Sunwater Scrivener Dam

Background:

Scrivener Dam is a concrete gravity dam on the Molonglo River, impounding Lake Burley Griffin in the Centre of Canberra ACT. The dam was completed in 1963.

Lady Denman Drive, one of the main road ways in the area, is incorporated into the dam structure as an overhead bridge directly above the proposed works. The dam office complex is located just off Lady Denman Drive on the opposite bank of the river to the National Aquarium.

The main features of Scrivener Dam are:

• 5 Spillway gates
• 3 Sluice gates
• Emergency generator
• Office complex

The dam is operated to maintain a uniform water level (within +/- 100 mm) in Lake Burley Griffin. The Storage is ornamental, not operational in nature; however, it can provide some flood attenuation during flood events in the Molonglo Catchment. Scrivener Dam is a concrete gravity dam, which is designed to hold back 33 million cubic metres of
water of the Molonglo River within Lake Burley Griffin. The spillway is controlled by five German designed-and-built fish-belly flap gates (floodgates), each measuring 30.5 metre wide. The dam also includes an outlet works containing three sluice valves for environmental release.

The purpose of the project was to upgrade the electrical and control systems for the Flap Gates and Sluice Valves, to meet current industry standards, improve safety for Operators and maintenance staff, and improve the functionality and reliability of these systems.

Preliminary Works:

CEQ were appointed main contractor to SunWater, with Wagtec providing PLC and SCADA programming. The existing switchboards were traced out and to verify old drawings found onsite. There had been a number of wiring modifications over the years to alter operation, and these needed to be captured to ensure correct operation of the site equipment after the upgrade.

Control System:

The existing hard wired relay logic was replaced with the following Schneider equipment:

• Main PLC controller (Modicon M340)
• SCADA / HMI (CitectSCADA touch screen display)
• Five flap gate RIO units
• Three sluice valve RIO units
• Ethernet switches
• Modbus TCP/RTU gateway

The main PLC and ancilliaries is located at ground level, with fiber communications down the the gallery underneath the dam wall.

Installation:

As the dam could not be offline for an extended amount of time each piece of plant equipment was decommissioned and upgraded independantly. This provided challenges as the old and new control system needed to work side by side for the duration of the cutover.

Full testing of the new Sluice Valve and Flap Gate boards was was witnessed by Scrivener Dam staff before being placed into operation.