On July 4, 1993, about 1300 hours eastern daylight time, N164SS, a Grob Speed Astir II glider, registered to Louis Groundal, Newtown, Connecticut, was destroyed after impacting trees during landing near Chester, Vermont. The certificated private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and a flight plan was not filed. The local personal flight originated from Springfield, Vermont, and was conducted under 14 CFR 91. According to the pilot; "After about one hour of soaring, attempts to return to airport to land [were] hampered by sudden heavy sink. Terrain consisted of trees and [lacked] appropriate off field landing sites, except a pond and one small very rough field (1.5 to 2 miles from airport). Attempted to land glider in field, but on final approach heavy sink put glider in a tree near the edge of the field." No mechanical malfunctions were reported.