As a Penn Yan native as well as that BW (I'm moving to warmer climate), Parker, I was fortunate enough to enjoy the Penn Central and early ConRail days around the plant. During my tenure as "Penn Yan and Himrod Yardmaster", I witnessed the salt trains which were dispatched out of Dewitt. Trains usually consisted of 90 cars. Power was usually 3 ALCo six axle engines. GY (Geneva) tower handled the moves. Ward K Stout of Penn Yan (wife was the village meter maid) was usually the op at GY during the shift.
The crew had to back the entire train through Himrod and up the grade to the Corning Secondary because six axle power was not allowed on the Watkins Glen Secondary. The salt mine was the only waiver. The power ran around the 90 car on the 110 car Himrod siding on the Corning Secondary. Now Himrod siding is only a 90 car siding so it doesn't have to cross Route 14 as it did then.
The salt from that mine is the same "vein" that goes under Watkins Glen and over at Cargill in Lansing. The reason for the mine closing? There were many, but Morton just felt the bottom dropped out of the market at the time.
Those were my observations. No HJ block operators were in service at the time.