Cutter-suction Versi-Dredge 5012HP dredger removes the need for offshore disposal (continued)

The secret to ensuring your dredge is as cost efficient as possible lies in the earliest possible testing, analysis, classification and quantifying of the waste. This is a highly specialist area, and one in which Land and Water’s Environmental team are well versed. "The route to real savings is obtaining early data and early consultation with stakeholders and regulators alike" states Mr Ridding. A fine example of how an early partnership between client and specialist contractor actually delivers are the works recently completed by Land and Water for Quay Marinas Ltd at their marina sites at Conway and Deganwy.

Here, Land and Water has assisted the client from an early stage to help obtain practical and economic consents for the works, without the need to dispose of anything! By using its unique 10" suction dredger (a Versi-Dredge 5012HP supplied by the company), Land and Water has removed sediments from within the marinas with the minimum of disruption, and have discharged the removed materials in strictly controlled tidal windows directly into the fluvial channel.

"The principal at work here is the beneficial re-charge of the Estuarial Cell" explains Ridding. "By removing the sediments from the estuary there is a net, un-natural loss, but by modelling the behaviours of the water-body, and releasing the sediments during carefully selected environmental windows the sediments are successfully re-deposited by the tidal currents back onto depleting mudflats and habitats, that are otherwise under increasing attack".

Of-course the need to develop the strategy at the earliest point is always key, as there are a number of environmental and local stakeholder interests to consider but, given time and ingenuity these hurdles can be overcome, but never at short notice. The outcomes at Conway and Deganwy have been in line with client expectations, and Land and Water is now set to return in 2010 for a further 25,000m3 campaign.

Land and Water’s Versi-Dredge is currently the only Contractor-owned unit of its type operating in the UK. It travels as a single unit on a conventional HGV, and can be craned into the water and at work in short order. Unlike conventional suction dredgers, the 10" heavy-duty pump is mounted on the end of the dredge arm, and is fed directly by the cutter/harvester head as it moves across the bed of the water-body. The Versi-Dredge is stationed using conventional winch/guide wires or a pair of powered "star wheels" which are located on extended drive arms which lower themselves on to the sea bed at the rear of the vessel and propel or "walk" it forward. This is a distinct advantage inside marinas and irregular shaped lagoons or lakes as the star wheels "free" the dredger to move as it pleases without restricting cables crossing the site. In both cases the marinas remained open to navigation whilst the works took place.

This article first appeared in a trade magazine. To enquire about the Versi-Dredge, please get in touch.