NSW government-owned water services corporation Sydney Water will replace its existing supervisory control and data acquisition (SCADA) infrastructure at five water filtration plants during the next twelve months.

SCADA systems are used by Sydney Water to monitor and control the operation of water and wastewater treatment plants. They typically comprise instrumentation, control equipment, local and wide-area communication networks, programmable logic controllers (PLCs), and workstations and servers.

An interface is provided to integrate local SCADA system data into Sydney Water's integrated instrumentation, control, automation and telemetry system (IICATS).

Sydney Water's Cascade and Orchard Hills sites comprise a cluster of five water filtration plants (WFPs) in the western Sydney suburbs of Nepean, Warragamba, and North Richmond.

The Cascade and Orchard Hills WFPs, which are linked, were both commissioned in late 1993 and by Sydney Water's own admission its PLC and SCADA networks "have insufficient redundancy or capacity to add new process sequences".

"Also the existing PLCs are obsolete and procurement of spares is a major problem," according to one tender document.

Recent projects at both WFPs have increased the loading and functionality on the existing SCADA systems resulting in "slow screen updates". Consequently, the slow network speed has "created major delays" in diagnosing and fixing problems at WFPs.

"The existing network architecture is of obsolete technology and is not compatible with proposed modern PLCs."

The Orchard Hills site contains 21 PLCs throughout the plant. The SCADA system consists of one primary server and another secondary server providing control and monitoring of both the WFP and pumping station.

The Cascade WFP contains 16 PLCs and the SCADA system consists of one global server and another local server to control the WFP and the clear water pumping and delivery system.

A key driving factor for the upgrade is the increasing difficulty of support for existing PLCs, according to Sydney Water.

While not classically in the domain of IT, SCADA systems have become more IP-based in recent years making the technology a better fit into the data networking practice of a large enterprise.

A Sydney Water spokesperson declined to reveal the cost of the project, only saying it will be "several million" dollars.

"It will replace the existing system and no new processes are being added," the spokesperson said. "New instruments will be installed as the PLCs are out of date and no longer supported. In some cases they will be retrofitted, and a new LAN will be put in place."

The spokesperson told Computerworld recent lightning strikes have damaged some PLCs which, due to their age, are difficult to find replacement parts for.

The project will involve the upgrade of existing SCADA systems to Serck SCX6 SCADA, replacement of all existing PLCs and SCADA LAN networks, retainment of existing motor control centres, provision of additional instrumentation, provision of a full set of new electrical and SCADA drawings, installation of new PCs with SCX6 SCADA software to enable to control and monitor the Cascade and Orchard Hills WFP's from remote sites.