In this study, a decision support system is developed to aid selection of earthwork equipment. Physical andeconomical attributes of five off the shelf dozers, three excavators, and seven hydraulic hammers are enteredto a spreadsheet application. Seven seismic velocity-mechanical property relationships of rock and stiff soilare derived from the literature and defined to the spreadsheet application. Mechanical properties of the soilsamples obtained from the construction site are entered to the relevant data cells and seismic velocity to bemeasured at the field is estimated. Developed system estimates the ripper outputs of the dozers by usingripper production charts, cost and duration of the earthwork task is computed and likelihoods of the feasibilityof the construction machines are estimated. Developed system takes the construction duration into accountand solves time-cost trade-off problem for the selection of the best construction machine. Developedmethodology is implemented on the excavation of the foundations of a mass public housing project with 72houses. Utilization of ripper production charts without performing seismic velocity tests become possible bythe proposed method. Furthermore, time cost trade-off problem is formed and solved without humaninterruption. The developed decision support system proposes the construction machine with least total directand indirect costs. Contractors would be able to reduce their construction costs and gain competitiveadvantage on their rivals, if they implement the proposed system.