BS EN 1998-1 requires a ground type classification for every seismic design in the UK, and Cheltenham's varied geology makes site-specific VS30 measurement essential. The town sits at the junction of the Cotswold escarpment and the Severn Vale, where a thin veneer of Inferior Oolite limestone can mask thick sequences of Charmouth Mudstone and Lower Lias clay. A desk study alone cannot resolve the shear wave velocity contrast between these units. Our team runs active and passive MASW surveys to deliver a measured VS30 profile, replacing assumed site classes with field data. For projects on the steep valley sides near Leckhampton Hill, where bedrock depth changes rapidly across short distances, the seismic refraction method is often combined to map the rockhead geometry alongside the velocity structure.
Site-specific VS30 measurement in Cheltenham frequently upgrades a conservative desk-study classification by one ground type, directly reducing seismic design forces.
