Construction firms are getting smarter and more effective by significantly improving their performance level at the job site. Particularly, cycle time which represents the time needed to complete one set of operation has been an important measure of productivity. In this study, cycle time of a petroleum storage tunnel which has many reiterative operations is investigated. With the aid of value stream analysis based on flow process chart, non-value adding activities of mucking-focused process are identified. Value stream mapping is then applied to simplify the current process as well as to remove crucial wastes of the process. Finally, this study suggests a scheme to improve the mucking process, which ultimately shows that applying the 'to-be' mode to the real site can improve the cost and average effectiveness by 9.6% and 17.7%, respectively.