June 2022 G-01483.84-017-R-Rev0 Because the 44 guidelines (WRC 2020a, pg 106. Table 7-1) site diversion channel materials are anticipated in stiff clay (1.14 m/s) but may range from volcanic ash to weathered volcanic rock. Figure 16 indicates where the typical channel lining options presented in Table 20 would apply. Detail design is required at the next study level to optimize channel design dimensions and incorporate detail around the specific erosion control measures for each segment (lining specifications, check dams, stilling basins, and drop structures). (Appendix E) provides typical erosion control solutions as referenced on Figure 16 and noted on WRS stage plan sections (Appendix C). A natural incised gully after culvert 4 may need additional rip rap protection to carry increased flows or an alternate route formed along the existing access track and discharged into the main gully. Table 20: Typical trapezoidal channel dimensions and lining. Channel reference Max design flows Max velocity (lining) Gradient range Base width Side slope Depth (D) Lining type W-Steep 0.5 m³/s 1.5 m/s >5%<18% 0.5m2.5m 1:1.5 0.7m Rock lining SW- Flat 0.07 m³/s 0.5 m/s <5% 0.5m 1:1 0.6m Rock lining CW-Steep 1.9 m³/s 7.6m/s1/6.1m/s2/4.6m/s3 >5%<25% 1.0m 1:2 0.5 m TRM CW- Flat 1.8 m³/s 1.14m/s <5% 1.0m 1:2 0.8 m Grass lined 1 – Fully Vegetated: 70% to 100% density19. 2 – Partially Vegetated: 30% to 70% density. 3 – Unvegetated: 0% to 30% density. WRS haulage and access roads include bunds along edges and have carriage ways graded at 2% (to inside) (Figure 15), the roads provide additional contingency for stormwater overflows in larger than the 1:10 AEP storm events. The WRS haulroad, WUG portal access road and lower track running to the TSP are designed with downhill gradients to the WCP. Given that the WRS is active haulage site some repair and maintenance is expected along the main haul road and access following storm events while the WRS is under construction. Suitable maintenance equipment is expected available on site. Figure 15: Sketch of typical Haul Road cross section including SW side drainage channel.
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