A487 Porthmadog, Minfordd and Tremadog Bypass

Glaslyn Bridge construction, Bailey Bridge and Cambrian Coast mainline

CEEQUAL Excellent – Whole Project Award
Version 4, Oct 2012 | Portmadog, Wales, UK

Highly Commended – CEEQUAL Outstanding Achievement Awards 2013 – Ecology and Biodiversity

Client: Welsh Government
Employer’s Agent: Halcrow Group
Contractor’s Designer: Hyder Consulting
Construction: Balfour Beatty/Jones Bros JV

Assessor: David Gibson

Project summary

Ever since 1993, the preferred bypass route for this scheme has been waiting for the go-ahead. Until last year, the seaside town of Porthmadog and the adjacent villages of Minfordd and Tremadog, continued to suffer intolerable levels of vehicle congestion as tourists battled with heavy lorries and other through-traffic in the narrow streets of the town and villages.

This is now a not too distant memory. Traffic wishing to use this vital north-south trunk route can do so with ease, sweeping over the Glaslyn River on a new three span bridge and bypassing the town and villages on a new 5.3km long, single carriageway road. Meanwhile the people and businesses in Porthmadog have been given their town back. Tourists can enjoy the high street and businesses can thrive in the pleasantly bustling centre.

With more efficient transport links comes benefits in carbon emissions reduction – a prime objective for this project. Other advantages include more efficient local public transport services, more attractive cycling and pedestrian experiences, fewer accidents and improved air quality.

The construction phase had its challenges too. A temporary bailey bridge was installed over the Glaslyn to enable the 900,000 tonnes of locally quarried fill material to be brought directly to site. This avoided 106,000 lorry movements through the centre of Porthmadog, and its consequent disruption and emissions.

All the 183,000m³ of excavated material was re-used in the scheme. Waste off site was minimal – limited to the general waste from the compound area which went to a Transfer Station.

A Scheduled Ancient Monument (Roman Bath House) was protected during construction, as were slow worms (capture & release), bats (route re-aligned and flight lines maintained), badgers (temporary artificial setts constructed), water quality (settlement lagoons, SUDS etc..), ancient hedgerow, 8,400m² of valuable lowland dry acid grassland and wet woodland (all successfully translocated), and lichens (substrate relocated and placed in original orientation).

8,500m³ of Japanese knotweed infested material was sealed in an on-site cell under the guidance of the Environment Agency. This avoided 1,700 HGV journeys to a licensed landfill.

Habitats were improved or created for water vole, bats and reptiles with the 3,000m new stone walling being modified to contain reptile refugia in the rear elevation.

With four separate railway lines affected – Network Rail’s Cambrian Coast mainline, Ffestiniog Railway, Welsh Highland Railway and the Welsh Highland Heritage Railway, a working quarry, Porthmadog FC, Porthmadog Town Council, Gwynedd County Council and the local school; the liaison during the whole scheme delivery was extensive.

The Contractors provided the Aberglaslyn Mountain Rescue Team with two portacabins in the compound car park for storage and meeting and carried out work on the access track of their new premises, when they had to leave their former base.

To improve the visual impact of the scheme, overhead power cables were moved underground, embankment slopes slackened, screening bunds created and 52,000 trees and shrubs planted.