Chatham Rock Phosphate Marine Consent Application. P Kennedy Environmental Chemistry and Water Quality Evidence Summary

Transcription

1 Chatham Rock Phosphate Marine Consent Application P Kennedy Environmental Chemistry and Water Quality Evidence Summary

2 The key matters covered in my evidence and in the toxicology and water quality expert caucus group Sediment quality Elutriate testing Toxicity testing Multiple stressors Biouptake of trace elements Uranium toxicity ANZECC guidelines October 15,

3 Sediment quality Sediments comprise muddy glauconitic sand over chalk these constitute the key sediment types on the Chatham Rise Chemical analysis of sediment has shown that there is little to note in the chemistry concentrations are natural (i.e., background) and display little unusual geochemistry. Phosphorite nodules do have some interesting chemical difference to chalk and sediment due to their development over millions of years. The key difference between nodules and the other sediments is principally the higher concentration of most trace elements, including uranium. Nodules are not returned to the seafloor. Ongoing samples of sediment will be collected and characterised as part of the Monitoring Plan that forms part of the EMMP. October 15,

4 Elutriate quality Elutriate testing is used to assess the effects of the release of sediment into seawater. In this case, the elutriate is considered (in my view) to be representative of the shaking that occurs as sediment is processed. As expected, trace elements are released (along with other common constituents). Elutriates were prepared on surface, subsurface and chalk sediments and also the phosphorite nodules. Very few differences were seen between materials tested. The caucus statement recommended that further elutriate data be obtained using fresh sediments this is proposed by CRP in the EMMP Monitoring Plan. The caucus statement recommended that the quality of the discharge be monitored. CRP propose that this would occur on board the vessel but within the sinker pipe system. Specific details are included in the EMMP Monitoring Plan. October 15,

5 Toxicity testing Toxicity testing was carried out for three standard species to gauge potential toxicity. The caucus group discussed its concern about the use of those species rather than using site specific species. The toxicity testing used frozen sediments. It was agreed by the caucus group that there was value in repeating the toxicity testing using fresh sediment. This is now proposed and is included in the EMMP Monitoring Plan. The toxicity testing on the species used showed little toxicity indicating little dilution was required to ensure no toxicity in the plume. The results of the toxicity testing compared well with the expected requirements based on comparison with the ANZECC (2000) guidelines. The toxicity work carried out showed that uranium concentrations likely to be present in the discharge are not likely to be toxic. This reflects the agreed caucus statement conclusion for issue 6 that uranium is likely to have low toxicity. October 15,

6 Multiple stressors The caucus statement identified that multiple stressors were an issue but were given a Low rank It is agreed that organisms are exposed to stressors such as contaminants, suspended solids, reduced dissolved oxygen at the same time. The toxicity testing provided an indication of exposure to multiple contaminants but not all stressors. Dissolved oxygen reductions within the plume are expected but are likely to be localised within the core of the plume Effects of multiple stressors will be limited in space and time. Mining events are of four day duration followed by six days of no-mining. October 15,

7 Biouptake Biouptake does occur in the marine environment for many elements but biomagnification does not (mercury is one of the few elements that does). Non-essential elements are typically discriminated against with low trophic transfer rates (uranium falls into this group) No baseline assessment of trace elements in fish has been carried out. The caucus statement identified under Issue 5 that monitoring of trace elements in fish should occur. CRP is now proposing that monitoring of trace elements and radionuclides in key commercial fish be carried out. This will occur prior to mining to develop a baseline and will continue following the start of mining. This will be set out in the Monitoring Plan that forms part of the EMMP. October 15,

8 Uranium toxicity The caucus group identified uncertainty about toxicity of uranium in seawater There is a significant difference in the toxicity in freshwater (low ph) versus marine environments (carbonate conditions with higher ph). This difference is due to the chemistry of the environments. The group concluded that in seawater the toxicity of uranium is likely to be low. The freshwater/marine toxicity differences can be seen comparing the ANZECC (2000) 95 % trigger value of 0.5 mg/m 3 for freshwater environments with the natural concentration in seawater of 3.3 mg/m 3. However, if one accepted the CCME (2011) freshwater long term exposure guideline of 15 mg/m 3, following 10 fold dilution, concentrations in the discharge will be lower than that guideline. The available near-field dilution is assessed as 750 times. October 15,

9 ANZECC guidelines Issue 7 of the caucus statement concerned the application of the ANZECC (2000) guidelines. The concern related to the common mis-use of the trigger values by regulators. The trigger values are not end-of-pipe standards and as such identifying the trigger values as standards to be met prior to discharge is not appropriate and was not what the trigger values were developed for. The trigger values (e.g., 90, 95 and 99 % protection) define the first stage of a hierarchical assessment system. October 15,