This project examines the pre-construction grab sampling survey that took place during October 2005 at the site of the Rhyl Flats offshore wind farm by CMACS Ltd. This was carried out to provide information concerning the infaunal benthic populations and the sub-tidal sediment types in and around the development area as part of the 2005 baseline program. These surveys will be repeated annually as part of the FEPA monitoring. In conclusion the samples showed inside and on the boundary of the Rhyl Flats development the sediment composition was relatively consistent. The majority of sub-tidal sediments collected were composed of sand of various grades. Most grab stations produced sediment consisting of coarse-medium sand, commonly associated with variable amounts of shell fragments. Some of the more conspicuous fauna were the mask crab at site 2, the sea potato at site 9 and the Lesser sand eel at site 3.