Assessing public benefits of reusing waste materials in highway projects - A framework and decision-support tool

The State of Minnesota frequently receives requests from outside sources regarding the acceptance of waste materials for reuse in highway construction and maintenance projects. These waste materials can include glass, roofing shingle tabs, shredded tires, coal ash, railroad ties, and taconite tailings. The Minnesota Department of Transportation (MnDOT) recently established a policy requiring the use of such materials if they have both short- and long-term public benefits. MnDOT sought a framework to assess these benefits. A decision framework and decision-support tool-in the form of an electronic spreadsheet-were developed, tested, and refined through the application of three case studies. The framework and the spreadsheet decision-support tool are described, and results are presented from one of the case studies. This information illustrates the types of input the spreadsheet requires and the output it produces. The spreadsheet is a flexible tool that accounts for a variety of materials and their placement in highways. It compares (a) the discounted present value over a 20-year period of incremental increases in highway construction and maintenance costs as a result of using broken glass in roads with (b) the avoidable costs of disposal by transporting the waste and landfilling it or disposing of it at the source-that is, where the waste material is generated.