Session Title:
NPWTP Temporary Fluoride dosing
Session Date:
25/10/2022
Session Location:
Mishima Room
ATTENDANCE RECORD
Name
Position
Company
Signature
Graeme Pool
Principal Operations Engineer
NPDC
Paula Wright
Project Manager Lead
NPDC
James Mitchell
Infrastructure Project Manager
NPDC
Safety in Design for NPWTP Fluoridation Project
Inherent risk assessment
Residual risk assessment
Risk
HAZARD
Description of Consequence
Risk Owner
Current treatment
Future or additional treatments
ACTION On
Risk last updated
Next Review
Close Out Comments
ID
Consequence
Likelihood
Rating
Consequence
Likelihood
Rating
Uncertain Negative HSE Risk is due to Event Y leading to
consequence Z.
Monitoring of source water is a stndard requirements.
Natural Events/
volcanic eruption increases the level of naturally occuring
Supernatenat recyle will also be sampled to ensure fluoride in
D1
Environmental
fluoride leading to overdosing of the water supply adversley
NPDC
Catastrophic
Unlikely
High
filterbackwash is accounted for. Online fluoride anlayser will shut
Catastrophic
Unlikely
High
Amend IRP to shut down fluoride dosing in event of an eruption
Conditions
impacting health
down dosing id treated fluoride concentration becomes high
(<1.1ppm).
Transfer pump is intended to run only until HFA day tank is full, or
Environmental
Transfer pump continue to run leading to overfow from HFA day
Consider hard piping the dosing skid drain back to the IBC bund as IBC bund will contain
D2
NPDC
Moderate
Possible
Medium
for a maximum time. Dosing skid bund includes a level switch
Moderate
Unlikely
Low
Damage
tank and over filling dosing skid bund
the full contents of an IBC
which will generate an alarm.
Vents are fixed to top of tanks. Not normally submerged so are not
vents extended and vented
Operations and
uncontrolled / unexpected discharge through vent due to
Consider extending vents to low level in bund so discharge is at low level in the bund. Air
D3
NPDC
Moderate
Possible
Medium
foreseen to contain liquid. Day tank in bund will contain liquid
Low
Possible
Insignificant
outside of covers to prevent
Maintenance
bubbles resulting in splashing / contamination of personnel
break required to prevent siphoning
when IBC is full but then should not contain any air bubbles
build up of fumes
Dosing skid day tank required to contain sufficient chemical to
Reliance on visual observance of IBC contents results in
Operations and
allow at least 24 hours dosing within refilling. Therefore there
Consider PT on bund day tank to provide level information to SCADA screen and to allow
PT installed on bund day tank
D4
chemical being depleted without operator knowledge and
NPDC
Minor
Moderate
Medium
Minor
Possible
Low
Maintenance
should be a 24 hour period during which operators can identify
trending / alarming at low level.
(Transfer Tank)
dosing is interupted.
that the IBC is empty and arrange an exchange
Dosing flow meter provides check on dose flow rate and is
programmed to alarm at high flow or on deviation from
Operations and
Dosing system malfunctions resulting in overdosing of fluoride
programmed dose rate. Online fluoride analyser will shut down
D5
NPDC
Catastrophic
Unlikely
High
Catastrophic
Unlikely
High
Maintenance
to the drinking water making drinking water unsafe
dosing if treated fluoride concentration becomes high (<1.1ppm).
Neither instrument provide control feedback as per WaterNZ CoP
and only provide alarms and inhibits
Reverse flow through duty / standby arrangement of dosing
Operations and
dosing pumps are positive displacement pumps which prevent
Discuss pump types with supplier and confirm reverse flow can not occur. Consider
D6
pumps resulting in lower than expected dose rate and or recyle
NPDC
Minor
Moderate
Medium
Minor
Unlikely
Insignificant
non return valves installed
Maintenance
reverse flow by design
installation of non-return valves on each pump discharge
of HFA to the Day tank through the standby dosing pump
Schedule 80 pVC pipework specified. Actual pressure is low.
Majority of pipework on the dosing skid in enclosed within the
Material defects - exposure to sunlight results in premature
D7
Material Defects
NPDC
Moderate
Moderate
Medium
dosing skid. Dosing line from the skid is dual enclosed and below
Moderate
Possible
Medium
Consider painting the exposed pipework to provide additonal protection from sunlight
Pipework dual contained
ageing of plastic pipes and fittings
ground. Some piping between the IBC and dosing skid may be
exposed to sunlight. Operating pressure of this pipework is <20kPa
D8
D9
D10
2 of 4
SID NPWTP Fluoridation reviewd 27-6-23.xlsm
14/08/2023
CH2M Beca
Safety in Design for NPDC LTP Reservoirs
Construction Considerations for Henwood Road
Risk ID
Hazard
Description
Risk Owner
Inherent risk assessment
Current treatment
Residual risk assessment
Future or additional treatments
ACTION On
Risk last updated
Next Review
Close Out Comments
Consequence
Likelihood
Rating
Consequence
Likelihood
Rating
Uncertain Negative HSE Risk is due to Event Y
leading to consequence Z.
Forklift operations in confined area during
work plan and segregation of
construction presents hazard to site staff.
Location of work clearly defined. Establish
C1
Construction
NPDC
Major
Moderate
High
Minor
Possible
Low
construction activity and
Uncontrolled access may result in hospitalisation or
work area isolation during construction
operations/maintenance
fataliity
Forklift operations in confined area during
IBC bund and dosing skid designed to be
construction results in damage to equipment during
handled by forklift. Proposed location has
C2
Construction
NPDC
Minor
Possible
Low
Minor
Possible
Low
installation delaying the commencement of
previously been used for temporary storage of
fluoridation
larger equipment handled by forklift
Pre commissioing inspections. Commissioing
Material defects result in failure of dosing to operate
undertake commissioing process using
plan. Pump performancec checked during
C3
Construction
as intended / failing prematurely or during
NPDC
Moderate
Moderate
Medium
Minor
Unlikely
Insignificant
Potable water instead of HFA until
commissioing. Functional description provides
commissioning
operation fully checked and verified.
protection against over or under dosing.
Pre commissioing inspections. Commissioing
Construction defect leads to unexpected behaviour
undertake commissioing process using
plan. Pump performancec checked during
C4
Construction
during commissoning resulting in overdosing of
NPDC
Moderate
Possible
Medium
Minor
Unlikely
Insignificant
Potable water instead of HFA until
commissioing. Functional description provides
chemical or loss of containment
operation fully checked and verified.
protection against over or under dosing.
C5
C6
C7
C8
C9
C10
C11
3 of 4
SID NPWTP Fluoridation reviewd 27-6-23.xlsm
14/08/2023
CH2M Beca
Safety in Design for NPDC LTP Reservoirs
Operations and Maintenance Considerations for Henwood Road
Risk
Hazard
Description
Risk Owner
Inherent risk assessment
Current treatment
Residual risk assessment
Future or additional treatments
ACTION On
Risk last updated
Next Review
Close Out Comments
ID
Consequence
Likelihood
Rating
Consequence
Likelihood
Rating
Forklift operations in confined area during
construction presents hazard to site staff.
trained forklift operators. Procedures in place
O1 Operations and Maintenance
NPDC
Major
Moderate
High
Minor
Possible
Low
Uncontrolled access may result in hospitalisation or
for forklift operations
fataliity
Existing site lighting. Dosing is not critical to
Inadequate lighting resulting in poor working
provision of safe water. If Operators are unable
O2
Egress / Access
NPDC
Moderate
Likely
High
Minor
Possible
Low
conditions for operator especially out of hours
to address due to poor light it is acceptable to
wait until next working period
Dosing flow meter provides check on dose flow
rate and is programmed to alarm at high flow
or on deviation from programmed dose rate.
Operation fatigue leads to inappropriate operation of
Online fluoride analyser will shut down dosing
O3 Operations and Maintenance
NPDC
Catastrophic
Possible
High
Catastrophic
Unlikely
High
dosing system reusling in incorrect dose of HFA
if treated fluoride concentration becomes high
(<1.1ppm). Neither instrument provide control
feedback as per WaterNZ CoP and only provide
alarms and inhibits
4 of 4
SID NPWTP Fluoridation reviewd 27-6-23.xlsm
14/08/2023
CH2M Beca
