On December 6, 2006, at approximately 1150 Pacific standard time, a Cessna 310B, N6640B, was substantially damaged when the left main landing gear collapsed during taxi at Frontier Airpark (WN53), Lake Stevens, Washington. The commercial pilot and his passenger were not injured. The owner/pilot was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country flight which had departed Arlington, Washington, approximately 20 minutes before the accident. No flight plan had been filed. The pilot said that while taxiing to his hangar, the left main landing gear collapsed. The airplane settled onto the left wing's tip tank. The most outboard rib will need replacing, and the wing's upper skin was also wrinkled. The airplane's landing gear had collapsed previously, approximately 6 months ago. No determination was made as to why the landing gear collapsed on this occasion.