Our Ref: DWI/2/10 Event 30/10 Date: 9 June ... - Derry City Council

Our Ref: DWI/2/10 Event 30/10
Date: 9 June 2011
Mr G Butler
Asset Management Director
Northern Ireland Water
Westland House
Old Westland Road
BELFAST
BT14 6TE
Dear George
DRINKING WATER INSPECTORATE’S (DWI) ASSESSMENT LETTER - ADVERSE
WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN IRELAND, 27
DECEMBER 2010 – 6 JANUARY 2011
1. Introduction
1.1 The purpose of this letter is to inform you of the conclusions and recommendations
arising from DWI’s assessment of the incident involving the loss of supplies across
Northern Ireland in December 2010 and January 2011, following a sustained period of
adverse weather. This takes into consideration NI Water’s response (received 1 April
2011) to DWI’s initial assessment letter (issued on 4 March 2011).
1.2 NI Water is required under regulation 33(6) to notify district councils, health authorities
and the Department (in effect DWI) of any event which gives rise, or is likely to give
rise, to a significant risk to human health. NI Water notified DWI of this event on 27
December 2010.
1.3 When notified of an event, the Inspectorate assesses NI Water’s reports and other
information gathered in the course of its assessment for compliance with the
regulations and, where appropriate, provides comments to NI Water on the way in
which the company managed the event. The Inspector’s investigation assessment
report containing findings and assessments are provided in Annex 1. A summary of
the recommendations and any outstanding actions required to be undertaken by NI
Water are provided for ease of reference in Annex 2 to this letter.
1.4 In addition to this, during the period of the incident, the Inspectorate was notified of
events under the regulatory reporting requirements regarding water quality
contraventions at nine water treatment works. The assessment of the events relating
to performance of the water treatment works will be individually assessed and reported
through our normal regulatory reporting procedures. A summary of these events is
contained in Annex 3.
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1.5 Information was gathered during the course of this assessment from NI Water through
regulatory reporting requirements, follow up discussions and written information
requests. Other sources of information were also taken into consideration in making
this assessment, these included the: Public Health Agency (PHA); Northern Ireland
Authority for Utility Regulation (NIAUR); Consumer Council for Northern Ireland (CCNI)
and; Northern Ireland Environment Agency (NIEA).
1.6 I acknowledge that NI Water was asked to provide substantive information to others
who have been tasked to investigate specific matters associated with this incident. I
note the published report 1 by NIAUR (3 March 2011) contains key findings and a
recovery plan relating to the cause for loss of supply and the performance of NI Water.
2. Overview of the incident
2.1 During December 2010 and January 2011 adverse weather conditions prevailed
across Northern Ireland which experienced extreme sub zero temperatures with
December 2010 registering as the coldest month on record. Across the region,
prolonged frozen ground conditions followed by a rapid thaw caused major difficulties
in maintaining the integrity of the water supply network. The output production of water
treatment works was maximised, service reservoir storage levels were rapidly
depleted and a significant number of water supply pipes burst, both within NI Water’s
distribution network, and within customers’ properties. During the incident it is
estimated that 215,000 properties experienced interruptions to their supply.
2.2 As a consequence, the provision of drinking water supplies across Northern Ireland
was affected and alternative water supplies had to be made available in many
locations:
50 tankers were used to augment supplies at water treatment works, service
reservoirs and to fill static tanks;
149 static tanks were deployed at 77 locations;
water was also supplied to customers directly from tankers on one occasion;
eight standpipes were put in place;
over 820,000 litres of bottled water was made available, of which over 410,000
litres was distributed; and
rotation of water supplies in a number of areas was introduced to enable a
supply to be maintained and service reservoirs to recover.
2.3 The production of normal water supply volumes rose rapidly because demand
increased by over 200 million litres a day due to leakage in the network, together with
bursts within private pipes. Water treatment works were operating at much higher than
normal outputs (average daily distribution input of 620 million litres a day rising to a
maximum of 862 million litres a day) during the incident.
1 Utility Regulator's report of the investigation into the Freeze/Thaw incident 2010/11.pdf
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2.4 To augment supplies at strategic locations, NI Water:
tankered treated water into three water treatment works
(Camlough WTWs, Carran Hill WTWs and Clay Lake WTWs);
put two emergency sources (Glarryford and Cabragh Boreholes) back into
supply;
obtained treated water from Louth County Council and tankered it into Clay
Lake WTWs;
tankered treated water into 22 service reservoirs; and
obtained temporary authorisation from NIEA to increase abstraction from two
sources (River Derg and Lough Neagh) for production purposes at Derg and
Dunore Point WTWs (the additional abstraction at Dunore was not required).
2.5 During the incident final water quality at nine works was affected in the short term and
where the standards were breached these were notified to the Inspectorate in
accordance with regulatory reporting requirements. These are listed below:
Cabragh / Gortlenaghan WTWs (iron and manganese);
Carmoney WTWs (turbidity);
Dorisland WTWs (aluminium);
Caugh Hill WTWs (turbidity);
Lough Macrory WTWs (aluminium);
Ballinrees WTWs (aluminium);
Dunore Point WTWs (aluminium);
Lenamore Springs WTWs (turbidity); and
Killylane WTWs (turbidity and aluminium).
A range of problems at the WTWs including; instrument faults; response to alarms;
freeze/thaw damage, effects of low temperature on the coagulation process; and
increased production; which were all factors in one or more of these events. Annex 3
to this letter provides additional summary detail relating to these events.
2.6 Stocks of water normally available in many service reservoirs were severely depleted.
Of the 330 service reservoirs monitored for compliance purposes 55 had less than
0.5 metres storage capacity continuously for more than 24 hours.
2.7 NI Water repaired bursts to its distribution network at:
one trunk main;
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286 distribution mains;
880 communication pipes; and
180 fittings.
A significant number of bursts occurred on private property and these do not form part
of this assessment. It is estimated that 80% of the additional water demand caused by
the freeze/thaw leaked from domestic and business water pipes.
3. Conclusions
3.1 I note that, due to the complex nature and extent of this incident, and given the scale
and operational demands, the company’s main priority was the restoration of water
supplies and the delivery of alternative interim supply arrangements.
3.2 While undertaking the many activities to restore supplies NI Water has also a duty to
ensure that public health is protected through the provision of safe drinking water
supplies and that appropriate mitigation measures are put in place to manage any risk
of supplying water which could constitute a potential danger to human health.
3.3 The post incident assessment undertaken by my inspectors is based on the currently
available information and provides comment and makes recommendations on how
NI Water carried out its drinking water quality regulatory duties. Since my initial
assessment letter was issued seeking assurances, further information requirements
and making recommendations to NI Water, several follow up actions are underway or
have been completed.
3.4 The follow up actions in Annex 2 are considered necessary to give the assurance that
any key learning points from this incident are carried forwards to ensure regulatory
compliance and uphold public confidence. It is necessary for NI Water to ensure that
risks to public health are being robustly managed to prevent the potential
contamination of drinking water supplies, particularly when normal operational
conditions do not prevail. Pending satisfactory completion of the remaining follow up
actions, the Inspectorate will proceed to close this incident file.
3.5 The following paragraphs provide summary detail on the main aspects of the
Inspectors assessment of this incident.
3.6 Incident management
3.6.1 NI Water had in place a Major Incident Plan (MIP). This provides the necessary
framework to manage sufficiency and supply issues. Roles, responsibilities, tasks and
activities are identified with the scientific adviser playing a key role in water quality
matters.
3.6.2 NI Water needs to have its MIP supported by the application of good operational
procedures and that record keeping is carried out robustly throughout any incident.
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3.6.3 During any incident it is incumbent upon NI Water to manage the risks to prevent the
introduction of contamination into the water supply. It is paramount that the framework
within the MIP is put into effective operation and that good communication and close
liaison with relevant stakeholders is maintained. This is to enable appropriate and
timely advice being given to protect consumers of any potential risk of contaminated
water, and what action consumers can take during such emergency situations.
3.6.4 The Inspectorate acknowledges that due to the scale of this incident there was an
unprecedented demand placed on NI Water’s customers’ services which would
normally record customers concerns and complaints. However, the Inspectorate is
concerned that the systems that were in operation were unable to allow consumers
concerns or complaints to be recorded as required in DWI Information Letter 01/11.
This is a particular issue regarding the recording of information relating to the
appearance of the water, given the potential for consumers to be concerned during
incidents, as well as the considerations regarding the provision of ‘unfit’ water for
human consumption.
3.6.5 Given the large scale disruption and restoration of the distribution network during the
incident, this may have caused concern for consumers who may have experienced
problems with receiving discoloured water. It is the Inspectorate’s assessment that
consumers would have benefited if they had been given information on what to expect
during the disruption to normal services and when their water supplies were being
restored. The Inspectorate recommends that NI Water reviews its communication of
key messages such as ‘discolouration due to mains deposits’ or ‘cloudiness due to air’
and also to consider giving advice on any steps consumers may take until the water
quality returns to normal.
3.7 Record keeping
3.7.1 It is fundamental to recognize the importance of having effective record keeping at all
levels. This applies, not only to staff in the incident room, but also to the management
of all staff and resources, to ensure that the information requirements can be met.
Records are kept to support the decisions that are taken during the incident of how
risks are managed to avoid contamination. The information logs and data sheets also
provide the necessary evidence to demonstrate that regulatory responsibilities have,
or have not, been met.
3.7.2 The Inspectorate recommends that robust records are required to provide information
in support of actions NI Water took to manage the water quality aspect during this
incident and has recommended that the relevant sections of the MIP on record
keeping are reviewed. Significant gaps in documentation provision extended from
communication logs on how decisions were made between NI Water and key
stakeholders regarding public health protection, through to sufficiency of records to
demonstrate compliance with the provision of alternative supplies.
3.8 Risk management
3.8.1 The Inspectorate assesses what measures NI Water has in place to manage any risk
of supplying water which could constitute a potential danger to human health during
the incident. A risk based approach needs to be applied to all of NI Water’s activities
as it is paramount to safeguard consumers particularly where normal operational
conditions do not prevail.
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3.8.2 It is the Inspectorate’s assessment that, when a significant loss of supplies has been
experienced, a comprehensive programme of water quality checks is necessary and
that such an operational sampling programme should be related to the assessment of
the potential risks to public health. The monitoring programme is necessary to verify
that there has not been a breach of the integrity of the distribution network such as
may be caused by: multiple repairs of burst pipework and fittings; valving operations;
sediment disturbance when service reservoirs are being refilled following significant
depletion; and reintroducing water into the distribution network.
3.8.3 It is not evident from the information made available to the Inspectorate that such a
robust programme was in place during this incident. The Inspectorate is concerned
that there was a reliance on compliance monitoring, with no clear information available
from any specific operational monitoring plan put in place during this incident. The
Inspectorate therefore recommends that NI Water reviews its operational monitoring
plan to take account of the specific circumstances which could be encountered during
such emergency situations and that such a plan should take account of the
assessment of the potential risks to public health.
3.8.4 The Inspectorate has concerns in relation to how NI Water managed the risks
associated with the provision of alternative supplies involving ‘third parties’. The
Inspectorate recommends that NI Water undertake a review of how it can be assured
that, during emergency situations when water is provided to consumers involving a
‘third party’, it has the necessary checks and procedures in place to enable it to
demonstrate to the Inspectorate that the water supplied is wholesome.
3.9 Water treatment works performance
3.9.1 NI Water was required to maximise output from its water treatment works during the
incident. The majority of its works continued to produce high quality drinking water;
however this increased production resulted in short term water quality issues at nine of
the 31 works, due to factors such as: instrumentation faults; freeze/thaw damage;
effectiveness of coagulation at lower temperatures; and operational response to
process alarms. NI Water, through the ‘normal event reporting process, has identified
to the Inspectorate what remedial action has been taken for each of these sites
(Annex 3 refers).
3.9.2 I would emphasise the importance of responding to malfunctions associated with the
telemetry alarms systems especially when critical control alarms are not operational or
are not triggered. This is particularly significant given the importance of the
coagulation process and how it can be affected by many factors, including pH and low
temperatures. I also would emphasise the criticality of optimal operational
performance at water treatment works particularly when there are demands such as in
emergency situations when extra throughput is required and normal working patterns
may need to be adjusted to ensure integrity of the treatment processes.
3.9.3 During this incident there was significant disruption to the production of water within
water treatment works and in its storage and onward distribution. It is critical that, in all
such circumstances, the disinfection process is not compromised. NI Water is
required to ensure it has in place a disinfection policy to cover individual sites where
disinfection is practised and to ensure that this extends to emergency situations where
alternative supplies may be used.
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4. General requirements
4.1 Further action is required to be taken by NI Water and this is detailed in Annex 2 to
this letter. Pending satisfactory completion of these requirements the Inspectorate will
proceed to close this incident file.
4.2 I am happy to discuss further any points the Inspectorate has raised through the
assessment of this incident. Any enquiries should be addressed to me (9056 9294) or
Colin Clements (9056 9242).
4.3 Copies of this letter are being sent to the Director of Water Policy Division, DRD;
Director of Environmental Protection (Northern Ireland Environment Agency); the
Director of Water Regulation, NIAUR; the Director of the Public Health Agency; the
Chief Environmental Health Officer, DHSSPS; the Head of Water, CCNI; and the Chief
Environmental Health Officers.
4.4 Please acknowledge receipt of this letter, by e-mail to DWI@doeni.gov.uk
Yours sincerely
Margaret Herron
Chief Inspector of Drinking Water
Drinking Water Inspectorate
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Annex 1
DWI’s OPERATIONAL INSPECTOR’S INVESTIGATION ASSESSMENT REPORT -
ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
1. Incident management
1.1 NI Water managed the incident caused by this loss of supply through its Major Incident
Planning (MIP) and civil contingency processes: a level 3 incident team was
established on 17 December 2010 which involved management at a local level. On 26
December 2010 NI Water took the decision to escalate the incident to category 1 and
on 27 December 2010 an incident management team was established. An incident
management Gold team was established at NI Waters Head Offices, with Silver and
Bronze Teams mobilized in regional locations. The Inspectorate was advised that NI
Water had scientific advisory representation within the MIP Gold Team in matters
relating to ‘public health, drinking water quality regulation and water supply’ from the
afternoon of 28 December 2010.
1.2 Roles, responsibilities, tasks and activities are identified and assigned within NI
Water’s MIP; this provides a framework to bring together people with the necessary
skills and expertise. This makes provision for matters relating to water quality such as
the provision of network management including alternative supplies, sampling and
process control. Specific roles and duties are identified for the Scientific Advisor.
1.3 There is also a duty to contact other stakeholders during an incident. This is of
particular significance should there be any water quality matter that may give rise, or is
likely to give rise, to a significant risk to human health. In such a case, the Public
Health Agency and the Chief Environmental Health Officers would be contacted. There
are well established procedures in place that are used to respond to contraventions of
water quality parameters; this continued to be operational practice during the incident.
This is a key role for the Scientific Advisor.
1.4 The Civil Contingencies Group, which is the body set up to coordinate public sector
organisations in an emergency, met on 30 December 2010.
1.5 Throughout the incident, NI Water carried out significant operational work to get
customers back onto mains water supply but operational water quality sampling was
limited. In the circumstances, the Inspectorate would have expected a comprehensive
operational water quality sampling programme to be implemented to ensure the risk to
public health could be fully assessed. NI Water needs to have its MIP supported by the
application of good operational procedures and that record keeping is carried out
robustly throughout the incident.
2. Alternative supplies
2.1 NI Water’s regulatory obligations regarding the provision of safe drinking water
supplies extends to water provided by the company in bottles or containers when there
is an interruption to normal piped supplies. In practice this means:
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water being used to fill tankers must meet the regulatory standards;
the containers, from which water is being provided, are not contaminated, whether
through the tanker material, the cleaning procedure, or through the filling process; and
as a further safeguard to protect public heath, any precautionary advice should be
given at the point at which the water is being made available to consumers.
2.2 As part of this incident management many static tanks were used to provide drinking
water supplies. In line with best practice it is important that static tanks are available in
‘ready to use state’. This will mitigate against potential contamination issues and to
assist deployment without unnecessary delays.
2.3 All tanks from which customers can take water should be clearly labelled with
appropriate ‘Boil Water Before Use’ signs to safeguard drinking water supplies, in
accordance with good industry practice. This standard precaution is aimed at informing
consumers of the need to safeguard against contamination introduced inadvertently by
them when drawing off water into household containers and during subsequent
storage and use. I note that, in the information NI Water has provided to the
Inspectorate regarding the incident, all tanks and standpipes were labelled with “Boil
Before Use” notices.
2.4 Tanks should only be filled by, or under the control of NI Water staff. NI Water
tankered water to water treatment works, service reservoirs and static tanks.
NI Water’s report to the Inspectorate of the incident refers to static tanks being filled by
councils and by the Northern Ireland Fire and Rescue Service. The Inspectorate has
not been provided with information to demonstrate what arrangements NI Water had in
place to ensure that any water being provided through the companies static tanks and
provided by third parties was wholesome. The Inspectorate required an assurance
from NI Water that appropriate arrangements were in place.
2.5 The Inspectorate has concerns in relation to how NI Water managed the risks
associated with the provision of alternative supplies involving ‘third parties’. The
Inspectorate recommends that NI Water undertake a review of how it can be assured
that, where in emergency situations when water is provided to consumers involving a
‘third party’, it has the necessary checks and procedures in place to enable it to
demonstrate to the Inspectorate, through appropriate records and evidence, that the
water supplied is wholesome.
2.6 Bottled water was made available from 27 December 2010 from the following sources:
NI Water’s emergency stock supply (100,800 litres);
two bottled water companies within Northern Ireland (261,238 litres); and
Scottish Water (459,840 litres).
Over 821,878 litres of bottled water were made available, of which, 411,878 litres were
distributed. Within the Incident Management Team, the Networks Operations Advisor
has overall responsibility for alternative supplies. The Alternative Supplies Task
Leader organises the distribution of bottled water supplies. Requirements for record
keeping purposes regarding water quality matters were managed by the Scientific
Advisor.
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3. Water treatment works performance
3.1 The following is a list of nine water treatment works where contraventions were
reported and events notified through normal reporting procedures during the period of
this incident. Further assessment of these events will be undertaken by the
Inspectorate through normal assessment and reporting procedures.
3.2 During the incident final water quality at nine works was affected in the short term and
where the standards were breached these were notified to the Inspectorate in
accordance with regulatory reporting requirements. These are listed below:
Cabragh / Gortlenaghan WTWs (iron and manganese);
Carmoney WTWs (turbidity);
Dorisland WTWs (aluminium);
Caugh Hill WTWs (turbidity);
Lough Macrory WTWs (aluminium);
Ballinrees WTWs (aluminium);
Dunore Point WTWs (aluminium);
Lenamore Springs WTWs (turbidity); and
Killylane WTWs (turbidity and aluminium).
A range of problems at the WTWs including: instrument faults; response to alarms;
freeze/thaw damage: effects of low temperature on the coagulation process; and
increased production, were all factors in one or more of these events.
4. Distribution networks / systems recovery
4.1 Throughout this incident there was significant disruption within the distribution network
caused as water mains burst requiring repair, as operational changes were made as
water was redistributed throughout the system or when water was re-introduced to
networks following restoration of supplies. Such operations would have caused
disturbance within the mains which may have led to water quality problems being
encountered in some areas. As part of good operational practice, it is the
Inspectorates opinion that NI Water should have robust procedures in place to
mitigate, as best it can, against any risks of contamination being introduced into the
distribution systems when undertaking these activities.
4.2 It is the Inspectorates opinion that, when a significant loss of supplies has been
experienced, a programme of water quality checks through an operational sampling
programme is necessary, and that such a programme should be related to the
assessment of the potential risks to public health. The monitoring programme is
necessary to verify that there has not been a breach of the integrity of the distribution
network such as may be caused by: multiple repairs of burst pipework and fittings;
valving operations; sediment disturbance when service reservoirs are being refilled
following significant depletion; and reintroducing water into the distribution network.
4.3 It is not evident from the information provided that such a programme was in place
during this incident. The Inspectorate is concerned that there appears to have been a
reliance on compliance monitoring, with no clear information available on any specific
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operational monitoring plan put in place during this incident. This has resulted in an
incomplete evidence picture being presented by NI Water to give me the necessary
assurance that risks were managed to protect public health. The Inspectorate also has
concerns on the potential of consumers to be exposed to contaminated water within
the distribution systems and what assessment NI Water had made to ensure
consumers were protected as supplies were being restored. It is therefore
recommended that NI Water reviews its operational monitoring plan to take account
of the specific circumstances which could be encountered during such emergency
situations and that such a plan should take account of the assessment of the potential
risks to public health.
4.4 NI Water has internal procedures for the repair of burst mains which detail the
necessary hygienic procedures required to be followed in undertaking repairs as well
as the requirement to obtain bacteriological samples at upstream and downstream
points on completion of the repair (with the exception of simple split collar repairs
where a positive pressure has been maintained throughout the repair and the
appropriate hygienic procedures have been followed).
4.5 The Inspectorate assessed the data provided in relation to the number of burst repairs
carried out by NI Water and the number of samples taken following such repairs. The
data returned to the Inspectorate details that there are a significant number (33%) of
bursts where the required sampling did not take place.
4.6 While NI Water’s current operating practices in relation to sampling after bursts are in
line with best industry practice, the Inspectorate is concerned that this was not
followed in all instances, in that not all burst repairs were sampled after the work was
completed. An assurance is required that the risk of water being supplied to
consumers during this incident was considered by NI Water. The Inspectorate
recommends that operational procedures in dealing with repairs in incident
emergency situations are reviewed in liaison with PHA and the Inspectorate.
4.7 In following best industry practice, and in compliance with NI Water’s ‘Section 1903:
Water Supply Hygiene Precautions’, staff or personnel involved in restricted operations
(i.e. work which may involve direct contact with fully treated water within WTWs or at
any stage in its distribution) should possess a current certificate of medical suitability
and have received appropriate training in hygiene procedures. It is NI Water’s
responsibility to ensure all staff involved in restricted operations has suitable medical
clearance and training. The Inspectorate recommends that NI Water review its
emergency procedures to ensure this requirement was met for those staff involved in
restricted operations.
4.8 Given the extent and nature of this incident, disruption to supplies would be
unavoidable in order to ensure consumers were placed back on supply as soon as
possible. NI Water should be assured that its operational procedures, where possible,
are planned and co-ordinated to ensure that the potential for ‘discoloured water’ issues
for consumers is kept to a minimum.
4.9 To ensure there was no adverse affect on water quality during refilling operations at
service reservoirs (particularly at levels

Inspectorate is not aware of any operational procedures which may have been in
place to reduce the impact of such filling operations or that a comprehensive sampling
plan was in place to ensure that the quality of water being further distributed was not
adversely affected. It is recommended that NI Water carries out a review of these
operational procedures.
4.10 The restoration of the distribution networks systems in this incident was complex
because of the unprecedented number of bursts. In restoring supplies there would be
a number of potential problems which should be taken into consideration and
assessed by NI Water such as:
valve operations within the distribution in order to restore and move water
throughout the network;
potential disturbance of mains sediment with any consequences considered for
water quality issues such as dirty water;
occurrence of possible airlocks; and
back siphonage issues especially from “high fluid risk categories” including dual
supplies (private water supplies).
The Inspectorate has not assessed NI Water’s response to the above points in detail
but requires an assurance from NI Water that these issues have been considered in
the management of this incident.
5. Regulatory Requirements of The Water Supply (Water Quality) Regulations
(Northern Ireland) 2007 as Amended
5.1 Regulation 4 - Wholesomeness
5.1.1 NI Water has a duty to provide wholesome water through its distribution network and
this duty also extends to water supplied by other means when alternative provision
arrangements are put in place by the water supplier, such as water made available to
consumers by bottled water and containers.
5.1.2 Regarding the quality of water supplied during the period of the incident, normal
reporting and assessment procedures apply to investigations of all contraventions.
The following 34 contraventions were notified to the Inspectorate:
21 at water treatment works - aluminium (7), turbidity (5), manganese (5); and
iron (4);
5 at service reservoirs - aluminium (2) and iron (3);
7 at customer taps - aluminium (6) and iron (1); and
1 at a static tank - turbidity.
5.2 Alternative supplies
5.2.1 Bottled waters: The information provided does not detail that test results were
available for all the bottled waters and, therefore, the Inspectorate is unable to assess
that all water provided was wholesome. From the information provided there is no
evidence to suggest that any water supplied through bottled water was unwholesome.
However the Inspectorate is concerned that no test results were provided for water
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supplied from one supplier over a four day period. It is recommended that NI Water
should ensure that appropriate records are kept to demonstrate that the water supplied
is wholesome.
5.2.2 Tankering and static tanks: In order to verify that water supplied from tankers and
static tanks is wholesome, there must be available evidence detailing that static
tankers are cleaned and disinfected before filling with a verified source of wholesome
water. In order for the Inspectorate to be assured of this, there must be in place
detailed records on each static tank which would provide such assurance.
NI Water advised the Inspectorate that static tanks were cleaned, disinfected, filled
with wholesome water and were lockable but the records provided do not contain
sufficient detail or cover all operations relating to the deployment of static tanks. The
Inspectorate has no evidence to confirm that the necessary precautions were carried
out. It is recommended that NI Water should review its procedures to ensure
complete records are maintained for each tanker and static tank to verify that water
supplied is wholesome.
5.2.3 Standpipes: Standpipes used in an emergency must be kept specifically for that use,
stored appropriately and cleaned and disinfected before use. Standpipes were made
available in eight locations. NI Water has stated that all standpipes were labelled “Boil
Before Use”.
5.3 Regulation 6 Monitoring: general provisions
5.3.1 NI Water has a duty under its monitoring requirements to put in place a schedule for
sampling where distribution within a water supply zone is through tankers. Regulations
6(3) and 6(4) contain the requirements for the frequency of sampling from tankers.
Regulatory guidance 1 defines tankers as any mobile water tank used to supply water
to consumers on a temporary basis. Tankers should only be filled with wholesome
water.
5.3.2 In order to demonstrate compliance with this regulation, NI Water must keep detailed
records as contained with the regulatory guidance on the deployment of each tanker
and static tank. Within the MIP there are logs to be completed when alternative supply
arrangements are put into operation. The documentation submitted as part of this
investigation does not provide the necessary details to allow a judgement to be made
on whether, on all occasions, this regulatory duty was complied with. It is
recommended that NI Water should review its record keeping, ensuring that it
contains sufficient detail for the deployment of all tankers and static tanks.
5.3.3 Where re-zoning is considered necessary as part of the operational practices in
managing the incident, an assessment should be made by NI Water to consider if any
adjustment is necessary to the routine statutory monitoring programme. Based on the
information provided, NI Water has stated that the re-zoning of water supplies was
covered by minor boundary changes. It is recommended that, where re-zoning is
being planned, an operational sampling plan is considered to cover any water quality
issues that may be caused by reversing flows etc.
1 Guidance on the Water Supply (Water Quality) Regulations (Northern Ireland) 2007
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5.3.4 The PHA advised NI Water on 31 December 2010 that there should be increased
monitoring at Clay Lake WTWs and enhanced monitoring in the distribution systems
and this was also to apply to other WTWs receiving tankered water. After this date,
Carran Hill WTWs was sampled daily and Clay Lake WTWs was sampled daily except
for 4 January 2011. However, Camlough WTWs was not sampled on the 1, 2 or 3
January 2011 and there were no additional distribution samples taken. The
Inspectorate requested an explanation as to why these additional samples were not
taken.
5.4 Regulation 15 Sampling: new sources
NI Water has a responsibility to ensure it has taken adequate precautions before
bringing sources into supply which are not currently in use. Regulation 15 requires NI
Water to put in place appropriate monitoring of any new source, either before bringing
in the source, or as soon as practicable afterwards. NI Water may, however, bring in
new sources as a matter of urgency in order to prevent an unexpected interruption in
supply, but this may only be done in circumstances where a regulation 27 risk
assessment has been carried out.
In bringing in the Cabragh and Glarryford boreholes, as these supplies had not been in
use for the preceding 6 months, NI Water was required to have undertaken monitoring
and a risk assessment. Appropriate monitoring was undertaken for these boreholes to
enable these supplies to be brought into service.
5.5 Regulation 16 Collection and analysis of samples
This regulation details specific requirements for the collection and analysis of samples.
The Inspectorate requires an assurance from NI Water that all personnel, including
contractors, who were taking samples during the incident, had been accredited to
undertake sampling or had undergone appropriate training, and that samples were
taken, handled and transported appropriately in compliance with this regulation.
5.6 Regulation 17 and 18 Investigations
Where NI Water has reason to believe that the water supplied fails, or is likely to fail,
to meet the standards of wholesomeness specified in the regulations, it is required to
investigate the cause of that failure or likely failure. Normal reporting and assessment
procedures apply to investigations of all contraventions. 34 contraventions were
notified to the Inspectorate under these regulations.
5.7 Regulation 26 Disinfection and other treatment arrangements
5.7.1 Regulation 26 requires NI Water to ensure that any disinfection process carried out at
any site is effective and that there is documented evidence to demonstrate verification
of the performance of the disinfection process. The regulation also requires that all
water supplied for Regulation 4(1) purposes (Wholesomeness) is disinfected.
5.7.2 No documentation was provided by NI Water to demonstrate verification of
disinfection. NI Water is required to meet the requirements regarding verification of
Page 7 of 9

the disinfection process as contained within DWI Information Letter 06/10. This should
form part of NI Water’s disinfection policy.
5.7.3 The Inspectorate has concerns that, in replenishing service reservoirs and in
recharging the distribution network during the incident, the chlorine demand may have
been affected within reservoirs and onward distribution. The Inspectorate requires
further information from NI Water into what controls were in place to ensure
disinfection was not compromised during this process.
5.8 Regulation 30 Application and introduction of substances and products
Regulation 30 specifies the circumstances in which NI Water may apply or introduce
substances or products into water supplies for cooking, drinking, food preparation or
washing. This includes water supplied in bottles or containers. The Inspectorate
requires an assurance that this regulation was met regarding all substances and
products utilised during the incident.
5.9 Regulation 33 Provision of information
5.9.1 Under regulation 33(6)(a) NI Water is required to notify the health authorities; every
appropriate district council; and DWI of an event which gives rise, or is likely to give
rise, to a significant risk to human health.
5.9.2 We have insufficient information to confirm when NI Water first contacted the Public
Health Agency in relation to this incident. The Inspectorate requires NI Water to
provide information to confirm that the PHA was contacted “as soon as possible” after
the event was declared.
5.9.3 In NI Water’s incident investigation report it states that notifications were made to the
25 district council areas affected; however there were no records provided to
document these notifications. The Inspectorate requires NI Water to maintain a
comprehensive event log to demonstrate that the appropriate contacts were made.
5.9.4 The Inspectorate acknowledges the substantial information provided by NI Water from
27 December 2010 on a daily basis until the end of the incident including regular
updates of the overall situation via the “Upward Reports”.
5.9.5 There are circumstances where NI Water takes advice from the PHA and restrictions
or precautionary restrictions are put in place by the company to protect public health in
matters relating to drinking water quality. Following communications between NI Water
and the PHA, general ‘Boil Water Before Use’ advice was made available through the
PHA’s website on 29 December 2010; however it was not made available on NI
Water’s website until 31 December 2010.
5.9.6 It is the Inspectorate’s opinion that there was not sufficient information made available
to the public in those areas where mains were being repaired. Consumers should
have been made aware, for example, that temporary discolouration may be
experienced as supplies are reconnected and restored to normal operations. They
should also have been advised whether there was a need to take any precautionary
measures such as boiling the water before use. It is recommended that NI Water
Page 8 of 9

takes into consideration a review of this aspect of consumer communications within
the work currently being undertaken by a sub group of the Drinking Water Liaison
Group that is providing guidance to health professionals and those in the water
industry in Northern Ireland.
5.9.7 NI Water advised the Inspectorate that the Drinking Water and Health Guidance
Document should be reviewed to include lessons learnt dealing with this incident and
the provision of health advice to customers. It is recommended that operational
procedures should be reviewed and taken into consideration in the work currently
being undertaken by the DWLG sub group. This review should reflect best water
industry practice.
6. Water unfit for human consumption
6.1 NI Water is required to provide the Inspectorate with data relating to the complaints
and concerns of its consumers. During the period of this incident the company has
reported that there were 47 contacts made relating to the appearance of ‘black/brown/
orange’ coloured water. Due to the unprecedented number of contacts being made to
the company’s call handling centre, the Inspectorate is aware that only a percentage
of incoming calls were answered. It is therefore impossible to know what percentage
of calls, not getting through, were to make complaints or express water quality
concerns. As the company has not provided sufficient information to demonstrate that
all calls were correctly categorized, the Inspectorate cannot establish an accurate
picture of what customers were experiencing.
6.2 It is possible that some consumers may have rejected their water supply for drinking,
cooking and other domestic purposes when supplies were restored. In considering the
information provided by NI Water, there is a lack of sufficient reliable evidence that the
company supplied water that was unfit for human consumption.
6.3 It is recommended that the information recording procedures are reviewed to enable
NI Water to ensure that all contacts, whether complaints or concerns, are categorized
and recorded robustly particularly during incident situations.
7. Other matters
The Inspectorate, during the period of this investigation, notes that a ‘level 3’ incident
was declared on 17 December 2010 and that tankering to service reservoirs from 12
December 2010 to 13 January 2011 was ongoing. The Inspectorate was not notified
when this initial tankering operation commenced on 12 December 2010. It is the
Inspectorate’s opinion that NI Water should contact DWI as soon as it is aware of a
notifiable problem, or a developing situation, which might become notifiable. In
circumstances where tankering is commenced to service reservoirs, this would be
notifiable.
COLIN CLEMENTS
Operations Inspector
17 May 2011
Page 9 of 9

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Alternative Supplies
3.2.4 DWI requires an assurance from
NI Water that appropriate
arrangements are in place to ensure
that any water being provided through
the company’s static tanks and
provided by third parties is wholesome.
This issue will be
considered as part of the
Major Incident Plan (MIP)
review. DWI to be
informed when the review
is completed.
Insufficient information
has been recorded by NI
Water to allow a full
assessment to be made in
relation to third parties
providing water through NI
Water’s static tanks. DWI
notes that NI Water will
consider this issue as part
of its MIP review.
NI Water to provide an update
of the relevant section of the
MIP when it is completed.
In the interim, NI Water
should ensure it adheres to
Water UK Technical
Guidance Note No. 12
regarding tankers, static tanks
and bowsers.
Action status: Ongoing, NI
Water to provide review
progress update at
NIW/DWI AMD Meeting 22
June 2011
1 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Distribution Networks / Systems
Recovery
3.4.5 DWI requires an assurance that
the risk of supplying water to
customers during the incident was
considered, and recommended that
operational procedures were reviewed
in liaison with Public Health Agency
(PHA) and the Inspectorate.
Assurance given
regarding risk
assessments and
refers to mitigation
measures. To be raised at
the next meeting of the
interagency Drinking
Water Liaison Group
(DWLG).
NI Water did not provide
sufficient detail as to how
the assessment of risk
was fully considered.
Reliance on compliance
samples and the limited
operational samples taken
during the period of the
incident was in DWIs
assessment insufficient to
enable a full evaluation of
the risks to be considered.
These were not normal
operating conditions and
for example sampling
downstream following
repair several days later
(or not at all) would not
fully inform the risk of
potentially contaminated
water being present for
consumers.
NI Water to outline its
procedures on its assessment
of the risk of supplying
unwholesome water during an
incident taking account of its
assessment of how this could
constitute a danger to public
health. This update to be
provided at the next meeting
of the DWLG in June 2011.
Action status: Ongoing
2 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Distribution Networks / Systems
Recovery
3.4.6 DWI recommended that NI
Water reviewed its emergency
procedures regarding the medical
screening and hygiene training of staff
involved in restricted operations.
All NI Water and
Contractor’s employees
carrying out work in
restricted operations must
be registered under the
National Water Hygiene
Scheme and carry the
card. This will be
considered as part of the
MIP review and DWI
informed when the review
is completed.
DWI accepts the
assurance that all NI
Water and Contractor’s
employees must be
registered under the
National Water Hygiene
Scheme and carries the
card.
NI Water to provide an update
of the relevant section of the
MIP when it is completed.
Action status: NI Water to
provide review progress
update at NIW/DWI AMD
Meeting 22 June 2011
3 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Distribution Networks / Systems
Recovery
3.4.8 DWI recommended that NI
Water reviewed its operational
procedures regarding tankering into
service reservoirs including operational
monitoring.
NI Water follows good
operational practice during
filling operations. Routine
compliance monitoring
was carried out. Suggest
we discuss with DWLG
and incorporate into
Guidance Document for
Water and Health
Professionals.
DWI’s opinion is that
routine compliance
samples are not sufficient
when there is significant
operational work ongoing.
A comprehensive
programme of water
quality checks through a
robust operational
sampling programme is
required.
NI Water to outline its
proposals regarding
mitigation of the risk of
tankering into service
reservoirs at the next meeting
of the DWLG in June 2011.
Action status: Ongoing
3.4.9 DWI required an assurance
regarding the restoration of supplies
and the potential impact on water
quality.
NI Water carry out
continual risk
assessments on the
possible impacts of
networks operations on
water quality.
NI Water did not provide
sufficient detail as to how
the assessment of risk
was fully considered.
Reliance on compliance
samples and the limited
operational samples taken
during the period of the
incident was in DWIs
assessment insufficient to
enable a full evaluation of
the risks to be considered.
NI Water to outline its
proposals regarding the risk
assessment process
at the next meeting of the
DWLG in June 2011.
Action status: ongoing
4 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulatory Requirements
Alternative Supplies
4.2.1 DWI recommended that
appropriate records are kept to
demonstrate bottled water supplies are
wholesome.
NI Water is currently
reviewing its bottled water
procedure to ensure
appropriate records are
maintained in the future.
DWI notes that a review of
bottled water is being
undertaken by NI Water.
NI Water to provide details of
the review being carried out
within 4 weeks of the date of
this letter.
Action status: Ongoing
4.2.2 DWI recommended that NI
Water should review its procedures to
ensure complete records of cleaning,
disinfection and filling of tankers and
static tanks and locking of static tanks
are maintained.
NI Water will consider this
as part of the MIP review.
DWI notes that record
keeping relating to tankers
and static tanks will be
considered as part of the
MIP review.
NI Water to provide an update
of the relevant section of the
MIP when it is completed.
Action status: Ongoing, NI
Water to provide review
progress update at
NIW/DWI AMD Meeting 22
June 2011
5 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulation 6 Monitoring: General
Provisions
4.3.2 NI Water’s record keeping
regarding the deployment of each
tanker and static tank were insufficient
to demonstrate compliance with
Regulation 6, and DWI recommended
NI Water reviewed its record keeping.
NI Water will review its
record keeping
procedures to ensure a
complete record of tankers
and static tanks exists.
DWI notes that a review is
being undertaken.
NI Water to provide details of
the review being carried out
within 4 weeks of the date of
this letter.
Action status: ongoing
4.3.3 DWI recommended where rezoning
is being planned, an operational
sampling plan is considered.
NI Water will consider
increased monitoring in
the distribution system
during major boundary
change operations
through a risk based
approach.
DWI notes that NI Water
will use a risk-based
approach to operational
sampling when re-zoning
occurs.
In any future event, NI Water
must ensure that adequate
operational sampling is
carried out.
Action status: no further
action required
6 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulation 6 Monitoring: General
Provisions
4.3.4 DWI requested an explanation
as to why the additional samples
requested by the PHA at Camlough
WTWs were not taken.
NI Water advised that this
was an oversight by the
company.
DWI accepts that this was
an oversight.
In any future event, NI Water
must ensure that any
additional operational
sampling requested by PHA
is carried out.
Regulation 16 Collection and
Analysis of Samples
Action status: No further
action required
4.5 DWI required an assurance that all
personnel taking samples during the
incident were accredited.
All samples were taken by
SERCO who are UKAS
accredited.
DWI accepts the
assurance given.
Action status: No further
action required
7 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulation 26 Disinfection and
Other Treatment Arrangements
4.7.3 DWI required further information
as to what controls were in place to
ensure disinfection was not
compromised when service reservoirs
were being replenished.
NI Water gives an
assurance that public
health is its primary
concern and operational
practices were closely
monitored to minimise
potential water quality
impacts. Chlorine
residuals were monitored
closely.
No documentation was
provided by NI Water to
demonstrate verification of
disinfection.
NI Water is required to meet
the regulatory requirements
regarding verification of the
disinfection process and
outlined within DWI
Information Letter 06/10. This
should form part of NI Water’s
disinfection policy. NI Water
to provide a timeframe for full
implementation of the
requirements of I/L 06/10
within 4 weeks of the date of
this letter.
Action status: ongoing
8 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulation 30 Application and
Introduction of Substances and
Products
4.8 DWI required an assurance that
Regulation 30 regarding substances
and products was met for all
substances and products utilised
during the incident.
Statement of assurance
given by NI Water that all
equipment used during the
incident complies with the
regulation.
Supporting evidence is
required to provide DWI
with the necessary
assurance.
NI Water to provide
information on the
specification of emergency
equipment utilised during the
incident to include tankers
and static tanks within 4
weeks of the date of this
letter.
Action status: ongoing
Regulation 33 Provision of
Information
4.9.2 DWI required an assurance that
PHA was contacted “as soon as
possible” after the event was declared;
and that NI Water maintain a
comprehensive log of notifications.
A council liaison officer
was established at the
Westland Gold Command
Centre to provide the
councils with information.
NI Water’s response does
not provide the necessary
detail regarding contact
with the PHA.
NI Water should review its
contact arrangements with
PHA and its maintenance of
notification records. NI Water
should provide outline
proposals at the next meeting
of the DWLG in June 2011.
Action status: ongoing
9 of 10

Annex 2
DWI FINAL ASSESSMENT SUMMARY - ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN
IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
DWI Requirement/ Recommendation
in Initial Assessment Letter of
4 March 2011
Summary of NI Water
Response received
1 April 2011
DWI Assessment of
NI Water Response
Further Action Required
Regulation 33 Provision of
Information
4.9.6 DWI recommended that NI
Water considers customer
communications as part of the DWLG
sub-group preparing a guidance
document for water and health
professionals; and that operational
procedures should be reviewed and
considered by this group.
NI Water has now updated
the website on Repairs
and Interruptions to
include information
regarding discoloured
water etc. NI Water will
take forward the aspect of
customer communications
with the DWLG sub-group.
DWI notes that NI Water
will progress this issue
through the DWLG subgroup.
NI Water to progress this
issue through the DWLG subgroup.
Action status: ongoing
Water Unfit for Human Consumption
5.3 DWI recommended that NI Water
reviewed its recording procedures
regarding customer contacts, to ensure
all contacts are categorised and
recorded robustly.
NI Water uses a number
of key recording codes, in
conjunction with call
handler scripts, to record
customer contacts. NI
Water plans to roll out a
training programme for
volunteer call handlers.
Due to the communication
difficulties caused by the
high level of customer
contact, NI Water was not
able to robustly categorise
and record all customer
contacts.
System of customer contacts
should be reviewed for
suitability in emergency
situations.
Action status: ongoing
10 of 10

ADVERSE WEATHER INCIDENT AFFECTING SUPPLIES ACROSS NORTHERN IRELAND, 27 DECEMBER 2010 – 6 JANUARY 2011
SUMMARY TABLE OF EVENTS AT WATER TREATMENT WORKS (WTWS) DURING THE ADVERSE WEATHER INCIDENT
Annex 3
WTWs
Cabragh /
Gortlenaghan @
Cabragh
Dates
28/12/10 – 05/1/2011
(8 days)
Parameter
Failures
Manganese and
Iron in final water
Probable Cause
Requirement to bring Cabragh Borehole back into service as an emergency supply
due to sufficiency issues. There are naturally high levels of iron and manganese
present in this emergency water source.
Carmoney 28/12/10
(1 day)
Dorisland 29/12/10 – 04/01/11
(6 days)
Caugh Hill 29/12/10 – 03/01/11
(5 days)
Lough Macrory 29 /12/10 – 03/01/11
(5 days)
Ballinrees 29/12/10
(1 day)
Dunore Point 02/01/11 – 05/01/11
(3 days)
Lenamore Springs 04/01/11 – 07/01/11
(3 days)
Killylane 06/01/11 – 10/01/11
(4 days)
Turbidity in final
water
Aluminium in final
water & customer
tap samples
Turbidity & Iron in
final water
Aluminium in final
water
Aluminium in final
water
Aluminium in final
water & customer
tap samples
Turbidity in final
water
Turbidity and
Aluminium in final
water and in the
distribution system.
The very low level in the clear water tank led to an air lock which caused disturbance
in the sample line resulting in an unrepresentative sample.
Instrument malfunction caused problems with pH control which affected the
coagulation process. Critical process monitoring point failure resulted in a delay in
the problem being reported and investigated. This was compounded by the works
being unmanned over the holiday period, so manual tests were not carried out. The
breakdown in treatment went undetected and therefore corrective action to restore
water quality was delayed.
Instrument malfunction caused problems with pH control which affected the
coagulation and filtration processes.
The low temperatures affected the coagulation process, and this was compounded
by a number of temporary shutdowns at the works caused by problems with the
power supply.
Lime dosing pump failure caused problems with pH control which affected the
coagulation and filtration process.
Breakdown of the coagulation process due to Freeze/Thaw damage to the ‘‘dirty
wash-water” system which caused increased aluminium levels being introduced at
the head of the works.
Tankering operations into the holding tank, which were necessary because of
sufficiency issues caused particle disturbance.
Breakdown of the coagulation process after the primary coagulant had been
changed as part of ongoing operational work at this works.