On July 21, 2004, at 1345 mountain daylight time, a Swearingen SA-226T, N84GA, piloted by an airline transport pilot, was substantially damaged when, during an aborted takeoff, the airplane departed runway 26 and struck two taxiway signs and a runway light at the Rifle/Garfield County Regional Airport (RIL), Rifle, Colorado. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted on an instrument flight rules flight plan under the provisions of Title 14 CFR Part 91. The pilot, commercial certificated copilot, and four passengers on board the airplane were not injured. The cross-country flight was originating at the time of the accident and was en route to Lafayette, Louisiana. The pilot reported that they flew from Scottsdale, Arizona, to RIL to pick up four passengers, and then fly to Lafayette. At RIL, the pilot checked the weather and determined, because of the high density altitude, he wanted to do a CAWI (Continuous Alcohol Water Injection) takeoff. At the end of the runway, the pilot brought up the engine power. The pilot said that the right engine came up to 100 percent torque immediately, but the left engine hesitated at 75 percent torque. The pilot said he gave the left engine more power lever and the torque came up to 85 to 90 percent. The pilot began his takeoff roll. At approximately 70 knots, the left engine "surged down" to 70 to 75 percent torque, and the airplane went sharply left of runway centerline. The pilot said he shouted "abort takeoff" and got the airplane aligned with the runway again. The pilot said he told the copilot to turn off the CAWI pumps. The airplane had slowed to 40 knots. The pilot said as he "initiated the power levers to idle and over the gates into the BETA range, the airplane again surged sharply to the left." The pilot said that he and the copilot applied "hard right rudder" to straighten the airplane. The pilot said the airplane departed the left side of the runway at the A4 taxiway. The copilot reported they were on takeoff roll when approximately 1,000 to 1,500 feet down the runway, the left engine CAWI system failed. The left engine's torque dropped from 100 percent to 65 to 70 percent. The airplane then surged toward the left side of the runway. The copilot said that the pilot pushed in right rudder, got the airplane under control, turned the CAWI system off, and aborted the takeoff. The copilot said, "As we slowed the plane down, suddenly something caused the right engine to surge again heading us back towards the side of the runway. Unfortunately, this time we were unable to regain control." The airplane departed the left side of the runway, struck two taxiway signs, and rolled in the grass an additional 3,000 feet before coming to rest 4,500 feet down, and 60 feet left, of the runway's edge. An examination of the airplane showed dents and punctures in the forward fuselage through the pressure vessel. Dents and punctures were also found in the left and right nose landing gear doors, the left and right engine nacelles, and the underside of the fuselage between the wings. One of the left propeller's four blades showed heavy scrapes. Two other blades showed leading edge nicks and chordwise scratches. An examination of the left engine, a Garrett TPE 331-10U turbo prop, showed a sensor wire to the CAWI system was broken. Additionally, it was discovered that the right engine was misrigged causing a delay when the engine was placed in reverse thrust. The CAWI system introduces a water/alcohol mixture to the engines' compressor air inlet and diffuser sections to produce additional thrust for takeoff. The company reported the airplane had been in maintenance at Scottsdale, Arizona, for intermittent EGT (Exhaust Gas Temperature) indications on the right engine, and intermittent and low pressure indications on the right engine CAWI. The company reported that a new EGT harness had been installed and a corroded check valve on the CAWI pumps had been "ultrasound cleaned". The flight from Scottsdale to Rifle was uneventful.