This is my part of the world and I've flown in the area many times. The mast isn't 1000' or anything like it; it's only a little over 300' AGL and tbh if low enough to worry about hitting it, I'd be equally worried about hitting one of the many trees along the ridge.
Would there be a METAR for Benson at the time of the accident? Low lying fog is notoriously patchy but I'd expect conditions to be similar to those at Chalgrove.
Not sure if they have automatic reporting/someone to take readings on a Sunday.
Without inferring anything specific, I'll repeat something I've posted before: descent below MSA in IMC whilst not on a published approach procedure has killed a lot of pilots, some highly experienced.
Last edited by Sillert,V.I.; 18th Jan 2017 at 17:03.