REV DATE REVISION DETAILS APPROVED 0 03.02.22 Draft for review Project WAIHI NORTH Title Erosion and Sediment Control Plan Northern Rock Stack – Stage 2 Drawn ZW Checked MP Drawing No. ESCP-NRS-002-01 Sheet No. 4 NOTES 1. All erosion and sediment controls will be installed and maintained in accordance with the Waikato Regional Council Technical Report 2009/02 ‘Erosion and Sediment Control Guidelines for Soil Disturbing Activities’ (TR2009/02). 2. Completed areas to be stabilised in accordance with TR2009/02. 3. All erosion and sediment control measures will be inspected on a daily basis by the site foreman. 4. Site monitoring will be undertaken before and immediately after rain as well as during heavy rainfall events. Any required maintenance or improvements to control measures will be undertaken immediately. SRP-NRS-07 Catchment area: 1.5ha Total volume: 450m3 Dead storage: 135m3 Live storage: 315m3 Refer to specific SRPNRS-07 design details. SRP-NRS-06 Catchment area: 1.5ha Total volume: 450m3 Dead storage: 135m3 Live storage: 315m3 Refer to specific SRPNRS-06 design details. Clean water diversion bund constructed using stripped topsoil to divert uphill clean water around the work area. Construction Methodology – Upper section of permanent uphill clean water diversion - Initially a silt fence will be installed below the footprint of SRP-NRS-06. The SRP will then be constructed at the approximate location shown. - Perimeter bunding (clean water and dirty water diversions) will be constructed (likely topsoil stripped from the footprint of works) and stabilised on the external ‘clean’ side of the bunds to direct runoff to the SRP for treatment. - Earthworks will then commence and progress upslope towards the main gully. - A flow activated pump will be set up to over pump clean stream water downstream of the earthwork’s extent so that the temporary stream diversion pipe can be installed. The temporary pipe will be placed within the base of gully to allow clean water to continue to flow downstream during the earthworks. A dam/bund of clay (height TBC) will be placed just downslope of the temporary culvert inlet and stabilised with geotextile. This will create further headwater depth should the capacity of the pipe be exceeded. - Once the temporary stream diversion is in place, SRP-NRS07 will be constructed on top of the temporary stream diversion. The western external batter of the SRP will be stabilised with geotextile. - Once the SRP is in place the diversions will be constructed and stabilised then earthworks will commence to fill the gully. - The earthworks associated with the magazine storage facility will also be completed at this time. SRP-NRS-07 will be used to capture runoff from this area. Due to the steep slopes above the magazine storage area, it is not likely that uphill clean water diversions will be able to be constructed. - Once constructed, the permanent uphill clean water diversion will be stabilised as per final design details and the haul road will be sheeted with aggregate. - With the upper section of the permanent uphill clean water diversion and perimeter access road completed and stabilised, the temporary stream diversion pipe will be removed and/or blocked and the stream water able to flow through the completed section of permanent uphill clean water diversion. Upper section of the uphill diversion drains and perimeter access road. Earthworks associated with the magazine storage facility (~6,000m2) could be completed during this stage of work to allow for runoff to flow to SRP-NRS-07. KEY Erosion and Sediment Control Clean Water Diversion Dirty Water Diversion Culvert Silt Fence Sediment Retention Pond Stabilised dam/bund constructed to increase headwater depth for culvert. Approximate existing stream alignment.
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