Determining Integrity in 5,000 Feet of Water Following a Major Incident

Prior to the completion of installation of the Big Foot TLP, 9 of 16 pre-installed tendons fell to the seafloor. Seven of the tendon assemblies were reverse installed. Nine of the tendons lay on the seafloor with the lower connector assemblies remaining within the piles and receptacle device. A critical go forward decision was determination of reusability of the pile/receiver assemblies. The pile/receiver assemblies were located in over 5,000 feet of water. Novel technology application and deployment was needed to clear the site, inspect remaining components, determine integrity and adequacy. The decision was time bound as go-forward decisions relied on the outcome of the study. This paper outlines the fallen condition, development of criteria to assure adequacy, identification of technologies sufficient to determine adequacy, interpretation of the data, engineering assessment and final decisions. Initial clearing of site included removal of lower tendon sections and connectors without incurring damage to the pile assembly was required. Marinizing inspection tools, templates, etc. for both accuracy and repeatability was required. The novel and successful execution starting with "as is" condition through design, deployment and results will be highlighted. One key element was mapping the after-incident conditions to the design tolerances. Developing tools and operating procedures to assure measuring tolerances and repeatability required new methods and procedures that proved successful. For a first of kind and unique challenge, the importance of starting with first principles and initial acceptance criteria, identifying technologies and tools available to match, followed by selection of most likely to succeed in extending existing tools for success is illustrated.