A Model for the Regional Variability of Riprap Prices in Alabama

Abstract

Riprap is widely used by departments of transportation (DOTs) for erosion control and slope stabilization activities. Even though DOTs seem to be satisfied with the ability of riprap to fulfill its intended purpose, its cost-effectiveness has been increasingly questioned. Projects, where riprap is not locally available, are affected by long-hauling distances, resulting in high unit prices. This is a concern in some parts of the state of Alabama where the geology does not contain limestone or granite for mining Riprap. Before considering alternative technologies or materials for those locations, the Alabama Department of Transportation (ALDOT) must first understand the behavior of riprap unit prices across the state. A considerable portion of the research efforts conducted under this study was used to gain an understanding of riprap unit prices, which was then applied to facilitate the geographic classification of the riprap market in Alabama. The development of cost classification required the use of advanced data collection and processing techniques, as well as the systematic iterative application of statistical tests. Quantitative research efforts resulted in the identification of four geographic regions that showed statistically significant different riprap pricing levels. The resulting geographic classification was also qualitatively explained and validated through the analysis of the location of riprap producers across the state. Finally, the four different regions were used to model the behavior of the riprap market across the state in the form of a Riprap Location Cost Index (RLCI). All research efforts presented in this thesis were conducted with historical bid data from projects awarded by ALDOT between the years 2006 and 2016.