The only specialised marine publication in Oceania that focuses on the maritime industry, from super yachts to small craft to large commercial ships, including coastal shipping, tugs, tow boats, barges, ferries, tourist, sport-fishing craft
Issue link: https://viewer.e-digitaleditions.com/i/131029
NEW GENERATION ALLOY DUMP BARGE BY KEITH INGRAM T he recent launching and delivery of a purpose built 1200 gross tonne spoil dump barge has certainly turned some heads. Traditionally these dumb barges have been made of steel with mechanical bomb doors, and because of the nature of their work end up looking like a bucket of rust and an ugly dung heap in a very short time. Because they look like a dog's breakfast throughout their working lives they get abused, mistreated and generally unloved. The mechanical doors and operating systems on these dump barges slowly deteriorated, it was not uncommon that a leaky barge from the time of departure to the dump site could lose half its load in transit. Not so now, with the strict Resource Management Act and monitoring requirements required by law before any dumping at sea – a marine permit is issued. The dredging of our ports and sheltered waterways for commercial use has been a requirement since we developed safe havens for our ships and vessels. Be it a working port, local wharves or a marina, most require some form of maintenance dredging from time to time and Auckland's Pine Harbour marina is no different. Pine Harbour was dug out of low lands accessed by a long dredged channel leading to the deeper water of the Tamaki Strait on the approaches to Auckland's harbour. Surrounded The two barge sections as they emerge from the shed 12 Professional Skipper May/June 2013 by mud flats, the need for annual maintenance dredging is just part of doing business for Pine Harbour and many other marinas in Auckland. Unfortunately the days when we had dredges and hopper barges on standby are long gone. All too often when a marina company is planning its dredging programme, they are finding out that the required tugs or large barges and diggers are in Australia working on lucrative mining infrastructure projects and will not be back in New Zealand for some time. "Time and tide" waits for no man and with each flood of the tide a bit more silt is deposited into our draft sensitive waterways, a creeping enemy from mother nature. Today most dredging is done by converted long reach excavator diggers mounted on a dumb barge from where it can operate and either dump into a small hopper on the barge or operate alongside a larger dump barge when in open water. In Pine Harbour's case, the dredging digger and spoil transfer barge is operated by Coastal Resources Limited and while the transfer pond can hold some hundred tonnes of wet spoil on a good day with the digger on board, it is not suitable or economic to face the 60nm tow to the spoil grounds outside the 12 mile territorial limit beyond Great Barrier Island. Gone are the days when one could dump dredged spoil in the Waitemata Harbour or Hauraki Gulf. Faced with this pressing problem, the decision was made by Coastal Resources to commission a purpose built 40 metre split hopper barge with a capacity of some 1000 tonnes to aid in disposing maintenance dredgings for various marinas. The brief was for a vessel of a nominal two metre draft so it could be loaded within the sheltered marina basin itself, but still large enough for the economical trip to the disposal ground. Most marinas give a depth of two to three metres at chart datum so ongoing maintenance costs are a critical factor in the management of any marina. There has always been a good supply of smaller tugs and digger barges from the local workboat sector to do this sort of confined space work and while maintenance dredging is by its nature regular, there has not been a reliable supply of the right