ABSTRACT 1.ENGINEERING APPROACH These trials were meant to demonstrate the validity of the approach to the environ mental data acquisition, processing, assessment and to engineering procedures in very deep waters. We would like to deal here with design aspects worth discussing either for their innovating approach or for the complex ity of the problems involved, such as: -theoretical preparation;selection of the route through morphologically irregular areas where it is impractical or even impossible to modify the environment;study of the data acquisition system and its specific components;procedures for selection and analysis of data gathered during the trials. 2. PIPE-LAYING EXPERIENCES Trials were intended to experiment and validate procedures, techniques and new solutions to the following unprecedented operations in 2,000 ft of water: -mooring the lay vessel with the accuracy and the efficiency necessary to lay;laying 16 and 12 inch pipelines, abandoning and recovering them;installing artificial supports to reduce free spans of the pipeline;recovering a wet buckled pipeline. These aims, successfully attained, significantly widen the state of the art and provide proven operational solutions. Exhaustive data gathered through advanced instrumentation and computerized acquisition system contribute to a better knowledge of the actual phenomena met during operations. I. ENGINEERING APPROACH 1.1. INTRODUCTION Recent years have seen Snamprogetti concerned by sea-line design problems at depths down to 2,000 ft. The solution of the many new technical problems raised by such advanced realizations have required a careful theoretical preparation developed also in cooperation with Tecnomare through a finalized research project. The suitability of the methods applied and the feasibility of such projects needed not only a model test confirmation, but also full scale tests. Thus, lay trials in the Straits of Messina were perform ed in 1974, followed by those in the Straits of Sicily in 1976. In both projects Snamprogetti was entrusted by Snam with the Engineering and Supervision and Saipem with the Pipeline Laying and the preparation of the necessary equipment. The trials in the Straits of Messina reached a maximum depth of 1,200 ft. They gave conclusive answers to the feasibility of anchoring a lay-barge at such depths, the static behaviour of the pipe during laying, the possibility of performing particularly accurate manoeuvres. Yet, it was still to be confirmed whether:the outcome of these trials and the forecasts of the mathematical models could be applied to the deepest depths of interest to us, dynamic aspects included;the environmental survey systems, data processing, interpretation and utilization of the collected data, selection of the optimal route led to satisfactory results.