Nov 5, 2002
The old NP track profiles for the Wahluke Slope Branch show the end of the prepared grade at MP 53.29, with a future end at MP 54.75. I don't believe the track was ever laid beyond MP 21.33, which was identified as Sagehill. However, the grade and (the few) bridges were built to the end of the prepared grade. The bridges were all heavy design, and were salvaged and re-used at other locations in the 1980's. Your recollection is correct that the line was well built, as the rail was second-hand 112 lb. welded (with a laid date of 1969), and the ballast was crushed rock from Cactus Pit, which is ballast still used on the mainline today.
My recollection is that the line was not used beyond Basin City from the mid 70's due to a slide in the vicinity of MP 11 or 12, although you could hi-rail on both sides of the slide. The line was removed between Sagehill and MP 11.20 by AFE 83-947, and some time later was removed to MP 10.0, about 1.5 miles west of Basin City. I haven't been over there in quite a few years, but the current BNSF track chart still shows the line in place from Mesa to MP 10, and the current Northwest Division timetable has a reference to the Basin City Stub.