Design and Construction of Floating Concrete Pontoons for the Vesuvius to Crofton Ferry Terminals


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Title: Design and Construction of Floating Concrete Pontoons for the Vesuvius to Crofton Ferry Terminals

Author(s): H. R. Woodhead

Publication: Special Publication

Volume: 93


Appears on pages(s): 889-902

Keywords: concrete constuction; floating docks; pontoons; structural design

Date: 9/1/1986

The Vesuvius to Crofton ferry plies the waters of the Strait of Georgia between the east coast of Vancouver Island and the west coast of Saltspring Island. At each end a floating pontoon supports the seaward end of the loading ramp. Prior to 1978, the pontoons were constructed of timber and Styrofoam but they had become waterlogged and badly deteriorated. It was therefore decided to replace them with concrete pontoons to utilize the durability of the material. Tenders were called for the design and construction of the pontoons and Dillingham Construction was the successful bidder. The pontoons were built as hollow boxes without a bottom slab. The walls and top were constructed of high quality reinforced concrete and the inside was filled with closed cell polystyrene to provide the necessary flotation. During the design, care was taken to ensure that the resistance to sea water attack and impact loads was maximized. They were fabricated in the graving dock at Dillingham's yard in North Vancouver and towed out to the site. They have now been providing satisfactory service for over seven years with no signs of deterioration. This rather novel project has shown that floating concrete struc-tures can be built economically and require little maintenance.