Geogrids Enable Site Access at Large Wind Farm—Technical Details and Case Study

Scout Moor Wind Farm is situated in the West Pennine Moors in Lancashire, Northwest England. The site chosen for the 65MW wind farm is located on moorland which consists of extensive peat bog covering the majority of the site. It was also anticipated that very soft to soft glacial clays would underly a significant proportion of the blanket bog. It was anticipated that the vast majority of the site was underlain by extensive unrecorded shallow mine workings. These are just a few of the factors that required consideration when Scott Wilson Ltd. were commissioned as Lead Civils Designer in 2005 for the balance of plant works for the wind farm. The commission included conducting ground investigation and the detailed design of over 12km of access track, 26 crane pad construction areas, drainage and cable runs, 26 wind turbine foundations (2.5MW), and an electrical substation for connection in to the national grid. The solution to use a `floating road' construction for the access tracks, effectively a linear load transfer platform, took into consideration the various site constraints as well as issues including construction buildability, design life and economics which all played a significant role in the decision. This paper is concerned with the principals of the design philosophy for the use of geogrid reinforced unpaved access tracks and bridged mine voids, and the use of geogrids and the elements of the detailed design methodology used to overcome the challenges set out by the moorland environment.