A bore cover can take 20 years to slowly rust to the point where a person stepping on it will fall straight through. The fall can easily be deadly. Unfortunately it is likely to be children who like to play on such an interesting object. With 170 000 Bores throughout the Perth Metro area there are highly likely to be home owners unaware of the danger. The council check pool fencing and the electricity wires but not bore covers.
There is also a real risk to household pets. Pets are just as vulnerable to falling through dangerously rusted bore covers.
There is a significant number of bores in the front yard of properties and the almost all are unsecured. If the public knew how deep many of these bore holes are they would be terrified. I have visited many properties delivering bore covers and some are so deep you cannot see the bottom. Even in the same suburb there are shallow and deep bores.