UEA Trenchless completed a 150 metre sewer upgrade for Bolte Civil as part of the Hunter Water Williamtown Wastewater Transfer Scheme (WWTS). The project consisted of three road crossings, including a 110 metre crossing of the Pacific Highway and adjacent wetlands.
The WWTS will extend the current wastewater system to cater for existing and new development in the Williamtown and Tomago areas. The WWTS includes the construction of a wastewater pumping station within the new Williamtown Aerospace Centre and a second wastewater pumping station in Hunter Water owned land off Masonite Road, Tomago.
UEA used pilot tube microtunneling methods combined with traditional auger boring to provide a flexible solution to cross both major roadways and a creek whilst working in environmentally sensitive zones with a very high water table.
The first two drives, both 40 meters in length, were driven across local roads using a GBM laser pilot system, followed by a traditional auger borer. This method of 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 pilot tube microtunneling, 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.