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Proposed National Environmental Standard for Sources of Human Drinking-water

Executive Summary

1 Introduction

2 Statement of the Issue

3 What are the options?

4 Proposed Standard for Sources of Human Drinking-water

5 Efficiency and Effectiveness of the NES

Appendix 1: Compliance with Drinking-water Standards

Appendix 2: Outbreaks of Water-borne Disease in New Zealand

Appendix 3: Estimate of Water-borne Disease Burden in New Zealand

Appendix 4: Original Wording of NES as Notified in Discussion Document

Appendix 5: Drinking-water Supplies, by Population

Appendix 6: Case Study Methodology

Appendix 7: Health Benefit Methods

Appendix 8: Section 43 of the Resource Management Act 1991

References

Appendix 7: Health Benefit Methods

The health benefits that can be ascribed to the NES are recognised as extremely difficult to quantify. The reasons for this are outlined in chapter 5. Nevertheless, several different methods were used to attempt to quantify the health benefits of the NES for the purpose of this analysis. Qualitative approaches were also used.

Quantitative health benefits were estimated using the following methods:

• an expert group

• a linear health effect model.

The methodologies used to determine the health benefits are explained in chapter 5. The expert group methodology is set out below.

Expert group

A group of experts - including microbiologists, a water treatment engineer, a biostatistician and an expert in drinking-water management - was convened with the task of determining: “Can a health benefit be quantified for the proposed NES for sources of human drinking-water?”

The group discussed how activities were likely to be affected by the NES, and in a case study situation assessed the likely impact on drinking-water and public health. The expert group was asked:

1. whether it was possible to numerically estimate the health benefit associated with the NES on a national basis for all of New Zealand and, if not

2. whether the health benefit could be quantified for a case study catchment.

The group indicated that it was not possible to quantify health benefits nationally. Therefore the group was provided with a case study example to determine whether health benefits of the NES could be estimated on a local basis.

The group used the Ashburton drinking-water supply and its source catchments [This source was chosen because it included both ground and surface water, and because we had reasonably good information on the consents in both source catchments from the Environment Canterbury (ECan) database. It is somewhat historical because the supply has recently been upgraded to a secure groundwater source, and because the ECan Proposed Natural Resources Regional Plan (NRRP) introduces a number of controls in drinking-water catchments. We addressed the plant as it was prior to its recent upgrade, and used the ECan NRRP as a likely outcome following a review of permitted activities in accordance with the NES.] as its case study. Information was provided to the group on the nature of water sources, drinking-water treatment, land uses, permitted activities and consents in the supply catchment, together with the consulting team’s assessment of the likely outcome of consent applications and permitted activity reviews under the NES.

The expert group reached the conclusion that it is not possible to quantitatively assess the health impacts of the NES, even within a specific catchment, because the nature of the relationships between activities, source water, treatment and health are too uncertain.