It is not clear what caused the sinkhole, although Peel Ports told the Liverpool Echothat it had been "aware of a potential issue in the area for a few weeks...We have taken immediate action to ensure the safety of all port staff and visitors and have opened an investigation into the cause of the issue which we are looking to resolve as soon as possible.
“The terminal remains open although the access to the area affected is restricted. The crane commissioning is continuing as planned."
Professor Chris Hunt, a geologist at Liverpool John Moores University, is quoted in the Financial Times as saying: It may have happened when the cranes arrived. It is always a risk when you are loading. I don't think they have used enough piles. They have clearly got a major remedial job on their hands."
Professor Hunt stated that building deepwater berths in a tidal estuary aways carries risks due to shifting geology. The riverbed has pockets of water-bearing sand squashed between layers of mud and heavy imposed loads could lead to "hydrocollapse."
Speaking to WorldCargo News, Professor Hunt said Peel Ports will certainly be carrying out extensive evaluations. "A geophysical survey using, for instance, seismography on land and in the adjoining estuary would be at most a few days and be relatively cheap, while drilling a network of test boreholes and some soils testing by a geotechnic contractor would not be ruinously expensive either. The costs and nature of remedial work will clearly depend on what the investigation will find and is impossible to forecast at this stage."
Professor Hunt points out that he has not been asked to carry out a detailed appraisal, but he says that "publically-available images in Google Earth’s historical imagery show that the structure of the dock is basically a big box with an outer cassion wall anchored by piling enclosing what looks like dredged mud, which seems to have been spread inside the structure.
"The structure might have been more stable if there had been internal compartmentalisation, which is what I meant by 'not enough piling' [as]...most likely there are major support structures under where the cranes are situated to ensure stability, considering the loads involved."
All the same, Professor Hunt adds that there is a feature in the google imagery that is consistent with "there being instability in the fill as the material was put into the dock, but I stress that this is a deduction without a site visit or other more detailed evaluation. And this instability, unless remedied, might have continued as loading of the sea bed materials under the dock progressed, thus perhaps eventually contributing to the collapse.
"The exact weight of the cranes is unlikely to be an issue, but moving very heavy loads and vibration during their introduction to the site could have contributed - strong vibration could well have led to dewatering, which might have contributed to the collapse."
Liverpool2, which opened last November, remains virtually empty although Peel Ports says it is in advanced talks with potential shipping line customers. Peel Ports contends that the cargo base of North West Britain, for which it is the natural deep sea port, is too big for shipping lines to ignore.
The company claims that its Cargo200 initiative is now backed by shippers aggregating1.35M TEU/year of UK trade and that shippers could save 200M road and rail freight miles and £350M-400M in overland transport costs by switching ocean freight to Liverpool from South East ports.
A containership calling North Continent/S England via Suez would need two extra days sailing to call at Liverpool (400 n/m x 2 @ 17 knots), with the extra bunkers at that speed costing around US$32,000 for a 10,000 TEU ship (current bunker prices). Peel Ports contends that in the context of the overall logistics chain the landside savings exceed the extra vessel costs.