Water Safety Plans for Utilities in Developing Countries - A case study from Kampala, Uganda
Sam Godfrey, Charles Niwagaba, Guy Howard, Sarah Tibatemwa
1
Acknowledgements
The editor would like to thank the following for their valuable contribution to this publication:
Frank Kizito, Geographical Information Section (GIS), ONDEO Services, Kampala, Uganda
Christopher Kanyesigye, Quality Control Manager National Water and Sewerage (NWSC), Kampala, Uganda
Alex Gisagara, Planning and Capital Development Manager, National Water and Sewerage (NWSC), Kampala, Uganda
Godfrey Arwata, Analyst Microbiology National Water and Sewerage (NWSC), Kampala, Uganda
Maimuna Nalubega, Public Health and Environmental Engineering Laboratory, Department of Civil Engineering, Makerere University, Kampala, Uganda
Rukia Haruna, Public Health and Environmental Engineering Laboratory, Department of Civil Engineering, Makerere University, Kampala, Uganda
Steve Pedley, Robens Centre for Public and Environmental Health, University of Surrey, UK
Kali Johal, Robens Centre for Public and Environmental Health, University of Surrey, UK
Roger Few, Faculty of the Built Environment, South Bank University, London, UK
The photograph on the front cover shows a water supply main crossing a low lying hazardous area in Kampala, Uganda (Source: Sam Godfrey)
2
TABLE OF CONTENTS:
WATER SAFETY PLANS FOR UTILITIES IN DEVELOPING COUNTRIES.1
- A CASE STUDY FROM KAMPALA, UGANDA...... 1 Acknowledgements...... 2 Introduction: ...... 4 Development of Water Safety Plan (WSP): ...... 5 Stages of Implementation...... 7 Stage 1: Forming WSP steering group:...... 7 Stage 2: System description:...... 9 Concepts of Risk Maps...... 12 Hazards...... 13 Vulnerability ...... 13 Susceptibility...... 14 Stage 3 Development of assessment tools:...... 15 Stage 4: System Assessment:...... 17 Stage 5: Development of Risk Maps ...... 19 Hazard Assessment:...... 20 Vulnerability Assessment:...... 23 Vulnerability Maps: ...... 31 Susceptibility...... 34 Key Findings:...... 36 Stage 6: Water Safety Plan ...... 38 Stage 7: Verification exercise (water quality assessment and audit) ...... 44 Results...... 46 Recommendations:...... 49 Future Work...... 52 Bibliography ...... 53
3 Introduction: The most effective way to achieve safety of drinking water is through the adoption of quality assurance schemes that ensure water supplies are designed, operated and maintained properly. The development of quality assurance schemes has been identified by WHO as the principal mechanism for ensuring water safety and refer to these as Water Safety Plans (Davison et al., 2002). A full discussion of the concepts of Water Safety Plans may be found in Davison et al. (2002) and in Howard et al. (2002).
This case study documents the findings of a research project funded by Department for International Development (DFID) undertaken by the Water, Engineering and Development Centre (WEDC) in collaboration with the Uganda National Water and Sewerage Corporation (NWSC) and the Public Health and Environmental Engineering Department of Makerere University. This research project examines the methods and tools required to apply the WSP framework to water utility systems in developing countries. It documents the development of methodologies and tools for a Water Safety Plan developed for a large utility system in Kampala, Uganda. In addition, the case study presents a risk map of the system, which identifies hazardous and vulnerable areas.
The structure of the case study follows the stages of field implementation of a Water Safety Plan and risk mapping. The case study begins with a brief description of the Kampala system and then goes onto describe the key requirements for the successful implementation of a WSP. These requirements include the establishment of a local led steering committee as well as reliable baseline data on both the treatment and distribution network’s performance. The case study then examines the tools and methods required to undertake a comprehensive system assessment. Findings from this assessment and from a comprehensive literature review are then combined to identify control points within the supply. Finally, the case study presents a Water Safety Plan for Kampala, with management actions and monitoring programmes for managing water-related risks.
4 Development of Water Safety Plan (WSP): A Water Safety Plan (WSP) is a management tool designed to optimise performance management of piped water systems. The development of a WSP follows a structured 12-point process as shown in figure 1 below.
Figure 1. Steps in the development of a Water Safety Plan
Water Safety Plan
1 Set Water Quality Objectives
2 System Assessment
3 HACCP Supporting Programmes
1. Assemble team Ensure control measures are managed through supporting programmes: eg 2. Describe water supply Commitment
Training 3. Define intended use
Document control
4. Construct system flow diagram Good design and operation
Calibration of equipment 6.1 Identify Hazards
5. Validate flow diagram 6.2 Prioritise Hazards Community education 6.3 Identify existing control measures Community consultation
6. Conduct hazard analysis
7. Identify control points 7.1 Identify control measures for inclusion as control points 72. Identify control measures as part of supporting programmes 8. Define operational limits programmes
9. Establish monitoring
10. Establish corrective options
11. Establish record keeping
12. Establish validation and verification
5 For distribution systems, the above process can be summarised as being covered by 7 core areas of activity as shown in figure 2.
Figure 2: Development of WSP
Review of existing Forming WSP data / System steering group Description / Zoning
System Assessment Establish Development of / Validation of Vulnerability / tools - Analytical Tools Hazard Matrix & training Map
Development of Verfication and Risk Maps Refinement of WSP
Examples outlined in this document are based on field work undertaken in Kampala, Uganda between January and November 2002. It is important to note that the WSP alone can not ensure the provision of safe drinking water. As well as the WSP, there are two fundamental additions, namely: - Prerequisites - Supporting Programmes
Supporting programmes can be defined as the foundation activities required to ensure safe water (Davison, 2002). Examples include ensuring water treatment works operate at optimum design capacity for water quality control and hygienic working practices, as documented in maintenance Standard Operations Procedures (SOP’s). In Kampala, this of increasing importance due to the increased pollution of the source water in Lake Victoria and particular concerns regarding algal blooms. A supporting programme in this case would be to ensure that the clarification process in the treatment works is able to cope with increased algal loading. This would particularly address design constraints encountered in the mixing channels to ensure more
6 effective floc formation. An upgrade of these clarifiers would then guarantee adequate quality of treated water into the distribution network
Prerequisites can be defined as absolutes required to ensure the successful implementation of the WSP. For example, the success of WSP is dependent on full cooperation and understanding from the senior management. To achieve this in Kampala, senior members from both NWSC and from the system operator, OSUL (Ondeo Services Uganda Ltd) participated in detailed discussions of the WSP and how the WSP could assist NWSC in managing the Kampala system more effectively.
Stages of Implementation There are 7 stages in the development of the WSP. These include selecting a steering group to manage the WSP development process, followed by a review of existing data which can be used to develop appropriate field assessment tools. These tools are then used to undertake a comprehensive system assessment which is then used to develop a Water Safety Plan which forms the basis for the composition of vulnerability and risk maps. The maps form the basis for prioritising control points and requirement for monitoring within the system. Finally, a water quality assessment is performed to verify the Water Safety Plan and to assess whether changes are required to then plan and to provide recommendations for improvement in the operation of the water supply. This section outlines the processes followed in Kampala to achieve these stages.
Stage 1: Forming WSP steering group: A WSP steering group is required to guide the process of implementing a Water Safety Plan. It is recommended that this is composed of members from varied professional backgrounds in order to form a balanced interdisciplinary team. As well as engineers and water quality managers, the steering group may include academics, planners, surveyors, sociologists and health scientists. The balance of varied professionals is important to ensure that the water safety plan incorporates financial, technical and social considerations.
In Kampala, the WSP steering group was formed during initial discussions with the senior management of NWSC. Members of the team were selected on the basis of
7 their professional ability as well as the extent of their involvement in water safety related activities. The majority of the members volunteered to be members of the team during a consultation meeting with the Managing Director of NWSC. These volunteers were from NWSC, OSUL and the Public Health and Environmental Engineering Laboratory of Makerere University.
As NWSC are responsible for water quality, the team was co-ordinated by the NWSC WQCD. The Principal Analyst of NWSC WQCD was proposed as the risk manager. The team was also comprised of three other managers from NWSC, one from OSUL and one from Makerere University. General responsibilities for each of the task force members are outlined in table1. Responsibility in each category is marked as R, with involvement as I and awareness of the activity as A.
Table 1: Roles of the Task Force Members Activity Task Force Members Responsibility
(NWSC/WQCD) Analyst Principal (OSUL) Senior Engineer NWSC development) (planning/capital Chief Engineer University) (Makerere Engineer Environmental Lecturer – (NWSC) Operations Manager- (NWSC/WQCD) Manager Control Quality
Overall Coordination R A A I A A
Coordination at NWSC HQ A A R A I I Coordination of involvement of I I I R I A Makerere staff Technical specifics of system A R R A R A Intellectual Input R R R R R R Progress reporting to top level A A A I A R management Coordinating and institutional A A I A R I field work
In order to clearly define responsibilities between the various stakeholders, an activity – responsibility matrix was drawn up by the WSP steering group. This initially focussed in the identification of the general activities in developing a WSP for the Kampala system (the primary assessments and risk mapping). Within these general activities, specific responsibilities were identified and assigned to individual members of the task force (note column name responsible in table 2).
8
Table 2 outlines the results of this exercise for two key activities in the process of forming the WSP namely the system assessment and the water quality assessment.
Table 2: Activity / Responsibility Matrix Activity/Responsibility Name NWSC Responsible WQCD HQ OSUL MAK WEDC 1. System Assessment Identification and printing of maps Senior Engineer I A R I A Field work Engineers I A I R A Reporting and data analysis Engineers I A I R I Transport arrangements Principal Analyst R A A A I Management of logistics Principal Analyst R A A A I Co-ordination Principal Analyst R A I I I
2. WQ Assessment Laboratory analysis Principal Analyst R A A I I Sampling Principal Analyst R A A I I Transport Principal Analyst R A A A A Co-ordination Principal Analyst R A I I I Report and data analysis Principal R A I I I Analyst/Quality control manager Logistics Principal Analyst R A A I I Training for WQ analysis Consultant I A A I R WQ assessment preparation Consultant I A I I R
It is important to divide responsibilities amongst the stakeholders during the assessment stage. This division must receive full approval from senior managers. This is achieved by ensuring that the core of the WSP steering group are middle and/or senior managers. These staff should have a broad understanding of the use of a WSP as a means of improving water quality in their water supply.
Stage 2: System description: The key to the implementation of a successful WSP is gaining a thorough understanding of the entire water supply system. Therefore, it is essential to undertake a preliminary desk based analysis of the entire distribution network. This is achieved
9 through the composition of a systematic diagram of the system. Figure 3 and 4 below outline both a brief and detailed description of the Kampala system.
Figure 3: Kampala System
Surface water use Abstraction of surface water Treatment
Storage Reservoir Distribution Consumer
Figure 4: Schematic diagram of Kampala system
Source Water taken from Lake Victoria which is prone to high algal loading. Recent observations have noted potential breakthrough of blue green algae
2 coarse screened Intakes located 30m off shore (Gaba 1 and Gaba 2). These serve 2 6-7m deep raw water sumps in two water treatment works located 12km from the city centre
GABA 1( Production of 35,000m3/day) GABA 2 (Production 60,000m3/day) Filtration (Mannesman and Peterson rapid gravity Coagulation/Flocculation/4 flat bottom clarifiers / slow sand filter / Candy pressure filters) - Chlorination filtration / disinfection / pH adjustment
LOW HIGH PRESSURE PRESSURE MAIN MAIN
Gun Hill Service Rubaga Service Mutungo Service Muyenga (5 tanks) Naguru Service Reservoir Reservoir Reservoir Service Reservoir Reservoir
South East amd North East of the Centre of City West of City East of City West, North West City of City
The Kampala system is fed from a surface water source in Lake Victoria. It has two treatment works following conventional treatment unit processes. The combined capacity of the works is 95,000m3/day, which is then distributed to 5 major service reservoirs. There are two distinct pressure zones (high and low) in the supply. The principal service reservoir for the low pressure transmission main is located in the city centre at Gun Hill. There are also two other major areas of low pressure supply located in the East (Mutungo) and West (Rubaga) respectively. The high-pressure transmission mains supplies balancing tanks at Muyenga, South of the City. The
10 Muyenga tanks serve some secondary transmission mains directly and also supplies three other boosters/ tanks located in the North (Kololo), South (Makindye), and North (Naguru) respectively. The entire network covers more than 871 kilometres of pipeline with over 40,000 household connections. Based on previous assessments of numbers of people served with household connections and of water source use by households without a household connection, it is estimated that the network serves 700,000 people.
The WSP steering group undertook an initial analysis of the system with support from NWSC staff. The objective of the system analysis was to identify the major primary and secondary transmission mains in the system. This was done using existing Universal Transverse Mercator (UTM) AutoCAD maps of the distribution system. The Kampala system was mapped in the 1990’s with the assistance of a German surveying agency using traditional cartographic techniques. The city was mapped using aerial photography and information was stored in individual block maps of 0.5km2 that covered the entire Kampala supply. Each of these block maps was geo- referenced using UTM grid references points and a full system map showing the individual blocks prepared. The block maps formed the basis for the development of risk maps for the entire Kampala distribution system.
Using the distribution map as a platform, the WSP steering group, identified the key infrastructural points of the system and defined supply zones. These included the primary trunk mains, the secondary service mains and other major infrastructure with in the system such as;: • Service Reservoirs • Booster Stations • Major Valves
Zoning ensures that at any particular point in the supply, staff know the source of water and the major infrastructure that the water has passed through. Furthermore, zoning of the system enables the operator to estimate the likely impact of a contaminant entering into the system at any given point. Each zone may be used to identify sanitary risks particular to individual sections of supply with the aim of
11 improving the operators ability to manage overall risk. In the Kampala system, a total of six major supply zones were identified based on the service reservoirs. The zones were demarcated on a pipe network map of the system through hydraulic mapping by the operations managers and engineers. During the mapping process, the supply patterns from the two Kampala water treatment works (Gaba 1 and Gaba 2) to the service reservoirs were marked along with connections on the high and low pressure transmissions mains. From each of the supplied service reservoirs water movement was then traced using block maps. Major isolation valves, cut off points or points of potential mixing were marked. The six supply zones are shown on map 4 and are:
1. Gaba low-level
2. Muyenga (five supply tanks serving both service reservoirs and direct connections)
3. Gun Hill (one tank divided into four compartments providing low pressure zone)
4. Naguru (one tank supplied from high pressure zone)
5. Mutungo (one tank supplied from low pressure zone)
6. Rubaga (one tank supplied from low pressure zone)
Within these six zones, there are 22 sub zones each with it’s own discrete area of supply. These are mostly defined by separate booster stations and/or supply tanks. Although these sub zones are important as a tool in the management of individual components of the system, it should be emphasised that the foundation of the system lies in the six main supply zones. From a water quality perspective, it is these six zones which are key to the understanding of contaminant dispersal and movement throughout the system.
Concepts of Risk Maps This section describes the conceptual basis for defining risk within the system. The concept of risk is defined by the hazards and vulnerability associated with the system. In line with definitions of risk outlined in Howard et al. (2002) the approach to controlling water quality in distribution systems should take into account both the vulnerability of the water supply and hazard event scenarios. Therefore:
12 HAZARD + VUNERABILITY = RISK
In addition, the susceptibility of the users (low-income, higher health burdens etc) may magnify the risk, therefore:
IMPACT RATING = RISK + SUSCEPTIBILITY
In order to determine what constitutes these components in Kampala, the WSP steering group undertook a comprehensive analysis of existing data of the system. This included analyses of sanitation/sewer data, topographical data, existing water quality data, pipe specifications and population/socio-economic data. The specific definitions are outlined below:
Hazards
Hazards are specific biological, chemical or physical agents that cause an adverse health effect. However, as noted by Davison et al. (2002) it is easier to consider hazard events rather than individual hazards as this is more useful in identifying management actions.
In the context of water quality control in piped system, hazards may also be defined by hazardous environments in which infrastructure is located (Howard et al., 2002). The definition is dependent on the quantity of hazardous material in the environment (e.g. faecal matter).
Vulnerability
Vulnerability is the susceptibility of infrastructure to a hazard event. This may include vulnerability of the pipe infrastructure to pipe breakage, leakage, intermittence or the physical state of the infrastructure (such as the age, material, diameter and length of the pipe). In Kampala an evaluation of the potential vulnerability of the system was undertaken based on the above. Data was collected from OSUL on both pipeline attributes and from previous research undertaken in Kampala (DFID KAR no. R6874) on historical pipeline failures. For pipeline attribute, data was collected on pipe age,
13 material, diameter and length whilst for pipeline failures data was collected on pipe breakage, leakage and discontinuity. • Pipe Material - vulnerability of different pipe materials to friction, failure and chlorine consumption. • Pipe Length –vulnerability of depending on the number of joins with in pipe • Pipe age –vulnerability dependent on age and material of pipe • Diameter –vulnerability related to increased friction factor (C) dependent on diameter
The two data sets were then divided into two categories: • Variable Vulnerability – monitoring data related to sanitary risks and increased hazardous events. This includes data on pipeline failures. • Static Vulnerability – data on the physical state of the infrastructure and its potential vulnerability to hazard event. This includes pipe attributes.
Initial baseline vulnerability maps were composed to assist in the visual identification of varying areas of vulnerability with in the system. As visual representations are key to gaining a better understanding of risk with in the system, it is recommended that for as many categories as possible these are used.
Susceptibility
The impact rating of the associated risk within the system is defined by the potential susceptibility of the consumer. Susceptibility can be defined as the potential impact on the population from contamination at a giving point of the infrastructure. This is related to a number of factors including socio-economic status of consumer. Socio- economic data is important in terms of the potential ability of a low socio economic group to cope with a hazard event, in particular because the level of service is typically lower. Socio-economic status has been shown to be related to disease burdens in both developed and developing countries (Howard, 2002; Jarman, 1985; Stephens et al., 1997).
14 Stage 3 Development of assessment tools: In addition to estimating the inherent vulnerability of the system, assessment of sanitary risks in the field was undertaken in identified areas of the system. This first involved the development of system specific quantitative tools, including sanitary inspection and water quality testing of selected physio-chemical parameters. Two types of sanitary inspection tools are required in order assess and monitor sanitary risks with in the system. These include: 1. Assessment tools – A set of detailed quantitative tools designed to be used infrequently to assess the sanitary integrity of the system. These tools include water treatment plant audit forms and distribution system sanitary inspection forms. Information from these assessments provides data for the composition and updating of risk maps. 2. Monitoring tools – A set of tools designed to be used on regular basis to monitor the sanitary integrity of specific points with in the system. These tools include sanitary inspection forms specific to individual control points and provide information on the variable vulnerability with in the supply.
Assessment and monitoring tools were developed for the Kampala system. The tools used were based on sanitary inspection (SI) forms developed during research undertaken in Uganda and Ghana (Howard, 2002). Findings from this and previous research stressed the importance of standardisation of SI forms in order to maintain maximum comparability. Both SI assessment and monitoring forms were then developed in consultation with local partners. The appropriateness of the forms for the Kampala system were discussed in great depth. This included the phrasing of the forms, types system specific forms required and use of local terminology.
The forms were then field tested by local partners over a one month period. Proposed improvements to the forms were noted and the forms amended to suit local conditions. Changes made were specific to the Kampala system. For example, Kampala is served by 5 different service reservoirs. In depth field verification of potential sanitary risks in each service reservoir revealed individual design differences between the reservoirs. In order to maintain comparability, sanitary risks common to all the reservoirs were identified. These included the potential contamination of stored water by bird faeces from Maribu stalks defecating on top of the reservoirs. It also
15 included the potential of tree branches to provide a ready access route onto service reservoir roofs and for tree roots to damage the reservoir walls, depending on service reservoir design. From these observations, SI forms were phrased to suit conditions in each service reservoir. For example:
5. Could trees have an impact on the reservoir? Y/N (e.g. tree roots, overhanging branches etc.)
Questions were also phrased to include detail of information from consumers regarding the supply as well as detail on the immediate hazardous environment. For example, at individual standpipes, observations were made as to the state of the environment. Questions related to supply problems were included in order to build up a comprehensive picture of risk associated to that particular inspection point. Once finalised, these forms were used as the basis for undertaking a comprehensive system assessment (see annex 1 for example of a service reservoir form).
As well as SI forms, monitoring of selected physical-chemical parameters was undertaken during the assessment stage. These were: 1. Free residual chlorine – to assess residual disinfectant protections available throughout piped network; 2. Total residual chlorine – to assess whether chlorination at the works had been carried out; 3. pH – to assess whether chlorination had been performed within an acceptable range for effective chlorination (6.8-8); 4. Turbidity – to assess whether there had been ingress, whether there was likely to be an impact on free chlorine residual and aesthetic quality (colour) 5. Temperature – field data from various utilities in the USA, note that water temperature above 150C accelerate the growth of biofilm in pipes (Geldreich, 1996). Results from the system assessment indicated that average temperatures in Kampala were 220C and therefore there is potential for re-growth of biological communities (biofilm).
16 The analyses were performed using field testing equipment. This included a hand held chlorine/pH comparator and a conductivity/turbidity metre. Appropriate training on the use of this equipment was undertaken as part of a field trial prior to undertaking the in depth system assessment.
Stage 4: System Assessment: The aim of the system assessment is to evaluate the sanitary integrity of the entire water distribution network. The assessment is designed to identify inspection points within the distribution system that will provide data to verify the information gained during the initial system description. The information gained on individual inspection points is projected onto stretches of pipe up and down gradient of the inspection points.
Inspection points were identified in the Kampala system by the WSP steering committee. During a participatory discussion facilitated by the risk manager, a number of questions were asked as to what criteria should be used to define the inspection points. The points were identified using the 12 criteria specific to the Kampala system outlined in table 3 below:
Table 3: Inspection Point Selection Criteria Hazard Proximity to physical hazard (sewer, low lying area) Proximity to area of high faecal loading (population density) Historical record of microbial contamination Vulnerability Proximity to primary/secondary infrastructure Pipe Attribute (age/material/length) Pressure/supply zone Proximity to identified vulnerable area Historical record of intermittence in supply Historical record of leakage Evidence of perpetually low residual chlorine levels Susceptibility Potential scale of health impact Number of people effected
Data to fulfil the above criteria was gained from 4 principal sources:
17 • Hazard and vulnerability maps – research undertaken during system description stage assisted in identifying appropriate numbers of inspection points in each area; • Institutional knowledge - known points of vulnerability within the system such as location of exposed pipes, faulty major valves and major connections; • Existing sampling points used by WQCD; and, • Block maps – specific detail of where each point is located.
A total of 152 points were identified throughout the system. Initially, all major primary infrastructure such as service reservoirs and booster pumps/tanks within a given sub zone were identified. From these, secondary infrastructure such as valves, bulk meters, washout valves and points where secondary pipes cross sewers/drainage channels and/or exposed pipes were identified. Using historical records of reported discontinuity, signs of leakage and chlorine residual data, an equal spread of inspection points throughout the system were selected in hazardous areas. The number of inspection points per infrastructure type is outlined in the table 4 below.
Table 4: Number of inspection points per infrastructure type Criteria Number Criteria Number Service Reservoir 5 Bulk Meters 7 Primary valves 23 Booster Pump/Tanks 14 Interconnection valves 8 Channel Crossing/Exposed Pipe 14 Gaba Tanks 3 Washout Valves/Hydrants 11 Standpipe 67 TOTAL 152
Each of the inspection points was then listed according to the sub zone in which it is located. They included 81 in high level pressure zones and 71 in low level pressure zones. This equalled an average of 7 sampling points per sub zone. There were however a greater proportion of inspection points identified in vulnerable zones and/or areas within a known hazardous environment. Each of these inspection points was then located and marked on the UTM system maps. The individual block maps in which the inspection points was located was then printed out and used in the field to guide the assessment team to the exact point with in the system.
18 Each of the 152 inspection points identified was then assessed using sanitary inspection and physio-chemical parameters. Block maps for individual zones were used to identify the location of the points and GPS readings were taken at each inspection point and recorded on the printed field block maps These served as a reference point to be plotted on to the UTM platform to assess risks specific to the identified inspection point. In order to not disrupt the NWSC WQCD schedule, a team of 3 persons worked only 2 days per week over a 7 week period to complete the assessment. Between 10 and 15 inspection points were assessed per day.
Results from the system assessment indicated that the sanitary integrity of valve boxes is of concern. During the first two days of the assessment 5 valve boxes were visited. 4 of these indicated medium sanitary risk and 1 indicated high risk. These valves were vulnerable to contamination as inspection covers were missing and the valve was submerged in stagnant water. Additionally, many of the valve boxes visited were not designed with either a washout facility or an impermeable base.
Furthermore, results indicated that many primary and secondary mains with in the Gun Hill area are located in hazardous environments. Many of the pipes are not secured/protected and cross open trenches in low lying areas (e.g. Nakivubo channel). Additionally, many of these pipes are laid with in 10m of stormwater and sewage pipelines with no evidence of cut off walls to prevent cross contamination.
Additional to the 152 sampling points identified during the desk based exercise, 31 other points were identified taking the total of inspection points up to 183. A full list of these inspection points is outlined in annex 2. Each of these points was then plotted on the UTM platform as an infrastructure type. For example each valve box was coded green, each standpipe as pink etc. The water supply sub zones and block maps were used as a guide in the identification of the exact location of each inspection point (see map 4 for details).
Stage 5: Development of Risk Maps A combination of field data from the system assessment and existing surveillance data was used to compose a risk map of the Kampala distribution network. The maps were
19 composed using a process of risk ranking for each inspection point based on a risk matrix incorporating hazard, vulnerability and susceptibility, as previously described.
The matrix was divided into three categories (hazard/vulnerability/susceptibility) each with a number of sub categories. For each sub category a number of variables were used. Although not listed in the risk matrix, each of these is described in detail in the subsequent sections.
The objective of the risk matrix is to define static risk within the Kampala system based on data collected from both the system assessment and from historical monitoring data. Static risk can be define as the associated vulnerability of the existing infrastructure to hazardous events and in hazardous areas. By using an additive numerical matrices, it is possible to define the static risk associated with specific points with in the Kampala distribution system. This risk assessment tool provides the platform from which risks can then be identified and managed within the system. It is however dynamic and requires updating using variable risk scores on a periodic basis. These variable risks are obtained from regular water quality monitoring and sanitary inspection data. At monthly intervals, monitoring data is fed into the risk matrices to update the static risk matrix.
Hazard Assessment: As noted in earlier sections, the assessment of the hazardous area in which a pipe is located is key to the understanding of relative risk to the pipe of contamination. In order to define the hazardous areas with in Kampala, topographical and sanitation type data was used. These were used to identify: • Sewered zones • Areas with on site sanitation • Low lying areas
These hazards were mapped as a layer within the GIS platform used to display the final risk maps. The definition of this hazardous area falls within two classifications: 1. Hazard Source – use of population density as surrogate for faecal loading 2. Hazard Environment – area of increased potential occurrence of hazard source (e.g. low lying area)
20 Map 2 outlines an example of a layer, which identifies the parishes located within the low lying areas. Low lying areas are perceived as hazardous environments due to the increased probability of cross contamination of water mains from on-site sanitation and/or sewers. Leaching of contaminants from all forms of sanitation into the soil in water logged areas results in a potentially hazardous environment for water mains, as back-siphonage may occur where leaks exist.
Further data was then obtained on sanitation coverage with in the city. This included a map of the sewer network and an estimation of on-site sanitation coverage. It was estimated that sewers posed the highest risk because of the high likelihood of leakage from sewers and because sewers were located closer to the water mains. Within these sewered areas, specific hazardous zones were identified. Hazardous zones were defined as areas in which sewers were laid in close proximity to primary or secondary mains.
Despite the high risk of sewers, only 10% of Kampala’s population has access to sewered sanitation. Classification of sanitation types in non sewered areas of the city were however more difficult to define. For each category a nominal hazard value was assigned. This value reflected the relative hazard associated with each population density category (the higher the population density, the higher the hazard score). Each of the scores refers to a particular parish.
Using the risk maps, the parish in which the inspection point was sited was located. The hazard score for that parish was then used as the score for the inspection point with in the risk matrix. Population figures based on the estimated parish population using figures from the 1991 census and applying a 4.76% growth rate were used to calculate total population per parish. The population density was then calculated by dividing the estimated population of the parish by the area of the given parish in the 1991 census. This population density figure was then used as a surrogate for faecal loading. Categorisation from the census were used to categorise population density into high, medium, low and very low population density (see table below for details). For each parish, population density was plotted onto the GIS platform in vector format (see map 1).
21 Table 5: Population density risk scores Population Density` Category Risk 36992-16364 HIGH 4 15974 - 7833 MEDIUM 3 7689 - 3801 LOW 2 3716-687 VERY LOW 1
Hazardous environments were then identified using the risk maps. The hazardous environment was defined as parishes located in low lying areas.
Parishes with in low lying areas susceptible to water logging were assigned a nominal value of 1 (hazardous area). Parishes outside of the low lying areas were assigned a nominal score of 0 (non hazardous area). These values are based on the perceived likelihood of the occurrence of a hazard event. Inspection points located with in these hazardous areas were then given a hazard scoring with in the risk matrix. For example A standpipe located in the high density parish of Katwe would be given the following hazard score:
Table 6: Hazard Matrix Hazard Hazard Hazard Source Environment Score Sampling Point Parish Population Risk Low Lying Risk Density (Y/N) Standpipe Near Mosque CRN: Katwe HIGH 4 Y 1 5 2317/556
From maps 1 and 2 it was concluded that nine high density parishes were located in low lying areas within the Kampala system. These included parishes located to North West, South West and South East of the city centre. The parishes were Bwaise II and III, Mulago II, Kisenyi I and II, Katwe I and II, Wabigalo and Nakasero III. A map indicating the identified hazard areas with in the Kampala distribution was then composed to assist the risk managers in identifying further potential vulnerable points with in the system. 150mm (1
22 Vulnerability Assessment:
Vulnerability can be defined by a combination of pipe attribute and sanitary risk data. Pipe attributes were identified by plotting the GPS location of the pipe onto the UTM map. Data obtained from OSUL on pipe numbers for each inspection point were then used to marry pipe numbers with inspection points. Referring to operations data on specific pipe details within the system, a breakdown of the pipe attributes was obtained. As there was a lack of initial sanitary risk data from NW&SC, data was used from the urban surveillance project in Uganda in the first instance. This will be subsequently replaced by data collected by NW&SC.
The replacement or updating of this data is most effectively achieved through a visual representation. This assists the operators to understand changes in the vulnerability of the system. An example of this form of representation is outlined in map 3 which illustrates a combination of maps that may be used to identify areas of variable vulnerability with in a supply. Map 3 is based on monitoring data collected from the previous research R6874. The information presented is parish based data which can be represented on a map in an isolated grouping known as a vector. Values for these vectors represent average values assigned to each parish.
The objective of map 3 is to assist the risk assessor in identifying potential areas of vulnerability within the system. This data provides a basis for further in depth assessment of variable vulnerability with in the Kampala supply. As the data is also collected at regular intervals to monitor the performance of the supply, it can be used to update static vulnerability maps
To identify static vulnerability, specific vulnerable points assigned to pipe attributes are required. These will give a basis of the condition of individual sections of the system. In Kampala, static vulnerability was assessed using detailed pipe information obtained from OSUL. Each pipe was assigned a pipe number by OSUL and included information on pipe material, length, age and diameter. From this data it was possible to ascertain specific detail on individual points with in the system. The importance of individual attributes is outlined below.
23 The different variables used to define vulnerability with in the Kampala supply can be broken down as shown in table 7 below:
Table 7: Vulnerability Data Groups Pipe attributes Sanitary risk data Pipe Age Leakage Pipe Material Pipe Breakage Pipe Length Intermittence Pipe Diameter
Outlined in the sections below is a narrative description of the process of risk scoring for each pipe variable.
Pipe Material The system assessment of the Kampala water distribution system, revealed that the system comprises of 6 pipe materials. Each of these pipe materials can be considered a sub variable. They included: 1. PVC 2. Flexible Polyethylene (PE) 3. Asbestos Cement (AC) 4. Steel (ST) 5. Ductile Iron (DI) 6. Galvanised Iron (GI)
In order to define risk associated with each pipe material, an extensive literature review was undertaken. Based on this review, three key sub-variables were defined as important in describing vulnerability: 1. Pipe failure – defined as the susceptibility of a pipe material to pipe failure (i.e. breakage). A review of pipe structural deterioration by Rajani et al. (2001) noted that there are three factors that are related to pipe failure. These are pipe structural properties (material, quality of installation, pipe-soil interaction), internal loads (operational pressure, traffic load) and material deterioration (internal/external biochemical environment). The review by Rajani et al. (2001) concluded that large diameter plastic pipes are more prone
24 to failure than metallic pipes. This conclusion is reflected in table 8 below which ranks a higher value for pipe failure in metallic pipes in the Kampala system(e.g. PE = 6) and a lower value for metallic pipes (e.g. ST). 2. Pipe friction – including the roughness factor within the pipe as defined by the pipes roughness and condition. This is particularly important as a means of defining pipe performance (e.g. high friction rate in AC pipe) and potential of pipe to support biofilm formation (Geldriech, 1996). Research by LeChevalier noted that biofilm developed more quickly on iron pipe surfaces than on plastic pipes due to corrosion and pitting (LeChevallier, 1999). This is of importance as biofilm formation will result in increased chlorine consumption and reduced protection against ingress of pathogens in contaminated water. The findings of this research are reflected in the table below, where low scores (e.g. PVC = 1) are assigned to plastic pipe and high score (e.g. ST = 5). 3. Chlorine consumption – studies by Kiene highlight a difference between chlorine consumption in synthetic material pipes and that in metallic pipes. The study concluded that chlorine consumption in metallic pipes is greater than in synthetic pipes due to excessive chlorine decay in corrosion deposits (Kiene, 1998). High risk scores are therefore assigned to metallic pipes and low scores to plastic pipes.
Nominal values were applied to the risk associated with each of the sub variables. Risk scores were ranked from 1 to 6 with 6 equating to very high risk down to 1 equating to low risk. Based on the evidence presented in the literature, risk scores were assigned to each sub variable. A total vulnerability score was then calculated through an additive process. Risk scores for failure, friction and chlorine consumption were added together to calculated the associated vulnerability of each pipe material. Table 8: Pipe Material Pipe Material Failure Friction Chlorine Consumption Vulnerability PVC 4 1 1 6 Flexible Polyethylene (PE) 6 2 2 10 Asbestos Cement (AC) 2 6 3 11 Ductile Iron (DI) 3 3 5 11 Steel (ST) 1 5 6 12 Galvanised Iron (GI) 5 4 4 13
25 The table concludes that metallic pipes (GI/ST/DI) are more vulnerable than plastic pipes (PVC/PE) to potential failure/breakage and/or chlorine consumption.
Pipe Diameter Research into the relationship between pipe diameter and pipe failure reveals that larger diameter pipes (i.e. trunk mains greater than 300mm) are less prone to failure than smaller diameter pipes. These is due to three reasons: a) Pipe wall thickness increases with pipe diameter. Larger pipes are therefore less susceptible to failure than smaller diameter pipes (Cooper et al. 2000). b) Larger pipes are less susceptible to ground movement from traffic than smaller pipes as they have a greater cementing surface area (Cooper et al. 2000). c) Studies of chlorine decay in pipes notes that chlorine decay profiles are most pronounced in small diameter pipes. This is due to increased absorption of chlorine through contact with biomass. Kiene (1998) estimates that this is most pronounced in pipes with a diameter of less than 75mm.
Table 9: Pipe Diameter Pipe Diameter Vulnerability Score Pipe Diameter Vulnerability Score 50mm 2 300mm 1 65mm 2 350mm 1 80mm 2 400mm 1 100mm 2 450mm 1 125mm 2 500mm 1 150mm 2 600mm 1 200mm 2 700mm 1 250mm 2 800mm 1
Using 300mm as the recognised distinction between primary trunk mains within the NW&SC supply and secondary/tertiary mains, a risk score of 1 is associated with larger diameter pipes and a risk score of 2 is associated with smaller diameter pipes.
26 Pipe Length The vulnerability of a pipe is directly related to its length. Studies reveal two principal reasons for this: a) Pipe stress - Over stressing of pipes is more likely in longer segments of pipe resulting in potential longitudinal breaks (e.g. hoop stress – longitudinal breaks caused by transverse stresses). Studies of vulnerability of varied pipe lengths to failure from earthquake hazards further reinforced that pipe failures increased with pipe length (Ballantyne, 1995). b) Pipe jointing - The number of pipe jointings increases with pipe length. Studies of pipe jointing have identified it as a high risk point for potential contaminant ingress. The materials used to join the water pipes e.g. seal threaded pipe should also be considered as possible sites for microbial colonisation (Geldreich, 1996). The latter would be of concern as this promotes biofilm formation and consequent chlorine consumption.
Based on the literature, a higher vulnerability score is therefore assigned to pipes of a longer length, where pipes of 100 metres are less vulnerable than pipes of 3000m (see table 10 below). Four vulnerability scores have therefore been assigned. A low risk score for pipes with a length less than 100m (score of 1), a medium risk score for pipes between 150 and 750m, a high risk score for pipes between 1000 and 2000m and a high risk score for pipes between 3000 and 4000m.
Table 10: Pipe Length Vulnerability Pipe Length Vulnerability Pipe Vulnerability Pipe Length (m) Score (m) Score Length (m) Score 4000 4 750 2 100 1 3000 4 500 2 50 1 2000 3 350 2 20 1 1500 3 250 2 10 1 1000 3 150 2 5 1
Pipe Age A study by Herz on the relationship between pipe age and pipe failure. recognises that the starting point is an analysis of existing stock of distribution mains (Herz, 1998).
27 The study notes that it is difficult to forecast how long mains will last and that often it is dependent on the pipe material. Reliance must therefore be placed on historical failure records and predicted survival functions of individual sections of pipes (Herz, 1998).
A rehabilitation strategy for the Teplic Water mains in Northern Bohemia by Herz notes that vulnerability associated with pipe age should consider pipe materials, ages, lifetimes under local conditions, frequency of failures (assumed as 0.5 failures per km per year), losses by leakage and extent of rehabilitation work in the past (Herz, 1998). The research indicated that it possible to estimate the survival function of different pipe materials in both the short terms (defined as lower lifetime) and long term (upper lifetime). These periods are dependent on varied pipe materials and change over time. Examples of the Herz model is outlined in the table below:
Table 11: Pipe Age/Material – Short/Long Life Pipe Material Short life (years) Long life (years) Steel 10 40 uPVC 15 50 Polyethylene 20 50 Cast Iron (CI) 30 70 AC 40 70 Others 50 100 Ductile Iron (DI) 60 100
The first step in applying the Herz model to the Kampala system is in the estimation of the percentage lengths of different pipe materials. In Kampala, the network is composed of approximately 60% steel, 20% uPVC, 10% Galvanised Iron and 10% other. The original primary mains were installed between 1930 and 1958 and were made of steel. These were later replaced by Ductile Iron (DI) pipes. The table below outlines the approximate dates associated with different materials and diameters in the Kampala system.
28 Table 12: Pipe Age/Material Kampala Material Diameter Age AC 100 1960 DI 300-800 1958-1996 GI <100 1959- TO DATE PE <100 1929- TO DATE UPVC 50-250 1935 TO DATE Steel (ST) 50-250 1930 TO DATE
A detailed study undertaken in Tronhiem, Norway further ranked pipe failure using predictive statistical models (Lei, 1998). The studies concluded three points: 1. Plastic pipe failure - plastic pipes are the materials most prone to failure (within 5 years). 2. Metallic pipe failure - metallic pipe is prone to failure after approximately 10 years due to increased corrosion and pitting. 3. Lined metallic pipes - lined metallic pipes such as ductile iron have a predicted failure life of 40 years. Using the statistical model as a basis for the research, a generic risk value was approximated for the entire Kampala system. It should be noted that due to limited on site verification of pipe condition, there is substantial room for potential errors. Without digging up every pipe within the system it is difficult to verify vulnerability scores associated with each pipe attribute.
Table 13: Pipe Age Year of Installation Vulnerability 1929-1958 2 1959 – 2002 1 There are a number of additional sub variables such as the relationship between pipe rehabilitation and failure which it is suggested are possible future researchable.
Sanitary inspection data – signs of leakage Data collected by environmental health staff from Kampala City Council was used in the first instance to define the variable vulnerability with in the system. The data collected was entered into the matrix at a parish level to define potential vulnerable
29 points with in the system. The data included records of leakage, pipe breakage and discontinuity. A simple vulnerability scoring was assigned to each of the data sets and then added into the static vulnerability matrix (see below).
Table 14: Leakage Data No of No of No of inspections with inspections with inspections with Vulnerability sign of leakage Vulnerability sign of leakage Vulnerability sign of leakage 15 17 10 11 5 5 14 16 9 10 4 4 13 15 8 9 3 3 12 13 7 8 2 2 11 12 6 7 1 1
Table 15: Community report burst mains Number of inspections with reported mains Vulnerability bursts 4 5 3 4 2 2 1 1
Table 16: Discontinuity Data Recorded Recorded Vulnerability Discontinuity Vulnerability Discontinuity 8 8 4 4 7 7 3 3 6 6 2 2 5 5 1 1
The data above is both relatively old and for leakage is qualitative. The collection of sanitary inspection data in routine monitoring by NW&SC will be used to update the variable vulnerability on a regular basis. It would be preferable to include quantitative estimates of leakage to refine the variable vulnerability component.
30
Vulnerability Scoring To estimate the overall vulnerability for each inspection point with in the supply, it is important to combine all the sub variable within both the pipe attribute risk and the sanitary inspection data to equal a total vulnerability score. This will follow the example outlined in the table below.
Table 17: Vulnerability Matrix Vulnerability Pipe attributes ( PIPE NO: X ) Sanitary inspection data Vulnerability score Inspection point
) mm Material Material Risk Diameter ( Risk (m) Length Risk Age Risk Break Pipe Risk Discontinuity Risk Leakage Risk Valve box (Y) ST 12 100 2 400 2 1960 1 2 2 7 7 13 15 41 (high risk)
This score is used to establish the static vulnerability within the piped network at each inspection point. The values refer to a vulnerability score recorded for a point on a specific pipe and combine both hazard and vulnerability scorings. The piped network is then used to estimate the extent of the effect of the contamination event (in terms of number of pipes effected) of occurring at that point
Vulnerability Maps:
The identified vulnerable areas equate to the total scores assigned within the risk matrix. For each identified inspection point from the system assessment, the following process was undertaken: 1. Plot GPS coordinates on UTM platform as infrastructure types for each inspection point (i.e. as valve box, service reservoir etc) 2. Identify pipe number on which GPS point is located (OSUL classification) on UTM platform 3. Abstract pipe attributes from OSUL data and enter as vulnerability score in risk matrix below 4. Identify parish location for each GPS coordinate and record performance monitoring data, hazard data and susceptibility data for each point. 5. Plot risk scores for each inspection point
31
Table 18 outlines an example of the table used for calculating the risk at each inspection point. The table consists of both hazard and vulnerability scores. Scores from the table are then entered into the GIS platform to estimate areas within the Kampala system that are potentially vulnerable to contamination (see Annex 3 for a complete data set).
32 Table 18: Static Vulnerability Table: HAZARD VULNERABILITY
Hazard Performance Hazard STATIC VULNERABILITY Environ Pipe Attributes Monitoring Source ment Data
Sampling Low LyingArea
Point Pipe Breakage Discontinuity Parish (POP) Diameter Material Leakage Length RIS RISK RISK Category RISK RIS RIS Age Sampling Point K K K
Namirembe Booster Booster Nam 3 N 0 474 2 100 2 ST 12 1970 1 1 6 11 38 (Namirembe Parish) Station irem (Pipe Number 2209) be
Where: > 30 = HIGH RISK, 15-30 = MEDIUM RISK, 0-15 = LOW RISK
33 The objective of mapping vulnerability with in the system is to then ascertain which areas of the Kampala system are at highest risk to contaminant ingress. In order to do this, it is important to understand the hydraulics of the system to ascertain if a contaminant enters the system at point A, how will it travel to then effect point B,C and D. In the Kampala system, the original supply zone maps were used. Inspection points located within each supply zone were identified on the UTM maps. These were then matched to the appropriate supply zones by locating flow patterns with in each supply zone. Risk scores for each point were then added up and divided by the number of points with in the zone to give an average risk score for the supply zone.
To understand the specifics of the system, risk scores for inspection points were computed onto individual pipes within the map. This facilitated the location of high/medium and low risk pipes with in the supply. This was done using the supply zone map 7. On the map major primary and secondary infrastructure was identified. Of particular importance were balancing tanks (direct hydraulic effect) and isolation valves. Risk scores associated to inspection points located on or close to these points were then marked on the map. Severity of the risk score was then only changed once pipes intersected with risk of higher or lower severity down flow of initial risk point. A full breakdown of risks with in the Kampala system can be seen in map 6.
Susceptibility Susceptibility is important in prioritising identified risk areas within the identified risk areas. Where high risk has been identified in a particular area, susceptibility is an essential variable to limit the potential adverse health effects associated with a hazard event. This susceptibility factor plus the associated risk of the system equals an impact rating (i.e. potential impact on population of a contamination event). This is effectively used as an additional tool to assist in planning/scheduling monitoring and assessment activities to improve water safety.
To achieve this, a socio-economic index was developed for Kampala for a surveillance project run with the Ministry of Health. This index used quantitative data on six housing and demographic variables obtained from the 1991 census. It was applied at the parish level, as this was the lowest level of local Government for which data was available. Using the data from the original index, Parishes in Kampala were categorised into the following levels of relative wealth:
34 • Very low-income; • Low-income; • Medium income; and, • High income These categories were then marked on a map to overlain on the piped distribution system. In order to update the index, a rapid field assessment was performed using three selected variables: • Roof material • Wall material • House type The objectives of the field assessment were: 1. To assess whether there had been a change in relative socio-economic status of Parishes in Kampala and to re-classify these accordingly; and, 2. To assess whether any sub-divisions of Parishes was required, as this was not possible using the original data.
Field assessments were undertaken by consultants from South Bank University, UK and Makerere University. The assessment was undertaken in only those Parishes where it was felt that either changes may have occurred since 1991 or that sub-division was considered likely to be important.
An initial set of consultations were held with key professionals in Uganda to gain guidance regarding which Parishes were likely to have seen significant changes and from these consultation 37 Parishes were identified. Parishes selected for inclusion in the field study was based on: • The likely size of the change/divide in terms of perceived degree of change, size of the divided area, and current position of the parish in the existing index; • Number of times the parish was identified; • Cross-checking with map information (e.g. evidence of housing density disparities); and, • Geographical spread of parishes.
35 A final list of 12 Parishes were identified for inclusion in the field assessment. Within each Parish, four linear clusters were selected based on sections of paths or roads that were to be surveyed and clusters selected at random within different cartographic ‘blocks’ shown on the map using a numbered grid overlay and random number tables. In each cluster eight housing units were observed, starting with the third dwelling on one side of the route and continuing at an interval of three dwelling units. In total 32 housing units were observed in each sector, making 96 units in each parish.
Once the data was collected it was incorporated into the original index. It was also analysed by developing a 3-variable-category index from the original data. The field data was then used to re-calculate the 3-variable-category score. For a Parish to be sub-divided or changed, there had to be variation of at least 4.55 in the overall score (this was the equivalent of the numerical span of the 3-variable category).
The field assessment resulted in relatively limited changes with a total of five Parishes showing a change in overall category (two from very low to medium; two from very low to low; and, one from medium to high) and two Parishes showing sub-division. The data from the field assessment were then incorporated into the map on susceptibility on the GIS platform and used to prioritise control measures and control points within the distribution system.
Key Findings: In total 177 inspection points were identified within the Kampala system. Table 19 illustrates a complete breakdown of the results:
Table 19: Inspection Points Inspection Points Quantity Inspection Points Quantity Service Reservoirs 5 Valve Boxes 29 Clear Water Tanks 2 Bulk Metres 7 Supply Tanks 7 Road Crossings 14 Booster Stations 7 Fire Hydrants 11 Standpipes 85
The complete data for the 177 inspection points is outlined in annex 2. Forty five incomplete data sets were removed from the data. From the remaining 132 inspections, qualitative techniques were used to identify the most vulnerable areas.
36
The standpipes present in the 132 data set were then removed leaving a remainder of 82 inspection points. The standpipes were removed primarily because the data could not be projected onto to a longer stretch of pipe (unlike the valves and major infrastructure) because the risks were local in nature. They are primarily used to evaluate whether supply or local risks predominate when contamination is found.
Focus was maintained on the primary and secondary infrastructure. This includes the service reservoirs/supply tanks, major valves and any hydrants/road crossings/bulk metres that occur at vulnerable points on the primary or secondary trunk mains(see table 20 below).
Table 20: Infrastructure Breakdown Primary Infrastructure Secondary Infrastructure Service Reservoirs Supply Tanks Clear Well Tanks Secondary Valves Major Valves Fire hydrants Bulk Metres on primary trunk mains Road Crossings Booster Stations Exposed Pipes
Particular vulnerable points were then identified (see map 6 for details). The inspection points were broken down into high, medium and low vulnerability to help establish static vulnerability within the system.
In the Kampala system, the majority of the supply (79.5%) of the supply was considered having a MEDIUM static vulnerability status. Only 12.3% of the system was considered to have a high static vulnerability status, with only 8.2% constituting a low static vulnerability rating.
Once the general areas of static vulnerability were identified, it is important to identified specific areas. The high vulnerability areas of the Kampala system were: • Service Reservoir – 5 high vulnerable points were identified close to the Mutungo service reservoir. These include the service reservoir, the supply tank and major valves.
37 • Booster – 3 high vulnerable points to the North West of the city including the Namirembe booster were identified. This effected a large area in the parishes of Rubaga/Namirembe, Lungujja and Nakalubye. • End Points – Two valve boxes towards the end point of the system were identified as highly vulnerable to potential contamination. These were to the South West of the city. Interestingly, chlorine residual levels recorded at these points (V1345,V1550) were less than 0.1mg/l. Additionally, a low risk area was identified at the end point of the secondary main in the parish of Busega.
As well as identifying specific areas of the supply that have high static vulnerability, the model provides sound recommendations for prioritising inspection points for monitoring. To achieve an equal spread of these points throughout the system, it is important to understand some common lessons from the results. These include: • The most high vulnerability points in the system were found in medium to high income communities in Kampala. However, in developing the overall risk map, whether these supply pipes serving low-income groups was taken into account when prioritising control points. • There was a direct correlation between high pipe vulnerability and pipe material. Of the highly vulnerable points identified, 100% were metallic pipes of either Steel or Galvanised Iron. There were no highly vulnerable points identified with plastic pipe material connections.
Stage 6: Water Safety Plan Using the data from the previous activities, a Water Safety Plan was developed for the Kampala system. This Water Safety Plan focuses primarily on the treatment works and distribution at present, but will in future be expanded to cover actions within the source water and prevention of re-contamination post-collection from taps. For a detailed discussion of the terminology of the Water Safety Plan, see Davidson et al. (2002) and Howard et al. (2002).
The Water Safety Plan is presented in full in Annex 6 of this report and is broken down into a number of sub-sections, relating to particular supply zones and treatment works in order to be more easily used as a working tool. The Plan identifies a range of hazard events that were identified during the system assessment as likely to occur, for instance the inundation of specific valve boxes by contaminated water. For each hazard event, a concise and clear
38 control measure is defined that when undertaken will prevent the hazard event from occurring.
For each control measure, critical limits have been defined. The critical limits identify both the target level of performance (the performance that should be considered normal working practice) and an action level (a level of degraded performance at which action must be initiated to maintain control). Monitoring parameters and frequency are outlined, as well as who should undertake the monitoring. Monitoring parameters are all simple proxy measures of process control that relate directly to the critical limits and maintenance of control. They do not include microbial testing. Corrective actions are identified for each control measure outlining the actions required to ensure control is maintained once the action level is reached. These are important components of the Water Safety Plan as it ensures that management action plan exists for immediate action. The final component of the Water Safety Plan is the means of verification, which includes microbial indicators plus audits.
Some key hazard events from a water safety plan are shown in figure 5 below, which includes control measures, critical limits, monitoring parameters and verification.
39 Figure 5: Water safety plan extract Hazard event Cause Risk Control Critical limits Monitoring Corrective Verification measure Target Action What When Who action Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection staff inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Ingress of Inundation of inlet Moderate/ Good drainage Valve boxes Cover out of place, Sanitary Monthly Operating Clean valve box E.coli contamination at valve of surface Major in valve box; covered and do signs of water or inspection; staff and replace Faecal streptococci. inlet valve water and covers on valve not have standing material build-up; washout drain cover; clear Bacteriophage box; valve water or organic packing shows tests washout drain; Sanitary inspection packing in good material in base; visible signs of replace packing (WQCD) condition packing does not damage leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Six-monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve Butabika water at the valve drainage; good condition; damage to drains; turbidity, any repairs Bacteriophage (61776, 34495) box structural valve box does signs of damage to chlorine made to drains Sanitary inspection V1487 integrity of box; not require box; valve packing residual and valve box; (WQCD) Block Map 2336 valve packing in repairs; vale leaking replace valve good condition packing does not packing leak Microbial Contaminated Moderate/ Pipes buried at Pipes buried, no Pipes exposed; signs Sanitary See annex 2: Operating Repair leaks, E.coli contamination in water enters For impact depth on sign of leaks of leaks inspection, Primary - staff bury pipes and Faecal streptococci. distribution at through damaged rating see roadside, collars turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 reinforce joints chlorine Secondary - Sanitary inspection residual quarterly (WQCD) Tertiary (sample) Microbial Contaminated Moderate/ Provide support Non-approved Pipes unsupported, Sanitary See annex 2: Operating Provide E.coli contamination in water enters when For impact to pipes at pipe materials; no collars to support inspection, Primary - staff supports to Faecal streptococci. distribution at damaged pipe rating see channel/drain pipes entry into turbidity, monthly pipes, replace Bacteriophage channel/drain inundated by Annex 1 crossings and unsupported channel/drain chlorine Secondary - unapproved Sanitary inspection crossing contaminated use appropriate residual quarterly pipe materials (WQCD) surface water pipe material Tertiary connections (sample) Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to sewers leakage data; monthly plan in place for Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance chlorine Secondary - water supply Sanitary inspection sewer system lies above the map) mains; leak quarterly and sewers Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme
40
The same control measure often applies at several points within the system. Where these are important components of the major infrastructure (and therefore where loss of control would result in very high associated risks) they are defined as control points. In the Kampala Water Safety Plan, a total of 82 control points have been identified including the major primary and secondary infrastructure. Other control measures, particularly those relating to tertiary infrastructure or long stretches of pipe, are not converted into control points. However, this does not imply that these control measures are less important than those at the control points, rather than they cannot be applied to individual points within the system.
A WSP for the water treatment works in Kampala was constructed based on a water treatment audit at the two water treatment works at Gaba I and Gaba II. The audit involved a combination of both visual and physical assessment tools. The development of the audit tools and estimation of operational requirements to meet water quality objectives, an extensive literature review was undertaken. This included a review document of treatment efficiency undertaken as part of the revision of the WHO Guidelines for Drinking-Water Quality and a range of other documents that provided evidence of treatment process efficacy in reducing pathogen concentrations in water. An example of a table outlining the key findings from the literature review is outlined in annex 5.
In addition, the development of the treatment works was undertaken and the flow diagrams of the principal unit processes of treatment in each treatment works was reviewed. Gaba I was built in 1929 with the design capacity output of 72,500m3/day. During the time of the assessment, the plant was producing only 34,500m3/day due to low performance pumping and inefficient filtration systems. Gaba II was built more recently in the early 1990’s and includes an additional unit process of clarification (coagulation/flocculation/settlement). Gaba 2 has a capacity of 60,000m3/day. The clarification process has been included to address an increasing problem of high algal loading in Lake Victoria.
A summary of the Kampala treatment works is outlined in figure 6 below:
42 Figure 6: Water Treatment Unit Processes
GABA 1 GABA 2 Water Treatment Works - Water Treatment Works - Kampala Kampala
Abstraction Abstraction (Raw Water (Raw Water Sump) Sump)
Coagulation/Flocculation Filtration (Rapid sand/pressure filters)
Sedimentation (Up flow clarifiers)
Disinfection
Filtration (Rapid Sand)
Disinfection
The treatment audit involved a complete assessment of each of the unit processes. This involved a combination of techniques: 1. Visual inspection –assessment of treatment processes through interview with the works manager and observation of operational practice; 2. Records – analysis of existing water quality and operational records for both treatment plants; and, 3. Experiments – tracer tests were undertaken to assess retention times in the settlers in order to evaluate whether this met design parameters and to reviews likely efficiency.
43
Results of the audit were documented in the WSP format with the objective to serve as an effective management tool for the treatment plants. A full version of the results from Kampala treatment works is outlined in annex 1.
The Water Safety Plan that has been developed provides a working tool for the WQCD and operations unit in controlling safety. The Water Safety Plan and an associated schedule of monitoring activities and verification activities has been provided to NW&SC and these are now being evaluated.
Stage 7: Verification exercise (water quality assessment and audit) An initial verification exercise was undertake to evaluate whether the Water Safety Plan was appropriate and to also assess the extent to which the supply was compliant with the Water Safety Plan.
The specific objectives of this exercise were to:
1. Assess whether the control measures and critical limits were reliable; 2. Evaluate an initial suite of microbial indicators for use in verification exercises; 3. Undertake an audit of the treatment works; and, 4. Assess the extent to which the system was compliant with the WSP and what areas were indicated as being deficient.
Samples were taken from each unit process in the treatment works, from major control points in the primary and secondary infrastructure and from a sample of points in the tertiary infrastructure.
Of the 82 control points identified in the system description, samples were taken at 50. Primary and secondary infrastructure control points were selected based on the severity of risk associated with a contaminant entering the system at that point. For example, a service reservoir serves the entire zone of the network and therefore the risk associated with the point ranges from major to catastrophic. As contamination is point specific, samples were taken from all the tanks to ensure adequate coverage. For control points in the secondary infrastructure, some were omitted because they were
44 not accessible and some because they lay on the boundary of two supply zones and testing them would have yielded data that was difficult to interpret. For valve boxes without sample taps, samples were taken from the nearest standpipe.
In the tertiary infrastructure, a random selection of points throughout the entire supply system was made. The number selected was based on the recommendations in the 2nd edition of the WHO Guidelines for Drinking-Water Quality of 20 samples for the first 100,000 population and then one additional sample per extra 10,000 population. Based on an estimated user population of 700,000 people, the number of samples required was 80, although a total of 82 samples were finally taken from the tertiary infrastructure. The breakdown of samples taken and inspections performed is shown in table 20 below.
Table 20: Summary of inspections and samples taken Number of inspections Number of samples Inspection point type Treatment works - 66 Service reservoirs 16 23 Valve boxes 34 44 Standpipes 82 103 Total 140 236
The selection of the sampling points in the tertiary infrastructure was carried out using random number tables. Block maps in each zone were numbered and the required number of block maps selected using a random number tables (see example in Annex 4). A full list of the sampling sites is shown in Annex 4. On each day of sampling, samples were taken from the service reservoir supplying the zone as well from the tertiary infrastructure to provide an overall evaluation of the zone.
The breakdown of these points used for sampling in each supply zone is outlined in table 21 below.
45 Table 21: Water Quality Assessment Points Zone Number of Samples Rubaga 25 Muyenga 75 Mutungo 11 Naguru 24 Gun Hill 35 Gaba 2
At each sampling point, a sanitary inspection was performed and analysis of physio- chemical parameters linked to microbial quality (free and total residual chlorine, temperature, pH and turbidity).
In addition, samples were also taken for microbial analysis. Three microbial indicators were selected as being suitable for use in the verification exercise. These were E.coli, faecal streptococci and Sulphite-reducing clostridia/Clostridium perfringens. Samples were taken for analysis of E.coli and faecal streptococci within the treatment works and throughout the distribution systems. Analysis was by membrane filtration in a two-stage process of presumptive and confirmatory testing. Sample for analysing sulphite-reducing clostridia and Clostridium perfringens were taken only at the treatment works to evaluate treatment efficiency. Presumptive tests of sulphite- reducing clostridia were performed followed by confirmatory testing of Clostridium perfringens.
Two samples for microbiological analysis were taken from each sampling point (one for the Makerere laboratory and one for the NWSC laboratory) to allow inter- laboratory comparison in the results. The maximum number of samples that could be collected per day by one field testing team was between 10-15 This was due to the inaccessibility of the points, distance between points and poor roads. Samples were taken to two laboratories in order to allow inter-laboratory comparison
Results The results of the verification are summarised below. However, it should be noted that these are interim results and that a further verification exercise will be needed in the
46 future, both to evaluate the impact of implementing the Water Safety Plan and to further test the verification parameters.
The initial exercise showed that the Kampala system retains some operational and design problems. The level of sanitary risks identified at the service reservoirs was high. The median value was 40% risk, with a range of 10-50% risk. Persistent problems were found with four key risks: • Vents being uncovered • Inspection covers missing or left open • Corrosion inside the tank • Poor security at the service reservoir site
It should be noted that with the exception of the corrosion within the reservoir, the remaining risks are very simple operational issues that should be simple to remediate, but call for greater training and guidance on basic hygiene for the operators. One sample was positive for microbial indicators, although this result was treated as suspicious as the level of free chlorine suggests that the sample may have been contaminated during collection. It should be stressed, however, that the high risk scores provides better overall evidence of weaknesses in ensuring safety and that action should be taken to address the persistent problems with simple operational issues.
The chlorine residuals showed greater variation. The Muyenga balancing tanks generally had adequate free chlorine, but none of the remaining major service reservoirs had at least 0.2mg/l of free chlorine. Although previous analysis has indicated that free chlorine was not strongly associated with control of microbial quality In NW&SC supplies (Howard et al., 2002), the inability to sustain reasonable free chlorine levels within the system suggests that operational improvement may be required. In general total chlorine levels were acceptable, although not in Gun Hill. This suggests that chlorination is not well controlled in Gaba I.
Sanitary inspection of the valve boxes was problematic as many were buried and therefore not accessible for inspection. Of those where an inspection was possible, the
47 median risk was 30%, with a range of 10 –80%. The major problem is with the operational status of the valves (i.e. very easily opened and closed) which create a problem with potential back-siphonage into the valve. No other factors were found persistently, but the data suggests a need to improve maintenance of the valve boxes. Only 3 samples showed the presence of presumptive E.coli, of which 2 provide positive confirmatory tests results and 8 samples showed the presence of presumptive faecal streptococci, of which only 3 were positive on confirmatory tests.
The standpipes generally showed lower sanitary risk, with a median of 13% and a range of 0-50% risk. There were particular persistent problems noted, although surface water collecting around taps was the most commonly reported risk. A total of 10 samples gave a positive result in the test for presumptive E.coli, of which 6 gave positive confirmatory test results, and 12 samples showed a positive result in the presumptive faecal streptococci test of which 7 gave positive confirmatory test results. The number of bacteria isolated were relatively low in all cases and never exceeded 30 cfu/100ml. The data for the standpipes suggests that local level risks are being better managed, but there is a need for user education.
In the treatment plant, the audit indicated a number of operational and design problems. Within the water quality assessment, it became clear that microbial loads in the raw water are relatively low and that in general the treatment works appears to be removing microbes.
It is of concern that in one sample, Clostridium perfringens was isolated from the final water in Gaba II, as this implies operational weakness and potential for breakthrough of protozoa. In tests in the final water for the other microbial indicators, 3 samples were positive for presumptive E.coli, of which 2 showed positive in confirmatory tests and 8 samples were positive for presumptive faecal streptococcus, of which 5 showed positive in confirmatory tests. This again illustrates concern that the treatment works are failing to produce water of adequate quality relatively frequently.
The microbial indicators selected all appeared to work effectively and could be recommended for use, although the levels of positive confirmatory tests for both E.coli and faecal streptococci (62.5% and 53.7% respectively) is relatively low.
48 Although presumptive faecal streptococci are isolated more commonly than E.coli the rate of confirmation is lower suggesting that they are perhaps less reliable. However, this may also be due to unfamiliarity of the analysts with the technique and this requires further evaluation in the next stages of the study. In addition, further assessment is required of an indicator for viral pathogens.
An important lesson learnt from the Kampala assessment was that the WQCD were not familiar all the parts of the distribution system. As a result, a route map was composed based on block map numbers this assisted in assigning a route to each of the analysis teams. Further support is required to ensure that WQCD staff have a better understanding of the Kampala system.
Recommendations: The findings from the system assessment form the basis for the establishment of a water safety plan for the Kampala system. This plan includes: - Establishment of control measures; - Prioritisation of control points; and, - Appropriate monitoring and verification of performance.
For each part of the system, measures to control safety are defined, as discussed by Davison et al. (2002) and Howard et al. (2002) and outlined in annex 5. Control points are identified during the system assessment and are ranked in order of the risk. The ranking is determined by a combination of two factors: firstly the severity of risk of each inspection point and secondly the associated infrastructure type (i.e. service reservoir, road crossing etc). Through the ranking, 82 inspection points were selected. These points included major primary and secondary infrastructure throughout the system.
An example of a control point is the Mutungo service reservoir. The reservoir was identified as having a high static vulnerability due to potential ingress of contaminants at the outlet valve of the reservoir. During the system assessment, sanitary inspection records noted that the outlet valve was submerged in stagnant water. The outlet valve would therefore become the exact control point. The appropriate control measure
49 would be to install an effective washout drain and to ensure the valve is covered at all times. A full list of control measures are outlined in the WSP’s developed for Kampala in annex 5. The frequency of monitoring for these control points is shown in table 22 below.
Table 22: Prioritisation of Control Points for Monitoring Control Points Frequency Control Points Frequency Service Reservoirs Once per Valve Boxes Once per week week Clear Water Tanks Once per 2 Bulk Metres Once per month weeks Supply Tanks Once per 2 Road Crossings Once per month weeks Booster Stations Once per 2 Fire Hydrants Once per month weeks
A total of 82 control points have been identified for the Kampala distribution system as shown in Annex 3. Monitoring should be performed by the WQCD in collaboration with OSUL. Monitoring will include sanitary inspection and physio-chemical analyses, with less frequent verification using microbial indicators.
Control measures for the tertiary infrastructure are less easy to define as control points, as the number would be extremely large. Therefore, for the tertiary infrastructure the inspection and physio-chemical testing of water from a random selection standpipes is recommended. More targeted monitoring may be achieved by focusing on those standpipes in areas of particularly high risk.
Additional recommendations include the addition of sampling taps at the identified control points. During the system and water quality assessment, it was noted the collection of samples from identified control points was difficult as most valve boxes/service reservoirs were not equipped with appropriate sampling taps. As an alternative water quality samples were therefore taken from the closest standpipe to the control point. In order to assure safety within the system it is recommended that the major control points are equipped with a sampling tap. Additionally, for many of the valve boxes the WQCD were not equipped with a key to the inspection cover making sampling and sanitary inspection difficult. It is recommended that future
50 assessments WQCD are equipped with appropriate tools to inspect and monitor key infrastructure.
In order to link priority areas for monitoring with the risk maps, it is essential that a quantitative leakage detection programme is initiated. Data collection from this exercise will contribute greatly to ensuring a better understanding of vulnerability within the supply. To achieve this, it is recommended that NWSC/OSUL work in collaboration with the WEDC research team to identify potential areas of high leakage using the identified control points within the system as a reference point to minimising the risk of contaminant ingress and severity of impact.
The most important recommendation that arises from the first stage of the research is related to the method and frequency of sampling. It is recommended that in line with the WSP, greater attention is paid to monitoring of surrogate indicators such as chlorine residual and sanitary inspection and less time on end product microbial testing. The assessment/verification programme using microbial indicators should focus on the collection of at least 80 microbiological samples per month as a means of verification of the regular monitoring. This will be a distinct reduction of microbial testing for NWSC from existing 200 samples per month.
It is then recommended that monitoring is increased and undertaken at two levels; firstly by the NWSC WQCD department and secondly by the service reservoir operators. Monitoring using sanitary inspections and selected physical chemical parameters should be undertaken at the following frequency: • Service reservoirs: twice per week • Primary valves and supply tanks: once per week • Secondary valves: once per month • Tertiary: minimum is with all micro samples, preferable double the number
The verification or assessment programme would involve sampling of thermotolerant coliforms with confirmatory testing for Ecoli on positive samples only. By preference about 20 samples should be tested for faecal streptococci in order to establish a correlation between faecal contamination and more robust bacterial strains. It is
51 recommended that the microbiological verification focuses on sampling from the control points identified annex 3. This should include: • All service reservoirs (total 9) • All supply tanks (total 7) • All critical valves (total 6) • 11 secondary valves (each valve to be visited once per quarter on rolling programme) - • 47 samples from tertiary infrastructure (at least 30 should be random) • Plus twice weekly tests at treatment works
Future Work Outlined in this report are the key findings of the first phase of the research. During the second phase, a number of additional areas will be explored. These will include:
Hazardous environment – Initial research has revealed that reliance on hazardous area and hazard events as a measure of hazard is insufficient. In order to encompass a wider array of hazard scenarios, hazard in a risk management context, must be considered in terms of the hazardous environment in which a pipe is located. Building on research findings to date, the second stage of research will focus on the processes that result in a hazard event. These may include: a) Sanitation type - Quantification of hazardous areas through extensive quantitative ground truthing. It is recommended that a survey is designed that would involve the physical counting and type classification of on site sanitation in all parts of the city. b) Soil Corrosivity - Areas with high soil corrosivity should be considered a hazardous environment. A trunk line condition assessment undertaken in the City of Los Angeles, USA revealed that vulnerability of metallic pipes to failure increases in areas that pass through severely corrosive soils (Harasick, 1995).xi Due to the limitations of the scope of this research, this area could not be validated in the field. It is therefore recommended that this is considered as a future researchable.
52 c) Traffic loading – Areas with increased traffic loading should be considered a hazard. These will contribute to increased vulnerability of pipe failure and potential contaminant ingress. To effectively incorporate these hazardous environment ratings into the overall risk matrix, further research is required into estimating the severity of impact of a contamination event. Building research to date, future work will include the development of simplified monitoring schedules that will consider risk not only in terms of risk to physical infrastructure but also in terms of impact rating.
Water treatment plant design – Consideration of water safety should be included in the engineering design of Gaba 3. Consideration should be given to the design of the clarification treatment unit process. Specifically, the design should consider an appropriate design of the mixing channels to reduce algal loading.
Water quality surrogates – Based on the extensive data set made available from the initial research findings, future work will use physical test to establish the correlation between increased temperature and biofilm formation in pipelines.
Bibliography • Ballantyne, D., Dames and Moore., 1995, Relative Earthquake Vulnerability of Water Pipe, Proceedings of the American Water Works Association 1995 Annual Conference, AWWA, Denver, Colorado, USA • Cooper, N.R, Blakey, G., Sherwin C., Ta. T., White, J, T., Woodward, C., 2000 The use of GIS to develop a probability based trunk mains burst risk model, Urban Water 2, pp 97-103 • Davidson, A., Howard, G., Stevens, M., Callan, P., Kirby, R., Deere, D., Bartram, J., 2002, Water Safety Plans, WHO, Geneva • Geldreich, E. E., 1996, Microbial quality of water supply in distribution systems, CRC Press, USA • Harasick, R. F., 1995, Trunk line Condition Assessment Programme, Proceedings of the American Water Works Association 1995 Annual Conference, AWWA, Denver, Colorado, USA • Herz, R, K., 1998 Exploring rehabilitation needs and strategies for water distribution networks, Agua, Vol. 47, No. 6, pp. 275-283 • Howard, G., Vairavamoorthy, K., Godfrey, S., 2002, Improved risk assessment and management in urban piped water supply – Inception report, WEDC, UK • Jarman, B. 1984. Underprivileged areas: validation and distribution of scores. British Medical Journal, 289: 1587-1592.
53 • Kiene, L., Lu, W., Levi, Y., 1998, Relative importance of the phenomena responsible for chlorine decay in drinking water distribution systems, Water Science and Technology, Volume 38, No. 6, pp 216-227 • LeChavallier, M.W., 1999, The case for maintaining a disinfectant residual, American Water Works Association, Vol. 91, Issue 1, pp. 86-94 • Lei, J., Saegrou, S., 1998 Statistical Approaches for Describing Failures and Lifetimes of Water Mains, Water Science and Technology, Volume 38, No 6, pp 209-217 • Rajani, B., Kleiner, Y., 2001, Comprehensive review of structural deterioration of water mains physically based models, Urban Water, Vol. 3, pp 151-164 • Stephens, C, Akerman, M, Avle, S, Maia, P B, Campanario, P, Doe, B and Tetteh, D. 1997. Urban equity and urban health: using existing data to understand inequalities in health and environment in Accra, Ghana and Sao Paulo, Brazil. Environment and Urbanisation, 9(1): 181-202.
54
i Geldreich, E. E., 1996, Microbial quality of water supply in distribution systems, CRC Press, USA ii LeChavallier, M.W., 1999, The case for maintaining a disinfectant residual, American Water Works Association, Vol. 91, Issue 1, pp. 86-94 iii Kiene, L., Lu, W., Levi, Y., 1998, Relative importance of the phenomena responsible for chlorine decay in drinking water distribution systems, Water Science and Technology, Volume 38, No. 6, pp 216-227 iv Cooper, N.R, Blakey, G., Sherwin C., Ta. T., White, J, T., Woodward, C., 2000 The use of GIS to develop a probability based trunk mains burst risk model, Urban Water 2, pp 97-103 v Cooper, N.R, Blakey, G., Sherwin C., Ta. T., White, J, T., Woodward, C., 2000 The use of GIS to develop a probability based trunk mains burst risk model, Urban Water 2, pp 97-103 vi Ballantyne, D., Dames and Moore., 1995, Relative Earthquake Vulnerability of Water Pipe, Proceedings of the American Water Works Association 1995 Annual Conference, AWWA, Denver, Colorado, USA vii Geldreich, E. E., 1996, Microbial quality of water supply in distribution systems, CRC Press, USA viii Herz, R, K., 1998 Exploring rehabilitation needs and strategies for water distribution networks, Agua, Vol. 47, No. 6, pp. 275-283 ix Herz, R, K., 1998 Exploring rehabilitation needs and strategies for water distribution networks, Agua, Vol. 47, No. 6, pp. 275-283 x Herz, R, K., 1998 Exploring rehabilitation needs and strategies for water distribution networks, Agua, Vol. 47, No. 6, pp. 275-283 xi Harasick, R. F., 1995, Trunk line Condition Assessment Programme, Proceedings of the American Water Works Association 1995 Annual Conference, AWWA, Denver, Colorado, USA Davidson, a., Howard, G., Stevens, M., Callan, P., Kirby, R., Deere, D., Bartram, J., 2002, Water Safety Plans, WHO, Geneva Rajani, B., Kleiner, Y., 2001, Comprehensive review of structural deterioration of water mains physically based models, Urban Water, Vol. 3, pp 151-164 Lei, J., Saegrou, S, 1998 Statistical Approaches for Describing Failures and Lifetimes of Water Mains, Water Science and Technology, Volume 38, No 6, pp 209-217 Howard, G., Vairavamoorthy, K., Godfrey, S., 2002, Improved risk assessment and management in urban piped water supply – Inception report, WEDC, UK
55 ANNEX 1: SERVICE RESERVOIR SANITARY INSPECTION FORM
1. General information: Zone: Area: 2. Code Number 3. Date of Visit 4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified)
1. Are vents not covered? Y/N (could animals get into the reservoir)
2. Is the inspection cover or concrete around the cover damaged or corroded? Y/N
3. Is the inspection cover not in place when inspected? Y/N
4. Is any observable part of the inside of the tank corroded or damaged? Y/N (including ladders, roof struts, walls etc)
5. Is there evidence of leakage/cracks in the reservoir? Y/N (check the outside of the tank to look for faults)
5. Could trees have an impact on the reservoir? Y/N (e.g. tree roots, overhanging branches etc.)
6. Is there evidence of leakage/cracks in the tank? Y/N (check the outside of the tank for faults)
7. Can run off from stagnant pools enter the reservoir? Y/N (ditches and roof gutters may be faulty or need cleaning)
8. Can stagnant water collect in valve boxes? Y/N (i.e. the base is impermeable and allows water to enter)
9. Are the valve boxes dirty? Y/N
10. Is the fence absent or faulty or site lacking security? Y/N
Risk score: 9-10 = Very high, 7-8 = High, 5-6 = Medium, 0-5 = Low
111 Results and Recommendations: The following important points of risk were noted: (list nos: 1-11) Signature of health inspectors/assistant: Comment:
1. Type of Facility ROAD CROSSINGS / DRAIN AND DITCHES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified) ROAD CROSSING 1. Is there a valve box with in 1m of road crossing? Y/N
2. Is road murram? Y/N
3. Is there evidence of erosion of roadside? Y/N
DRAINS/DITCHES 4. Is there evidence of leakage around pipe? Y/N
5. Does pipe cross open drain/ditch/trench? Y/N
6. Is there evidence of faeces in trench/ditch? Y/N
7. Is there waste material around the pipe? Y/N
8. Is the pipe submerged in stagnant water? Y/N
9. Is the pipe damaged / cracked / leaking? Y/N
Risk score: 8-10 = Very high, 6-8 = High, 4-6 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-10)
Signature of health inspectors/assistant:
Comments
1. Type of Facility VALVE BOXES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified)
1. Is the cover of the box unlocked/open? Y/N
2. Was the cover missing when visited? Y/N
3. Is the valve box cover cracked? Y/N
4. Is the valve corroded? Y/N
5. Is the valve operational? Y/N
6. Does the valve leak? Y/N
7. Is there a lack of backflow preventers installed on supply main? Y/N
8. Are backflow preventers in unclean condition? Y/N
9. Are there any noticeable illegal connections? Y/N
10. Is there stagnant water in washout? Y/N
Risk score: 8-10 = Very high, 6-7 = High, 4-5 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-5)
Signature of health inspectors/assistant:
Comments
1. Type of Facility STANDPIPES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified)
1. Do any standpipes leak? Y/N
2. Does surface water collect around any standpipe? Y/N
3. Is the area 5m uphill from tapstand eroded? Y/N
4. Are pipes exposed close to any tapstand? Y/N
5. Is human excreta on the ground within 10m of any standpipe? Y/N
6. Has there been discontinuity in the last 7 days at any standpipe? Y/N
7. Are there solid waste dumps 10m from tapstands? Y/N
8. Are there stagnant pools of water close to the pipe? Y/N
9. Is the mains pipe exposed with in block map area? Y/N
10. Does main pipe cross a drain/ditch? (if YES go to road crossing SI) Y/N
Risk score: 6-8 = Very high, 4-6 = High, 3-4 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-8)
Signature of health inspectors/assistant:
Comments
MINIMUM CONSTRUCTION STANDARDS FROM OPERATIONS REQUIRED??
1. Type of Facility ROAD CROSSINGS / DRAIN AND DITCHES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified) ROAD CROSSING 1. Is there a valve box with in 1m of road crossing? Y/N
2. Is road murram? Y/N
3. Is there evidence of erosion of roadside? Y/N
DRAINS/DITCHES 4. Is there evidence of leakage around pipe? Y/N
5. Does pipe cross open drain/ditch/trench? Y/N
6. Is there evidence of faeces in trench/ditch? Y/N
7. Is there waste material around the pipe? Y/N
8. Is the pipe submerged in stagnant water? Y/N
9. Is the pipe damaged / cracked / leaking? Y/N
Risk score: 8-10 = Very high, 6-8 = High, 4-6 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-10)
Signature of health inspectors/assistant:
Comments
1. Type of Facility STANDPIPES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified)
1. Do any standpipes leak? Y/N
2. Does surface water collect around any standpipe? Y/N
3. Is the area 5m uphill from tapstand eroded? Y/N
4. Are pipes exposed close to any tapstand? Y/N
5. Is human excreta on the ground within 10m of any standpipe? Y/N
6. Has there been discontinuity in the last 7 days at any standpipe? Y/N
7. Are there solid waste dumps 10m from tapstands? Y/N
8. Are there stagnant pools of water close to the pipe? Y/N
9. Is the mains pipe exposed with in block map area? Y/N
10. Does main pipe cross a drain/ditch? (if YES go to road crossing SI) Y/N
Risk score: 6-8 = Very high, 4-6 = High, 3-4 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-8)
Signature of health inspectors/assistant:
Comments 1. Type of Facility VALVE BOXES
1. General information: Zone: Area:
2. Code Number
3. Date of Visit
4. Water samples taken? Sample Nos
11. Specific Diagnostic Information for Assessment:
No. Risk Sample (Please indicate at which sites the risk was identified)
1. Is the cover of the box unlocked/open? Y/N
2. Was the cover missing when visited? Y/N
3. Is the valve box cover cracked? Y/N
4. Is the valve corroded? Y/N
5. Is the valve operational? Y/N
6. Does the valve leak? Y/N
7. Is there a lack of backflow preventers installed on supply main? Y/N
8. Are backflow preventers in unclean condition? Y/N
9. Are there any noticeable illegal connections? Y/N
10. Is there stagnant water in washout? Y/N
Risk score: 8-10 = Very high, 6-7 = High, 4-5 = Medium, 0-3 = Low
111 Results and Recommendations The following important points of risk were noted: (list nos: 1-5)
Signature of health inspectors/assistant:
Comments
Annex 2: Inspection Points
Number Supply Zone Supplied From Service Res no Sampling Point Station Parish 1 KAWEMPE HL Muyenga 1 Near Kobil Petrol station CRN 0814/23 Kawempe 1 2 Muyenga 1 End Point CRN 0512/41 Mpigi 3 Muyenga 1 Homestead CRN 0915/111 Kawempe 1 4 Muyenga 1 Homestead CRN 1015/117 Kawempe 1 5 Muyenga 1 Off Bombo road, Near Dott services CRN 1213/49 Bwaise 2 6 Muyenga 1 St. Kizito Nursrey & P/School CRN 1316/340 Bwaise 1 7 Muyenga 1 Homestead off Windsor school CRN 1316/22 Bwaise 1 8 Muyenga 1 Near KP paints CRN 1115/259 Kawempe 1 9 Muyenga 1 Dead End, Near Caltex, at Mama Hamuza Beauty Salon CRN 1114/21 Kawempe 1 10 Muyenga 1 Standpipe CRN1314/189 Bwaise 2 11 Muyenga 1 Opposite Kisaasi Rd Block Map 1018 Kankanya 12 Muyenga 1 Homestead CRN 0718/113 Komamboga 13 MAKERERE HL Rubaga via Namirembe 2 Near Nyanza Hostel, on Bombo Rd Block Map 1617 Mulago2 14 Rubaga via Namirembe 2 At University Hall Block Map 1817 Wandegeya 15 Rubaga via Namirembe 2 Wandegeya Market CRN 1917/260 Wandegeya 16 Rubaga via Namirembe 2 Sir Apollo Kagwa Rd Block Map 1916 Kagugube 17 MUTUNGO Mutungo 3 Luzira Market Luzira 18 Mutungo 3 Luzira Alex Residence Luzira 19 Mutungo 3 Luzira near Afroplast/Main prison Luzira 20 Mutungo 3 Mutungo reservoir Luzira 21 Mutungo 3 Kitantale water office Mutungo 22 Mutungo 3 Butabika Sample taken from near standpipe Butabika 23 Mutungo 3 Mutungo reservoir Luzira 24 Mutungo 3 Mutungo tank Mutungo 25 Mutungo 3 Valve box connecting Muyenga mains and Mutungo reservoir Luzira 26 Mutungo 3 Fire hydrant Mutungo 27 Mutungo 3 Valve box in Nakivubo channel Luzira 28 GUN HILL Gun Hill 4 Dewinton Road Car Park and Washing Sample point taken fromnear s Civic Centre 29 Gun Hill 4 Acacia Avenue Stanpipe in Golf Course Kololo 4 30 Gun Hill 4 Sewer line crossing water main Civic Centre 31 Gun Hill 4 Sewer line crossing Nakivubo channel Naka 3 32 Gun Hill 4 Water mains crossing Nakivubo channel Naka 1 33 Gun Hill 4 Nakesero (GUN HILL) - reser oir 1 Naka 1 34 Gun Hill 4 Nakesero (GUN HILL) - reservoir 2 Naka 1 35 Gun Hill 4 Nakesero (GUN HILL) - reservoir B1 Naka 1 36 Gun Hill 4 Standpipe in Kisseka - CAR WASHING BAY Naka 3 37 Gun Hill 4 Valve in Kiseeka - CAR WASHING BAY Old Kla 38 Gun Hill 4 Standpipe in Martin road Nak 4 39 Gun Hill 4 Valve box on sixth street roundabout Ind A 40 Gun Hill 4 Road crossing near sixth street roundabout Ind a 41 Gun Hill 4 Sewer pipe crossing Nakivubo channel Nak 4 42 Gun Hill 4 Shariyaaka Market Nakivubo 43 KASUBI HL Rubaga via Namirembe 2 Kasubi Market Block Map 1814 Kasubi Annex 2: Inspection Points
44 Rubaga via Namirembe 2 Near Cleopatra Beauty Parlour Kawaala TC CRN 1613/78 Kasubi 45 Rubaga via Namirembe 2 Near Kawaala Basooka General works CRN 1914/184 Kasubi 46 Rubaga via Namirembe 2 Near Uganda Aids Commision Secretariat V1210 instead seen Namirembe 47 Rubaga via Namirembe 2 Market near V1210 Block map 2313 Namirembe 48 Rubaga via Namirembe 2 Near Kawaala Police Post Kasubi 49 NAMIREMBE HL Namirembe 5 Namirembe Booster station Block map 2214 Namirembe 50 Namirembe 5 GAPCO filling station, Near NWSC Nakulabye office 2115/83 Bukesa 51 Namirembe 5 Hoima Rd, Near Voluntary Action for Development Block map 2015 Bukesa 52 NAKASERO HL Muyenga 1 Near Police stores, Nakasero Block Map 2019 Nak 2 53 Muyenga 1 Lumumba Avenue-Lumumba lane Junction Block map 2018 Nak 2 54 Muyenga 1 Shimoni Rd, near Junction with Kintu Rd Nak 2 55 KYEBANDO HL Muyenga 1 Mulago Market Mulago 1 56 Muyenga 1 Offices Kanjokya street Kamwokya 1 57 Muyenga 1 Near Mpererwe market CR No. 0718/111 Kanyanya 58 Muyenga 1 Near Junction CR No. 0419/29 Komamboga 59 Muyenga 1 Valves 1428/1429 Kyebando 60 MBUYA HL Mbuya Booster 6 Near by House to V094 Mbuya 61 Mbuya Booster 6 Endpoint, Near MoWHC Premises (2031/88) Mbuya 62 Mbuya Booster 6 Near Mbuya Military barracks Mbuya 63 Mbuya Booster 6 Valves 1052/1053/1054 64 Bwaise 1 LL Gun Hill 4 Bwaise Shell Petrol Station Maerere 3 65 Gun Hill 4 Bwaise - Kalerwe Rd, Near Tipper Association Maerere 3 66 Gun Hill 4 River side Nursrey School, Kalerwe Near Nsooba cahnnel 67 Gun Hill 4 Opposite Kisasi Rd 68 Gun Hill 4 Endpoint, Lukoma Rd Kawempe 1 69 Gun Hill 4 Endpoint, Tula Zone-Kawempe 70 Gun Hill 4 End point, Opposite Maganjo Grain Millers Bwaise 1 71 Gun Hill 4 End point, Tula Rd, Off Mbogo Trading Centre 72 Gun Hill 4 End point, Opp. Kawempe Police station Wandegeya 73 Gun Hill 4 Bwaise, Behind Katumba Furniture Kyebando 74 Gun Hill 4 Endpoint, Caltex-Opp. PMK Kanyanya centre 75 Gun Hill 4 Katanga, opp. New Valley Motors Wandegeya 76 Gun Hill 4 Katanga, near a spring below Girls' Hostel Wandegeya 77 Gun Hill 4 Nkizi Rd, at Junction to Bombo Rd Wandegeya 78 Bwaise 2 LL Gun Hill 4 Near Bwaise Parents' school Kasubi 79 Gun Hill 4 Kawala, after Kawala Parents' School Bwaise 3 80 Gun Hill 4 Rd to Namungona H/School Kasubi 81 Gun Hill 4 Sentema Rd Lubya 82 KATWE Gun Hill 4 Katwe, Near Mosque CRN: 2317/556 Kisenyi 1 83 Gun Hill 4 Katwe CRN: 2317/556 Kisenyi 2 84 Gun Hill 4 Masaka RD - Wankulukuku RD Junction Rubaga 85 Gun Hill 4 Road Crossing near Police BM 2912 Kabawo 86 Gun Hill 4 Welaga Rd CRN 2915/68 Najj 2 87 Gun Hill 4 Katwe, off Suna Rd CRN: 2816/46 Mengo 88 Gun Hill 4 Katwe, NWSC Sampling Pt CRN: 2715/272 Ndeeba Annex 2: Inspection Points
89 Gun Hill 4 Near Police, NWSC Sampling Pt CRN: 2912/39 Kabowa 90 Gun Hill 4 Katwe, at the Fire Brigade - OVERFLOW Civic Centre 91 RUBAGA Rubaga 5 V1555 Off Rubaga Rd in BM2316 Mengo 92 Rubaga 5 v1565 off Kivebuli Namirembe 93 Rubaga 5 H709 Rubaga 94 Rubaga 5 V1332 at Rubaga Rd, Kabakanjagala Rd Jn in BM2415 Mengo 95 Rubaga 5 Rubaga Reservoir in BM2512 Rubaga 96 Rubaga 5 V1301 at Kabusu Rd/Nabunya Rd Jn in BM2514 Rubaga 97 Rubaga 5 Near V1565 Off Kivebulaya Rd in BM2414 Rubaga 98 MAKINDYE Muyenga 1 Seguku Booster in BM4013 Mpigi 99 Muyenga 1 Lincholn International School Mpigi 100 Muyenga 1 Lubowa Tank Mpigi 101 Muyenga 1 Near D. K Primary & Secondary School CRN 3418/51 Mpigi 102 Muyenga 1 Namasuba Tank in BM3318 Mpigi 103 Muyenga 1 Busabala/Namasole Rd Jn Najja 1 104 Muyenga 1 Dead end, in a homestead near swamp CRN3417/1 Mpigi 105 Muyenga 1 Off Kivebulaya Rd Namirembe 106 INDUSTRIAL AREA Gun Hill 4 Wampewo Avenue in BM2023 Kololo 4 107 Gun Hill 4 Old Portbell Rd/4th Street Jn in BM2125 Kiswa 108 Gun Hill 4 Bugolobi Market Bugolobi 109 Gun Hill 4 Nakawa Students Hostel, Bugolobi in BM2328 Bugolobi 110 Gun Hill 4 Kulubya Close in BM2328 Bugolobi 111 Gun Hill 4 Luthuli Close, in BM 2430 CRN2430/13 Bugolobi 112 Gun Hill 4 6th Street Ind. Area, Near Sewer Pipeline Ind Area 113 Gun Hill 4 Muhaire Rd Opposite Ebenezer Nursrey & Primary School Kisugu 114 Gun Hill 4 Kironde Rd/Nakibirango Rd Jn in BM2627vConnection of HL with LL Bukasa 115 Gun Hill 4 5th street/Kibira Rd Jn in BM2226 Bugolobi 116 Gun Hill 4 5th street/Kibira Rd Jn in BM2226 Bugolobi 117 Gun Hill 4 At the valves at Wampewo Avenue Kololo 4 118 MUYENGA Muyenga 1 Total Petrol Station, Nsambya BM2520 Nsambya Estate 119 Muyenga 1 Standpipe at CRN2626/95 Bukasa 120 Muyenga 1 Muyenga Reservoir in BM2726 Bukasa 121 Muyenga 1 Muyenga Valve Box in BM2726 Kansanga 122 Muyenga 1 Near Grave Yard, at Proposed Interconnection in BM2829 Bukasa 123 Muyenga 1 Near Poultry Farm in BM3027 Kansanga 124 Muyenga 1 Gaba Water Works Gaba 125 Muyenga 1 Makindye Booster in BM3022 Lukuli 126 Muyenga 1 Makindye Tank in BM3122 Lukuli 127 Muyenga 1 CRN 2620/58 Nsambya 128 Muyenga 1 End point CRN3322/27 Salaama 129 NAJJANANKUMBI Muyenga 1 Masaka Rd - Mutagwanya Rd jn Rubaga 130 Muyenga 1 Mutundwe Hill Rd Mutundwe 131 Muyenga 1 Valve Box Mutundwe 132 Muyenga 1 Valve Box Mutundwe 133 Muyenga 1 CRN3511/5 Mpigi Annex 2: Inspection Points
134 Muyenga 1 CRN 3016/3 Mpigi 135 Muyenga 1 Gwomotoka Rd Rubaga 136 Muyenga 1 BM 2707 Mutundwe 137 Muyenga 1 BM 2707 (near the point above) Mutundwe 138 NAGURU Naguru 6 Jinga Road/lugogo Bypass Nakawa 139 Naguru 6 New Portbell Road Kiswa 140 Naguru 6 NWSC booster Banda 141 Naguru 6 Bulk Meter at Kyambogo Junction Mbuya2 142 Naguru 6 Jinja Rd / Near MOW Mbuya2 143 Naguru 6 CRN 1437/80 n/a 144 Naguru 6 Dead End (CRN 1138/R) n/a 145 Naguru 6 Coca Cola Factory n/a 146 Naguru 6 Nalya Estate n/a 147 Naguru 6 Dead End 1232/09 n/a 148 Naguru 6 Dead End CRN 0923/11 Komamboga 149 Naguru 6 Naguru Reservoir Na 2 150 Naguru 6 Dead End in Naguru Slum Nag1 151 Naguru 6 Valves Near Band Booster Banda 152 Naguru 6 Valve at Coca Cola Factory n/a 153 Naguru 6 V1493 Mbuya2 154 BUSEGA Rubaga 5 Albert Cook/Kalema Rd. Junction Rubaga 155 Rubaga 5 Albert Cook/Kalema Rd. Junction Rubaga 156 Rubaga 5 Nattete Road/Makamba Road Rubaga 157 Rubaga 5 Sekabaka Kintu Road/Sembelu Road Junction Lungujja 158 Rubaga 5 Sekabaka Kintu Road/Mugema Road Junction Busega 159 Rubaga 5 Mubende Road Busega 160 Rubaga 5 Masaka Road at railwat crossing Mpigi 161 Rubaga 5 Dead end, oppositve petro kyengera Mpigi 162 Rubaga 5 Dead end at police post Natete Nateete 163 BUNGA Muyenga 1 Kansanga Water Tank Nsambya Estate 164 Muyenga 1 Gaba Rd near Police post Nsambya Estate 165 Muyenga 1 Gaba Rd near Police post Nsambya Estate 166 Muyenga 1 Gaba Rd near Police post Kansanga 167 Muyenga 1 Bunga booster off Gaba Rd Gaba 168 Muyenga 1 Bunga booster off Gaba Rd Gaba 169 Muyenga 1 End point CRN 3132/07 Gaba 170 Muyenga 1 Gaba market Gaba 171 Muyenga 1 Gaba 1 water treatment plant Gaba 172 Muyenga 1 Near Jnc of Gaba rd Gaba 173 Muyenga 1 Dead end near lake Salanga 174 Muyenga 1 Buziga booster Buziga 175 Muyenga 1 Buziga tank Salanga 176 Muyenga 1 End Point near Lukuli Avenue Mpigi 177 KOLOLO Naguru 6 Kololo Booster, BM1921 Kololo 2 178 Naguru 6 Kololo Tanks, BM1822 Kololo 2 Annex 2: Inspection Points
179 Naguru 6 Kololo High School, Kololo 2 180 Naguru 6 Kitante Hill School Kololo 2 181 Naguru 6 Kaboja Junior School Kololo 2 182 Naguru 6 Swiss House, Kamiti Kagewa close Kololo 2 183 Naguru 6 UEB Quarters, Ridgeway drive Kololo 2 ANNEX 3:Complete Data Set SYSTEM HAZARD PARISH BASED DATRiskA = Population + SocioEcon +Length + Diameter+Mate Population Density Low LyingAnnex: Area Vulnerability Pipe Data No. Lengthset (m) Diameter (mm) Material Year of Installation Pipe Break Discontinuity Leakage Number Sampling Point Station Sampling Point Category Parish HAZARD Parish HAZARD Risk Risk Risk Risk VULNERABILITY 1 NWSC booster Booster St Banda 3 Banda 0 221 1371 3 150 2 ST 12 unknown 0 2 1 4 27 2 Bunga booster off Gaba Rd Booster St Gaba 1 Gaba 1 1167 131 2 400 2 ST 12 1996 1 0 0 0 19 3 Seguku Booster in BM4013 Booster St Mpigi 1 Mpigi 0 1000 3 100 2 ST 12 1996 1 0 0 0 19 4 Makindye Booster in BM3022 Booster St Lukuli 2 Lukuli 0 1467 146 2 100 2 ST 12 unknown 0 0 0 0 18 5 Kololo Booster, BM1921 (36N0054433) Booster St Kololo 2 2 Kololo 2 0 500 2 150 2 ST 12 unknown 0 0 0 0 18 6 Buziga booster Booster St Buziga 1 Buziga 0 1107 40 1 150 2 PVC 6 1996 1 0 0 0 11 7 Namirembe Booster station Block map 2214 Booster St Namirembe 3 Namirembe 0 2209 474 2 100 2 ST 12 1970 1 1 6 11 38 8 At University Hall Block Map 1817 Bulk Meter Wandegeya 4 Wandegeya 1 1792 288 2 100 2 ST 12 unknown 0 0 0 3 24 9 Sir Apollo Kagwa Rd Block Map 1916 Bulk Meter Kagugube 4 Kagugube 0 2237 382 2 100 2 ST 12 unknown 0 0 0 0 20 10 Old Portbell Rd/4th Street Jn in BM2125 Bulk Meter Kiswa 1 Kiswa 0 328 28 1 250 2 ST 12 1963 1 0 0 1 18 11 Bulk Meter at Kyambogo Junction Bulk Meter Mbuya2 2 Mbuya2 0 249 223 2 150 2 ST 12 unknown 0 0 0 0 18 12 Jinja Rd / Near MOW Channel Crossing Mbuya2 2 Mbuya2 0 207 279 2 250 2 ST 12 unknown 0 0 0 0 18 13 Gaba 1 water treatment plant Clear water Tank Gaba 1 Gaba 1 1145 361 2 350 1 ST 12 unknown 0 0 0 6 23 14 Gaba 2 water treatment plant Clear water Tank Gaba 1 Gaba 1 1283 1803 3 800 1 DI 11 unknown 0 0 0 0 17 15 Near Poultry Farm in BM3027 Exposed Pipes Kansanga 2 Kansanga 0 1444 1349 3 350 1 ST 12 unknown 0 0 0 6 24 16 Gaba Rd near Police post Exposed Pipes Nsambya Estate 1 Nsambya Estate 0 1170 1274 3 450 1 ST 12 1959 1 0 0 0 18 17 Kulubya Close in BM2328 Fire Hydrant Bugolobi 2 Bugolobi 0 412 274 2 100 2 ST 12 1960 1 0 0 0 19 18 Mubende Road Fire Hydrant Busega 1 Busega 0 2802 40 1 100 2 PVC 6 1972 1 0 3 7 21 19 Near Police stores, Nakasero Block Map 2019 Fire Hydrant Nak 2 2 Nak 2 0 1573 36 1 50 2 PE 10 unknown 0 5 4 14 38 20 Luzira near Afroplast/Main prison Road Crossing Luzira 2 Luzira 0 1018 387 2 250 2 ST 12 unknown 0 0 4 11 33 21 Acacia Avenue Stanpipe in Golf Course Road Crossing Kololo 4 2 Kololo 4 0 513 332 2 150 2 ST 12 unknown 0 0 0 0 18 22 Sewer line crossing Nakivubo channel Road Crossing Naka 3 3 Naka 3 0 656 193 2 200 2 PVC 6 1958 2 0 0 1 16 23 Water mains crossing Nakivubo channel Road Crossing Naka 1 2 Naka 1 0 713 327 2 200 2 ST 12 1958 2 0 0 8 28 24 Gwomotoka Rd Road Crossing Rubaga 2 Rubaga 1 810 598 2 150 2 ST 12 1964 1 0 0 6 26 25 BM 2707 Road Crossing Mutundwe 1 Mutundwe 0 1514 1144 3 100 2 ST 12 1970 1 1 7 15 42 26 BM 2707 (near the point above) Road Crossing Mutundwe 1 Mutundwe 0 1516 687 2 65 2 ST 12 unknown 0 1 7 15 40 27 Masaka Road at railwat crossing Road Crossing Mpigi 1 Mpigi 0 2801 2376 3 100 2 GI 13 1997 1 0 6 11 37 28 Nakesero (GUN HILL) - reser oir 1 Service Reservoir Naka 1 2 Naka 1 0 94 1488 3 250 2 ST 12 1961 2 1 0 0 22 29 Nakesero (GUN HILL) - reservoir 2 Service Reservoir Naka 1 2 Naka 1 0 402 142 2 100 2 ST 12 1960 0 0 0 0 18 30 Nakesero (GUN HILL) - reservoir B1 Service Reservoir Naka 1 2 Naka 1 0 403 246 2 100 2 ST 12 1960 0 0 0 0 18 31 Mutungo reservoir Service Reservoir Luzira 2 Luzira 0 57 107 2 250 2 ST 12 unknown 0 0 4 11 33 32 Muyenga Reservoir in BM2726 Service Reservoir Bukasa 1 Bukasa 0 1216 342 2 600 1 ST 12 unknown 0 0 3 8 27 33 Naguru Reservoir Service Reservoir Nak 2 2 Nak 2 0 1310 272 2 350 1 ST 12 unknown 0 0 1 4 22 34 Mutungo reservoir Service Reservoir Luzira 2 Luzira 0 166 30 1 80 2 ST 12 unknown 0 0 4 11 32 35 Rubaga Reservoir in BM2512 Service Reservoir Rubaga 2 Rubaga 1 2812 420 2 450 1 ST 12 1997 1 0 1 0 20 36 Mutungo tank Supply Tank Mutungo 2 Mutungo 0 592 124 2 100 2 ST 12 unknown 0 0 2 1 21 37 Lubowa Tank Supply Tank Mpigi 1 Mpigi 0 3627 2000 3 100 2 ST 12 unknown 0 0 1 0 19 38 Namasuba Tank in BM3318 Supply Tank Mpigi 1 Mpigi 0 3626 500 2 200 2 DI 11 unknown 0 0 1 3 20 39 Kololo Supply Tank Supply Tank Nak 4 1 Nak 4 0 2776 817 2 150 2 PVC 6 1997 1 0 0 0 12 40 Kansanga Water Tank Supply Tank Nsambya Estate 1 Nsambya Estate 0 1066 390 2 200 2 ST 12 unknown 0 0 0 0 17 41 Makindye Tank in BM3122 Supply Tank Lukuli 2 Lukuli 0 1472 667 2 50 2 ST 12 unknown 0 0 0 0 18 42 Buziga tank Supply Tank Salanga 1 Salanga 0 1095 1681 3 100 2 ST 12 1970 1 0 0 0 19 43 Valve Box (V1345) Valve Box Mutundwe 1 Mutundwe 0 1519 536 2 100 2 ST 12 1970 1 5 4 14 41 44 Valve Box (V1550) Valve Box Mutundwe 1 Mutundwe 0 1520 593 2 100 2 ST 12 1970 1 1 0 8 27 45 Valves 1428/1429 Valve Box Kyebando 2 Kyebando 0 1990 32 1 100 2 PVC 6 1996 1 0 2 1 15 46 Valve in Kiseeka - CAR WASHING BAY Valve Box Old Kla 3 Old Kla 0 266 398 2 150 2 ST 12 unknown 0 0 0 0 19 47 Butabika Sample taken from near standpipe Valve Box Butabika 1 Butabika 0 1010 118 1 100 2 ST 12 unknown 0 0 0 0 16 48 Valve box connecting Muyenga mains and Mutungo reservoir Valve Box Luzira 2 Luzira 0 2841 1183 3 500 1 ST 12 1993 1 0 0 0 19 49 Valve box on sixth street roundabout Valve Box Industrial Area 1 Industrial Area 0 427 533 2 100 2 PVC 6 unknown 0 0 0 0 11 50 Masaka RD - Wankulukuku RD Junction Valve Box Rubaga 2 Rubaga 1 2126 453 2 300 1 ST 12 unknown 0 0 0 0 18 51 V1493 Valve Box Mbuya2 2 Mbuya2 0 989 330 2 100 2 PVC 6 1996 1 2 1 4 20 52 Valve box in Nakivubo channel Valve Box Luzira 2 Luzira 1 260 109 2 100 2 ST 12 unknown 0 0 4 11 34 53 oima Rd, Near Voluntary Action for Development Block map 201 Valve Box Bukesa 4 Bukesa 0 2204 138 2 80 2 ST 12 1965 1 0 0 0 21 54 Shimoni Rd, near Junction with Kintu Rd Valve Box Nak 2 2 Nak 2 0 575 51 1 150 2 PVC 6 1996 1 5 4 14 35 55 Valves 1052/1053/1054 Valve Box Mbuya 1 Mbuya 0 1331 267 2 80 2 ST 12 1958 0 0 0 0 17 56 V1555 Off Rubaga Rd in BM2316 Valve Box Mengo 4 Mengo 0 1549 207 2 80 2 ST 12 unknown 0 1 2 8 31 57 v1565 off Kivebuli Valve Box Namirembe 3 Namirembe 0 1689 236 2 150 2 ST 12 unknown 0 1 2 8 30 58 H709 Valve BoxRubaga 2 Rubaga 1 1751 274 2 80 2 ST 12 1964 1 0 1 0 21 59 V1332 at Rubaga Rd, Kabakanjagala Rd Jn in BM2415 Valve Box Mengo 4 Mengo 0 2251 471 2 200 2 ST 12 unknown 0 0 1 0 21 60 V1301 at Kabusu Rd/Nabunya Rd Jn in BM2514 Valve Box Rubaga 2 Rubaga 1 2308 525 2 100 2 PVC 6 unknown 0 1 2 8 24 61 Wampewo Avenue in BM2023 Valve Box Kololo 4 2 Kololo 4 0 1896 299 2 150 2 ST 12 unknown 0 2 1 4 25 62 ronde Rd/Nakibirango Rd Jn in BM2627vConnection of HL with Valve Box Bukasa 1 Bukasa 0 85 98 1 150 2 PVC 6 1996 1 1 4 10 26 63 5th street/Kibira Rd Jn in BM2226 VALVE 244 Valve Box Bugolobi 2 Bugolobi 1 429 33 1 150 2 PVC 6 1996 1 0 0 0 13 64 Muyenga Valve Box in BM2726 Valve Box Kansanga 2 Kansanga 1 2104 82 1 50 1 PE 10 unknown 0 0 1 0 16 65 Jinga Road/lugogo Bypass Valve Box Nakawa 3 Nakawa 0 312 612 2 300 1 ST 12 unknown 0 1 7 15 41 66 New Portbell Road Valve Box Kiswa 1 Kiswa 0 343 195 2 150 2 ST 12 unknown 0 0 0 0 17 67 Valves Near Band Booster Valve Box Banda 3 Banda 0 220 95 1 50 1 ST 12 unknown 0 2 1 4 24 68 Valve at Coca Cola Factory Valve Box n/a 0 n/a 0 2878 3288 4 250 2 PVC 6 1997 1 2 1 4 20 69 Albert Cook/Kalema Rd. Junction Valve Box Rubaga 2 Rubaga 1 1742 491 2 50 2 ST 12 unknown 0 0 0 0 19 70 Albert Cook/Kalema Rd. Junction Valve Box Rubaga 2 Rubaga 1 1741 11 1 100 2 ST 12 1964 1 0 0 0 19 71 Nattete Road/Makamba Road Valve Box Rubaga 2 Rubaga 1 1745 725 2 150 2 PVC 6 1972 1 0 0 0 14 72 Sekabaka Kintu Road/Mugema Road Junction Valve Box Busega 1 Busega 0 1717 405 2 150 2 PVC 6 1972 1 0 0 0 12 73 Gaba Rd near Police post Valve Box Nsambya Estate 1 Nsambya Estate 0 1170 1274 3 450 1 ST 12 1959 1 0 0 0 18 74 Gaba Rd near Police post Valve Box Kansanga 2 Kansanga 1 1257 1274 3 400 1 ST 12 1959 1 0 0 0 20 75 Road Crossing near Police BM 2912 Valve Box Kabawo 2 Kabawo 0 2829 1267 3 200 2 PVC 6 1997 1 0 0 0 14 76 5th street/Kibira Rd Jn in BM2226 Valve Box Bugolobi 2 Bugolobi 0 429 33 1 150 2 PVC 6 1996 1 0 0 0 12 77 At the valves at Wampewo Avenue Valve Box Kololo 4 2 Kololo 4 0 1896 678 2 150 2 ST 12 unknown 0 1 7 15 41 78 6th Street Ind. Area, Near Sewer Pipeline (V497) Valve Box Industrial Area 1 Industrial Area 0 427 533 2 100 2 PVC 6 1996 1 1 4 10 27 79 Kasubi Market Block Map 1814 (V1178) Valve Box Kasubi 3 Kasubi 0 2343 194 2 100 2 PVC 6 1972 1 0 0 0 14 80 Masaka Rd - Mutagwanya Rd jn (V1289) Valve Box Rubaga 2 Rubaga 1 2303 601 2 100 2 PVC 6 unknown 0 0 0 0 13 81 Lumumba Avenue-Lumumba lane Junction V811 Valve Box Nak 2 2 Nak 2 0 2365 7 1 100 2 ST 12 1958 2 5 4 14 42 82 Near Kawaala Police Post WASHOUT VALVE Kasubi 3 Kasubi 0 2349 642 2 100 2 PVC 6 1972 1 0 0 0 14 ANNEX 4: SUMMARY OF SAMPLING POINTS FOR WATER QUALITY ASSESSMENT
No Supply Zone Infrastructure Type Block . (Detail) No. GUN HILL
Primary 2 Gun Hill Service Reservoir Service Reservoir 2219 3 Wampewo Avenue/Upper Kololo Valve Box 2023 Avenue V391 V796 V390 4 Masaka/Wankuluku Road V1766 2713 V1765 5 Nakivubo Place V3109 2222 6 6TH Street V497 2225 7 Nakivubo Place V1396 2222 V1397 V1398 8 Nakivubo Place V375 2318 9 Nakibiringo Rd/Kironde Rd V1396 2627 Secondary 10 Acacia Avenue Road Crossing 2020 11 Old Port Bell Road/4th street Bulk metre BM29 2125 12 Kulubya Close Hydrant H127 2328 13 Kibirard junction/5th street Washout Valve V154 2226 14 Wamala Rd/Mutesa 2 Junction Washout Valve V996 2912 Tertiary 15 5th street / Kabira rd 2226 16 Katwe off Suna Rd 2816 17 2717 18 2317 19 2020 20 1919 21 1316 22 2519 23 1921 24 1116 25 2417 26 1317 27 2116 28 2321 29 2816 30 1315 31 2221 32 2428 33 1824 34 2228 35 2329 36 2229 37 2226 38 2127 39 2123 40 1924
No. Supply Zone Infrastructure Type Block (Detail) No. MUYENGA Primary 20 Muyenga reservoir Service Reservoir 2726 21 Kabaka Njagala/Rubaga Rd V1297 2415 23- Rubaga Rd/Hoima Rd V1554/4 2316 26 V1575 2115 V1151 1814
27 Nabunya Rd/Kabuo Rd V1301 2514 28 Bulange Way/Kivebulaya Rd V1564/5 2414 29 Banda Booster V640 1631 30 Near Coca Cola Factory V150 1343 31 Near Main Gate MUK V374 1917 32 Kasubi V199 2016 33 Muyenga Reservoir Valve V438 2726 34 Busabala/Namasole V1347 2917 35 Mutundwe/Klankaluka Junction V1335 3111 36 Mutundwe Road/Wamala Road V1345 3010 Junction 37 ? V811 2018 38 Shimoni Road/Kintu Road V469 2120 Secondary 39 University Hall Bulk Metre BM53 1817 40 Rubaga Cathedral Fire Hydrant H709 2513 41 Sir Apollo Kaggwa Rd BM038 1916 42 Near Police Stores H533 2019 43 Poultry Farm Exposed Pipe 3027 44 Makindye Tank Supply Tank 3122 45 Mbuya Booster V1052 Tertiary (to include) 46 Dead End Standpipe 1930 47 Maganjo Trading Centre 1215 48 Uganda Aids Commission 2313 49 Near Police Stores 2019 50 Lumumba Avenue Junction 2018 51 3020 52 2621 53 2913 54 3316 55 3320 56 3018 57 2728 58 2816 59 3120 60 2518 61 2113 62 2613 63 1715 64 2214 65 2011 66 2216 67 2316 68 1832 69 2032 70 1637 71 1831 72 1434 73 1535 74 1829 75 1438 76 0715 77 0812 78 2809 79 2319 80 3408
No. Supply Zone Infrastructure Type Block (Detail) No. MUTUNGO Primary 2 Mutungo reservoir Service Reservoir 2334 3 Near Butabika Hospital V1487 2336 4 Near Road Crossing V1871 2433 V1872 2433 5 Pipe Interconnection V1888 2631 6 Near HL Junction V095 2130 7 Mutungo Tank Supply Tank 2233 Secondary 8 Near Afroplast/Luzira Prison Road Crossing/Exposed 2634 Pipe Tertiary 9 Luzira Market 2725 10 2532 11 2635 12 2234 13 2835 14 2531 15 2432 16 2131
NAGURU Primary 2 Naguru reservoir Service Reservoir 1524 3 Kyebando Ring Rd V1428 1419 V1429 1419 V1427 4 Lugogo Bypass Rd V378 2025 5 New Portbell road V453 2028 6 Gyanza Rd V928 1617 Secondary 7 Sudan/Egypt Embassy V1053 1621 V1054 V1052 8 ? V1531 1720 Tertiary 9 1318 10 1220 11 1922 12 1020 13 1720 14 1617 15 1119 16 1321 17 2028 18 1427 19 0829 20 1030 21 1726
No. Supply Zone Infrastructure Type Block (Detail) No. RUBAGA Primary 2 Rubaga reservoir Service Reservoir 2512 3 Albert Cook/Kalema Rd V1250 2413 V1248 4 Natete Rd/Makamba Rd V1244 2412 5 Maburero Rd/Mubende V1714 1415 V875 6 Masaka Rd/Matagwanga V1289 2712 7 Klamala Rd/Murtundwe Rd V1345 3010 Secondary 8 Sekabaka Kintu Rd/Mugema Rd Bm 37 2309 Junction 9 Mubende Rd H695 2405 10 MaSAKA Railway crossing Exposed Pipe 2503 11 Ouomotoka Rd Crossing Pipe at road crossing 2712 TERTIARY 12 2212 13 2604 14 2405 15 3114 16 2702 17 1414 18 2504 19 2110 20 2507 21 2706 22 2212 23 1613 24 1514 25 1513 26 2411 27 2009 28 1512 29 2710 30 2207 31 2507 32 2506 33 3115 34 2913 35 2412 36 2312 37 2209 38 2306 39 1809 40 2409 GABA Primary 2711 2 Clear Well Tank Treated water from Gaba 3732 1 3 Near Bunga Booster V187 3127 BM15 BM44 V483 Secondary 4 Kansanga Water tank Supply Tank 2725 5 Busiga Booster Tank Outlet 3327 6 Buzifa Tank Supply Tank 3627 Tertiary 7 Near Jnc of Gaba Rd and Cape Rd 3529 8 Gaba near police 2624 9 3929 10 3230 11 3125 12 3630
ANNEX 5: ESTIMATED LOG REDUCTIONS BY CONVENTIONAL UNIT PROCESSES
Log Reductions using Log Reductions using SSF RSF CONVENTIONAL TREATMENT UNIT PROCESSES Ecoli 0157:H7 = 2.2 Ecoli 0157:H7 = 2.2 Cryptosporidium = 2.2 Cryptosporidium = 2.2 Hepatitis A = 1.5 Hepatitis A = 1.5 Giardia Lamblia = 2.5 Giardia Lamblia = 2.5 SOURCE WATER Ecoli 0157:H7 = 5.5 Ecoli 0157:H7 = 5.5 Shigella = 2 Shigella = 2 ROUGHING FILTER
Ecoli 0157:H7 = 2 Ecoli 0157:H7 = 2 Cryptosporidium = 2 Cryptosporidium = 2 Hepatitis A = 3.4 Hepatitis A = 3.4 FLOCCULATION Shigella = 2 Shigella = 2 COAGULATION Giardia Lamblia = 2 Giardia Lamblia = 2 SEDIMENTATION Ecoli 0157:H7 = 5 Ecoli 0157:H7 = 4.3 Cryptosporidium = 5 Cryptosporidium = 7 Hepatitis A = 5 Hepatitis A = 3.7 Shigella = 2 Shigella = 3.3 RAPID SAND FILTRATION SLOW SAND FILTRATION Giardia Lamblia = 1.7 Giardia Lamblia = 2 Ecoli 0157:H7 = 2 Ecoli 0157:H7 = 2 Cryptosporidium = 2 Cryptosporidium = 2 DISINFECTION DISINFECTION Hepatitis A = 2 Hepatitis A = 2 Shigella = 1 Shigella = 1 (CHLORINATION) (CHLORINATION) Giardia Lamblia = 3.6 Giardia Lamblia = 3.6 ANNEX 6: WATER SAFETY PLANS
Water safety plan for Muyenga service reservoir A,B (with conical vents)
Hazard event Cause Risk Control Critical limits Monitoring Corrective action Verification measure Target Action What When Who Microbial Birds faeces enter Likely/ Vent covers Vents covered 50% of vent Sanitary Weekly Operations Repair and replace E.coli contamination of through vents Catastrophic remain in support struts are inspection staff damaged vents. Faecal streptococci. service reservoir because covers place damaged Sanitary inspection from birds dislodged (WQCD) Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating staff Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection Visible signs of Sanitary Quarterly/ Operating staff Replace damaged Inspection contamination of faeces enter Catastrophic covers and hatches and damage or inspection annually or corroded covers (WQCD) service reservoir through damaged hatches are covers show no corrosion and hatches from birds and or corroded kept in good visible sign of animals inspection hatches condition damage or corrosion Microbial Rodents or Moderate/ Vent covers Vents covered 50% of vent Sanitary Weekly Operations Repair and replace E.coli contamination of amphibians enter Minor remain in support struts are inspection staff damaged vents. Faecal streptococci. service reservoir service reservoir place damaged Sanitary inspection from animals through vents (WQCD) because covers damaged Microbial Contaminated Moderate/ Roof gutters Gutters free of Gutters blocked, Sanitary Quarterly Operations Clear gutters E.coli contamination of water builds up on Major for easy debris start of rainy inspection staff Faecal streptococci. water by birds roof of tank drainage of season Sanitary inspection and animals because of poor raidnwater (WQCD) drainage and inundates inspection covers Animal and bird Animal and bird Likely/ Trees do not Tree branches Trees within Sanitary Quarterly Operating staff Cut back tree E.coli faecal faecal material Moderate overhang the 2m from 0.5m of roof; inspection branches and Faecal streptococci. builds up on roof reservoir and reservoir roof; roof visibly dirty clean roof Sanitary inspection of service roofs kept roof clean (WQCD) reservoir clean Ingress of Inundation of inlet Moderate/ Good Valve boxes Cover out of Sanitary Monthly Operating staff Clean valve box E.coli contamination at valve of surface Major drainage in covered and do place, signs of inspection; and replace cover; Faecal streptococci. inlet valve water and valve box; not have standing water or material washout drain clear washout Bacteriophage covers on water or organic build-up; tests drain; replace Sanitary inspection valve box; material in base; packing shows packing (WQCD) valve packing packing does not visible signs of in good leak damage condition Ingress of Valve is inundated Almost Effective Valve box Drainage around Sanitary Monthly (SI) Operating staff Make sure all E.coli contamination at by surface water certain/ washout covered and no box blocked or inspection; Annual (drain boxes have Faecal streptococci. outlet/washout or waste water Major drains; visible signs or damaged; washout drain test) washout drain that Bacteriophage valve from reservoir covered valve water or waste washout drain test is jetted as part of Sanitary inspection box; good matter in box; blocked; water or regular (WQCD) quality valve washout drain waste build-up in maintenance; packing functional; valve box; routine packing packing in good packing showing replacement condition signs of wear Microbial Biofilm sloughs Likely/ Regular Interior of Biofilm Sanitary Monthly Operating staff Take reservoir Aeromonas contamination off or sediment is Minor cleaning of reservoir is clean develops, inspection, off-line and Biofilm coupons from biofilm or disturbed. service and sediment is increase in chlorine cleand Sanitary inspection sediment reservoir, minimised and chlorine residuals, (WQCD) drain-down of undisturbed consumption turbidity reservoir and clear sediment
Water safety plan for Muyenga service reservoirs C,D,E (with elbow and mesh vents) Hazard event Cause Risk Control Critical limits Monitoring Corrective action Verification measure Target Action What When Who Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating staff Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection Visible signs of Sanitary Quarterly/ Operating staff Replace damaged Inspection contamination of faeces enter Catastrophic covers and hatches and damage or inspection annually or corroded covers (WQCD) service reservoir through damaged hatches are covers show no corrosion and hatches from birds and or corroded kept in good visible sign of animals inspection hatches condition damage or corrosion Microbial Rodents or Moderate/ Vent mesh in Vent mesh in Mesh shows Sanitary Weekly Operations Repair and replace E.coli contamination of amphibians enter Minor place good condition visible signs of inspection staff damaged vents. Faecal streptococci. service reservoir service reservoir damage Sanitary inspection from animals through vents (WQCD) because mesh damaged Microbial Contaminated Moderate/ Roof gutters Gutters free of Gutters blocked, Sanitary Quarterly Operations Clear gutters E.coli contamination of water builds up on Major for easy debris start of rainy inspection staff Faecal streptococci. water by birds roof of tank drainage of season Sanitary inspection and animals because of poor rainwater (WQCD) drainage and inundates inspection covers Animal and bird Animal and bird Likely/ Trees do not Tree branches Trees within Sanitary Quarterly Operating staff Cut back tree E.coli faecal faecal material Moderate overhang the 2m from 0.5m of roof; inspection branches and Faecal streptococci. builds up on roof reservoir and reservoir roof; roof visibly dirty clean roof Sanitary inspection of service roofs kept roof clean (WQCD) reservoir clean Ingress of Inundation of inlet Moderate/ Good Valve boxes Cover out of Sanitary Monthly Operating staff Clean valve box E.coli contamination at valve of surface Major drainage in covered and do place, signs of inspection; and replace cover; Faecal streptococci. inlet valve water and valve box; not have standing water or material washout drain clear washout Bacteriophage covers on water or organic build-up; tests drain; replace Sanitary inspection valve box; material in base; packing shows packing (WQCD) valve packing packing does not visible signs of in good leak damage condition Ingress of Valve is inundated Almost Effective Valve box Drainage around Sanitary Monthly (SI) Operating staff Make sure all E.coli contamination at by surface water certain/ washout covered and no box blocked or inspection; Annual (drain boxes have Faecal streptococci. outlet/washout or waste water Major drains; visible signs or damaged; washout drain test) washout drain that Bacteriophage valve from reservoir covered valve water or waste washout drain test is jetted as part of Sanitary inspection box; good matter in box; blocked; water or regular (WQCD) quality valve washout drain waste build-up in maintenance; packing functional; valve box; routine packing packing in good packing showing replacement condition signs of wear Microbial Biofilm sloughs Likely/ Regular Interior of Biofilm Sanitary Monthly Operating staff Take reservoir Aeromonas contamination off or sediment is Minor cleaning of reservoir is clean develops, inspection, off-line and Biofilm coupons from biofilm or disturbed. service and sediment is increase in chlorine cleand Sanitary inspection sediment reservoir, minimised and chlorine residuals, (WQCD) drain-down of undisturbed consumption turbidity reservoir and clear sediment
Water safety plan for distribution from Muyenga service reservoirs
Hazard event Cause Risk Control Critical limits Monitoring Corrective Verification measure Target Action What When Who action Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Catastrophic and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V928 V190 water at the valve drainage; good condition; damage to drains; turbidity, any repairs Bacteriophage Block Map 1617 box structural valve box does signs of damage to chlorine made to drains Sanitary inspection integrity of box; not require box; valve packing residual and valve box; (WQCD) valve packing in repairs; vale leaking replace valve good condition packing does not packing leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Catastrophic and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V374 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 1917 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Major and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V199/V297 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2016 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Major and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1054 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 1621 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V438 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2726 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1289 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2712 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V469 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2120 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V811 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2018 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1347 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2917 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1427 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 1419 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1531 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 1720 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1345 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 3010 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1335 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 3111 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Moderate/ Good internal Drain clear; valve Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and external box in good blockage, signs of inspection, staff are cleared and Faecal streptococci. fire hydrant water through drainage; valve condition and damage to box; turbidity, repairs made to Bacteriophage H533/V122 hydrant valve box integrity; clear of any debris valve packing chlorine drains and valve Sanitary inspection Block Map 2019 valve box kept leaking; organic residual box; replace (WQCD) clean material built-up valve packing Microbial Contaminated Moderate/ Pipes buried at Pipes buried, no Pipes exposed; signs Sanitary See annex 2: Operating Repair leaks, E.coli contamination in water enters For impact depth on sign of leaks of leaks inspection, Primary - staff bury pipes and Faecal streptococci. distribution at through damaged rating see roadside, collars turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 reinforce joints chlorine Secondary - Sanitary inspection residual quarterly (WQCD) Tertiary (sample) Microbial Contaminated Moderate/ Provide support Non-approved Pipes unsupported, Sanitary See annex 2: Operating Provide E.coli contamination in water enters when For impact to pipes at pipe materials; no collars to support inspection, Primary - staff supports to Faecal streptococci. distribution at damaged pipe rating see channel/drain pipes entry into turbidity, monthly pipes, replace Bacteriophage channel/drain inundated by Annex 1 crossings and unsupported channel/drain chlorine Secondary - unapproved Sanitary inspection crossing contaminated use appropriate residual quarterly pipe materials (WQCD) surface water pipe material Tertiary connections (sample) Contamination Water flows from Moderate/ Non-return Non-return valves Non-return valve Sanitary Monthly Operating Ensure all repair E.coli enters distribution internal institution For impact valves (NRV) function correctly absent/faulty inspection; (NRV); staff (NRV) made to non- Faecal streptococci. system from distribution rating see on connection and water quality Absence of a water turbidity, annual WQCD return valves Bacteriophage major institutions system into mains Annex 1 to supply main. management plan quality management chlorine (plan audit) (audit) (NRV) and Sanitary inspection supply due to Institutional developed and plan residual; plans developed Audit reduced pressure water quality followed Institution and approved (WQCD) because of management WSP by audit intermittence or plan approved transient pressure by the utility fluctuations Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to sewers leakage data; monthly plan in place for Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance chlorine Secondary - water supply Sanitary inspection sewer system lies above the map) mains; leak quarterly and sewers Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme Microbial Ingress of Likely/ Leakage, Low levels of Sudden loss of Chlorine, See annex 2: Operating Repair and E.coli contamination contaminated For impact control, positive leakage in areas chlorine, increase in turbidity, Primary - staff rehabilitation Faecal streptococci. from faecally- water from soil rating see hydrostatic with on-site turbidity, leak leakage data monthly plan in place Bacteriophage contaminated containing Annex 3 (risk pressure; sanitation; detection Secondary - Sanitary inspection soils pathogens map) residual positive quarterly Audit disinfection hydrostatic Tertiary (WQCD) pressure, (sample) protective trench for mains Microbial Poor hygiene in Unlikely/ Hygiene code of Hygiene code Evidence that Turbidity During and Operating Train staff in E.coli contamination repair work allows Catastrophic practice for developed, hygiene code not Chlorine finish of staff hygiene code Faecal streptococci. introduced during contamination to repairs (see available to all followed residuals repair for repair work Bacteriophage repairs on enter into the manual of good staff and followed Site Clostridia distribution system practice) inspection perfringens system Sanitary inspection (WQCD) Biofilm Biofilm develops Moderate/ Control of Little biofilm Increases in Chlorine See annex 2: Operating Replacement of Aeromonas sloughing into and lack of minor biofilm through developed and turbidity, chlorine residual, Primary - staff high adherence Corrosion coupons drinking water control strategy. chlorination, limited risk of loss, changes in colour, annually pipe material, Record audit Hydraulic changes use of low- sloughing colour turbidity, Secondary - optimised (WQCD) lead to sloughing adherence odour, bi-annually treatment, materials, limit customer Tertiary improve steady potential for complaints (sample) state flow surges and water hammer Microbial Area surrounding Likely/ Keep area close No waste close to Waste close to tap, Sanitary Tertiary Community/ Training of E.coli contamination at tap and sanitary Moderate to tap clean and tap; tap and riser damage to tap or inspection (sample) operating communities to Faecal streptococci. tap condition of tap maintain in good condition riser staff maintain Bacteriophage allow entry of integrity of tap hygienic Sanitary inspection contaminated and riser surroundings (WQCD) water and repair tap and risers Microbial Contamination Likely/ Keep all mains All pipes buried Pipes exposed with Sanitary See annex 2: Operating Ensure that E.coli contamination at enters through Moderate buried to design or with secure no protection inspection Primary - staff exposed pipes Faecal streptococci. pipe exposed pipes (NB: on- depths; provide protection monthly are covered Bacteriophage selling and secure designs Secondary - Sanitary inspection public taps for over-ground quarterly (WQCD) serve many pipes Tertiary people) (sample)
Microbial Contamination of Moderate/ Cleaning Tanks clean and Tanks dirty or in Sanitary Periodic Community/ ` E.coli contamination of poorly maintained Moderate regime for tanks in good condition need of repair inspection operating Faecal streptococci. community tanks tanks established staff Bacteriophage Sanitary inspection (WQCD)
Water safety plan for Mutungo service reservoir
Hazard event Cause Risk Control Critical limits Monitoring Corrective Verification measure Target Action What When Who action Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection staff inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection hatches Visible signs of Sanitary Monthly Operating Replace Inspection contamination of faeces enter Catastrophic covers and and covers show damage or corrosion inspection staff damaged or (WQCD) service reservoir through damaged hatches are kept no visible sign of corroded covers from birds and or corroded in good damage or and hatches animals inspection hatches condition corrosion Microbial Rodents or Moderate/ Vent mesh in Vent mesh in Mesh shows visible Sanitary Weekly Operations Repair and E.coli contamination of amphibians enter Minor place good condition signs of damage inspection staff replace Faecal streptococci. service reservoir service reservoir damaged vents. Sanitary inspection from animals through vents (WQCD) because mesh damaged Microbial Contaminated Moderate/ Roof gutters for Gutters free of Gutters blocked, Sanitary Monthly Operations Clear gutters E.coli contamination of water builds up on Major easy drainage of debris start of rainy season inspection staff Faecal streptococci. water by birds roof of tank rainwater Sanitary inspection and animals because of poor (WQCD) drainage and inundates inspection covers Animal and bird Animal and bird Likely/ Trees do not Tree branches 2m Trees within 0.5m of Sanitary Monthly Operating Cut back tree E.coli faecal faecal material Moderate overhang the from reservoir roof; roof visibly inspection staff branches and Faecal streptococci. builds up on roof reservoir and roof; roof clean dirty clean roof Sanitary inspection of service roofs kept clean (WQCD) reservoir Ingress of Inundation of inlet Moderate/ Good drainage Valve boxes Cover out of place, Sanitary Monthly Operating Clean valve box E.coli contamination at valve of surface Major in valve box; covered and do signs of water or inspection; staff and replace Faecal streptococci. inlet valve water and covers on valve not have standing material build-up; washout drain cover; clear Bacteriophage box; valve water or organic packing shows tests washout drain; Sanitary inspection packing in good material in base; visible signs of replace packing (WQCD) condition packing does not damage leak Ingress of Valve is inundated Almost Effective Valve box Drainage around Sanitary Monthly (SI) Operating Make sure all E.coli contamination at by surface water certain/ washout drains; covered and no box blocked or inspection; Annual (drain staff boxes have Faecal streptococci. outlet/washout or waste water Major covered valve visible signs or damaged; washout washout drain test) washout drain Bacteriophage valve from reservoir box; good water or waste drain blocked; water test that is jetted as Sanitary inspection quality valve matter in box; or waste build-up in part of regular (WQCD) packing washout drain valve box; packing maintenance; functional; showing signs of routine packing packing in good wear replacement condition Microbial Biofilm sloughs Likely/ Regular Interior of Biofilm develops, Sanitary Monthly Operating Take reservoir Aeromonas contamination off or sediment is Minor cleaning of reservoir is clean increase in chlorine inspection, staff off-line and Biofilm coupons from biofilm or disturbed. service and sediment is consumption chlorine cleand Sanitary inspection sediment reservoir, drain- minimised and residuals, (WQCD) down of undisturbed turbidity reservoir and clear sediment Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1487 water at the valve drainage; good condition; damage to drains; turbidity, any repairs Bacteriophage Block Map 2336 box structural valve box does signs of damage to chlorine made to drains Sanitary inspection integrity of box; not require box; valve packing residual and valve box; (WQCD) valve packing in repairs; vale leaking replace valve good condition packing does not packing leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1871/2 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 24333 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Six-monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V1888 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2631 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Moderate/ Good internal Drain clear; valve Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and external box in good blockage, signs of inspection, staff are cleared and Faecal streptococci. Mbuya Booster water through drainage; valve condition and damage to box; turbidity, repairs made to Bacteriophage valve VO95 hydrant valve box integrity; clear of any debris valve packing chlorine drains and valve Sanitary inspection Block Map 2130 valve box kept leaking; organic residual box; replace (WQCD) clean material built-up valve packing Microbial Contaminated Moderate/ Pipes buried at Pipes buried, no Pipes exposed; signs Sanitary See annex 2: Operating Repair leaks, E.coli contamination in water enters For impact depth on sign of leaks of leaks inspection, Primary - staff bury pipes and Faecal streptococci. distribution at through damaged rating see roadside, collars turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 reinforce joints chlorine Secondary - Sanitary inspection residual quarterly (WQCD) Tertiary (sample) Microbial Contaminated Moderate/ Provide support Non-approved Pipes unsupported, Sanitary See annex 2: Operating Provide E.coli contamination in water enters when For impact to pipes at pipe materials; no collars to support inspection, Primary - staff supports to Faecal streptococci. distribution at damaged pipe rating see channel/drain pipes entry into turbidity, monthly pipes, replace Bacteriophage channel/drain inundated by Annex 1 crossings and unsupported channel/drain chlorine Secondary - unapproved Sanitary inspection crossing contaminated use appropriate residual quarterly pipe materials (WQCD) surface water pipe material Tertiary connections (sample) Contamination Water flows from Moderate/ Non-return Non-return valves Non-return valve Sanitary Monthly Operating Ensure all repair E.coli enters distribution internal institution For impact valves (NRV) function correctly absent/faulty inspection; (NRV); staff (NRV) made to non- Faecal streptococci. system from distribution rating see on connection and water quality Absence of a water turbidity, annual WQCD return valves Bacteriophage major institutions system into mains Annex 1 to supply main. management plan quality management chlorine (plan audit) (audit) (NRV) and Sanitary inspection (see Annex for supply due to Institutional developed and plan residual; plans developed Audit listing) reduced pressure water quality followed Institution and approved (WQCD) because of management WSP by audit intermittence or plan approved transient pressure by the utility fluctuations Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to sewers leakage data; monthly plan in place for Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance chlorine Secondary - water supply Sanitary inspection sewer system lies above the map) mains; leak quarterly and sewers Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme Microbial Ingress of Likely/ Leakage, Low levels of Sudden loss of Chlorine, See annex 2: Operating Repair and E.coli contamination contaminated For impact control, positive leakage in areas chlorine, increase in turbidity, Primary - staff rehabilitation Faecal streptococci. from faecally- water from soil rating see hydrostatic with on-site turbidity, leak leakage data monthly plan in place Bacteriophage contaminated containing Annex 3 (risk pressure; sanitation; detection Secondary - Sanitary inspection soils pathogens map) residual positive quarterly Audit disinfection hydrostatic Tertiary (WQCD) pressure, (sample) protective trench for mains Microbial Poor hygiene in Unlikely/ Hygiene code of Hygiene code Evidence that Turbidity During and Operating Train staff in E.coli contamination repair work allows Catastrophic practice for developed, hygiene code not Chlorine finish of staff hygiene code Faecal streptococci. introduced during contamination to repairs (see available to all followed residuals repair for repair work Bacteriophage repairs on enter into the manual of good staff and followed Site Clostridia distribution system practice) inspection perfringens system Sanitary inspection (WQCD) Biofilm Biofilm develops Moderate/ Control of Little biofilm Increases in Chlorine See annex 2: Operating Replacement of Aeromonas sloughing into and lack of minor biofilm through developed and turbidity, chlorine residual, Primary - staff high adherence Corrosion coupons drinking water control strategy. chlorination, limited risk of loss, changes in colour, annually pipe material, Record audit Hydraulic changes use of low- sloughing colour turbidity, Secondary - optimised (WQCD) lead to sloughing adherence odour, bi-annually treatment, materials, limit customer Tertiary improve steady potential for complaints (sample) state flow surges and water hammer Microbial Area surrounding Likely/ Keep area close No waste close to Waste close to tap, Sanitary Tertiary Community/ Training of E.coli contamination at tap and sanitary Moderate to tap clean and tap; tap and riser damage to tap or inspection (sample) operating communities to Faecal streptococci. tap condition of tap maintain in good condition riser staff maintain Bacteriophage allow entry of integrity of tap hygienic Sanitary inspection contaminated and riser surroundings (WQCD) water and repair tap and risers Microbial Contamination Likely/ Keep all mains All pipes buried Pipes exposed with Sanitary See annex 2: Operating Ensure that E.coli contamination at enters through Moderate buried to design or with secure no protection inspection Primary - staff exposed pipes Faecal streptococci. pipe exposed pipes (NB: on- depths; provide protection monthly are covered Bacteriophage selling and secure designs Secondary - Sanitary inspection public taps for over-ground quarterly (WQCD) serve many pipes Tertiary people) (sample)
Microbial Contamination of Moderate/ Cleaning Tanks clean and Tanks dirty or in Sanitary Periodic Community/ ` E.coli contamination of poorly maintained Moderate regime for tanks in good condition need of repair inspection operating Faecal streptococci. community tanks tanks established staff Bacteriophage Sanitary inspection (WQCD)
Gun Hill service reservoir area: water safety plan
Hazard event Cause Risk Control Critical limits Monitoring Corrective Verification measure Target Action What When Who action Microbial Birds faeces enter Likely/ Vent covers Vents covered 50% of vent Sanitary Weekly Operations Repair and E.coli contamination of through vents Catastrophic remain in place support struts are inspection staff replace Faecal streptococci. service reservoir because covers damaged damaged vents. Sanitary inspection from birds dislodged (WQCD) Microbial Birds faeces enter Likely/ Inspection Inspection covers Inspection covers Sanitary Daily Operating Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection staff inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection hatches Visible signs of Sanitary Quarterly/ Operating Replace Inspection contamination of faeces enter Catastrophic covers and and covers show no damage or inspection annually staff damaged or (WQCD) service reservoir through damaged hatches are kept visible sign of corrosion corroded covers from birds and or corroded in good damage or and hatches animals inspection hatches condition corrosion Microbial Rodents or Moderate/ Vent covers Vents covered 50% of vent Sanitary Weekly Operations Repair and E.coli contamination of amphibians enter Minor remain in place support struts are inspection staff replace Faecal streptococci. service reservoir service reservoir damaged damaged vents. Sanitary inspection from animals through vents (WQCD) because covers damaged Ingress of Shallow Moderate/ Structural Tank structure Drainage channels Sanitary Monthly Operations Clear drainage E.coli contaminated groundwater Major integrity and sound with no blocked; visible inspection staff channels. Take Faecal streptococci. water through ingress through drainage cracks; drainage signs of cracks tanks off-line Bacteriophage service reservoir cracks in service channels in good develop in tank for repairs. Sanitary inspection walls reservoir walls condition structure Flush tank and (WQCD) distribution before re- commissioning Ingress of Damage by trees Likely/ Structural No trees on Signs of tree Sanitary Annually Operating Keep grass on E.coli contaminated planted on Catastrophic integrity of reservoir roof and growth or crack inspection staff reservoir well Faecal streptococci. water through reservoir roof or roof; control no cracks in roof development maintained and Bacteriophage roof damage grass roots from tree growth close cropped Sanitary inspection large tussocks; (WQCD) inundation by surface water of reservoir roof Ingress of Inundation of inlet Moderate/ Good drainage Valve boxes Cover out of place, Sanitary Monthly Operating Clean valve box E.coli contamination at valve of surface Major in valve box; covered and do not signs of water or inspection; staff and replace Faecal streptococci. inlet valve water or ingress of covers on valve have standing material build-up; washout drain cover; clear Bacteriophage stagnant water box; valve water or organic packing shows tests washout drain; Sanitary inspection through leaking packing in good material in base; visible signs of replace packing (WQCD) valve packing condition packing does not damage leak Ingress of Valve is inundated Almost Effective Valve box covered Drainage around Sanitary Monthly (SI) Operating Make sure all E.coli contamination at by surface water certain/ washout drains; and no visible signs box blocked or inspection; Annual (drain staff boxes have Faecal streptococci. outlet/washout or waste water Major covered valve or water or waste damaged; washout washout drain test) washout drain Bacteriophage valve from reservoir box; good matter in box; drain blocked; test that is jetted as Sanitary inspection quality valve washout drain water or waste part of regular (WQCD) packing functional; packing build-up in valve maintenance; in good condition box; packing routine packing showing signs of replacement wear Microbial Biofilm sloughs Likely/ Regular Interior of reservoir Biofilm develops, Sanitary Monthly Operating Take reservoir Aeromonas contamination off or sediment is Minor cleaning of is clean and increase in chlorine inspection, staff off-line and Biofilm coupons from biofilm or disturbed. service sediment is consumption chlorine clean Sanitary inspection sediment reservoir, drain- minimised and residuals, (WQCD) down of undisturbed turbidity reservoir and clear sediment Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V – 244 water at the valve drainage; good condition; damage to drains; turbidity, any repairs Bacteriophage box structural valve box does not signs of damage to chlorine made to drains Sanitary inspection integrity of box; require repairs; box; valve packing residual and valve box; (WQCD) valve packing in vale packing does leaking replace valve good condition not leak packing Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage 391/V796/V-390, box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection Block Map 2023 integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve - water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage 1766/V1765 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection Block Map 2713 integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V831 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2317 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve industrial water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage area V309 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection (Interconnection integrity of box; require repairs; box; valve packing residual box; replace (WQCD) High/Low level) valve packing in vale packing does leaking valve packing Block Map 2222 good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V497 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2225 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage V1396/1397/1398 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection Block Map 2222 integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V831 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2317 box structural valve box does not signs of damage to chlorine drains and valve Sanitary inspection integrity of box; require repairs; box; valve packing residual box; replace (WQCD) valve packing in vale packing does leaking valve packing good condition not leak Microbial Ingress of Moderate/ Good internal Drain clear; valve Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Moderate and external box in good blockage, signs of inspection, staff are cleared and Faecal streptococci. fire hydrant fire water through drainage; valve condition and clear damage to box; turbidity, repairs made to Bacteriophage station H375 hydrant valve box integrity; of any debris valve packing chlorine drains and valve Sanitary inspection Block Map 2318 valve box kept leaking; organic residual box; replace (WQCD) clean material built-up valve packing Microbial Ingress of Moderate/ Good internal Drain clear; valve Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and external box in good blockage, signs of inspection, staff are cleared and Faecal streptococci. fire hydrant water through drainage; valve condition and clear damage to box; turbidity, repairs made to Bacteriophage H127 hydrant valve box integrity; of any debris valve packing chlorine drains and valve Sanitary inspection Block Map 2328 valve box kept leaking; organic residual box; replace (WQCD) clean material built-up valve packing Microbial Contaminated Moderate/ Pipes buried at Pipes buried, no Pipes exposed; Sanitary See annex 2: Operating Repair leaks, E.coli contamination in water enters For impact depth on sign of leaks signs of leaks inspection, Primary - staff bury pipes and Faecal streptococci. distribution at through damaged rating see roadside, collars turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 reinforce joints chlorine Secondary - Sanitary inspection residual quarterly (WQCD) Tertiary (sample) Microbial Contaminated Moderate/ Provide support Non-approved pipe Pipes unsupported, Sanitary See annex 2: Operating Provide E.coli contamination in water enters when For impact to pipes at materials; pipes no collars to inspection, Primary - staff supports to Faecal streptococci. distribution at damaged pipe rating see channel/drain unsupported support entry into turbidity, monthly pipes, replace Bacteriophage channel/drain inundated by Annex 1 crossings and channel/drain chlorine Secondary - unapproved Sanitary inspection crossing contaminated use appropriate residual quarterly pipe materials (WQCD) surface water pipe material Tertiary connections (sample) Contamination Water flows from Moderate/ Non-return Non-return valves Non-return valve Sanitary Monthly Operating Ensure all repair E.coli enters distribution internal institution For impact valves (NRV) function correctly absent/faulty inspection; (NRV); staff (NRV) made to non- Faecal streptococci. system from distribution rating see on connection and water quality Absence of a water turbidity, annual WQCD return valves Bacteriophage major institutions system into mains Annex 1 to supply main. management plan quality chlorine (plan audit) (audit) (NRV) and Sanitary inspection (see Annex for supply due to Institutional developed and management plan residual; plans developed Audit listing) reduced pressure water quality followed Institution and approved (WQCD) because of management WSP by audit intermittence or plan approved transient pressure by the utility fluctuations Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to leakage data; monthly plan in place for Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance sewers chlorine Secondary - water supply Sanitary inspection sewer system lies above the map) mains; leak quarterly and sewers Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme Microbial Ingress of Likely/ Leakage, Low levels of Sudden loss of Chlorine, See annex 2: Operating Repair and E.coli contamination contaminated For impact control, positive leakage in areas chlorine, increase turbidity, Primary - staff rehabilitation Faecal streptococci. from faecally- water from soil rating see hydrostatic with on-site in turbidity, leak leakage data monthly plan in place Bacteriophage contaminated containing Annex 3 (risk pressure; sanitation; positive detection Secondary - Sanitary inspection soils pathogens map) residual hydrostatic quarterly Audit disinfection pressure, protective Tertiary (WQCD) trench for mains (sample) Microbial Poor hygiene in Unlikely/ Hygiene code of Hygiene code Evidence that Turbidity During and Operating Train staff in E.coli contamination repair work allows Catastrophic practice for developed, hygiene code not Chlorine finish of staff hygiene code Faecal streptococci. introduced during contamination to repairs (see available to all staff followed residuals repair for repair work Bacteriophage repairs on enter into the manual of good and followed Site Clostridia distribution system practice) inspection perfringens system Sanitary inspection (WQCD) Biofilm Biofilm develops Moderate/ Control of Little biofilm Increases in Chlorine See annex 2: Operating Replacement of Aeromonas sloughing into and lack of minor biofilm through developed and turbidity, chlorine residual, Primary - staff high adherence Corrosion coupons drinking water control strategy. chlorination, limited risk of loss, changes in colour, annually pipe material, Record audit Hydraulic changes use of low- sloughing colour turbidity, Secondary - optimised (WQCD) lead to sloughing adherence odour, bi-annually treatment, materials, limit customer Tertiary improve steady potential for complaints (sample) state flow surges and water hammer Microbial Area surrounding Likely/ Keep area close No waste close to Waste close to tap, Sanitary Tertiary Community/ Training of E.coli contamination at tap and sanitary Moderate to tap clean and tap; tap and riser in damage to tap or inspection (sample) operating communities to Faecal streptococci. tap condition of tap maintain good condition riser staff maintain Bacteriophage allow entry of integrity of tap hygienic Sanitary inspection contaminated and riser surroundings (WQCD) water and repair tap and risers Microbial Contamination Likely/ Keep all mains All pipes buried or Pipes exposed with Sanitary See annex 2: Operating Ensure that E.coli contamination at enters through Moderate buried to design with secure no protection inspection Primary - staff exposed pipes Faecal streptococci. pipe exposed pipes (NB: on- depths; provide protection monthly are covered Bacteriophage selling and secure designs Secondary - Sanitary inspection public taps for over-ground quarterly (WQCD) serve many pipes Tertiary people) (sample)
Microbial Contamination of Moderate/ Cleaning Tanks clean and in Tanks dirty or in Sanitary Periodic Community/ ` E.coli contamination of poorly maintained Moderate regime for tanks good condition need of repair inspection operating Faecal streptococci. community tanks tanks established staff Bacteriophage Sanitary inspection (WQCD)
Water safety plan for Naguru service reservoir
Hazard event Cause Risk Control Critical limits Monitoring Corrective Verification measure Target Action What When Who action Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection staff inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection hatches Visible signs of Sanitary Quarterly/ Operating Replace Inspection contamination of faeces enter Catastrophic covers and and covers show damage or corrosion inspection annually staff damaged or (WQCD) service reservoir through damaged hatches are kept no visible sign of corroded covers from birds and or corroded in good damage or and hatches animals inspection hatches condition corrosion Microbial Rodents or Moderate/ Vent mesh in Vent mesh in Mesh shows visible Sanitary Weekly Operations Repair and E.coli contamination of amphibians enter Minor place good condition signs of damage inspection staff replace Faecal streptococci. service reservoir service reservoir damaged vents. Sanitary inspection from animals through vents (WQCD) because mesh damaged Microbial Contaminated Moderate/ Roof gutters for Gutters free of Gutters blocked, Sanitary Quarterly Operations Clear gutters E.coli contamination of water builds up on Major easy drainage of debris start of rainy season inspection staff Faecal streptococci. water by birds roof of tank rainwater Sanitary inspection and animals because of poor (WQCD) drainage and inundates inspection covers Animal and bird Animal and bird Likely/ Trees do not Tree branches 2m Trees within 0.5m of Sanitary Quarterly Operating Cut back tree E.coli faecal faecal material Moderate overhang the from reservoir roof; roof visibly inspection staff branches and Faecal streptococci. builds up on roof reservoir and roof; roof clean dirty clean roof Sanitary inspection of service roofs kept clean (WQCD) reservoir Ingress of Inundation of inlet Moderate/ Good drainage Valve boxes Cover out of place, Sanitary Monthly Operating Clean valve box E.coli contamination at valve of surface Major in valve box; covered and do signs of water or inspection; staff and replace Faecal streptococci. inlet valve water and covers on valve not have standing material build-up; washout drain cover; clear Bacteriophage box; valve water or organic packing shows tests washout drain; Sanitary inspection packing in good material in base; visible signs of replace packing (WQCD) condition packing does not damage leak Ingress of Valve is inundated Almost Effective Valve box Drainage around Sanitary Monthly (SI) Operating Make sure all E.coli contamination at by surface water certain/ washout drains; covered and no box blocked or inspection; Annual (drain staff boxes have Faecal streptococci. outlet/washout or waste water Major covered valve visible signs or damaged; washout washout drain test) washout drain Bacteriophage valve from reservoir box; good water or waste drain blocked; water test that is jetted as Sanitary inspection quality valve matter in box; or waste build-up in part of regular (WQCD) packing washout drain valve box; packing maintenance; functional; showing signs of routine packing packing in good wear replacement condition Microbial Biofilm sloughs Likely/ Regular Interior of Biofilm develops, Sanitary Monthly Operating Take reservoir Aeromonas contamination off or sediment is Minor cleaning of reservoir is clean increase in chlorine inspection, staff off-line and Biofilm coupons from biofilm or disturbed. service and sediment is consumption chlorine cleand Sanitary inspection sediment reservoir, drain- minimised and residuals, (WQCD) down of undisturbed turbidity reservoir and clear sediment Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve at Coca- water at the valve drainage; good condition; damage to drains; turbidity, any repairs Bacteriophage Cola factory box structural valve box does signs of damage to chlorine made to drains Sanitary inspection Block Map 1343 integrity of box; not require box; valve packing residual and valve box; (WQCD) valve packing in repairs; vale leaking replace valve good condition packing does not packing leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V377/378 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2025 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V046 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 1631 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Ingress of Likely/ Good external Internal and Evidence of drain Sanitary Monthly Operating Ensure drains E.coli contamination at contaminated Minor and internal external drains in blockage, signs of inspection, staff are cleared and Faecal streptococci. valve V453 water at the valve drainage; good condition; damage to drains; turbidity, repairs made to Bacteriophage Block Map 2028 box structural valve box does signs of damage to chlorine drains and valve Sanitary inspection integrity of box; not require box; valve packing residual box; replace (WQCD) valve packing in repairs; vale leaking valve packing good condition packing does not leak Microbial Contaminated Moderate/ Pipes buried at Pipes buried, no Pipes exposed; signs Sanitary See annex 2: Operating Repair leaks, E.coli contamination in water enters For impact depth on sign of leaks of leaks inspection, Primary - staff bury pipes and Faecal streptococci. distribution at through damaged rating see roadside, collars turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 reinforce joints chlorine Secondary - Sanitary inspection residual quarterly (WQCD) Tertiary (sample) Microbial Contaminated Moderate/ Provide support Non-approved Pipes unsupported, Sanitary See annex 2: Operating Provide E.coli contamination in water enters when For impact to pipes at pipe materials; no collars to support inspection, Primary - staff supports to Faecal streptococci. distribution at damaged pipe rating see channel/drain pipes entry into turbidity, monthly pipes, replace Bacteriophage channel/drain inundated by Annex 1 crossings and unsupported channel/drain chlorine Secondary - unapproved Sanitary inspection crossing contaminated use appropriate residual quarterly pipe materials (WQCD) surface water pipe material Tertiary connections (sample) Contamination Water flows from Moderate/ Non-return Non-return valves Non-return valve Sanitary Monthly Operating Ensure all repair E.coli enters distribution internal institution For impact valves (NRV) function correctly absent/faulty inspection; (NRV); staff (NRV) made to non- Faecal streptococci. system from distribution rating see on connection and water quality Absence of a water turbidity, annual WQCD return valves Bacteriophage major institutions system into mains Annex 1 to supply main. management plan quality management chlorine (plan audit) (audit) (NRV) and Sanitary inspection (see Annex for supply due to Institutional developed and plan residual; plans developed Audit listing) reduced pressure water quality followed Institution and approved (WQCD) because of management WSP by audit intermittence or plan approved transient pressure by the utility fluctuations Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to sewers leakage data; monthly plan in place for Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance chlorine Secondary - water supply Sanitary inspection sewer system lies above the map) mains; leak quarterly and sewers Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme Microbial Ingress of Likely/ Leakage, Low levels of Sudden loss of Chlorine, See annex 2: Operating Repair and E.coli contamination contaminated For impact control, positive leakage in areas chlorine, increase in turbidity, Primary - staff rehabilitation Faecal streptococci. from faecally- water from soil rating see hydrostatic with on-site turbidity, leak leakage data monthly plan in place Bacteriophage contaminated containing Annex 3 (risk pressure; sanitation; detection Secondary - Sanitary inspection soils pathogens map) residual positive quarterly Audit disinfection hydrostatic Tertiary (WQCD) pressure, (sample) protective trench for mains Microbial Poor hygiene in Unlikely/ Hygiene code of Hygiene code Evidence that Turbidity During and Operating Train staff in E.coli contamination repair work allows Catastrophic practice for developed, hygiene code not Chlorine finish of staff hygiene code Faecal streptococci. introduced during contamination to repairs (see available to all followed residuals repair for repair work Bacteriophage repairs on enter into the manual of good staff and followed Site Clostridia distribution system practice) inspection perfringens system Sanitary inspection (WQCD) Biofilm Biofilm develops Moderate/ Control of Little biofilm Increases in Chlorine See annex 2: Operating Replacement of Aeromonas sloughing into and lack of minor biofilm through developed and turbidity, chlorine residual, Primary - staff high adherence Corrosion coupons drinking water control strategy. chlorination, limited risk of loss, changes in colour, annually pipe material, Record audit Hydraulic changes use of low- sloughing colour turbidity, Secondary - optimised (WQCD) lead to sloughing adherence odour, bi-annually treatment, materials, limit customer Tertiary improve steady potential for complaints (sample) state flow surges and water hammer Microbial Area surrounding Likely/ Keep area close No waste close to Waste close to tap, Sanitary Tertiary Community/ Training of E.coli contamination at tap and sanitary Moderate to tap clean and tap; tap and riser damage to tap or inspection (sample) operating communities to Faecal streptococci. tap condition of tap maintain in good condition riser staff maintain Bacteriophage allow entry of integrity of tap hygienic Sanitary inspection contaminated and riser surroundings (WQCD) water and repair tap and risers Microbial Contamination Likely/ Keep all mains All pipes buried Pipes exposed with Sanitary See annex 2: Operating Ensure that E.coli contamination at enters through Moderate buried to design or with secure no protection inspection Primary - staff exposed pipes Faecal streptococci. pipe exposed pipes (NB: on- depths; provide protection monthly are covered Bacteriophage selling and secure designs Secondary - Sanitary inspection public taps for over-ground quarterly (WQCD) serve many pipes Tertiary people) (sample)
Microbial Contamination of Moderate/ Cleaning Tanks clean and Tanks dirty or in Sanitary Periodic Community/ ` E.coli contamination of poorly maintained Moderate regime for tanks in good condition need of repair inspection operating Faecal streptococci. community tanks tanks established staff Bacteriophage Sanitary inspection (WQCD)
Water safety plan for Rubaga service reservoir
Hazard event Cause Risk Control Critical limits Monitoring Corrective action Verification measure Target Action What When Who Microbial Birds faeces enter Moderate/ Inspection Inspection covers Inspection covers Sanitary Daily Operating Replace E.coli contamination of through open Catastrophic covers remain locked in place not in place or inspection staff inspection cover Faecal streptococci. service reservoir inspection hatches in place unlocked Chlorine and check Sanitary inspection from birds residual chlorine (WQCD) consumption Microbial Birds and animal Unlikely/ Inspection Inspection Visible signs of Sanitary Quarterly/ Operating Replace damaged Inspection contamination of faeces enter Catastrophic covers and hatches and damage or inspection annually staff or corroded covers (WQCD) service reservoir through damaged hatches are covers show no corrosion and hatches from birds and or corroded kept in good visible sign of animals inspection hatches condition damage or corrosion Microbial Rodents or Moderate/ Vent mesh in Vent mesh in Mesh shows Sanitary Weekly Operations Repair and replace E.coli contamination of amphibians enter Minor place good condition visible signs of inspection staff damaged vents. Faecal streptococci. service reservoir service reservoir damage Sanitary inspection from animals through vents (WQCD) because mesh damaged Microbial Contaminated Moderate/ Roof gutters Gutters free of Gutters blocked, Sanitary Quarterly Operations Clear gutters E.coli contamination of water builds up on Major for easy debris start of rainy inspection staff Faecal streptococci. water by birds roof of tank drainage of season Sanitary inspection and animals because of poor rainwater (WQCD) drainage and inundates inspection covers Animal and bird Animal and bird Likely/ Trees do not Tree branches Trees within Sanitary Quarterly Operating Cut back tree E.coli faecal faecal material Moderate overhang the 2m from 0.5m of roof; inspection staff branches and Faecal streptococci. builds up on roof reservoir and reservoir roof; roof visibly dirty clean roof Sanitary inspection of service roofs kept roof clean (WQCD) reservoir clean Ingress of Inundation of inlet Moderate/ Good Valve boxes Cover out of Sanitary Monthly Operating Clean valve box E.coli contamination at valve of surface Major drainage in covered and do place, signs of inspection; staff and replace cover; Faecal streptococci. inlet valve water and valve box; not have standing water or material washout drain clear washout Bacteriophage covers on water or organic build-up; tests drain; replace Sanitary inspection valve box; material in base; packing shows packing (WQCD) valve packing packing does not visible signs of in good leak damage condition Ingress of Valve is inundated Almost Effective Valve box Drainage around Sanitary Monthly (SI) Operating Make sure all E.coli contamination at by surface water certain/ washout covered and no box blocked or inspection; Annual (drain staff boxes have Faecal streptococci. outlet/washout or waste water Major drains; visible signs or damaged; washout drain test) washout drain that Bacteriophage valve from reservoir covered valve water or waste washout drain test is jetted as part of Sanitary inspection box; good matter in box; blocked; water or regular (WQCD) quality valve washout drain waste build-up in maintenance; packing functional; valve box; routine packing packing in good packing showing replacement condition signs of wear Microbial Biofilm sloughs Likely/ Regular Interior of Biofilm Sanitary Quarterly Operating Take reservoir Aeromonas contamination off or sediment is Minor cleaning of reservoir is clean develops, inspection, staff off-line and Biofilm coupons from biofilm or disturbed. service and sediment is increase in chlorine cleand Sanitary inspection sediment reservoir, minimised and chlorine residuals, (WQCD) drain-down of undisturbed consumption turbidity reservoir and clear sediment Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Monthly Operating Ensure drains are E.coli contamination at contaminated Catastrophic and internal external drains in drain blockage, inspection, staff cleared and any Faecal streptococci. valve V1297 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2415 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Monthly Operating Ensure drains are E.coli contamination at contaminated Catastrophic and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve 1554/1555 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2316 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Monthly Operating Ensure drains are E.coli contamination at contaminated Major and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve V1575 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2115 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Monthly Operating Ensure drains are E.coli contamination at contaminated Major and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve V1564/5 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2414 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Quarterly Operating Ensure drains are E.coli contamination at contaminated Moderate and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve V1151 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 1814 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Quarterly Operating Ensure drains are E.coli contamination at contaminated Moderate and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve H709 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2513 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Ingress of Likely/ Good external Internal and Evidence of Sanitary Quarterly Operating Ensure drains are E.coli contamination at contaminated Moderate and internal external drains in drain blockage, inspection, staff cleared and Faecal streptococci. valve V1301 water at the valve drainage; good condition; signs of damage turbidity, repairs made to Bacteriophage Block Map 2514 box structural valve box does to drains; signs chlorine drains and valve Sanitary inspection integrity of not require of damage to residual box; replace valve (WQCD) box; valve repairs; vale box; valve packing packing in packing does not packing leaking good leak condition Microbial Contaminated Moderate/ Pipes buried Pipes buried, no Pipes exposed; Sanitary See annex 2: Operating Repair leaks, bury E.coli contamination in water enters For impact at depth on sign of leaks signs of leaks inspection, Primary - staff pipes and Faecal streptococci. distribution at through damaged rating see roadside, turbidity, monthly reinforce joints Bacteriophage road crossings pipes Annex 1 collars chlorine Secondary - Sanitary inspection reinforce residual quarterly (WQCD) joints Tertiary (sample) Microbial Contaminated Moderate/ Provide Non-approved Pipes Sanitary See annex 2: Operating Provide supports E.coli contamination in water enters when For impact support to pipe materials; unsupported, no inspection, Primary - staff to pipes, replace Faecal streptococci. distribution at damaged pipe rating see pipes at pipes collars to turbidity, monthly unapproved pipe Bacteriophage channel/drain inundated by Annex 1 channel/drain unsupported support entry chlorine Secondary - materials Sanitary inspection crossing contaminated crossings and into residual quarterly (WQCD) surface water use channel/drain Tertiary appropriate (sample) pipe material connections Contamination Water flows from Moderate/ Non-return Non-return valves Non-return Sanitary Monthly Operating Ensure all repair E.coli enters distribution internal institution For impact valves (NRV) function correctly valve inspection; (NRV); annual staff (NRV) made to non- Faecal streptococci. system from distribution rating see on connection and water quality absent/faulty turbidity, (plan audit) WQCD return valves Bacteriophage major institutions system into mains Annex 1 to supply management plan Absence of a chlorine (audit) (NRV) and plans Sanitary inspection (see Annex for supply due to main. developed and water quality residual; developed and Audit listing) reduced pressure Institutional followed management Institution WSP approved (WQCD) because of water quality plan by audit intermittence or management transient pressure plan approved fluctuations by the utility Microbial Sewers and water Moderate/ Cut-off walls; Systems designed Sudden chlorine Risk See annex 2: Operating Repair and E.coli contamination supply mains For impact positive to prevent cross- loss, leakage in assessment; Primary - staff rehabilitation plan Faecal streptococci. from cross- placed too close to rating see hydrostatic connection under areas close to leakage data; monthly in place for water Bacteriophage connections to together or sewer Annex 3 (risk pressure in all circumstance sewers chlorine Secondary - supply and sewers Sanitary inspection sewer system lies above the map) mains; leak quarterly Audit main. repair; Tertiary (WQCD) emergency (sample) disinfection programme Microbial Ingress of Likely/ Leakage, Low levels of Sudden loss of Chlorine, See annex 2: Operating Repair and E.coli contamination contaminated For impact control, leakage in areas chlorine, turbidity, Primary - staff rehabilitation plan Faecal streptococci. from faecally- water from soil rating see positive with on-site increase in leakage data monthly in place Bacteriophage contaminated containing Annex 3 (risk hydrostatic sanitation; turbidity, leak Secondary - Sanitary inspection soils pathogens map) pressure; positive detection quarterly Audit residual hydrostatic Tertiary (WQCD) disinfection pressure, (sample) protective trench for mains Microbial Poor hygiene in Unlikely/ Hygiene code Hygiene code Evidence that Turbidity During and Operating Train staff in E.coli contamination repair work allows Catastrophic of practice for developed, hygiene code Chlorine finish of repair staff hygiene code for Faecal streptococci. introduced during contamination to repairs (see available to all not followed residuals repair work Bacteriophage repairs on enter into the manual of staff and followed Site inspection Clostridia distribution system good perfringens system practice) Sanitary inspection (WQCD)
Water Safety Plan: Gaba I Treatment Works Unit Hazard Cause Risk Control Critical Limits Monitoring Corrective Verification Process Event Measure Action Target Levels Action Level What When Who Intake High iron in Corrosion of Moderate/ Iron readings Iron 0.3mg/l >0.3mg/l Test for Monthly WTPO Bleaching/cleaning Audit, customer raw water intake screens Insignificant Colour readings iron of screens complaints
Blockage of Shallow intake Likely/ Flow readings and 3,745m3.hr <3,000m3/hr Pumping On-line, WTPO Increase depth of Audit, inspection raw water resulting in Catastrophic throughput in raw rate at least intake screen close contact water sump hourly with algae, plastic bottles, polythene bags Microbial Bird droppings Moderate/ Sanitary integrity No bird droppings Visible bird Sanitary Daily WTPO Regular cleaning of E.coli contamination on access bridge Minor of access bridge build up on bridge droppings on survey access bridge Faecal of water overlaying inlet bridge Ensure limited streptococci entering plant pipe leakages in inlet pipe Inspection Raw water Breakthrough High sediment Likely/ Sanitary integrity Turbidity below Turbidity exceeds Turbidity Weekly WTPO Increase cleaning E.coli sump of pathogenic loading in Catastrophic of booster tank 100 NTU; no 100 NTU; visible and frequency from 12 Faecal bacteria to micro-strainer visible bird bird droppings sanitary months to 6 months streptococci candy filters booster tank and droppings inspection Clostridia visible bird perfringens droppings Audit Patterson Contaminated Leaking tank Moderate/ Disposal of first 90% reduction in Turbidity 0.3NTU Turbidity On back- WTPO Fix tank E.coli and water used for (existent for Major filtrate after turbidity washing Don’t run the sand Clostridia Mannesman backwashing more than 10 backwashing to <0.2 NTU dry perfringens backwashing years) waste Audit tank Candy filter Contaminated Leaking valve Moderate/ Disposal of first 90% reduction in Turbidity 0.3NTU Turbidity On back- WTPO Fix tank E.coli backwashing water used for on tank Major filtrate after turbidity washing Don’t run the sand Clostridia tank backwashing backwashing to <0.2MTU dry perfringens filters waste Audit Filtration Mannesman Overloading of Moderate/ Reduction of 0.1NTU 1NTU Head loss On-line WTPO Fix air scourers Audit; inspection (Mannesman filters - mud filters Major turbidity to Backwashing 15m <15m head Inspection At least of backwashing 4 filters) balling and <1NTU head @ <1,200m3/hr daily formation of Headloss during 1,200m3/hr sand pockets at backwashing edge of tank Short-circuiting Poor operation Moderate/ Control of Filtration rate of Filtration rate < Filtration On-line WTPO Uniform distribution Turbidity of Manneman of manually Major filtration rates 7.1m/hour 7.1 m/hr rate At least of flow Colour filters operated filter Turbidity = Turbidity daily Audit rates <0.2NTU = >0.2NTU E.coli Clostridium perfringens
Uneven filter Poor Moderate/ Air scouring rates 38.7m3//hr at <38.7m3/hr Air On back- WTPO Ensure air scourers Audit bed performance as Major 0.9bar at less 0.9 bar scouring washing perform efficiently Turbidity air scourers are rates Colour not all E.coli operational Clostridium perfringens Contamination Mannesman line Moderate/ Sanitary integrity Minimum distance <10m Sanitary Annual WTPO Move septic tank E.coli of filtrate located close to Moderate of facility of 10m from septic inspection Faecal septic tank streptococci tank/soakaway Excessive algal Back washing of Moderate/ Filtration rates 7.7m/hour <7.7m/hour Filtration On-line WTPO Balancing filtration Algal cells formations filters <18 hour Moderate Head loss filtration rate rate At least rate with flow rates Colour intervals daily
Cross Mixing of Likely/ Control of 0.2mg/Cl2 <0.2mg/Cl2 Chlorine On line WTPO Ensure efficiency of E.coli contamination filtrate in Major chlorine residual residual At leas on line chlorinators Faecal of Paterson contact tanks prior to hourly streptococci with intermixing Mannesman Candy filters Excessive algae Increased air Likely/ Cleaning by air Scouring at Scouring at Head-loss On line WTPO Ensuring cleaning Turbidity blocking filters scouring and Moderate scourers and 36.7m3/hr at 3 bar <36.7m3/hr at 3 At least undertaking based on Colour backwashing backwashing and Backwashing at bar daily head-loss; maintained E.coli every 18-24 head loss 68m3/hr and head Backwashing at > air scourers Faecal hours for 8-10 loss at 15m 68m3/hr and head streptococci minutes Turbidity loss at > 15m Clostridia <02.NTU Turbidity perfringen >0.2NTU
Ineffective Insufficient Likely/ Residual chlorine 0.2-0.5mg/l <0.15mg/l residual Chlorine On-line WTPO Having functioning Turbidity chlorination dosing, buried Catastrophic Turbidity; pH residual chlorine >1..5NTU dosing At least dosing equipment E.coli line makes leak <1NTU pH>8 records hourly and monitors on inlet Faecal detection pH <8 Free and outlet. Install streptococci difficult chlorine alarms to warn of residuals dose reduction Turbidity pH
Chlorination No chlorine No booster Unlikely/ Dosing rates at 3kg/l per pump <3kg/l per pump Chlorine On-line WTPO Ensure that dosing E.coli dosing on high pump Catastrophic 3kg/hr x 3 for each or pump off line residual At last occurs in high level Faecal level water post sedimentation daily clearwell streptococci stage No back up Lack of HTH Likely/ Ensure sufficient HTH supply Less than 7 days Stores Daily WTPO Ensure stores hold Audit chlorine in case available as Catastrophic stock of HTH sufficient for one supply sufficient stocks of of failure back-up month HTH
Water Safety Plan: Gaba II Treatment Works Unit Hazard Cause Risk Control Critical Limits Monitoring Corrective Verification Process event Measure Target level Action level What When Who Action
Source water Presence of Nutrient Unlikely/ Control of nutrient No visual blue Blue green algae Inspection Annually WTPO/ Source water Inspection/ toxic cyano- enrichment in moderate inputs into IMB green algae Assess WQCD catchment assessment bacteria in source waters source management plan source water water Intake Reduced Fishermen’s Moderate/ Intake protected Dip test to 3m 2.5m Raw Daily WTPO Removal of nets. Audit and flow into raw nets, shells or Catastrophic against damage (tank is 6m deep) 2 operational water Increase regular inspection water sump other debris with minimal 2 operational pumps @ < sump removal of course clogging course water level in raw pumps @ 3000m3/hr levels screen inlet screen water sump of 3m 3000m3/hr Pumping rates at flow meter Water levels in raw water sump Sloughing of Algal formation Unlikely/ Regular flushing No biofilm Breakthrough Sanitary Quarterly WPTO Regular cleaning of Inspection algae inside inlet pipe Minor of inlet pipe. formation in pipe occurs inspection pipe reduce from 12 through to month to 6 months raw water sump / biofilm formation Raw water Low levels Inadequate Likely/ Regular cleaning Dip test to 3m 2.5m Dip Test Daily WTPO Regular cleaning of Inspection; audit sump in raw water through flow Minor of screens (tank is 6m deep) raw water screens of records sump due to resulting in die increased from 12 to blockage of off of organic 6 months screens matter in tank
Algal Larvae growing Likely/ Regular cleaning Water free of large Presence of large Sanitary Monthly WTPO Reduce through flow Audit; E.coli, blooms in sump Moderate of screens organic or aquatic organic/aquatic inspection of plant and increase aeromonas leading to reducing BOD life life continuous fish dying in clarification raw water sump (occurred in 2000) Increased Excessive Moderate/ Regular cleaning Iron 0.3mg/l Iron > 0.3mg/l Test for Monthly WTPO Bleaching/cleaning Audit, customer iron levels in corrosion of Insignificant of screen iron of screens complaints raw water course screens Tripping of Clogging of Likely/ Clean screens and 3,500m3/hr at 3 Minimal Inspection On line WTPO Regular cleaning of Audit, inspection raw water screens Catastrophic ensure clear pumps functioning for flow rate At least screens pumps and clarifiers daily insufficient 2000m3/hr production Failure in Lightening Likely/ Secure stable 415 volts from <415 volts Inspection On line WTPO Earth electric supply Audit, inspection raw water striking / Catastrophic electricity supply 11kVA power Install back up pumps and irregular power generator; install plant failure supply to raw alarm for power loss water pump Clarification Poor floc Poor mixing, Likely/ Effective mixing Retention time 2.1 Retention time Flow rate, Weekly WTPO Fix automatic Clostridia Coagulation formation insufficient or Major of coagulant. hours, controlled reduced, flow turbidity, discharge levels on perfringens Flocculation/ and/or excessive inlet Retention time T = velocity exceeds design inspection pumps Retention time sedimentation flooding of pressure from 2.1 hours Raise clarifier inlets tracer tests clarifier raw water to accommodate flow inlets pumps from pumps Graduated/slopping improvement s to clarifier inlets Poor floc Non uniform Likely/ Well constructed Minimum <2.1hrs Flow rate On line WTPO Cover tanks; ensure E.coli formation in distribution and Major tanks and sinuous residence time of At least effective mixing Clostridia inner part of mixing of channels 2.1hrs daily perfringens clarifier units coagulant Wind and temperature effecting mixing Excessive Inadequate Likely/ Use 5% solution = 30mg/l <30mg/l Jar tests Hourly WTPO Increase or reduce Jar test records use of alum mixing of alum Insignificant > 30mg/l mixing Turbidity At least coagulant dose and Dosing records chemicals during Colour daily residence time. Add hydraulic rapid polymer coagulant mixing aid Lack of synchronisation of raw water pump flow and dosing rate Excessive Dead end in Likely/ Ensure effective No micro-floc Micro-floc carry- Inspection At least WTPO Ensure that retention Audit of records build up of clarifier Minor floc formation and carry-over over observable wekkly time is sufficient for sludge/algae channels removal effective floc in clarified resulting in formation and water excessive removal flushing in of sludge Inadequate In operational Likely/ Ensure sludge Sludge bleeding Build-up of Inspection At least WTPO Fix sludge discharge Audit mixing due sludge Minor discharge gate occurs at required unstable sludge monthly gates to discharge gate operational and intervals blanket insufficient that sludge is sludge removed bleeding Excessive Blocked Moderate/ Ensure tridents are No algal build-up Indication of algal Inspection At least WTPO Increase frequency of Audit algal loading tridents during Minor not blocked in clarified water build-up in monthly unblocking of in clarified cleaning clarified water tridents using water chlorine and jet hose to unblock tridents to once per year rather than once per 3 years Refill tank at non peak demand time s(i.e. at night to give more time for closer inspection)
Filtration Presence of Corrosion of Likely/ Reduction in 0.2NTU >0.2NTU Turbidity, Daily WTPO Reduce alum dose Inspection, audit corroded sheer pins due Minor turbidity to flow rate At least and improve debris to addition of <0.1NTU weekly clarification resulting in chlorine after efficiency clogging of clarification filters Disinfection Inadequate Insufficient Likely/ Ensure adequate 02.-0.5mg/l free <0.15mg/l free Chlorine Hourly WTPO Improve logistical E.coli disinfection supply of Cl2 Catastrophic Ct value chlorine after 30 chlorine after 30 dosing supply Faecal gas (e.g.2002 minutes minutes records Have standby HTH streptococci no gas for 1 Free (need a lot as use month) chlorine >900kg per day) residual Excessive 2 chlorinators Likely/ Proper control of Total residual Total residual is Chlorine On-line WTPO Improve dosing and Audit chlorine (1 on standby) Minor chlorine dosing in should never >5mg/l dosing At least demand caclulation dosing @ 11kg/hr response to exceed 5mg/l daily during time of calculated chlorine (WHO GV) audit no demand calibration records available Soda Ash Over dosing Soda ash Likely/ pH 6.3-6.5 or 6.7- Dose according to Dosing carried out Dosing Daily WTPO More regular Audit of soda ash addition to Insignificant 6.9 but soda ash pH correction without reference records monitoring of soda water pH still added need to pH adjustment ash addition needs