth
Alternatively, sensitive customers could choose to use bottled or distilled water, or water that has been appropriately filtered through a well-maintained treatment device.
Owners of public facilities are requested to post Water Quality Advisories at all sinks or drinking water fountains accessible to the public, alternatively, public fountains and taps may be turned off). As opportunities arise they must also advise their clientele verbally of the WQA.
What are the City’s next steps?
Moving forward, City staff will compile a report in conjunction with Northern Health on ‘lessons learned’ from the Notice, including opportunities for improvement should an event like this occur in future. This information will be presented at a meeting of Council in February.
Veronika Stewart, Communications Manager
City of Prince Rupert
(778) 884 6285