Project Outline:

During a principal inspection of the Nant Cwm-parc river channel and masonry retaining wall, it was advised by RCT that it is in poor condition and is no longer maintainable and a design to replace it was drawn up.

The new 70m long structure was designed by Redstart who were also the NEC project managers for the scheme. It was intended to construct the channel in precast reinforced concrete ‘L’ shaped sections, stitched together to form a U-shaped channel section across the full width of the river channel.

A 1.4m high N1 containment steel parapet with a working width of W2, with a decorative finish, was provided along the top of the retaining wall adjacent to the A4061 and to the west side of the structure.

In addition to the Nant Cwm-parc river channel, Institute Bridge at the downstream end of the scheme was assessed as weak. To strengthen the bridge, it was intended to install additional beams spliced and bolted in-situ on site below the steel troughing and the upstream reinforced concrete footway slab.

In order to replace the wall while minimising the need for highway closures on the A4061, it was intended to install a reinforced concrete U-shaped channel to support the original structure, highway and footway.

In summary, the works consisted of:

•          Civil Engineering Works associated with utility diversions on site.

•          Demolition works to existing structures such as a toilet block which spanned over the river on supporting piers and existing retaining walls / parapets.

•          Construction of a new ‘U’ shaped channel consisting of precast reinforced concrete ‘L’ shaped units, with a central reinforced concrete stitch and cast insitu tie-ins at the upstream and downstream end of the scheme.

•          Demolition of the steel troughing propped cantilever that partially supports the footway on the A4061.

•          Reinstatement of footway on A4061 along with partial reconstruction of carriageway.

•          Reinstatement and extension of footway adjacent to Library and car park access road and partial reinstatement of access road and car park surfacing.

•          Extension of footway on Institute Bridge (road bridge to north of proposed U-shaped channel).

•          Strengthening of Institute Bridge using the installation of additional spliced steel beams.

•          Installation of a blockstone weir downstream of Institute Bridge, where the existing concrete scour protection currently ends abruptly stopping fish from travelling up the Nant Cwm-parc.

•          Undertaking masonry repairs and repointing to the brickwork retaining wall supporting the A4061 at the upstream end of the scheme.

Project Delivery: -

Working methods were employed to minimise disruption to the public and on the highway, e.g., minimising traffic management on the A4061 and keeping the adjacent footpath open for as long as possible. Before Walters mobilised, TM meetings were held between all parties to ensure the correct plan was in place, restrictions were accounted for and the TM which caused the least disruption was utilised. Once our TM plans were accepted by all parties, meetings were held with local businesses and Treorchy comprehensive school to advise them of the works and also to remind the pupils of the dangers of not adhering to provided walkways on a busy carriageway.

Temporary works

Walters partnered with our temporary works designer, to oversee the fabrication design of the PCC units including lifting points and connection details. Working collaboratively, the temporary and permanent works designs were undertaken jointly between the Redstart design team, the Project Manager, our temporary works designers and the PCC unit supplier. Temporary Works design and checks were also undertaken for earthworks stability, crane pad stability and longitudinal dam arrangements for supporting the Nant Cwm flows during construction.

Added Value and Client Partnerships: -

During the mobilisation stage and throughout the project, we  reviewed the design & proposed materials and advised the designers with alternative options to provide a cost and/or time saving, although this was not a D&B contract.

Walters held design meetings with our Pre-cast concrete specialists and the Principal Designers to advise on alternative options. We liaised with service providers to ensure service diversions were accurately designed and provided information on depths, condition and alignments of gas mains and WPD apparatus.

Working closely with RCT and the local councillors, Walters recognised important dates within the calendar e.g. bank holidays, Treorchy Comprehensive school terms, exam periods and dates for local events such as Rhondda Arts Festival and Big Weekend and programme restrictions were managed around this. This fostered and enabled us to have excellent working relationships with key stakeholders and local business throughout the project until successful Completion.