CART CART-01 Revision 0 Page | 1 1 Introduction 1.1 Purpose and Scope This Chemical Analysis and Reactivity Test (CART) Report applies to the earthwork’s operations associated with the construction phase of Oceana Gold (New Zealand) Limited’s Waihi North Project (the Project). The purpose of this report is to determine the effectiveness of chemical coagulants on common soil types identified within the Project area with the overall objective of minimising to the greatest extent practicable the discharge of suspended sediments into waterways during the construction phase of the project. It reports on initial testing undertaken, and the procedure for future testing to be undertaken during the Project. Chemical treatment is now widely used throughout New Zealand to enhance the sediment removal efficiency of sediment retention devices implemented during the earthworks phase of infrastructure and development projects. Chemical treatment is currently absent from the WRC erosion and sediment control guidelines and therefore Auckland Council’s Guideline Document 2016/005 ‘Erosion and Sediment Control Guide for Land Disturbing Activities in the Auckland Region, Incorporating Amendment 1’ has been adopted. Soil samples have been tested with two common cationic coagulants, which neutralise the negatively charged soil particles to improve flocculation and settlement within the sediment control device. The two coagulants are complimentary, with one or other often showing a better response depending on the soils being tested. 1. Poly Aluminium Chloride (PAC). 2. Superfloc (a blend of PAC and PolyDADMAC). These coagulants contain aluminium and therefore pH monitoring must be monitored during testing and application. GD05 states that the following limitations apply to chemical treatment: • pH must be tested as part of the bench testing methodology and should be used as a control baseline. Whatever flocculant is being used must not change that baseline pH beyond +/-1 and must not fall outside of the range of 5.5 – 8.5, as measured from the primary spillway. To align with the conditions of consent the pH range, 6.0 to 9.0 will be adopted as part of this Project. • Treatment should cease when the above pH limits cannot be met. Additionally, a chitosan based flocculant was used in two tests to compare results to PAC and Superfloc. This product, supplied by Vital Chemicals, is pH stable and is composed of biodegradable organic compounds. TSF3 Sample 2 and TSF3 Sample 3 were tested with this product. Results are reported in Section 3. This report presents the initial results of bench test trials undertaken to determine the effectiveness of the two coagulants and flocculant. Clarity, turbidity, and pH measurements were undertaken and recorded for each bench test and the results used to determine the optimum chemical and dose rate for each sample provided. 1.1.1 Chemical Treatment Management System The relationship of this CART report within the overall chemical treatment management system for the Project is shown in Figure 1 below. The CART has informed the development of the Chemical Treatment Management Plan (CTMP) developed for the Project. The CTMP is the overarching plan for the
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