In 2007, EPAL – Empresa Portuguesa das Águas Livres, S.A. – started to implement a water safety plan (WSP) in its water supply system, from source to tap, following the international methodologies regarding risk management of water quality. Since the implementation of its first version of the WSP, EPAL has been working on the optimization of its methodology regarding identification and evaluation of hazards/hazardous events and risk assessment. The main objective of this optimization is the prioritization of capital investments and implementation of mitigation actions, within the integrated risk-based management of the company. For this purpose, the initial risk assessment matrixes were optimized with the integration of new specific multicriteria tools to evaluate risks associated with different types of operational assets. The final risk assessment took into account the strategic importance of each individual asset within EPAL's supply system. The new risk assessment methodologies have helped decision-making and prioritization of capital investments and also allowed EPAL to better pinpoint the critical issues to address in its supply system.

INTRODUCTION

In the last decades, the World Health Organization (WHO) has issued a vast number of publications and recommendations regarding water quality and the protection of human health. The WHO publications are directed to the Water Sector stakeholders such as governmental and health authorities, regulators, water companies and consumers' associations, among others.

In 2004, the International Water Association (IWA) published the Bonn Charter for Safe Drinking Water, which along with the WHO Guidelines for Drinking-water Quality (3rd edition), promoted a new perspective in water quality management, replacing the conventional end-line conformity-driven monitoring methodology by the application of the water safety plans (WSP) as ‘The most effective means of consistently ensuring the safety of a drinking-water supply through the use of a comprehensive risk assessment and risk management approach that encompasses all steps in water supply from catchment to consumer’ (WHO 2004; IWA 2004).

The preventive approach recommended by WSP offers unquestionable benefits to water utilities, such as improved regulatory compliance with drinking water quality standards, better general water quality and reduced risk of occurrence of waterborne illnesses and, as such, improves public health (Gunnarsdottir et al. 2012).

The implementation of the WSP is to be adapted to the specific goals/needs of each water company, to the legal/regulator/consumer requirements and several external aspects that are specific to each country such as economic, social and cultural factors. Regarding risk assessment, the usual methodology is to apply qualitative or semi-quantitative matrixes (WHO 2011; Vieira & Morais 2005; Vieira 2011).

EPAL – Empresa Portuguesa das Águas Livres, S.A – is the biggest water company in Portugal and was created in the 19th century (1868). EPAL's mission is to provide water services and sustainable management of the urban water cycle in all its activities and businesses. The company produces and supplies, directly and indirectly, drinking water to 2.9 million inhabitants, approximately 25% of the Portuguese population. EPAL's supply system includes two surface sources, the Rivers Zêzere and Tagus, as well as 20 groundwater sources, which in total produce 224.2 million m3 per year, two conventional water treatment plants (WTP) and 27 chlorination/rechlorination facilities. The system provides bulk supplies to 34 municipalities and direct distribution to the city of Lisbon, corresponding to a total area of 7,090 km2 and has 710 km of trunk mains and over 1,450 km of pipes in the distribution network. The supply system also includes 42 service reservoirs and 41 pumping or booster stations.

In the scope of its activities, EPAL faces several risks. The identification, control and mitigation of these risks are crucial in the pursuit of the strategic objectives of the company: to guarantee the operation of a water supply system compliant with the established quality and quantity requirements (legal and regulatory) and to gain the customers' trust and satisfaction. For this purpose, it is important to guarantee the integrity of the operational assets (water sources, catchment areas, WTP, main trunks, among others) of the company.

In 2007, EPAL developed its first WSP, following the methodologies proposed by the WHO and the IWA. Contemplating its entire supply system from catchment areas to consumers' taps, which was integrated in the risk-based management of the company, the WSP included different approaches to deal with the quality and quantity objectives and its specific risks, as well as the catchment areas/sources used to produce drinking water, WTP, distribution system assets (including trunk mains, service reservoirs, chlorination units, pumping stations and pipelines/network) and all the internal or domestic plumbing to the final tap or point of use. The WSP's output was the thorough identification and evaluation of hazards, hazardous events and risk assessment of the supply system of EPAL. The WSP also allowed the identification and prioritization of control actions and short- to long-term capital investments needed.

In 2013, during one of the periodic revisions of the WSP, EPAL decided to reformulate or optimize the risk assessment methodology to incorporate the experience gathered during the first 6 years of its WSP. For this purpose, the initial risk assessment matrices were reformulated (from qualitative or semi-quantitative to quantitative) and optimized with the integration of new specific multicriteria tools to evaluate risks associated with different types of operational assets. The final risk assessment took into account the strategic importance of each individual asset within EPAL's supply system.

METHODOLOGY

The development and implementation of the first WSP in EPAL, as well as the successive revisions accomplished since 2007, followed the step-by-step approach/recommendations announced by WHO and IWA (WHO 2005, 2006, 2009).

Consequently, a qualified multidisciplinary project team was formed, involving all the pertinent operational areas/departments of EPAL namely, production, operations, asset management, investment planning, water quality control and an external advisor (specialist). The project team was coordinated by the Water Quality Control Department of EPAL and reported directly to the Board of Directors.

Although the Portuguese legislation defines that the conception, construction and maintenance of internal plumbing is not the responsibility of the water companies, the regulatory compliance with drinking water quality standards has to be performed at the consumers' taps. Therefore, EPAL decided to extend the scope of its WSP from catchment areas/sources used to produce drinking water, through treatment and distribution to the final tap/point of use.

EPAL's first version of the WSP (2007) had the following objectives: evaluation and prioritization of the risks of EPAL's supply system from the perspectives of water quality (protection of public health and the compliance with legal and EU requirements) and water quantity (supply interruptions and pressure problems). The first approach was soon upgraded to incorporate some physical appearance (turbidity and colour) and organoleptic (taste and odour) characteristics of the drinking water. Consumers are more sensitive to the selected drinking water characteristics as the parameters influence or condition the users taste and acceptance.

Water that is aesthetically unacceptable undermines the confidence of consumers, will lead to complaints and, more importantly, to the use of water from sources that are less safe. The concentration at which constituents are objectionable to consumers is variable and dependent on individual and local factors, including the quality of the water to which the community is accustomed and a variety of social, environmental and cultural considerations (WHO 2011). Hence, since 2010/2011 EPAL's WSP identifies and assesses the risks associated with three distinct perspectives:

  1. Water quality/public health (microbiological, biological, chemical and radiological parameters).

  2. Water quantity (continuity of water service).

  3. Service quality (water pressure, aesthetic/physical/organoleptic parameters).

To support the risk assessment, the project team's first task was to fully describe EPAL's supply system. The thorough description included catchment areas, abstraction sites and sources used to produce drinking water, WTP, distribution system (trunk mains and distribution network) and all the internal plumbing, the tools used to support operation of the system, communication channels, historic data on operation and quality, to mention just a few. The system description further provides sufficient and accurate information to identify where the system was vulnerable to hazardous events, relevant types of hazards, with the identification of the control measures already implemented and evaluation of their effectiveness (Beuken & Pettersson 2009).

For all the hazards identified, EPAL defined operation/business targets and critical limits, control measures in place (and their effectiveness), monitoring measures (what to monitor and when), management procedures (available or required) to demonstrate the company's due diligence in the management of the identified hazards and, most importantly, defined additional corrective actions to be taken. One important aspect that facilitated the process was the extensive previous experience of the company regarding risk assessment in its water system. Some of the referred to experience had already been incorporated in relevant documentation regarding the strategic management of the company (EPAL 2006). In this case, the WSP team main activities were to review or update information by site inspection for auditing and interviewing all pertinent relevant professionals (EPAL 2006; TECHNEAU 2008, 2009).

EPAL's WSP risk assessment was performed taking into account five specific templates, which were used to address the different parts of the supply system: hydrographical basins, source catchment areas, treatment systems, distribution system assets (including trunk mains, service reservoirs, chlorination units, pumping stations and pipelines/network) and internal plumbing systems.

According to its nature, each hazardous event and respective hazard was risk assessed using one of the three 5 × 5 quantitative matrices (likelihood or frequency x consequence or severity) that were adopted since 2010/2011: one matrix related to public health or water quality hazards (occurrence or non-conformant/recommended levels of contaminants in the water), the second related to water quantity (continuity of water service) and a third one related to service quality (water pressure, aesthetic/physical/organoleptic parameters).

The definitions and scores/ratings for likelihood and consequence were established according to WHO/IWA recommendations and the expert judgment of the WSP team and EPAL's professionals (Tables 1,234) (WHO 2011).

Table 1

Definition for likelihood of occurrence

LikelihoodDefinition (number of occurrences per year)Score
Most unlikely <1 
Unlikely [1, 12] 
Probable [12, 52] 
Almost certain [52, 365] 
Certain ≥365 
LikelihoodDefinition (number of occurrences per year)Score
Most unlikely <1 
Unlikely [1, 12] 
Probable [12, 52] 
Almost certain [52, 365] 
Certain ≥365 
Table 2

Definition of consequences regarding public health or water quality hazards (occurrence or non-conformant/recommended levels of contaminants in the water)

ConsequenceDefinition (contaminant(s) potentially found in the water)Score
Wholesome water Ch: Calcium, chlorides, magnesium, sulfates, phosphates, hardness, … 
Perceived unwholesomeness: confidence undermined – sensorial unfit to drink Ch: Boron, barium, iron, manganese, zinc, pH, permanganate index, total organic carbon (TOC), assimilable organic carbon (AOC), … 
Potentially harmful: Possible short/long-term health effects Mb: Pseudomonas aeruginosa,Staphylococcus, viable microorganisms 22 ° and 37 °C 
Ch: Nitrates, nitrites, bromates, bromides, lead, cadmium, nickel, sodium, potassium, fluorides, dissolved hydrocarbons, detergents,… 
Potential illness: chronic/long-term illness; Possible acute illness Mb: Total or faecal coliforms, Legionella spp., Clostridium perfringens, Escherichia coli, Enterococcus 
Ch: Acrylamide, volatile organic compounds (VOC), trihalomethanes (THM), haloacetic acids (HAA), chlorophenols, phenols, polycyclic aromatic hydrocarbons (PAH), pesticides, aluminium, mercury, … 
Illness: Fatal (immediate); Fatal (long-term outcome); Acute illness life threatening for some; Acute illness not life threatening Mb: Aeromonas campylobacter, Cryptosporidium spp., Campylobacter jejuni, E. coli O157:H7, Giardia spp., Helicobacter pylori, Klebsiella spp., Legionella spp., Legionella pneumophila, Mycobacterium avium complex, Salmonella spp., Shigella spp., … 
Ch: Alkylphenol ethoxylates, arsenic, bisphenol A (BPA), cyanides, dioxins, steroid hormones, radioactivity, … 
ConsequenceDefinition (contaminant(s) potentially found in the water)Score
Wholesome water Ch: Calcium, chlorides, magnesium, sulfates, phosphates, hardness, … 
Perceived unwholesomeness: confidence undermined – sensorial unfit to drink Ch: Boron, barium, iron, manganese, zinc, pH, permanganate index, total organic carbon (TOC), assimilable organic carbon (AOC), … 
Potentially harmful: Possible short/long-term health effects Mb: Pseudomonas aeruginosa,Staphylococcus, viable microorganisms 22 ° and 37 °C 
Ch: Nitrates, nitrites, bromates, bromides, lead, cadmium, nickel, sodium, potassium, fluorides, dissolved hydrocarbons, detergents,… 
Potential illness: chronic/long-term illness; Possible acute illness Mb: Total or faecal coliforms, Legionella spp., Clostridium perfringens, Escherichia coli, Enterococcus 
Ch: Acrylamide, volatile organic compounds (VOC), trihalomethanes (THM), haloacetic acids (HAA), chlorophenols, phenols, polycyclic aromatic hydrocarbons (PAH), pesticides, aluminium, mercury, … 
Illness: Fatal (immediate); Fatal (long-term outcome); Acute illness life threatening for some; Acute illness not life threatening Mb: Aeromonas campylobacter, Cryptosporidium spp., Campylobacter jejuni, E. coli O157:H7, Giardia spp., Helicobacter pylori, Klebsiella spp., Legionella spp., Legionella pneumophila, Mycobacterium avium complex, Salmonella spp., Shigella spp., … 
Ch: Alkylphenol ethoxylates, arsenic, bisphenol A (BPA), cyanides, dioxins, steroid hormones, radioactivity, … 

Mb – microbiological contaminants.

Ch – chemical contaminants.

Table 3

Definition of consequences regarding water quantity (continuity of water service)

ConsequenceDefinitionScore
Insignificant Distribution: interruption of customers for a period <6 hours 
WTP: partial (reduction) or total interruption for a period <6 hours 
Minor Distribution: Interruption of customers for a period 6–12 hours 
WTP: partial (reduction) or total interruption for a period 6–12 hours 
Moderate Distribution: Interruption of customers for a period 12–24 hours 
WTP: partial (reduction) or total interruption for a period 12–18 hours 
Major Distribution: interruption on customers for a period 24–48 hours 
WTP: partial (reduction) or total interruption for a period 18–24 hours 
Very severe Distribution: interruption of customers for a period >48 hours 
WTP: partial (reduction) or total interruption for a period >24 hours 
ConsequenceDefinitionScore
Insignificant Distribution: interruption of customers for a period <6 hours 
WTP: partial (reduction) or total interruption for a period <6 hours 
Minor Distribution: Interruption of customers for a period 6–12 hours 
WTP: partial (reduction) or total interruption for a period 6–12 hours 
Moderate Distribution: Interruption of customers for a period 12–24 hours 
WTP: partial (reduction) or total interruption for a period 12–18 hours 
Major Distribution: interruption on customers for a period 24–48 hours 
WTP: partial (reduction) or total interruption for a period 18–24 hours 
Very severe Distribution: interruption of customers for a period >48 hours 
WTP: partial (reduction) or total interruption for a period >24 hours 
Table 4

Definition of consequences regarding service quality (water pressure, aesthetic/physical/organoleptic parameters)

ConsequenceDefinitionScore
Insignificant Minimal aesthetic impact 
Minor Minor or localized pressure/aesthetic problems 
Moderate Pressure/aesthetic problems in a subsystem and/or DMA/DP 
Major Large scale pressure/aesthetic problems in more than one a subsystem and/or DMA/DP 
Very severe Large scale pressure/aesthetic problems generalized to a significant part of the supply system of EPAL 
ConsequenceDefinitionScore
Insignificant Minimal aesthetic impact 
Minor Minor or localized pressure/aesthetic problems 
Moderate Pressure/aesthetic problems in a subsystem and/or DMA/DP 
Major Large scale pressure/aesthetic problems in more than one a subsystem and/or DMA/DP 
Very severe Large scale pressure/aesthetic problems generalized to a significant part of the supply system of EPAL 

DMA – district metered areas.

DP – delivery point to municipalities/water companies (bulk supply).

The listed matrices were applied to the specific templates used in the different parts of the supply system. The final classification of risk in the first versions of the WSP was common to the three matrices used and had three levels: high risk (scores of greater than 10), medium risk (scores between 5 and 9) and low risk (scores of less than 4). This final risk rating was reformulated in 2013's revision of EPAL's WSP to incorporate four levels that differ according to the type of matrix/hazard being dealt with: very high risk, high risk, medium risk and low risk (Table 5).

Table 5

Risk assessment matrix for public health or water quality hazards and for water quantity (continuity of water service) and service quality

 
 

The reformulation/optimization of EPAL's initial risk assessment matrices from qualitative or semi-quantitative to quantitative, resulted in a more tangible (based on facts) evaluation. The risk rating reformulation along with the division of the matrices into three types, according to the hazards (water quality/public health, water quantity and service quality), the specification of different scores for the duration of an interruption of supply according to the part of the supply system where it occurs (production or distribution) and the incorporation of four levels for the final risk rating (specific for the type of matrix/hazard) were the first and simplest new features introduced into the company's WSP risk assessment methodology to help management decisions regarding the prioritization of implementation of mitigation actions and investment. Further improvements made include the following:

  1. Introduction of a relevance factor (Fr) to weigh the initial risk (Ri) of the same hazard/types of hazards between similar parts of the supply system according to importance within the system to determine its final risk (Rf): Rf = Fr × Ri (Table 6). This relevance factor was only used for sources used to produce drinking water (and respective catchment areas) and WTP and only for hazards regarding water quantity and service quality. For example, the risk associated with the loss or restriction of a WTP due to a hazardous event like flooding, is multiplied/weighed according to its specific importance/relevance.

  2. Integration of new specific multicriteria tools in secondary matrices that were used to evaluate the risks of water quality and water quantity associated with the different types of operational assets of EPAL's supply system, according to their types/characteristics. Six new matrices were created for transport water trunk mains, distribution water mains, pumping stations, service reservoirs, chlorination facilities and DMA.

  3. Identification of the specific operational criteria related to likelihood or/and to consequence for each asset was the first challenge in the preparation of the six specific matrices (see examples of criteria in Table 7). The contribution/value of each individual criterion of likelihood and consequence (VLi or VCi) was pondered in the establishment of the overall likelihood and consequences (L and C) of the asset.

  4. Pondering/weighing factor used (PLi and PCi) incorporates the asset's location, prevalence and strategic importance within the supply system. The final risk assessment (Rf) of each type of asset takes into account this multicriteria evaluation: 
    formula
Table 6

Relevance factor used to weigh initial risks found for sources used to produce drinking water and WTP

Part of supply systemTreated volumeCriterion (m3/day)Fr
Sources used to produce drinking water and WTP Qd 0 < Qd ≤ 50,000 0.2 
50,000 < Qd ≤ 75,000 0.4 
75,000 < Qd150,000 0.6 
150,000 < Qd ≤ 300,000 0.8 
Qd > 300,000 1.0 
Part of supply systemTreated volumeCriterion (m3/day)Fr
Sources used to produce drinking water and WTP Qd 0 < Qd ≤ 50,000 0.2 
50,000 < Qd ≤ 75,000 0.4 
75,000 < Qd150,000 0.6 
150,000 < Qd ≤ 300,000 0.8 
Qd > 300,000 1.0 
Table 7

Examples of criteria used in the definition of likelihood and consequences for operational assets

Type of hazardLikelihoodConsequences
Water quality Dosing equipment failures Volume of water treated 
Monitoring equipment failures Redundancy 
Data (historic) on non-conformant results Type of non-conformity 
Data (historic) on quality consumers' complaints % of very sensitive or hypersensitive consumers (e.g. hospitals and schools), … 
Retention time  
Structural conception and design (e.g. water circulation in service reservoirs)  
Type of reservoir settlement, …  
Water quantity Number of failures with impact on assets’ availability Volume of water pumped 
Average age, … Alternative of supply, … 
Both Structural inspection Strategic importance 
Construction anomalies with impact on operation Storage capacity 
Equipment failure/obsolescence Volume of transported water 
Security and vulnerability of asset Volume of water supplied, … 
Type of water flow (free or pressurized)  
Number of bursts or failures/100 km pipes (per year)  
Predominant material, …  
Type of hazardLikelihoodConsequences
Water quality Dosing equipment failures Volume of water treated 
Monitoring equipment failures Redundancy 
Data (historic) on non-conformant results Type of non-conformity 
Data (historic) on quality consumers' complaints % of very sensitive or hypersensitive consumers (e.g. hospitals and schools), … 
Retention time  
Structural conception and design (e.g. water circulation in service reservoirs)  
Type of reservoir settlement, …  
Water quantity Number of failures with impact on assets’ availability Volume of water pumped 
Average age, … Alternative of supply, … 
Both Structural inspection Strategic importance 
Construction anomalies with impact on operation Storage capacity 
Equipment failure/obsolescence Volume of transported water 
Security and vulnerability of asset Volume of water supplied, … 
Type of water flow (free or pressurized)  
Number of bursts or failures/100 km pipes (per year)  
Predominant material, …  

An example of the methodology described above applied to service reservoirs of the distribution system is shown in Tables 8 and 9. In this case criteria such as age, existence/type of coating, storage capacity/volume, average retention time, data (historic) on non-conformant results, structural conception/design (water circulation within service reservoirs) and type of settlement were considered.

Table 8

Secondary multicriteria matrix used to evaluate the risks of water quantity associated with service reservoirs

L or CMetricIndicatorWeighing factorEvaluation criterionValue
Likelihood Structural inspection General state of conservation of the structure 0.80 Very good 
Good 
Reasonable 
Bad 
Very bad 
Security Vulnerability 0.20 Difficult access 
Limited access 
Easy access 
Consequence Relevance Strategic importance and redundancy 0.65 Low or not important 
Important 
Very important 
Crucial 
Autonomy Storage capacity (m30.35 V ≤ 5000 
5,000 < V ≤ 10,000 
10,000 < V ≤ 20,000 
20,000 < V ≤ 50,000 
V > 50,000 
L or CMetricIndicatorWeighing factorEvaluation criterionValue
Likelihood Structural inspection General state of conservation of the structure 0.80 Very good 
Good 
Reasonable 
Bad 
Very bad 
Security Vulnerability 0.20 Difficult access 
Limited access 
Easy access 
Consequence Relevance Strategic importance and redundancy 0.65 Low or not important 
Important 
Very important 
Crucial 
Autonomy Storage capacity (m30.35 V ≤ 5000 
5,000 < V ≤ 10,000 
10,000 < V ≤ 20,000 
20,000 < V ≤ 50,000 
V > 50,000 
Table 9

Secondary multicriteria matrix used to evaluate the risks of water quality associated with service reservoirs

L or CMetricIndicatorWeight or correction factorEvaluation criterionValue
Likelihood Water quality Non-conformant results (events/year) 0.10 0–2 
3–4 
5–7 
8–10 
>10 
Average retention time (h) 0.25 t ≤ 24 
24 < t ≤ 48 
48 < t ≤ 72 
t > 72 
Conception Structural design of the asset 0.20 Full circulation of water 
Acceptable circulation of water 
Reduced circulation of water 
Structural inspection General state of conservation of the structure 0.30 Very good 
Good 
Reasonable 
Bad 
Very bad 
Security Vulnerability 0.10 Difficult access 
Limited access 
Easy access 
Conception Type of settlement 0,05 Buried 
Semi-buried 
Supported 
Elevated 
Consequence Relevance Strategic importance and redundancy 0.60 Low or not important 
Important 
Very important 
Crucial 
Autonomy Storage capacity (m30.20 V ≤ 5,000 
5,000 < V ≤ 10,000 
10,000 < V ≤ 20,000 
20,000 < V ≤ 50,000 
V > 50,000 
Water quality Type of non-conformant results 0.20 According to Table 2  
L or CMetricIndicatorWeight or correction factorEvaluation criterionValue
Likelihood Water quality Non-conformant results (events/year) 0.10 0–2 
3–4 
5–7 
8–10 
>10 
Average retention time (h) 0.25 t ≤ 24 
24 < t ≤ 48 
48 < t ≤ 72 
t > 72 
Conception Structural design of the asset 0.20 Full circulation of water 
Acceptable circulation of water 
Reduced circulation of water 
Structural inspection General state of conservation of the structure 0.30 Very good 
Good 
Reasonable 
Bad 
Very bad 
Security Vulnerability 0.10 Difficult access 
Limited access 
Easy access 
Conception Type of settlement 0,05 Buried 
Semi-buried 
Supported 
Elevated 
Consequence Relevance Strategic importance and redundancy 0.60 Low or not important 
Important 
Very important 
Crucial 
Autonomy Storage capacity (m30.20 V ≤ 5,000 
5,000 < V ≤ 10,000 
10,000 < V ≤ 20,000 
20,000 < V ≤ 50,000 
V > 50,000 
Water quality Type of non-conformant results 0.20 According to Table 2  

After identifying the significant/critical risks (high or very high ranked) for water safety in the supply system, EPAL drew a WSP Improvement/Upgrade Plan (IUP). The IUP document listed and prioritized the improvement/upgrade proposals (short-, medium- or long-term actions or programmes) to deal or mitigate the significant risks, the operational or management areas of the company that ‘own’ relevant responsibility and the target implementation date. The IUP included proposals that varied from the simplest revision of procedures or operational routines (for example, the change of mineral hydraulic oil to a vegetal one, to prevent water contamination in the case of leakage) to very complex upgrades in the systems' controls or major infrastructure changes (for example, the refurbishment of a WTP). The latter were obviously included in the Capital Investment Plan of the company.

The monitoring/follow-up of EPAL's IUP is done periodically (every 6 months) by the company's WSP Manager and the pertinent operational areas (programme owners), to evaluate if the target implementation date was observed and if improvements are effective.

EPAL's WSP is verified periodically by the WSP team and audited by an external auditor, to formally assess if it is working effectively. The assessment is accomplished using the following tools: compliance monitoring programmes, internal and external auditing of operational activities and customer satisfaction enquiries.

Presently, EPAL's WSP is reviewed every 2 years or more frequently (immediately) after significant changes of the conditions previously evaluated (knowledge of a new hazard), in the water supply system, in the staff/organization or after an incident/problem, emergency or near miss in the water supply system. This review of the overall WSP is documented, as documentation is a crucial step in the success of the implementation of the WSP and provides the basis to guarantee an updated assessment.

RESULTS AND DISCUSSION

EPAL identified 599 risks from catchment areas/sources used to produce drinking water to the final consumers' tap: 53.4% related to catchment and treatment, 37.1% in the distribution system (including trunk mains, service reservoirs, chlorination units, pumping stations and pipelines/network) and 9.5% in the internal plumbing (Figure 1).

Figure 1

Risk assessment results of the EPAL supply system.

Figure 1

Risk assessment results of the EPAL supply system.

Regarding the type of risk, the 599 risks identified were divided as: 41% related to water quality or public health issues (e.g. contamination of water sources due to spillage in river basins or terrorist actions, among others), 32% related to water quantity and 27% related with service quality (Figure 2).

Figure 2

Types of risks found in EPAL's supply system.

Figure 2

Types of risks found in EPAL's supply system.

The present IUP identifies 39 programmes/actions, to be developed in the next 3 years, which can be categorized into the following groups: quality studies, elaboration and revision of operational procedures, upgrade or review of emergency and contingency response plans, upgrade of maintenance plans, establishment of protocol/communication with stakeholders, refurbishment of infrastructures, expansion of supply system, training programmes of staff and revision of EPAL's hygiene code.

The reformulation/optimization of EPAL's initial risk assessment methodology, with the incorporation of several new features such as different score scales in the evaluation matrices, the adoption of specific secondary multi-criteria matrices for operational assets of EPAL's supply system and the adoption of relevance/weighing factors according to the asset's location, prevalence and strategic importance within the supply system made the recent assessment more effective and provided a tool of utmost importance to help management decisions regarding the prioritization of implementation of mitigation actions and investment.

CONCLUSIONS

The new risk assessment methodologies adopted by EPAL have allowed a better understanding and focus of the different operational teams on the critical risks and helped decision-making and prioritization of capital investments. The new assessment procedures also allowed EPAL to better pinpoint the critical issues to address in its supply system.

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