Coastway Surveys was commissioned by Tarmac plc to undertake a sub-surface survey following the discovery of a 1.5m diameter hole in the new quarry floor during the removal of blast material. Initial surveys by Tarmac plumbed the hole to a depth of 25m. Coastway Surveys deployed the sonar unit, configured specifically for lowering into submerged underground cavities, to acquire horizontal profiles up to 200m range.
The survey data were geo-referenced on site using GPS and total station. These data were used to generate a plan, sections and a 3D model cavity beneath the blast area.
The resultant data set provided a volume calculation in true space which allowed the client to determine the 3D extent of the Karst cavity system and was incorporated into the quarry design model for future operations.