The River Medway and its estuary is a major asset for Kent and over the past 28 years, a key driver in the successful regeneration of the Rochester and Chatham riverfronts.

Built to relieve congestion on the Medway bridge and allow greater access to the town and Chatham Dockyard, the tunnel is notable for being one of only two immersed tube tunnels in the UK. The tunnel was constructed in three sections with the centre section comprising a 370 metres long immersed tube running under the water and linking to cut and cover tunnels on the east and west banks of the river.

Monitoring and managing water flows is essential to ensure the safe passage of over 40,000 vehicles using the tunnel daily. Shortly after the tunnel’s opening in 1996, PSM’s 260 level transmitters were installed in four strategically placed sumps, one at either end and two in the middle, which collect water from the River Medway and road runoff.

The 4-20mA signals from these transmitters are fed into a PLC system that controls the pumping out of sumps, when the level reaches a predefined point, crucial for optimal water management, Because the level is controlled within a defined range, the transmitters were required to provide accurate measurement over a small range - 450mm for the central sumps and 1300mm for the larger end sumps, providing precise data within this critical zone.

The PSM transmitters have delivered exceptional performance throughout the tunnel's operation. One transmitter is the original unit installed in 1996, while one was replaced in 2006 and two upgraded in 2009, meaning even the newest has worked reliably for over 15 years.

PSM is also contracted to conduct annual checks and calibration certifications on the transmitters, given the critical nature of their role in water flow management.

These checks are performed during nighttime closures of the tunnel to ensure safety, and these inspections often reveal that the transmitters have maintained their accuracy, requiring no or minimal adjustments year after year.

If you would like more information on our level transmitters or any of our other products, then please visit www.psmmarine.com, email [email protected] or call +44 (0) 1444 410040.