I really don't have much to add, but had started to post about the same thing as Casey earlier, then got called away from the computer. My understanding has been that the mainline was upgraded to 70lb. rail. Is that what the rest of you understand? Some of the rail at McEwen yard that we are using was pulled up from S.Baker I believe, so this might tend to support this as I think it is either 70 or 75lb. There are so many ties still on the ROW in various places like near the Alder Springs trestle site and over on the line between Tipton-Carol-Whitney, that are rotten, yet sound enough that you can't pull the remaining spikes out by hand. (One professional told me if the tie is sound enough to hold a spike, it still has service live, though the trackage might be FRA excepted or class 1).My understanding as to their longevity is that they were treated. I have understood that OLC had a small treating facility in S.Baker. I thought someone said it was across the river from the yard where the rr bridge is that is still in place and being used for vehicles. It would be interesting to consider axle loading. I have not seen a figure of the weight on drivers for the mallets either before or after the removal of the side tanks. FWIW Jim Bockenstette told me that in regard to future bridges on the loop at Sumpter, he figured that the most concentrated weight on one of the bridges would be in the unlikley situation of 19 and 20 being coupled together tender to tender. My gut feeling is the Mike's with their longer ridged wheelbase would have been harder on track than the 6 coupled mallets.