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GEOLOGISTS

Properly qualified or experienced geologists and related professionals (such as engineering geologists and geotechnical engineers) provide geotechnical advice for property development.

Contact us for advice in relation to these matters.

Geotechnical reports assess whether a given parcel of land is capable of supporting an intended development. Issues which normally require attention include surface drainage, flood potential, tunnel erosion, foundation conditions for houses ("soil tests"), wastewater, slope stability (eg landslips or unstable ground),

Some local councils require geotechnical reports for land subdivisions of any size. Most councils require site-specific soil tests for new houses and extensions. Some councils require site assessments for domestic wastewater, and some have a list of potentially contaminated land which, until investigated, might not obtain development approval.

There may be other issues - such as Aboriginal or European cultural heritage caveats, mining leases and exploration licences, or other environmental restrictions - which may affect land use.

Some lawyers will demand this information before property is transferred. Some lending authorities will not provide finance until satisfactory geotechnical reports are available.

MORE ON GEOLOGISTS

Geologists are often called upon to satisfy the following Council requirement:

When is Land Instability Assessment Required

Land instability assessment and Geotechnical reporting is required for all development applications (particularly subdivision) which are on land at or above the threshold slope angle.
or which shows evidence of land instability, terracetting rumpled topography, bowed tee trunks, trees angled downhill, damaged or cracked existing structures leg, cracking in masonry walls, around window frames, footpaths, road pavements, elc.), cracks in the ground, soft ground, are all evidence of possible land instability.

Land instability assessment should ideally be obtained prior to a planning permit being issued. This is particularity important in the case of subdivision (except boundary adjustments) because of the need to ensure that the land is capable of further development. In respect of developments other than subdivision, it is advisable to obtain assessment at the earliest possible opportunity (preferably before planning approval is given), but definitely prior to a building permit being issued.

How to assess whether development applications require Land Instability Assessment?

Step 1-3 are relevant to all forms of development.

Steps should be followed in Sequence:

Step 1. Determine the slope of the site. This can be done by any of the following methods:

A. Using a clinometer or similar instrument. B. Determining steepness of slope from map contours. {i.e., from a map, measure the horizontal distance of the entire Map on which the project site is located (eg, 100 metres) and then determine the height difference by subtracting the lower contour from the higher.

C. Estimating vertical fall within a given horizontal distance (eg, land falls 1 metre vertically in 5 metres horizontally).

Step 2. Determine the Geology Type.

This can be done by consulting relevant geology maps, or by identifying whether the site has sandy or clay soil. If the site has sandy soil, then it could be either tertiary Sediments, Permian Sediments, Triassic Sediments, Quaternary Sediments geology types. If the site has clay soil, then it could be Jurassic Dolerite or Tertiary Sediments geology types.

Step 3. Compare the slope of the land with the relevant Threshold Slope Angle for the relevant n geological type indicated in Table 1. (available upon request)

If the slope of the subject site is at or above the threshold, and/or there is no physical evidence on the site or surrounding land of instability, no further, more detailed investigation is required.

If the slope of the subject site is at or above the threshold, and/or there is physical evidence or the site, or surrounding area, of instability (see “When is Land Instability Assessment Required" for examples evidence of land instability) then further, more detailed investigation is required.

What investigations are required if land instability assessment is needed, and what matters will have to be considered?

If further more detailed investigation is required (as determined in Step 3, above) then an adequate Geotechnical report will need to be submitted to the Council. This report will need to address all potential hazards to the satisfaction of Council prior to the relevant approvals being issued,

Who should do Land Instability Assessments

Land Instability (Geotechnical) assessment should be undertaken by persons with appropriate training, knowledge and skill in assessing and quantifying land instability risk. An engineering geologist or Geotechnical engineer, who carry the appropriate professional indemnity insurance for Geotechnical investigation purposes, are probably the most qualified to undertake such investigations.

When are Geotechnical reports required?

A Geotechnical report can be required for all subdivisions with the exception of boundary adjustments which do not create a site intended for development. This requirement may be modified when Council receives regional Geotechnical information.

Who can prepare Geotechnical reports?

The report is to be prepared by a suitably qualified engineering geologist or professional Geotechnical . That is, a person who has recognised qualifications and experience in the Geotechnical field and has specific expertise in landslip risk assessment and quantification.

What is to be covered by a Geotechnical report?

The report is to include information about the site and the surrounding area which includes:

geology;
geomorphology and slope conditions:
geological history of the site relative to landslip;
surface drainage sub-surface and groundwater conditions,
soil/bedrock conditions.
soil classification relative to AS2870;
changes to natural surfaces, and;
distribution of vegetation.

it is also expected that the report will contain an explanation of the research undertaken including details of the published geological reports and maps which have been examined and an explanation of the findings.

Finally, it is essential that the report quantifies the level of risk and refers to the specific proposal under consideration Statements are to be made about the degree of risk which may result from the possible development and/uses which could be approved on each of the proposed lots. Where risk reduction measures are suggested these are to be written in a manner which can be translated into conditions of approval.

Independent Review

If the conclusions or recommendations of a report are complex or unclear, Council may require a review of the report by an independent engineering geologist or Geotechnical Engineer.

Who Assesses On-site Effluent Disposal Capability of Lots in Unsewered Area?

Council's Environmental Health Program carries out assessment of proposed lots in unsewered areas to determine their ability to dispose of effluent within lot boundaries.

SIMPLY:
Council has the power to ask for a report when any development application is lodged. glenorchy City Council always ask for a report. They can be expensive but usually represent a clarification for Council and an easier path through the approval process.

HOW WE ASSIST:
We are closely aligned with geotechnical experts and can advise on the best course of action for your application.