On August 2, 2009, about 1139 Pacific daylight time, a Schempp-Hirth Discus CS glider, N7HV, collided with terrain while maneuvering near the Williams Gliderport (CN12), Williams, California. The private pilot, the sole occupant, received serious injuries. The glider sustained substantial damage. Visual meteorological conditions prevailed for the local flight, which was conducted in accordance with Title 14 Code of Federal Regulations (CFR) Part 91, and a flight plan was not filed. The flight was originating at the time of the accident. The pilot reported that his glider, the trail glider, and another glider, the lead glider, were being towed simultaneously by a single tow plane. The lead glider was attached with a 200-foot rope, while his glider was attached to a 300-foot rope. The trail pilot stated that after taking off the lead glider started to descend back to the runway; the lead pilot had elected to release from the tow plane due to a "slack-line" condition. The trail pilot reported that after realizing that his tow rope was under the lead glider's right wing, and that his glider and the tow plane were ascending, released his tow rope. The trail pilot stated that he feared that his tow rope would pull the lead glider's right wing up causing him to ground loop if he did not release the tow rope. The trail pilot further stated, "Instinctively, I turned right immediately after releasing from the tow plane, then realized that I did not have enough airspeed or altitude to return to the airport. I tried to level my wings but my right wing tip struck the ground." The glider came to rest upright in a rice field east of the runway and sustained substantial damage to its right wing and empennage. In a statement submitted to the IIC, the lead glider pilot reported that he was connected to a shorter tow rope, while the accident trail glider was attached to a longer tow rope, positioned aft and to the right of his glider. The lead pilot stated that after taking off he encountered a slack line, which prompted him to perform a precautionary release, followed by clearing to the left and landing uneventfully off of the west side of the runway. The lead pilot further stated that after landing he observed the accident glider strike the ground with its right wing tip heading in a southerly direction, about 100 yards east of the departure runway.