112 Our assessment compares the merits of retaining the existing USEPA (1986) standards as detailed above, against the application of more contemporary standards. This will assist in determining whether the presently permitted receiving water quality standards30 remain appropriate and effective at properly mitigating the ecological effects of the discharge. 20.1.2 Ecological Values A fundamental question in the application of water quality standards is what ecological values are to be protected or safeguarded. In section 13 we outlined the past and present water quality and ecological values of the Ohinemuri River. The information available shows that the ecosystem attributes and the ecological values of the Ohinemuri River have not varied since the application of the USEPA (1986) receiving water criteria. 20.1.3 Comparison of Values We have provided a comparison of the receiving water quality standards set in the existing resource consents with the ANZG (2018) guidelines, at various levels of ecosystem protection (Appendix 10). For the purposes of the application, we have applied the 95% level of ecosystem protection, despite the ecological values varying in condition, and indicators suggest that the condition of the Ohinemuri River is in fact poor-fair. It will be apparent that the existing receiving water standards are, for most parameters, higher than the ANZG DGVs. This is to be expected as the DGVs act as ‘trigger’ levels, requiring further investigation if exceedances occur, as compared to actual standards derived specifically for the biotic communities of the Ohinemuri River. A number of DGV trigger levels (selenium, mercury, lead) are higher than those provided for by the resource consents. We also note that, for most of the parameters (as associated with the receiving water quality standards) there is no change in the DGVs from the trigger levels provided by the ANZECC (2000) guidelines. 20.1.4 Water Quality of the Ohinemuri River Figure 28 and Figure 29, below, show the water quality of the Ohinemuri River at each sampling site for the period 2008-2021, and on each is plotted the resource consent standard, and the ANZG (2018) trigger DGV. These graphs are helpful in understanding how the water quality of the Ohinemuri River compares with both the existing consented standard, and when compared to the ANZG (2018) trigger DGVs. It is evident, that for the most part, the summary of the water quality of the Ohinemuri River, over the sampling period, shows that the median values of the parameters met the consent requirements. Similarly, with the exception of silver, median values of all remaining parameters meet the ANZG (2018) trigger DGVs. We note that the DGV value for silver is below the detection limit, effectively making compliance with the DGV impossible. 30 As set out in resource consents XXXX
RkJQdWJsaXNoZXIy MjE2NDg3