Gore Drinking-water Supply

Transcription

1 Public Health Management Plan Gore Drinking-water Supply Prepared By Jim Graham Principal Environmental Scientist Wellington Environmental Office L5, Majestic Centre, 100 Willis St PO Box , Thorndon, Wellington 6144 New Zealand Reviewed By Telephone: Facsimile: Christopher Bergin Projects Work Group Manager Date: 18 June 2013 Reference: Status: Final 2013

2 Gore Public Health Management Plan Contents 1 Revision Details Introduction Supply Details Description of the Drinking Water Supply Photographs of the Gore Water Supply System Flow Chart Schematic of Supply Critical Points and Barriers to Contamination Barriers to Contamination Improvement Schedule Benefits of Proposed Improvements Methodology Ranking Procedure Drinking Water Standards, and Grading Consultation Contingency Plan Tables

3 Gore Public Health Management Plan Figures Figure 1 Map of Gore Water Supply Key Infrastructure...8 Figure 2 Map of Gore Water Supply Reticulation... 9 Figure 3 Jacobstown well Figure 4 Jacobstown bore Figure 5 New Coopers well Figure 6 Older Coopers well Figure 7 Hilbre Ave sand filters Figure 8 Hilbre Ave aeration tower Figure 9 Hilbre Ave caustic soda storage Figure 10 Hilbre Ave on-line monitoring Figure 11 Hilbre Ave chlorine storage Figure 12 Pressure pumps for higher levels of North Gore Figure 13 Wentworth St treatment plant Figure 14 Wentworth St backup generator Figure 15 Wentworth St on-line monitoring Figure 16 Wentworth St reservoir Figure 17 Critical Point Schematic of Gore Water Supply Tables Table 1 Summary of Gore Drinking Water Supply Details... 5 Table 2 Critical Points Table 3 Capital and Significant Projects Table 4 Operational Improvements and Minor Projects Table 5 Likelihood Scale Table 6 Consequence Scale Table 7 Level Allocation Table Table 8 Summary of Compliance with DWSNZ Table 9 Contingency Plan for Gore Water Supply

4 1 Revision Details Gore Public Health Management Plan Version No Description Approved Revision Date V1 For assessment by DWA 2017 Following approval of this plan it will be revised and submitted for re-approval following any major system reconfigurations or, alternatively, before 1 January Review of the performance of the plan Review of the performance of the plan and adjustments to the plan will be undertaken annually. The review will include an assessment of events such as non-compliances, near misses and unexpected situations that have occurred, progress made against the improvement schedule and changes to any of the supply elements. Adjustments will be made to the plan as a result of information provided by this assessment. Reporting of the plan A brief report on the performance of the plan, including information on the review will be provided by the 3 Waters Asset Manager to the General Manager District Assets annually on the anniversary of the plan being finalised. Links to other quality systems This Public Health Management Plan (PHRMP) will be linked to the Activity Management Plan and the Council Long Term Plan

5 2 Introduction Gore Public Health Management Plan This Public Health Management Plan (PHRMP) has been prepared for the Gore water supply to identify potential events that present public health risks to the consumers of the drinking water supply. Gore District Council is committed to this PHRMP and to the future improvements to the supply that have been identified in this PHRMP. The Gore drinking water supply is an urban supply providing water to a population of approximately 7480 people in the town of Gore. The water for the supply is sourced from two bore fields, one located on the north bank of the Mataura River between Whiterig and Knapdale called Coopers Wells and the second located at the northwest of the town called Jacobstown Wells. A third source at Oldham Street in Gore has in the past provided an emergency supply during dry summer months but this source has now been abandoned. Water from the Jacobstown wells is supplied to the Hilbre Ave water treatment plant. Some of the treated water is pumped to service the high areas of the reticulation in West Gore. The rest of the water is fed by gravity into the low level reticulation for Gore on the west side of the Mataura River. The high and low level reticulation networks are normally isolated from one another. Water from the Coopers wells is supplied to the Wentworth Street water treatment plant. Some treated water is pumped up to the tanks on Talbot Street to supply water to the high areas of the reticulation in East Gore. The rest of the water is fed by gravity into the low level reticulation for Gore on both sides of the Mataura River. The scheme is administered at the main council offices in Civic Avenue, Gore and is managed by Council s Utility Assets team. The maintenance and operation of the Gore Water Supply are the responsibility of Gore District Council s water and wastewater field staff

6 Gore Public Health Management Plan 3 Supply Details Table 1 Summary of Gore Drinking Water Supply Details Supply Details Supply Name Gore WINZ Community Code GOR001 Supply Owner Gore District Council General Manager District Assets Paul Withers 3 Waters Asset Manager Sarah Dowling Essential Services Supervisor Ian Lowe Water TP Operators Corey Reed, Daniel Wright, Michael Lee Population Served by Supply 7480 (WINZ register 2013) Source 1 Details Source Name Jacobstown Wells Source WINZ Code G00051 Type of Source Shallow groundwater Depth of Bores Well - 7m. Bore - 24m Consent Expires March 2025 Maximum Consented Water 3,000 m 3 /day Grid Reference of Source Easting : Northing : Treatment 1 Details Location Hilbre Avenue WTP Treatment Plant WINZ Code TP00084 Treatment Processes Pressure sand filtration, chlorine dosing, caustic soda dosing, aeration Average Daily Volume 1,150 m 3 /day Source 2 Details Source Name Coopers Wells Source WINZ Code G00052 Type of Source Shallow groundwater Depth of Bores Up to 8 metres depth Consent Expires August 2033 Maximum Consented water take: 5,000 m 3 /day Grid Reference of Source Easting : Northing : Treatment 2 Details Location Wentworth Street WTP Treatment Plant WINZ Code TP00085 Treatment Processes Chlorine dosing, caustic soda dosing, aeration Average Daily Volume 2,850 m 3 /day Distribution Zone Distribution Zone Name Gore Distribution Zone WINZ Code GOR001GO Distribution Zone Population 7480 (WINZ 2013)

7 Gore Public Health Management Plan 4 Description of the Drinking Water Supply 3.1 Water Sources The Jacobstown wells are located within a gravel stockpile area adjacent to SH94, approximately 200 m from the Mataura River. There are five wells at the site but only two are used, a shallow well of 7 metres depth and a bore of 24 metres depth. The abstraction rate from the Jacobstown well and bore is approximately 1,240 m 3 /day with a normal rate of 23 L/s. The water sourced from Jacobstown well is slightly acidic, containing relatively low concentrations of dissolved ions and slightly elevated nutrient concentrations. The water from the bore has elevated levels of manganese. Generally the turbidity from the well is low. Water can be pumped from the Mataura River into one of the abandoned wells to artificially recharge ground water levels in dry periods. The Jacobstown well and bore supply water to the Hilbre Avenue water treatment plant. The Coopers wells are located on the floodplain of the Mataura River approximately 5km north of Gore just off the Knapdale Highway. The area surrounding the Coopers wells site is relatively flat and has been used for dairy farming over the past 10 years. There are four wells at the Coopers site. Two of the wells are operational and two have been abandoned. The operational wells have depths of up to 8 7 metres with continuous slots from 3 m to 6 m. During dry periods water can be pumped from the Mataura River into one of the abandoned wells to artificially recharge groundwater levels. The wells have a relatively constant rate of abstraction with an average rate of 2850 m 3 /day though a peak extraction of 5167 m 3 /day has been recorded. The Coopers wells supply water to the Wentworth Street water treatment plant. 3.2 Treatment Plant Facilities and Processes The treatment processes at Hilbre Ave water treatment plant include pressure sand filtration, aeration, ph correction and gas chlorine disinfection. Water is then stored in a treated water reservoir before being distributed to the reticulation system. Flow rate through the plant is generally about 26 L/s however a maximum flow of 40 L/s has been recorded. There are a number of issues with the Hilbre Ave plant. The pressure sand filters date from the 1940 s and their performance cannot be assured. The quantity and condition of the sand in the filters is not known. Gas chlorine dosing is provided from a 920kg chlorine tank. The tank is on scales and the operators check the weight to determine when the tank is near empty and a new tank is ordered. A standby tank is not kept on site. The chlorine is manually adjusted to a set point to maintain a chlorine level of.6ppm in water leaving the plant. Because the source water has low turbidity and remains relatively constant, there is little need to adjust the chlorine level. FAC, ph and turbidity are continuously monitored at the plant. The average raw water turbidity is 1.1 NTU and the treated water turbidity is 0.3 NTU, though the turbidity metres have not been regularly calibrated. E. coli samples are taken weekly

8 Gore Public Health Management Plan The Hilbre Ave Reservoir has a capacity of 1000 m 3 which provides less than 24 hours supply for this part of the system. The Jacobstown well pumps are controlled by the reservoir level, turning off at 85% full and on when the level drops below 77%. There is a high level alarm activated at 97% and a low level alarm at 60%. The treatment processes at the Wentworth Street water treatment plant includes aeration, ph correction and gas chlorine disinfection. Gas chlorine dosing is provided from a 920kg chlorine tank. A 70kg standby tank is kept on site and an auto changeover system is in place. The chlorine is manually adjusted to a set point to maintain a chlorine level of 0.6ppm in water leaving the plant. Because the source water is has low turbidity and remains relatively constant, there is little need to adjust the chlorine level. FAC, ph and turbidity are continuously monitored at the plant. The average raw water turbidity is 0.2 NTU and the treated water turbidity is 0.1 NTU, though the turbidity meters have not been calibrated. A backup generator at the Wentworth Street plant provides electricity in the event of a mains power supply failure. Water is then stored in a treated water reservoir which feeds Gore s low level reticulation by gravity. A small proportion is pumped to the Talbot Street Reservoir, two 22 m 3 tanks, which supply the East Gore high level reticulation system. The Wentworth Street Reservoir has a capacity of 4000 m 3, less than 24 hours storage for this part of the system. The reservoir level controls the pumps at Coopers wells, turning them off when the reservoir capacity reaches 87% and turning them on when the water level drops below 75%. There is a high level alarm activated at 90% and a low level alarm at 60%. 3.3 Distribution System The whole of Gore s reticulation can be fed off one or other of the treatment plants. Historically Gore was considered as two separate distribution zones but is now included in the drinking-water register as a single distribution zone. Gore s reticulation has three higher level areas which are serviced by pump stations. The largest of these is the pumping station within the water tower at Hilbre Ave which replaced the water tower s gravity system as the means to supply water to the high areas of North Gore. A backup generator near to the pumps can provide electricity if the mains supply fails. There is also a booster pump station at the Wentworth St water treatment plant known as the Talbot Street pumping station. The booster pumps here supply water to the Talbot Street tanks which provide water under gravity to 14 properties located at a higher level. The third pumping station in the Gore reticulation is the Charlton Rd pump station which pumps water to what was formerly the Department of Scientific and Industrial Research (D.S.I.R). The rising main from this pumping station runs for 1.87 km and services 11 properties. Generally, the pressure in the reticulation is good. There are nine different water quality sampling sites in the Gore reticulation. Tests for E. coli, FAC and ph are conducted 16 times per quarter with a maximum allowance of 11 days between samples and at least five different days of the week each quarter. E. coli results for the reticulation are consistently zero. The average FAC value obtained from the sampling has been 0.46 mg/l

9 Gore Public Health Management Plan Figure 1 Map of Gore Water Supply Key Infrastructure Figure 8: Sampling Point Locations for the

10 Gore Public Health Management Plan Figure 2 Map of Gore Water Supply Reticulation

11 Gore Public Health Management Plan 5 Photographs of the Gore Water Supply System Figure 3 Jacobstown well Figure 4 Jacobstown bore Figure 5 New Coopers well Figure 6 Older Coopers well Figure 7 Hilbre Ave sand filters Figure 8 Hilbre Ave aeration tower

12 Gore Public Health Management Plan Figure 9 Hilbre Ave caustic soda storage Figure 10 Hilbre Ave on-line monitoring Figure 11 Hilbre Ave chlorine storage Figure 12 Pressure pumps for higher levels of North Gore Figure 13 Wentworth St treatment plant Figure 14 Wentworth St backup generator

13 Gore Public Health Management Plan Figure 15 Wentworth St on-line monitoring Figure 16 Wentworth St reservoir 6 Flow Chart Schematic of Supply Below is a schematic of the Gore water supply showing the critical points for the supply. Critical point 1 Critical point 2 Critical point 3 Critical point 4 Critical point 5 Critical point 6 Booster pumps High level reticulation Jacobstown wells Pressure filters Aeration Chlorine dosing ph adjustment Storage Reservoirs Low level reticulation Coopers wells High level East Gore Aeration Storage Reservoirs Barrier: Groundwater and sanitary boreheads provide a partial barrier to microbiological contamination. Barrier: Chlorination provides a barrier to nonprotozoan microbiological contaminants. Barrier: Reservoirs are covered to prevent ingress of rainwater or contaminants and to exclude birds and vermin providing a partial barrier to contamination. Barrier: Chlorine dosing is done at a level to provide a partial barrier to microbiological contamination throughout the reticulation system. Figure 17 Critical Point Schematic of Gore Water Supply

14 Gore Public Health Management Plan 7 Critical Points and Barriers to Contamination Critical points where hazards can be eliminated, minimised or isolated include: Table 2 Critical Points 1 Critical Point Shallow groundwater well primary sources 2 Pressure filters 3 Chlorine and ph dosing Description Well/Pumping failure means eventual loss of supply Failure will result in raw water turbidity not being reduced Failure will result in a lack of bacterial and viral control Overdosing may exceed the chemical MAV 4 Treated water storage Possible point for microbiological recontamination 5 Booster Pumps 6 Distribution system connections and distribution system hydrants Failure of booster pumps means an inability to supply the higher reticulation levels with adequate water Possible access point for recontamination from events such as backflow. 8 Barriers to Contamination Groundwater Sources The supply bores are sealed and have concrete aprons to prevent contaminant ingress. The area around the bores is fenced to prevent access by stock. This provides a partial barrier to microbiological contamination. Filtration Pressure filtration at Hilbre Ave treatment plant provides a partial barrier to bacterial and protozoal contamination. Chlorination The chlorine dosing and subsequent reservoirs/tank farms provide sufficient contact time for chlorination to be a barrier to bacterial and viral contamination. Storage Reservoirs The reservoirs at Wentworth Street treatment plant are covered and enclosed to prevent ingress of rainwater or contaminants and to exclude birds and vermin. The reservoir at Hilbre treatment plant is covered but is not secure against birds and vermin. These measures provide a partial barrier against recontamination of water following treatment

15 Gore Public Health Management Plan Distribution Network The following measures provide a partial barrier against recontamination of water following treatment: Chlorine dosing is provides FAC at a level to protect the water against microbiological contamination throughout the system. Backflow prevention measures are taken for commercial premises. All distribution system maintenance is undertaken in a sanitary manner. Operators are trained and experienced. 9 Improvement Schedule The improvement schedule outlines improvements that have been recommended for preventing, reducing or eliminating the identified public health risks in the Gore 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. GMDA = General Manager District Assets = 3 Waters Asset Manager AO = Assets Officer = Essential Services Supervisor TPO = Water TP Operators

16 Gore Public Health Management Plan Table 3 Capital and Significant Projects Priority Level Water Supply Area Reference to Table Proposed Works Person Responsible Expected Cost Intended Completion Date 1 Very high Chlorination 4.2, 4.3, 4.4, 4.5, 4.6, 4.8, 4.9, 4.10 Investigate installing an automatic plant shut down system when FAC is above or below a set point. Investigation $ High Catchment Filtration 1.1, 1.2, 3.1, 3.2, 3.3, 3.5, 3.6 Investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. Investigation $20, Catchment 1.4 Investigate options for developing new sources or rationalising the existing sources so that security of the supply quantity is achieved. GMDA Investigation $50, Abstraction Reticulation 2.6, 7.5 Develop and implement a backflow prevention policy AO $ Low Filtration (Hilbre Ave) 3.4 Connect pump station backup generator so that it can also run the treatment plant TPO $

17 Gore Public Health Management Plan Table 4 Operational Improvements and Minor Projects Priority Level Water Supply Area Reference to Table Proposed Works Person Responsible Expected Cost Intended Completion Date 1 Very high Filtration ph adjustment 3.7, 5.4, 8.2 Implement a programme for calibration of all on-line monitoring equipment and retain calibration records. Staff time Catchment 1.2 Monitor land use changes in the recharge zones and the raw water quality in the wells. GMDA Staff time On-going 3 Storage reservoirs 6.1 Undertake an assessment of the bird and rodent security of the Hilbre Ave reservoir. TPO Staff time Reticulation 7.4 Develop protocols for staff or contractors undertaking work on water supply pipes to ensure all work is carried out in a sanitary and hygienic manner. Staff time $ Reticulation 7.7, 7.9 Prepare a flushing procedure and implement a flushing programme. Staff time Reticulation 7.1 Establish and record reticulation failure history on asset management system. Staff time Storage reservoirs 6.4 Implement a programme to clean the storage reservoirs. Staff time Storage reservoirs 6.5 Programme structural integrity checks of reservoirs. Staff time $

18 Gore Public Health Management Plan 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. Identifying the treatment requirements for the supply and upgrading the treatment plant so that it has an effective and DWSNZ compliant process for the control of protozoa will reduce the risk of protozoan illness in consumers. The installation of an automatic plant shutdown based on excessive or insufficient chlorine residuals will reduce the risk of bacterial and viral contaminated water being provided to consumers. It will also reduce the risk of producing disinfection byproducts. It will also reduce the risk of taste and odour complaints due to over chlorination. The installation of a backflow prevention programme will reduce the risk of the distribution system becoming contaminated. The recommended operational improvements will improve operation of the supply. 11 Methodology This PHRMP has been prepared consistent with the approaches recommended by the Ministry of Health. Supporting documents include the PHRMP Guides and A Framework on How to Prepare and Develop Public Health Management 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. Indicative cost estimates and implementation timeframes have been prepared for the required improvement measures. 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 3Waters Asset Manager is responsible for implementation of the Improvement Plan within the timeframes indicated, subject to community and council approvals, funding constraints and availability of resources. The 3 Waters Asset Manager is also responsible for on-going review and updating of the PHRMP and associated Improvement Schedule. 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. 3 Waters Asset Manager 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: Catchment Abstraction and Raw Water Pipelines Filtration (Hilbre Ave) Chlorination ph Adjustment Storage Reservoirs Reticulation Other

19 Gore Public Health Management Plan 12 Ranking Procedure Potential public health risks have been evaluated using the Likelihood and Consequence scales tabulated below to determine a risk level low, moderate, high, very high or extreme. The assessed risk level allows prioritisation of the associated improvement measures. Table 5 Likelihood Scale Likelihood Almost certain Likely Possible Unlikely Rare Description Is expected to occur in most circumstances. Will probably occur (once in 1 yrs) Might occur at some time (once in 5 yrs) Could occur at some time (once in 25yrs) Only in exceptional circumstances (once in 50yrs) Table 6 Consequence Scale Consequences Insignificant Minor Medium Major Catastrophic Insignificant public health impact Description Minor public health impact or inconvenience to supply users public health impact and/or short term loss of supply Major public health impact and/or loss of supply for a long period. Small number of water-borne illnesses Major public health impact. Significant water-borne illness Table 7 Level Allocation Table Consequence Likelihood Insignificant Minor Medium Major Catastrophic Almost certain Very High Extreme Extreme Likely Low High Very High Extreme Possible Low Very High Very High Unlikely Low Low High Very High Rare Low Low Low High

20 Gore Public Health Management Plan 13 Drinking Water Standards, and Grading Compliance of the Gore drinking water supply with the DWSNZ is set out in the table below. The supply is currently not graded. Table 8 Summary of Compliance with DWSNZ Standards compliance assessed against 2005 (revised 2008) Secure bore water? Bacterial compliance criteria used for water leaving the treatment plant Protozoa log removal requirement required for the supply Protozoa treatment process Compliance criteria 6A or 6B is used for water in the distribution zone? Bacterial compliance for water leaving the treatment plant was achieved for the 2011/2012 year? Protozoa compliance for water leaving the treatment plant has been achieved for the 2010/2011 year? Bacteria compliance for water in the distribution zone has been achieved for 2010/2011 year? P2 determinands allocated to supply? Chemical compliance achieved for the last 4 quarters? Cyanobacteria identified in the supply? Cyanobacterial compliance has been achieved for the last 4 quarters? Laboratory undertaking analyses? No 2A To be assessed None 6B No No No N/A Watercare 14 Consultation In April 2013 a site visit to the Gore water supply was carried out by Opus and discussions were held with relevant Gore District Council staff, particularly Paul Withers, General Manager District Assets, Sarah Dowling, 3 Waters Asset Manager, and Ian Lowe, Essential Services Supervisor. An inspection of the water sources, treatment plants and reservoirs was undertaken and operation of the plant was discussed with the supply operator Corey Reed. As part of the site visit, discussions covered the operation and performance limits of the plant, the critical points, operation of treatment barriers, the risks that have been identified, how these risks are managed currently and the improvements that could be put in place. A drive through of parts of the community that is serviced was included. Subsequent to this consultation telephone discussions and contact has been used to provide further information necessary for the preparation of this PHRMP. The PHRMP was then reviewed by Sarah Dowling prior to completion

21 Gore Public Health Management Plan The information provided during this consultation has been used to compile the risk tables. 15 Contingency Plan Table 9 Contingency Plan for Gore Water Supply Gore Water Supply Contingency Plan Type of Event Required Contingency Action Severe microbiological contamination of source water (such that treatment is ineffective) Indicators: A contamination event in the catchment may be observed by or reported to GDC staff. May also be indicated by reported illness among consumers or positive E. coli monitoring results. Issue Boil Water notice Increase chlorination and FAC levels Advise Drinking Water Assessor (DWA) Inspect catchment and wells to identify source of contamination and rectify problem as quickly as possible Consider provision of emergency treatment or alternative water supply (e.g. tankers) Disinfect contaminated reservoirs and flush mains Keep customers informed and advise once regular service is restored Chemical contamination of source water Indicators: A contamination event in the catchment may be observed by or reported to GDC staff. May also be indicated by reported water quality concerns from consumers (taste, odour, colour) or illness among consumers. Advise Drinking Water Assessor (DWA) Assess situation and advise customers regarding use/treatment/disposal of contaminated water Arrange emergency water supply (tankers) if necessary Inspect catchment and intake to identify source of contamination and rectify problem as quickly as possible Flush contaminated reservoirs and mains Keep customers informed and advise once regular service is restored Insufficient water available for abstraction and treatment or loss of ability to take water from wells. Indicators: Observed or reported low water levels in wells or bore. Observed or reported low Mataura river flow level. Advise customers to conserve water Implement demand management strategies as required Activate emergency water sources if necessary Arrange emergency water supply (tankers) if necessary Keep customers informed and advise once regular service is restored

22 Gore Public Health Management Plan Gore Water Supply Contingency Plan Type of Event Required Contingency Action E. coli transgression in water leaving treatment plant or distribution zone Indicators: E. coli transgression reported following routine monitoring. Follow transgression response procedure in DWSNZ Advise Drinking Water Assessor (DWA) Commence daily E. coli testing at WTP Use an enumeration test method Sample in distribution system Investigate cause, inspect plant and wells Take remedial action Continue to sample for E. coli until 3 consecutive samples are free of E. coli If E. coli is found in repeat samples consult with DWA, intensify remedial action, increase disinfection, consider Boil Water notice, consider alternative supply Inadequate chlorination Indicators: Low FAC reported from treatment plant monitoring. Inspect treatment plant to identify cause of problem and rectify as quickly as possible Manually chlorinate reservoirs Advise DWA and issue boil water notice if appropriate, i.e. if cannot reinstate adequate chlorination Make arrangements for provision of emergency treatment or alternative water supply Keep customers informed and advise once regular service is restored Severe turbidity of source water and turbidity passing through Hilbre Street treatment plant. Indicators: Highly turbid water arriving at the plant may be observed by or reported to GDC staff. May also be indicated by reported water quality concerns from consumers (taste, colour) or illness among consumers. Cease abstraction from turbid well and supply from other wells or treated water storage. Monitor reservoir level. Monitor source water turbidity Recommence abstraction and treatment when turbidity level drops such that treatment is effective If reservoir storage is low and effective treatment cannot be resumed then advise DWA and issue Boil Water notice Keep customers informed and advise once regular service is restored

23 Microbiological Contamination Catchment Assessments 16 Tables GMDA = General Manager District Assets = 3 Waters Asset Manager AO = Assets Officer = Essential Services Supervisor TPO = Water TP Operators 1. Catchment Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 1.1 Contamination entering the shallow aquifers from agricultural activities (particularly animals) in the recharge zones Very high (likely x major) High raw water E. coli results. Turbidity in raw water. Illness in community. Coopers wells have concrete aprons installed to prevent surface water ingress and are fenced to exclude stock for 5 metres. Jacobstown wells have concrete aprons installed to prevent surface water ingress and are located in an area that is fenced to exclude stock. Partially Investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. Relationships are maintained with farmers and the Regional Council

24 Chemical Contamination Microbiological Contamination Catchment Assessments 1. Catchment Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 1.2 Land use change in catchment. (Particularly dairy discharges) High raw water E. coli readings. Increased turbidity in raw water. Changes to District Plan. Chlorination treatment at all sites. Ability to challenge resource consents. Rules and regulations within district plan. Partially Monitor land use changes in the recharge zones and the raw water quality in the wells. Investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. GMDA Applications for resource consents for activities in catchment. 1.3 Surface runoff containing chemical contaminants from agricultural and industrial activities (e.g. pesticides, nutrient fertilisers and oils) Taste and/or odour. Complaints or information provided by public about activities in catchment. Suite of chemical determinands are tested minimum every 5 years None required

25 Inadequate Quantities of Water Catchment Assessments 1. Catchment Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 1.4 Low surface runoff and flows in streams needed for aquifer recharge Demand exceeding consent conditions for low flows. Very high major) Inability to extract enough water Restrictions imposed by regional council Wells near to the abstraction wells can be recharged with river water, recharging the groundwater in the areas where water is abstracted Partially Investigate options for developing new sources or rationalising the existing sources so that security of the supply quantity is achieved. GMDA

26 Inadequate water quantity Inadequate water quantity Inadequate water quantity No supply or low volume of supply Catchment Assessments 2. Abstraction and Raw Water Pipelines Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 2.1 Intentional vandalism or accidental damage to well heads High major) Obvious signs of damage to structure. Reduced flow to treatment plant. Option of four operational wells and three emergency sources 24 hours of treated water storage. Low None required TPO Coopers wells on private property. 2.2 Failure of Jacobstown pressure pipeline to treatment plant Reduced flow or no flow to treatment plant Pipeline repair materials held in store None required 2.3 Failure of Coopers pressure pipeline to treatment plant Reduced flow or no flow to treatment plant Pipeline repair materials held in store None required 2.4 Power Failure at well pumps (Possible x No flow to treatment plant Telemetry alarm 18 hours treated storage Use other intakes if available. Low None required TPO Generator set available at Coopers

27 Microbiological or Chemical Contamination Inadequate water quantity Catchment Assessments 2. Abstraction and Raw Water Pipelines Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 2.5 Failure of Intake Pump(s) (Possible x No flow to treatment plant. Telemetry alarm 18 hours treated storage There are two wells at each intake. Low None required TPO 2.6 Illegal connections into the raw water pipelines Less than anticipated flows of water going into the treatment plants during Summer Taste and/or odour. 18 hrs of treated water storage Regulation and enforcement of illegal connections Partially Develop and implement a backflow prevention policy AO Complaints or information provided by public about illegal activities

28 Particulate material not removed Particulate material not removed Particulate material not removed Catchment Assessments 3. Filtration (Hilbre Ave.) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 3.1 Backwashing failure (backwash pump, underdrain or nozzles fail) Very high (likely x major) High turbidity in water leaving the filter. Complaints about water quality from consumers. Low water level in chlorine contact reservoir. Telemetry alarm on high turbidity Manually operated and manually shut down. 18 hours treated water storage No High (likely x Assess the on-going suitability of the existing filters and investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. GMDA 3.2 High suspended solid loads during peak demand periods. Very high (likely x major) High turbidity in water leaving the filter. Increased frequency of backwashing required. Complaints about water quality from consumers. Telemetry alarm on high turbidity Ability to manually shut down the plant. 18 hours treated water storage Partially High (likely x Assess the on-going suitability of the existing filters and investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ.. GMDA 3.3 Media loss from excessive backwashing rate or deterioration of filtration media. Very high (likely x major) High turbidity in water leaving the filter. Increased frequency of backwashing required. Complaints about water quality from consumers. None. No Very high (likely x major) Assess the on-going suitability of the existing filters and investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. GMDA

29 Particulate material not removed Particulate material not removed Catchment Assessments 3. Filtration (Hilbre Ave.) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 3.4 Inability to backwash effectively due to local power outage High turbidity in water leaving the filter. Complaints about water quality from consumers. Telemetry alarm on high turbidity Ability to shut the plant down manually. 18 hours treated water storage Partially Low insignificant) Connect pump station backup generator so that it can also run the treatment plant TPO 3.5 Backwash water from the pressure filters enters the water to the reservoir High turbidity in water leaving the filter. Complaints about water quality from consumers Filters can be manually backwashed Telemetry alarm on high turbidity Ability to shut the plant down manually. Assess the on-going suitability of the existing filters and investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. GMDA 18 hours treated water storage

30 Particulate material not removed Particulate material not removed Catchment Assessments 3. Filtration (Hilbre Ave.) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 3.6 Existing filtration inadequate for removal of particulate material to log level required by DWSNZ. High (likely x Existing filtration cannot meet the DWSNZ protozoa log removal requirements. Filtered water turbidity exceeds 0.5NTU Filtration provides some unverifiable protozoa protection. On-line turbidity monitoring of water leaving the filters. No High (likely x Assess the on-going suitability of the existing filters and investigate the installation of treatment processes which meet the bacterial and protozoal requirements of the DWSNZ. GMDA Turbidity of filtered water is monitored. 3.7 Turbidity of filtered water is not known High (likely x Records of turbidity meter calibration are not held. Turbidimeters are not calibrated Turbidity meters are installed on filtered water but not calibrated. No High (likely x Implement a programme for calibration of all on-line monitoring equipment and retain calibration records

31 Inadequate Chlorination Inadequate Chlorination Inadequate Chlorination Catchment Assessments 4. Chlorination (Hilbre Ave and Wentworth St WTPs) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 4.1 Inadequate contact time during peak demand. Lack of storage after treatment E. coli detected in water leaving the treatment plant. 18 hours of storage is provided in reservoirs This provides sufficient contact time. Low (rare x None required TPO 4.2 Chlorine gas supply exhausted. Very high major) Illness in community. FAC is less than 0.5 mg/l or E. coli detected in water leaving treatment plant. Bulk duty (920kg) Standby (70kg) chlorine gas cylinders at Wentworth St. Weight of chlorine is measured through chlorine scales Very high major) Investigate installing an automatic plant shut down system when FAC is below a set point. Continuous FAC monitoring with results transmitted back to Council via telemetry. 4.3 Chlorinator failure. Very high major) Illness in the community. FAC is less than 0.5 mg/l or E. coli detected in water leaving treatment plant. Continuous FAC, ph and turbidity monitoring transmitted back to Council via telemetry. Partially Very high major) Investigate installing an automatic plant shut down system when FAC is below a set point

32 Inadequate Chlorination Inadequate Chlorination Inadequate Chlorination Catchment Assessments 4. Chlorination (Hilbre Ave and Wentworth St WTPs) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 4.4 Chlorine dose level incorrectly set. FAC is less than 0.5 mg/l or E. coli detected in water leaving the treatment plant. Continuous FAC monitoring and low alarm transmitted back to Council. Operators check chlorine levels and can adjust set-points if required. Partially Investigate installing an automatic plant shut down system when FAC is below a set point. 4.5 Chlorine analyser failure. FAC is less than 0.5 mg/l or E. coli detected in water leaving the treatment plant. No FAC detected or unusual FAC result Weekly colorimetric comparison to check analyser. Continuous FAC monitoring and low alarm transmitted back to Council. Partially Investigate installing an automatic plant shut down system when FAC is below a set point.. Annual service maintenance contract. 4.6 High chlorine demand. FAC is less than 0.5 mg/l or E. coli detected in water leaving the treatment plant. Continuous FAC monitoring and low alarm transmitted back to Council. Partially Investigate installing an automatic plant shut down system when FAC is below a set point. Need to increase chlorine dosing set point. Odour complaints Operators check chlorine levels and can adjust set-points if required

33 Over Chlorination Over Chlorination Inadequate Chlorination Inadequate Chlorination Catchment Assessments 4. Chlorination (Hilbre Ave and Wentworth St WTPs) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 4.7 Chlorinator failure due to local power failure. Very high major) FAC is less than 0.5 mg/l or E. coli detected in water leaving the treatment plant. 24 hours reservoir storage. Standby power generators available Low None required TPO 4.8 Lack of chlorine due to dosing pipe failure or leak. High major) Illness in the community. FAC is less than 0.5 mg/l or E. coli detected in water leaving the treatment plant. Continuous FAC monitoring and low alarm transmitted back to Council. Regular visual checks Low (Unlikely x Investigate installing an automatic plant shut down system when FAC is below a set point. 4.9 Chlorinator failure. Very high (Possible x major) FAC level high. Odour and taste. Complaints from consumers. Continuous FAC monitoring and high alarm transmitted back to Council. Partially Investigate installing an automatic plant shut down system when FAC is above a set point Chlorine dose level incorrectly set. (Possible x FAC level high. Taste complaints. Residual based chlorine dosing Continuous FAC monitoring transmitted back to Council via telemetry. Partially Low Investigate installing an automatic plant shut down system when FAC is above a set point

34 ph Level Incorrect ph Level Incorrect ph Level Incorrect Catchment Assessments 5. ph Adjustment (Hilbre Ave and Wentworth St WTPs) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 5.1 Caustic soda dosing pump failure. ph less than 7 or greater than 8. Continuous ph monitoring transmitted back to Council by telemetry. Low None required TPO 5.2 Chemical supply exhausted. Low ph less than 7 or greater than 8. Continuous ph monitoring transmitted back to Council by telemetry. Low Minor) None required TPO Operators check caustic soda storage levels regularly 5.3 Inappropriate or poor quality chemicals used. Unusual ph record All chemicals are purchased from an ISO accredited chemical supplier. None required TPO

35 ph Level Incorrect Catchment Assessments 5. ph Adjustment (Hilbre Ave and Wentworth St WTPs) Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 5.4 Incorrect ph level due to monitoring failure Unusual ph record Consumer complaints No records of monitoring equipment calibration ph on-line monitors calibrated from time to time Partially Implement a programme for calibration of all on-line monitoring equipment and retain calibration records. TPO

36 Microbiological Contamination Microbiological Contamination Microbiological Contamination Catchment Assessments 6. Storage Reservoirs Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 6.1 Leakage of surface water through reservoir roofing or flooring. Illness in community. Reduced FAC in water leaving the treatment plant. E. coli detected in water leaving treatment plant. Residual chlorine maintained in water. Wentworth St reservoir has been shown to be secure FAC tested frequently. Partially Undertake an assessment of the bird and rodent security of the Hilbre Ave reservoir. TPO 6.2 Contamination through insanitary maintenance or sampling procedures. E. coli in water leaving reservoir. Decreased FAC in water leaving reservoir. Residual chlorine maintained in water. Only trained supply operators or contractors under supervision carry out maintenance or sampling. None required 6.3 Vandalism to reservoir. (Possible x E. coli in water leaving reservoir. Decreased FAC in water leaving reservoir. Residual chlorine maintained in water. Properties are fenced and gates locked Non required TPO Evidence of reservoir entry

37 Loss of water Discoloured water Catchment Assessments 6. Storage Reservoirs Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 6.4 Sediment accumulation within reservoirs Visible suspended matter in water exiting reservoir. Decreased FAC in water leaving reservoir. Residual chlorine maintained in water. Partially Implement a programme to clean the storage reservoirs. TPO Complaints from consumers 6.5 Leakage from reservoir Low water level in reservoir. Alarm on low level. Partially Programme structural integrity check of reservoirs. AO

38 Loss of Supply Loss of Supply Loss of Supply Catchment Assessments 7. Reticulation Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 7.1 Pipe failure. Complaints from consumers about loss of supply. Change in flow or pressure in reticulation. Council requires all work and materials used in reticulation to meet the specifications determined by GDC. Pipe line renewal programme in place Partially Establish and record reticulation failure history on asset management system. AO 7.2 Booster pump failure (Hilbre Ave Water Tower, Talbot Street, Charlton) Complaints from consumers about loss of supply. Change in flow or pressure in reticulation. SCADA alarm More than one pump available for boosting at Hilbre Ave. Flow is pumped into storage tanks which provide the consumers with gravity feed. Low insignificant) None required TPO Genset can provide power for pumps. 7.3 Power failure to booster pumps SCADA alarm Information from electricity supplier. Flow is pumped into storage tanks which provide the consumers with gravity feed. Low insignificant) None required TPO Complaints from consumers about loss of supply. Genset can provide power for pumps

39 Microbiological Contamination Microbiological Contamination Catchment Assessments 7. Reticulation Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 7.4 Inadequate controls on maintenance and construction work. Illness in community. Complaints from consumers about taste or odour. Standard health and safety plans must be followed by staff contractors. Partially Develop protocols for staff or contractors undertaking work on water supply pipes to ensure all work is carried out in a hygienic and sanitary manner. E. coli present in reticulation system. Inadequate FAC in reticulation. 7.5 Backflow from consumer connections. Illness in community. Contaminants present in the reticulation system. Industrial users required to install backflow prevention devices. Partially Develop and implement a backflow prevention policy. Reduced FAC in water Taste or odour complaints from consumers

40 Microbiological Contamination Microbiological Contamination Catchment Assessments 7. Reticulation Event No Cause Without Measures Indicators Measures in Place Controlled Residual Additional Measures That Could be put in Place Resp. 7.6 Breaks or leaks in pipes Contaminants present in the reticulation system. Taste or odour complaints from consumers. Reduced FAC in water. Chlorine residual maintained in water. Breaks and leaks repaired as a priority. Microbiological sampling programme that meets the requirements None required Pipes under positive pressure 7.7 Poor circulation of water in network leading to biofilm growth. Contaminants present in the reticulation system. Taste or odour complaints from consumers. Reduced FAC in water. Dead ends are flushed from time to time. Flushing undertaken in response to complaints. Residual chlorine maintained in water. Partially Prepare a flushing procedure and implement a flushing programme. AO