Buoy maintenance services

Description

PML is now seeking tenders for the replacement of the L4 buoy which has provided excellent service for over 10 years in the field. The envisaged new buoy platform will provide the necessary infrastructure for PML to make significant technical and scientific advancements at the L4 station. Site description The western English Channel is a hostile environment for the long-term deployment of oceanographic equipment. It can be subject to strong winds at any time throughout the year with gales and storms being commonplace especially in the winter months. The prevailing winds are from the southwest and, due to the long fetch; these can generate powerful swell and large waves (during storm events to the order of 10 m). The tides are moderately strong (typically 0,6 – 0,8 ms-1 at mean spring tide with maximums anticipated in the region of 1 ms-1) with a tidal range of almost 6 m at extreme spring tides. In addition the English Channel is a major thoroughfare for commercial shipping and Plymouth itself is a naval port with a sizeable fishing fleet. The buoy and any fixed moorings need to be well characterised in order to avoid any potential collisions and strong enough to withstand the elements. Whilst the present buoy doesn’t measure wave height there is a wave buoy in close proximity (5 nautical miles) operated as part of the Channel Coastal Observatory (http://www.channelcoast.org/data_management/real_time_data/charts/?chart=98); wind data is available from the Rame Head Meteorological Station (4 nautical miles north of L4; (http://www.nci-ramehead.org.uk/weather/Current_Monitor.htm) and the meteorological data measured on the existing L4 buoy can be accessed at: http://www.westernchannelobservatory.org.uk/buoys.php The L4 station has a charted depth of 51m but as mentioned above the large tidal range should be taken into consideration. Hardware requirement and specification The envisaged replacement platform is required to be of suitable size and design to maintain the existing time-series measurements with the addition of a water column profiling capability. The WCO is recognised as a UK Natural Environment Research Council National Capability: in addition to the data buoys, vessel sampling is also maintained on a weekly basis. With a constant requirement for new measurements driven by both scientific aspirations and also technical advances, it is essential that the buoy platform has the scope to accommodate third party prototype sensors. — the platforms should be of modular construction and be simple and straightforward to change component parts. Where possible the construction materials should be lightweight and be highly resilient to chemical and biological corrosion and fouling. It is also important that the structure is easily cleaned in situ, — the buoy supplied must be able to withstand the hostile marine environment found in the western approaches off Plymouth, — it is expected that the buoy will have a minimum lifespan of 10 years – accepting the need to replace some component parts during this time due to wear and tear, — the buoy platform will be supplied in yellow indicating special mark in line with IALA requirements, — suitable lifting point arrangements must be incorporated into the design and be appropriately placed as to not compromise any sensors during lifting, — the buoy should be sufficiently ballasted to maintain inherent stability in the event of breaking free from moorings and for towing and installation purposes, — non-slip surfaces are required in locations accessed by personnel, — the buoy platform will have good sea keeping abilities and be as stable as possible in all sea conditions. Please see tender documents for full breakdown and details of the following elements: — hull, — superstructure, — winch assembly, — power systems, — control, integration and communication, — mooring design, — final considerations.