On April 23, 2003, at 0718 Pacific daylight time, a Cessna 340A, N100UW, taxied over an unmarked, partially collapsed telephone junction box cover with the left main landing gear at the Boulder City Municipal Airport (61B), Boulder City, Nevada. The resultant aircraft motion collapsed the nose landing gear strut. Air Travel Partners LLC operated the airplane under the provisions of 14 CFR Part 91 as a business flight. The airplane sustained substantial damage. The airline transport pilot and two passengers were not injured. The flight was taxiing to the active runway for departure, en route to Bullhead City, Arizona. Day visual meteorological conditions prevailed, and no flight plan had been filed. According to the pilot, he taxied the airplane down the yellow-stripped centerline when the left main landing gear penetrated a telephone junction box cover. The airplane veered sharply to the left, the nose gear collapsed, and both engines stopped after their respective propeller blades contacted the taxiway. According to a witness, the day prior to the accident he observed that the telephone junction box had a noticeable crack, and its pieces were sticking up out of the taxiway. During that day, two members of the airport advisory committee checked the junction box cover and confirmed its faulty condition. Before going on their way, they placed the broken pieces back over the junction box and smoothed them over. One of the committee members left a message with the senior city electrician, who was on vacation at the time, about the broken cover. The witness stated that when the committee members left the airport, they left the cracked junction box cover unmarked and without signage on the taxiway. In a written statement, the airport advisory committee members reported noticing the cracked junction box cover the day before the accident. After looking at it, they decided that it needed to be replaced and left a message with the senior city electrician, on his cell phone, to come out and replace the cover. The senior city electrician reported being on vacation in California the day before and the day of the accident. On the morning of the accident his cell phone woke him up. An airport advisory committee member was on the phone. The committee member called to report an airplane accident and asked the electrician if he had received the message about the broken junction box cover. The electrician replied that he hadn't received the message. The following day, the electrician returned to 61B to inspect the box and found it belonged to Sprint telephone service. The electrician replaced the cover and reminded the airport manager to contact Sprint and have them come out to inspect and repair the cover. The airport manager's written statement indicated that he is a part-time employee. He stated that he had not been notified about the cracked junction box cover prior to the accident. The morning of the accident, he received a phone call in the City Community Director's Office notifying him of the accident. Upon arriving at the scene, he noted that the collapsed cover was over a Sprint telephone box. During his conversation with Sprint, they claimed that it was a city box on the airport and not Sprint's responsibility. The airport manager then had all of the airport telephone junction box covers inspected.