Aurecon New Zealand Limited
Level 6 KPMG Centre
85 Alexandra Street
Hamilton 3240
PO Box 487
Hamilton 3240
New Zealand
T
F
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+64 7 834 1565
+64 7 834 3527
[email protected]
aurecongroup.com
13 November 2015
Jeremy Miller
Project Manager
Nova Energy
Level 15 95 Customhouse Quay
Wellington
Dear Jeremy
RE:
1
Proposed Nova Energy Waikato 300 MW Power Plant - Preliminary Geotechnical
Appraisal Report
Project background
Aurecon have been engaged by Nova Energy (the Client) to provide geotechnical consultancy
services to support preliminary planning and concept design for the proposed 300 MW Waikato Power
Plant, located approximately 500m to the west of Kawhia Road, SH39, Otorohanga (the ‘site’).
The purpose of this report is to provide a ‘high level’ site-wide preliminary geotechnical appraisal to
support master planning and conceptual design of options for the proposed development. The key
elements assessed by the preliminary geotechnical appraisal include:



The power plant building location
Access Roads A & B
220kV overhead transmission line
In order to prepare this report a desktop study and site inspection was undertaken to collate available
and relevant information to identify and provide preliminary discussion concerning geotechnical
hazards at the site which may impact the design and construction of the proposed development.
Detailed geotechnical investigation and assessment will be required to support future design and
construction.
2
Site setting
2.1
Site location and access
The proposed development site is located within a single legal property boundary, legally defined as
Section 75 B:L XVI Pirongia SD and owned by NEL Farms Ltd. The site is addressed 869 Kawhia
Road, RD3, Te Raumoa, State Highway 39 (SH39). The land parcel covers a total area of 153
hectares, of which the proposed power plant will cover an area of 2 to 3 hectares. The power plant site
is currently accessed from the south-east along farm tracks extending from Kawhia Road. The site is
currently zoned as rural, under the Otorohanga District Plan.
The power plant footprint is located approximately 500 m to the west of SH39 within the centre of the
property. From the building footprint, proposed Access A extends back along the existing farm access
track south-east towards SH39. Proposed Access B extends from the building footprint north along
existing tracks and through paddocks towards SH39 in the northern corner of the property. The
proposed transmission line route extends roughly south-west from the power plant building footprint
towards existing transmission line which is located in the southwest corner of the site.
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 1
2.2
Geological setting
A review of the Institute of Geological and Nuclear Sciences (IGNS) geological map 1:250,000 for
Rotorua, Sheet 5 (Healy et al, 1964) indicates that three main geological units are mapped within the
property boundary, as shown on Figure 1 attached.
The Aotea Formation, primarily a sandstone unit with siltstone, limestone and greenstone sub-units is
mapped in the western part of the site and corresponds with raised topography to the west of the main
building footprint. This unit is described as ‘massive or banded, calcareous muddy sandstone and
sandy calcareous siltstone, commonly glauconitic, basal, flaggy or cross bedded’. The unit is
Oligocene-aged (~28.5 Ma) and mapped as part of the large Te Kuiti Group of sedimentary rocks. The
southwest most part of the transmission line is shown to be underlain by Aotea Formation.
The Ongatiti Formation, a Pleistocene-aged (~1.8 Ma) ignimbrite unit, is mapped within the central
and eastern parts of the property. The ignimbrite is described as ‘compound, moderately to strongly
welded, vitriophyric pumice and crystal rich ignimbrite with abundant lithics’. The majority of Access
Road A and the proposed transmission line are situated within areas of the site mapped to be
underlain by Ongatiti Formation.
The northern corner of the site, in the vicinity of site streams, is mapped as Piako Subgroup. This
formation is described as alluvial and colluvial deposits of silt, sand, gravel and pumice. These
materials are described as ‘locally derived pumiceous clays, sandy clays and gravels’. The majority of
the Power Plant and Access Road B are situated within areas of the site mapped to be underlain by
Piako Subgroup alluvium.
Although not mapped, the geological units described above are is anticipated to be overlain by a
capping layer (typically a few metres thick) of volcanic ash originating from the Taupo Volcanic Zone.
The beds of local streams are also expected to be underlain by recent alluvial deposits associated
with migration of stream channels.
2.3
Geomorphological setting
The site is located within a small valley on the boundary between two key geomorphological settings,
the West Waikato Hills and Ranges to the east and the Waipa Basin to the west, as described by
Edbrooke (2005). The Waipa Basin is described as a wide valley system formed by the Mangapu
River, Waipa River and Mangaokewa Stream (and respective tributaries). The northern part of the
basin is dominated by low rolling hills formed by volcaniclastic rich alluvium with locally higher hills
formed over weathered basement greywacke (such as Aotea Formation). Wide alluvial valleys
separate the hills.
The West Waikato Hills and Ranges is described as an area of dissected hills and ranges extending
inland from the coast towards the Waipa Basin. In the area of the site, the dissected hills are formed
over siltstone and sandstones of the Te Kuiti Group (Aotea Formation). The hills have a stepped
profile of alternating steep and gentle slope escarpments. Numerous block falls are apparent along
steeper slopes and active earth flows are common. Sinkholes and karst landscapes are common in
areas underlain by limestone, although this is not anticipated to be an issue for the power plant site.
2.4
Hydrogeological setting
The site area comprises a large valley setting with a number of small streams, creeks and tributaries
flowing north. This network of streams drain to the Waipa River which lies approximately 1.4 km to the
north of the power plant building footprint. Of these streams, the Ongaruhe Stream flows along the
eastern periphery of the power plant, with a smaller tributary stream flowing through the centre of the
building footprint.
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 2
No groundwater bore information is currently available. It is expected that the groundwater will be
relatively shallow below the valley floor, which sits at an elevation of ~32 m RL. It is expected that
surface run-off will percolate quickly through free draining site soils and flow towards streams and
creeks at the base of gullies. In addition to natural water courses, a series of drainage channels and
ditches have been constructed within the valley floor in the vicinity of the proposed power plant.
2.5
Active fault database
A review of the GNS online active fault database on 10 November 2015 indicates the nearest active
fault to be in exceedance of 80 km to the south-east and east of site.
2.6
Regional hazard mapping
The site is located within an area defined as a ‘Not Very Hazardous’ to ‘quite hazardous’ earthquake
zone by the Waikato Regional Council. ‘Not Very Hazardous’ classification is defined by the WRC as
being underlain by materials formed between 75 and 2.5 millions years ago and which include
sandstone, siltstone, mudstone, coal measures, limestone and conglomerate. These materials are
defined as being weak to moderately strong, containing volcanic rocks of various ages. Gravel
materials are usually dense to very dense. Fine-grained rocks are prone to slumping and land sliding,
especially if saturated or without vegetation.
The ‘Quite Hazardous’ classification is defined as materials formed less than 2.5 million years ago and
are made up of ricer and marine terrace deposits, lignite, dune sand, pumice, alluvium and ignimbrite
flows. These include unsaturated, slightly weathered, loose gravel ash and sand.
Areas of natural valley and lower elevation (which include the Power Plant and Access B) are
identified by Waikato Regional Council as being within zones of likely flood hazard. It is noted that the
mapping prepared by WRC does not represent a design flood event.
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Figure 1
Waikato Regional Council Earthquake Hazard Map (source:
http://www.waikatoregion.govt.nz/PageFiles/2529/earthquake.pdf)
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2.7
Site inspection
Aurecon’s Senior Engineering Geologist undertook a site inspection on Tuesday 3 November 2015.
The purpose of the investigation was to inspect the current status of the site, and identify any key
geotechnical constraints that will need to be addressed and/or managed through the design and
construction process.
The inspection focussed on the four key features of the power plant concept design. As such, other
parts of the property (including the proposed gas supply route shown on Drawing L001) have not been
inspected in as much detail and may need to be revisited in the event specific structures or services
are relocated.
A summary of the key observations made during the inspection is presented in Table 1. The location
references for each key feature are shown on Figure 1, attached. Site photographs relevant to the
inspection are also attached at the end of this document.
Table 1
Key site observations
Location
Ref.
Photo
Ref.
Location
Comment
1
1&2
Access A
Entrance to site through paddock raised approximately 1.5 m above Kawhia
Road. Gentle slope to north-west across paddock to existing farm track. No
structures present, other than water tanks and a corrugated tin shed. A
small grassed drainage channel (less than 500 mm deep) runs through the
centre of the paddock along the rough alignment of Access A. Some
exposed ash soils within paddock comprising stiff sandy silt. A cut would
need to be formed to tie in access track to main road.
2
3-5
Access A
Access A alignment runs along crest of sloping ground located at head of
large gully. Slope approximately 15 to 20 m high and moderate to steep
gradient (~°45). Small shallow failures noted to be present at top and base
of slope exposing ash soil within fresh scarp surface. A small slip scarp was
observed at top of gully head which was circular in shape and measured 2
m across and 400 mm high. Scarp at base of slope appears to be erosional.
A small spring was observed at base of slope with swampy vegetation and
organic silt/clay infilling the gully floor.
3
6
Access A
Pond formed by earth embankment in base of gully with small culvert
draining to stream.
4
7&8
Access A
Access A follows alignment of existing farm track in this locality Track
formed in cut located two thirds up the way of moderate north-facing slope.
Slope ranges in height between 10 m and 20 m. Cut surface above track
approximately 70°, exposing cream and pale brown sandy silt ash soils.
Some minor instability caused by weathering and erosion in face, which is
not vegetated. Slope above cut less than 30° with no instability observed.
Below the track the slope steepens to between approximately 40° and 45°.
Slopes below the track show some minor instability and erosion (stream
located directly at toe of slope).
5
9
Power
Plant
Power Plant building platform located in the base of an alluvial valley (Piako
Subgroup) approximately 350 m wide. The northern end of the platform
comprises level ground, but with natural undulations and hummocky
surface. The site area is currently in pasture with no building structures. No
soil exposures were observed.
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 5
Location
Ref.
Photo
Ref.
Location
Comment
6
10 &
11
Power
Plant
Southern end of the power plant building platform is located over a plunging
ridgeline (Ongatiti Formation) elevated approximately 5 to 10 m above the
valley floor. The ridgeline trends south to north and drops into the valley
floor at a gradient of ~<10°. Gentle to moderate slopes to east and west
from crest of ridge with no observed evidence of instability.
7
12
Power
Plant
The Ongaruhe Stream runs along the eastern boundary of the Power Plant
building platform. At this location the channel is approximately 1 m to 2 m
wide and 3 m deep and at the time of inspection running with approximately
1 m of water. Some minor erosion instability is observed at the edge of the
channel. Channel is unlined and appears to follow a natural alignment.
8
13
Power
Plant
Stream channel located through the western side of the building platform.
Channel is 1 to 2 m wide. Channel approximately 1 m deep and half full.
Channel unlined but has been straightened for drainage purposes.
9
14 &
15
Access B
From the power plant, Access B follows the existing farm track north for
approximately 300 m. The track follows the eastern edge of the valley floor
at the toe of gentle to moderately sloping ground. At location 9, the track is
formed within a small cut into a west facing slope with a gradient of ~25°. No
evidence of instability observed.
10
16
Access B
Culvert beneath existing farm track for small drainage channel.
11
17
Access B
At the closest point to Access B, the Ongaruhe Stream flows through a
natural cut approximately 3 m high and with a gradient towards the channel
of approximately 40° to 60°. At the base of the cut, the channel is
approximately 3 to 4 m wide and approximately 1 m deep.
12
18
Access B
The northern end of the Access B deviates from the existing farm track and
passes through paddock towards an entry point to be formed in the northern
corner of the property. The alignment rises up a gentle slope at a gradient of
approximately 10°.
13
19
Access B
Where Access B meets the State Highway the elevation matches that of the
valley floor. Between Locations 10 and 12 there is a small shallow plunging
ridgeline through the alignment that could be avoided by re-routing the
access way approximately 20 m to the north.
14
20
Proposed
220 kV
line route
The proposed route of overhead wires follows a small gully to the south of
the power plant footprint for approximately 450 m. Through the base of the
valley the gradient to the south is gentle, with level to gently sloping
topography to the east of the line route, and moderately sloping topography
to the west of the line route. Further upgradient to the west, the slopes
steepen sharply and show evidence of instability.
15
N/A
Proposed
220 kV
line route
Due to recent rain and steep topography this area could not be accessed
directly, however from this point the line route moves to the south-west and
traverses steep south-east facing sloping ground with evidence of instability
visible in aerial photography.
2.8
Previous and current investigations
To our knowledge there has been no site specific geotechnical investigations undertaken at the site.
Aurecon are in the process of undertaking ground investigation to support a large industrial
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 6
development located at the corner of Kawhia Road and Waitomo Valley Road, approximately 10 km to
the south of the site. Although the location of the investigation is of reasonable distance from the
current site, the site is located within a similar geological and geomorphological setting; within a low
lying valley floor setting at the edge of the Waipa River catchment. A geotechnical assessment report
is yet to be published by Aurecon, however the following information has been obtained which is of
relevance to this site:

MASW geophysics undertaken at the Kawhia Rd site confirmed a Subsoil Class C setting in
accordance with NZS1170.5. The geophysics also identifies the presence of buried palaeochannels within the Piako Subgroup which may result in locally deep soft sediment or greater depth
to bedrock.

Investigations undertaken to date confirm the presence of shallow topsoil and recent volcanic
tephras overlying a thick sequence of Quaternary-aged alluvium, comprising primarily cohesive (silt)
material with occasional horizons of sand and organic material.

The results of in-situ testing show an SPT N values of 0 to 10 within alluvial sequence improving to
30 – 50 in within weathered bedrock (estimated to be present below the site at approximately 20 m
bgl).

The alluvial sequence was found to comprise soft and loose soils which are likely to be susceptible
to settlement, low bearing capacity, and liquefaction risks.
3
Engineering considerations
3.1
Introduction
The desktop information indicates the site is underlain by two main geological units which are likely to
govern the geotechnical aspects of the development. The Power Plant and Access Road B is likely to
be underlain by a sequence of quaternary sediments overlying bedrock at depth. Access Road A and
the overhead transmission line is largely underlain by Ongatiti Formation. All of the areas are expected
to be underlain by a capping layer of topsoil and ash of variable thickness. Key geotechnical
engineering considerations for development include the following:






Variability in ground conditions and soil flexibility (subsoil class)
Foundation conditions – bearing capacity and settlement risk
Seismic considerations including liquefaction and lateral spread risk
Slope stability risk
Earthworks and reuse of site soils
Environmental risk
Each of the above the constraints are discussed in more detail in the following subsections. These
considerations are subject to change based on the findings of any future geotechnical or
environmental investigations.
3.2
Preliminary ground model
Based on the mapped geology and the geophysical information obtained as part of the current scope,
it is considered likely that the subsurface ground profile within the Power Plant and Access Road B will
comprise a sequence of topsoil and volcanic tephras overlying alluvial material comprising sand, silt
and gravel. The alluvial sequence will be underlain by the published mapped geological units (being
either ignimbrite or sandstone). The alluvial layers may be separated by horizons of soft lacustrine silt
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 7
and clay and localised peat deposits. Access Road A is expected to be underlain by Ash mantling
Ongatiti ignimbrite. The transmission line is expected to be largely underlain by Ash mantling Ongatiti
Formation, with the possibility of Aotea Formation outcropping at the southwest end of the proposed
alignment.
Based on recorded groundwater levels, topographic information and proximity to surface water bodies
it is anticipated that a permanent groundwater table will be less than 5 m below the ground surface
level within the area of the Power Plant and Access B. It may be possible that a shallow or perched
water horizon exist as a result of surface run off from the adjacent hills.
There is currently no evidence of fill material within surface, or near surface soils, however this cannot
be ruled out. Any non-engineered fill is likely to be unsuitable for earthworks or bearing shallow
foundations without investigation of its properties, or information regarding fill compliance testing
becomes available.
3.3
Site classification
Based on the mapped geology it is considered likely that the area of the Power Plant building footprint
will meet the requirements of a Class C or D site in accordance with NZS1170.5:2011 Earthquake
design actions. This will need to be confirmed by geophysical or geotechnical ground investigations.
The transmission line is expected to be Class C but potentially may be Class B where shallow rock is
identified during investigations.
3.4
Foundations
3.4.1 Power Plant
There is potential for soft or organic soils to be present within alluvium near the surface within the area
of the power plant building footprint and along Access Route B. These soils may be susceptible to
consolidation settlement beneath shallow foundations supporting high building loads and where earth
fill embankments are proposed. Where significant cuts are undertaken to form building platforms, the
risk of settlement may be reduced through load compensation.
The presence and extent of soft soils shall be investigated by geotechnical investigation with analyses
undertaken based on final landform design and expected building loads and embankment heights.
The risk of consolidation settlement may be reduced or mitigated through one or a combination of the
following:




Undercut and replacement (where practicable to remove shallow compressible soils near surface)
Ground improvement (stone columns, deep soil mixing, geo-grid reinforced gravel rafts)
Pre-loading (wick drains and surcharge filling)
Pile or structural raft foundations
No information has been provided in respect of building foundations or finished design levels. The
base of the valley through which the Ongaruhe Stream flows, and the location of the power plant, may
be underlain by topsoil and soft silt or loose sand alluvial material with pockets of organics. Soft
cohesive material or loose granular material may result in a lower bearing capacity for shallow
foundations. Conversely, even if relatively stiff soils are present, heavy and concentrated building
loads may exceed available bearing capacities for these soils and therefore require investigation,
specific foundation design and/or ground improvement.
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 8
3.4.2 Transmission Line Pylons
Foundations for the pylons are expected to comprise either pads or piles. The foundation conditions
are expected to comprise ash overlying Ongatiti Fm. Where practicable the foundations will be
embedded into the Ongatiti Formation.
The foundations for the transmission line are likely to be situated on or near sloping ground which may
be susceptible to or situated within areas of slope instability and erosion. Based on the assumption
that the proposed transmission line is located largely outside of the mapped alluvial basin,
consolidation settlement is unlikely to be a significant risk. The likely factors governing foundation
design will be the site stability, and the foundation bearing capacity, and elastic settlement limitations
for the pylons.
3.5
Liquefaction hazard
Given the presence of quaternary alluvial sediments and elevated groundwater conditions, it is
considered likely that soils underlying the Power Plant are susceptible to liquefaction-induced
settlement in the event of a design event earthquake. It is anticipated that the power plant, given that it
is a critical lifeline or service, will be an Importance Level 4 or 5 structure in accordance with
NZS1170.0:2011. It is very possible that liquefaction will result in unacceptable settlements across the
power plant footprint as a result of design level earthquake events. A detailed assessment of
liquefaction will need to be assessed through site specific ground investigation and subsequent
geotechnical analysis.
Options to mitigate or manage the effects of liquefaction are available and are similar in nature to
those proposed for managing settlement risk (i.e ground improvement, foundation strengthening) and
therefore is it anticipated that the foundation system for the power plant is likely to be designed to
mitigate multiple geotechnical hazards including consolidation settlement, low bearing capacity and
liquefaction hazard. It is considered that the site is at low risk from lateral spreading hazard due to the
limited depth and small size of adjacent stream channels.
3.6
Slope instability
Hills to the west/southwest of the Power Plant comprise areas of steep sloping ground rising
approximately 80 m above the valley. These slopes are of moderate to steep gradient with some
vegetation but evidence of instability (scarps or bluffs) is observed.
The risks associated with slope instability are best managed by relocating structures and roads away
from instability areas. If however this is not practicable then options for stabilisation may include the
following:
General slope stabilisation measures:


Slope re-profiling
Installation of drainage and erosion protection (vegetation and geotextiles)
In combination with general slope stabilisation measures, where there is a risk of debris inundation
from slips above a road or structure then the following options are available:



Debris bunds and catch fences
Retaining walls
Soil and rock stabilisation – soil nailing, rock bolting
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 9
In combination with general slope stabilisation measures, where there is a risk of under slip below the
edge of a road or foundation/structure then the following options are available:


Construct deep (pile) foundations
In-ground walls and or retaining walls
The transmission line route is situated within an area of slope instability risk which may impact the
location of and type of foundation proposed for the pylons, potentially on a foundation location specific
basis. Geomorphological mapping in the proposed alignment area will be important to identify
appropriate locations to put foundations which limit the risk posed from slope instability. This will be
followed by site specific geotechnical investigation to inform foundation and slope stability design.
The alignment along Access Area A is located near to the crest of sloping ground and formed within
cuts. There is potential for slope instability to cause washouts from below the access road, or for
inundation from above (Photo 7 provides an example of this situation). Ground investigation and
topographic survey of key slopes will be required to inform quantitative slope risk modelling to better
assess risk of instability along access ways.
Alternatively, if it is possible to reroute Access A away from sloping ground (recommending a
horizontal distance measured from the toe of offending slopes of three times the slope height) this
may limit need for more detailed investigation and quantitative analyses. Stability of existing tracks
may be improved through use of drainage, sealing the track surface and/or retaining walls.
3.7
Surface water and groundwater
A number of small streams are located within the valley floor that may need to be realigned and/or
culverted to redirect flow away from building areas. By re-aligning Access B it may be possible to
make use of existing culverts constructed below the farm access.
It is considered likely that any excavations to form shallow foundations or basements within the power
plant building footprint will intercept the groundwater table. This may require implementation of
appropriate drainage, dewatering and/or the use of drawdown wells.
Drainage measures are likely to be required for areas of instability where this is effecting infrastructure
in order to limit the risk of erosion caused by overland flow and groundwater seepage.
3.8
Earthworks
Any non-engineered fill or material with high organic content (such as peat) identified by ground
investigations will not be suitable for re-use as engineered fill. This material may be suitable for preloading or landscaping. Any non-engineered fill may need to be tested from environmental perspective
to confirm ongoing suitability for re-use on site. It is anticipated that site won natural ash soils will be
suitable for re-use as engineered fill for bulk earthworks landform modification subject to appropriate
testing. Imported granular fills are likely to be required for site drainage, roading pavements and to
form building foundations.
3.9
Environmental
The site is an operational dairy farm, and is expected to have remained as such for much of its
developed history. Dairy farms are not formally recognised by the Ministry for Environment (MfE) on
the Hazardous Activity and Industry List (HAIL) with potential to cause soil and groundwater
contamination. However it is recognised that dairy pasture within the Bay of Plenty and Waikato
regions have been widely sprayed with phosphate-based fertilisers that have resulted in gradual
accumulation of heavy elements such as arsenic and cadmium that often exceed the ‘background’
concentration set by regional councils.
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These elevated concentrations are not likely to be anywhere near human health soil contaminant
standards set by the NES (for commercial/industrial land use) or relevant ecological screening criteria.
As such the on-going risk associated with pasture to human health and environment is considered to
be low. Elevations above background do not meet the MfE definition of cleanfill, and as such, any offsite disposal of site soils should be undertaken in liaison with Waikato Regional Council.
The presence of additional contaminating activities beyond pastoral land use at the site has not been
assessed to date. A more detailed assessment of contamination issues may be required by
Otorohanga District Council to be assessed under the National Environmental Standard for Assessing
and Managing Contaminants in Soil to Protect Human Health Regulations (2011) as part of any future
land use or building consent application.
3.10 Further investigation
In order to support specimen and detailed design, extensive ground investigation will be required to
provide further analysis of geotechnical hazards and provide parameters for design. We recommend a
phased approach to investigation:

Non-intrusive geophysical investigation comprising MASW across the proposed Power Plant
footprint. The purpose of this investigation would be to provide low cost non-destructive
investigations over a wide area to confirm likely depth of bedrock, identify any key risk areas
requiring more targeted investigation (palaeochannels, obstructions, low density ground); and
provide classification of sub-soil class (in accordance with NZS1170) early in the design process.
This could be supplemented with some limited ground investigation to confirm interpretation of
MASW and provide more detailed observations of ground conditions to support specimen design.

Included within this phase would be a geomorphological mapping exercise to identify areas of slope
instability which will inform our recommendations for the roading alignments and foundation
locations for the transmission line pylons. The geomorphological mapping will be supported by
LIDAR and detailed instrument survey of key risk areas

Once design is further advanced, detailed geotechnical investigation at the locations of the key
design elements will be required to support design. The following investigations could be expected:
 Power Plant building: rotary boreholes, Cone Penetration Tests (CPT) and shallow investigations
(test pits or hand augers) to inform liquefaction and settlement analyses; earthworks and
foundation design.
 Access A: machine drilled boreholes and shallow investigations (test pits and hand augers) to
inform earthworks, slope stability analyses and design of civil infrastructure.
 Access B: Shallow investigations (test pits and hand augers) to inform earthworks and design of
civil infrastructure.
 220 kV transmission line: boreholes at the location of each pylon platform to inform slope stability
analyses and foundation design,
Please do not hesitate to contact the undersigned should you wish to discuss any of the above further.
Yours sincerely
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 11
Richard Griffiths
Senior Engineering Geologist
Attachments



Site Location Plan
Drawing 241157-L001
Site photographs (Aurecon, November 2015)
Limitations of this report
Aurecon has prepared this report in accordance with the brief as provided. The contents of the report
are for the sole use of the Client and no responsibility or liability will be accepted to any third party.
Data or opinions contained within the report may not be used in other contexts or for any other
purposes without Aurecon’s prior review and agreement.
Soil and rock formations are often variable, resulting in heterogeneous distribution of contaminants
across a site. Contaminant concentrations may be estimated at chosen sample locations, however,
conditions between sample sites can only be inferred on the basis of geological and hydrological
conditions and the nature and the extent of identified contamination. Boundaries between zones of
variable contamination are often indistinct, and therefore interpretation is based on available
information and the application of professional judgement.
Only a finite amount of information has been collected to meet the specific technical requirements of
the Client’s brief and this report does not purport to completely describe all the site characteristics and
properties. The nature and continuity of the ground between test locations has been inferred using
experience and judgment and it must be appreciated that actual conditions could vary from the
assumed model.
This report does not provide a complete assessment of the environmental status of the site, and it is
limited to the scope defined herein. Should further information become available regarding the
conditions at the site, including previously unknown likely sources of contamination, Aurecon reserves
the right to review the report in the context of the additional information.
This report has been prepared for the Client for its own use and is based on information provided.
Aurecon takes no responsibility and disclaims all liability whatsoever for any loss or damage that the
Client may suffer as a result of using or relying on any such information or recommendations
contained in this report, except to the extent Aurecon expressly indicates in this report that it has
verified the information to its satisfaction. This report is not to be reproduced either wholly or in part
without our prior written permission
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 12
Site inspection photographs
Photograph 1
Looking south at the entrance from SH39 into Access A
Photograph 2
Looking south-west towards SH39, through entrance paddock (Access A)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 13
Photograph 3
Looking north over crest of slope from Access A (Location 2)
Photograph 4
Sloping ground and minor failures below Access A (Location 2)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 14
Photograph 5
Shallow instability at top of crest, below Access A (Location 2)
Photograph 6
Earth bund and pond (Location 3)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 15
Photograph 7
Looking west along Access A (Location 4)
Photograph 8
Existing farm access cut within moderate slope, with exposed ash soils (Location 4)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 16
Photograph 9
Looking north over Power Plant building footprint
Photograph 10
Plunging ridgeline through centre of Power Plant building footprint
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 17
Photograph 11
Crest of plunging ridgeline (Location 6)
Photograph 12
Looking north at Ongaruhe Stream, with Access B to the right (Location 7)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 18
Photograph 13
Drainage channel running through centre of Power Plant footprint, looking north (Location 8)
Photograph 14
Looking north-west; Access B in foreground, Power Plant footprint in background
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 19
Photograph 15
Looking south along Access B, existing farm track with cut (Location 9)
Photograph 16
Looking south across Power Plant building footprint (culvert beneath existing track in midground)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 20
Photograph 17
Ongaruhe Stream (beneath trees) (Location 11)
Photograph 18
Looking south-west across paddock, where Access B deviates from existing track (Location 12)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 21
Photograph 19
Looking north towards Access B site entrance from SH39 (Location 13)
Photograph 20
Looking south along lower reaches of proposed 220 kV route (Location 14)
Project 241157 File 241157_PGAR_Rev0.docx 13 November 2015 Revision 0 Page 22
HIA ROAD
SH31 KAW
SS B
MAUI GAS
ACC
E
GAS
TOR
VEC
PROPOSED SITE
~3.92 Ha
176m
220m
PARCEL AREA
152.75 Ha
REFER TO DETAILED
SITE PLAN L-003
GAS SUPPLY
POS
LINE ED 220
kV
ROU
TE
AC
CE
A
WA
IPA
PRO
RIV
ER
SS
SH
3
1K
AW
H
IA
RO
AD
Y
HL
MI-
T
kV
220
75
0
150
300m
SCALE 1:7500
CLIENT
REV
DATE
REVISION DETAILS
APPROVED
DRAWN
DESIGNED
T.NICKLESS
B.McHARDY
CHECKED
R.CATHCART
4
3
2
1
0
30.10.15
19.12.14
22.10.14
04.04.14
03.04.14
ISSUED FOR RESOURCE CONSENT
ISSUED TO CLIENT
ISSUED PROJECT DESCRIPTION
Revised for Comment
Issued for Comment
C.Walters
C. Walters
C. Walters
C. Walters
C. Walters
PROJECT
PRELIMINARY
WAIKATO POWER PLANT
NOT FOR CONSTRUCTION
PROJECT No.
TITLE
APPROVED
DATE
C. Walters
241157
SCALE
SITE LOCATION PLAN
SHEET 1 OF 2
SIZE
AS SHOWN
A3
DRAWING No.
REV
L-001
4
KAW HIA R O
AD
Walton Subgroup (Puketoka & Kara
Holocene alluvium
Legend
Legal property boundaries
Section 75 Block XVI Pirongia
SD
¬
«
Power Plant Site
13
¬
«
Access A
11
Access B
Proposed 220 kV Line Route
¬
«
12
State Highway 39
Ongaruhe Stream
Tributaries
¬
«
10
Geology
Aotea Formation
Ongatiti Formation
Piako Subgroup
¬
«
9
Walton Subgroup (Puketoka &
Kara
¬
«
5
¬
«
10/11/2015 09:41
8
¬
«
14
¬
«
7
¬
«
6
¬
«
\\aurecon.info\shares\NZTRG\Projects\Projects\241157-Nova Energy Waikato OCGT Power Plant\CADD\GIS\GET
4
¬
«
15
Aotea Formation
¬
«
¬
«
¬
«
3
Waipa
River
Notes:
1. Image dated 2011 and sourced from the LINZ Data
Service ( https://data.linz.govt.nz/layer/1872-waikato-05m-rural
-aerial-photos-2012-2013/) and licensed by Waikato
Regional Aerial Photography Service (WRAPS) 2012 for
re-use under the Creative Commons Attribution 3.0 New
Zealand licence.
2
1
2. Location of proposed design elements approximate only.
Ongatiti Formation
Map by: RMG
Piako Subgroup
Date: 10/11/2015
°
A3 scale: 1:10,000
Job No: 241157
Projection: NZTM
Version: 0
300 MW Waikato Power Plant Preliminary Geotechnical Appraisal Report
Site Location Plan