Disposal of excess stock at the end of a project when facing on-going operational usage

In this paper we consider an important decision faced in many large-scale construction projects. Specifically, there is a surplus stock of an item at the end of the construction phase. Moreover, the item is to be used (as a spare part or for routine replacement) in the on-going operations of the facility. There is an opportunity to dispose of some of the stock but the marginal salvage value is not necessarily constant. The decision variable is the disposal quantity.