cbec was contracted by Salix to develop detailed designs for the protection of ten mains gas pipeline crossing points on rivers throughout southern Wales
To inform the design development, high-resolution topographic surveys and geomorphic assessments were undertaken at each site. The surveys took place in two week-long visits, with a range of river systems surveyed (from large stretches of river within the tidal zone to small, confined upland gravel-bed streams). As such, a range of survey methods was employed to safely collect the required data, from real-time kinematic and total station surveying on foot to rod-based surveys undertaken from a rigid inflatable boat (RIB).
A digital terrain model was generated from lidar and the topographic survey data to inform the design drawings. For three of the sites, where conditions dictated it to be necessary, hydraulic modelling was undertaken to evaluate shear stress and peak flow velocities. This enabled designs to be developed, which would provide the appropriate degree of protection, ensuring Wales and West Utilities (the asset owner) would have confidence in the proposed solution. For each site, detailed drawings were developed to enable the estimation of construction costs (by Salix) and to inform the final implementation of measures.