Pontoon assembled for off-land soil investigation Black Rocks Harbor Saba

THE BOTTOM- In anticipation of an off-land soil investigation in the waters at the location of the new Black Rocks Harbor, a pontoon has been assembled in the Fort Bay Harbor.

When the sea conditions are favourable, the so-called jack-up pontoon with all the necessary equipment for the soil investigation, will be moved to the pre-selected drilling locations at the new harbour. The pontoon came from the Netherlands and was assembled on-site last week by contractor Geotron and local contractor Work Monster.

The pontoon can only be located and relocated when the wave heights are around one meter. With waves being higher on Saba most of the time, the time that the pontoon can be moved and installed in one of the drilling locations is limited. 

Due to the local sea conditions, determining a precise time when the soil investigation can be done is limited. Thus, the pontoon has been assembled and now must wait until weather conditions allow for the work to be done. As such, it requires careful planning and monitoring of the weather to make optimal use of the right weather circumstances. Possible developing storms are also carefully monitored.

Coral survey

Before the pontoon gets to the drilling location, the seabed at the drilling location will be surveyed and filmed to prevent that corals are damaged, and a buoy placed to indicate the location. The Saba Conservation Foundation (SCF) supervises the underwater survey.

To guarantee stability that is needed for the soil investigation, the pontoon has to be out of the water, jacked up. The geotechnical investigation will be conducted at a number of drilling locations, starting with the ones furthest from the coast.

There are a number of challenging factors in getting this investigation done under the local circumstances within the limited budget. The investigation takes place in a difficult location with mostly hard wind, large wave heights and an uneven seabed with big boulders. Also, the equipment is not available in the region and needs to come from far away.    

Design

The soil investigations, on-land and off-land, are needed for the final design of the Black Rocks Harbor and will be part of the tender documents for contractors. The on-land soil investigation was done in June this year. The underwater geophysical investigation will measure the layers of the sea bottom and the so-called bathymetric multi-beam survey will determine the depth of the area which was done two months ago.

Tender 

The tender documents for the new harbor are finalized. Once the permit has been received from Rijkswaterstaat, the tender documents will be issued to the contractors. The contractors need the geotechnical and geophysical surveys and bathymetric survey to engineer the harbor and calculate their prices.