On July 12, 2003, approximately 1400 Pacific daylight time, a Cessna 172H, N2805L, registered to and being flown by a private pilot, sustained substantial damage when the aircraft overran the upwind end of the runway during landing rollout at the Sullivan Lake State airport, Washington. The pilot incurred minor injuries and the passenger incurred serious injuries. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14CFR91, and originated from Paine Field, Everett, Washington, approximately noon. The pilot reported (refer to attached NTSB Form 6120.1) that upon arrival in the area of his destination he descended to about 1,000 feet above the surface of Sullivan Lake and executed an overflight northbound along the east edge of the runway to evaluate the two windsocks. He reported observing the north windsock "...hanging limp..." but did not report any observations for the south windsock. He then executed a right turn to set up for a northbound landing reporting that there was "...no indication of wind..." during the setup. The pilot further reported that he established a stabilized approach with 40 degrees flaps and a slightly slower airspeed than normal and then pulled the nose up slightly as the aircraft passed over the threshold (at the north end of the lake). The aircraft then floated and eventually touched down with (according to the pilot) "...very little runway remaining...." The aircraft continued past the upwind end of the runway sliding down an embankment at the north end of the runway and coming to rest alongside a paved road (refer to photographs 1 and 2). A wildlife research biologist, who resided at the airstrip and was located along the west edge of the runway approximately midfield, observed the entire approach and overrun event (refer to attachment W-I). He reported seeing the aircraft passing from south to north over the runway approximately 30 feet above ground and at a "...high rate of speed, certainly above the 40-60 mph...." He thought the aircraft was executing a low pass but then realized a short time later that the aircraft did not power up. He then looked north and observed the tail of the aircraft disappearing beyond the north end of the runway. He further reported that on the afternoon of the accident he observed both windsocks "...flying out horizontal, indicating winds of at least 15 knots from South to North...." And that this was common for wind conditions on a summer afternoon. He also reported that the surface of the lake was covered with white-capped waves due to the stiff south wind. A second witness (a pilot) reported observing the aircraft during the downwind leg, approach and overrun. He reported that the aircraft appeared high and fast on the approach and that there was a direct tailwind for the pilot. He also reported that the aircraft touched down beyond midfield and saw the aircraft exit the upwind end of the runway (refer to attachment W-II). Another witness (pilot) reported seeing the aircraft during the approach and described the approach as "...fast and steep..." with a tailwind (refer to attachment W-III). The Sullivan Lake State airport is situated at the north end of Sullivan Lake. The strip is 1,900 feet long and 150 feet wide and the surface is turf. A windsock is positioned at the northwest corner of the strip and a second windsock is located at the southeast corner. Additionally, there is a permanently embedded (non-movable) wind "tee" indicator positioned to show prevailing winds from the south (refer to photograph 3).