By using their long reach excavator with 24m of reach working from the newly constructed launch jetty, the silt was excavated on the low spring tides to provide adequate draft for the vessels being launched.

The works form part of the redevelopment in the estuary, with the site being prepared for a new boat storage facility being constructed by Plymouth Yacht Havens. Engineers assessed the loadings that the machine would place on the jetty launch structure during the excavation and loading operations. Detail planning involved selecting the low spring tide for the works so that sufficient water depth was achieved for the worst case below chart datum. For the scale of the works, floating plant was cost prohibitive and the use of a long reach machine was the preferred option.

The launching and removal of the boats from the water is done using a huge telescopic forklift crane which can lower the boats into the water. This provides the biggest risk to beaching the vessels, leading to concerns over safety and stability. The long reach machine was able to reach along the berths and load dump trucks some 15m away, thus eliminating the additional loading on the jetty which the trucks would cause.

This solution provided a cost effective method for the works, proving both safe and practical. The use of an electronic dig profile system allows the operator to 'see' underwater, using sensors located on the boom and dipper that plot the exact location of the bucket and show if it is open or closed for digging.

Successfully delivered, this project has paved the way for improved dry berth storage at this popular marina and the redevelopment of the outer harbour area.

WM Plant Hire is currently providing three long reach excavators to a site in Kings Lynn UK where Costain is building a new pumping station. The project requires a massive cofferdam to retain the tide in the estuary.

The largest excavator has a reach of 26m and weighs 90 tons. With the cofferdam nearing completion, the machines are removing silt, working around the tides and using an electronic dig profile system to excavate the required level below water.