"The recent fluctuations in weather have not made for good, safe ice over an extended period," said Ryan Robson, a resource technician with South Nation Conservation, in a news release. The authority covering part of Ottawa and communities to the east said last week it was measuring ice just 15 centimetres thick near some huts around Casselman, Ont., which is considered barely safe for walking. Ice thickness around Petrie Island in east Ottawa ranged from 15 to 51 centimetres in the local association's latest report last weekend and the ice is off-limits to larger vehicles.