Geotechnical assets such as material sites, rock and soil slopes, and retaining walls have a vital role in providing raw materials to build our roads and airports, as well as physically supporting core assets that make transportation possible. While it is neither practical nor advisable to manage every geotechnical asset, transportation asset management (TAM) principles can be applied effectively to geotechnical as well as other asset classes.
The Statewide Materials Geotechnical Services group is nearing completion in its research to guide development of a geotechnical asset management (GAM) plan for four primary asset classes that provide critical function and whose deterioration can negatively affect fiscal scenarios, road user mobility, and safety. The geotechnical asset types considered in this research effort are:
Inventory and condition surveys have commenced for each of these key geotechnical asset classes. Slopes and embankments have been inventoried along all NHS routes statewide while retaining walls have been inventoried along select NHS and AHS routes. The existing statewide Material Site Inventory (MSI) supplied a wealth of information for identifying service areas with a scarcity of quality materials.
An informative, Interactive GAM Program Overview developed through the GAM research efforts has been built using DOT&PF’s online GIS system. The story maps introduce the program, methods of condition assessment, asset locations and extents, and the risks posed. Tools to track the occurrence of adverse geotechnical events have permitted mapping based on a decade’s worth of maintenance activities logged in the Maintenance Management System, resulting in over 7,000 entries mapped for the first time.
This research has demonstrated that there are many opportunities for DOT&PF to address deteriorating geotechnical asset conditions. Based on the incomplete inventory collected to date, findings indicate that replacement costs for the rock slopes, unstable soil slopes and embankments, and retaining walls is approximately $19 billion, or about 3 times the value of State’s bridge inventory (based on current reconstruction costs).
Similar to bridges and pavements, fiscal modelling of network level mitigation costs, deterioration rates, and user costs have shown that there is a benefit to extending the service life of geotechnical assets. When near-term and long-term costs are summed over all three of these asset classes, every dollar invested in preservation pays for itself and saves an additional $1.06 in long term costs.
Condition state and reconstruction cost value of aggregated rock slope, soil slope (includes embankments), and retaining wall assets.
For more information, please contact Barry Benko, chief engineering geologist, at (907) 269-6211.