CHLORINE FREE WATER SUPPLY TRIAL FOR MOSSMAN TOWNSHIP

Transcription

1 66 WATER & WASTE COMMITTEE 20 APRIL CHLORINE FREE WATER SUPPLY TRIAL FOR MOSSMAN TOWNSHIP B. Gardiner: 24/20/137-01: # RECOMMENDATION: That Council advise the Douglas community via a consultation process that it will not proceed with a chlorine free water supply trial in Mossman township due to the following: 1. The significant costs of required preparatory work as recommended by Black & Veatch consultants ($2.75 to $4.95 million) 2. The degree of uncertainty that the trial will actually succeed 3. The significant potential costs (over $12 million) for preparatory work to extend chlorine free water supply trial to other supplies in the Douglas area 4. The potential health risks associated with residual disinfection free water supplies 5. Council s legal obligations to provide safe drinking water to all sectors of the public. INTRODUCTION: A report was presented at the January 2010 Ordinary Council meeting on the draft Black & Veatch report into the possibility of conducting a chlorine free trial for the Mossman water supply. The final report has now been received and reviewed by Council staff. The resource implications of undertaking the pre-trial activities recommended by Black & Veatch have now been assessed. The results of the assessment are provided in this report for a decision by Council on how they wish to proceed on this matter. The strong desire of the Douglas community to achieve chlorine free water supply is recognised and acknowledged. This desire needs to be balanced against the cost and resource implications of undertaking the preparatory work prior to a chlorine free trial. Council also needs to consider the risks associated with the trial not being successful despite the best efforts of staff and Council advisors. In addition, the potential extension of the chlorine free supply to Port Douglas, Whyanbeel and Daintree will also have potentially significant cost and resource implications.

2 67 BACKGROUND: Council has been working with the Douglas Community Water Reference Group (DCWRG) since September 2008 on the management of water quality issues in the Mossman/Port Douglas, Whyanbeel and Daintree Village water supplies. There have been 10 meetings of the Group and 8 separate reports to Council on Douglas water quality matters, not including reports containing DCWRG meeting minutes. There have also been 5 briefings to Council on Douglas water quality issues. The water supplies in the region had been operated without any form of water treatment for decades up until Following the construction of membrane filtration plants in 2004, the systems operated with a high level of treatment but without residual disinfection (eg chlorination). Residual disinfection is traditionally used in almost all water supplies in Australia to maintain water quality once treated water leaves a treatment plant and enters the pipe network. The 3 Douglas Water supplies have been chlorinated since October 2009 as a result of Public Health Orders issued by Queensland Health in response to continued water quality issues. In late 2009 the Douglas Community Water Reference Group (DCWRG) requested that Council develop a protocol to allow a chlorine free water supply trial to occur in the Mossman supply. Council subsequently engaged the services of Black & Veatch Australia in September 2010 to advise Council on whether a chlorine free water supply trial could be implemented and to assist in finalising a draft protocol for the trial. Council received the draft report from Black & Veatch on 21 December 2010 which was reviewed over the Christmas break and early January. A number of matters required clarification prior to finalisation of the report. The final report has now been received and a copy has been provided to Queensland Health for their review and comment. The Black & Veatch report identifies a series of tasks that they consider need to be completed prior to a chlorine free trial being undertaken and have provided preliminary costings for this preparatory work. They have also updated the draft protocol for conducting a chlorine free water supply trial in Mossman Township. The preliminary cost estimates and resource implications of the preparatory work to be completed before a chlorine free trial can be attempted have been reviewed by staff within the context of: Reviewing the feasibility of the tasks Developing more accurate costings Identifying staff resource implications Identifying customer impacts of the pre-trial tasks.

3 68 COMMENT: 1. Key findings of the Black & Veatch report The key findings of the Black & Veatch report with regard to their review of the current Mossman water supply system are as follows: - Based on the limited sampling undertaken to date, the raw water source is not as microbiologically pure as has been assumed in a number of prior reports - Treated water after storage within the Mossman and Port Douglas Reservoirs has, at times, had higher levels of microbes than should be present in treated water - Water quality within the reticulation system typically degrades as the water is transported throughout the system. 2. Is a chlorine free trial possible? Black & Veatch conclude that a chlorine free trial should be possible as chlorine free supplies are provided to large populations such as in the Netherlands and parts of Germany. These water supplies rely on: 1. A very high degree of treatment to remove organic matter 2. A comprehensive regime of distribution water quality monitoring and analysis 3. Rigorous maintenance of the distribution system through the following practices: a. Unidirectional mains flushing b. Cross-connection control and documentation c. Storage tank cleaning and maintenance d. Optimised asset renewal and repair using best practices e. Coordination of customer concerns from initial contact through to complaint resolution f. Communication and permitting of all non-utility access to hydrants or other utility assets. 3. Preparatory work required prior to a chlorine free trial Black & Veatch consider that a chlorine free trial should be possible but not until the following actions have been completed: - the quality of the raw water from Rex Creek is fully understood (regular sampling commenced in November 2010) - the performance of the Mossman Treatment Plant is fully evaluated, and the treatment process enhanced if necessary - the integrity of the treated water storage reservoir at Mossman Treatment Plant is improved through replacement of the tank roof - the condition of the distribution system is improved through a comprehensive regime as outlined above in best practices for chlorine-free systems - the quality of the treated water and degree of re-growth within the distribution system is fully understood, and demonstrated to be acceptable for chlorine-free supply

4 69 - a Quantified Microbial Risk Assessment (QMRA) of the system is completed, and any further actions identified in the QMRA are completed. 4. Consultant s cost estimates of preparatory work Black & Veatch were asked to provide preliminary cost estimates of the preparatory work they recommended be undertaken prior to a chlorine free trial. Their estimate of preparatory work is between $820,000 and $3,020,000. The upper estimate relates to the potential need to install further water treatment processes due to the presence of dissolved organic carbon in the raw water supplies. This will not be able to be confirmed until the proposed additional detailed water quality monitoring has been completed. The components of their cost estimate are provided in the following table and discussed below. Black & Veatch preparatory work cost estimates The additional sampling prior to the trial is recommended to firstly establish that the flushing program has been effective, and secondly to confirm that re-growth is not occurring in the distribution system over time.

5 70 The tie-in of the Hospital to the Port Douglas supply has been recommended as the Port supply will continue to be chlorinated throughout the trial. An allowance has been made for other vulnerable communities or customers that may need to continue to have chlorinated supply during the trial. The detention time modelling is required to identify how long treated water stays in the pipe network for and to identify dead ends or low flow areas. This work will assist in ongoing management of water quality and prioritising spot-flushing programs. The QMRA item is for a Quantitative Microbial Risk Assessment of pathogen occurrence in the water supply. Council does not have the expertise to undertake this work. 5. Council cost estimates of preparatory work Council staff have reviewed and refined the Black & Veatch cost estimates. Based on this review, there are additional items and cost variances from the consultant s costs. The additional and variation items are shown in the following table and discussed in detail below. Cairns Regional Council preparatory cost estimates Cairns Regional Council Item Council cost Black & Veatch cost Unidirectional Flushing Program $255,413 $90,000 Non-Revenue Water Use $41,738 Traffic control $204,673 Backflow Checks $2,703 Installation of Sample Points $16,500 $10,000 Management of access to Hydrants $80,000 Additional sampling prior to trial $396,792 $210,000 Turbidity Meter and Fluoride works $48,700 Upgrade UV system $195,000 Valve-Hydrant Replacement $1,000,000 Total $2,241, Unidirectional Flushing Program The water distribution network has operated for many decades with raw creek water flowing through it. This means that over time, the network has accumulated sediment and other organic material during periods when the raw water quality was poor. While localised areas would have been flushed based on customer complaints, there is no record of any systematic flushing program to cleanse the pipe network.

6 71 The unidirectional flushing program is not just a simple process of opening valves and flushing. What has been proposed by Black & Veatch is a systematic, structured and documented process of flushing with a forceful flow of 1.5 to 2 metres per second to scour pipe walls and remove loose corrosion products. Flushing needs to progress from the treatment plant, through each section of the network until the end of the system. Every valve and hydrant in the network must be exercised and every dead-end flushed. Hydrants are located 60m apart in the Mossman network. Turbidity measurements need to be taken until the target turbidity of 0.1 NTU is reached which from trials we have conducted could take several hours. Water samples would also be collected for laboratory testing for bacteriological characterisation. A significant volume of water will be required to be used for the unidirectional flushing program particularly in the first year. This volume of water has the potential to flood low-lying areas and cause traffic hazards where it lies on the roads. Black & Veatch suggest that this water should be disposed of to sewer which would add treatment costs. As an alternative option it could be de-chlorinated then discharged to waterways. Logistically management of the flushing water will be very difficult given the large volume and the location of hydrants across the network. It is also likely that we will receive complaints from the public due to water wastage and flooding of property. This is particularly so given Council is about to embark on an active demand management campaign to defer the need for a new supply. Flushing trials have been undertaken in the Douglas area recently and complaints have arisen. There will also be an interruption of service for customers during the flushing program. Customers would be encouraged to reduce consumption to ensure that there is enough flow and pressure to scour the mains. In addition they will experience reductions in water pressure during the flushing period which could be several hours at a time. To try and minimise customer impacts, staff have explored the option of undertaking flushing at night. While this may limit customer impacts, it would increase the labour cost of the program from $170,000 to over $600,000 due to penalty rates applying. It is estimated that the flushing program will take up approximately 45.5 weeks to complete with a work crew working full-time on the program.

7 72 We have included estimated of computer modelling (provided separately by Black & Veatch) in the costs for the flushing program. Our estimate includes purchase of the software and training and is $85,000 based on quotes received from suppliers. Hydrant flushing in Douglas area 5.2 Non-revenue water use This is the estimate of the value of the water that would be used during the unidirectional flushing program during the first year. The program would be repeated annually but the expectation is that the volume of water required would reduce after the first year. 5.3 Traffic Control We will be required to have traffic control for many of the flushing sites. An estimate of $204,673 has been provided of the cost of traffic control contractors. Traffic control will also be required during the valve and hydrant replacement program for many of the sites but has not been included in the cost estimates in the table due to uncertainty on the actual hours required. 5.4 Valve-hydrant replacement Black & Veatch have indicated that a program of hydrant and valve repair and replacement may need to be completed prior to the flushing program. There are 341 hydrants and 192 valves in the Mossman network. Based on field experience, many of the hydrants are significantly blocked with the best method of cleaning being replacement (see photos below). Similarly many of the valves would also be in poor condition and may need replacement. A cost estimate based on having to replace approximately two-thirds of the valves and hydrants is $1,000,000 which would be a capital budget item and not affect the operating budget.

8 73 The time estimate to complete the hydrant and valve replacement work is 53.3 weeks. This work is required to be completed in any case. However, it would normally be undertaken on a scheduled program over 8 to 10 years as done elsewhere in the Council area. Photographs of clogged hydrants in the Douglas area 5.5 Additional sampling prior to trial Black & Veatch recommend that additional sampling be undertaken over a 9 month period to establish whether the reticulation network is stable and the bacteriological regrowth potential of the system. This will include sampling and analysis of the raw water and more discrete testing of the treatment plant processes. Should the review of this sampling prove positive, then a chlorine free water supply trial may be possible. Our estimate of the cost of the additional sampling program at $396,792 is based on detailed calculations and current day costs. This is higher than the consultant s estimate of $210,000. The B&V estimate did not take into account the labour costs of sampling or the requirement for the daily testing and analysis having to be performed over weekend periods. 6 Combined cost estimate When the Black & Veatch preliminary cost estimate items are combined with the Council revised and additional cost items, the estimated cost of the preparatory work is between $2.752 and $4.952 million. The lower figure would be the cost if the future water quality testing reveals that further water treatment is not required to reduce organic matter. These costs are summarised in the table below.

9 74 Total potential cost estimate for preparatory work Council estimate $2,241,519 Black & Veatch (different items) $510,000 Total $2,751,519 Additional treatment if required $2,200,000 Grand total $4,951,519 7 Assessment of preparedness for a chlorine free trial Black & Veatch recommend that Council should evaluate the success or otherwise of the above work and sampling program in the January to April period of They suggest that this should be done in conjunction with Queensland Health and the DCWRG. Black & Veatch do not consider that a chlorine free trial should commence unless the guideline values of < 50 cfu/100 ml for Heterotrophic place counts (HPC) and < 15 cfu/100 ml for total Coliforms are consistently met. The above approach does not take account of the potential requirement for additional water treatment processes to be installed. This will require analysis of the additional water quality testing of level of dissolved organic matter in the water supplied to the reticulation network. This assessment cannot be undertaken with any degree of certainty unless sampling occurs over a full dry season and a full wet season. Should additional treatment be required there would be a time period of up to 12 months for design, equipment sourcing, procurement, installation and commissioning. 8 Community acceptance of a chlorine free trial While it is clear from the DCWRG that there is a strong view in the vocal community that the Douglas water supplies should be returned to chlorine free, Council should consider some form of consultation with the broader community to advise the community of the proposal and the associated costs and risks. This will be a somewhat difficult task given the complexity of the issue and the linkages with the Council amalgamation. Methods of delivery will need to be reviewed but a targeted phone survey of residents and commercial customers may be the best method of obtaining results that can inform the Council. During any consultation process, particular attention will need to be paid to sensitive customers such as infants, immuno-deficient, the elderly, and commercial customers who provide food.

10 75 9 Chlorine free trial Should the preparatory work on the water supply and the subsequent water quality monitoring indicate that the system is stable, and the results of any consultation process indicate community support, then a chlorine free water supply trial for a 3 month duration could be possible. During the trial water quality monitoring from the raw water and throughout the network would be conducted on a daily, weekly and monthly basis for key indicators as proposed by Black & Veatch. The estimated cost of the laboratory testing for this sampling is $70,000. Black & Veatch have recommended some water quality trigger points (see below) where action would be required to be taken. These actions include a range of options including issuing boil water alerts, flushing, and localised chlorination. Water quality trigger points Indicator E Coli Total Coliforms Heterotrophic plate counts Opportunistic pathogens Trigger point >5 cells per 100ml >15 cells per 100 ml > 125 cells per 100ml > 1 organism per 100 ml In the event that there are repeated failures of the system, a decision point would be reached where Council would need to determine whether the trial should continue or not. 10 Extension of trial to other areas The Mossman system was selected for the proposed chlorine free trial as it has no reservoirs in the network, has a relatively small tourist population and this supply has performed best in terms of drinking water quality. There is little doubt that sections of the Port Douglas, Whyanbeel and Daintree Village communities will request that the chlorine free water supply be extended to their systems should the trial be successful. Based on the report and recommendations from Black & Veatch, there would be reasonably significant costs associated with preparatory work on these water supplies. In addition, it is likely that we would need to undertake trials to ascertain whether chlorine free water supplies would be viable in these water supplies. At this stage the best method of estimating what these costs may be is to use the Mossman system estimates and extrapolate based on the lengths of water main in each system. As can be seen on the table below, there are approximately 210km of water mains in the Port Douglas, Whyanbeel and Daintree networks. This is approximately 4.4 times the length of mains in the Mossman network. Based on the cost estimates for the Mossman system, the estimated cost of preparatory work could be over $12 million excluding any additional treatment costs that might be required at the Whyanbeel and Daintree treatment plants.

11 76 Water supply pipe network lengths Location Pipe length Km Reservoirs Mossman Port Douglas Whyanbeel Daintree Options for consumers to remove chlorine There are several options available to customers who do not wish to drink chlorinated water. These include the purchase and installation of filtration or osmosis systems, boiling water, or letting water stand for several hours in sunlight. There are a range of filtration systems available on the market which claim to remove chlorine. These systems generally use some form of activated carbon to remove some impurities and require regular maintenance to ensure they remain effective and do not themselves generate potential health related contaminants. Only a small percentage of water is used in the home for drinking (generally between 5 and 10%). Customers will also come into contact with chlorinated water when showering, bathing or using other bathroom facilities. Hence removing chlorine from drinking water is not likely to satisfy some residents in the Douglas area. There has been discussion about the Council paying for and providing filtration systems to customers who wish to remove chlorine from their drinking water. This is not seen as a preferred option for several reasons. Firstly, there will be issues with maintenance of any filtration unit provided by Council. Should they not be maintained they will not be effective in removing chlorine and may in fact cause additional water quality problems. Secondly there would be considerable cost to provide filtrations systems as this offer would presumably have to be made to all customers in the Council area. The third issue is that the provision of filters would seem to run counter to the notion that chlorine is added to water supplies at levels that are safe with regard to health impacts, as established by the National Health and Medical Research Council. 12 Options for funding the preparatory work and trial An option for funding the proposed preparatory work and chlorine free trial is to implement a special charge under the provisions of section 92 (3) of the Local Government Act Under this provision a special rate may be levied for services, facilities and activities that have a special association with particular land because the land or its occupiers specially benefits from the service, facility or activity; or has or will have special access to the service. In this case there are 1,576 connections to the water supply network in the Mossman supply area. If the cost of the preparatory work and chlorine free trial were applied to these customers, the approximate cost per connection would be between $1,745 and #3,141. It is suggested that these costs would not be palatable for those residents. However, this option may wish to be explored by Council with the affected residents.

12 77 CONSIDERATIONS: Corporate and Operational Plans: Corporate Plan Goal 4 Delivering Service and Infrastructure: Objective 4.1: Provide a robust, secure, high quality water supply to meet the growing needs of the community. Statutory: Council has obligations under the Water (Safety and Reliability) Act 2008 and the Health Regulation 1996 to provide safe drinking water to the public. Policy: Council s Drinking Water Quality Policy is relevant to this report and in particular the following item in that policy: Consider the needs and expectations of our customers, stakeholders, regulators and employees and integrate appropriate solutions into our planning to provide and maintain safe water supplies Financial and Risk: The financial aspects of the proposed chlorine free trial have been detailed in the body of this report. To summarise, the potential cost of undertaking preparatory work on the Mossman system is $2.752 million. Should additional treatment be required at the Mossman water treatment plant, an additional $2.2 million may be needed. Preparatory work to extend the trial to the Port Douglas, Whyanbeel and Daintree systems could be over $12 million excluding any additional treatment plant process improvement costs at the Whyanbeel and Daintree water treatment plants. Sustainability: Progressing towards a chlorine free water supply trial is in line with community aspirations in the Douglas area. The financial implications of conducting the work prior to the trial and the actual trial will have an impact on Council s operating budget position. CONSULTATION: Black & Veatch have presented the findings of their report to a Councillor workshop, Queensland Health, and the Douglas Community Water Reference Group in February Councillors have been presented the findings of the staff review of the Black & Veatch report at a workshop in March.

13 78 Queensland Health have been provided with a copy of the Black & Veatch report for their comment. At the time of writing the report, formal comment had not been received. OPTIONS: Council essentially has two main options with regard to this matter. Option 1: That Council proceed with the chlorine free water supply trial by completing the following: 1. Undertake the Black & Veatch recommended preparatory work on the Mossman water supply network including the 9-month detailed water quality sampling program. 2. Review the results of the water quality sampling program in consultation with Queensland Health and the Office of the Water Supply Regulator. 3. Concurrently undertake a broad community consultation process to seek feedback on the broader community view about being supplied with residual disinfection free drinking water supply and the willingness or otherwise to pay for the additional cost of providing this service. 4. Should the results of the sampling and community consultation appear favourable, proceed with a 3-month chlorine free water supply trial for the Mossman water supply network including Cooya Beach and Newell Beach. 5. Should the chlorine free trial appear successful, then further consider the extension of the trial to the Port Douglas, Whyanbeel and Daintree Village water supplies. Option 2: That Council advise the Douglas community via a consultation process that it will not proceed with a chlorine free water supply trial in Mossman township due to the following: 1. The significant costs of required preparatory work as recommended by Black & Veatch consultants ($2.75 to $4.95 million) 2. The degree of uncertainty that the trial will actually succeed 3. The significant potential costs (over $12 million) for preparatory work to extend chlorine free water supply trial to other supplies in the Douglas area 4. The potential health risks associated with residual disinfection free water supplies 5. Council s legal obligations to provide safe drinking water to all sectors of the public.

14 79 CONCLUSION: The preferred option is that Council advise the Douglas community via a consultation process that it will not proceed with a chlorine free water supply trial in Mossman township due to the following: 1. The significant costs of required preparatory work as recommended by Black & Veatch consultants ($2.75 to $4.95 million) 2. The degree of uncertainty that the trial will actually succeed 3. The significant potential costs (over $12 million) for preparatory work to extend chlorine free water supply trial to other supplies in the Douglas area 4. The potential health risks associated with residual disinfection free water supplies 5. Council s legal obligations to provide safe drinking water to all sectors of the public. ATTACHMENTS: Nil Bruce Gardiner General Manager Water & Waste