UEA Trenchless recently completed a 600mm utility tunneling project for Bolte Civil through environmentally sensitive wetlands on the Tomago to Raymond Terrace sewer rising main. The tunneling project consisted of three road crossings, including a 110m crossing of the Pacific Highway and adjacent wetlands as part of a package of under bores in the Newcastle area. Ground conditions presented hard packed sand through to saturated muds with a high water table.
The first two drives, both 40 meters in length, were driven across local roads using a GBM laser pilot system, which was followed by a traditional auger borer. This method, which is also known as pilot tube microtunneling, ensured accuracy of line and level and the auger borer provided a simple and efficient method of inserting the 600mm steel enveloper pipe. The 450mm PE carrier pipe was then inserted and grouted into position.
The third drive of 110 meters was also completed using the same pilot tube microtunneling method, ensuring accurate line and level for the enveloper pipe. The 600mm steel enveloper pipe was installed using a combination of auger boring under the Pacific Highway; and then switching to a Grundoram® hammer to ensure safe passage beneath the environmentally sensitive wetlands and a flowing creek with no surface disturbance. With less than 600mm of cover the enveloper was successfully installed and the 450mm PE carrier pipe inserted and grouted into position.
Although the location of the under bores presented several challenges and environmental restrictions the flexibility of the laser guided system paired with the auger borer and Grundoram® hammer ensured accurate and timely delivery of the project.
Related Article: UEA Uses Pilot Tube Microtunneling to Deliver Pin Point Accuracy.
Image Caption: Inserting the GBM pilot tubes.