The Forgotten Mile – the increased importance of the beach landing operation in regional systems By
Virginia Hoffman
Over the past several years, large, long distance transocean cable systems have led the way to the linking and development of smaller, more decentralized regional systems. Point-to-point systems, characteristic of the analog era and early fiber optic designs have all but disappeared. The allowance of branching unit designs and the ever increasing capacity made possible in the Fiber Optic Power systems and other configurations such as self healing rings and repeaterless festoons have given another dimension to the shore end segment. Generally, with large trans-ocean systems, the submarine cable came ashore at one or two locations - the beginning and end of the system - with the shore end cost and risk budget comprising a small percent of the overall system total. Regional systems, comprised of shorter distances between landings and sometimes multiple landing sites, have now significantly increased shore end installation cost percentages with respect to the overall installation or project budget. This cost percentage increase then becomes of critical importance in accurately estimating and budgeting total system cost and risk. The “forgotten mile” phrase is used in addressing the area of installation between the main lay vessel and the beach manhole otherwise known as the shore end or beach landing area. This installation area or distance, if not planned properly, can result in substantial cost increases, probable risk increase, and possibly result in environmental mitigation procedures. To alleviate or mitigate the risk associated with working in the surf environment and subsequently reduce the cost percentage for shore ending operations, it would seem that the addition of an experienced submarine cable installer familiar with all aspects of the shore ending operation to the overall system design team would bring a practical approach to the integration of both the terrestrial and submarine segments. This addition of final installation expertise would highlight and bring under discussion factors that, with smaller distance regional systems, have greater financial impact. For example, the draft of the main lay cable ship in the shallow water area of the shore end may require it to stand off further, subsequently requiring a longer cable distance offshore for the shore end operation. And that same draft, by requiring the cable ship to stand off a greater distance, may then require a pre-lay operation and not a
direct lay operation. This pre-lay would then lead to the necessity of hiring on a smaller cable handling vessel, thereby adding in additional cost and risk to the overall landing procedure. The addition to the design team of personnel experienced in shore end operations would give visibility to this issue early on and highlight either the additional cost or influence the choice of cable ship. Conversely, the draft requirement may also influence the landing area choice and then this impacts the terrestrial segment. At a minimum, experienced personnel would be available for discussion of options at the beginning of the procedure and not solely at the actual installation phase with a possible greater and unanticipated cost. Another example might be that of a bore pipe location exit point. Typically, the exit point is located outside of the surf zone, and the bore pipe is drilled well before the actual shore end operation. The actual distance offshore of the exit point may become an issue as perhaps local assets such as small boats or dive teams are not available to support these operations and assets must be brought in from other locations. Adding some length to the bore pipe would bring the exit point further offshore and allow local assets to support the landing operation. This may or may not have a contributory effect on the overall cost and risk budget, but the addition of installation team personnel in the design concept phase would at least allow the discussion of options and cost tradeoffs. Experienced installation personnel would also be able to assist in correctly interpreting the desk top study information, or in some cases, insufficient or incomplete information. Typically, a desk top study consists of collecting data for the entire route including the shore portion. Most times this study is subcontracted out to companies that are not involved in the system design phase or who do not have a vested in interest in the installation procedure –they just the collect and assemble the information and present it in a pre-agreed format. In some cases the data may not be available due to local weather conditions, and surf or reef structures may mask correct bathymetry or obstructions. Sometimes the desk top study is done months prior to the actual installation and that may also limit its value in that it is not available as real time data, subject to discussion and revision by the installer. In the Caribbean, severe weather patterns may add another element to data – for example, 25