“The basic rule of dredging is that you don’t want to over- or under-dredge,” explains Adam Whitcome, operations manager for CGC Dredging, the firm tasked with dredging the harbour entrance of Port Geographe in Busselton, WA. “Over-dredging means you spent time and money, like burning diesel, that you didn’t need to; and if you under-dredge your floor may not meet design depth specification. You really need to be precise and efficient in your work and also have the ability to make adjustments according to design parameters.”
Popular Sorrento beach had been losing its sand! As summer approached, Sandpiper Dredging utilised hydrographic survey technology to replenish the beach.
Shifting sands in Port Phillip have left the front beach at Victoria’s popular destination of Sorrento beach lacking sand. As summer approached, the Mornington Peninsula Shire and Australian Department of Environment and Primary Industries (DEPI) decided to replenish the beach by dredging a near shore sandbank.
DEPI awarded the contract to Sandpiper Dredging due to their history of minimising environmental impact. Sandpiper has a decade of dredging experience and builds their own precision dredgers in Tweed Heads NSW.
The contract specified the dredge ground extent and the minimum Australian Height Datum (AHD) height Sandpiper could dredge. To achieve the job specifications and efficient operation of their dredge, Sandpiper knew they needed hydrographic survey technology on board. They turned to their local Trimble distributor, SITECH Construction Systems, for advice.
Consultation with SITECH Construction Systems established three key equipment requirements in order to precisely position in 3D the cutter suction head on the dredge frame in real time.
Trimble® SPS461 GPS Heading and Positioning Receiver—a robust and accurate position and heading system all in one integrated GPS receiver designed for easy and fast installation
Inclinometer to measure the angle of the cutter head frame
Trimble HYDROpro™ Dredge software to display and log seabed levels—an easy to use software solution that can be configured for a wide range of dredgers.
To obtain precise 3D positions from the SPS461 receiver GPS corrections were streamed in, via cellular Internet, from the Victorian Government’s CORS (Continually Operating Reference System). Position and heading from the SPS461 receiver were interfaced into HYDROpro Construction software to display dredge position. The inclinometer mounted on the dredge frame also interfaced with HYDROpro and allowed the AHD height of the cutter head to be displayed. The dredge position displayed in HYDROpro allowed operators to stay within the dredge grounds and ensure no over dredging occurred. The HYDROpro software was the central hub in the wheel house displaying and logging dredge positions and the AHD height of the dredge head. The easy-to-use HYDROpro software allowed the dredge operator to focus on controlling the dredge rather than understanding where to dredge. Using GPS and AUSGeoid09 removed the need for considering tide data because HYDROpro displayed the AHD height. The logged data could be delivered to the client as an as-built drawing.
Daniel Fristch,owner of Sandpiper, said “Building our own dredging systems is something we’re really proud of. In building them we can apply our years of experience to ensure we have the right machinery we need to carry out our clients’ work”.
“Working with SITECH Construction Systems is a true partnership because they are as focused on the needs of the customer as we are. After speaking about the challenges we had been facing, SITECH came back with the solution of the Trimble HYDROpro system which meant we could dredge in exactly the right place and maintain coverage, all the while protecting the environment of the beach.”