The pilot reported that he entered the traffic pattern for runway 30 at approximately 900 feet and completed a right turn to base. The pilot stated that while on base, he realized the aircraft was too high and deployed the spoilers halfway. As he turned to final, he stated that he was too low and at that point observed the airspeed dropping to the stall point. In an attempt to avoid a stall, the pilot lowered the aircraft nose and realized that he would not make the airport. According to the pilot, he then flew under power lines and deliberately struck a power line pole with the right wing at approximately 30 feet above ground level, in order to dissipate energy. Approximately 10 feet of the outboard right wing was severed from the aircraft as it rotated 90 degrees to the right and dropped about 15 feet before coming to rest in a swamp about 200 yards from the airport. A witness stated that he clearly observed the glider's spoilers in a fully deployed position when the aircraft rolled out on final.