water safety plan (wsp)€¦ · team leader 3 waters santha agas team leader water supply dean...

Water Safety

Plan (WSP)

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

288.01 4

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.

288.01 5

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)

288.01 6

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


Type of Source Bore


Plant Name Bledisloe Park


Location (T2) Bledisloe Park



Source Name Burness Road Bore


Type of Source Bore


Plant Name Burness Road


Location (T1) Road reserve Burness Road



Source Name Cloverdale Bore


Type of Source Bore


Plant Name Cloverdale Pump Station


Location (C1) Cloverdale St



Source Name Guppy Road Bore


Type of Source Bore


Plant Name Guppy Road


Location (T5) Road reserve Guppy Road


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Source Name Riverside Park Bore


Type of Source Bore

Grid Reference of Source (NZTM) Easting : 2840344 Northing : 6177098

Plant Name Riverside Park


Location (T3) Riverside Park



Source Name T4 Bore Napier


Type of Source Bore


Plant Name T4 Pump Station


Location (T4) Gloucester Street



Source Name T6 Bore


Type of Source Bore


Plant Name T6 Pump Station


Location (T6) Road reserve Guppy Road



Source Name T7 Bore, King Street


Type of Source Bore


Plant Name T7 Pump Station, King Street


Location (T7) King Street


Distribution Zone (Napier community)

Distribution Zone Name Napier City

288.01 9

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)

288.01 10

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

288.01 11

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

288.01 12

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.

288.01 13

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

288.01 14

288.01 15

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

288.01 16

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

288.01 17

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

288.01 18

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


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

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


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

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.

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

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

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

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.

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

288.01 26



Plan/Plans


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


water supply plan (tank water)



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.






MAS

288.01 27



Plan/Plans


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






MAS

Earthquake,

flood or other

natural disaster

Emergency

response plan

Implement emergency response plan DS

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

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Resid

ual

Ris

k

Proposed Corrective Action (s)

Lik

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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

288.01 29


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ual

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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)


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

288.01 30


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Resid

ual

Ris

k


Lik

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d

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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


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

288.01 31


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Resid

ual

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Lik

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Resid

ual

Ris

k


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

288.01 32


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Resid

ual

Ris

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Lik

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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.


288.01 33


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ual

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ual

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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.


288.01 34


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Resid

ual

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Resid

ual

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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

288.01 35


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Resid

ual

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k

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

288.01 36


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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


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

288.01 37


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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

288.01 38


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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

288.01 39

Napier City Booster Pumps


Even

t

Refe

ren

ce


Monitoring - What to check (and signs that action is needed)

Lik

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oo

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uen

ce

Resid

ual

Ris

k


Lik

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Resid

ual

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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

288.01 40


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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).

288.01 41

Napier City Transmission & Distribution

Risk Assessment of Existing

Residual Risk* Assessment

Even

t R

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Like

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Corrective Action (s)

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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


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

288.01 42


Residual Risk* Assessment Ev

ent

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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.


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


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).


Rare Moderate Medium None N/A N/A N/A


Contamination through insanitary maintenance or

Access to reservoirs is restricted to NZQA-qualified staff.

Positive E. Coli in reservoir or reticulation


288.01 43



ent

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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


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

288.01 44



ent

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failure at reservoir site.

if necessary. Develop inspection programme. (Action nos. 22 and 24 of the improvement plan)


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

288.01 45



ent

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NTD2 Treated Water Transmission – Napier City


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



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

288.01 46



ent

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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

288.01 47



ent

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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

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.


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.


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

288.01 49



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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



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


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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pressure in reticulation

((Action nos. 1and 25 of the improvement plan).


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


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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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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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.


Rare Moderate Medium None N/A N/A

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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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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.


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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are updated 3 yearly and on as necessary basis. (Action no.27 of the improvement plan)

water safety plan (wsp)€¦ · team leader 3 waters santha agas team leader water supply dean...

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