Delineation and management of sulfidic materials in Virginia highway corridors

Excavation through sulfidic geologic materials during road construction has resulted in acid drainage related problems at numerous discrete locations across Virginia. Barren acidic roadbanks, and acidic runoff and fill seepage clearly cause local environmental problems along Virginia road corridors. Degradation of construction materials may necessitate road repairs, which can be time-consuming, costly, and a nuisance to travelers. These problems can be minimized, and even prevented, by incorporating sulfide hazard analysis into the pre-design stage of highway construction. Evaluating the likelihood of encountering sulfidic materials can decrease exposure of problematic materials. When exposure cannot be avoided, proper characterization of the material allows for immediate application of appropriate remediation procedures. Failure to rigorously identify and remediate acid-forming materials in the road planning and construction process will inevitably lead to the mix of engineering and environmental problems discussed and documented in this report. While the barren and erosive slopes resulting from acidification of cut roadbanks are the most obvious indicator of this problem, the long term emission of acidic drainage from fills is clearly the most serious environmental compliance problem that VDOT will face with sulfidic materials over time. Unfortunately, many of these problems (e.g. acid seepage from fills) do not become obvious for some period of time after the road construction contracts have been closed, leaving the full liability for environmental compliance resting upon VDOT maintenance budgets. Therefore, the true cost of identifying, handling and disposing of potentially acid-forming materials must be rigorously assessed and designed for in the road building process.