Manholes are an essential part of any municipal drainage system. Manhole covers date back at least to ancient Rome when they were square and made of stone. There are more than 20 million manholes in the US of which 4 million are over 50 years old and 5 million aged 30-50 years. When in good order they keep the piping below secure from any inux of excess water which would otherwise overwhelm drainage system. But, over time these removable caps set in roadways and sidewalks lose their integrity and signicant remedial work needs to be done.