A487 Bontnewydd Bypass, Caernarfon

In 2014, the Welsh Government proposed to build a new bypass from the Goat roundabout on the A499/A487 junction to the Plas Menai roundabout. In 2015 the contract was awarded to the Balfour Beatty/Jones Bros (Ruthin) Joint Venture initially as a £65.5m deal. The welsh government are now investing £135m in the Caernarfon and Bontnewydd bypass project.

Increasing volume of traffic causing longer travel times, having a detrimental effect on local businesses, reduced economical growth, noise and air pollution and an increasing number of collisions were the main driving factors around the bypass project. Maintaining free flowing traffic was becoming impossible.

Balfour Beatty/Jones Bros took on this project for 5 key objectives — To reduce journey times between Llanwnda and Plan Menai, and Llanwnda and Caernarfon. A reduction in the number of vehicles passing through the residential communities of Llanwnda, Dinas, Bontnewydd and Caernarfon, To reduce accidents on the A487 and to improve resilliance on this road network. The scheme is set to provide a positive impact on the area by providing local employment during the construction phase, and after by improved connectivity to the local communities also providing better air quality.

Janson Bridging was approached to supply three temporary bridges on this scheme. A 24m x 5m JSB Grider Bridge with a 1m cantilevered foot walk for the A487, a 30m x 5m JSB Girder Bridge with a 1m cantilevered foot walk for the Afon Seiont and a 13.5m x 5.1m JSK Beam Bridge with a 1m cantilevered foot walk.

All three bridges were needing to have a segregated pedestrian foot walk for site personnel with the A487 bridge needing additional hoarding to prevent detritus falling onto the carriageway underneath. Working collaboratively with Balfour Beatty/Jones Bros JV, a design for the hoarding was agreed and installed to cover the additional height needed due to the large plant vehicles crossing the bridge.

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Project details

Solution
Plate girder bridge
Type
JSB
Bridge length
30m
Width
5m
Location
Bontnewydd, Wales
Client
Welsh Government
Plate girder bridge

Highlighted

Plate girder bridge (JSB)
Solution

Plate girder bridge (JSB)

Janson’s plate girder bridges (JSB) were designed for temporary applications, especially in areas with heavy traffic density and where a span of up to...
Beam bridge (JSK)
Solution

Beam bridge (JSK)

Janson’s girder bridges (JSK) were developed for creating a relatively short free span of up to maximum 21 metres.
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