Just when I had the answer the question got changed
Apologies for the delay in getting back to you post.
We have had to undertake emergency repairs on Boyton Dock. This due to the storm surge last December and general decay. The quay side had been washed out and the surface of the dock had become very hazardous to the public. Due to financial limitations and available options we opted for sleepers. The alternatives for repair was sheet steel piling or tropical hardwood, the former was very costly and the latter is ecologically unsustainable. Untreated hardwood has a very short life span when used in the marine environment and was not a viable option. We agree that treated timber in the marine environment is not ideal but the advice given was that any impact would be very focused to the immediate area surrounding the quay rather than to the wider estuary.
If you would like to discuss further please do email me on: havergate.island@rspb.org.uk
Aaron, Site Manager