BNSF had replaced wood ties with concrete, on the East side of Stevens Pass down through Berne, Gaynor, and Merritt about 7 or 8 years ago. Only a year or so afterwards, I noticed they had RE - replaced the concrete ties with new ones of a different style -- removing the ties with the spring clips resting on a urethane pad next to the rail, with the ties that use a butterfly - style wire clip that screws onto the tie. The local BNSF section foreman from Skykomish ( since retired ) told me that the original style did not hold the track gauge on curves.