Ward & Burke were awarded a contract to construct 4 No. concrete caissons and 225m of 3000mm OD microtunnel for the Burbrook Trunk Sewer Project.
- Tunnel No.1 was 175m in length crossing underneath 22 No. live rail lines.
- Tunnel 2 was 50m in length crossing under 2 No. live rail lines.
- Both crossings were completed with 7m+/- cover, (from ground level to crown of pipe) with negligible settlement to the rail lines, the alert level for settlement was 5mm, which was not reached during or after tunnelling was completed. Both tunnels were tied-in to the existing storm pipe lines and permanent manholes constructed in-situ.
- An original attempt to cross rail lines using open face tunnelling equipment and dewatering failed a number of years ago due to geotechnical conditions, with basements flooding in the interim. The contract was redesigned and specified as microtunnelling 10 years later to overcome the ground conditions.