Download Access Options Bath Spa Skew Bridge

Access Options Bath Spa Skew Bridge
Project Title:
The Great Western Programme, Bath Corridor
Location:
Bath Spa Station, Bath, Bath & North East Somerset, BA1 1SU
Mileage
106m 71ch
OS Grid reference
ST 7519064313
1.0 Introduction
HOCHTIEF (UK) Construction are required to undertake SIGI works to the Skew Bridge at
Bath Spa Station. The information obtained from the site investigative works will feed into
the design which is being undertaken by TGP. Prior to undertaking any works the existing
site conditions have been considered and the environmental constraints identified with
appropriate avoidance measures and/or adequate mitigation introduced. Consideration has
been applied to the following scope of works;
1.1 Site investigative works
In order to facilitate the design coring is required to the Skew Bridge structure. There are
approximately 24no. coring locations where investigation works are required. These are
located within bridge abutment piers and archways. This critical structural data is then used
to inform the design.
1.2 Temporary scaffold access
Temporary access is required as part of the SIGI works, further
ecological surveys & licence applications (Bats) and subsequent
main structural install. The access consists of erecting a Haki
staircase tower access and temporary scaffold platform structure
spanning the length of Skew Bridge. The Haki staircase will be
located to the southwest corner of the skew bridge. It is anticipated
that the temporary structure will remain in-situ for approximately
18 months.
.
1.3 Permanent works
A new column to the central pier is required along with a bridge span along with tie-ins to
the existing structure to the east and west bridge abutments at a high level (Southside only)
2.0 Existing site conditions
2.1 Heritage
The Station and Bath Skew Bridge are Grade II listed structures.
2.2 Ecological surveys
A phase one ecological assessment was undertaken by AA Environmental 12th May, 2016.
This report identified statutory sites within 1 km - Cotswolds AONB, Non-statutory sites
within 1 km - Smallcombe Wood & Steep Slope below Oakwood (part of) SNCI, Smallcombe
Wood Cemeteries SNCI. Other - 2 areas of ancient semi-natural woodland, Bat records
within 1 km - Serotine, Daubenton’s Bat, Natterer’s Bat, Common Pipistrelle, Soprano
Pipistrelle, Brown Long-eared Bat, Greater Horseshoe Bat and Lesser Horseshoe Bat.
Protected species records within 1 km - Stag Beetle, Water Vole. Protected species records
within 100m - Otter and Badger.
AAe have also completed a series of bat activity surveys on Skew Bridge and recorded roosts
for individual soprano pipistrelle (Pipistrellus pygmaeus) and common pipistrelle (P.
pipistrellus) bats. A European Protected Species Licence (EPSL) has subsequently been
sought and granted to allow the SI works and associated scaffold installation for the bridge
(disturbance of roosting bats only).
The Site itself is described as having a ‘limited number of species recorded and can be
described as common or abundant and are found in similar places across much of Britain,
with no evidence of protected species recorded. Although there are considered to be no
specific ecological constraints to the proposals (notwithstanding bat mitigation for Skew
Bridge), a series of generic mitigation measures will be implemented to reduce any impacts
on the local wildlife.’
2.3 Arboricultural Assessment
An Arboricultural Impact Assessment (AIA) and Arboricultural Method Statement (AMS) was
undertaken by Greenman Environmental Management on 14th June, 2016. The report
provided by Greenman describes the site as; the overall arboricultural quality of the on-site
tree stock is assessed to be good with a range of early mature amenity trees developing well
within the landscaped verge between the road, and the riverside footpath and the River
Avon.
It is anticipated that two trees will be impacted by the works. T1 is a Cotoneaster shrub and
T2 is a Lime Tree. The conditions of these trees are described below in the extract taken
from Greenman’s report;
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(T1) 1no. Cotoneaster (Category C2) which is described as low quality and an
expected lifespan of less than 10 years. it does however offer landscaping value
(T2) 1no. Lime tree (category B2) is of moderate quality, an expected lifespan of 20
years and offers landscaping value.
3.0 Impact of the proposed works
In order to undertake SIGI (coring works), the installation of a Haki Staircase access and the
main works efforts have been made to consider alternative options to avoid impacting the
existing flora. These considerations are identified below;
3.1 SIGI Options
Efforts have been made to avoid impacting the existing flora which includes;
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A request to TGP (the design organisation) has been
made seeking alternative coring locations. This has
been possible in some locations. However there is
still a need to access the west abutment for coring.
In order to undertake these works safely a platform
is required. Due to the changing levels alternative
proprietary access systems would not be suitable.
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Alternative coring locations had been agreed for the
central pier which avoided the need to utilise the
hung section from the scaffold platform meaning
that a pontoon can be used. This does present a
more challenging means of access but is achievable.
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Arrangements have been made to core through the eastern abutment from within
the arches (commercial properties) as appose to the planned access which was to
core through the external face using the proposed hung scaffold.
Although other options have been pursued it is not possible to complete a full suite of SIGI
coring works without the removal of the Cotoneaster (T1) in order to access the western
abutment.
3.2 Haki Staircase
Considerations have been applied to potential alternatives to the installation of a Haki
staircase with little success. A ladder for example is suitable for means of access but this
would be inadequate due to the duration of the works. This would also contravene company
policy and is not in line with the Health & Safety Executive (HSE) Guidance. The only other
option would be to erect the Haki staircase on the towpath which would result in impacting
the towpath for the duration of the works (18 months). Therefore it is deemed not to be a
viable option.
3.3 Permanent works
Due to the need to obtain site investigative information the full impact of the main works
are unknown. However it is highly likely that a high number of personnel will need to access
the temporary structure and work area. Therefore it is essential that we provide a safe and
suitable means of access. With high level tie-ins it is anticipated that MEWPs or other
mechanical means may be required for access again this also would be likely to impact the
Cotoneaster and Lime tree.
4.0 Conclusion
Numerous options have been considered and alternative measures have been pursued
where possible to avoid directly impacting the trees and mitigate against their loss. Due to
the scope of the works required which includes; coring, platform access and potentially the
main works there is not a suitable alternative other than their removal of both the
Cotoneaster and Lime tree.