CWMS Strathalbyn Wastewater Treatment Process Upgrades (Stage 2)

⁠⁠⁠Alexandrina Council (the Council) invites tenders from Tenderers for the provision of CWMS Strathalbyn Wastewater Treatment Process Upgrades (Stage 2) (the Services).

The township of Strathalbyn is serviced by a Community Wastewater Management System (CWMS), which involves wastewater collection, treatment and reuse/disposal. The scheme is primarily a Septic Tank Effluent Disposal Scheme (STEDS), meaning most connections have a septic tank for primary treatment. The township also has a number of full sewer connections. The CWMS is owned and operated by Alexandrina Council (Council).

Effluent generated within the township gravitates through a network of gravity drains into pump stations within the township, and is pumped through a network of rising mains to a sequence batch reactor (SBR) wastewater treatment plant (WWTP) near the intersection of Michelmore Road and Greenway Road. The SBR plant currently operates at 500 – 700 kL/day, and has a capacity of 1,500 kL/day. Based on field observations and a water balance assessment, the existing 120 ML polyethylene-lined storage lagoon at the plant has been found to have inadequate capacity to balance the scheme’s annual water storage variation.

Stage One of the project involved the construction of a new 110 ML storage lagoon at the plant to provide additional balancing storage.

Stage Two of the project involves a range of other upgrades to address some deficiencies with the existing plant and improve operation.

The Services relates specifically to Stage Two: Strathalbyn, Wastewater Treatment Plant and Irrigation Pump Station Package.

Stage two WWTP and Irrigation Pump Station Package includes:

• Construction of new irrigation pump station upon the batter of the 110 ML storage lagoon;
• Construction of 100 kL chlorine contact tank between the SBR plant decant line and the outlet drains to the storage lagoons;
• Modifications to the transfer mains from the balance tank;
• Modifications to the WWTP’s gaseous chlorination dosing system;
• Construction of a platform and a wastewater screen on the inlet to the WWTP’s balance tank, including installation of a wash pump;
• Realignment of various pipework in the WWTP;
• Construction of an offtake line to the existing chlorine dosing water storage tank, containing a filter, actuated isolation valve and a pressure sustaining valve;
• Installation of actuated gate valve on the existing rising main to the Ness irrigation site;
• Construction of an inlet manifold on the existing low level outlet pipes from the existing 120 ML, including a new floating suction inlet;
• Decommissioning of the existing irrigation pump station and modifications to internal pipework at the invert of the pit to connect in to the new irrigation pump station inlet pipework;
• Installation of hydrostatic level sensors on existing 120 ML lagoon and new 110 ML Lagoon; and,
• Testing and commissioning.

Council’s aims appoint a single contractor for the Civil works. The Electrical design and upgrades will be carried out by Councils CWMS Management team and selected Electrical Contractors;

This will be an exclusive contract to deliver services