A470(T) Blaenau
Ffestiniog to Cancoed Improvement |
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Whole Project Award
Project Team: Transport
& Strategic Regeneration, Welsh Assembly Government
(client), Gwynedd
Consultancy & White
Young Green (design), Carillion
(construction), Gifford
& Richards
Moorehead & Laing (contractor’s designers)
The project
The upgrading of this 4 km (2 ½ miles) stretch
of the A470 Trunk Road from Blaenau Ffestiniog northwards
to Cancoed was finished in September 2008 and completes
a programme of improvements between Blaenau Ffestiniog
and Betws-y-Coed. The road passes through a valley with
steep sides formed by slate waste tips, climbs northwards
to the Crimea Pass and crosses open moorland as it drops
down into the Lledr Valley within the Snowdonia National
Park.
The objectives of the scheme were to improve road
safety and journey-time reliability by upgrading the
road whilst also minimising its impact on this environmentally
sensitive area and taking advantage of opportunities
to enhance the environment.
Difficulties in constructing the new road between
slate waste tips and five listed structures in the Llechwedd
exchange sidings area at Pont Pant-yr-Afon were overcome
by constructing a temporary diversion route through
the exchange sidings area and carefully planning traffic
management to minimise delays to travellers and ensure
safety.
The temporary diversion was constructed on top of a
separation layer placed over the existing ground surface
and on temporary deck structures spanning over the existing
bridges to avoid intrusive excavation into archaeological
remains and preserve the historical value of the Llechwedd
exchange sidings.
Collaborative approach
Crucial to the success of the project was its careful
design and programming, innovation in construction,
diligent application of Environmental and Quality Management
Systems, and the establishment of good relationships
between the project partners, the local community and
statutory bodies. This approach enabled the construction
team to remain on programme, despite working within
some of the most challenging terrain to be found anywhere
in the region.
An Environmental Liaison group was established prior
to work commencing and was maintained throughout the
project. It consisted of representatives from the Countryside
Council for Wales, Cadw, the Environment Agency, Snowdonia
National Park Authority, Gwynedd Council and the principal
project partners. The group met on a regular basis to
discuss appropriate mitigation measures and assess their
effectiveness.
Waste minimisation
Minimising waste during construction was a key objective
and extensive use was made of slate waste, which was
graded to produce materials suitable for general fill
through to pipe bedding and sub-base.
This meant that no new materials were required to construct
the road up to the underside of the surface tarmac.
Amongst other factors, CO2 production and the volume
of waste taken to landfill were closely monitored and
the site achieved significant reductions compared to
similar sites.
Drainage
The existing road drainage was uncontrolled, running
into roadside ditches and through ‘scuppers’
in the existing walls to adjacent fields. The new highway
drainage consists of gullies, filter drains, carrier
drains and combined filter and carrier drains. Surface
water is discharged from the highway drainage system
into existing watercourses.
Existing watercourses crossing the route have been
taken through large culverts to ensure that even the
most intense storm flows are conveyed safely beneath
the road. Salvaged and new stone was used to line the
stream channels and for the masonry facing of the headwalls,
to replicate the appearance of existing headwalls and
watercourses found in the area.
Ecology and nature conservation
Ecological constraints were identified during scheme
development and construction, including evidence of
otters and reptiles. The completed scheme incorporates
features to assist and protect these species, such as:
- gaps in walls to provide nesting
and roosting opportunities for reptiles, birds and
bats
- dry culverts and ledges to
enable otters to pass safely beneath the road
- otter-proof fencing associated
with watercourses that pass beneath the road.
Site clearance and the demolition of walls and a stone
barn took place only after extensive surveys of the
areas for nesting birds, bats or hibernating reptiles.
Landscape
Careful consideration was given to the effects of the
scheme on the local landscape. North of the Crimea Pass
summit, the high scenic quality of the landscape is
acknowledged by its location within the Snowdonia National
Park. South of the Crimea Pass summit the trunk road
passes through an area included in the Register of Landscapes,
Parks and Gardens of Outstanding Historic Interest in
Wales.
Account was taken of the grain of the landscape and
of important local features such as rock outcrops, watercourses
and the existing form of the highway boundary.
Care was also taken to limit the impact on man-made
features that add to the area’s special character,
such as the Llechwedd hydro-electric powerhouse.
Archaeology
Extensive archaeological surveys were undertaken prior
to works commencing on site. There are five listed structures
in the Pont Pant-yr-Afon area, including the grade-II-listed
Llechwedd hydro-electric powerhouse and the crane.
The concentration of industrial archaeological features
meant that Cadw’s (Welsh Historic Monuments) continued
advice was sought during the construction period and
an archaeological watching brief was maintained by Gwynedd
Archaeological Trust, including the preparation of an
archive report.
The listed crane was dismantled and stored at the start
of the site works and was re-erected in the Llechwedd
exchange sidings area after the temporary diversion
works had been removed.
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