Health Impact Assessment of Central Plains Water Scheme April 2008 Lead agency: Community and Public Health, Canterbury District Health Board HIA lead: Alistair Humphrey Report prepared by: Humphrey A, Walker M, Porteous A, Pink R, Quigley R, and Thornley L Acknowledgements This rapid health impact assessment (HIA) has benefited from the knowledge, experience and skills of many people. A steering group of Alistair Humphrey, Malcolm Walker, Ramon Pink, Andrew Porteous, Louise Thornley and Robert Quigley provided direction and insight into the process. An initial scoping meeting was held and stakeholders were invited to set the boundaries for the HIA. A list of invited members and participants is attached as Appendix 1. A number of people provided valuable advice to the steering group beyond attendance at the meetings; Martin Ward, Margaret Leonard, Carl Hansen, Richard English, Geoff Fougere, Miria Lange, Professors Tony Blakely, Valerie Brown, Peter Crampton, Paul Dalziel, and Karen Witten. Finally, Gina Erceg and others in the administration team of Community & Public Health provided valuable support in word processing and administration, often at short notice at a difficult time of year. 2 Table of contents Acknowledgements................................................................................. 2 Executive Summary ................................................................................ 4 1. Introduction......................................................................................... 6 2. Methodology..................................................................................... 11 2.1. Scope.......................................................................................... 11 2.2. Appraisal ............................................................................................. 21 2.3. Assessment of evidence............................................................. 24 3. Background – water quality .............................................................. 26 4. Findings – water quality.................................................................... 31 4.1. Potential effects of CPWS on water quality......................................... 31 4.2. Potential effects of reduced water quality on health............................ 37 5. Findings – socioeconomic impacts................................................... 42 6. Discussion ........................................................................................ 45 6.1. Relationship between CPWS and water quality.................................. 45 6.2. Potential impact of nitrates on health .................................................. 47 6.3. Potential impact of CPWS on septic tank contamination and flooding 48 6.4. Pathways between CPWS, water quality and health outcomes.......... 48 6.5. Socioeconomic effects of CPWS with respect to health ..................... 52 6.6. Issues for Maori with respect to health................................................ 54 7. Conclusion and recommendations ................................................... 56 7.1. Overall recommendation ..................................................................... 57 7.2. Suggested mitigating actions – water quality ...................................... 58 7.3. Suggested mitigating actions – socioeconomic issues ....................... 60 References............................................................................................ 62 Appendix 1 ................................................................................................ 64 Appendix 2a .............................................................................................. 66 Appendix 2b .............................................................................................. 67 Appendix 2c............................................................................................... 68 3 Executive Summary The Central Plains Water Scheme (CPWS) is a proposed project designed to provide irrigation for 60,000 hectares of land in Canterbury. The scheme would encourage intensification of farming in order to meet increasing world demand for agricultural products. Community and Public Health, of the Canterbury District Health Board, has undertaken this Health Impact Assessment (HIA) to contribute to the consideration of the proposed scheme within the statutory resource consent process. This HIA has considered the evidence for the benefits and risks of the CPWS with respect to population health and wellbeing. The assessment is based on evidence drawn from four workshops with key stakeholders and experts, literature reviews and interviews with experts. In particular, the HIA has considered the potential health implications in terms of water quality and socio-economic issues. The HIA found there are potential adverse health implications associated with the scheme in relation to water quality. Rising groundwater levels associated with the scheme are likely to lead to septic tank failures on the central plains and, as yet, there is not enough evidence to rule out increased nitrate contamination in Canterbury, including of the Christchurch city aquifer. If the scheme went ahead as proposed there would be a small, but notable, risk of infant death at some time in the future from methaemoglobinaemia. As increased groundwater nitrate concentrations take a long time to reverse and are difficult to treat, this represents a considerable risk to the Canterbury community. Appraisal of socioeconomic effects suggested that financial benefits of the scheme would initially be confined to a small proportion of the community, most of whom are not in the most socially deprived sector of society and whose families will therefore receive little, if any, health benefit from the scheme. There is little evidence of any likely “trickle down” effect from the scheme in improving the health of the most deprived of Canterbury’s population. Most of the job vacancies generated by the scheme are likely to be filled by people from outside Canterbury and New Zealand. While these people and their families may experience improved health as a result of their migration, it is unlikely that simply increasing the population of Canterbury will 4 improve the overall health of Cantabrians. Since there is no “rural decline” in Canterbury, there will be no significant benefit in terms of retention of businesses and services in the area. In fact, it is likely that current services, although they have expanded recently, would be stretched. Based on assessment of the scientific literature, expert advice and key stakeholders’ views, the HIA has concluded that the potential risks of the CPWS to the health of Cantabrians as a whole outweigh the probable financial benefits to a few people. It is recommended that resource consent be declined at this stage. A set of potential actions to mitigate the anticipated health concerns is provided in the event that the scheme is granted consent to proceed. 5 1. Introduction This report summarises the process and findings of a health impact assessment (HIA) on the proposed Central Plains Water Scheme (CPWS) in Canterbury. The area in the proposed CPWS is located between the Rakaia and Waimakariri Rivers. The CPWS is a proposal to irrigate up to 60,000 hectares of farmland by building a dam in the Waianiwaniwa Valley near Glentunnel to create a water storage lake. The lake would be filled from the Waimakariri and Rakaia Rivers. The stored water would then be distributed to local landowners for irrigation through canals radiating out from the lake. Due to the size and potential impacts of the proposed scheme, there is considerable public and media interest. Under the New Zealand Public Health and Disability Act (2000), every District Health Board has the responsibility to: “improve, promote and protect the health of people and communities” [s22 (a)] “promote the reduction of adverse social and environmental effects on the health of people and communities” [s23 (1) (h)]. The Canterbury District Health Board (CDHB) partially fulfils this obligation through the participation of its Community and Public Health Division (Environmental Health Team) in the Resource Management Act (RMA) process. Consideration of the proposed Central Plains Water Scheme is within the RMA process. The Community and Public Health Division of the CDHB made a submission opposing the granting of resource consent for the CPWS. This was largely due to concern about insufficient information on the potential health implications of the proposed scheme. In its submission Community and Public Health recommended that an HIA be carried out to address this concern. Community and Public Health considered that an HIA of the CPWS was warranted as: The CPWS would affect a large number of people, and have impacts on many determinants of health and wellbeing. 6 Central Plains Water Ltd recognised that changing land use is a key determinant of the health and wellbeing of communities. The local authorities involved have a strong interest in health and wellbeing, and a willingness to try innovative approaches. This was recently demonstrated by an HIA on the Greater Christchurch Urban Development Strategy. Community and Public Health wanted to strengthen their work across sectors to promote health and wellbeing. The timing was right for informing the CPWS resource consent hearing. In the year following the initial application, CPW Ltd carried out several pieces of work which touched on a number of