A particularly awkward clean-up of 22,300m3 of contaminated sediments in Falmouth Marina has begun.
Specialist contractor Land & Water Services Ltd has provided a bespoke clean-up strategy and dredging team to the Premier Falmouth Marina. The £1.66 million project involves installing tubular mooring piles and pontoons to remove the contaminated sediment to improve the mooring and operational facilities at the site.
The close proximity of a number of highly protected sites and the inbuilt risks of recovering a highly mobile contaminant in the tidal environment, make the works particularly high profile for the regulators. Land and Water has developed their own site specific waste strategy plan, with environmental protection being offered by combining a number of technologies, developed and operated by the company.
The risk of suspended sediment release was mitigated using a combination of 4 technologies:
A ‘visor bucket’ attached to the excavator to collect the sediments from the seabed and then trap them to prevent and fluidisation on raising the bucket.
A3D dig control system allowing the operator to finely position the bucket and a telemetry system to track and monitor the excavator.
A ‘moon-pool’ system created around the digging envelope in front of the dredge pontoon. This allows sediment to be collected successfully despite the tidal conditions.
Water monitoring buoys which measure the suspended solids in the water column and alert the operators to any levels that exceed the threshold.
Land & Water will also manage the transfer and recycling of the dredged arising with 4Recycling Ltd. The low level contaminated dredgings will be used as a restoration soil over a number of nearby sites formerly used for china clay extraction.
Read more in the Silt Curtain Case Study