Special River Crossing – North Wales

Special crossings often pose a unique set of problems and require significant planning and project management.  Green Frog Utilities has the in-house technical knowledge and expertise to successfully navigate through the most challenging schemes and are often chosen by our clients to provide turn-key solutions for these complex projects.

This specific project, located in Llanfairfechan, North Wales, involved the diversion of two above-ground crossings supplying gas to the local area. The crossings, one MP and one LP were both in critical condition and at risk of failure.  The works, aimed at providing a long-term solution to support the local network, involved installing two new PE mains by open-cut techniques through the Afon Llanfairfechan River.  The new mains were then connected into the existing infrastructure either side of the crossing, enabling the permanent abandonment and removal of the aged above-ground crossings.

A challenging project, delivered both on time and budget, with zero accidents or lost time injuries.


Llanfairfechan, Conwy


North Wales


Western Gas Alliance

Duration of contract

2 Months

Contract value

Circa. £100,000

Work content

  • Mobilisation, site clearance and establishment
  • Route clearance, dismantling stone walls and installation river diversion equipment
  • Lay new MP and LP mains through watercourse utilising open cut techniques
  • Undertake under pressure drilling to MP and LP mains required for connections
  • Undertake flow stop operations of existing MP and LP main to facilitate crossing removal
  • Decommission, abandon and remove redundant pipework crossing
  • Test all new pipework in accordance with IGE/TD/3 Edition 5.
  • Carry out tie-ins, purge, pressurise and commission all newly installed pipework
  • Rebuild wall to a finish equal to that before it was dismantled
  • Demobilise and leave site clean, safe and secure
  • Provision of Authorising Engineer (“AE”) / Competent Persons (“CP”) and an approved Non-Routine Procedure (“NRO”) in accordance with the networks Safe Control of Operations (“SCO”) procedures.

Performing under pressure.