Search
× Search
Menu
  1. Home
  2. General
  3. Infrastructure Development Processes
  4. Quality Assurance Information Requirements
    1. QA-1 Resource Consent Application Requirements
    2. QA-2 Works Undertaken By or For a Council
    3. QA-3 Development Works Approval
    4. QA-4 Survey Plan (s223) Approval
    5. QA-5 Final Sign Off (s224c) Application Requirements
    6. QA-6 As-Built Information
    7. QA-7 Bonds and Maintenance Fee
    8. QA-8 Building Consent Considerations
  5. Design Standards
    1. DS-1 General Provisions
    2. DS-2 Streetscape
    3. DS-3 Reserves
    4. DS-4 Transportation Network
    5. DS-5 Stormwater
    6. DS-6 Wastewater
    7. DS-7 Water Supply
    8. DS-8 Public Lighting
    9. DS-9 Network Utilities
    10. DS-10 Natural Hazards & Earthworks
    11. DS-11 Road Zone/Road Reserve Occupancy
    12. DS-12 Building Consent Considerations
  6. Standard Drawings
    1. SD-1 General Provisions
    2. Street design diagrams
    3. T100 Perspective Drawings
    4. T200 Streetscape
    5. T300 Reserves
    6. T400 Transport Network
    7. T500 Stormwater
    8. T600 Wastewater
    9. T700 Water Supply
    10. T800 Public Lighting
    11. AB As-Built Drawings
  7. Approved Materials
  8. Construction Standards
    1. CS-1 General
    2. CS-2 Site Clearance
    3. CS-3 Earthworks
    4. CS-4 Excavation
    5. CS-5 Excavation in Trench
    6. CS-6 Fill
    7. CS-7 Bedding & Backfill
    8. CS-8 Subsoil Drainage for Earthworks & Roads
    9. CS-9 Pipework
    10. CS-10 Pipe Fittings
    11. CS-11 Manholes & Rodding Eyes
    12. CS-12 Sumps
    13. CS-13 Trenchless Technology
    14. CS-14 Road Ripping
    15. CS-15 Road Pavement Layers
    16. CS-16 Kerb & Channel
    17. CS-17 Concrete Work
    18. CS-18 Carriageway Surfacing
    19. CS-19 Roadmarking
    20. CS-20 Berm Features
    21. CS-21 Street Structures
    22. CS-22 Road Maintenance
    23. CS-23 Grassing & Turfing
    24. CS-24 Vegetation Planting & Gardens
    25. CS-25 Reinstatement
  9. Inspection & Testing Requirements
    1. IT-1 General Provision
    2. IT-2 Streetscape
    3. IT-3 Reserves
    4. IT-4 Transportation Network
    5. IT-5 Stormwater
    6. IT-6 Wastewater
    7. IT-7 Water Supply
    8. IT-8 Public Lighting
    9. IT-9 Network Utilities
Infrastructure Development Code

DS-10 - Appendix E - Assessment and Reporting

PreviousNext

DS-10 - Appendix E.1   General

The assessment of landforms shall utilise the following and may be supplemented by the expert opinion stated in the documents noted in DS-10 APX A Associated Standards:

  1. All earthworks for a development shall:
    1. Comply with the design criteria for completed landforms.
    2. Take the reduction of overland flow velocity and the concentration of overland flow into account for the completed landform geometry and gradients.
    3. Provide for the permanent management of overland flow across landforms (contour drains, cut-off drains, formalised overland flowpaths not forming accessways etc).
    4. Provide for the construction of man-made structures to create safe landforms and designed building platforms.
    5. Where necessary provide for the installation of debris protection devices.
    6. Define the earth fill and subgrade construction standards, define testing frequency, volumes and outline methods of testing to be used.
  2. Observation, quality assurance and review of the earthworks design during the construction phase are covered in CS-3 Earthworks. Engineering appraisal and design are required:
    1. Prior to detailed planning, which may involve some form of subsurface investigation.
    2. During the review of and advice on design concepts.
    3. During construction to ensure the adequacy of the bulk filling and the execution of the earthworks design.
  3. Development Evaluation Reports and Geotechnical Completion Reports relating to Category 1 and Category 2 landforms shall:
    1. Be subject to a level of quality control appropriate to the complexity of the project. This extends to an independent review within the company preparing the report of the technical areas, key assumptions of the report, investigation findings, adopted soils model, parameters and final conclusions opinions.
    2. Presence of and influence on the development from existing geomorphic features.
    3. Assessment of historic landform stability and landform processes.
    4. Other engineering issues influencing the proposed development such as but not restricted to, seismic stability, liquefaction, shrink/swell effects, settlement issues, foundation requirements, limitations on surface water run-off etc.
    5. In undertaking the assessment, the expertise of both a Geo-Professional and Professional Engineering Geologist may be required to ensure a full understanding of the site is gained.

DS-10 - Appendix E.2   Balancing Landform Choices

The final choice of landform is dependent on many factors, which may be specific to the development. These include the:

  1. Relationship with surrounding landscapes.
  2. Current building practices in the area e.g. a preference for flat building sites.
  3. Natural drainage patterns.
  4. Size of the development.
  5. Proposed and existing roading patterns.
  6. Preservation of natural features.
  7. Enhancement of natural features where compromised by fragmentation or reduction due to the development.
  8. Stability of the land.
  9. Function and purpose of the development.
  10. Potential for flooding, erosion and other natural events.

The order of importance of these factors will vary from project to project. The final choice of landform shall represent the most desirable compromise between the development requirements, the preservation of natural features including the existing soil profile and the natural quality of the landscape. Preservation aspects include retaining natural watercourses and excluding any development from natural gullies or overland flowpaths (refer to the City Plan).

DS-10 - Appendix E.3   Reducing Waste

When designing the development, consider ways in which waste can be reduced:

  1. Design to reduce waste during construction e.g. minimise earthworks, reuse excavated material elsewhere.
  2. Use materials with a high recyclable content e.g. recycled concrete subbase. Proposed recycled materials will need approval from the Council to ensure that environmental contamination does not occur.

Refer to the Resource Efficiency in the Building and Related Industries (REBRI) website for guidelines on incorporating waste reduction in your project www.rebri.org.nz.

DS-10 - Appendix E.4   Existing Landforms

Study the general nature and shape of the ground and take particular note of:

  1. The geological nature and distribution of soils and rock.
  2. Existing and proposed drainage conditions and the likely effects on groundwater.
  3. The previous history of ground movements in similar soils in the area.
  4. Where earthworks are involved, the performance of comparable cuts and fills (if any) in adjacent areas.
  5. Where peat is present, ensure the geotechnical design will achieve the infrastructure design life required by all other parts of the IDC. Preserve the flow of groundwater through the peat at pre-development levels e.g. by way of pipework/ gravel drains etc.

Aerial photography and other sources of information shall be reviewed and incorporated into any slope stability assessment.

DS-10 - Appendix E.5   Suitability

The choice of a suitable landform is dependent on many factors that may be specific to a particular site. Avoid unnecessary earthworks, aim to protect original soils and drainage patterns and to minimise disturbance, compaction, earthworks and importation of topsoil, although earthworks may be justified in the following circumstances to:

  1. Minimise the risk of property damage through ground movement in the form of rock fall, slips, subsidence, creep, erosion or settlement.
  2. Minimise the risk of property damage through flooding, or surface water run-off.
  3. Lessen tunnel gully erosion within hillside developments.
  4. Develop a more desirable roading pattern with improved accessibility to and within the site, and to create a better sense of orientation and identity for the area as a whole.
  5. Increase the efficiency of overall land use, including the quality of individual sites and amenity areas around buildings, the economics of providing engineering services and the standard of roading and on-site vehicular access.
  6. Create, where needed, suitably graded areas for playing fields and other community facilities.
  7. Enhance the general environmental character of the area by softening the landscape or by artificially creating or emphasizing landforms of visual significance, particularly on flat sites or on areas devoid of landscape features.

DS-10 - Appendix E.6   Seismic Considerations

Consider the seismic effects on earth fills, slopes and liquefiable ground, and take these into account in the design and construction of any development.

DS-10 - Appendix E.7  Description of Geomorphological Zones and Assessment Guidelines

DS-10 - Appendix E.7 Table 2: Description of Geomorphological Zones and Assessment Guidelines

Geotechnical Risk Category Assessment Guidelines

Very High and High Risk

Category 1 Geo-Professional

Requires extensive and detailed engineering geological and geotechnical assessment. Intensive investigation may be required and development may not be economically feasible. Boreholes to determine geology present will be required.
Assessment of site required by both Professional engineering geologist and Geo-Professionals.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. Initial assessment to be carried out by Category 1 Geo-Professional (Professional Engineering Geologist and Geotechnical Engineer) 
  2. b) Examination, on foot, of the surface of the site and the surrounding ground, with the assistance of existing topographical maps
  3. Examination of available aerial photographs of the area (include selection from early to present time)
  4. Assessment of available geological data (IGNS and other maps, publications, university theses and any other published or unpublished data)
  5. Review of relevant files and other historical records
  6. Check with local residence and other sources for evidence of past instability, particularly during periods of heavy rainfall
  7. Prepare preliminary report including geomorphological map of site, detailed cross sections showing site stratigraphy, preliminary conclusions on site characteristics and recommendations for additional investigation, mapping and monitoring. Report to include specific reference to all aerial photographs and other sources of information used for the study
  8. Geomorphological assessment to provide conclusion on characteristics of any landslide present and the history of movement (historical or current)
  9. If landslide with recent movement effects the site, further topographical surveys, ground investigations and stability analysis will be required to demonstrate that the site can be made adequately safe by remedial works
  10. Undertake investigation to determine the nature and distribution of the soils that may be prone to slip and develop engineering geology site model
  11. Measure groundwater pressures in the soils strata and evaluate the transient pressures that may develop ender extreme rainfall conditions
  12. Produce engineering geological report with details of mass movement features and other ground failure hazards
  13. Carry out geotechnical evaluation, using Category 1 Geo-Professional and including further sampling, laboratory testing, assessment of ground properties, groundwater monitoring, etc. If strength assessment has been made by reference to test data from the other sites, provide detailed rationale for the use of such data
  14. Undertake slope stability evaluation using approved methods
  15. Make recommendations for use of site and provide design for remedial measures if appropriate

Moderate Risk

Category 2 Geo-Professional

Some sites may require detailed engineering geological and geotechnical assessment
Visual assessment. Hand and possible drill investigation methods.

  1. Assessment to be carried out by Category 1 or 2 Geo-Professional (Professional Engineering Geologist /geomorphologist and/or Geotechnical Engineer)
  2. Examination, on foot, of the surface of the site and the surrounding ground, with the assistance of existing topographical maps
  3. Examination of available aerial photographs of the area (include selection from early to present time)
  4. Assessment of available geological data (IGNS and other maps, publications, university theses and any other published or unpublished data)
  5. Review of council files and other historical records
  6. Check with local residence and other sources for evidence of past instability, particularly during periods of heavy rainfall
  7. If absence of recent or current landslide activity is confirmed, prepare report confirming this with appropriate documentation (map and representative sections)
  8. If ground hazard identified, follow Steps 7 to 15 of Zone 1 procedures

Low Risk

Category 2 Geo-Professional

Does not require engineering geological and geotechnical assessment

  1. Site to be inspected by competent Category 2 Geo-Professional
  2. Provide written confirmation of inspection and judgement that there is no landslide hazard at the site

Category 3 Geo-Professional

Very Low Risk
No requirement for Engineering Geology or Geo-Professional expertise

  1. Site to be inspected by competent category 3 person

Definitions in this section

City plan

Council

Design

Development evaluation report

Geotechnical completion report

Geo-professional

Ground

IDC

Infrastructure

Person

 

 

Tauranga City Council, Private Bag 12022, Tauranga, 3143, New Zealand  |  Terms of use

Back To Top