Adverse events and observations: small drinking water systems
When something goes wrong with your small drinking water system, the event may be referred to as either an adverse observation or an adverse test result, and specific notification requirements and corrective actions will be required.
In the event that an adverse event or observation requires a drinking water advisory, the information will be made public on Public Health Sudbury & Districts’ disclosure website, Check Before You Go!
What is an adverse event and how do I respond?
You are required, as an owner or operator of a small drinking water system, to provide users with safe drinking water at all times.
When something goes wrong with your drinking water system, the event may be referred to as either an adverse observation or an adverse test result, and specific notification requirements and corrective actions will be required.
The regulation provides the initial directions with regard to the appropriate response, which may include actions such as:
- notifying the users of the drinking water system
- taking necessary steps to correct the problems
- notifying the Medical Officer of Health (MOH)
What should I do if my test results for bacteria are “adverse” or “unacceptable”?
If your test results indicate your drinking water is unsafe, then you must:
- stop using the water supply for drinking unless boiled
- notify all other users to avoid drinking the water and to use an alternative source
- follow the notification requirements listed in the regulation
- contact Public Health Sudbury & Districts
What is an adverse observation?
An “adverse observation” means that you, or an employee of the small drinking water system for which you are responsible, observed an event (other than an adverse test result) that suggests that the system may not be providing water that is safe for the users to drink.
Some of these events may include:
Inadequate filtration of the water entering the system
Turbidity (cloudiness) is an indication of how heavily contaminated the water is. Therefore, if turbidity is seen, the existing treatment system may not be providing adequate disinfection and may require adjustment of the chemical levels or other action.
Low disinfection levels in the distribution system
Proper disinfection levels throughout your distribution system will prevent build-up of biofilm. If biofilm builds up, it can reduce the effectiveness of the disinfectant used to protect the water from the growth or re-growth of harmful micro-organisms.
Contamination of the small drinking water system due to the possibility of back siphonage
If there is a cross connection in the piping of your system, during low pressure situations, the drinking water may become contaminated with waste water or other untreated water.
What is an adverse test result?
An “adverse test result” means a drinking water test result that shows any of the following outcomes that differ from Ontario Regulation 169/03 – Ontario Drinking Water Quality Standards under the Safe Drinking Water Act, or from a directive issued under the Small Drinking Water Systems Regulation.
Laboratory testing
Microbiological parameters
Under the regulations, owners and operators are required to ensure that at least one sample is taken as per the directive for their drinking water system.
Your water test results should be free of Escherichia coli (E. coli) and total coliforms bacteria.
The presence of these organisms is an indication of recent fecal contamination or entry of surface water and a warning that there is a risk to the health of users of your drinking water system.
Chemical or radionuclide parameters
Sometimes there may be high concentrations of chemicals (nitrate or lead) or radionuclide (uranium or radon) parameters in your source water. These may occur naturally or as a result of an accident such as a spill.
The public health inspector may include requirements in the directive for specific chemical or radionuclide testing based on a site-specific risk assessment.
Non-laboratory checks – adverse observations
Disinfection residuals
Where the system is required to provide secondary disinfection, the test results should be in accordance with the type of disinfection that is used. The use of chemical disinfection will inactivate bacteria present in the water and prevent re-growth of bacteria or biofilm during storage.
Free available chlorine (FAC) residual
If the system is chlorinated, the FAC concentration must be at or above 0.05 milligrams per litre (mg/L) collected from the plumbing or the distribution system, unless your directive specifies otherwise.
Combined chlorine residual
If the system is disinfected by chloramination, you must maintain the combined chlorine residual concentration at least 0.25 milligrams per litre (mg/L) in the distribution system.
Who should I notify of any adverse test results or observations?
Small drinking water system operators are required to immediately report to the local Medical Officer of Health (MOH) every adverse observation or test result that would indicate the system may not be providing safe water to users. The immediate notice to the MOH must be done by speaking in person or by phone with the public health inspector or the after-hours on-call inspector.
A follow-up written notice within 24 hours must also be sent to the MOH. You can do this by completing the notice of adverse test results and issue resolution form.
If you are reporting an adverse water test result or observation to Public Health Sudbury & Districts, you must call 705.522.9200 and state that you need to speak with a live person as you are mandated to report an adverse water test result or observation. If you are reporting an adverse water test result or observation after-hours, you must call 705.688.4366 and an agent will send a page to the after-hours on-call inspector. A public health inspector will call you back with steps to follow to resolve the problem.
Both the immediate report and the 24-hour notice must specify the adverse result or observation, the actions being taken in response, and whether any required corrective action (specified in the regulations) is being taken.
What are general corrective actions?
In addition to the above general notification requirements, the small drinking water system regulation also includes corrective actions and notification requirements according to the specific adverse result or observation in question. Some examples are as follows:
Presence of E. coli
- Immediately notify all users of the drinking water system to use an alternate source of drinking water or, if none is available, to bring their water to a rapid, rolling boil for at least one minute before use.
- Immediately notify the MOH.
- Immediately resample and test. Follow the requirements given to you by a public health inspector.
If your drinking water system uses chlorine, immediately increase the chlorine dose and flush the system to ensure there is adequate chlorine residual.
Maintain the residual until two consecutive water samples taken 24 – 48 hours are free of E. coli.
Presence of total coliforms
- Immediately notify the MOH.
- Resample and test as soon as possible.
If your drinking water system uses chlorine and total coliforms are still detected upon resampling, immediately increase the chlorine dose and flush the system to ensure there is adequate chlorine residual.Maintain the residual until two consecutive water samples taken 24 – 48 hours apart are free of total coliforms.
If your SDWS does not use chlorine, immediately follow the steps for temporary disinfection of the system as required by the MOH (consistent with the Ministry of Health and Long-Term Care’s Procedure for Corrective Action for Small Drinking Water Systems that are Not Currently Using Chlorine).
Improper disinfection
- Immediately restore the disinfection.
- Immediately notify and instruct all users of the drinking water system to use an alternate source of water or, if none is available, to bring their water to a rapid, rolling boil for at least one minute before use.
- Immediately notify the MOH.
Other adverse events
When an adverse event is not a result of bacterial contamination, you may need to apply different corrective measures than those listed above. Some adverse events may be caused by any of the following:
- Chemical spill that enters the source water that supplies your drinking water system (for example, diesel or other petroleum-based products).
- Agricultural products that enter your drinking water system source either from a run-off or by leaching into the aquifer that supplies your system.
- Broken pipes or water mains that become contaminated.
- Naturally occurring chemicals or radiological agents such as nitrate, lead or uranium.
At such times, you must notify Public Health Sudbury & Districts and follow any steps required by the MOH or public health inspector to resolve the problem.
Will there be additional requirements from Public Health?
In addition to the specific regulatory requirements for responding to adverse observations and adverse test results, the MOH or public health inspector may issue additional requirements to correct the problem. These steps are mandatory.
What do I do when the problem is resolved?
Once you have taken the necessary steps to remedy the problem that caused the adverse test result or observation, you must provide a written notice to the MOH summarizing:
- actions that were taken to correct the issue; and
- the results that were achieved.
The written notice must be on the same Notice of Adverse Test Results and Issue of Resolution form advising of the adverse water test result or observation.
Remember, if you are uncertain of what actions to take, immediately contact Public Health Sudbury & Districts and speak with a public health inspector at 705.522.9200 (toll-free 1.866.522.9200).
This item was last modified on August 27, 2018