Wayne Laepple thinks it may be closer to 1/2 mile long. It is the section of fill approaching the concrete bridge just south of Mt. Union. You can see it across the field from the county highway. From the highway it looks normal, but it was washed out in the flooding after hurricane Agnes in 1972, I believe. I haven't been on it since the bulldozers pushed the fill back up on the right-of-way, so it may be worthwhile to walk that section and see what it is like (besides trees & brush!).
I may be wrong, but I believe all the rails were buried for several hundred yards. I saw it right after the flood, and there was a definite low area through the middle of the fill that was later filled in when the field was cleared of ballast, etc. Since you live close, you might see what it is really like.
Phil