Taff’s Well Depot - a structured approach to design management

24 March 2022
Image of a construction site.
On a large-scale multidisciplinary project like the Taff’s Well Depot, a structured approach to design management is essential

Transport for Wales (TfW) awarded the 15-year franchise to operate train services in the Wales and Borders area to KeolisAmey. The franchise included development of the South Wales Metro – an integrated public transport network for the Cardiff and valleys area. Central to the project is Taff’s Well Depot, a purpose-built facility designed to accommodate a new fleet of light rail vehicles (LRVs).

Amey's Transport Infrastructure business, the principal contractor responsible for construction, appointed Amey Consulting to produce detailed designs for key elements of the depot. These included track, signalling, telecoms and electrical power (E&P), plus overhead line equipment (OLE) for the stabling area. The depot would also host a dedicated control centre for all signalling on the Core Valley Lines (CVL) (part of the rail network).

Other packages of work were awarded to contractors including Arcadis (the maintenance shed, office building and civil engineering works), NG Bailey (mechanical and electrical design), and Alan Griffiths (depot building construction and other elements). 

On joining the project, Amey Consulting took a standard engineering management approach to the OLE, E&P, telecoms, track and signalling designs. Each discipline was assigned a lead, known as the CRE (contractor’s responsible engineer), responsible for ensuring all relevant policies and processes were followed and liaising with other disciplines. The process was overseen by the CEM (contractor’s engineering manager), a multidisciplinary role responsible for the overall engineering co-ordination of the design and construction.

However, it was clear that the project was not proceeding as smoothly as it could have been. Faced with the need to fit a lot of infrastructure into a tightly constrained site, close collaboration between disciplines was essential. However, the different teams were struggling to integrate their designs, partly due to the variety of CAD platforms and modelling tools in play, partly because of continually changing operational requirements.

To help pull things together and restore clarity, Amey Consulting enforced a structured design management process based on a combined engineering model known as the PIM (project integrated model). This provided an all-important ‘single source of truth’, allowing all the teams to see the designs as they developed, with each discipline’s information included on different layers of the model. A clash detection system based on Bentley Systems’ Navigator was put in place.

Amey's integration manager organised two-weekly interdisciplinary design checks (IDCs) to review and update the PIM and share work in progress. Regular workshops and integration meetings provided an opportunity for discussions with the client and stakeholders to clarify project objectives and ensure requirements were being met. Bentley’s ComplyPro software was used to share information relating to risks, hazards and compliance, facilitating sign-off by the various responsible engineers.

Amey's value engineering process helped to solve problems and improve designs. For example, in collaboration with Arcadis and NG Bailey, the track in the northern part of the depot was repositioned to provide greater clearance for trains entering and exiting the maintenance shed. When a potential hazard from snapped live wires in the OLE was identified, the engineers enclosed the cables in a rigid cage above the trains.

As a result, AIP (approved in principle) designs were produced on schedule, and the project moved successfully to the next stage.