BEFORE THE INDEPENDENT HEARING COMMISSIONERS

Transcription

1 BEFORE THE INDEPENDENT HEARING COMMISSIONERS AT Taupo IN THE MATTER AND IN THE MATTER of the Resource Management Act 1991 of the hearing of submissions on an application for resource consent by Kaiapo Bay Limited for subdivision and land use at Kaiapo Bay, Taupo STATEMENT OF PRIMARY EVIDENCE OF ANDRES MARTINEZ ON BEHALF OF KAIAPO BAY LTD GEOTECHNICAL ENGINEERING 12 NOVEMBER 2018

2 1. EXECUTIVE SUMMARY 1.1 None of the proposed building envelopes are considered to be affected by future displacements of the Kaiapo fault, which runs through the development. 2. INTRODUCTION 2.1 My full name is Andres Francisco Martinez, I hold a Bachelor of Civil Engineering degree and a postgraduate diploma in Environmental Engineering awarded in Colombia both verified by the New Zealand Qualification Assessment (NZQA) institution (application ). I also hold a postgraduate Masters degree in Geotechnical Engineering (own title from the polytechnic University of Madrid, Spain; in cooperation with the Ministry of Public Works and Transport). I am also an Engineering NZ Member and hold a Colombian engineering registration (COPNIA). 2.2 I have 12 years work experience, five and a half of them working overseas and six and a half working in New Zealand. Since working in New Zealand, I have completed almost 250 geotechnical investigations, mainly within the Waikato, Bay of Plenty and Hawke s Bay regions. I have a thorough knowledge of geotechnical conditions in the Taupo-Rotorua area, however I have also managed projects all around the North Island. I also participated with the Christchurch reconstruction, where a number of investigations related to liquefaction issues was completed. I have completed 3 fault alignment assessments within the Taupo-Rotorua area, as required by local authorities and several preliminary/comprehensive geotechnical investigations for subdivision projects. 2.3 I was the geotechnical engineer in charge of organising the on-site near to surface ground investigation, carrying out a desktop analysis of publicly available information and reporting about the findings. My role involved the definition of geological/geotechnical constraints potentially affecting the proposed development layout. Code of Conduct 2.4 Although this is a Council hearing, I have read the Environment Court's Code of Conduct and agree to comply with it. My qualifications as an expert are set out above. I confirm that the issues addressed in this statement of evidence are within my area of expertise. 2.5 I confim I understand the obligation contained within the Environment Court's Code of Conduct.

3 Scope of Evidence 2.6 My evidence will address, adequacy of the proposed building envelopes setback from the Kaiapo fault alignment. 2.7 Where appropriate and relevant, my evidence will reference and rely on the report of IGNS Science, with a copy of which is attached to this evidence 3. OVERVIEW OF THE PROPOSAL 3.1 The particular elements of the Proposal relevant to my evidence are as follows: (a) Adequacy of building envelopes locations with respect to the required setback from the trace of the Kaiapo fault. 3.2 Cheal Consultants Ltd was engaged by Kaiapo Bay Limited to undertake a preliminary geotechnical assessment for the proposed subdivision at Kaiapo Bay, Taupo. The purpose of the report was to define at an early stage of the subdivision, geotechnical constraints which could influence future construction of residential dwellings and associated infrastructure. 3.3 For analysis purposes, the whole site was divided into seven areas, each of which assessed against relevant land constraints (six in total). For all but one of the constraints, both remedial measures and construction recommendations were given. However, the item related to the presence of a fault line (Kaiapo fault) running through the development site was considered complex and consequently both construction techniques for residential dwelling and further consideration of consenting conditions were advised. 3.4 The Ministry for the Environment (MfE), technically supported by IGNS Science (GNS), produced in 2003 a guide titled Planning for Development of Land on or Close to Active Faults. That document is broadly used in New Zealand by planners, engineers and Local Authorities (among others) to direct land use planning approaches for land on or close to active faults, particularly to define measures to avoid or mitigate the risks associated with building on or close to active faults. 3.5 The first part of the guide (sections 2 to 9) focuses on the need for a risk-based approach to planning for land use on or near active faults. It recommends that Councils: Identify active faults in their district, with maps that are at the correct scale for the purpose. Create fault hazard avoidance zones on their district planning maps. 3

4 Evaulate the fault rupture hazard risk within each fault avoidance zone. Avoid building within fault hazard avoidance zones where possible. Mitigate the fault rupture hazard when building has taken place or will take place within a fault hazard avoidance zone. 3.6 The second part of the guide (sections 10/11) discusses the role of Regional Councils and Territorial Authorities in planning for fault rupture hazard. Section 11 describes how Councils can take a risk-based approach to establishing resource consent categories for buildings within or adjacent to the fault hazard avoidance zone. 3.7 Taupo District Council (TDC) District Plan (DP) Section 4e.10 Fault Line Hazard Area, states in 4e.10.1: Any structure excluding network utility lines, cables and pipelines (including support structures) within 20m of a fault line identified on the Planning Maps is a discretionary activity 3.8 TDC presents within its publicly available online geographic information system platform (MAPI) location of fault lines, including a 20m buffer each side of them, present within the District. 3.9 MAPI was used by Cheal, during recent planning stages of the proposed development, to locate building envelopes outside the 20m buffer from the trace of the Kaiapo fault GNS Science s website portal, also was publicly available information about active faults around New Zealand Further investigations were carried out by Coffey Consultants (August 2010). They based their conclusions on the potential effects of the fault on the proposed development on more accurate mapping techniques used by GNS to define the location of the fault Coffey s report also refers to a +/- 75m for the location of the fault, - ie a reported error of +/- 75m. I have assumed the +/- 75m was defined as a precautionary measure to cover their lack of assessment, understanding and interpretation of the particular faulting process After recent research done l found the +/- 75m as the maximum lateral area expected to be affected by a fault trace, as noticed from a consulting report prepared by IGNS for Rotorua District Council (GNS Rep 2010/182), of which we present Figure 5 (see Attachment 1) I pointed out the discrepancy in location of the fault between Taupo District Council s and GNS Science s information. 4

5 3.15 Since the section 92 request for further information on the faultlines, we asked IGNS to accurately plot the faultlines and provide a plan and report. This is attached to this evidence and is dated 14 th November IGNS s conclusion was that the main fault is further to the east than the Council MAPI data and clear of all proposed building sites. Lot 25 is the only one that has a building envelope close to the fault avoidance zone and so we have altered the shape of the envelope to keep out of the restrictive area MfE s guide does not prohibit/ban the placement of structures within a fault hazard avoidance zone, but rather describes how Councils can take a risk-based approach to establishing resource consent categories on those situations For this particular project, TDC could consider placing consent notices on the titles of the affected lots, requiring any potential owner of the land wanting to build within the IGNS setback to undertake either specific investigations to define the extension of the land prone to deform if future fault displacements occur, or to provide specific engineering design of foundations to withstand future land deformation Two approaches for fault definition based on trenching could be used. The first (finding the fault) involves trenching perpendicular to both sides of the defined fault trace to both confirm its location and to laterally define the extension of fault features (ie: antithetic faults) The second (finding fault features) involves trenching backwards from the location of the planned building and towards the fault, to evaluate potential marks/indications of the fault extending away from the defined fault trace Based on previous experience, the second approach is considered adequate for this site, as the potential extension of deformed ground due to the fault displacement could be defined (ie: antithetic faults, discontinuities on the materials layering etc) without effecting the slope created by the fault uplift (ie: trenching will not create an additional slope stability issue). 5

6 4. CONDITIONS 4.1 In considering all the information and extensive discussions and communication with IGNS it is my opinion that all proposed building envelopes areclear of any faultlines. However lots 5, 11, 24 & 25 are all close to the main fault. A consent notice could be registered on their titles alerting the the owners to this fact. ATTACHMENTS: 1. Figure 5 - IGNS Fault assessment and mapping 2. IGNS Report dated 13 November 2018 Andres Martinez [Geotechnical Engineer] 15 November

7 Attachment 1 Rotorua DC Faults Location, Figure 5

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9 Attachment 2 IGNS Report dated 13 November 2018

10 Letter Report No: CR 2018/180 LR Project No: 430W November 2018 Geotechnical Engineer Cheal Consultants Limited Level 1 4 Horomatangi Street Taupo 3330 Attention: Andreas Martinez 1 Fairway Drive, Avalon Lower Hutt 5010 PO Box Lower Hutt 5040 New Zealand T F Dear Andreas, Fault Avoidance Zones at Kaiapo Bay Subdivision, 15 & 37 Kaiapo Bay Rd, Acacia Bay, Taupo 1.0 INTRODUCTION AND SCOPE This report summarises the definition of Fault Avoidance Zones for the Kaiapo Bay Subdivision at 15 & 37 Kaiapo Bay Road, Acacia Bay, in the Taupo District. The Kaiapo Bay Subdivision partially overlaps previously mapped (1:250,000 scale) traces of the active Kaiapo Fault (Langridge et al., 2016). The Kaiapo Fault occurs within the Taupo Rift, one of the most tectonically active areas of New Zealand and which has numerous fault traces (Litchfield et al., 2014). The new Fault Avoidance Zones have been developed following the Ministry for the Environment s guidelines titled Planning for Development of Land on or Close to Active Faults (Kerr et al., 2003), hereafter referred to as the MfE Guidelines. The MfE Guidelines promote a risk-based approach for dealing with ground-surface fault rupture hazard, and at a specific site the hazard is characterised by two parameters: 1. location and complexity of surface rupture of the fault; and 2. activity of the fault, as measured by its average recurrence interval of surface rupture. The Fault Avoidance Zones have been developed utilising a high resolution Digital Elevation Model (DEM) derived from 2009 Light Detecting and Ranging (LiDAR) data collected by Taupo District Council and 1960 s aerial photography stereopairs (run 3192, photos 8-10). The Fault Avoidance Zones have only been developed for the Kaiapo Fault within the Kaiapo Bay Subdivision boundary (provided by Cheal Consultants Limited) to characterise the fault in that DISCLAIMER This report has been prepared by the Institute of Geological and Nuclear Sciences Limited (GNS Science) exclusively for and under contract to Cheal Consultants Limited. Unless otherwise agreed in writing by GNS Science, GNS Science accepts no responsibility for any use of or reliance on any contents of this report by any person other than Cheal Consultants Limited and shall not be liable to any person other than Cheal Consultants Limited, on any ground, for any loss, damage or expense arising from such use or reliance. Page 1 of 10 Institute of Geological and Nuclear Sciences Limited

11 location and, therefore, should only be applied within the subdivision at 15 & 37 Kaiapo Bay Road. The Fault Avoidance Zones are supplied as Geographic Information System (GIS) shapefiles which accompany this report. 2.0 FAULT AVOIDANCE ZONES The LiDAR data utilised in this report come from the 2009 survey collected by NZ Aerial Mapping Ltd for the Taupo District Council. The data was processed into a 1 m bare-earth DEM and hillshade model, which for this project, used a combination of illumination orientations from the northeast, north and northwest. Fault trace mapping for the current investigation was undertaken at approximately 1:1000 to 1:2500 scale. For this study, the Fault Avoidance Zones were developed by first identifying and mapping fault traces (Section 2.1), and then creating locational uncertainty zones and setback distances around the fault traces (Section 2.2) in accord with the recommended procedures in the MfE Guidelines. 2.1 Fault Traces Fault traces occur where past ruptures of a fault at depth have broken though to, and torn, the ground surface. It is the mitigation of the hazard posed by this tearing of the ground surface that is the intended aim of the MfE Guidelines. Table 2.1 provides definitions of the terms used in this report. Two main, subparallel traces of the Kaiapo Fault are mapped within, and impact, the Kaiapo Bay Subdivision (updated from Langridge et al., 2016). In addition, one newly identified shorter, possible fault trace was mapped as part of this investigation (Figure 2.1). Note that the red lines on Figure 2.1 are our best and simplest interpretation of where the fault plane has in the past, and will likely in the future, rupture the ground surface, but there is some uncertainty with respect to the exact location of the surface rupture deformation. This locational uncertainty is accommodated in the definition of Fault Avoidance Zone widths as is discussed later in this report. In the southeast portion of the subdivision, an accurate, well defined scarp is observed along the majority of the base of the slope. Utilising the high-quality LiDAR data, we have refined the location of this scarp (red line in Figure 2.1) and it now lies slightly further southeast than where the previous 1:250,000 scale mapping showed it to be (black line in Figure 2.1). Where the fault scarp crosses the stream, it has been eroded, and therefore its locational accuracy is reduced and accordingly we have mapped it as approximate. At its north-eastern extent (but still in the southern part of the subdivision), the fault scarp splays into two separate traces (Figure 2.1), which, according to the previous data (Langridge et al. 2016), connect to the two fault traces towards the northeast. However, this is outside the study area, so this connectivity has not been interpreted any further. The other active fault traces in the subdivision occur in the northeast. Here, the locations of the eastern and middle traces have been slightly refined from the previous 1:250,000 scale mapping (Figure 2.1) using LiDAR data. Where a fault scarp can be seen on the LiDAR data, Page 2 of 10 GNS Science

12 it is mapped as accurate and definite. Where it is not visible on the LiDAR, due to surface erosion or modification, it is mapped as approximate and either definite or likely. Overall, both traces have a clear geomorphic expression, with total surface scarp heights up to 60 m. The western strand splays into two at its southern extent as the change in elevation across the structure seems to occur in two steps. The westernmost strand (step) at this location has been mapped as a possible fault, rather than a definite fault because erosion has strongly modified the landscape. While we interpreted the change in elevation as a possible fault scarp, the surface expression of the possible fault is not sufficient at this location to map it as a definite fault. Table 2.1 Attribute Accuracy Certainty Exposure Definitions for the terms used in this report and accompanying GIS data. Definition Locational accuracy of the fault trace linked to the exposure and method (accurate, approximate, or uncertain) The likelihood that the feature is an active fault (definite, likely, or possible) The exposure of the fault trace in the landscape (exposed or eroded) Dominant slip type Down quadrant Method Fault complexity Deformation width Buffer distance Fault Avoidance Zone Fault Avoidance Zone Class Recurrence Interval Class Dominant or primary sense of movement on the fault (all normal in this case) The direction of the down-thrown side of the fault described in terms of quadrants Method used to locate the fault trace (LiDAR DEM or LiDAR hillshade) Clarity and extent of the surface expression of the deformed land caused by ground-surface fault rupture; if it is constrained within a narrow and obvious zone (well-defined) or if the traces cannot be identified because of erosion or burial (uncertain) Visible deformation width of scarps (i.e. fault complexity ) in meters represents zone of uncertainty in the location of future intense ground deformation Half of the deformation width in meters Sum of the deformation width plus the 20 m setback zone in meters The classification of the Fault Avoidance Zone (well defined, well defined - extended, or uncertain - constrained) The average time between surface rupturing events on a fault (all class I in this case) Page 3 of 10 GNS Science

13 Figure 2.1 New and previous fault mapping of the Kaiapo Fault within the Kaiapo Bay Subdivision using a hillshade model based on 2009 LiDAR data. Previous 1:250,000 scale linework is from the New Zealand Active Faults Database ( Note the fault lines mapped extend beyond the subdivision boundary but have not been mapped for this report. Individual fault traces are numbered and relate to trace numbers in Table A1.1, Appendix 1. All traces of the Kaiapo Fault within the Kaiapo Bay Subdivision are considered to be normal dip-slip faults 1, due to the active extensional stresses in this region, and the known normal sense of movement of the vast majority of active faults in the Taupo region. The accurate traces of the Kaiapo Fault are classified as well defined in terms of the fault complexity classification in the MfE Guidelines, while the approximate and uncertain traces have a fault complexity classification of uncertain. 1 The following link on the GNS Science website provides a description and explanation of the different types of faults (e.g. strike-slip, reverse, and normal): Topics/Earthquakes/Earthquakes-and-Faults/Different-types-of-Faults Page 4 of 10 GNS Science

14 2.2 Fault Avoidance Zones Fault Avoidance Zones are comprised of two parts: 1) the uncertainty of the exact location of the ground-surface fault rupture trace; and 2) the setback. The first step is to construct buffers around the fault traces which represent the uncertainty in the location (and width) of the fault rupture ground deformation, hereafter referred to as the fault deformation width (Figure 2.2). This area includes all ground-surface deformation associated with fault rupture but does not include secondary effects from the earthquake such as liquefaction or landslides. In practise, the fault deformation widths were derived from the scarp width (i.e., assuming future rupture is likely to be located where past rupture has occurred) and vary along the length of the fault depending on the certainty and accuracy of mapping. The fault deformation widths in the Kaiapo Bay Subdivision range from 6 to 30 m. The second step is to add a 20 m wide setback zone from this fault deformation width (Figure 2.2), as recommended by the MfE Guidelines (Kerr et al., 2003), to account for possible subresolution secondary deformation. Within the Kaiapo Bay Subdivision, the resulting Fault Avoidance Zones are between m wide (Table A1.1). Note that in the northeast portion of the subdivision, the majority of the previous 1:250,000 scale fault trace mapping falls within the newly defined Fault Avoidance Zones; whereas, in the southeast portion of the subdivision, the previous mapped fault traces lie outside of the new Fault Avoidance Zones. Page 5 of 10 GNS Science

15 Figure 2.2 model. Fault Avoidance Zones for the Kaiapo Fault within the Kaiapo Bay Subdivision overlying a hillshade Figure 2.3 shows the Fault Avoidance Zones in relation to the lot layout of the Kaiapo Bay Subdivision. The building footprint of lot 25 is affected by the newly mapped possible fault to the west. Page 6 of 10 GNS Science

16 Figure 2.3 Fault Avoidance Zones of the Kaiapo Fault in relation to the proposed lots within the Kaiapo Bay Subdivision as provided by Cheal Consultants Limited on 1 October KAIAPO FAULT RECURRENCE INTERVAL The Kaiapo Fault recurrence interval ranges between 460 and 630 years (Stirling et al., 2012; unpublished data) and the published mean recurrence interval is 530 years (Stirling et al., 2012). This places the Kaiapo Fault into Recurrence Interval Class I ( 2000 years) with a high level of confidence. 4.0 OPTIONS FOR THE NEWLY MAPPED TRACE The newly mapped trace appears to just affect the southeast edge of the building footprint on lot 25. The recommended option is to double check that there is no overlap between the building footprint and the Fault Avoidance Zone, and if there is, to shift the building footprint slightly to the northwest to avoid the Fault Avoidance Zone. If there is overlap and the building footprint cannot be moved, then we recommend undertaking paleoseismic trenching explorations to assess whether the trace that has been mapped as a possible fault is in fact an active fault. Based on this desktop study, the location shown in Figure 4.1 appears to be suitable for such a trench investigation. Basically, if it can be proven that the topographic feature is not a fault, then it poses no fault rupture ground deformation constraint on the subdivision. Page 7 of 10 GNS Science

17 Figure 4.1 The recommended site located at the southern extent of the newly mapped trace that could be trenched if required to determine whether this fault trace is in fact an active fault. 5.0 SUMMARY AND CONCLUSIONS Surface traces of the Kaiapo Fault have been defined within the boundary of the Kaiapo Bay Subdivision at a scale of between 1:1000-1:2500 using a high-resolution DEM derived from 2009 LiDAR data. Remapping of the fault traces has highlighted a new possible fault trace to the west of the two previously known main strands of the Kaiapo Fault. For all traces, Fault Avoidance Zones have been developed following the MfE Guidelines. The Fault Avoidance Zone classes include well defined, well defined - extended, and uncertain - constrain. The fault complexity of the Fault Avoidance Zones is classified as well defined where the traces are accurate, and uncertain in all other instances. The Fault Avoidance Zone of the new trace potentially affects the building footprint on lot 25. The remainder of the building sites fall outside of the mapped Fault Avoidance Zones for the Kaiapo Fault. The Kaiapo Fault has a published recurrence interval of 530 years, which places it in Recurrence Interval Class I ( 2000 years). If the building footprint on lot 25 overlaps the Fault Avoidance Zone and cannot be moved to avoid the Fault Avoidance Zone, we recommend trenching the fault trace at a suitable location in order to determine whether or not it is an active fault before proceeding with development plans. Page 8 of 10 GNS Science

18 6.0 REFERENCES Kerr J, Nathan S, Van Dissen R, Webb P, Brunsdon D, King A Planning for development of land on or close to active faults: An interim guideline to assist resource management planners in New Zealand. Lower Hutt (NZ): Institute of Geological & Nuclear Sciences. 56 p. (Institute of Geological & Nuclear Sciences client report; 2002/124). (prepared for, and published by the Ministry for the Environment, New Zealand). Langridge RM, Ries WF, Litchfield NJ, Villamor P, Van Dissen RJ, Barrell DJA, Rattenbury MS, Heron DW, Haubrock S, Townsend DB, et al The New Zealand Active Faults Database. New Zealand Journal of Geology and Geophysics. 59(1): doi: / Litchfield NJ, Van Dissen RJ, Sutherland R, Barnes PM, Cox SC, Norris R, Beavan RJ, Langridge RM, Villamor P, Berryman KR, Stirling MW, Nicol A, Nodder S, Lamarche G, Barrell DJA, Pettinga JR, Little T, Pondard N, Mountjoy JJ, Clark KJ A model of active faulting in New Zealand. New Zealand Journal of Geology and Geophysics. 57(1): doi: / Stirling MW, McVerry GH, Gerstenberger MC, Litchfield NJ, Van Dissen RJ, Berryman KR, Barnes P, Wallace LM, Villamor P, Langridge RM, Lamarche G, Nodder S, Reyners ME, Bradley B, Rhoades DA, Smith WD, Nicol A, Pettinga J, Clark KJ, Jacobs K National seismic hazard model for New Zealand: 2010 update. Bulletin of the Seismological Society of America. 102(4): doi: / Yours sincerely Regine Morgenstern Earthquake Geology Technician Pilar Villamor Earthquake Geologist Page 9 of 10 GNS Science

19 APPENDIX 1: Table A1. 1 Attributes for each fault trace shown in Figure 2.1. Trace No. Certainty Fault Complexity Fault Avoidance Zone Class Total Fault Avoidance Zone width (m) 1 definite uncertain well defined - extended 50 2 definite well defined well defined 48 3 definite uncertain well defined - extended 52 4 definite uncertain well defined - extended 55 5 definite uncertain well defined - extended 58 6 likely uncertain well defined - extended 60 7 definite uncertain uncertain - constrained 70 8 definite well defined well defined 50 9 definite well defined well defined likely uncertain well defined - extended definite uncertain well defined - extended definite uncertain well defined - extended definite well defined well defined definite well defined well defined definite uncertain well defined - extended definite uncertain well defined - extended definite well defined well defined definite uncertain well defined - extended definite well defined well defined likely uncertain well defined - extended definite well defined well defined definite uncertain well defined - extended definite uncertain well defined - extended definite uncertain well defined - extended definite uncertain uncertain - constrained definite well defined well defined likely uncertain uncertain - constrained possible uncertain uncertain - constrained 60 Page 10 of 10 GNS Science

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