Building, Delivery and Installation of an Open Raft Facility

The open raft facility is a floating structure for testing of underwater ultrasonic devices located on the Wraysbury Reservoir in Middlesex, UK. It comprises a buoyant structure assembled from modular pontoons with a steel grillage deck structure sheathed with non-slip GRP panels.

There are two large moonpools with gantry cranes over each, plus four hydraulic knuckle boom cranes for handling test equipment and loading/off-loading from supply boats. Accommodation comprises modular buildings fitted out as laboratory, office, accommodation, workshop and store spaces.

The whole structure is to be modular, delivered to site by road and assembled in the water. Mooring is to four concrete sinkers with mooring wires and shock absorbing chains to the pontoon.Included in the contract is the safe and ecologically compliant disposal of the existing facility.

The objective of the project is to replace the existing facility with a new and substantially improved pontoon for the testing and calibration of underwater acoustic transducers and associated apparatus. Overall dimensions of the pontoon are approximately 32.50 metres long and 31 metres beam comprising five hulls each consisting of six (6) modular pontoons supporting a deck of steel grillage construction topped with non-slip glass fibre panels.

Safety railings, arranged in portable sections are to be fitted around the perimeter of the pontoon and around both moon pools. Within the pontoon will be two (2) moon pools one about 20.00 metres long, the other around 15 metres, both are 4.20 metres wide over which will be gantry cranes incorporating the test equipment lifting stations.

For loading/offloading equipment, stores and ancillary items there will be four (4) hydraulic knuckle boom cranes. Accommodation comprises four (4) structures constructed from modular buildings; the main two storey accommodation building, located on the centreline between the moon pools, towards the forward end of the pontoon, incorporating; on the ground floor, the laboratories, workshop, store and plant room.

On the first floor, accessed by an internal staircase, will be a canteen with kitchenette and an open plan office. Aft of the main building towards the stern is a single storey building, described as the client store/office space; it is divided into two sections, one for the storage of test equipment and the other office spaces for clients.

To starboard forward is a small single storey building for additional office space; aft to port is another small building for use as a garage/store. Suitable rubber 'D' section fendering is to be fitted around the periphery of the pontoon to prevent damage of both the pontoon and the vessels servicing it.

Services are arranged from shore to the pontoon and include 400/3/50 AC power supply, telephone and internet. Mooring of the pontoon will be by four (4) concrete sinkers suitably positioned on the reservoir bottom and connected to the pontoon by adjustable length steel galvanised wire mooring warps with heavy short link chain cable shock absorbers. Budgeted amount: £3,750,000.00