Multi Utility New 250mm Gas Main Installation


JSM was appointed Principal Contractor to install multiutilities for a multimillion pound development of 4 commercial properties and one Data Centre.



2 Months

Date Completed

October 2021

JSM installed a new 250mm gas main terminating at 4 end locations within G6 meter housings by use of open cut conventional method as well as Horizontal Directional Drilling (HDD).

POC connection 12” Low Pressure, Cast Iron, Gas main. Opposite side of main dual carriageway to site.

Live UPT branch saddle fitting, testing and drilling completed.

Main laying methods of mechanical jointing, butt fusion and electrofusion.


JSM liaised with Hertfordshire County Council, the Police, Environment Agency, keeping them updated with the progress of works, attending meetings as and when required.


  • Restricted opening notice imposed by Highway’s authority due to ongoing Motorway expansion (M25 )
  • No excavations at any given time permitted on main carriageway
  • Closure of sole footpath on busy duel carriageway
  • Multiple HV Cables and Trunk Fibreoptic data cables within 1.0 Mtr of Parent gas main
  • Temporary works, deep excavation shoring and Heras fencing
  • Poorly recorded water mains
  • Coordinating with customers timeframes


  • Ensure programme of works is built around restricted opening notice;
  • Use Horizontal Directional Drilling to install gas main across the A10
  • Initiative raised by JSM to utilise a dedicated ‘Pedestrian Marshall’ who’s sole purpose was to ensure MOP safety throughout the length and duration works
  • Trial holes and hand dig techniques used
  • Appointed temporary works designer/coordinator/supervisor and ensured approved method of excavating and shoring were put in place
  • Water mains located on the site side of A10 were not documented, trial holes prior to HDD highlighted these
  • Detailed programme of works issued to all parties to ensure works are properly coordinated; regular progress meetings with all parties involved; Ensure key staff notified of any delays or changes in advance;


Services Provided

  • Design
  • Excavation
  • Backfilling
  • Reinstatement
  • HDD
  • Gas Main installation
  • Testing
  • Commissioning
  • Traffic management
  • Handover documentation