On February 14, 1998, at 1949 mountain standard time, an Enstrom F28C-2, N5693M, registered to and operated by Dominion Corporation, doing business as Denver Helicopter Service, was substantially damaged when it collided with terrain during a forced landing 4 miles west of Broomfield, Colorado. The commercial pilot and two passengers were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at Englewood, Colorado, approximately 30 minutes before the accident. The following is based on a telephone conversation with the pilot and this investigator, and the accident report submitted by the pilot. The pilot said the flight had proceeded normally for about 30 minutes. He then noticed the LOW FUEL PRESSURE warning light illuminate "along with engine roughness." Suspecting an imminent fuel pump failure, the pilot turned on the electric fuel pump and diverted to Jefferson County Airport. While on the initial landing approach, the engine lost power. As the pilot autorotated towards an open field, the engine began to "surge." As the pilot approached the field, he turned on the landing light and caught a glimpse of powerlines. Fearing a collision, he made a pedal turn to the right. Main rotor rpm decayed and the helicopter struck the ground. According to Textron Lycoming, the LOW FUEL PRESSURE annunciator light will illuminate when the engine driven fuel pump fails or when fuel pressure drops below a preselected value (usually 3.2 pounds per square inch). Activation of the electric fuel pump is a checklist item before takeoff and landing. Acting independently, both the engine driven and electric fuel pumps will provide sufficient fuel pressure to sustain engine power. The pilot said a postaccident fuel sample taken from the engine sump disclosed water in the fuel. The source of water contamination could not be determined. The helicopter had flown several times that day, and had been serviced by an airport refueling truck. No other reports of fuel contamination were received from aircraft operators serviced by the same truck.