Peterborough Gas Compressors

Costain (Power & Energy)

£10m

A circa £10 Million civils package working for Costain & National Grid as part of the Peterborough Gas Compressor Upgrade. The works covered a varied scope including site setup, intensive investigation works, RC works, bulk excavations & demolition. These works were completed in line with a strict programme that required shutdown of the plant. Throughout the project Hercules Site Services contributed to an excellent safety culture on site with consistently high scores from both Principal Contractor (Costain) & Client (National Grid).

Site Setup included:

  • Topsoil strip & 400mm stone to previous greenfield site
  • Setup of external perimeter fencing & associated compound &
    car park areas.
  • Construction of 300m+ concrete footpaths,
  • Drawpits & 1000m of ducting for temporary power & lighting
  • Install of water and foul pipework for welfare units.
  • Installation of wheel wash unit inc. R/C slab

Phase 1 Permanent Works:

Early permanent Civils included construction of various works to facilitate the changeover of key process plant including:

  • RC slab construction for Vent Stack & Nitrogen Snuffing installations. Due to poor ground conditions, large mass foundations (up to 300m3) were required. Self-compacting concrete was used to eliminate H&S risks & ensure sufficient compaction was achieved.
  • New access gate into National Grid compound including service diversions (LV & Fibre), RC slab & installation of new high security fencing & gates.
  • 400m+ class 1 ducting installation & drawpits. GRP prefabricated units were utilised to reduce overall construction time & eliminate requirement for cranage in an area where high pressure gas lines were present.

Shutdown Works

Due to the nature of these works, they were completed during plant shutdown between April & November. Works included:

  • Extensive investigation utilising vacuum excavators due to limited as-built service information.
  • 300m+ of open cut excavations for installation of new vent lines through the middle of the compressor plant. These excavations were blinded and sanded ready for mechanical pipework installation
  • Excavation & installation of temporary works (sheets driven by others) for new balance line installation. This excavation was up to 4.5m deep and excessive breakout of rock layer. Hercules utilised BROKK remote breaker to eliminate risk of persons working within the trench during breakout operations.
  • Fence Support – excavation & installation of support steelwork to existing high security fence line to allow new pipework to pass beneath.
  • Backfill of all process pipework including import of large quantities of sand to surround ‘live’ gas pipework post installation. Due to the critical nature of the shutdown, night shifts were mobilised to ensure pipework was backfilled on time to allow plant to be brought back online.

Pre-Shutdown Enabling Works

  • Installation and modification of temporary roads utilising signal
    road plates. This was essential for access around a tight site
    where process plant was now live.
  • Excavation and removal of redundant pipework and structures
    inc. demolition of large RC bases/valve chambers. This
    included a mix of open cut excavations & use of trench boxes
    to a depth of 4m.
  • Installation of 3000m2 pile mat.
  • Installation of 2 no. cofferdams to facilitate install of Stopple
    assembly (By others). This was critical to allow isolation of
    plant for 2019 shutdown.

Support /Misc. Works

  • Along with the main contracted works, Hercules also completed &
    assisted with the maintenance of the site. These works included:
  • Dewatering of site including the management of a large
    number of pumps feeding to a siltbuster. The works were
    managed effectively in line with a strict environmental
    consent.
  • Outfall remediation works to allow discharge without causing
    erosion to bank.
  • Landscaping works across the life of the project including:
    – Removal of 200m of tree line to facilitate new
    – construction works access & control building.
    – Excavation & lining of pond to meet Environmental
    commitments of PC.
    – Planting of 30+ semi-mature tree and landscaping of
    site perimeter to provide future screen to nearby
    residents.
    – Supply of Dayworks team inc. telehandler op & banksman,
    gateman, yardman & cleaners.