WET News

MAY 2014 WET NEWS 15 The U Mole HammerHead HB100 pipe bursting rig in position in the pulling shaft 'Pipe-eating' augers well for Edinburgh pipeline work • Replacing a 300mm diameter sewer with a 600mm diameter pipe in Edinburgh soon turned into a challenge, with difficult site access putting equipment selection high on the agenda. 'Pipe-eat- ing' replacement became the technique of choice. TECHKNOW • A combined auger boring rig and pipe burst rig assembly was used to complete the 'pipe eating' replacement technique • The pipe-eating head was attached to the lead pipe of the jacking rig • A series of uplift pulling rods were passed through the existing pipe to connect the machines • A series of uplift pulling rods were passed through the existing pipe to connect the machines • The pulling force kept the pipe eating head remained on the same line MOANS & GROANS • Site access was difficult because of the close proximity of a canal and a railway line at one end and a special needs school at the other • The logistics were "nightmarish" because of the limits on equipment A difficult 'pipe eating' pro- ject was undertaken re- cently to replace a 300mm diameter sewer with a 600mm diameter pipe – the ex- isting sewer was under capacity for its present requirements and was causing flooding upstream. The project, for Scottish Water, with Pipeline Drillers as the spe- cialist contractor working for George Leslie, was located in Kingsknowe Crescent, Edin- burgh. The length of the section of pipe that needed to be replaced was 60m, with the existing pipe running at depths between 3.5m at one end and 6m at the other. Ground conditions comprised very stiff clay with boulders. The terrain also banked up and down along the full pipe length with the surface being mostly wooded, which added signifi- cantly to the access difficulties. The woods are also used by a special needs school under supervised access. Any works needing major surface access to the woods would have pre- vented use of the woods by the school for the duration of the project and for some time a'er to allow the grass and woodland to re-establish. Access to the site was diffi- cult with one end limited by the close proximity of a canal and a PROJECT SPECS • Replace a 300mm diameter sewer with a 600mm diameter pipe • Select appropriate trenchless technology THE VERDICT • The carbon footprint of the works was reduced because of the trenchless technology • The innovative use of the combined jacking and pipe bursting systems brought success to a very challenging situation railway line whilst at the other end was the school. Taking these factors into account it became obvious that only rela- tively small size construction equipment could be used to complete the works. At the planning stage various options for the completion of the works were considered including Open Cut, Horizontal Directional Drilling (HDD), Standard Pipe Bursting and Auger Boring The Open Cut method was not an option as the location and route of the pipeline was more than 6m deep for part of its length and would have required the removal of trees. Also, there was potential for massive local disruption and environmental damage that such an operation would create. Overall, this meant that the cost of the open cut option was also highly prohibitive. HDD was also a non-starter because of the limited access and footprint at the installation site, which meant that there was little space for an HDD rig and its support equipment. Stand- ard Pipe Bursting, whilst some- what similar to the technique ultimately used, was not suita- ble because of the limited size of the equipment that could physi- cally be used on site. ONSITE ASSET MANAGEMENT Confined access on site led to significant logistical difficulties throughout the project The pipe eating head attached to the pulling rods from the U Mole burster

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