Reference Specifications for Civil Engineering Work 2001

5.tRENCH technologies

Refer Annexure.

Existing surfaces

Saw cutting: Before excavating trenches, saw cut existing concrete and bituminous surfaces to provide a straight even joint during the restoration.

In road carriageway, saw cut to requirements of Standard Drawing BSD-2042.

In road verge, footpaths and bikeways, saw cut to requirements of Standard Drawing BSD-2043.

Any other locations, saw cut 150 mm clear of the trench walls.

Position saw cut to coincide with any grooved pattern line or contraction joint or expansion joint in concrete paving, if the saw cutting is undertaken within 600 mm of these elements.

Unit paving: Lift and store unit paving for later reinstatement.

Excavation

Alignment: Excavate for underground services to the required lines, levels and grades. Generally make the trenches straight between maintenance access points, inspection points and junctions, with vertical sides and uniform grades.

Timing: In new construction projects, excavate trench before any paving or topsoiling and grassing operations, unless approved otherwise by the Superintendent.

Trench widths

Keep trench widths to the minimum consistent with the laying and bedding of the relevant service, construction of maintenance access points and pits, and compaction of the trench backfill. For drainage trenches, comply with Standard Drawing BSD-8011.

Trench depths

Excavate as required to achieve the following minimum cover over the top of the conduit or service, where the service is not placed in a conduit. If the relevant Service Authority specifies minimum cover, ensure that the minimum cover will be maintained during future pavement rehabilitation – allow for 600 mm to be removed on major roads and 250 mm on minor roads as part of future pavement rehabilitation.