T07 HMR Geotechnical Appraisal AEE Stage AppendixCDE

7/28/2019 T07 HMR Geotechnical Appraisal AEE Stage AppendixCDE

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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.



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.



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


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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Waikato W indfarm - Geotechnical Appraisal

Awhitu Group erosion and accreting sand dunes


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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Waikato W indfarm Geotechnical Appraisal

Cross Section showing instability within the Te Kuiti Group


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


Qvn

Pad

Ott

Legend Geology

Transmission Line




and rockfalls

Proposed substation

location

Lithology boundary

Pad - Awhitu Group

Kerikeri Volcanic Group

Qvn - Ngatutura Basalts

Te Kuiti Group



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Proposed Te Akau Substation

2311429 Figure E3

Ott

Mwk


Legend Geology

Transmission Line




and rockfalls

Proposed substation

location

Lithology boundary

Waitemata Group

Mwk - Koheroa Siltstone

Te Kuiti Group



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Proposed Orton Switching Station

2311429 Figure E4

Legend Geology

Transmission Line


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

T07 HMR Geotechnical Appraisal AEE Stage AppendixCDE

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