Hindmarsh Island North Rising Main
HDS Australia was engaged by the Alexandrina Council to design a pump station and rising main to transfer sewage from a new land development on Hindmarsh Island and inject it into the Goolwa Community Wastewater Management System network. The construction contract was awarded to B J Jarrad Pty Ltd and construction is now complete. Unique to this project was the major challenge of pumping sewage across the River Murray.
After extensive investigations, including, liaison with Council and other stake holders (Department of Planning, Transport and Infrastructure, Murray Darling Basin Authority, Ngarrindjeri Regional Authority, EPA and Department of Health) the decision was made to install the rising main across the river by attaching it to the underside of the Hindmarsh Island Bridge. Underboring of the River Murray was eventually discarded as an option because of the residual risk inherent in installing a pressure main under the river.
Herriot Consulting provided the engineering details of the new land development and the design process required close collaboration between HDS Australia, Alexandrina Council along with the engagement of Bullock and Partners to design the structural elements for the pipework under the bridge. Interesting engineering solutions needed to be addressed regarding;
- preventing slack flow in the downside portion of the rising main when pumping stopped,
- determining the head required (from Walbridge & Gilbert’s EPANet model of the Goolwa network) to ensure injection of the sewerage from the development into the existing rising main,
- overcoming ground water issues during construction of the six metre deep pump station on Hindmarsh Island, and
- sourcing a suitable air valve to be accommodated and maintained in a restricted area on the rising main under the bridge deck.
The project required, the installation of a standard PVC rising main on both sides of the River Murray where adequate sediment control measures within the flood plain were installed to ensure that the construction activities had no impact on the river. Construction of the pump station on Hindmarsh Island. Under-boring of the Steam Ranger Rail Track was required at three locations and the major challenge involved attaching the ductile iron rising main under the bridge.