HORIZONTAL DIRECTIONAL DRILLING (HDD)

DM Civil has undertaken some of the largest diameter and longest HDD shots for the Water Corporation of WA.

In 2002, DM Civil constructed the 13.5km DN375 Eaton to Kemerton waste water pressure main. The pipeline was largely PVC pipe except for the crossings of the Collie & Brunswick Rivers. These two river crossings were constructed underneath the rivers via 400 metre and 600 metre directional drilling respectively.

DN150 pilot rods were drilled into position utilising induced magnetic field to track the steering head. Once the pilot rods were in place, the hole was reamed out using incrementally increasing reaming tool sizes. Once the last DN600 reamer had completed the hole this was attached to a pre-welded, strung and tested DN400 PN 20 polyethylene pipe and pulled into position in a continuous pull-back operation.

The Collie River crossing was simple, standard catenary shaped drill and pull back. The 600 metre Collie River Crossing was more complex and comprised of multiple curvatures requiring two horizontal and three vertical changes in direction.

In 2013, DM Civil delivered an alternative construction methodology utilising 410 metres of DN200 PE HDD throughout the township as a part of Dwellingup’s new water supply scheme. This had considerable, safety, environmental and stakeholder benefits to open excavation methodology.

In 2014 DM Civil won the contract for the construction of the Yanchep DN225 – DN1200 gravity sewers via trenchless technology methods and also the 7.5 kilometre DN450 PE waste water pressure main, including construction of 1,000 metres of DN450 PN20 via HDD methodology in pinnacle limestone ground. This was done in two drill shots, one at 600 metres and the other at 400 metres. The 400 metre HDD contained double curvature design. The HDD section had considerable design, construction, stakeholder and operational benefits for the Water Corporation.

This technique is a very cost effective methodology used for bores under roads, railway lines, services and structures, in wet or dry ground conditions, where line, level and grade are not critical and long distances are required to be covered.