Near Shore Construction –
Shallow Water Fun, Deep Trouble for Some
13 April 2011 Perth Branch Evening Meeting
Chairman Ben Witton, Project Engineer, Cal Dive International (Australia) Pty Ltd
Sponsored by Cal Dive International (Australia) Pty Ltd
Overview
Near shore construction has seen cross pollination of offshore and onshore construction methods. This has resulted in a multitude of options for bringing product ashore.
With the growth in the regional LNG market these construction methods are particularly applicable to many projects in the region. These work scopes often provide the interface between the onshore and offshore contractor, with the resulting schedule clashes and different contract milestones providing a special challenge for the contractor in the middle. These presentations will provide an overview of some of the factors to be considered when planning and executing a near shore construction project.
Presentations
Survey Techniques in the Near Shore Environment
Bill Russell-Cargill, Survey and Inspection Manager, DOF Subsea Australia Pty Ltd
The presentation discussed the surveying techniques used in shallow water for oil and gas projects where survey information is required for the optimisation of engineering design and construction support. Bill discussed some of the challenges that face hydrographic surveyors when undertaking positioning and mapping operations in shallow water. The shallow marine environment with its rapidly changing complex horizontal and vertical stratification creates the need for state-of-the art survey data to be acquired in areas where it is often impossible to go back and resample. The usefulness of information for analysis, modelling and design hinges on the quality of all original data due to the dynamic nature of the areas being investigated. Similarly precise and accurate data is required for controlling construction activities in these zones. These requirements make it essential that survey techniques are continually developed to obtain the high quality data that is needed. The transition from sea to land represents the 'twilight zone' for acoustic systems to work effectively. These areas are not easy to survey economically and a number of novel approaches have to be adopted to achieve the required results. Examples of the problems that are often encountered and some of the solutions used were discussed along with case studies.
Diving in the Near Shore Environment
Peter Evans, General Manager, Cal Dive International (Australia) Pty Ltd
Peter presented on the challenges of diving in the near shore zone highlighting issues that are particular to the this area, such as local currents, diving in areas of poor visibility as well as consideration of the sort of vessels / practices most suitable for construction activities near the shore line. The presentation drew on lessons learnt from recent projects conducted along the North West Shelf.