MANUAL GUILLOTINE lock gates on the River Nene in East Anglia are being replaced by the Environment Agency because of fears for the safety of children who are using the gates' 4m high frameworks as diving platforms.
Jackson Civil Engineering is replacing the two 60 year old, 4.7m wide gates at the downstream ends of Upper Wellingborough and Higham Ferrers locks near Peterborough. It is replacing them with traditional manually operated steel mitre gates that rise only about half a metre above the water level.
The £1M contract includes the replacement of a third guillotine gate at the Lower Wellingborough Lock at the end of this year.
There are more than 30 similar locks on the River Nene navigation and a small number on the Great Ouse in Yorkshire. Agency project manager Steve Crooks said that seven more guillotine gates in or near urban areas were being considered for replacement. 'All our guillotine gates present severe health and safety issues, ' he added. 'Inexperienced boaters could lift them too quickly, causing dangerous currents in and below the lock. And there is a risk of overwinding jamming the 7t counterweight and leaving the mechanism in a dangerous condition.'
Where daredevil children are unlikely to be a problem, the Agency will probably retain the gates, but change them to electric operation, Crooks said. This would make it impossible to open the gates too fast or too high, but still allow them to act as flood control sluices where necessary.
'In high flow conditions, we chain open the upstream mitre gates and raise the guillotine gates as required to reduce the risk of flooding, ' Crooks explained.
Replacement downstream mitre gates may be less attractive to children, but they bring with them new problems. On the Nene, the upstream gates are frequently overtopped, keeping the locks permanently full to overflowing. This is not a problem with guillotine gates downstream as these can easily cope with the increased flows needed to empty the lock.
'But with mitre gates, even with the penstocks wide open, the outflow might not be high enough to drain down the lock far enough to allow the gates to open, ' Crooks said.
'So we're having to raise the upstream gates on the three locks currently being worked on and put in extra flood alleviation measures to compensate for the loss of the guillotine gates.'