Novel use of radio-location for a ground investigation at Pen Park Hole, Bristol, United Kingdom

Number of references 15 Number of tables 2 Number of figures 12 Pen Park Hole is currently the UK’s only known hydrothermal cave system. Situated under a large housing estate in north Bristol, it contains one of Britain’s largest natural underground cavities, the roof of which is only a few metres below the surface. Discovered in 1669, the cave has had a long history of investigation, including being the object of the world’s first published cave survey in 1683. In 2006, a telecommunication company submitted a planning proposal to erect a transmitter close to the site. Given the sensitive nature of the cave and potential uncertainties in the accuracy of a more recent cave survey, Bristol City Council planners required a better fix on the location of the cave. The urban surroundings prevented traditional geophysical techniques being used, and a ground penetrating radar survey failed due to thick residual clay soils over the site. Instead, radiolocation was employed to check on the accuracy of the existing cave survey, allowing i