OPW20.0191 NC IR response

NC Information Required for Item 2

Provide an updated Erosion and Sediment Control Plan, prepared by a CPESC or
RPEQ, which includes information on, but not limited to:
           2.1. Indicating the design event for the updated E&SCP;
           2.2. A clean water diversion design, or alternatively, demonstrate that
           the
           structures/measures are sufficient to cater for the total catchment
           (including water coming from neighbouring properties);
           2.3. Staging of the works and how each stage will be stabilised
           immediately after being completed;
           2.4. For each of the proposed stages, demonstrate how the proposed
           controls will prevent the runoff of sediment into the surrounding
           waterways;
           2.5. How areas that will not require earthworks in the imminent cut to fill
           operation will be stabilised;
           2.6. Maintenance regime of the proposed controls;
           2.7. Where the topsoil will be stockpiled and how it will be stabilised.

Engineering Response to Item 2

2.1
The proposed Erosion and Sediment Control Plans includes two Type D sediment
dams. The design event for these Type D dams is the 5 Day, 85th percentile, 1 year
ARI event (63.2% AEP). 85th percentile was chosen as the site discharges to a
sensitive area and the 1 year ARI event was chosen as the site has been classified
as a short term disturbance. The volume of storage required for this event is
approximately 700m3. The sediment dams (including the drainage channel) provide
approximately 1000m3 of storage.

2.2
The Erosion and Sediment Control Plans have been updated to ensure that the
upstream flows are directed along established areas to Kinmond Creek. To achieve
this the culvert under the main access has been blocked until the central drain on
site is effectively stabilised. The overland flow path for upstream catchments will flow
to the embankment of the main access before travelling north towards Kinmond
Creek. Figure 1 demonstrates that the location that the stormwater will flow is
effectively stabilised. The Stormwater will flow into a culvert that directs the
stormwater to Kinmond Creek. Figures 2 and 3 show the outlet of this culvert and
the channel to Kinmond Creek.




                                                                            Page 3 of 14