Engineer details ‘serious defects’ with popular Glenfinnan boardwalk

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Glenfinnan Community Council is to seek information from Forestry Land Scotland (FLS) on timescales, costs and future maintenance after an engineer’s report detailed serious problems with the popular ‘Dragonfly Trail’ wooden boardwalk and bridge overlooking the Callop River and Loch Shiel.

Councillors were emailed a copy of the report from FLS design engineer Graeme White ahead of last week’s October meeting of the community council. The bridge and boardwalk have been closed since July.

The Callop footbridge is near the Glenfinnan monument giving access over the Callop river to the east side of Loch Shiel and beyond.

The bridge consists of two spans, with a short ramp on the north side and a much longer ramp to the south which continues as a timber boardwalk for 250m. This infrastructure was built around 2006.

Mr White explains in his report that concerns have been raised about the ramp to the south in the past.

He states: ‘It is up to 1.8m above ground level and has a noticeable amount of lateral movement when rocked. I visited the bridge site on July 14 2021 and again on August 19 2021.

‘At my initial visit I found issues that were serious enough to warrant immediate closure of the bridge. The main defects were found in the south ramp. These included rot in the timber elements, missing cross-bearers and insufficient fixings between the cross-bearers and the posts. Each of these problems were enough to require a closure of the
bridge and ramp.

‘Rot was found in the ends of a number of cross-bearers and in the areas where they
connected to the posts weakening this key connection. There is some further rot at
the bases of some of the posts, another key area.

‘During the inspection, it was found one of the cross-bearers was missing around
half-way down the ramp. This means all the load will be going onto one beam
and its connections rather than being shared between two beams.

‘The other problem with the ramp to the south is that it doesn’t have vertical cross-
bracing which leads to excessive lateral movement. The design for the ramp replacement needs to include bracing to limit the movement.

‘Also, on the bridge proper, the handrails have been retaining moisture and are
rotting in small areas. These need to be replaced.’

Mr White goes on to say that each of these defects in their own right would be serious enough for the bridge to have been closed, as all represented a risk of a sudden failure
of a joint, post or decking leading to potentially a serious injury.

‘This risk is unacceptable to have on a managed structure on the National Forest Estate. The decision is a clear one that the bridge has to be closed,’ he said.

Mr White has recommended the affected ramp should be rebuilt, with much of the boardwalk on the approach to the bridge removed.

He adds that, since both ramps, the bridge and the first section of boardwalk sit within the Loch Shiel flood plain, it would be a benefit to remove structures from inside this zone.

Mr White has proposed rerouting the ramp onto the edge of the rocky bluff next to the bridge. It can then continue as a whin dust path outside the flood plain for around 40m before descending back onto the line of the boardwalk for 25m.

This section will have to be rebuilt boardwalk as this is still be part of the flood plain, but once out of this zone the remainder of the path can be constructed as a low maintenance whin dust path.

And he states: ‘This proposal will remove most of the structure from the flood plain zone [a Special Protection Area]. Much of the maintenance liability will also be removed. Only the minimum length of timber ramp and boardwalk would be required.’

CAPTION:

The popular Dragonfly Walk at Glenfinnan. Photograph: National Trust for Scotland.

NO F31 Dragonfly Walk