1.0 Purpose

This document explains the key terminology and methodology used by the Town of Markham to systematically assess the hazards and associated risks to which its drinking-water system is exposed. SOP- Risk Assessment Procedure has been developed to describe the process for identifying, assessing and ranking potential drinking water quality hazards, and identifying critical control points, control measures and monitoring procedures, based on the background information presented in this document. SOP- Risk Assessment Review Procedure explains the tasks involved in conducting a review of the risk assessment outcomes.

2.0 Scope

Risk Assessment applies to all Town of Markham business practices that relate to the distribution of safe drinking-water and to all personnel involved in these processes. The QMS Controller will be responsible for the application of the process and procedures explained in this document.

3.0 Definitions

· A Drinking Water Quality Hazard is a possible source of danger that may cause drinking water to be unsafe for human consumption. It is a biological, chemical, or radiological agent that has the potential to cause harm. Under the scope of the DWQMS, only hazards related to drinking water safety must be considered. For example, health and safety or environmental hazards need not be included if they do not present a hazard to drinking water safety.

· A Hazardous Event is an incident or situation that can lead to the presence of a hazard. Hazards and hazardous events can result from natural or technological causes, or from human activities.

For this exercise four different types of hazards are defined:

· Biological Hazards correspond to biological pathogens that may be present in the water. Waterborne biological hazards include bacterial, viral and parasitic organisms that may occur naturally or may be caused by the introduction of waste and other substances into the environment by humans or other animals. Biological hazards also include substances and particles that cause turbidity, since they can be a source of disease-causing organisms, and can shield pathogenic organisms from the disinfection process

· Chemical Hazards refer to contaminants that may be naturally occurring or may be added or created during the processing of water, and if present at high levels can have negative health effects.

· Radiological Hazards include all those substances that may have a negative impact on human health due to their emission of radiation. There are more than 200 radionuclides (radiation emitting substances). Some occur naturally while others are products from human activities such as mining and nuclear energy production. Ingestion of radionuclides in drinking water may cause cancer in individuals exposed and hereditary genetic changes in their children.

— Capacity Hazards are factors that affect the distribution system’s ability to supply water to its customers. Any of the above three hazard types can be a capacity hazard since it can lead to scenarios when supply of drinking water is interrupted.

— Control Measures refer to any processes, steps, or contingencies to prevent or reduce a hazard. For clarity purposes, the terms preventive control measures, monitoring procedures/processes, and response/mitigating measures are used for the risk assessment to distinguish between actions to eliminate or reduce the occurrence of the hazardous event before it occurs, actions to track the change of parameters that are related to the presence of the hazard, and actions to mitigate the effects of the hazardous event once it has occurred, respectively.

— A Critical Control Point refers to an essential step or point in the water system at which control can be applied to prevent or eliminate a drinking water health hazard or to reduce it to an acceptable level.

— A Critical Control Limit is a level of a hazard (or the process variable used to monitor the hazard) at which a Critical Control Point response is initiated.

— Risk is the magnitude of the identified hazards causing harm measured as a numerical score that includes their likelihood, severity and detectability. For this risk assessment, risk is defined as the sum of the likelihood, severity and detectability scores.

— Likelihood is the probability of occurrence of a hazard or hazardous event. It may also be referred to as “frequency.”

— Severity is the magnitude of the effects or consequences of the hazard/hazardous event if the hazard is not controlled. For this risk assessment, only the potential effects on human health will be considered to define severity.

— Detectability is a measure of how easy it is to identify the occurrence of a hazard/hazardous event. It contributes to risk since as the detectability of a hazard decreases the more difficult it is for appropriate control measures to be implemented.

4.0 Procedure

The DWQMS Guidance Document lists 12 main tasks as part of the risk assessment. This section explains the considerations and methodology used to perform each of these 12 tasks.

4.1. Risk Assessment Team

Performing a risk assessment requires a good knowledge of the system in question, including all aspects of the system from operation and maintenance, management and design. For this reason, it is recommended that the assessment be conducted by a group of people with a wide-ranging knowledge of the system. The risk assessment team should include representatives of other areas of the Town which are related to the provision of safe drinking water.

4.2. Risk Assessment Approach

The approach taken to conduct the assessment is based on the process illustrated in the DWQMS Guidance Document. It involves recognizing the three types of hazards (defined in the previous section) for each of the processes/components of the subject system. The components considered for the assessment include the following:

— Storage and distribution elements: Piped transmission systems (including appurtenances);

— Customer elements: Interactions with others - e.g. domestic and commercial, industrial and institutional customers, and neighboring municipalities.

4.3. Hazard Identification

The risk assessment is conducted in a series of risk identification workshops during which hazards to water quality are identified, given a score (assessed), and ranked. Control measures already in place are identified, and when necessary, recommendations for new control measures are developed.

The reliability/redundancy of the equipment and infrastructure forming part of the distribution system was considered when identifying hazards/hazardous events and control measures. The effect of equipment failure was determined and assessed when considering high risk areas.

4.4. Control Measure Identification

The method outlined in the Hazard Identification subsection above was used to identify available preventive control measures. The control measures recorded included all projects/processes not yet completed or implemented at the time of the assessment, but that are expected to be concluded by the time the DWQMS Operational Plan is completed. This was reflected in the Risk Identification Table, both by listing such projects and adjusting the total risk score.

4.5. Risk Assessment

Risk was expressed as the sum of likelihood, consequence and detectability, each of which was assigned a value between 1 and 5. A high value indicated high risk (e.g. a hazard with a high likelihood, high severity, and low detectability was given a high score). The likelihood, consequence and detectability ratings were assigned to better reflect the reality of the Town of Markham’s system and standards of operation. Figure 1 below shows the rating systems for each of the risk criteria, with their qualitative and quantitative ratings.

Figure 1 Likelihood, Severity and Detectability Rating System
Description	Likelihood of Hazardous Event Occurring	Rating
Rare	Has not occurred in the past. May occur in exceptional circumstances.	1
Unlikely	Historically has occurred less than once every 25 years. Has occurred in the collective memory of the group.	2
Possible	Has occurred or may occur once or more very 5 to 10 years.	3
Likely	Has occurred or may occur once every six months.	4
Very Likely	Occurs on a monthly or more frequent basis.	5
Description	Severity of Hazardous Even Occurring	Rating
Insignificant	Does not affect any customers. Some manageable operation disruption.	1
Minor	Affects a single street or small service area, but has no health effects.	2
Moderate	Could lead to a drinking water advisory. Potential for more severe effects if not mitigated immediately.	3
Major	Affects system at a pressure zone level. Affects critical customer. Could lead to illness.	4
Catastrophic	No water in distribution system. Potential serious health incident leading to death. Complete system failure. Affects whole population.	5
Description	Detectability of Hazardous Event	Rating
Very detectable	Easy to detect. On-line monitoring through SCADA. Real time monitoring and alarm.	1
Moderately Detectable	Problem can be indicated promptly by in-house lab test results done daily. Problem reported by customers. Operator rounds daily.	2
Normally Detectable	Part of a sampling program, but lab test not done on a regular basis (weekly or less frequent). Operator rounds or inspection at least once a year.	3
Poorly Detectable	Only found by chance. Not normally detected before problem becomes evident.	4
Undetectable	Cannot detect.	5

4.6. Risk Ranking

Based on the above, four risk categories were defined depending on the risk range of the particular hazard/hazardous event. Figure 2 below illustrates these categories.

Figure 2 Risk Assessment Categories
Risk = Likelihood + Severity + Detectability	Risk Category
3 - 5	Low
6 - 8	Moderate
9 - 11	High
12 – 15	Very High

All risks with values of 9 and over (categories “High” and “Very High”) were given the highest priority. The rationale for this cut-off value is that there are 19 different possible sums of the above criteria (likelihood, severity and detectability) that result in a risk score of 9. All these are due to a combination of a low value of one of the criteria and a high and/or moderate value for the remaining two criteria, or a moderate value of the three criteria. Any of these combinations was deemed critical to water quality and considered to require control either in the form of preventive measures, monitoring and/or responses.

4.7. Critical Control Point Identification

As defined previously a Critical Control Point (CCP) is an essential step in the water system at which control can be applied to prevent or eliminate a drinking water health hazard or to reduce it to an acceptable level. For the Risk Assessment, a CCP was defined as such if it had an associated hazard/hazardous event with a risk value over 8, and if the hazard was controllable at that area. If the hazard had a risk value over 8 and was not controllable (preventable), contingency or emergency response procedures were identified.

4.8. Critical Control Limits

Critical Control Limits are specified as numerical values indicating maximum, minimum, or a range of values for the key variables controlling the effectiveness of the disinfection process, or which best describe the presence of the hazard related to the CCP. Generally, the control limits are set by two lower limits and/or two upper limits, corresponding to “low low,” “low”, “high” and “high high” values. This allows the system to respond and correct the situation prior to being in regulatory non-compliance. Some hazards may be mitigated by monitoring/controlling several variables that may be used as surrogate parameters. For those cases, the corresponding Critical Control Limits are specified for each variable. Critical Control Limits were only assigned to Critical Control

Points.

4.9. Critical Control Point Monitoring

Monitoring of CCPs includes any checks or systems available to detect hazards or the potential for hazards. This includes continuous monitoring, visual inspection, and periodic sampling. Monitoring can be complemented

by control measures to ensure CCPs stay within the desired limits.

4.10. Procedures for Deviations from Critical Control Points

The DWQMS specifies that each CCP must have one or more documented response procedures to respond to cases when the critical control limits are not met. These procedures should ensure that the adequate response or corrective measures are applied so that the hazard is eliminated, minimizing the risk of the production and/or distribution of unsafe water, and preventing a recurrence from happening.

The procedure should define and describe:

— Who responds

— How is the cause of the critical control limit deviation investigated

— How the hazardous event and hazard are corrected or addressed

— Who the hazard occurrence is reported to

— How it is reported

— How the whole event should be recorded

The procedures developed for each CCP will be consistent with the format specified in Element 5 of the Operational Plan, Document and Records Control.

4.11. Risk Assessment Continuous Improvement

As required by the DWQMS, this risk assessment includes documentation to guarantee that the risk assessment information undergoes regular review and validation. A review of the validity of the risk assessment (including hazards identified, control measures, monitoring procedures, and risk values) is to be conducted for Markham’s water system on a yearly basis. If necessary, new hazards/hazardous events will be added to the original assessment.

The risk assessment will be redone every three years. This re-assessment will include the effects any new regulations that may affect the validity of the assessment, any changes/additions to water sources, any major modifications to the systems water treatment processes, and any other factors that may have arisen since the development of the current risk assessment.

4.12. Risk Assessment Outcomes

The following will be documented within Element 8 of the Operational Plan as per the Document and Records Control procedure:

— Identified potential hazardous events and associated hazards;

— Assessed risks associated with the occurrence of hazardous events;

— Ranked hazardous events;

— Identified control measures to address the potential hazards and hazardous events;

— Identified CCP’s and their respective critical control limits; and

— Procedures and/or processes to monitor, respond to, report and record deviations in the critical control limits.

5.0 Associated SOPs

· SOP – Risk Assessment Procedure

· SOP – Risk Assessment Review Procedure

· SOP – Deviations from Critical Control Limits

6.0 References

· DWQMS Element 7

· Element 8 – Risk Assessment Outcomes

· Element 16 – Sampling, Testing and Monitoring

· Element 17 – Measurement and Recording Equipment Calibration and Maintenance

· Element 18 – Emergency Management

7.0 Records

None applicable. The risk assessment outcomes are documented as part of System Level Document – Element 8.

8.0 History of Changes

Revision

Date

Description

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