Excavation underground lines

Excavation underground linesObjective of Excavation underground lines

Objective of Excavation underground lines procedure is to ensure the safety of underground services and safety of the employees.

HYDRAULIC OR TIMBER SHORING FOR TRENCHES

Hydraulic/timber shoring shall be provided as a method of protection against cave-ins in trenches that do not exceed 4 m in depth. Shoring for trench depths exceeding 4 m shall be purpose designed.

Excavation underground lines for CROSSING PIPELINES

  • The relevant Responsible Person shall be given a minimum of 7 days advance notice of the intention to excavate in the vicinity of existing pipelines.
  • Prior to excavation work, the required Permit to work together with an Excavation permit shall be issued for any work within 30 meters on each side of any exposed oil or gas pipeline.
  • Restrict personnel and vehicles to cross trunk lines and flow lines by recognized and established tracks.
  • In the event that no established tracks exist the following temporary crossings shall be constructed:
  • Buried lines – cover with a minimum 600-mm depth of sand and 300 mm of compacted gatch. Sand and gatch shall be levelled to a minimum 900-mm above original grade level.
  • Surface lines – cover with a minimum 900 mm depth of clean, aggregate-free sand and 450 mm of compacted gatch. Sand and gatch shall be levelled to a minimum of 1350-mm cover overflow line.
  • All routes of buried pipelines in the vicinity of the proposed excavation shall be accurately established and marked/demarcated prior to the excavation-taking place.
  • Excavate by hand shovel only within a horizontal distance of 3 meters from any oil or gas pipelines.
  • Provide adequate support for excavated pipelines.
  • Where permanent hard top roads are proposed to cross-existing pipelines, installing approved reinforced concrete culverts shall protect these pipelines.
  • New buried pipelines and other services shall cross beneath existing buried pipelines with 1 meter minimum vertical separation.

CROSSING HIGH VOLTAGE ELECTRICAL OVERHEAD TRANSMISSION LINES

  • The relevant Responsible Person shall be given a minimum of 7 days advance notice of the intention to excavate in the vicinity of existing overhead lines.
  • Prior to excavation work, the required Permit to work together with an Excavation Permit shall be issued for any work within 30 m on either side of an electrical transmission line.
  • Do not excavate within 10 m of an overhead line support pole.
  • Restrict vehicle passage to recognized and established track crossings. A Permit to work shall be issued for any heavy vehicles that have to pass or work beneath overhead lines.
  • Vehicles passing parallel to the overhead lines should maintain a minimum clearance distance of 30 m from the lines.

EXCAVATIONS ADJACENT TO OIL WELL OR OTHER WELL INSTALLATIONS

  • Give the relevant Responsible Person a minimum of 48 hours advance notice of the intention to excavate in the vicinity of a well installation.
  • A required permit to work and Excavation Permit shall be issued prior to carrying out any work within 30 meters of wells and associated equipment

CROSSING TRACKS & ROADS

  • Restrict excavation of roads and recognized tracks to outside normal hours of peak road use.
  • Give minimum 7 days notice to the relevant Responsible Person if it is necessary to close an established rig crossing on the overhead electrical transmission system or any other established track or road.
  • In all cases of disruption to normal access, a suitable, safe alternative temporary access track shall be provided, using asphalt, compacted gatch, or other suitable material.
  • Buried cables crossing tracks or company roads shall be run in UPVC suitable sleeves at 1000-mm depth as a minimum.
  • 7000-mm vertical clearance between extra high voltage overhead transmission lines and ground surface when the overhead line is crossing the roads or tracks.
  • 33kV overhead line/road crossing shall be through underground cables in UPVC sleeves 1000 mm minimum depth.
  • All reinstatement of excavated pipes, cables and other services shall be carried out to at least the same standard as the original.
  • The relevant Responsible Person referred to above will be the person appointed in charge of the specific area according to the Safety Management System.
  • On no account shall excavation in the vicinity of buried or above ground services, or with crossing these services by other than established routes proceed, without first obtaining the authority from the Responsible Person or his elected representatives.
  • In the event of any doubts concerning the protection of existing services, prior to construction work, contact the relevant Responsible Person.
  • All excavations and trenches inside hazardous operating areas shall be tested for harmful gasses and logged in a logbook signed by the responsible person before any person enter such trench.

AREAS OF ARCHAEOLOGICAL & HISTORICAL INTEREST

  • The Government department shall be notified by the client before excavation starts in known areas of archaeological and historical interest. An archaeological expert may be required to observe (and where appropriate, direct) excavation works in sensitive areas.
  • Should the client uncover art FACTS and structures of potential archaeological and historical interest during excavation, work shall stop and the Managing Director informed immediately.