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1 REPORT Proposed Second Runway Geotechnical Environmental Baseline Report Prepared for Prepared by Tonkin & Taylor Ltd Date October 2015 Job Number v3

2 Distribution: Tonkin & Taylor Ltd (FILE) 1 copy 1 copy

3 Table of contents 1 Introduction 1 2 Runway options 1 3 Site conditions 2 4 Previous geotechnical investigations Northern Runway Area of Influence Southern Runway Area of Influence 4 5 Geology 5 6 Subsurface conditions Northern Runway Southern Runway 6 7 Geotechnical considerations 6 8 Conclusions 10 9 Applicability 13 Appendix A : Figures Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

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5 1 1 Introduction Tonkin & Taylor Ltd (T+T) was engaged by (AIA) to complete a geotechnical assessment of the proposed second runway at Auckland Airport (Proposed Second Runway). Two main areas of influence are presently being considered by AIA for the Proposed Second Runway a northern and southern option. It is understood that the northern runway option is presently preferred and is therefore addressed in significantly more detail in this report. The geotechnical environmental baseline assessment has been completed using the results of historical geotechnical investigations completed by others, together with published geological maps, topographical data and T+T s geotechnical database for the area. The objectives of the study have been to: Assess the geological and geotechnical conditions in the Proposed Second Runway areas of influence; Identify geotechnical constraints for both Proposed Second Runway areas of influence ; and Summarise the key geotechnical design and construction considerations for the Proposed Second Runway design and construction in both the northern and southern areas of influence. 2 Runway options Two main areas of influence are presently being considered by AIA for the Proposed Second Runway options. These are illustrated on Figure 2-1 below. The northern area of influence is predominantly land-based extending from the western coastline of the airport precinct (south of the Ihumutao Quarry) to a tidal inlet of the Tautauroa Creek in the east. This land-based option is approximately 3,450 m long with an overall width (including parallel taxiways, rapid exits links etc.) of approximately 1,000 m. Two north-south running, parallel taxiways are proposed for connecting a northern runway to the international terminal and the Existing Runway and new terminal aprons for the future international terminal. It is understood that the north-south alignment of a northern runway option, together with the north-south taxiways and terminal aprons are common to all northern runway options, however, the western extent of the runway and adjoining taxiways may vary to include some reclamation into the Manukau Harbour. A 3,450 m long, fully land-based runway option is one possible option, however the east-west alignment of this runway could be modified to include a reclamation of up to 1,650 m length by 500 m width into the Manukau Harbour (see Figure 2-1 below). The eastern extent of a runway option, which includes reclamation at the western end, could terminate west of George Bolt Memorial Drive. The southern runway area of influence is wholly located south of the Existing Runway and would involve a 2,200 m wide by a maximum 3,450 m long reclamation into the Manukau Harbour. Parallel taxiways would run north and south of the Proposed Second Runway, together with rapid exit links. A remote terminal would be required to service aircraft using a southern runway to prevent the need for aircraft to taxi across the Existing Runway. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

6 2 Figure 2-1 Proposed Second Runway Areas of Influence 3 Site conditions The Designated Northern Runway extends over 3.4 km of predominantly greenfield land and traverses several shallow gully features. The topography of the site is typically low lying and gently sloping with ground elevations generally varying between RL 10 m and RL 20 m. This is some 5 to 10 m higher than the present runway and the International Terminal buildings. During 2008 and 2009, earthworks were undertaken to form a 1,200 m length of the Designated Northern Runway, over a width of 150 m. This work consisted of infilling gully features using site won fill. Earthworks were also carried out to form part of a north-south taxiway connecting the Designated Northern Runway to the airport terminals. The natural landform in these areas has therefore been extensively modified, as shown on Figure 2-2 below. Geotechnics a subsidiary company of T+T installed instrumentation for monitoring settlement of the natural ground following placement of the new fill in gully areas. Data from the profilometer instrumentation is available to T+T and has been used to appraise the compressibility and settlement characteristics of the subsoils. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

7 3 Figure 2-2: Aerial Photograph of the 2008/2009 Earthworks in the Northern Area of Influence Figure 2-3 below shows the ground surface topography over the northern area of influence with contours at 1 m intervals. The ground surface model presented in this figure pre-dates the earthworks completed between 2008 and 2009 and therefore does not show where gullies have already been infilled. The blue dots represent the locations of historical geotechnical investigations (machine boreholes, Cone Penetration Tests, hand auger boreholes etc). Figure 2-3: Surface topography and historical investigation locations Airport precinct Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

8 4 4 Previous geotechnical investigations 4.1 Northern Runway Area of Influence A large number of historical geotechnical investigations have been completed over the land-based northern area of influence. Historical test locations are shown on Figure 2-3 above and on Figures 1 to 5 attached in Appendix A. The investigations were completed for the Designated Northern Runway. Investigations were also completed and for extensions to the international terminal, taxiways and aprons. Data from a significant number of investigations completed by T+T for subdivisional works (associated with The Landing) and for individual building developments within the airport precinct have also been considered. These investigations have been used to develop a subsurface model for the northern area of influence as outlined in Section 6 below. A summary of historical investigations undertaken for the land-based northern area of influence is given below. SKM 2003 In 2003, SKM completed 116 cone penetration tests (CPTs) and 17 test pits along the alignment of the Designated Northern Runway. The investigations were positioned on the centreline of the runway, parallel taxiways and around the terminal aprons and taxiways. The locations of the SKM investigations are shown on Figures 1 to 5 in Appendix A. Beca 2003 Beca completed geotechnical investigations in 2003 for aircraft aprons and the Pier B area of the proposed International Terminal Building Stage 3 extension. The investigations comprised 13 fully cored machine boreholes, and 30 CPTs. Beca 2006/2007 In 2006 and 2007, Beca completed supplementary geotechnical investigations for the Designated Northern Runway, taxiways and terminal aprons. The 2006/2007 investigations comprised 21 fully cored, machine boreholes, 42 CPTs, and 68 test pits. The locations of these tests are shown on Figures 1 to 5. Beca 2011 Beca completed testing for the Dual Runway and Terminal Project in These investigations comprised 19 fully cored, machine boreholes, 10 CPTs and 60 hand augered boreholes. Test locations are shown on Figures 1 to 5 in Appendix A. 4.2 Southern Runway Area of Influence No geotechnical investigations have been undertaken for the southern area of influence or in the potential reclamation area of the northern runway option. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

9 5 5 Geology The published geology for the AIA region is presented on Figure 5-1 below. The areas shown in yellow are predominantly underlain by Puketoka Formation soils (estuarine deposits). The purple/red areas to the north, west and east of the airport region are former/present volcanic cones that were the source of a veneer of volcanic ash/tuff material which extends over the majority of the region. The grey represents fill material that was placed to reclaim land for construction of the Existing Runway and parts of the existing airport terminals and associated infrastructure. Figure 5-1: Regional Geology of the Auckland Airport Region 6 Subsurface conditions 6.1 Northern Runway Using the results of the historical geotechnical investigations summarised in Section 4 above and T+T s experience in conducting geotechnical investigations for subdivision and building projects at AIA, we expect that the northern land-based runway alignment will be underlain by the following sequence of geological units (in increasing age): Engineered fill (over the western extent of the alignment only, where the 2007/2008 Designated Northern Runway works were recently completed see Figure 2-2 above) comprising very stiff silty clays/clayey silts with undrained shear strengths exceeding 120 kpa; over 1.0 m to 2.0 m of weathered volcanic ash and tuff comprising very stiff to hard clayey SILT; overlying Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

10 6 Upper Puketoka Formation (Tauranga Group) estuarine deposits comprising intermixed layers of firm to stiff silty clay, organic silts, amorphous peat and loose sand layers (estuarine deposits); overlying Lower Puketoka Formation (Tauranga Group) medium dense to very dense silty sands (estuarine deposits); overlying Kaawa Formation very dense sands; occurring at depths of between 20 m and 35 m below natural ground level. Groundwater is present in both perched and regional regimes. Perched groundwater is usually present at near surface levels (between 2 and 5 m below ground level). 6.2 Southern Runway The subsurface conditions in the reclamation areas of the southern areas of influence are likely to comprise a surface layer of very soft/loose estuarine silts overlying Upper and Lower Puketoka Formation soils as outlined above. The surface layer of estuarine silts is likely to be normally consolidated and therefore of very low strength and highly compressible. This description also applies to the Northern runway reclamation area. 7 Geotechnical considerations The principle geotechnical considerations for the Proposed Second Runway development options are summarised below: Earthworks The majority of soils cut from the Designated Northern Runway alignment are expected to be suitable for re-use as engineered fill. The upper 3 to 4 m of the natural ground profile usually comprises volcanic ash/tuff clayey SILTs and very stiff Upper Puketoka Formation clayey SILTs. These soils are usually near to their optimum moisture content during the earthworks season and can therefore typically be placed without any requirement for soil conditioning. The volcanically derived soils particularly tuff soils at the western end of the northern area of influence which are probably sourced from the Ihumutao volcanic cone can be highly sensitive to disturbance when saturated. Trafficking and handling of these soils therefore needs to be undertaken in controlled conditions. Firm to soft clayey silts/silty clays and organic clays/silts are present from depths of around 5 m below natural ground level. These soils have moisture contents close to their liquid limit and therefore require significant drying back to achieve effective compaction to an engineered standard. The organic clays/silts will likely need to be blended with clean clays/silts to ensure that the organic content of the fill layer is limited to less than 3-5% to prevent long term settlement/ creep issues. Peat can be present at depths of between 5 and 10 m below ground level. The peat at Auckland Airport can be both fibrous and amorphous and with water contents of between 200 and 300%. These soils would not be suitable for use as engineered fill and would need to be removed from site. Relatively clean sand layers may also be present in the upper 5 to 10 m of the natural ground profile. These soils are unlikely to be suitable for direct placement as engineered fill, however they may be blended approximately 50/50 with clayey silts/silty clays to enable them to be more easily compacted. The loose sand layers are also usually fully saturated (being present below normal groundwater levels) and may therefore need to be dried back prior to blending/placement. For the southern alignment, rock fill will likely be required for reclamation works to at least 2 m above sea bed level. Cohesive fill may be suitable for use as fill once a working base of hard fill has been formed. Further comment is provided below in the Reclamation section. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

11 7 Soil Compressibility Compressible silts/clays and organic soils of the Puketoka Formation will consolidate and settle due to surcharging from the placement of new fill and construction of the Proposed Second Runway pavements. The magnitude of settlement and time taken for consolidation to occur under new fill areas will need to be calculated and allowed for in construction programming, i.e. the new fill will need to be in place for a sufficient period to enable consolidation settlement to be complete, well in advance of forming the runway pavement. T+T has conducted a review of historical settlement data sourced from instrumentation (profilometers) installed in gully features that were infilled during the 2008/2009 Designated Northern Runway earthworks. Data collected from these instruments indicates that the time to achieve approximately 90% of consolidation, due to the placement of up to 7 m of fill, was approximately 12 months. Where peat is present in layers of more than 1 m thickness, surcharging (temporary placement of fill above the design ground level) may need to be considered to mitigate secondary consolidation effects (creep) which could occur over the lifetime of the runway. Allowance for potential long term differential movements at cut fill boundary lines, which could affect the runway pavement over its design life, may need to be engineered using ground improvement works. For the southern area of influence, and any reclamation at the western end of the northern alignment, it will be critical to allow for sufficient load time to consolidate any marine sediments that are not excavated and removed prior to placing new fill. Further comment is provided below in the Reclamation section. Liquefiable Soils Potentially liquefiable loose silty sand layers are present within the Upper Puketoka and Lower Puketoka Formation units. Geotechnical investigations undertaken by T+T in recent years indicate that these soils have liquefaction trigger potential for seismic events with a return period as little as 150 years. The most susceptible layers to liquefaction are the loose sand /silt layers, usually present at depths of between 5 and 10 m, below the natural ground surface. The consequential effects of liquefaction are principally settlement (particularly where this occurs differentially and manifests at ground surface level) and lateral spreading which can result in instability toward a free (unsupported) face such as the coastline or the edge of a creek. The latter risk would need to be carefully considered for any Proposed Second Runway which involves reclamation or is within 100 m of the coastline. T+T recently completed a detailed desk study liquefaction assessment for AIA 1 (May 2014 Rev A). The conclusion of this study was that the Puketoka Formation loose sands and sandy silts are potentially liquefiable due to ground shaking from earthquakes with a return period as low as 100 years with increased consequential effects (greater settlement and greater risk of lateral spreading) for earthquakes with a return period greater than 250 years. However, it should be noted that the Puketoka Formation soils have high pumiceous contents which can conservatively skew the results of traditional liquefaction analyses (based on CPT data). Further detailed investigations comprising shear wave velocity testing, advanced laboratory testing (conducted at Auckland University) and confirmation of the site subsoil class - are recommended to further explore the risk of liquefaction occurring in the Puketoka Formation soils. 1 T+T Report. Liquefaction Risk Assessment Desk Study Auckland International Airport, dated May 2014 Revision A, T+T Ref Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

12 8 In the absence of detailed investigation data and comprehensive analyses confirming that the Puketoka Formation soils are not liquefiable, the consequences of liquefaction will need to be appropriately addressed in design. Careful consideration of this issue will be required for design of the runway pavement given the life-line importance of the airport to Auckland City. The lateral spreading risk associated with the southern area of influence, and any reclamation for the northern area of influence are expected to be more severe based upon typical marine sediment properties. Groundwater Levels Groundwater in the Auckland Airport region is usually present in both perched and regional regimes. Perched groundwater can be present at near surface levels during the winter months, falling to around 3 to 4 m below ground level in summer. Regional groundwater levels are governed by sea levels in the Manukau Harbour and water levels in tributary creeks which dissect the area. Subsoil drainage may form an essential component of the northern runway pavement design. The effects of lowering the groundwater level, where cuts of 5 to 10 m are required to form the runway, will also need to be assessed, particularly in relation to the potential for settlement under neighbouring buildings. The proposed T+T second runway investigations, to be conducted in October/November this year, will include installation of groundwater monitoring piezometers with electronic data loggers to measure groundwater levels at 10 minute intervals. Detailed groundwater analyses will be undertaken using this data to assess the potential groundwater drawdown effects of the proposed northern runway option on nearby buildings. Pavement Subgrade Conditions The northern runway option would have a highly variable subgrade extending through significant areas of new engineered fill (placed to achieve design surface elevations), volcanic ash/tuff, Upper Puketoka Formation silts/clays and organic silts/clays, peat and loose sands. Figures 10 to 12 attached illustrate the inferred subsurface model at an offset distance 72 m south of the northern runway area of influence. The inferred subgrade conditions are shown clearly on these sections, and summarised below in Table 1. Table 1: Inferred Northern Runway Subgrade Conditions (72 m south of centreline) Chainage Inferred Subgrade Conditions for Pavement Design & Construction 0 to 300 m 2 to 6 m of New Engineered Fill 300 to 400 m 1.5 to 2 m of Volcanic ash over 0.5 to 1.5 m of very stiff Puketoka Formation silts/clays 400 to to 7 m of New Engineered Fill Provisional Geotechnical Comments High strength fill materials for pavements, Relatively high strength soils for pavement construction. However, Volcanic ash soils have high sensitivity and will need to be protected during earthworks/construction (particularly in winter) High strength fill materials for pavements Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

13 9 Chainage Inferred Subgrade Conditions for Pavement Design & Construction 650 to m of Firm to Stiff Puketoka Formation silts/clays overlying loose silty sands to 3.5 m of organic clays/silts and/or amorphous peats exposed at runway subgrade level to 3 m of medium dense to dense sands overlying organic clays/silts and amorphous peats 2550 to to 2 m of volcanic ash overlying 2 to 3 m of firm very stiff Puketoka Formation silts/clays, over 2 to 3 m of organic soils 2900 to to 15 m of New Engineered Fill Provisional Geotechnical Comments Variable subgrade strength for pavement design/construction. Subgrade may require stabilisation if pavement construction is completed over winter months. May be significant drainage requirements (saturated subgrade) Significant ground improvement required for pavement construction (e.g. dig-out and replacement of peat soils and stabilisation of organic silts/clays) May be significant drainage requirements (saturated subgrade) Saturated sand subgrade may require cement stabilisation Underlying organic soils may be affected by heavy pavement loading (loading influence needs to be determined) May be significant drainage requirements (saturated subgrade) Relatively high strength soils for pavement construction. However, Volcanic ash soils have high sensitivity and will need to be protected during earthworks/construction (particularly in winter). Organic soils may be affected by heavy pavement loading High strength fill materials for pavements Stability The proposed runway fill embankments for the northern runway option extend up to 15 m in height at the eastern most extent. These will need to be supported by stable batter slopes where there is sufficient vacant land available to extend the area of earthworks. A preliminary, assumed batter slope of 2H:1V for engineered fill materials would result in the fill slopes extending to a maximum of 30 m beyond the runway platform. Such slopes would need to be analysed to ensure that they perform adequately under both static and seismic conditions. Staging of the filling may also be necessary to ensure that pore excess water pressures, exceeding the effective stress of the natural soils, are not generated during earthworks. Where there is insufficient vacant land available to form batter slopes to support the Proposed Second Runway platform (e.g. at the coastal margins of the northern land-based runway option), it may be necessary to construct retaining structures (e.g. mechanically earth stabilised walls) to support any new filling and the runway pavement. These would be significant structures that would require detailed analyses and assessment to ensure that they have both local and global stability under a range of operating conditions static and seismic. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

14 10 Reclamation The northern area of influence includes the potential for reclamation at the western end of the runway alignment extending up to 1,650 m west of the present coastline. The southern area of influence is entirely located within the present Manukau Harbour and would need to be wholly reclaimed. This would extend over an area of approximately 2,200 m x 3,450 m (~ 760 ha), minus the existing area of Wiroa Island and an adjoining piece of land at the eastern end of the present runway. Soft, normally consolidated, estuarine soils are expected to be present at ground surface level in the northern and southern reclamation areas. These soils are expected to be highly compressible and would therefore need to be excavated and removed prior to filling, or treated in situ (e.g. by cement stabilisation) beneath the runway pavement alignment. Alternatively, settlement of the soils (from fill placement) could be allowed for in design, e.g. by surcharging the runway/taxiway alignment (possibly in combination with wick drains) from finished design level. Earthworks in reclamation areas is challenging and cannot easily be undertaken in fully saturated conditions. There are a number of different construction methodologies that could be employed to enable filling to progress. One option that was recently adopted for reclamation of the Onehunga Foreshore involved construction of a perimeter bund around the extents of the reclamation. The bund would likely need to be formed of materials that would mitigate seepage inflow at high tides. Localised treatment of the natural soils around the toe of the bunds may also be needed to prevent water inflows occurring from the base of the reclamation. Even assuming the perimeter bunds are well constructed, it would be near impossible to achieve fully drained conditions for earthworks. Therefore, placement of cohesive (clay) fill is unlikely to be practical in the lower 1 to 2 m of the reclamation, i.e. a rock or hardfill material would likely be required at the base of the reclamation to achieve a compacted/engineered base. Cohesive fill could be placed on top of the base layer provided that dry working conditions were achieved. In addition to the geotechnical issues for reclamation works, coastal issues and effects would need to be considered for any reclamation option. These would include tidal effects, erosion, sea level rise and wave action. These design issues are discussed in more detail in the T+T Coastal Report (ref 1) dated October Petrified Kauri Forest The remnants of a petrified Kauri Forest are located along the coastal fringe at the far western extent of the northern runway area of influence. This is a protected geological feature and, as such, any development in this area will need to be carefully detailed to minimise impact and effects. 8 Conclusions This report has been prepared to provide a geotechnical assessment of the geological and geotechnical conditions for the two areas of influence being considered for a second runway at Auckland International Airport. The two areas have considerably different geotechnical constraints and considerations the northern area of influence being predominantly land based and the southern area of influence located wholly within the Manukau Harbour on reclaimed land. The geology of the Auckland Airport region is dominated by the Puketoka Formation geological unit, with some influence from the many nearby volcanic cones which surround the area. The Puketoka Formation can typically be separated into an upper layer (usually within m of ground level) and a lower layer (greater than m depth). The upper Puketoka Formation unit comprises geotechnically challenging soils comprising compressible silts/clays and organic silts/clays together Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

15 11 with isolated layers of amorphous and fibrous peat. Loose silty sand layers are also present within the Upper Puketoka Formation and these have been calculated to have susceptibility to liquefaction. Volcanic ash and tuff soils usually mantle the Upper Puketoka Formation with a typical thickness of 1 to 2 m. These soils are typically very stiff and perform well under a range of engineering conditions, except when heavily saturated and subject to disturbance (e.g. trafficking). The Lower Puketoka Formation typically comprise medium dense to very dense sands and silty sands. These soils are typically inert from an engineering perspective with low compressibility, limited liquefaction susceptibility and high bearing strength. Whilst no specific investigation data is available from the potential reclamation zones in the northern and southern areas of influence, these areas are likely to have a surface layer of very soft, normally consolidated estuarine silts. The underlying base geology is expected to be similar to that presented for the northern area i.e. Upper and Lower Puketoka Formation estuarine deposits. Groundwater is generally present in both perched and a regional regimes in the airport region. The perched groundwater can be present at near surface levels (1 to 2 m depth) during the winter months, dropping to around 3 to 4 m depth in summer. The regional groundwater level is governed by sea levels of the Manukau Harbour around the coastal fringe and by water levels in the many gullies/creeks that dissect the area. The northern area of influence is mostly land based and traverses variable topography with elevations typically ranging between RL 10 and RL 20 m. Significant earthworks would be required to form the design platform level for the northern area of influence with cut depths of up to 8 m and fill thicknesses of up to 15 m at the western eastern extent of the alignment. Such earthworks would extend through a range of different geological units as outlined above including volcanic ash/tuff, very stiff to stiff clayey silts, loose silty sands, soft to firm organic clays and peats. Each of these soils have different engineering properties which would need to be considered for earthworks and pavement design and construction. The principal geotechnical considerations for the Proposed Second Runway development will be as follows: The suitability of site won cut material for re-use as engineered fill. In general most of the site won materials are likely to be suitable for re-use, however, soil cuts from a depth greater than 3 to 4 m below natural ground level area likely to require some conditioning. Any loose sand, organic silt/clay and normally consolidated silts excavated from the harbour are likely to require both conditioning and blending with clean clay/silts to enable their effective re-use as fill. Amorphous and fibrous peats will need to be excavated and removed off-site. Soil compressibility. The placement of new fill over compressible natural soils such as the organic silts/clays and peats present within the Upper Puektoka Formation unit will result in consolidation and long term creep settlement. The magnitude of settlements could range between 100 and 300 mm for the land based northern area of influence, depending on the height of fill placed, and the period of consolidation may take between 12 and 24 months to occur. Allowance may also need to be made for long term creep of any organic soils (particular fibrous peat) present beneath fill areas. Liquefiable soils. Layers of loose silty sand are present in the Upper Puketoka Formation and occasionally in the Lower Puketoka Formation units. Historical analyses and studies have indicated that these soils are susceptible to liquefaction under seismic shaking. For earthquakes with return periods greater than 250 years, the effects of liquefaction can include differential settlement at ground surface and lateral spreading, within 200 m of an unsupported face, such as the coastline. Liquefaction may be a significant consideration for Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

16 12 pavement design (where the pavement is within 3m vertically of a liquefiable layer) and for any part of the runway extending within 200 m of the coastline (e.g. for reclamation areas). Groundwater effects. Runway earthworks involving excavations of around 5 m or more may result in permanent groundwater drawdown. The principle engineering effect of groundwater drawdown is consolidation settlement of compressible soils due to an increase in effective stress. This will need to be considered during the design stages of the project. Subgrade Conditions. The Proposed Second Runway for the land-based northern area of influence will extend through a range of different soil types and geological units including engineered fill, volcanic ash/tuff, very stiff to stiff Puketoka Formation clays/silts, soft-firm organic clays/silts, peats and loose silty sands. The engineered fill, volcanic ash/tuff and the upper 2 m of the Upper Puketoka Formation unit (very stiff to stiff clayey silts) are expected to provide a reasonable subgrade for construction of the runway pavement. However, improvements or treatment may be required in areas of the Proposed Second Runway that extend through soft-firm organic clays, peat and loose silty sands. Improvements/treatments could include excavation and replacement, lime/cement stabilisation or excavation and mixing/blending with clean clay fills. Stability. Construction of the Proposed Second Runway will involve significant areas of filling to fill gully features, reclaim land or to simply lift the runway pavement to the design finished elevation. Where there is available land to accommodate batter slopes, buttressing fill could be used to support elevated platform areas. Alternatively, retention structures such as Mechanically Stabilised Earth (MSE) walls could be employed to support new fill. Detailed analyses will be required to confirm both the local and global stability of batter slopes and retaining structures. Reclamation. The northern area of influence includes the potential for a 1,650 m long by 500 m wide reclamation into the Manukau Harbour. The Southern area of influence would be almost wholly reclaimed over an area of approximately 760 ha (less the Wiroa Island land mass). Soft marine sediments are likely to be present over the harbour bed and these would either need to be excavated and removed or treated to minimise the risk of long term settlements occurring. Alternatively, the completed runway earthworks platform could be surcharged, possibly in combination with wick drains, to mitigate the risk of settlement. Compaction of new fill within the reclamation area would be geotechnically challenging, necessitating well developed construction methodologies to control seepage inflows within a tidal zone. Hardfill may also be required over the lower 1 to 2 m of the reclamation to form a base platform to operate earthmoving equipment. Tonkin & Taylor Ltd Proposed Second Runway - Geotechnical Environmental Baseline Report October 2015 Job No: v3

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19 Appendix A : Figures Historical Investigation Location Plans Northern Area of Influence Geological Long Section Northern Area of Influence

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21 L:\29777\ \WorkingMaterial\CAD\FIG\ F1_F5.dwg, F1, 19/06/2015 1:32:15 p.m., jatg, 1:2 This report has been updated in response to further information requests. See Appendix 14 to AIAL response to further information request on 4 October DRAWING STATUS: Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09) PRELIMINARY DRAFT

22 This report has been updated in response to further information requests. See Appendix 14 to AIAL response to further information request on 4 October L:\29777\ \WorkingMaterial\CAD\FIG\ F1_F5.dwg, F2, 19/06/2015 1:32:29 p.m., jatg, 1: Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09) DRAWING STATUS: PRELIMINARY DRAFT

23 This report has been updated in response to further information requests. See Appendix 14 to AIAL response to further information request on 4 October L:\29777\ \WorkingMaterial\CAD\FIG\ F1_F5.dwg, F3, 19/06/2015 1:32:43 p.m., jatg, 1:2 4 Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09) DRAWING STATUS: PRELIMINARY DRAFT

24 This report has been updated in response to further information requests. See Appendix 14 to AIAL response to further information request on 4 October L:\29777\ \WorkingMaterial\CAD\FIG\ F1_F5.dwg, F4, 19/06/2015 1:32:54 p.m., jatg, 1: Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09) DRAWING STATUS: PRELIMINARY DRAFT

25 This report has been updated in response to further information requests. See Appendix 14 to AIAL response to further information request on 4 October L:\29777\ \WorkingMaterial\CAD\FIG\ F1_F5.dwg, F5, 19/06/2015 1:33:06 p.m., jatg, 1:2 4 Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09) DRAWING STATUS: PRELIMINARY DRAFT

26 L:\29777\ \WorkingMaterial\CAD\FIG\ F10_F11.dwg, F10, 22/06/2015 1:05:50 p.m., jatg, 1:2 Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09)

27 L:\29777\ \WorkingMaterial\CAD\FIG\ F10_F11.dwg, F11, 22/06/2015 1:06:13 p.m., jatg, 1:2 Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09)

28 L:\29777\ \WorkingMaterial\CAD\FIG\ F10_F11.dwg, F12, 22/06/2015 1:06:29 p.m., jatg, 1:2 Tonkin & Taylor Environmental and Engineering Consultants 105 Carlton Gore Road, Newmarket, Auckland Tel. (09) Fax. (09)

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