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A479 Talgarth
Relief Road and Bronllys Bypass |
82.9% |
Whole Project Award
Project team: Welsh
Assembly Government (client), BAM
Nuttall Ltd (Design & Build contractor), Hyder
Consulting (designers), Parsons
Brinckerhoff/WYG
Planning (Employer's Agent)
BAM Nuttall Ltd were awarded the Design and Build
Contract for the A479 Talgarth Relief Road and Bronllys
Bypass by the Welsh Assembly Government in early 2006,
with Hyder Consulting acting as their designers, covering
all disciplines, including environmental design, earthworks,
drainage and highways aspects.
The Project
The scheme lies partly within the Brecon Beacons National
Park and therefore required sensitive landscape treatment
in order to achieve successful integration with the
surrounding countryside. This was achieved through a
combination of careful selection of the highway alignment,
recreation of existing landscape features (i.e. hedgebanks
and hedgerows) and appropriate planting.
Acquisition of adjacent land and remnant field corners
as part of the Compulsory Purchase Order (CPO) for the
project was also a key factor in the project's development.
This allowed earthworks to be slackened (in comparison
with normal engineering slopes), profiles to be varied
and also provided room for additional landscape planting.
Overall, this has resulted in a more natural roadside
landscape.
The CEEQUAL Award not only recognises the efforts taken
to address landscape issues, but also work undertaken
throughout all stages of scheme development in relation
to archaeology, ecology and sustainable construction
in general.
Archaeology
A series of archaeological excavations was conducted
at the outset to investigate historic use of the scheme
footprint. Finds included items of Roman pottery and
a Bronze Age cist.
Ecology
Before site clearance work began, extensive ecological
surveys were carried out to ensure that the site was
clear of ecological constraints. Early surveys also
helped to inform the design of detailed mitigation measures.
The Talgarth section of the scheme includes mitigation
for a wide range of protected species, including lesser
horseshoe bats, badgers, otters and dormice. Where possible,
mitigation measures have been combined and this is best
demonstrated at Pendre Culvert, where an oversized culvert
approximately 2m in diameter was provided. The culvert
was designed to allow lesser horseshoe bats to safely
cross the line of the road, but it also accommodates
a seasonal watercourse, mammal ledges for badger and
otter and a high-level dormouse ledge to link habitat
on each side of the new road.
Monitoring of the mitigation measures during construction
and post-construction has shown that lesser horseshoe
bats are using the bat underpass. There is also evidence
that badgers and otters are present.
In addition to the dormouse shelf, the scheme includes
an innovative dormouse overhead crossing at Pendre,
intended as a long-term mitigation measure to address
potential fragmentation effects of the road. The design
of the Pendre Culvert and headwall were specifically
altered to allow mature Oak trees to be retained, thereby
ensuring the best possible connection with adjacent
vegetation.
Landscape
As part of the landscape proposals, grass seed was
sourced from local species-rich meadows, with help from
the Countryside Council for Wales (CCW), to ensure that
local provenance material was used.
In total, approximately 20ha of species-rich grassland
were created as a result of the scheme.
Water management
Watercourses that cross the scheme or run alongside
are tributaries of the River Wye Special Area of Conservation
(SAC). During construction, a surface water management
plan based on Sustainable Drainage (SuDs) principles
was developed in conjunction with the Environment Agency
to ensure that drainage from the scheme (in particular
suspended solids) did not affect the SAC. The same ponds
that were used during construction now form the attenuation
ponds for the operational scheme.
Post-construction monitoring of aquatic invertebrates
has shown that fresh-water crayfish continue to thrive
within these watercourses. Indeed these populations
are possibly some of the strongest in the National Park.
Sustainable construction
Other key features of the scheme that have contributed
to the high CEEQUAL score include the following:
- Earthworks balance –
excavated material was re-used within the scheme or
within landscape areas, thus reducing vehicle movements.
- Stone from a local quarry
was used to face Pendre Culvert, gateway entrances
and feature walling within Talgarth, reinforcing local
character and reducing transport impacts.
- Retention of mature
trees – including trees on both the Talgarth
and Bronllys sections of the scheme.
- Extensive involvement
of the local community and statutory consultees took
place during development and construction of the scheme,
including visits to the site by local school children.
- A detailed Construction
Environmental Management Plan (CEMP) was developed
and implemented, ensuring that commitments made within
the Environmental Statement and Public Inquiry were
addressed.
- Implementation of a 5-year aftercare period –
including long-term management and monitoring of the
effectiveness of mitigation measures.
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