Hi a6et, re following remark; takes around 6 months of non use for them to start to eat through the timbers.
I was not aware that traffic changed the way white ants and similar animal borers attacked bridge timbers? Do you have any more on this please as it is an interest area of mine?
During the 70's - 80's when lines were in many ways reclassed by Shirley from general traffic to wheat or grain only lines, then & later Hill when he had many classed as low volume wheat only lines, which led to their eventual closure. The issue of white ants infecting the sleepers on all of the many branch lines was raised. Many believed the old saying of white anting the lines & anything else in a similar category was no more than a throw away line, was actually quite true. As each of the lines that were not closed & only deemed suspended for seasonal conditions, there was a program set up to ensure the lines had an inspection car run over them in each 6 month period after the last train had run over the line.
Prior to reopening for their next season the same thing had to be performed again to ensure the sleepers were in good enough condition. All it took apparently in those areas was for there being no movement or vibration through the timber sleepers for the white ants to get into the sleepers & eat them out, & they condition could not be detected from the outside, as the white ants when doing the job only eat the internals of the sleepers & anything else. They can eat wood away totally on painted surfaces, & the only way you would know about the problem is if you touched the paintwork.
We rented a house in Cedar Party at Taree, & discovered white ants had come through & made a nest in the rear condenser of the fridge. A pest exterminator came out & went to go under the house & when he tried to pull the slip bolt out to open the man hole door the whole thing collapsed, there was virtually nothing left of the door except the paint, & slip bolt which was only in place owing to the bolt being in the brickwork. First time I ever saw that & understood what was talked about when in the NW area.
The mid sized petrol fettlers cars were used for these inspections & on one location near Warialda Rail the trike came off owing to the amount of sleepers that had been eaten out by the white ants, as the previous inspection had shown up no problems. When approaching the sleepers that crumbled they looked in good order but the weight of the trike on the sleepers just crushed them. When the ganger got out & trod on others the white ant activity was intense.
While 6 months is the deemed time, it can be sooner depending on the area.