Job Done: Dredging Complete for Aircraft Carriers

Hi, I’m Garry Brimecome and I’m DIO’s Project Manager for the dredge at Portsmouth. I work with Philip Wise, the Principal Project Manager for the infrastructure we’re providing at Portsmouth to prepare the Naval Base for the arrival of the Royal Navy’s two new aircraft carriers. In total, the infrastructure work at Portsmouth for the carriers is an investment of more than £100m.

If you’ve read Philip’s previous blogs, you’ll know about the dredge but it’s an appropriate time to explain a little more, because the project is now finished.

HMS Queen Elizabeth and HMS Prince of Wales are the largest warships ever built in the UK. With its complement of embarked aircraft, the QE class will be the centrepiece of both the Royal Navy’s fleet and Britain’s military capability for years to come. However, their size does require the approach channel and the harbour itself to be dredged to make it deep enough for the ships to enter and berth, and as you will see, that’s no small task.

Dredging Facts

The contract was awarded in June 2015 with work commencing that November. The contractors, Boskalis Westminster Ltd, used numerous specialist ships to complete the work, including a survey vessel, trailer suction hopper dredgers, and crane barges among others. Between them, these vessels removed 3,200,000 m³ of material from the sea bed to deepen the channel.

The shipping approach channel in the Solent, outside of the harbour, is 3.5km long and was approximately 250m at its widest. The approach channel width has been effectively doubled to around 500m at its widest point. The harbour entrance itself remains unchanged in width, at approximately 110m, but has been dredged to ensure sufficient clearance below the carrier. The inner harbour has been deepened too and an area for turning the carrier created, so altogether it was a lot of work! This material was disposed of at licensed sea disposal areas nearby and some was stored for possible future reuse, for example in beach replenishment work.

We took the environmental requirements of the project very seriously. The marine licence sets out stringent requirements which take into account the local marine and coastal environment. We had to relocate local oyster growers and avoid restrictions on bird reserves. All this important work had to be done without impacting on the existing operations at HMNB Portsmouth.

Archaeology of the Sea Bed

It wasn’t just sand, gravel and so on that the dredging uncovered. Nearly 21,000 individual items were recovered and catalogued. There were numerous finds of bottles, plates and other ceramics, as well as pieces of shoes which likely belonged to a sailor.

The dredge also uncovered various pieces of ordnance, ranging from bullets and cannonballs to a British torpedo, a German sea mine and five large bombs, evidence of Portsmouth’s naval history and how intensively it was targeted during the Second World War. The dredging team worked with the Royal Navy’s Explosive Ordnance Disposal personnel to destroy or otherwise render safe these items.

There were even eight cannons, 96 cannonballs, an aircraft engine, and 36 anchors. Most interesting of all, and the most gruesome, was a human skull! This was given to the local police. All items of archaeological interest were passed to the project’s archaeologists at Wessex Archaeology for categorisation and study.

It’s been a very interesting project to work on and I’m really looking forward to seeing the culmination of all of this work when HMS Queen Elizabeth arrives here later in the year.