The "stump" A New Dimension In Dredging

ABSTRACT Hydraulic dredging equipments has changed little since Liddy, Von Schmidt and others started pumping dredged spoil about one hundred years ago. The basic elements of the hydraulic dredge are simply a barge or ship's hull, a dredge pump, power plants, maneuvering spuds and lines or engine propulsion, suction line (cutterhead) and ladder, and a discharge line. In spite of various refinements and innovations, hydraulic dredges are about the same as they were when the Panama Canal was built. Approximately one hundred hydraulic dredges are manufactured each year. Their sizes vary from the small six-inch portables to the 36"- 42" superdredges. Modern dredges have more compact power plants, more efficiently designed pumping systems, swell compensating equipment and space-age electronic equipment for controls and navigation - but this is not enough. Although both the venerable old dredges and the modern dredges have tremendous capacity and are the most efficient earth-moving equipment in the world, they are not capable of meeting the great bulk of today's dredging requirements. Today's requirements include working in the pen sea to cut, clear, and deepen channels and harbors to depths of eighty feet or more. There is a recognized need for dredges to work offshore in ocean mining projects, in land reclamation, and on beach nourishment projects. Planners and engineers have designed offshore nuclear plants, airports, artificial islands, and deep-water ports, taking for granted that the dredging industry was keeping abreast of the times and their requirements and that costs would be nominal. The truth is that there are not enough dredges capable of doing this type of work, and the price is not nominal. It is too expensive. These facts will no doubt be brought out in the National Dredge Study now being completed for Congress by the Arthur D. Little Company. In the past dredge owners have been able to modify and make innovations to their existing fleet, incorporating the best available technology, in order to tackle various types of projects, most of which were in safe, sheltered waters. A dredge owner therefore has not only a large initial investment in the dredge, but the additional cost of upkeep and renovation. In his own best interest he must operate, maintain, and modify that dredge as long as he can keep it operational. However, many of these dredges are becoming really obsolete, and their owners cannot compete with operators of modern specialized equipment. Both modern and specialized dredges have profit and performance advantages over the old dredges, which have consequently remained idle. Inflated costs and high interest rates make it too costly to upgrade many of the old dredges to competitive levels. The technology in dredge design that is evolving allows the dredge longer wearing time on replaceable parts and easier and faster servicing. This allows a dredge to work continuously for a greater percentage of the time and to use smaller crews, thus reducing project costs and increasing profits and competition.