Even after 81 years, myths still cling to Hoover Dam. No workers are entombed in the concrete and the hardhat was not invented there. But one story about the project is absolutely true. On Dec. 20, 1921, a surveying crew got caught in a flash flood and John Gregory Tierney was lost forever in the raging Colorado River, one of the first casualties of the project. Then on Dec. 20, 1935, 14 years later to the day, the job site suffered its last fatal accident A worker fell to his death from one of the two intake towers. That man was Patrick William Tierney, J.G. Tierney’s only son. Their names appear in raised metal on a plaque near the dam, never to be forgotten.