Reference Document - RAL25/0020 & OPW25/0194 (As Published)

    About this Report
                                                                                             October 2024



Introduction                                               changes. They may not be the same at
These notes have been provided to amplify                  the time of construction as are indicated
Douglas’ report in regard to classification                in the report; and
methods, field procedures and the comments
section. Not all are necessarily relevant to all      •    The use of water or mud as a drilling fluid
reports.                                                   will mask any groundwater inflow. Water
Douglas’ reports are based on information                  has to be blown out of the hole and
gained from limited subsurface excavations                 drilling mud must first be washed out of
and sampling, supplemented by knowledge of                 the hole if water measurements are to be
local geology and experience. For this reason,             made.
they must be regarded as interpretive rather
than factual documents, limited to some               More reliable measurements can be made by
extent by the scope of information on which           installing standpipes which are read at
they rely.                                            intervals over several days, or perhaps weeks
                                                      for low permeability soils. Piezometers, sealed
Copyright                                             in a particular stratum, may be advisable in low
This report is the property of Douglas Partners       permeability soils or where there may be
Pty Ltd. The report may only be used for the          interference from a perched water table.
purpose for which it was commissioned and in
accordance with the Engagement Terms for              Reports
the commission supplied at the time of                The report has been prepared by qualified
proposal. Unauthorised use of this report in          personnel, is based on the information
any form whatsoever is prohibited.                    obtained from field and laboratory testing, and
                                                      has been undertaken to current engineering
Borehole and Test Pit Logs                            standards of interpretation and analysis.
The borehole and test pit logs presented in this      Where the report has been prepared for a
report are an engineering and/or geological           specific design proposal, the information and
interpretation of the subsurface conditions,          interpretation may not be relevant if the
and their reliability will depend to some extent      design proposal is changed. If this happens,
on frequency of sampling and the method of            Douglas will be pleased to review the report
drilling or excavation.       Ideally, continuous     and the sufficiency of the investigation work.
undisturbed sampling or core drilling will
provide the most reliable assessment, but this        Every care is taken with the report as it relates
is not always practicable or possible to justify      to interpretation of subsurface conditions,
on economic grounds.            In any case the       discussion of geotechnical and environmental
boreholes and test pits represent only a very         aspects,     and     recommendations           or
small sample of the total subsurface profile.         suggestions for design and construction.
                                                      However, Douglas cannot always anticipate or
Interpretation of the information and its             assume responsibility for:
application to design and construction should
therefore take into account the spacing of            •    Unexpected     variations  in    ground
boreholes or pits, the frequency of sampling,              conditions. The potential for this will
and the possibility of other than 'straight line'
                                                           depend partly on borehole or pit spacing
variations between the test locations.
                                                           and sampling frequency;
Groundwater
Where groundwater levels are measured in              •    Changes in policy or interpretations of
boreholes there are several potential                      policy by statutory authorities; or
problems, namely:
                                                      •    The actions of contractors responding to
•       In low permeability soils groundwater              commercial pressures.
        may enter the hole very slowly or perhaps     If these occur, Douglas will be pleased to assist
        not at all during the time the hole is left   with investigations or advice to resolve the
        open;                                         matter.

•       A localised, perched water table may lead
        to an erroneous indication of the true
        water table;

•       Water table levels will vary from time to
        time with seasons or recent weather


    1 of 2                          www.douglaspartners.com.au