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Appendix C
Detailed Geological
Descriptions
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1 Detailed Descriptions of Geological Units1.1 Murihiku Supergroup (200 145 Million yrs)Comprises the fossiliferous Apotu and Huriwai Formations as discussed below.
1.1.1 Apotu Group (IJa)Weak to very strong indurated fossiliferous siltstones and conglomerate sequences (greywacke). The
distinctive red-brown weathering of the conglomerates are comprised of rounded volcanic and
angular sandstone and siltstone clasts in a sandstone matrix with interbedded grit and minor siltstone.
The Apotu group consists of a 1,500 2,500 m thick sequence, is exposed mainly east of the Kaimanga
Syncline and produces steeply inclined (30 - 50) slopes.
1.1.2 Huriwai Group (IJh)Extremely weak to moderately strong carbonaceous sandstone, siltstone and conglomerate with some
thin mudstones, and rare thin coal seams. Plant beds and tree stumps in positions of growth are
found locally. The Huriwai Group is up to 1,300 m thick, is exposed southeast of Port Waikato andslopes are steeply inclined (30 - 50). This unit is observed to have a weathered profile of up to 12m
comprising soft to very stiff clayey silts interbedded with sandy silts.
1.2 Te Kuiti Group (34 23.8 Million yrs)Comprises a transgressive sequence of rocks ranging from coal measures and freshwater siltstones
and grades up into marine sandstones and limestones. The Group is up to 500 m thick and comprises
the following units oldest to youngest.
1.2.1 Mangakotuku Formation (Otm)Typically occurs as a weak blue-grey siltstone with muddy glauconitic green sandstone in its lower
part. The siltstone is rich in montmorillonite and weathered outcrops are prone to slumping when
wet. This unit is up to 90m thick in the Glen Massey area, and thins to 40m in the Raglan district and
produces moderately inclined to gently inclined (10 - 15) slopes; steeply inclined slopes (30) within
the unweathered material.
1.2.2 Glen Massey Formation (Otg)The Glen Massey Formation makes an appearance throughout the windfarm site and usually consists
of three distinct units in vertical succession:
a. Elgood Limestone - A thin flaggy, crystalline sandy limestone, and/or calcareous glauconiticsandstone, up to 27m thick and occurs at the base of the Formation. This unit commonly is eroded and
has tomos (dolines) and caves; forms very steeply inclined bluffs (60 -70).
b. Dunphail Siltstone - grey calcareous siltstone usually 3-6m thick, with graded upper and lowercontacts; forms gently inclined slopes (10- 15).
c. Glen Massey Sandstone - grey-white massive fine to medium calcareous sandstone that isbetween 24-75m thick and forms very steeply inclined bluffs (60 - 70). The sandstone dominates the
formation forming prominent bluffs displaying honeycomb weathering and solution grooves.
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1.2.3 Whaingaroa Formation (Oti)Comprises massive light grey to blue-grey glauconitic, calcareous siltstone with a thin basal
glauconitic muddy fine grained sandstone to sandy siltstone up to 20m thick. The siltstone is prone to
frittering and conchoidal fracturing, which forms piles or gravels < 5 mm at the base of cuttings.
Upper and lower contacts are gradational and the unit is up to 150m thick in places. The Whaingaroa
Formation has lateral relationships with the Glen Massey and Aotea Formations and forms gently
inclined slopes (10- 15).
1.2.4 Aotea Formation (Ota)The Aotea Formation is lithologically variable in the vicinity of the project comprises the Waimai
Limestone Member, which is a cross bedded, flaggy, crystalline limestone, 6m thick and forms steeply
to very steeply inclined (50 - 70) conspicuous bluffs near the coast between Port Waikato and Matira.
1.2.5 Te Akatea Formation (Ott)The Te Akatea Formation comprises a very weak to weak light grey-white calcareous, massive or
weakly bedded siltstone to silty fine grained sandstone, which varies from 30m to 60m thick. This
unit forms gently inclined to steeply inclined slopes (60 - 10). The upper contact is irregular and
usually comprises a bored weathered surface.
1.2.6 Waitomo Sandstone (Oto)Occurs in the southern half of the wind farm site and comprises massive muddy calcareous fine to
medium sandstone with shells, up to 15m thick.
1.3 Waitemata Group (21.7-19 Million yrs)In the region of the wind farm the Waitemata Group consists of two distinct Members.
1.3.1 Waikawau Sandstone (Mww)A massive to well -bedded grey calcareous glauconitic fine to medium sandstone, commonly has
calcareous concretionary beds near the base. This unit is up to 50m thick and may contain some thin
siltstone interbeds with steeply inclined (30 - 35) slopes.
1.3.2 Koheroa Siltstone (Mwk)The Koheroa Siltstone overlies the Waikawau Sandstone and has a graded contact. This unit is light
grey to blue-grey massive to well bedded sandy siltstone commonly with sandstone beds up to 2m
thick. The siltstone is up to 75m thick and forms gently inclined (10 - 15) slopes when weathered;
moderately inclined (30) slopes when unweathered.
1.3.3 Amokura Formation (Mwa)East of the windfarm along the transmission line route is the Amokura Formation, which consists
predominantly of alternating 0.2 1.0 m thick graded sandstones and 0.05 - 0.2 m thick laminated
mudstones. Carbonaceous fragments are common throughout.
1.4 Pliocene and Quaternary Rocks (5.3 Million yrs to Recent)These units can be divided into the following three Groups, including the Kaihu Group, Tauranga
Group and the Kerikeri Volcanic Group.
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1.4.1 Kaawa Formation (Pk) (5.3 1.8 Million yrs)The Kaawa Formation comprises light grey to purplish yellow pumiceous sandstone underlain by a
shelly calcareous sandstone layer and unconformably overlies Waitemata Group Rocks. This unit is
restricted in outcrop locally between the Kaawa and Waikaretu Streams where it is observed to be
13m thick. This unit is confirmed to be a prolific water source if encountered.
1.4.2 Awhitu Group (Pad) (2.4-1.63 Million yrs)The Awhitu Group outcrops along the coast and overlies an irregular erosion surface above about
20m elevation. It is over 120m thick in the west but thins rapidly to the east. Gentle to steeply
inclined (up to 45) slopes are formed in this unit. The observed profile is observed to comprise 1m-
3m of firm sandy silts and silts overlying loose to dense weakly cemented fine to medium sand with
minor lignite and carbonaceous layers.
1.4.3 Karioitahi Group (eQd) (126,000 yrs-Recent)Early Pleistocene to Holocene grey weakly consolidated to loose coastal medium sand deposits of
shallow marine, beach and dune origins. This unit is observed to be capping hills up to 150m in
elevation producing moderately inclined slopes (30), and its overall thickness is unknown. This unitalso comprises the Bothwell, Hood and Mitiwai Sands.
a. Recent Mobile Dunes (Q1d last 14,000 yrs)Loose coastal mobile dune sands are up to 60m thick.
1.4.4 Kerikeri Volcanic Groupa. Ngatutura Basalt (Qvn) (1.83-1.54 Million yrs)Comprises a lava sheet of fine grained olivine basalt, agglomerates and tuff. Fresh basalt is rarely
exposed. Outcrops and cutslopes of the Ngatutura Basalts are gently to moderately inclined (10-30).
Comprisesi very strong to strong moderately weathered to slightly weathered basalt, with olivine
crystals up to 30 mm. The basalt is often overlain by up to 10m of highly weathered scoriaceous
boulders with weathering rinds up to 100 mm, overlain by a up to 12m weathered breccia comprising
dark red clayey silt with angular basalt and sedimentary gravels up to 100 mm.
b. Franklin Basalt (Qvs) (1.6-0.5 Million yrs)Restricted to the eastern corridor of the proposed transmission line near the Tee in area. Comprises a
lava sheet of fine to medium grained basalt.
1.4.5 Tauranga Group (1.8 Million yrs - Recent)Consists of a series of terrestrial (volcanic and loess), alluvial, and marine deposits consisting the
following:
Puketoka Formation (2 Million yrs to 340,000 yrs) (Pup) - Pumiceous alluvium interbedded withpeat horizons and volcanic ash deposits, forms elevated dissected terraces near the Waikato River.
Walton Subgroup (1.8 Million yrs to 340,000 yrs) (eQa) comprises pumiceous alluvium andcolluvium dominated by primary and reworked non-welded ignimbrite, forms elevated terraces
adjacent streams. Observed to occur as up to 4m of soft to firm silts and clayey silts, overlying
very soft to soft allophanic sandy silts, loose silty sands.
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Karapiro Formation (500,000-150,000 yrs) - (eQk) - Highly weathered pumiceous, coarse-grainedrhyolitic sands and current bedded grits interbedded with peat.
Volcanic Ash Horizons ( Hamilton Ash Formation) (340,000-Recent), these soils are not mappedin the area but are observed to form distinctive coverbeds mantling hill tops and infilling lower
lying areas greater than 4m thick in places. Comprises interbedded strongly weathered tephra
beds (allopahnic clayey silts) interbedded with paleosols (firm to stiff clayey silts) interbedded
with allophanic sandy silt-clay beds.
Recent Alluvium (Q1a) (last 14,000 yrs) consisting of pumiceous alluvium and swamp depositsthat infill low lying areas and form recent floodplains and comprises unconsolidated sand, silt,
mud and clay with local gravel layers and thin peat beds and overlies older alluvial deposits and
in places shelly estuarine deposits of previous interglacial periods. The alluvial and estuarine
sequence is observed to be up to 20m thick in places.
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Appendix D
Site Photographs &
Observations
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Waikato Windfarm Geotechnical Appraisal
View East
View North
View North West
Slope instability viewed from Waimai Hill
2311429 Site Photograph D1
LEGEND
recent shallow movement/slope instability.
historical and gentle creep/
debris flow/rockfalls of the
coarse units.
hummocky ground
(indication of slope movement)
Gentle Creep
Ponding of water on top of the impermeable Te
Akatea siltstone initiating creep and instability.
Scarp and outcrop of Te Akatea siltstone from
surfical instability and erosion of the overlying
Awhitu Group.
Evidence of historical slope instability and rockfalls
exposing outcrops and scarps of the Waimai
limestone due to failure on the underlying weaker
siltstone of the Te Kuiti Group.Ponding of water on top of an impermeable
siltstone of the Te Kuiti Group, initiates creep.
Shallow movement within easily
erodible Awhitu Group.
Shallow movement within easily
erodible Awhitu Group.
Evidence of historical slope instability and rockfalls
exposing outcrops and scarps of the Waimai
limestone due to failure on the underlying weaker
siltstone of the Te Kuiti Group.
Shallow movement within easily
erodible Awhitu Group.
Picture Summary
Recent surfical erosion and slope instability within the
overlying Awhitu Group is noted amongst the
surrounding topography. Water is ponded on top of the
siltstone. A perched water table lies on the
impermeable Te Akatea siltstones and saturates soils
initiating creep instability. Historical slope instability at
site is represented by the grassed hummocky ground
and scarps within the Te Akatea siltstone and Waimai
limestone. Historical and recent rockfalls were also
present.
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West of Pukerewa Road - Basalt Quarry
North of Rangikahu, view north, towards Waimai Stream (bottom)
Slope instability west of Pukerewa Road and near Rangikahu
2311429 Site Photograph D2
Basalt Quarry
Dune Formation withn
Awhitu Grou
Recent slope instability of Awhiti Group sands
exposing the underlying Te Kuiti Group
Picture Summary (above and right):
Recent surficial erosion and slope instability(creep and flow slides) within the overlying
Awhitu Group was noted as well as historical
slope instability.
Picture Summary (below):
Hummocky ground and surface ponding in the
area suggests historical slope instability.
Some recent surfical erosion is present but is
localized to zones of saturation within the
Awhitu and Karioitahi Groups. Note the gentle
dip slope towards the west, of the hills
comprising Te Kuiti Group.
LEGEND
recent shallow movement/
slope instability.
historical and gentle creep/
debris flow/rockfalls of the
coarse units.
hummocky ground
(indication of slope
movement)
Shallow slumping
Gentle dip slope of the Kuiti Group
hills. Hummocky groundSurface ponding of water
Accreting sand dune
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Awhitu Group erosion and accreting sand dunes
2311429 Site Photograph D3
Coastal erosional terraces
initiated by headward
erosion of a stream.
Loose Awhitu Group sands
interbedded with cemented
layers.
Loose sands erode back to
cemented horizons
Modern accreting sand
dune migrating inland at
the Waimai Valley.
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Cross Section showing instability within the Te Kuiti Group
2311429 Site Photograph D4
MURIHIKU SUPERGROUP
MANGAKOTUKU FORMATION
GLEN MASSEY FORMATION
WHAINGAROA FORMATION
AOTEA FORMATION
TE AKATEA
FORMATION
AWHITU GROUP
Drawing not to scale
Shallow surficial erosion
Failure of weak siltstone due to over-saturation from
water percolating through the overlying Awhitu Group
sandy deposits initiating creep movement and debris
flows.
Exposed limestone and sandstone bluffs due to
erosion of underlying siltstone. Blockfalls occur
due to rafting and/or failure of the underlying
siltstone.
Shallow instability and erosion of steeper slopes are
common. The unit is distinctively bedded and cut slopes
are prone to wedge failures and blockfalls.
TE
KUITIGROUP
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Appendix E
Substation Sites &
Investigation Locations
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Proposed Limestone Downs Substation
2311429 Figure E1
Q1a
Ott
Mww
Geology based on Edbrooke (2001 & 2005). Figure Not to Scale.
Ott
Mww
Legend Geology
Transmission Line
Transmision Line Corridor
Historical instability including
gentle creep/ debris flow
and rockfalls
Proposed substation
location
Lithology boundary
Tauranga Group
Q1a - Recent alluvium
Waitemata GroupMww - Waikawau Sandstone
Te Kuiti Group
Ott - Te Akatea Siltstone
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Proposed Matira Substation
2311429 Figure E2
Geology based on Edbrooke (2001 & 2005). Figure Not to Scale.
Qvn
Pad
Ott
Legend Geology
Transmission Line
Transmision Line Corridor
Historical instability including
gentle creep/ debris flow
and rockfalls
Proposed substation
location
Lithology boundary
Pad - Awhitu Group
Kerikeri Volcanic Group
Qvn - Ngatutura Basalts
Te Kuiti Group
Ott - Te Akatea Siltstone
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Proposed Te Akau Substation
2311429 Figure E3
Ott
Mwk
Geology based on Edbrooke (2001 & 2005). Figure Not to Scale.
Legend Geology
Transmission Line
Transmision Line Corridor
Historical instability including
gentle creep/ debris flow
and rockfalls
Proposed substation
location
Lithology boundary
Waitemata Group
Mwk - Koheroa Siltstone
Te Kuiti Group
Ott - Te Akatea Siltstone
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Proposed Orton Switching Station
2311429 Figure E4
Legend Geology
Transmission Line
Transmision Line Corridor
Historical instability includinggentle creep/ debris flow
and rockfalls
Proposed substation
location
Lithology boundary
Tauranga Group
Q1a - Recent Alluvium
eQk - Karapiro Formation
Waitemata Group
Mwa - Amokura Formation
Geology based on Edbrooke (2001). Figure Not to Scale.
Mwa
Q1a
eQkeQk
Mwa