ESCP-001-01 ESCP-002-01 ESCP-003-01 ESCP-003-02 ESCP-003-03 ESCP-004-01 ESCP-004-02 ESCP-004-03 3.1. Clean Water Diversions Upper catchment clean water will be diverted where possible and practical using clean water diversions, at the approximate locations depicted on the drawings. TR2009/02 recommends that clean water diversions are designed to carry the flow from the 20% annual exceedance probability (AEP) rain event (plus 300mm freeboard). Where possible the clean water diversions have been increased in size to convey the 5% AEP storm event, including a freeboard of 300mm. Table 3 provides the clean water diversion sizing details. Clean water diversion design details have also been provided by BECA and Golder, where requirements vary between the ESC designs, the more stringent will be adopted from the outset. Table 2: Clean water diversion input parameters. Parameter Input Rainfall depth (24hr 5% AEP) 290mm Freeboard 300mm Base width 0.5m (unless otherwise specified) Stabilisation type (TBC on site) Grass, rock lined, geotextile All clean water diversions shall discharge to stable flow paths beyond each works site. Table 3: Clean water diversion sizing details for Willows Road. Clean Water Diversions Site reference Catchment area (maximum) Peak flow (m3/s) Diversion slope (minimum) Channel capacity (m3/s) Design Flow Depth (including 300mm freeboard) CWD - SFA 1ha 0.452 2% 0.85 500 Mine Access Road CWD 2ha 0.904 2% 0.92 550 CWD channel - Willows Rock Stack (Year 1 – maximum area) 6ha 2.71 5% 3.01 700 WRS CWD North 2ha 0.904 2% 0.92 550 WRS CWD South 1.25ha 0.565 2% 0.92 550
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