Technical insight into marina development studies
Engineers in Guernsey and Jersey will be given a personal insight into the technical investigations around a new marina in St Peter Port this week.
Guernsey Ports programme manager Jenny Giles will be guest speaker at the Channel Islands Group of Professional Engineers (CIGPE) lectures in the two islands. Jenny will give a presentation on the studies she has headed up to assess the potential for a new, all tide accessible marina in St Peter Port Harbour. Guernsey Ports has said that as well as addressing the existing shortage of berths for local boatowners, a new facility could provide a boost to the local economy.
A range of technical studies have been carried out over the past 12 months to assess the feasibility and develop an initial outline design. This was published earlier this month, through the media and online here.
The current concept design will create more than 200 additional berths, including for medium or larger sized boats which are currently in very short supply. It will also provide the opportunity to improve facilities for both visiting boatowners and local mooring holders.
Preliminary estimates put the construction costs at up to £90 million, but further work is being carried out to refine the costings and evaluate the wider financial benefits to the island. Those include a boost to the visitor economy through the improved leisure marine offering, new opportunities for the local marine services sector, and the potential to attract high net worth individuals to relocate here.
The technical work has included the design of a new breakwater, which would protect the marina and other areas of the harbour infrastructure and the seafront. This has been informed by a subsea survey, for which a large ‘jack-up barge’ spent a month in the harbour earlier this year.
Boreholes were drilled to collect material from on and below the seabed for laboratory analysis, to build a detailed picture of what is lying beneath the water. The data was used to establish where any new structures can be installed, and what depths of water can be achieved by dredging sediment and rock from the seabed.
As well as looking at the rock strengths and dredging possibilities, samples were checked for contamination. A separate survey of the existing piers and berths has also been carried out, to consider how close to these structures Guernsey Ports can dredge without risking damage to the foundations. Combined with the results of the underwater study, this has helped to identify the total area available for development, and where different facilities can be positioned.
Modelling studies were conducted to establish what impact the breakwater will have on the wave environment within the harbour. This looked at various wind conditions, as well as different designs and position for the new structure, to identify the optimum location, length and configuration.
It also modelled the effect of waves reflecting off a breakwater, to ensure there were no negative impacts to other parts of the harbour.
The States’ Trading Supervisory Board, which is responsible for Guernsey Ports, is due to present recommendations to the States next year.
Islanders are currently being asked for their views on the principle of a new marina in St Peter Port, so any feedback can be reflected in its proposals. Comments can be submitted here.
The consultation concerns the water space within the harbour, not landside arrangements. The use of the adjacent areas, including the piers, North Beach and Castle Emplacement will be the subject of a separate public consultation, to help develop a detailed Local Planning Brief for the area from La Vallette to Salerie Corner. That is expected to begin next year.