water safety plan (wsp)€¦ · team leader 3 waters santha agas team leader water supply dean...
TRANSCRIPT
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Water Safety
Plan (WSP)
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288.01 2
Contents
1. Revision Details ................................................................................................................... 4
2. Introduction .......................................................................................................................... 5
3. Supply Details ...................................................................................................................... 6
4. Description of the Napier City Drinking-water Supply .................................................... 10
5. Photographs of Napier City Water Supply ....................................................................... 15
6. Flow Chart/Schematic of the Supply ................................................................................ 16
7. Supply Schematic .............................................................................................................. 16
8. Barriers to Contamination ................................................................................................. 17
9. Improvement Schedule ..................................................................................................... 17
10. Benefits of Proposed Improvements ................................................................................ 20
11. Methodology ...................................................................................................................... 20
12. Risk Ranking Procedure.................................................................................................... 21
13. Drinking Water Standards and Grading ........................................................................... 23
14. Consultation ....................................................................................................................... 24
15. Contingency Plan............................................................................................................... 25
16. Risk Tables ......................................................................................................................... 28
Figures
Figure 1. Coverdale borehead in chamber .................................................................................... 15
Figure 2. Coverdale electrical control cabinet ................................................................................ 15
Figure 3. T6 bore chamber and cabinet (typical bore arrangement) .............................................. 15
Figure 4. T5 bore chamber and control cabinet ............................................................................. 15
Figure 5. Taradale reservoir .......................................................................................................... 15
Figure 6. Hatch on Enfield reservoir .............................................................................................. 15
Tables
Table 1. Summary of the Napier City water supply details .............................................................. 6
Table 2. Critical points .................................................................................................................. 17
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Table 3. Improvement Plan ........................................................................................................... 18
Table 4. Likelihood Scale .............................................................................................................. 21
Table 5. Consequence Scale ........................................................................................................ 21
Table 6. Risk Level Allocation Table ............................................................................................. 22
Table 7. Summary of Compliance with DWSNZ ............................................................................ 23
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1. Revision Details
Version No Description Approved Revision Date
V1.0 Prepared by BTO 17.08.10. Approved by DWA 2010 30/11/12
V2 Prepared by NCC staff with input from BECA December 2016 01/01/2020
This plan will be revised and submitted for approval before 1 January 2020.
Assessment of the performance of the plan
Assessment of the performance of the plan will be undertaken annually. The assessment will
consider any events, non-compliances, near misses and unexpected situations that have occurred,
progress against the improvement schedule and any changes to any of the supply elements. Any
matters requiring attention will be included into the Annual Plan, the Asset Management Plan for
Water Supplies and if requiring significant capital funding, the Council Long Term Plan.
Reporting of the plan
A brief report on the performance of the plan, including information from the assessment of the
plan will be provided by the Team Leader 3 Waters to the Manager Asset Strategy, annually on the
anniversary of finalisation of the plan. The report will cover the items listed above in the
assessment of the performance of the plan. The Water Supply Asset Manager will be responsible
for ensuring that any matters requiring attention will be appropriately included into the Annual Plan
or the Asset Management Plan for Water Supplies. If significant capital funding is required the
Works Asset Manager will include the matter into the Council approval process and the Council
Long Term Plan.
Links to other quality systems
This Water Safety Plan (WSP) will be linked to the Annual Plan, the Asset Management Plan for
Water Supplies and the Council Long Term Plan.
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2. Introduction
This WSP has been prepared for the Napier drinking-water supply to identify potential events that
present public health risks to the consumers of the drinking water supply. Napier City Council is
committed to the WSP and to the future improvements to the supply that have been identified in
this WSP.
The Napier drinking water supply is a large urban supply providing water to two communities,
Napier and Bayview. The total population that is supplied is approximately 50,800 people. The
water is sourced from a local aquifer, and is provided without treatment to both communities.
The scheme is administered at the main council offices on Hastings Street, Napier and operated
and managed by the Councils Works Asset Management and Services Groups. The management,
maintenance and operation of the Napier Water Supply are the responsibility of:
Director Infrastructure (Jon Kingsford)
Director Services (Lance Titter)
Manager asset Strategy (Chris Dolley)
Team Leader 3 Waters (Santha Agas)
Team Leader Water Supply (Dean Hammond)
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3. Supply Details
The Napier City drinking-water supply comprises two communities, Napier and Bayview. Both
communities are supplied with secure groundwater from a number of bores and pump stations.
The Napier community has two distribution zones, Napier City and Taradale. The Bayview has only
one distribution zone, Bayview. Most of the bores supply both communities through an extensive
network, however the A1 Awatoto Bore and pump station supplies only the Napier community. The
Ministry of Health registration details are set out in the table below with some further relevant detail
about each source.
Table 1. Summary of the Napier City water supply details
Community Details (Napier community)
Supply Name Napier
WINZ Community Code NAP001
Supply Owner Napier City Council
Manager Asset Strtaegy Chris Dolley
Director Services Manager Lance Titter
Team Leader 3 Waters Santha Agas
Team Leader Water Supply Dean Hammond
Population Served by Supply 49,910 (WINZ register 2015)
Community Details (Bayview community)
Supply Name Bayview
WINZ Community Code BAY001
Supply Owner Napier City Council
Manager Asset Strtaegy Chris Dolley
Director Services Manager Lance Titter
Team Leader 3 Waters Santha Agas
Team Leader Water Supply Dean Hammond
Population Served by Supply 894 (WINZ register 2015)
Consent Details
Resource consent Number WP 060658TA
Consented quantity Consent covers take from all of the bores supplying Napier and Bayview. It allows 784L/s, 67738m
3/day, 387,744m
3/7
days and 55,392m3 per day over a 7 day period.
Source and Plant Details (Napier community only)
Source Name A1 Awatoto Bore
Source WINZ Code G02037
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2845712 Northing : 677740
Plant Name A1 Awatoto Pump Station
Plant WINZ Code TP03097
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Location (A1) Road reserve cnr Awatoto & McLeod Roads
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name Bledisloe Park Bore
Source WINZ Code G00062
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2841040 Northing : 6178391
Plant Name Bledisloe Park
Plant WINZ Code TP00105
Location (T2) Bledisloe Park
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name Burness Road Bore
Source WINZ Code G00061
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2841921 Northing : 6178720
Plant Name Burness Road
Plant WINZ Code TP00106
Location (T1) Road reserve Burness Road
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name Cloverdale Bore
Source WINZ Code G00067
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2844053 Northing : 6180574
Plant Name Cloverdale Pump Station
Plant WINZ Code TP00111
Location (C1) Cloverdale St
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name Guppy Road Bore
Source WINZ Code G00064
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2841570 Northing : 6177913
Plant Name Guppy Road
Plant WINZ Code TP00103
Location (T5) Road reserve Guppy Road
Treatment Processes Secure ground water
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Source and Plant Details (Napier and Bayview communities)
Source Name Riverside Park Bore
Source WINZ Code G00065
Type of Source Bore
Grid Reference of Source (NZTM) Easting : 2840344 Northing : 6177098
Plant Name Riverside Park
Plant WINZ Code TP00102
Location (T3) Riverside Park
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name T4 Bore Napier
Source WINZ Code G00063
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2842048 Northing : 6179482
Plant Name T4 Pump Station
Plant WINZ Code TP00104
Location (T4) Gloucester Street
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name T6 Bore
Source WINZ Code G01151
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2841390 Northing : 6177111
Plant Name T6 Pump Station
Plant WINZ Code TP01961
Location (T6) Road reserve Guppy Road
Treatment Processes Secure ground water
Source and Plant Details (Napier and Bayview communities)
Source Name T7 Bore, King Street
Source WINZ Code G01395
Type of Source Bore
Grid Reference of Source (NZMG) Easting : 2841297 Northing : 6178066
Plant Name T7 Pump Station, King Street
Plant WINZ Code TP02308
Location (T7) King Street
Treatment Processes Secure ground water
Distribution Zone (Napier community)
Distribution Zone Name Napier City
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Distribution Zone WINZ Code NAP001NA
Distribution Zone Population 25,800 (WINZ register 2015)
Distribution Zone (Napier community)
Distribution Zone Name Taradale
Distribution Zone WINZ Code NAP001TA
Distribution Zone Population 24,110 (WINZ register 2015)
Distribution Zone (Bayview community)
Distribution Zone Name Bayview Township
Distribution Zone WINZ Code BAY001BA
Distribution Zone Population 894 (WINZ register 2015)
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4. Description of the Napier City Drinking-water Supply
The first community water supply for Napier City was commissioned in late 1877 and utilised water
from a bore located in what is now the central business district. The 1931 earthquake considerably
changed the geography of the Napier, elevating areas that had been underwater and providing
considerable further areas for development. The water supply has continued to rely on
groundwater bores and in 1968 when the Taradale Borough was amalgamated with Napier City the
public drinking-water supply was extended to that area. Aesthetically high quality groundwater in
the Taradale area was utilised with the first bore drilled in the mid-1970s and six more since. Bores
closer to Napier City with lower aesthetic quality were progressively decommissioned as more
supply capacity from Taradale was constructed. Trunk mains, booster pump stations and
reservoirs have subsequently been constructed to provide consistent pressures and security of
supply as development has continued.
The Bayview area was amalgamated with Napier in 1989. Bayview had been reticulated during the
early 1960’s, with the supply from a bore on the northern bank of the Esk River. This water was of
poor aesthetic quality and in 1988 the Tannery Road bore and pump station was established and a
14 km pipeline was installed to supply the area. In 1998 the Bayview area was connected to the
Napier City supply.
Today Napier City’s water supply system consists of two distinct supply areas or communities, the
Napier Community (NAP001) and the Bayview Community (BAY001). The Napier community
includes two distribution zones, Napier City (NAP001NA) and Taradale (NAP001TA). The Bayview
community has only one zone, Bayview (BAY001BA). Both include water supply to urban and rural
areas. 95.5% of Napier’s population is serviced by reticulation system and 9.8 million m3 of water is
consumed annually.
Groundwater is abstracted from the Heretaunga Plains aquifer and supplied to pressure zones
within the two community systems via bore pumps, reservoirs and pump stations.
The system comprises:
10 groundwater bores (8 in operation)
10 ground water and 8 booster pump stations
8 reservoir sites
471 km pipe mains
The bores have been drilled to depths of between 40 and 90 metres and are screened for the
bottom three to nine metres. They flow under artesian pressure, but bore pumps are used to
provide the pressures required in the reticulation system. Two reservoirs, Enfield (11,000m3) on
Hospital Hill and Taradale (92oom3), located at an elevated site behind Taradale, are filled from the
reticulation system and provide storage to balance demand. Both reservoirs have the same top
water level so operate in unison. The reservoir levels control the bore pump stop/start. The Enfield
and smaller Thompson reservoir supply the bulk of the water to consumers in the Napier zones,
particularly the flat part of the city. The Taradale reservoir supplies water to the Taradale zone. A
second 9200m3 reservoir is proposed for Taradale.
A number of smaller reservoirs or pump stations supply consumers in elevated locations. Seven
booster pump stations in the Napier zones are used to transfer water to more elevated pressure
zones. Six of the booster stations use water from the Enfield reservoir and a seventh is supplied
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from the Thompson reservoir. An eighth booster station, Church Road Booster is used to increase
the supply capacity of the source pumps within the Enfield reservoir system by fully utilising the
pressure capacity of the Tamatea trunk main.
Water is taken from a trunk main in the Napier system and pumped to the Bay View zone. Bayview
has in the past been supplied by the dedicated Tannery Bore as well, but supply from this bore has
recently been discontinued.
Eleven storage tanks on eight sites provide the storage required to balance peak demand and
meet firefighting and other emergency requirements throughout the zones. At strategic points in
the system, pressure control valves are used to maintain reticulation pressure within desirable
operational limits by utilising the higher pressure available in adjacent pressure zones or from
pumping trunk mains.
Approximately 471km of water mains ranging in diameter from 50mm to 450mm distribute water to
consumers.
Groundwater age dating for all of the bores has shown the water to have been underground for
considerably longer than 12 months and ‘secure’ status under the DWSNZ has been
demonstrated. Water residence time for the bores ranges from 14 years to 99 years but typically is
about 40 years. The age dating process was recently completed in 2014.
The bores are installed below ground level in sealed chambers. This arrangement has been
assessed under the requirements of the DWSNZ (section 4.5.2.2) and determined to meet bore
water security criterion 2, provision of satisfactory borehead protection. The bore chambers include
sump pumps and alarms to alert the operators should flooding of the chambers occur.
The bores are continuously monitored for pump performance, pressure and flow. Data is
telemetered to the Council office and alarmed to the operators.
Supply with potable groundwater means that treatment of the source water has not been required,
significantly influencing the way the water supply system has developed. As urban development
spread south, so too did the reticulation network. Additional bores and pump stations were easily
installed where development occurred. Most of the pump stations pumped directly into the
reticulation system since the water was not required to be conveyed any great distance from
source to the consumer. The required trunk main infrastructure was minimal and generally located
to service areas remote from the aquifer. In the Napier City area, this approach meant that, all the
bores and pump stations were located in an area of the aquifer which had poor aesthetic quality.
Since the amalgamation with Taradale Borough, the original development strategy was discarded
in favour of developing a pumping and distribution trunk main infrastructure that takes advantage of
the better quality water in the Taradale area.
Prioritising use of good quality water from the Taradale area has resulted in high but fluctuating
pressures in much of the network, particularly Taradale and contributed to an increased risk of pipe
failure and consumer complaints. Since 1995 a number of pumping trunk mains have been
installed to separate the bulk supply and distribution functions of the network.
Soil properties in the area where pipes have been installed varies depending on whether or not it
was submerged prior to the earthquake. This variation influences the performance of metallic pipes
and fittings with some areas less prone to corrosion than others. This is an issue which Napier City
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Council manages through an asset management system which utilises Accela asset management
software.
A hydraulic model of the reticulation network was developed more than ten years ago and is
maintained by the Water Supply Asset Manager. The model is used to identify capacity issues,
pipe renewal options, effects of development, levels of service, the impact of shutdowns and
tracing water source and age in the network. The supply as it is now configured supplies a
consistently high aesthetic quality water throughout the city at constant pressure.
Regular flushing of the network is not required as demand means that ‘fresh’ water is maintained
within the system. The removal, over time of network dead ends has contributed to this. Flushing is
undertaken if a need is demonstrated. Mains cleaning is undertaken with ‘pigging’. Approximately
20% of mains are cleaned in this way annually.
Backflow within the reticulation system is managed through a comprehensive programme. All
premises, existing and new, in industrial zoned land are required to have at least a testable double
check valve if the hazard is assessed as medium or lower. RPZ’s are required at any site that is
assessed as having a high hazard. All backflow devices are installed at the boundary regardless of
any devices that are installed within buildings on the site. Any other sites that present a backflow
risk are picked up when a land use or building use change is made. Any other sites that Council
considers to be a risk is required to have a testable backflow device installed. The type of backflow
devices required is determined by the activity on the site and the risks that relate to that activity. All
backflow devices are tested annually by Council.
Any new residential properties have manifolds with check valves installed and Council has an
extensive programme underway to replace all service connections with check valve manifolds.
The reticulation network consists of 471 kms of mains with a range of pipe types and sizes,
including asbestos cement (39%), PVC (33%), CI (17%), PE (4.6%), ST (3.6%) and other minor
lengths of ductile iron, ABS and unknown pipe materials. A 2014 Asset Management Lifecycle
Review Report concluded that there was no indication of a water system renewal backlog and the
operational service history provided no indication of any major service delivery issues with the
water network
DWSNZ compliance is demonstrated against section 4.3.1, compliance criteria 1 for water leaving
the treatment plants and section 4.4.1, compliance criteria 6A for water in the distribution zones.
Both of these compliance criteria rely on the analysis of E. coli in the water samples. Each bore is
sampled monthly (DWSNZ treatment plants) and more than 50 samples are collected each month
from the distribution zones. This is more than 150% greater than the minimum required by the
DWSNZ. Analyses is undertaken at the Napier City Council laboratory. This laboratory is Ministry
of Health recognised for the analyses it undertakes.
In the event of an extended power outage, the reservoirs can provide up to 24 hours of supply.
Elevated areas that are pumped are supplied with water in the event of a power outage, but with
considerably reduced pressure.
The system is relatively simple because it does not require any water treatment, but it is not
simplistic. It is fully is automated and effectively operates itself. There are however inherent
complexities that arise from the number of bores suppling the network, the way the bores are
spread across the network and the size and extent of the system.
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Council manages the operation and maintenance of all aspects of the supply. Council also
operates and manages the City wastewater system but keeps all aspects of the systems separate,
including staff and equipment. Council engages consultants or contractors to undertake specific
tasks as required.
Though source water is abundant and the costs of operating the supply are comparatively low,
Council undertakes a year round water conservation programme aimed at minimising demand.
This is intended to ensure that only infrastructure that is required is installed and to promote a
responsible and informed approach to water use amongst consumers. The supply fully complies
with the DWSNZ.
Summary of Water Sampling
E.COLI MONITORING FREQUENCY OF NAPIER CITY COUNCIL RETICULATION PER QUARTER
Zone
Minimum number of samples required by
Drinking Water Standards
Typical number of samples
actually collected
Maximum interval between samples (days)
Minimum number of days
of the week used
Napier City 28 54 6 7
Taradale 28 57 6 7
Bay View 13 33 11 5
E.COLI MONITORING FREQUENCY OF NAPIER CITY COUNCIL BORES PER QUARTER
Bore
Minimum number of samples required by
Drinking Water Standards
Minimum number of
samples actually collected
Maximum interval between samples (days)
Minimum number of days
of the week used
All secure bore water supplies
1 3 45 3
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5. Photographs of Napier City Water Supply
The following photos were taken on a site visit to the Napier City supply on17 July 2015.
Figure 1. Coverdale borehead in chamber Figure 2. Coverdale electrical control cabinet
Figure 3. T6 bore chamber and cabinet (typical bore arrangement)
Figure 4. T5 bore chamber and control cabinet
Figure 5. Taradale reservoir Figure 6. Hatch on Enfield reservoir
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6. Flow Chart/Schematic of the Supply
The following schematic provides a representation of the type of supply provided at Napier City. It
is not accurate in terms of the number or location of the bores or reservoirs etc. but is intended to
highlight the critical points and barriers relevant to this type of supply.
7. Supply Schematic
Critical
point 1
Critical
point 2
Barrier:
Reservoir is
covered to prevent
ingress of rainwater
or contaminants
and to exclude
birds and vermin
providing a partial
barrier to re-
contamination.
Napier City
distribution
zone
Storage
reservoir
Critical
point 3
Barrier: Secure
groundwater is not
contaminated with
micro-organisms
Secure bore
water sources
Storage
reservoir
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8. Barriers to Contamination
Table 2. Critical points
Critical points where hazards can be eliminated, minimised or isolated include:
Critical Point Description
1. Groundwater bores Bore or bore pump failure may result in a loss of source water to a part of the supply. Infiltration of surface water into the bores can compromise water quality
2. Treated water storage Possible point for microbiological contamination
3. Distribution system connections
Possible access point for contamination due to backflow
Existing barriers to contamination include:
1. Secure Groundwater Bores
A network of groundwater bores with sanitary boreheads that have been demonstrated to be
‘secure’ under the DWSNZ provide water that is not contaminated with micro-organisms providing
a barrier to microbiological contamination.
2. Prevention of contamination of treated water in storage
The reservoir is covered to prevent unauthorised access, ingress of rainwater or contaminants, and
to exclude birds and vermin. This contributes to the provision of a partial barrier against re-
contamination of water following abstraction.
9. Improvement Schedule
The improvement schedule outlines improvements that have been recommended for preventing,
reducing or eliminating the identified public health risks in the Napier drinking water supply.
Possible improvements to the water supply have been identified in the ‘Additional Measures That
Could Be Put in Place’ column of the risk tables. The most suitable option to improve the
management of each unmanaged risk has then been included in the improvement schedule. It
should be noted that costs are estimates only. Each project is ranked according to the priority to
which projects should be completed. All improvements are dependent on Council priorities,
affordability and Council statutory budget approval processes.
MAS – Manager Asset Strategy
DCS – Director City Services
TL3W – Team Leader 3 Waters
MEM – Manager Environmental Monitoring
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Table 3. Improvement Plan
Action no.
Risk level following
improvements
Water Supply area
Reference to risk table
Proposed works Person responsible
Expected cost Intended completion
date
1 Medium Catchment, Bores,
Reticulation
NS1.1, NS1.2, NS1.3
NS1.4, NS1.5,
Develop contingency plans MSA Staff time December 2017
2 Medium Catchment NS1.1 Catchment investigation MSA $10,000 December 2017
3 Medium Catchment NS1.1 and NS1.2
Increase water aging testing MSA $1,000 On going
4 Medium Catchment NS1.6 Review emergency response procedure MSA Staff time June 2017
5 Medium Catchment NS1.7 3 monthly evaluation of groundwater monitoring MSA Staff time On going
6 Low Abstraction wells
NS2.6 Develop a plan to isolate bores MSA Staff time June 2017
7 Medium Abstraction wells
NS2.8 Review of security of well heads and upgrade as necessary
MSA Staff time June 2017
8 Low Storage reservoirs
NTD1.1 Review and install membrane covers of reservoirs MSA $60,000 June 2017
9 Low Storage reservoirs
NTD3.4 Decommission Kamatea reservoir MSA $5,000 June 2017
10 Moderate Bores, and reticulation
network
NTD2.2 Develop network model MSA $100,000 December 2017
11 Low Catchment NS2.9 3 monthly meetings with Regional Council staff MSA Staff time On going
12 Moderate Booster pump station
NBP1.1 Improve security of booster pumps MSA $30,000 December 2017
13 Storage NTD1.7 Seismic assessment of reservoir structures MSA $80,000 December
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288.01 19
Action no.
Risk level following
improvements
Water Supply area
Reference to risk table
Proposed works Person responsible
Expected cost Intended completion
date
reservoirs 2017
14 Low Booster pumps
NBP1.1 Review of air valves MSA $5,000 December 2017
15 Moderate Other NTD2.3 Review and update the supply operations manuals DCS $20,000 December 2017
16 Low Reticulation Implement HPC sampling programme in conjunction with E. coli sampling
MEM Staff time
$1000
2016
17 Moderate Reticulation NDT2.2 Include projects in LTP to improve water network MSA Staff time June 2018
18 Medium Abstraction wells
NS2.4 Develop methodology for deploying generators MSA Staff time June 2017
19 Low Pumps, storage and reticulation
NS2.7 Refresher staff for training DCS $5,000 On going
20 Medium Pumps NBP1.3 Review pump maintenance programme DCS Staff time June 2017
21 Low Storage reservoirs
NTD1.2 Develop inspection check list for reservoirs DCS Staff time April 2017
22 Medium Storage reservoirs
NTD1.3 Undertake security review of all reservoirs and carry out works as required
DCS $7,000 June 2017
23 Medium Storage reservoirs
NTD1.6 Update water restriction plan and commission new reservoir at Taradale.
MSA Staff time June 2017
24 Medium Reticulation NTD2.8 and NTD3.10
Develop dedicated locations for taking water from hydrants
MSA $75,000 December 2017
25 Medium Reticulation NTD3.3 Carry out asset condition assessments MSA $10,000 On going
26 Medium Reticulation NTD3.6 Audit of backflow preventers MSA $5,000 On going
27 Low Reticulation NO1.5 Update operational processes and procedures DCS Staff time On going
28 Medium Reticulation NTD2.8 Develop a policy and process to take water from hydrants MSA Staff time June 2017
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288.01 20
10. Benefits of Proposed Improvements
The proposed improvements will provide public health benefits by reducing the risk of
adverse health outcomes associated with poor drinking water quality. Provision of more
storage will reduce the risk of supply interruption. Review of written procedures will reduce
contamination risks from operational activities. HPC monitoring will provide operational
information abut the microbiological activity within the reticulation system.
11. Methodology
This WSP has been prepared consistent with the approaches recommended by the Ministry
of Health. Supporting documents include the WSP Guides and A Framework on How to
Prepare and Develop Water Safety Plans for Drinking-water Supplies, Ministry of Health
(2005). A qualitative risk assessment approach has been taken following the guidance
notes in Appendix 2 of the “Framework” allowing the prioritisation of improvement needs and
development of the Improvement Schedule.
Risk tables have been prepared which identify the event, cause, risk without preventative
measures, indicators that the event may be occurring, preventative measures that are
currently in place to prevent the event, whether the risk is controlled, the residual risk,
additional measures that could be put in place and the person(s) who is primarily responsible
for managing that risk. The risk without preventative measures provides an indication of the
risk level of the event related to that cause if nothing was in place to prevent the event. The
residual risk is the remaining level of risk, taking account of the measures that are in place to
prevent the event related to that cause.
Indicative cost estimates and implementation timeframes have been prepared for the
required improvement measures and included in the improvement schedule where
necessary. These will be carried forward to the next Asset Management Plan (AMP) and
Council Long Term Plan for approval and inclusion in annual budgets following the statutory
public consultation process. Implementation of the Improvement Schedule is ultimately
subject to Council funding approval.
The Water Supply Asset Manager is responsible for implementation of the Improvement
Schedule within the timeframes indicated, subject to community and council approvals,
funding constraints and availability of resources. The Water Supply Asset Manager is
responsible for on-going review and updating of the WSP.
Contingency Plans have been prepared to provide guidance in the event that control
measures fail to prevent the occurrence of a risk event that may present an acute risk to
public health. The Water Supply Overseer is responsible for implementation of the
Contingency Plans when monitoring has identified the occurrence of a risk event.
Separate risk tables have been prepared for: recharge zone, bores, booster pumps, storage
reservoirs, reticulation, other.
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288.01 21
12. Risk Ranking Procedure
Potential public health risks have been evaluated using the Likelihood and Consequence
scales tabulated below to determine a risk level – low, medium, high, very high. The
assessed risk level allows prioritisation of the associated improvement measures.
Table 4. Likelihood Scale
Likelihood ranking Description
Almost Certain Is expected to occur in most circumstances
Likely Will probably occur (once in 1 or 2 years)
Possible Might occur at some time (once in say 5 years)
Unlikely Might occur once in 10 to 20 years
Rare Could occur (once in 50 to 100 years)
Table 5. Consequence Scale
Consequence Scale Description
Insignificant
- Insignificant impact
- Little disruption to normal operation
- Small increase in operation costs
Minor
- Short disruption of service ( < 1 hour) to part of a
zone (taken to be the 7 hydraulic zones in the Napier
system)
- Aesthetic water quality event for some consumers
- No reported illness
- Some manageable operation disruption
- Some increase in operating costs.
Moderate
- Disruption of service (<4 hours) to more than 1,000
properties
- Water quality event that requires flushing to clear
- Boil water notice for up to 3 days
- No reported illness
- Significant modification to normal operation but
manageable
- Operation costs increased
- Increased monitoring
Major
- Disruption of service (>4 hours) to two or more
zones (taken to be the 7 hydraulic zones in the Napier
system)
- Prolonged boil water notice
- Probable illnesses
- Adverse publicity and loss of trust of consumers
- Systems significantly compromised and abnormal
operation if at all
- High level of monitoring required
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288.01 22
Consequence Scale Description
Catastrophic
- Disruption of complete supply for one or more days
- Several instances of illness in the community or
instance of death
- Prolonged boil water notice
- Significant negative national press and long term
loss of trust of consumers
- Complete failure of systems
Table 6. Risk Level Allocation Table
Consequence
Likelihood Insignificant Minor Moderate Major Catastrophic
Almost certain Medium High Very high Very high Very high
Likely Medium High High Very high Very high
Possible Low Medium High Very high Very high
Unlikely Low Low Medium High Very high
Rare Low Low Medium Medium High
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288.01 23
13. Drinking Water Standards and Grading
The Napier City water supply fully complies with DWSNZ. Table 7. Below shows a summary
of compliance with the DWSNZ.
The treatment plant and distribution zone at Napier City are not currently graded.
Table 7. Summary of Compliance with DWSNZ
Compliance area Comments
Bacterial compliance criteria used
for water leaving the treatment
plant
Criterion 1
Protozoa log removal requirement
required for the supply
0-log. Secure bore water demonstrated
Protozoa treatment process None required. Secure bore water demonstrated
Compliance criteria 6A or 6B is
used for water in the distribution
zone.
Criterion 6A
Radiological compliance Monitoring every 10 years
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288.01 24
14. Consultation
On 14 December 2017, a workshop was held at the works depot of NCC at Austin Place to
prepare this updated WSP. Andrew Watson of BECA facilitated this workshop. The
attendees of the workshop were:
Director City Services (Lance Titter)
Manager Asset Strategy (Chris Dolley)
Jason Strong (Manager Environmental Solutions)
Fiona Bruins (Environmental Management Officer)
Team Leader 3 Waters (Santha Agas)
Team Leader Water (Dean Hammond)
Services Engineer (Graham Thorp)
Peter Martin (Pump Attendant)
Ricky Bales (Water Supply Operator)
Theo Fritz (Water Supply Operator)
An inspection of some of the bores, storage and other parts of the supply was undertaken on
the previous day by Andrew Watson, Santha Agas and Dean Hammond. Operation of the
supply and a draft risk table was discussed. Following the workshop a new risk table was
prepared with a different format.
The information provided during this consultation has been used to compile the risk tables.
The new risk table has been sent to all the workshop participants.
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288.01 25
15. Contingency Plan
Napier Water Supply Contingency Plan
Type of Event Contingency
Plan/Plans
Required Contingency Action Person
Respon
sible
Severe turbidity
of source water.
Indicators:
Highly turbid
water in
reticulation or
complaints from
consumers.
Bore isolation
plan (initial plan
will be prepared
by June 2017 and
subsequent
update following
modelling in June
2018)
Communication
plan (prepared by
March 2017)
Identify which bore(s) turbid water is
coming from and cease abstraction
from that bore(s). Refer to bore
isolation plan.
If a number of bores are implicated and
unable to abstract sufficient quantities
of water, supply from storage
reservoirs while problem is resolved
Pump any turbid bores to waste until
they run clear
Monitor storage level.
Monitor source water turbidity.
If storage is low and water with low
turbidity cannot be supplied, advise
DWA and issue Boil Water notice while
problem is resolved.
Issue water conservation notice
Keep customers informed and advise
once regular supply is restored (refer to
communication plan)
MAS
Severe
microbiological
contamination
of source water
Indicators: A
contamination
event near to
the boreheads
may be
observed by or
reported to
Napier City
Council staff.
May also be
indicated by
reported illness
among
consumers or
positive E. coli
monitoring
results.
Bore isolation
plan (initial plan
will be prepared
by June 2017 and
subsequent
update following
modelling in June
2018)
Temporary
chlorination plan
(prepared by June
2017).
Plan for provision
of alternative
water supply
including locations
for water tanks for
possible
contamination
scenarios
(prepared by June
Identify which bore(s) is contaminated
and cease abstraction from that
bore(s). Refer to bore isolation plan.
If a number of bores are affected and
unable to abstract sufficient quantities
of water, in addition to the
transgression response procedures in
the Drinking Water Standards, supply
from storage reservoirs until
contingency measures are in place as
described below.
Implement communication plan asap
Implement temporary chlorination plan
asap
Implement provision of alternative
water supply plan (tank water) asap
These contingency measures shall be
in place until the issue is resolved.
MAS
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288.01 26
Napier Water Supply Contingency Plan
Type of Event Contingency
Plan/Plans
Required Contingency Action Person
Respon
sible
2017)
Communication
plan (prepared by
March 2017)
E. coli
transgression in
water in
distribution
zone
Indicators: E.
coli
transgression
reported
following routine
monitoring.
Illness among
consumers
Temporary
chlorination plan
(prepared by June
2017)
Plan for provision
of alternative
water supply
including locations
for water tanks for
possible
contamination
scenarios
(prepared by June
2017)
Communication
plan (prepared by
June 2017)
Follow the transgression response
procedures in the Drinking Water
Standards. If E.coli transgression is
affected more than 500 properties, take
following actions immediately until the
issue is resolved.
Implement communication plan
Implement temporary chlorination plan
Implement provision of alternative
water supply plan (tank water)
These contingency measures shall be
in place until the issue is resolved.
MAS
Chemical
contamination
of source water
Indicators: A
contamination
event near to
the boreheads
may be
observed by or
reported to
Napier City
Council staff.
May also be
indicated by
reported water
quality concerns
from consumers
(taste, odour,
colour) or
illness among
consumers.
Plan for provision
of alternative
water supply
including locations
for water tanks for
possible
contamination
scenarios
(prepared by June
2017)
Communication
plan (prepared by
March 2017)
Advise Drinking Water Assessor (DWA)
Assess situation and take following
actions.
Implement communication plan
Implement provision of alternative
water supply plan (tank water)
These contingency measures shall be
in place until the issue is resolved.
MAS
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288.01 27
Napier Water Supply Contingency Plan
Type of Event Contingency
Plan/Plans
Required Contingency Action Person
Respon
sible
Insufficient
water available
for abstraction
or loss of ability
to take water
from the Napier
bores
Indicators:
Observed or
reported low
abstraction
levels, low
reservoir levels
Demand
management plan
Plan for provision
of alternative
water supply
including locations
for water tanks
(prepared by June
2017)
Communication
plan (prepared by
March 2017)
Implement demand management plan
Implement communication plan
Implement provision of alternative
water supply plan (tank water)
These contingency measures shall be
in place until the issue is resolved.
MAS
Earthquake,
flood or other
natural disaster
Emergency
response plan
Implement emergency response plan DS
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288.01 28
16. Risk Tables
Napier City Recharge Zone and Wells
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NS1 Groundwater Source
NS1.1 Microbiological contamination
Surface runoff from catchment.
Deep bores provide ‘secure” bore water. E. coli monitoring at bore heads and in reticulation. All bores are underground, secured and installed with sump pumps and alarms. Have 8 production wells and therefore have the ability to shut down wells drawing contaminated water (could buy some time to enable contingency measures to be put in place). Emergency chlorination.
Positive E. coli results at the bores. Turbidity in raw water (consumer complaint). Illness in community. Regional Council regulation of catchment.
Unlikely Catastrophic
Very high
Gain better understanding of risks by commissioning GNS to investigate zones of influence. 3 monthly meetings with relevant HBRC staff. Provide input into HBRC's consenting process for the activities which might lead into groundwater contamination. Meetings with HDC staff. Increase the water aging testing
Rare Major Medium
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288.01 29
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
frequency from 5 yearly to 3 yearly 5 yearly bore head assessment. Develop contingency plans as per section 14 of this document. (Action nos. 1,2, 3, and 11 of the improvement plan)
NS1.2 Microbiological contamination
Discharges from community wastewater systems, dairy effluent ponds, septic tank systems or urban stormwater.
As for NS1.1 Positive E. coli results at the bores. Turbidity in raw water (consumer complaint). Illness in community. Regional Council regulation of catchment
Rare Catastrophic
High As for NS1.1 Rare Major Medium
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288.01 30
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NS1.3 Chemical contamination
Surface runoff containing chemical contaminants from agricultural or industrial activities. (e.g. pesticides, fertilisers etc.).
No P2s registered against the supply. Chemical suite analysed from each bore and 12 sites across district every 2 years.
Taste and/or odour Complaints or information provided by public about activities in the catchment.
Rare Moderate Medium As for NS1.1 Rare Moderate
Medium
NS1.4 Microbiological or chemical contamination
Contaminants enter aquifer through abandonned/private/illegal wells.
Regional Council regulating wells (SOE monitoring bores spread across plains). Artesian pressure in lower part of plains, long travel time in aquifer from upper plains.
Positive E. coli results at the bores. Turbidity in raw water (consumer complaint). Illness in community. Regional Council regulation of catchment.
Unlikely Major High As for NS1.1 Unlikely
Moderate
Medium
NS1.5 Chemical contamination
Naturally occurring chemical contaminants that exceed MAV.
Chemical analysis indicates that the water does not contain contaminants which exceed 50% of the DWSNZ MAVs (i.e. no P2s).
Taste and/or odour. Results of raw water chemical testing. Results of MoH P2 chemical testing programme.
Rare Moderate Medium Develop contingency plans as per section 14 of this document. (Action no. 1 of the improvement plan)
Rare Moderate
Medium
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288.01 31
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NS1.6 Chemical contamination
Chemical spill contaminates ground water in catchment.
Transit time of groundwater to bores means considerable delay between water being contaminated by a spill and being abstracted at the bores. 8 production bores provide abstraction options.
Chemical spill is reported. Testing identifies unexpected contaminant. Complaints of taste or odour.
Unlikely Moderate Medium Confirm emergency spill procedures are in place, are responsive, and would work well. (Action no. 4 of the improvement plan)
Unlikely
Moderate
Medium
NS1.7 Leachate contamination
Leachate from Redcliffe Landfill contaminates aquifer.
Aquifer protected by confining layer.Groundwater monitoring wells located at landfill, and these show no evidence of leachate contamination.
Groundwater monitoring wells located at landfill.
Rare Catastrophic
High Evaluate groundwater monitoring results 3 monthly. (Action no. 5 of the improvement plan)
Rare Major Medium
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288.01 32
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NS1.8 Loss of supply Drought lowers water table reducing or preventing abstraction.
Water conservation measures (water restrictions) can be implemented during drought conditions. Aquifer is deep and has not been demonstrated to be affected by drought conditions. Emergency management plan can be activated.
Prolonged drought conditions. Reduced/no flow from bores.
Unlikely Minor Low None N/A N/A N/A
NS1.9 Saline contamination
Saline intrusion into ground water source.
Conductivity measured in 5 yearly chemical testing. Aquifer pressures are understood. Abstraction is managed to prevent excessive drawdown. Likely to have many years warning of intrusion, giving time to put response in place. Regional Council manages combined takes from aquifer.
Conductivity monitoring. Taste and/or odour complaints from consumers.
Rare Minor Low None N/A N/A N/A
NS2 Ground Water Abstraction Wells
NS2.1 Loss of supply Intentional vandalism to bore heads
Eight production bores provide abstraction options.
Obvious signs of damage to bore heads.
Unlikely Minor Low None N/A N/A N/A
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288.01 33
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
and/or bore electrical components.
Bores are installed below ground in difficult to access chambers. Bore electrical components are installed in locked steel cabinets. Between 6 and more than 24 hours treated water storage is available (in average summer demand period).
Reduced/no flow from bores. Alarms from bores indicate inadequate pump performance, pressure or flow.
NS2.2 Loss of supply Damage to boreheads or electrical components from flooding.
Eight production bores provide abstraction options. Bores are installed below ground in difficult to access chambers. Bore chambers include sump pumps and flooding alarms. Between 6 and more than 24 hours treated water storage is available (in average summer demand period). Electrical cabinets are installed in well drained areas.
Obvious signs of flooding, or heavy/prolonged rainfall.
Unlikely Minor Low None N/A N/A N/A
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288.01 34
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NS2.3 Loss of supply Bore pump failure
Eight production bores provide abstraction options. Between 6 and more than 24 hours treated water storage is available (in average summer demand period). Monthly motor electrical monitoring and maintenance of pumps undertaken. Bore pumps can be replaced in one to 2 days. Spare bore pumps held in store.
Reduced/no flow from bores. Alarms from bores indicate inadequate pump performance, pressure or flow.
Possible Insignificant
Low None N/A N/A N/A
NS2.4 Loss of supply Pump failure due to power outage >6hrs.
Reservoirs can provide between 6 and over 24 hours supply (in average summer demand period) Have 12 emergency generators (22 - 450kVA)
No pump activity alarm to operator. Reduction in storage reservoir water levels.
Possible Moderate High Document a methodology for deploying generators to bore pumps. (Action no. 18 of improvement plan)
Unlikely
Moderate
Medium
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288.01 35
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
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Proposed Corrective Action (s)
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NS2.5 Loss of supply Failure of bore structures.
Eight production bores provide abstraction options. Between 6 and more than 24 hours treated water storage is available (in average summer demand period).
Reduced/no flow from bores. High turbidity of water. Alarms from bores indicate inadequate pump performance, pressure or flow. Turbidity identified in source water.
Unlikely Moderate Medium Improve understanding of condition of wells (T1 to T4 now over 30 years old). Complete modelling exercise and add upgrade work or well replacement into LTP as required. Plan to isolate bore/bores and supply from the others. (Action nos. 6, 10, 17 and 25 of the improvement plan)
Rare Minor Low
NS2.6 Loss of supply Damage to bore from natural event like an earthquake.
Eight production bores provide abstraction options. Between 6 and more than 24 hours treated water storage is available (in average summer demand
Reduced/no flow from bores. High turbidity in water in reticulation network.
Unlikely Moderate Medium Plan to isolate bore/bores and supply from the others. (Action no.6 of the
Rare Minor Low
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288.01 36
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
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ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
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period). improvement plan).
NS2.7 Contamination of supply
Bore maintenance procedures result in contamination of supply.
Staff hold NZQA reticulation qualifications and understand need for good sanitation when working on supply that is not chlorinated. Water and wastewater maintenance and operations are separated within Council.
Positive E.coli results at bores or in network. Visual evidence of unsanitary maintenance practices.
Unlikely Moderate Medium Refresher training for staff. (Action no. 19 of the improvement plan).
Rare minor Low
NS2.8 Microbiological contamination
Contamination of bore or pipeline from SPS overflow (e.g Greenmedows SPS) - could happen in association with flooding.
Block bund around well pit. Artesian pressure. Secure wellheads. Alarm and pump in pit (would take half an hour to respond to SPS overflow).
Positive E.coli results at bore or in network. Illness in the community.
Unlikely Major High Review security of each wellhead near SPS and/or vulnerable to flooding. Review hydraulics/pressure transducers to check if negative pressures can occur.
Rare Major Medium
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288.01 37
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
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Proposed Corrective Action (s)
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Make necessary changes to wellhead and surrounds. (Action no. 7 of the improvement plan)
NS2.9 Loss of right to take water
Consent to take water is not renewed or is declined (one consent covers all bores).
Current consent expires in 2027.
Expiry date of existing resource consents.
Unlikely Catastrophic
Very high
3 monthly meetings with HBRC staff. Apply for the renewal of existing consent well in advance of expiry date. Investigate for alternative water sources if necessary. (Action nos. 2 and 11 of the improvement plan)
Rare Major Medium
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288.01 38
Risk Assessment of Existing Residual Risk* Assessment
Even
t
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Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to
check (and signs that action is needed)
Lik
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Proposed Corrective Action (s)
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NS2.10
Insufficient water for supply
Yield from current bores unable to meet demand.
Current consent conditions restrict quantity that can be extracted. Demand management plan can be implemented during times of high demand. Universal water metering could be considered, if necessary.
Low or reducing storage levels at times of high demand. Monitoring wells indicate excessive drawdown during time of high demand.
Rare Moderate Medium Review demand projections and confirm that demand can be met over the remaining life of the consent. Consider additional bores or bores at different locations. (Action no.2 of the improvement plan)
Rare Minor Low
*expected residual risk after
corrective actions are implemented
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288.01 39
Napier City Booster Pumps
Risk Assessment of Existing Residual Risk* Assessment
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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Proposed Corrective Action (s)
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NBP1 Booster Pumps
NBP1.1 Microbiological contamination
Contamination by sewage and/or floodwaters via air valves (located on suction side).
Church Rd and McLean Park BPSs have sump pumps. All others on hills except West Shore BPS which is unlikely to be flooded and therefore less vulnerable.
SPS overflow alarms. Positive E. coli result. Consumer complaints.
Unlikely Moderate Medium Removing of air valves, or piping air valve inlet/outlet above flood levels where necessary. (Action nos. 12 and 14 of the improvement plan).
Rare Minor Low
NBP1.2 Loss of supply Pump failure due to power outage >6hrs.
Reservoirs can provide between 6 and over 24 hours supply (in summer). Have 12 emergency generators (22 - 450kVA).
No pump activity. Alarm to operator. Reduction in storage reservoir water levels.
Possible Moderate High Document a methodology for deploying generators to BPSs. (Action no. 18 of the improvement plan).
Unlikely Moderate Medium
NBP1.3 Loss of supply to reticulation
Pump mechanical or motor failure.
Seven booster pumps and eight production bore pumps provide supply pressure ensuring minimal impact from one pump failure. All BPSs have standby pump. Reservoirs can provide between 6 and more than
No pump activity. Alarm to operator. Low reservoir levels or loss of pressure in reticulation.
Possible Minor Medium Review pump maintenance strategy and confirm if pro-active maintenance is warranted. (Action no.20 of the
Unlikely Minor Low
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288.01 40
Risk Assessment of Existing Residual Risk* Assessment
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Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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24 hours supply (in summer). Monthly electrical monitoring/maintenance of pump motors undertaken (but not pumps themselves). No spare pumps held in store, but can be ordered/delivered/replaced in 10 days.
Consumer complaints.
improvement plan).
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288.01 41
Napier City Transmission & Distribution
Risk Assessment of Existing
Residual Risk* Assessment
Even
t R
efe
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Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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NTD1 Storage Reservoirs
NTD1.1 Microbiological contamination
Leakage through reservoir roof or other parts of structure (need to consider retained soil at one end of Enfield Reservoir with houses above).
Reservoirs are covered and all entry hatches are sealed, but acknowledged that roofs (and buried wall at Enfield) could leak through cracks etc. Regular inspection of reservoirs is carried out.
Positive E. Coli in reservoir or reticulation sample.
Unlikely
Moderate Medium Inspection checklist to be developed. Assessed and install membrane cover for vulnerable reservoirs. (Action nos.8 and 21 of the improvement plans).
Rare Minor Low
NTD1.2 Microbiological contamination
Access by birds or vermin through vents/gaps in roof or other parts of structure.
Reservoirs are covered and all entry hatches are secure against ingress. Regular inspection of reservoirs is carried out
Positive E. Coli in reservoir or reticulation sample
Possible
Moderate High Inspection checklist to be developed. Review potential entry points and take action to mitigate the risk as necessary. (action no. 21 of the improvement plan).
Unlikely
Minor Low
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288.01 42
Risk Assessment of Existing
Residual Risk* Assessment Ev
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nce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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NTD1.3 Microbiological contamination
Vandalism to reservoir causes contamination either directly or indirectly (i.e. not graffiti).
Reservoirs are concrete structures that are very difficult to climb or damage. Roof of Enfield Reservoir is at ground level but is fenced. Ladder accesses have locked barriers. All access hatches are locked and secured (and some are alarmed). Acknowledged that Thompson site is fully accessible.
Positive E. Coli in reservoir or reticulation sample.
Unlikely
Major High Undertake security review of all reservoirs Prepare contingency plan for each reservoir. Fence the Thompson reservoir site. Add alarms to all reservoirs. (Action no.22 of the improvement plan).
Rare Moderate
Medium
NTD1.4 Microbiological contamination
Sediment accumulation within reservoir.
Use of bore water ensures water entering reservoir has very low sediment load, and secure source means no pathogens present. Reservoirs can be taken out of service and cleaned if required. Reservoirs cleaned out every 5 years (target).
Positive E. Coli in reservoir or reticulation sample.
Rare Moderate Medium None N/A N/A N/A
NTD1.5 Microbiological contamination
Contamination through insanitary maintenance or
Access to reservoirs is restricted to NZQA-qualified staff.
Positive E. Coli in reservoir or reticulation
Rare Moderate Medium None N/A N/A N/A
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288.01 43
Risk Assessment of Existing
Residual Risk* Assessment Ev
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Ref
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nce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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dip sampling procedure.
sample.
NTD1.6 Loss of supply
Insufficient storage to meet demand.
Increasing demand is understood. Demand management actions can be implemented. Some water conservation communications - eg Leaky Tap initiative.
Loss of water or pressure in reticulation. Frequent low reservoir levels
Possible
Moderate High Strengthen promotion of sensible use of water by community. Monitor reservoir levels through SCADA. Prepare water restriction plan. Commission Taradale new reservoir. (Action no. 23 of the improvement plan).
Unlikely
Moderate
Medium
NTD1.7 Loss of supply
Failure of reservoir
Water (on restricted demand basis) could be supplied directly to most of reticulation system. Condition assessments are undertaken at a regular frequency.
Complaints from consumers about loss of supply or pressure. Obvious signs of leakage or
Rare Catastrophic
High Review of asset condition and undertake seismic assessment - carry out seismic strengthening
Rare Major Medium
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288.01 44
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failure at reservoir site.
if necessary. Develop inspection programme. (Action nos. 22 and 24 of the improvement plan)
NTD1.8 Loss of supply
Overflows can cause undermining of tank foundation and/or damage to downstream properties/assets.
Minor overflows can be safely disposed of, but no facility for large overflows - eg Enfield.
Complaints from public about overflows. Obvious signs of leakage or failure at reservoir site.
Possible
Major Very high
Review maximum possible inflows to each reservoir and consequences of overflows that exceed hydraulic capacity of existing overflow system. Upgrade overflows as necessary. Install alarm system. (Action no.22 of the improvement plan).
Rare Major Medium
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288.01 45
Risk Assessment of Existing
Residual Risk* Assessment Ev
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Ref
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nce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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NTD2 Treated Water Transmission – Napier City
NTD2.1 Loss of supply
Pipe failure Pipe failures are repaired as a priority. Good asset knowledge is held on pipe ages, material and condition. At risk pipe types have been replace as part of the on-going renewals programme
Complaints from consumers about loss of supply. Change in flow or pressure in reticulation.
Possible
Insignificant
Low None N/A N/A N/A
NTD2.2 Loss of supply
Excessive demand in network or inadequate system capacity.
Basic network model is being used and network demand is known. Network capacity and pressures have been demonstrated to be adequate
Complaints from consumers about low pressure or loss of supply. Change in flow or pressure in reticulation
Unlikely
Minor Low Build a new network model to analyse and identify upgrade requirements and include in the LTP. (Action nos. 10 and 17 of the improvement plan).
Rare Minor Low
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288.01 46
Risk Assessment of Existing
Residual Risk* Assessment Ev
ent
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nce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
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NTD2.3 Microbiological contamination
Inadequate controls on maintenance and construction work.
Written procedures have been prepared for disinfection and testing on pipe installations or repairs. Work is undertaken by NZQA water reticulation trained and experienced staff
Complaints from consumers about taste or odour. E. coli identified in reticulation system.
Unlikely
Major High Review ongoing staff training as necessary. Action no. 19 of the improvement plan).
Rare Major Medium
NTD2.4 Chemical or microbiological contamination
Backflow from consumer connections
Premises on industrial zoned land are required to have a RPZ or testable double check valve based on hazard. BFPs installed on SPSs. Land-use or building use change initiates backflow assessment. Check valve manifolds being progressively installed at residential premises. Backflow devices are tested annually by Council.
Contaminants identified in the reticulation system. Taste or odour complaints from consumers.
Unlikely
Catastrophic
Very high
Audit of all commercial/industrial premises, with appropriate follow up actions. Use of trade waste database to identify high risk premises. Check hydraulic model (and data from any transducers) for negative pressure surges in network, and action any
Rare Major Medium
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288.01 47
Risk Assessment of Existing
Residual Risk* Assessment Ev
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nce
Event Cause Existing Preventive Measures / Monitoring
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necessary follow up measures. (Action nos. 10 and 26 of the improvement plan).
NTD2.5 Loss of water
Unidentified leakage, illegal connections or unaccounted for water.
Known breaks and leaks repaired as a priority. Network demand is known and loss monitored. Eight production bores provide abstraction options.
Results of leak detection surveys. Per head consumption exceeds expectations.
Unlikely
Minor Low None N/A N/A N/A
NTD2.6 Supply of turbid water
Silt or biofilm build up within reticulation pipes.
Groundwater has low sediment concentration. Flushing undertaken as required. Programme of cleaning (pigging) target of 20% of mains annually.
Reduced flows in reticulation. Complaints from consumer about quality of water.
Unlikely
Minor Low None N/A N/A N/A
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288.01 48
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NTD2.7 Inadequate supply of water
Poor quality workmanship or inappropriate materials used for reticulation pipes and fittings, or contractor damage to pipes.
All work and materials used in reticulation to meet standard NCC specifications. Best practice approach taken to reticulation work. Work is undertaken by NZQA-qualified and experienced staff.
Contaminants identified in the reticulation system. Taste and odour complaints from consumers.
Rare Moderate Medium None N/A N/A N/A
NTD2.8 Microbiological or chemical contamination
Water takes from fire hydrants and water tanker carriers.
Permission is required from the Council to take water from hydrants, but there is no formal process for this.
Contaminants identified in the reticulation system. Taste and odour complaints from consumers.
Likely Major Very high
Prepare a policy for taking water from hydrants. Formalise the process for taking water from hydrants. Develop dedicated locations for water takes by contractors. (action nos. 24 and 28 of the improvement plan)
Rare Moderate
Medium
NTD3 Treated Water Transmission – Bay View
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288.01 49
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NTD3.1 Loss of supply
Pipe failure Pipe failures are repaired as a priority. Good asset knowledge is held on pipe ages, material and condition. At risk pipe types have been replace as part of the on-going renewals programme
Complaints from consumers about loss of supply. Change in flow or pressure in reticulation.
Possible
Insignificant
Low None N/A N/A N/A
NTD3.2 Loss of supply
Excessive demand in network or inadequate system capacity.
Basic network model is being used and network demand is known. Network capacity and pressures have been demonstrated to be adequate
Complaints from consumers about low pressure or loss of supply. Change in flow or pressure in reticulation
Unlikely
Minor Low Build a new network model to analyse and identify upgrade requirements and include in the LTP. (Action nos. 10 and 17of the improvement plan).
Rare Minor Low
NTD3.3 Loss of supply
Supply main failure
There are 2 pumping mains. One from Tannery pump station and one from Westshore booster pump station.
Complaints from consumers about low pressure or loss of supply. Change in flow or
Unlikely
Major High Asset condition assessment, pressure control and monitoring. Alternative water supply (tank water)
Rare Moderate
Medium
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288.01 50
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pressure in reticulation
((Action nos. 1and 25 of the improvement plan).
NTD3.4 Microbiological contamination
Contamination at the Kamatea reservoir
Water is chlorinated Positive E.coli results
Possible
Moderate High Decommission Kamatea reservoir. This reservoir is not essential for the system. (Action no. 9 of the improvement plan).
Rare Insignificant
Low
NTD3.5 Microbiological contamination
Inadequate controls on maintenance and construction work.
Written procedures have been prepared for disinfection and testing on pipe installations or repairs. Work is undertaken by NZQA water reticulation trained and experienced staff
Complaints from consumers about taste or odour. E. coli identified in reticulation system.
Unlikely
Major High Review ongoing staff training as necessary. (Action no. 19 of thje improvement plan).
Rare Major Medium
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288.01 51
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NTD3.6 Chemical or microbiological contamination
Backflow from consumer connections
Premises on industrial zoned land are required to have a RPZ or testable double check valve based on hazard. BFPs installed on SPSs. Land-use or building use change initiates backflow assessment. Check valve manifolds being progressively installed at residential premises. Backflow devices are tested annually by Council.
Contaminants identified in the reticulation system. Taste or odour complaints from consumers.
Unlikely
Catastrophic
Very high
Audit of all commercial/industrial premises, with appropriate follow up actions. Use of trade waste database to identify high risk premises. Check hydraulic model (and data from any transducers) for negative pressure surges in network, and action any necessary follow up measures. (Action nos. 10 and 26 of the improvement plan).
Rare Major Medium
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288.01 52
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al R
isk Proposed
Corrective Action (s)
Like
liho
od
Co
nse
qu
ence
Res
idu
al R
isk
NTD3.7 Loss of water
Unidentified leakage, illegal connections or unaccounted for water.
Known breaks and leaks repaired as a priority. Network demand is known and loss monitored. Eight production bores provide abstraction options.
Results of leak detection surveys. Per head consumption exceeds expectations.
Unlikely
Minor Low None N/A N/A
NTD3.8 Supply of turbid water
Silt or biofilm build up within reticulation pipes.
Groundwater has low sediment concentration. Flushing undertaken as required. Programme of cleaning (pigging) target of 20% of mains annually.
Reduced flows in reticulation. Complaints from consumer about quality of water.
Unlikely
Minor Low None N/A #N/A
NTD3.9 Inadequate supply of water
Poor quality workmanship or inappropriate materials used for reticulation pipes and fittings, or contractor damage to pipes.
All work and materials used in reticulation to meet standard NCC specifications. Best practice approach taken to reticulation work. Work is undertaken by NZQA-qualified and experienced staff.
Contaminants identified in the reticulation system. Taste and odour complaints from consumers.
Rare Moderate Medium None N/A N/A
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288.01 53
Risk Assessment of Existing
Residual Risk* Assessment Ev
ent
Ref
ere
nce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
Like
liho
od
Co
nse
qu
ence
Res
idu
al R
isk Proposed
Corrective Action (s)
Like
liho
od
Co
nse
qu
ence
Res
idu
al R
isk
NTD3.10 Microbiolog
ical or
chemical
contaminati
on
Water takes
from fire
hydrants and
water tanker
carriers.
Permission is required
from the Council to take
water from hydrants, but
there is no formal
process for this.
Contamina
nts
identified in
the
reticulation
system.
Likely Major Very
high
Prepare a
policy for
taking water
from
hydrants.
Formalise
the process
for taking
water from
hydrants.
Develop
dedicated
locations for
water takes
by
contractors.
(action nos.
24 and 28 of
the
improvemen
t plan)
Rare Moderat
e
Medium
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288.01 54
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
NO1 Other
NO1.1 Sampling failure
Inadequate sampling programme or sample collection error
Sampling programme prepared and checked against standards. More than the required number of samples is collected.
DWSNZ compliance failure due to days of weeks, days between samples, insufficient samples, information gaps etc.
Rare Major Medium None N/A N/A N/A
NO1.2 Failure of equipment due to inadequate maintenance
Supply equipment fails due to inadequate asset information or inadequate maintenance planning
Accella software is used as asset management system.
Unexpected equipment or plant failures.
Unlikely Moderate Medium Refresher training for staff. (Action no. 19 of the improvement plan).
Rare Minor Low
NO1.3 Failure due to inadequate procedures
Inadequate, out of date or incorrect operational procedures.
Operational procedures are updated as necessary.
Operational manuals are not used.
Rare Moderate Medium None N/A N/A N/A
NO1.4 Operator error or management
Poor operational practices, plant failures and supply are affected.
Water supply staff are suitably qualified to operate the system.
Operational failures.
Rare Moderate
Medium None N/A N/A N/A
NO1.5 Failure to meet DWSNZ
Poor processes and procedures.
Processes and procedures are updated as necessary.
System failures.
Rare Moderate Medium Processes and procedures
Rare Minor Low
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288.01 55
Even
t
Refe
ren
ce
Event Cause Existing Preventive Measures / Monitoring
Monitoring - What to check (and signs that action is needed)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
Proposed Corrective Action (s)
Lik
elih
oo
d
Co
nseq
uen
ce
Resid
ual
Ris
k
are updated 3 yearly and on as necessary basis. (Action no.27 of the improvement plan)