A reservoir project is built on a tributary of the Tarlang river in Turpan city to satisfy the local water supply and irrigation needs. The dam type is embankment dam with clay core. During the opera- tion of reservoir

the contact surface between the dam body and the traditional culvert under the dam is prone to leak

which would threaten the dam safety. So the horizontal directional drilling technology is in- novatively adopted in this project. The water transmission tunnel built by this technology has no direct contact with the dam

which has fundamentally improved the operational reliability of water transmission facilities and the safety of dam structure and is worth reference.