On September 12, 1999, about 1200 Eastern Daylight Time, a Piper PA-28-201RT, N8313R, was substantially damaged while landing at the Robert J. Miller Airport (MJX), Toms River, New Jersey. The certificated commercial pilot and private pilot-rated passenger were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. The pilot stated that he departed from the Kentmorr Airport (3W3), Stevensville, Maryland, on Runway 28, a 2,400-foot long grass runway. For the takeoff, the pilot used a short and soft field procedure. During the takeoff, about halfway down the runway, a slight impact was felt in the vicinity of the right main landing gear. The takeoff was continued, and the airplane lifted off the runway normally. About 400 feet above the ground, the pilot attempted to retract the gear, and noticed that the right main gear had not retracted. The landing gear was recycled again using normal and emergency procedures, but the right main landing gear would not retract. The flight was continued uneventfully to MJX with all three landing gear extended. Upon arrival at MJX, the pilot performed a low pass over the airport to determine the condition of the landing gear. Ground personnel confirmed that all three landing gear were extended, but the right main landing gear appeared damaged. The pilot declared an emergency, and circled the airport for about an hour to burn off fuel and allow emergency equipment to arrive. The airplane touched down on Runway 24, a 5,949 foot long asphalt runway, with the remaining undamaged landing gear, before settling onto the damaged right main landing gear, which immediately collapsed. According to the airport manager at 3W3, the grass on the runway had just been cut, and was dry. At the end of Runway 28, a ditch was dug to help with the drainage. After the digging, a 2-foot high berm remained that was perpendicular to he runway. As the accident airplane was taking off, "it seemed to use all of the available runway." The airplane then proceeded off the end of the runway and came down just above the water that was located off the departure end of Runway 28, before gradually climbing to a higher altitude. A second witness located near the end of the runway stated that the airplane used the whole runway and hit a 2-foot high berm at the end. "It was the berm that put him into the air." The witness then observed the airplane make a shallow climb over the water. The witness additionally stated that the berm was located between the runway and a dirt road. The passenger, who was seated in the front right seat of the airplane, stated that the grass at 3W3 was wet and tall. As the airplane lifted off about 2/3 of the way down the runway, the passenger heard a "kabang" at the same time as the liftoff. The airplane then climbed out shallow, about 15 to 20 feet above the water. Examination of the wreckage by a Federal Aviation Administration inspector revealed that the right main landing gear forward retainer assembly and retaining bolt were sheared. The forward swivel assembly was damaged and pulled loose from the forward wing spar. Damage was also observed to the wing spar. When viewed from the face of the shear point, the forward retainer had a significant impact driving the landing gear rearward. Review of the airplane's pilot operating manual revealed takeoff performance data based for airports with paved level dry runways. There were no data charts for soft fields. The winds reported at an airport located about 20 miles to the northwest of 3W3, at 1154 were, variable at 3 knots.