EGL Ref: 9215 23 June 2022 Page 20 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. FIGURE 13: STORAGE 2 TAILINGS DENSITIES WITH TIME 4.2.6. Tailings profile within the impoundments The profile of the tailings in Storage 2 was investigated as part of the approval for the Storage 2 raise to RL160.7. The tailings profile was found to generally comprise of cohesive low plasticity material (sandy silt, clayey silt) with occasional thin lenses of cohesionless (non-plastic) silt/sand material. Lenses rather than layers of sand were inferred from comparison of Cone Penetration Tests (CPTs) located on the same section. Samples of the typical cohesive tailings and cohesionless lenses were obtained for testing. The typical particle size distribution (PSD) and plasticity index (PI) values are shown in Table 2. Most of the tailings are a moderately plastic clayey silt. The sandier lenses are a mixture of silt and sand with a minor amount of clay particles. TABLE 3: PSD AND PI OF TAILINGS IN STORAGE 2 Tailings Particle Size Distribution (PSD) Average (Range) Plasticity Index (PI) Average (Range) Clay (%) Silt (%) Sand (%) Clayey SILT (moderately plastic cohesive) 18 (13-33) 58 (45-73) 24 (4-42) 15 (11-22) SAND/SILT (cohesionless) 9 (8-10) 48 (31-53) 43 (39-59) Nonplastic
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