Project Hurunui Wind Construction and Project Overview

Project Hurunui Wind Construction Effects and Management Report
that platform areas around the basecourse hardstand areas are backfilled with top soil with
a slight cross fall, and regrassed to avoid erosion.
Drainage provision may be provided to the foundation excavation by way of a trench or filter
drain with suitable stabilised outlet.
Fill sites and lay down areas
The proposed treatment for fill sites is discussed in Section 2.4. Finished ground profiles
will be shaped to ensure that natural drainage paths are maintained. On completion of
construction, these sites will be re-topsoiled (with material which has been removed and
stockpiled) and re-vegetated as appropriate with runoff direct onto grassed land on
surrounding catchments.
Lay down areas will have a general crossfall, allowing stormwater run off in the direction of
the general slope of the land. Sedimentation and erosion control measures as described in
Section 3.3.1 above will be applied. On completion of construction, lay down areas will be
rehabilitated in the same manner as fill sites.
3.3.3 New Culverts at Stream or Gully Crossings in the Core Site
No stream crossings have been identified within the core site however there are locations
where upper gully crossings and existing open channel drain crossings will require culverts.
Table 15 below summarises the proposed culverts identified along core site access roads.
Culvert sizes have been based on flows for flood return periods of 20 years with provision
for secondary flow paths across purposely lowered sections of the access road (for
overtopping for longer return periods).
We envisage no gully crossings in addition to those tabulated given the layout of the access
roads are generally close to or on ridge tops where the terrain is relatively gentle. However,
where new culverts are required per the detailed design (consequent to adjusting the
turbine platforms and access roads within a 100m radius placement area), culverts will be
sized as described above.
The approximate height of the embankment at the culvert inlet of the majority of all culverts
is less than 1m apart from one culvert on Road D which has an embankment height of
approximately 1.5m at the culvert inlet. Given the embankment heights at culvert inlets are
not significant no locations have been identified where an embankment fill could essentially
form a ‘dam’ across upper valleys. However, if a significant embankment fill arises
consequent to adjusting the turbine platforms and access roads (within a 100m radius
placement area) the culvert will be sized on flows for flood return periods of 100 years to
address the effects of ‘heading up’ associated with culverts with significant embankment
fills.
Based on this design criteria, the required culvert sizes are indicated in the following table.
The final size of the culvert, where required, will be determined during the detailed design
stage. This table also identifies a range of characteristics associated with each culvert.
5C-1604.02
February 2011 44