Two Royal Navy mine hunters, HMS Grimsby (M108) and HMS Brocklesby, survey the River Mersey to update naval charts. Liverpool, United Kingdom. 18th November 2011
There has been some unusual traffic in the River Mersey over the last few days. It is well known that Royal Navy mine hunters are excellent at detecting and removing ordenance, whether it is World War II relic, or a modern mine. It is less well known that mine hunters also work as fisheries patrol vessel and survey vessels. The mine detectors HMS Brocklesby (hunt class), and HMS Grimsby (sandown class) have been surveying the river to update the naval charts for the estuary.
Without accurate navigational charts it is dangerous to sail a ship in a river as there are many hazards such as man-made structures and natural structures such as moving sand banks. Over time the features of a river change so it is important to regularly update charts.
Hunt class MCMVs (Mine Counter Measure Vessels) are only 750 tonnes and are made of glass-reinforced plastic to avoid setting off mines. These are equipped with high definition sonar to detect mines and explosives. The mines are then destroyed by either the ships diving teams or the Seafox mine disposal system. Brocklesby, pennant number M33 was launched in 1982 and commissioned in 1982.
Sandown class mine hunters are made of fibre glass are 484 tons with dimensions of 52.5m * 10.9m * 2.3m. Grimsby, pennant number M108 was launched in in 1998 and commissioned in 1999.