Detailed design is based on survey work. Ground surveys help form a ‘digital terrain model’ that is used in the final (detailed) design of the project.
Typical features recorded by the surveyors included services (phone, electricity, water, and sewer), property boundaries, nearby property improvements, vegetation (in particular the location of any threatened species), drainage paths, creeks, high flood marks, railway details, heritage details, existing highway and side roads, extent of wetlands etc. The survey data collected also provides important information for studies such as noise modelling, flooding and hydrology.
Further surveys and assessments are also carried out for the detailed environmental work prior to construction, and form the basis of the Environmental Management Plan.
Geotechnical investigations verify ground conditions and identify materials likely to be encountered during construction along the highway route.
Information is collected using a range of techniques (e.g. test pits, bores, seismic etc) and is used to assist in determining:
- Ground moisture conditions.
- Types, strengths and quantities of materials suitable for
excavation.
- The extent of soft soils, acid sulphate soils and contaminated
soils (hydrocarbon, agricultural).
- Foundation conditions for bridges and retaining walls.
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