Guess where this is...and it's not Ashton Vale! http://www.bristolrovers.co.uk/news/article/contractors-on-site-683979.aspx
Back in the fifties there used to be an open-shaft coal mine near the site. The open shaft was Filton side of HPs gateway running up toward where the stadium will be erected. I don't know how far the shaft ran for, but it might be that they are taking drilling samples before finding they have an expensive problem too late.
