97 11 Until final lining is complete, the Consent Holder shall ensure that the pH of a slurry of one part solid (less than 4 mm size fraction) to two parts deionised water, of the surface of exposed PAF rock (after liming) remains greater than or equal to pH 5.5. Unless Waikato Regional Council agrees to an alternative sampling programme in writing, samples shall be (subject to health and safety requirements) collected on a grid pattern of not more than 50 m and, where practical, within 1 week of placement of the PAF rock and then at intervals not exceeding 4 weeks. This test is designed to help determine the potential for acid generation and sulphate release from waste rock. The procedure for collecting and analysing the samples shall be as described in the GOPTSF Monitoring and Management Plan. 12 The Consent Holder shall, unless otherwise authorised in writing by Waikato Regional Council, collect all underdrainage flow from the tailings storage facility and divert it to the Water Treatment Plant for treatment or for use in the process plant. 13 A minimum freeboard of 4m shall be maintained between the pit crest and all material in the tailings pond (i.e. solid and liquid). This level shall be sufficient to impound the surface run-off arising from the Probable Maximum Precipitation (PMP) event without overtopping, plus 1.0 m. Following rainfall or any event that reduces the freeboard below the minimum requirement, the water level shall be drawn down as soon as practicable to restore the full freeboard. 14 The Consent Holder shall supply at least the following documentation to the Waikato Regional Council and Peer Review Panel prior to commencement of the GOPTSF construction works: a. Detailed Design Report b. Construction Drawings c. Specification All subsequent amendments to the design shall be supplied to the Waikato Regional Council prior to implementation and following Peer Review. 15 The Consent Holder shall retain a person or persons with recognised documented experience in the design of tailings storage facilities (the Designer). All aspects of the design of this facility shall be undertaken under the supervision of the Designer, who shall provide to Waikato Regional Council in conjunction with the documentation required by Condition 14, written confirmation that all aspects of this structure have been suitably investigated and properly and safely designed in accordance with currently accepted engineering practise, and designed to a standard adequate for the effective control of acid rock drainage and the containment of tailings.
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