An extra £725,000 is needed to cover the cost of repairs to the Clyde Tidal Weir in Glasgow after a failure in 2017.
One of the weir’s three gates was damaged when a bolt failed, allowing water to escape, and causing riverbanks to collapse, ruining nearby roads.
A £2m project to fix the faulty north gate is under way, but experts have identified additional problems.
The £725,000 would pay for repairs to the north gate, and councillors will be asked to approve the funding on Thursday.
“If the works were not undertaken the gate would remain inoperable,” a council report reveals.
It adds a further £3m could be required in the future to improve the middle and south gates.
The weir – which maintains the upstream river at a constant level, maintaining bank stability – is near the western end of Glasgow Green.
There are three gates which are raised or lowered depending on the tide and river conditions.
Initial underwater radar and dive surveys were carried out to assess the damage to the north gate, but it wasn’t until a dam had been constructed, to allow the contractor to start repair work, that a more in-depth investigation revealed “several defects”.
The report, by councillor Anna Richardson, city convener for sustainability and carbon reduction, states investigations “found additional damage and wear which had had not been identified previously”.
There is damage to the face plate, south roller carriage and guide rails, which allow the gate to be raised and lowered, as well as the bottom skirting and staunching rod, which help form a seal to prevent water loss.
Mechanical and electrical refurbishment works have also been commissioned to bring the weir up to “modern standards” and reduce risk of future failure, the report states.
This work includes new lifting chains and motors and a computer control system, which allows the gates to be monitored and operated remotely.
A contract for the work was awarded to George Leslie Ltd in March 2020, but didn’t start until August due to the pandemic. The project is expected to be complete by August 2021.
The two remaining gates remain operational, but surveys have found a need for “significant refurbishment”, which could cost an extra £3m.
“Significant wear and tear has become evident” on the middle and south gates, the report adds.
Cllr Richardson’s report states there is a reputational and financial risk to the council if repairs aren’t carried out and a “heightened risk of bank failures” could “hinder or affect future development of riverside sites”.
By local democracy reporter Drew Sandelands