Passage: In 1968, Hu volunteered for his service in Gansu and worked on the construction of Liujiaxia Hydroelectric Station while also managing CPC affairs for the local branch of the Ministry of Water Resources and Electric Power. From 1969 to 1974, he worked for Sinohydro Engineering Bureau as an engineer.

Question: What was Hu's occupation at Sinohydro Engineering Bureau?
engineer