Purpose

Bristol City Council are responsible for the
maintenance of two sandstone embankment rockfaces which run
adjacent to Park Road and Frenchay Park Road in Frome Vale ward,
east Bristol, where there have been minor rockfalls over previous
years. These weak rockfaces are at risk of partial collapse onto
the highway and are endangering the safety of the general public.
The situation is likely to worsen as the competency of the
weathered sedimentary rock deteriorates further, the proposed works
are to mitigate the risk of future rockfalls and ensure the safety
of the general public and the highway network.The proposed
methodology of works includes clearing the overgrown vegetation and
loose debris, scaling the rockfaces and anchoring a drape mesh at
necessary locations.

Content

Approval to spend up to £360,000.00 for
maintenance works to the two rockfaces adjacent to Park Road and
Frenchay Park Road in Frome Vale ward.
The proposal is for the stabilisation of two sandstone embankment
rockfaces which require stabilisation, Site A which is adjacent to
Park Road and ~35m in length, and Site B is adjacent to Frenchay
Park Road and ~90m in length. Previously the authority has
commissioned both geological investigations and topographical
surveys at both sites to inform the potential remedial works
required.
The proposed works required can be summarised as:
•De-vegetation of the face and crown of the rockface along
entire length
•Site A:
oScaling to remove surface loose rock material, likely accessed
from the road
oClear out of rock debris build up behind concrete barriers which
have previously been installed to catch minor rockfalls onto the
highway
oAnchored drape mesh installation to control and catch the fall of
future material as well as local spot bolting where necessary
oReinstallation of concrete barriers
•Site B:
oScaling to remove loose material at upper section of rockface and
also to remove high risk features as determined by geotechnical
engineer, via roped access
oRepointing and or rebuilding of the historic stone wall section,
there is no historic records of this construction but this also
requires essential maintenance as part of the remedial works
•All works be completed under temporary two-way lights
wherever possible, using three-way lights for short durations,
whilst working nearest the roundabout.

Alternative options considered

Alternative options considered but deemed
inappropriate are as follows:
•Do nothing – the rockfaces will continue to deteriorate
and suffer further rockfalls which could potentially cause harm or
injury to members of the public and may lead to emergency temporary
road closures impacting significantly on the network. The cost of
emergency action would cost significantly more than intervening now
before the condition worsens.
•Scaling only – this is an acceptable option for one of
the two rockfaces, it is not appropriate for the other where
rockfalls are more common. The addition of a drape mesh at this
location is necessary to adequately control any falling
materials.
•Rock anchored solution – a full-scale anchoring
solution over both rockfaces would reduce the current risk but the
cost of such a solution is considered inappropriate.