A critical review of risk matrices used in water safety planning: improving risk matrix construction.

Risk matrices are used in water safety planning to prioritize improvements to drinking water systems. While water safety plans (WSPs) are promoted globally, no study has evaluated whether risk matrices are comprehensively constructed to accurately assess risk. We used risk matrix criteria adapted from previous risk matrix research to evaluate risk matrices found in twelve templates across global jurisdictions. WSP templates were found using the WSPortal website and definitions of likelihood and impact were extracted from each template to assist in the evaluation of WSP risk matrices. Application of the criteria developed from a detailed mathematical analysis by revealed that 11 of 12 risk matrices evaluated contravene at least one of the risk matrix criteria. Furthermore, definitions of likelihood and impact varied widely across different jurisdictions, due in part to the system specific nature of the WSP methodology. To improve risk matrix construction, we recommend: setting clearer risk level boundary criteria, aligning specific impact category definitions with water system objectives, and selecting specific impact categories as opposed to defining impact in several ways. Finally, we recommend risk matrix construction be reviewed as part of the WSP process to ensure accurate identification of key risks in a water system.

Drinking water quality management progress in Ontario, two decades after Walkerton.

Following the waterborne disease outbreak in Walkerton, Ontario, the province made significant efforts to implement recommendations of the public inquiry that resulted. As Ontario reformed its drinking water sector, other jurisdictions were advancing risk-based quality management frameworks for drinking water, including the World Health Organization (WHO) through its water safety plan (WSP) framework. Two decades after the Walkerton tragedy, this paper seeks to: (i) evaluate alignment of Ontario's Drinking Water Quality Management Standard (DWQMS) with the WSP framework (ii) review readily available data for evidence that Ontario's DWQMS implementation has improved drinking water safety and promoted a preventive approach through risk-based quality management. Our study found strong alignment between the Ontario DWQMS and WSP frameworks, with supporting programmes and risk assessment procedures present. Analysis of available regulatory data revealed abundant reporting of water quality and adverse incidents in municipal water systems. However, performance data were publicly available, the use of percentage scores for water quality testing obscures the details of system performance and water safety. Reports describing the DWQMS plan and audit results were difficult to obtain and not standardized. There is a need to develop mechanisms to ensure continual improvement of the DWQMS.

Comparing quantitative probability of occurrence to a risk matrix approach: A study of chlorine residual data.

Implementation of water safety planning methods globally has focused primarily on developing an evidence base to demonstrate the benefits of the WSP methodology for risk management in water systems. However, little work has been completed to understand the appropriateness of the risk matrix method currently used to capture levels of risk for system-specific hazardous events. This study examines two quantitative risk calculations (probability density functions and event trees) compared to the risk matrix method employed in water safety planning. This analysis was undertaken to understand if the risk matrix provides an accurate estimation of risk in a water system. Two data sets were collected from nine water supply systems, both continuous inline monitoring and grab samples collected in water distribution systems (discrete events) for chlorine residual data. Using quantitative risk calculations, our study found the risk matrix does not accurately estimate risk compared to water quality data from a water system. In thirty-four (77%) of the forty-four possible scenarios investigated, the risk matrix method provided an underestimation or overestimation compared to the probability calculated using water quality data. The probabilities calculated using continuous data and the event tree method provided the closest estimations to the risk matrix, indicating larger data sets with simpler methods may be more likely to match WSP results. The lack of accuracy obtained reveals the need for a re-evaluation of the risk matrix within a water safety plan (WSP), particularly for systems with data available to perform advanced risk analysis. The risk matrix method has been used historically for systems with little data; however, for water systems with advanced water quality monitoring, adding quantitative probability calculations to a water safety plan has the potential to increase accuracy of risk assessment in water safety planning.

Co-development of a risk assessment tool for use in First Nations water supply systems: A key step to water safety plan implementation.

Despite several years of targeted interventions, First Nations drinking water systems in Canada remain under-resourced and require substantial improvements in both infrastructure and management to provide communities with safe drinking water. The purpose of this study was to co-develop a risk assessment process integral to the water safety planning methodology to determine if proactive risk assessment provides a beneficial management tool for First Nations water systems. We co-developed a risk assessment web-application with First Nations stakeholders to identify hazards and assess risk in six Atlantic region First Nations communities. Using this application, we were able to successfully identify high-risk hazards in each community, both risks specific to individual systems, and risks common at a regional level. Through semi-structured interviews we identified the following benefits of a risk assessment web application: increased communication, data ownership and centralized data management. However, challenges remain, including current fragmented governance realities, and liability concerns associated with adopting a new risk management strategy. Successful adoption of proactive risk management strategies in First Nations communities will depend on strong co-development of risk assessment tools, transparent communication between stakeholders and clearly defined data ownership and management practices.

Inorganic contaminants in Canadian First Nation community water systems.

While previous Canadian studies have examined microbiological water quality in First Nations, there is little published information on inorganic contaminants. In Atlantic Canada, the lead, manganese, and arsenic content of First Nations' drinking water has been measured for more than a decade, but the data have not been analyzed comprehensively. These contaminants are linked with health problems, and high levels in drinking water are a cause for concern. We examined 12 years of data from 47 First Nation community water systems to identify systems experiencing difficulties meeting sampling frequency or regulatory guidelines. While most contaminant concentrations were below guideline values, we identified elevated concentrations and issues with sampling frequency. No system met both sampling frequency requirements - a minimum of one sample per year per analyte - and regulatory guidelines. Exceedance rates for lead, manganese, and arsenic were high in some systems. Moreover, current sampling procedures for lead specify that taps be flushed prior to sampling, which is known to underestimate lead exposure. We find that a switch to random daytime sampling would at least sometimes yield higher estimates of lead at the tap. Our analysis demonstrates the need for increased monitoring and updated sampling procedures to better characterize inorganic contaminant occurrence in First Nations.

Water safety plans as a tool for drinking water regulatory frameworks in Arctic communities.

Arctic communities often face drinking water supply challenges that are unique to their location. Consequently, conventional drinking water regulatory strategies often do not meet the needs of these communities. A literature review of Arctic jurisdictions was conducted to evaluate the current water management approaches and how these techniques could be applied to the territory of Nunavut in Canada. The countries included are all members of the Arctic Council and other Canadian jurisdictions considered important to the understanding of water management for Northern Canadian communities. The communities in Nunavut face many challenges in delivering safe water to customers due to remoteness, small community size and therefore staffing constraints, lack of guidelines and monitoring procedures specific to Nunavut, and water treatment and distribution systems that are vastly different than those used in southern communities. Water safety plans were explored as an alternative to water quality regulations as recent case studies have demonstrated the utility of this risk management tool, especially in the context of small communities. Iceland and Alberta both currently have regulated water safety plans (WSPs) and were examined to understand shortcomings and benefits if WSPs were to be applied as a possible strategy in Nunavut. Finally, this study discusses specific considerations that are necessary should a WSP approach be applied in Nunavut.