STATS surveys the ground at Milford Haven

Until recently, the UK has been self-sufficient in gas, thanks largely to abundant supplies from gas fields, predominantly in the North Sea. However, offshore gas production is decreasing at the same time as demand for gas is rising, and analysis shows that in the future the UK will become increasingly dependent on imported gas.

To meet the demand, two new terminals to import Liquefied Natural Gas (LNG) are nearing construction completion at Milford Haven. National Grid had an obligation to connect this supply to the National Gas Transmission System and Murphy Pipelines was awarded a contract by National Grid to construct a 107 km long section of the pipeline from Brecon to Tirley.
Due for completion in October 2007, the new pipeline will have the capacity to carry 20% of the UK’s natural gas supply. As such, the whole project is of vital strategic importance for the future of the UK economy.

STATS was contracted to provide specialist technical services to the project. Initially, this involved the design, procurement, management and supervision of the ground and groundwater investigation of the proposed route, post investigation analysis of the collected data and the submission of appropriate recommendations with respect to design, construction and the final choice of route. In order to achieve this, STATS employed expertise from both within its specialist divisions and from key sub-contractors.

The main ground investigation provided considerable challenges due to the often remote locations and the rugged terrain in the foothills of the Brecon Beacons. Due to the environmentally sensitive location, National Grid was especially concerned that this phase of the work was carried out to the highest standards with minimal impact on the land, both during and after drilling. 

The  STATS geophysics team, led by Dr George Tuckwell, developed the concept of ‘virtual trial pits’ to investigate the soil characteristics and rockhead profile. A total of 17 locations were investigated using this technique and check drilling at two locations confirmed the ability of the virtual trial pits to identify rockhead to an accuracy of +/-50mm.

Commenting on the main site investigation works, STATS Project Manager, Jon Bassett said “The STATS site based team worked closely with the designers, construction crews and the quantity surveyors to develop new ways with which to make the borehole and laboratory test data, timely, relevant and meaningful. One outcome of this was that the interpretative report has very little text and as a result, the non specialist members of the project team can easily identify potentially problematic areas.”  

The pipeline route crosses an aquifer, six rivers and more than 30 ditches, and STATS has provided an assessment of the likely affects on surface groundwater resources, including flood risk assessments wherever the route crosses the floodplain. STATS also provided the scope of work for surface water monitoring to be carried out prior to, during and for four years post construction.

A mining and quarrying hazard assessment was undertaken to provide a basis for evaluating the presence and likely zones of influence from historic, current and planned mining, together with an assessment of potentially economic mineral reserves that could be mined in the future.
 
A landslide hazard assessment was also undertaken by STATS in order to assess the pipeline corridor for areas of potential slope instability.  This work was completed under the supervision of STATS Director Dr Shon Williams, with peer review by Professor Eddie Bromhead of Kingston University.

Tony O’Sullivan, Project Manger for Murphy Pipelines, said “STATS were awarded the contract because of the high quality work they provided on a similar project in Scotland and because they possess the resources and technical expertise necessary on a project of this scale.”

Commenting on progress to date, STATS Director Paul Stearns says “This project has allowed STATS to use our full range of specialist technical services to assist Murphy Pipelines and National Grid to deliver the project to very tight time constraints. Our biggest challenge has been to find the resources to manage the project and the unsung heroes have been the field engineers who have worked unbelievable hard over many months to produce top quality ground investigation data, without which the specialist expert reports could not have been produced.”

For further information contact:
STATS
Porterswood House
Porters Wood, St Albans
Hertfordshire AL3 6PQ
Tel: (01727) 833261
Fax: (01727) 835682
Website: www.stats.co.uk
Email: info@stats.co.uk

STATS is an independent consultancy practice with allied investigation, testing, monitoring and inspection services, which specialises in the environment, ground engineering, materials used in construction and built structures.

Comments