M4 J48 Upgrade
Carmarthenshire County Council
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At a Glance:
  • Works planned and phased to maintain traffic along the A4138/M4 during the daytime with minimal lane and M4 slip closures during night-time to minimise disruption.
  • Complex traffic management phasing planned and agreed with both Carmarthenshire County Council and South Wales Trunk Road Agency to accommodate both restrictions and requirements to the busy junction.
  • High quality finish with zero defects upon completion
  • Project shortlisted for CIHT Transportation Project of the Year
  • Works delivered around numerous live services including High pressure DCWW main, high pressure WWU gas main, High pressure National Grid Gas pipeline, Openreach fibre optic main, motorway communication services and supplies to traffic signals and street lighting.
  • Collaborated with the client/designer to re sequence and design the works around the DCWW potable main.
  • New employment to 1 trainee engineer and 1 site operative and graduate placement for 1 quantity surveyor and 1 graduate engineer.
  • Delivered section 50 works to new community hall project as part of the community benefits.

Project Outline: -

The M4’s junction 48 had historically suffered from congestion during peak periods, primarily due to the large volumes of vehicles joining the eastbound motorway in the morning and leaving the westbound motorway in the late afternoon/early evening. On particularly busy evenings, traffic build up would reach back along the westbound off slip to the two lane mainline M4, with motorists often taking it upon themselves to queue along the hard shoulder rather than obstruct lane 1. WG and the South Wales Trunk Road Agent (SWTRA) identified the associated safety concerns and instructed Atkins to undertake a study following the Welsh Transport Appraisal Guidance (WelTAG) to review the operation of the junction as a whole and identify measures that could be implemented to alleviate the safety concerns.

Walters were appointed as the Principle Contractor to undertake the construction works under the South West Wales Regional Civil Engineering Contractors Framework with Carmarthenshire County Council as the client and Atkins as the designer and project manager. The construction works involved the widening of the A4138 eastbound lane to provide dedicated lanes to Hendy and the M4 eastbound traffic and also to create the shared use footway/cycleway to further extent the active travel network. The works also introduced dedicated lanes for the M4  traffic and the traffic from Pontardulais, which were segregated by bollards to prevent the merging of traffic until further away from the actual junction ,in the southern direction. The works also included improvements to the motorway communication signage and the traffic signals on the county road at the M4 junction.

Project Delivery: -

We developed a detailed traffic management plan to undertake the works in multiple phases whilst minimising the disruption to the local network. The works were undertaken off line during the daytime with lane closures to the county road and closures of the SWTRA M4 slip roads during night shifts to minimise disruption to the local network. The traffic to the A4138 was maintained throughout the project during the daytime.

The project faced numerous unforeseen challenges with a DCWW high pressure water main being located within the proposed works rather than the original position of the existing highway, and the discovery of mine workings in the proposed carriageway widening area. The works were re-sequenced and redesigned to accommodate the revised location of the DCWW main and the mine workings grouted up beneath the proposed highway.

Following an initially delay to the commencement of the works due to the DCWW main, the works were delivered on programme whilst incorporating additional remedial works to the existing carriageway and resolving the discovery of the mine workings.

The works were delivered to a high standard and have been shortlisted for the CIHT Transportation Project of the Year awards 2022.

Added Value and Client Partnerships: -

During the project we implemented several value-added engineering proposals to reduce the cost and increase the sustainability of the designed scheme. For example, we reduced the amount of surfacing required by amending the design to save some of the existing pavement which was due to be reconstructed. The existing asphalt on the footway was planed and the arising reused as aggregates within the footway construction to reduce the quantity of quarried aggregates and reduce carbon from quarrying activities.

Walters engaged with local schools arranging site visits in collaboration with Atkins to promote pathways into civil engineering.

Walters delivered the section 50 works to provide the temporary construction access for the new Hendy community hall development as part of their social value commitments. A trail was also created within Hendy park for a new fairy garden.

Walters exceeded their Targeted Training and Recruitment objectives through the employment of a new trainee apprentice engineer on the project along with employment of a long term unemployed site operative through the Carmarthenshire Employment Officer. Further opportunities were delivered through a graduate summer placement engineer, who took up a full time role with Atkins  upon graduating ,and graduate year in industry placement for a quantity surveyor.

The works were undertaken in areas of land which were restricted under a European Protected Species License for dormice. Mitigation measures were installed including the creation of temporary pathways to maintain the connectivity of habitat during the works for the dormice and habitat creation upon completion.