Digging out some new flowers beds directly front of the house extension and hit a solid mass in one small area about a 20cm down. As its only in one small area am I correct in assuming its not structural for the extension? Would like to break it up to enable deeper planting but not idea what it is and can we safely reduce it in size?. Anyone know what it is, its green in colour and are we OK to remove some of it. Assume we going to need a pneumatic drill/breaker as it seems pretty solid. Thanks