Solent Crossing

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Maritime infrastructure is hugely important in facilitating the use of transport services, as well as supporting coastal communities and onshore and offshore industries.

The Isle of Wight, a county and the largest island off England, located in the English Channel 5–8 km off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent. To support the 140,000 population of the island it was imperative to ensure a sustainable maritime infrastructure.

Long O Donnell Associates's first major sea project, during the construction of the world’s longest 5km HDD of 2 no 12” High Pressure Steel Pipelines under the Solent connecting the Mainland to the Isle of Wight for our client Southern Gas Networks in two phases as follows:

Phase 1

A 1200m to 1300m long nominal 16” diameter trial pilot bore constructed from the Lepe side to rigorously explore, record and confirm (or otherwise) the viability of phase 2, including identifying and allocating contingencies and residual risks.

Work consisted of the drilling of a trial pilot bore to typically 1200 to 1300m. A detailed assessment of drilling parameters included:

  • push and rotational forces
  • drilling rates
  • weight on bit to cut the formation
  • wear of mud motor and bit
  • steering reaction and monitoring methods
  • mud pressures and returns
  • mud properties
  • mud processing requirements
  • spoil properties and handling characteristics
  • spoil disposal details
  • limitations identified on drilling parameters and interpretation of subsequent resulting risks

Phase 2

Fabrication and installation of 2 x 300mm diameter welded steel pipelines by horizontal directional drill beneath The Solent, with each drill being approximately 3850m long. The pipelines, which have an operating pressure of 26.2 barg, will be tested, purged and charged with Nitrogen to 26 bar and capped for commissioning.

Long O Donnell Associates were commissioned through the Project Services framework on a sole award basis for the provision of full Quantity Surveying and Cost Engineering Services, CDM Co-ordination Services, Health, Safety and Environmental Services, Risk Management, Programme Management and Inspection Services.

Commercial Management Consultancy Services included: contract administration, cost management, budgetary preparation and compensation event evaluation under the NEC Contract.

Client

Scotia Gas Networks

Project Value

£18M

Project Duration

24 months

Services Provided

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Solent Crossing,

Maritime infrastructure is hugely important in facilitating the use of transport services, as well as supporting coastal communities and onshore and offshore industries.

The Isle of Wight,…