OPW20.0191 NC IR response

and are sufficiently sized to capture the 5 Day, 85th percentile, 1-year ARI event.
These dams are proposed to be de-watered prior to expected rainfall events.

There is a portion of exposed earth in the northern portion of the proposed works
that is approximately 1000m2 that will drain towards Kinmond Creek and a portion of
exposed earth in the southern section of proposed works that is also approximately
600m2 that will drain towards the existing table drain adjacent to Kinmond Creek Rd.
These sections will have a sediment fence installed to capture any sediment runoff.

As part of Stage 2 it is proposed that 1200m2 of earth be reshaped. This portion of
works drain to the existing table drain adjacent to Kinmond Creek Rd. It is proposed
that work in Stage 2 will occur incrementally with exposed areas topsoiled and lightly
compacted immediately after the ground has been reshaped. All areas of exposed
earth are to have sediment fences installed around the exposed areas.

As part of Stage 3, it is proposed to install a new culvert under the secondary
access. This work also involves re-directing the existing table drain for a small
portion. It is proposed that the exposed area of table drain will be turfed immediately
after being shaped to provide protection to the table drain.

As part of Stage 4 it is proposed to install a new pipe from the main sediment dam to
Kinmond Creek. This drainage line will ensure that once works are completed that
the water level will quickly return to the height of the invert of the drainage line to the
main dam. This will ensure that the main drainage line can maintain enough
vegetation to remain effectively stabilised indefinitely.

The area of exposed earth will be limited to the trench area above the new pipe. It is
proposed that a sediment fence be installed around the exposed areas until they are
effectively stabilised with vegetation.

It is proposed that the new drainage line will outlet immediately east of the existing
culvert at the invert of Kinmond Creek. The outlet design will include a concrete
apron that includes a 150mm high upstand. This 150mm high upstand will allow the
concrete apron to act as a plunge pool and reduce water velocities as they flow into
Kinmond Creek. The reduced velocities will ensure that the outlet will not cause
erosion on the Kidmond Creek channel or its banks.

2.5
The existing areas that will not require earthworks are not expected to be disturbed
further and currently have sufficient ground cover to be classified as effectively
stabilised. If small areas are disturbed as part of the construction, a sediment fence
is proposed to be installed around these areas until they are stabilised. These areas
can be identified as part of the regular inspections and have not been shown on the
updated plans.

2.6
It is proposed that all Erosion and Sediment Control devices are inspected:
      • Daily when works are occurring on site
      • Weekly when works are not occurring on site
      • Within 24 hours of expected rainfall


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