Postconstruction Environmental Monitoring of a Fly Ash-Based Road Subbase

This paper discusses the results of post-construction environmental monitoring studies performed on a 3.4-km-long industry access truck route with unstabilized F-fly ash subbase. The road utilized approximately $\mathrm{60,000}{\mathrm{m}}^3$ of ponded F-fly ash as road subbase, generated by a nearby power plant. Long-term environmental monitoring has been an integral part of the project since the construction of the road in October 2002. Six, 9-m-deep boreholes were developed as monitoring wells around the project site to evaluate the direction of groundwater flow and changes in water quality over time. Preconstruction water quality studies were performed on water samples collected from the monitoring wells in June 2000, to establish baseline water quality data for groundwater. Samples of fly ash taken from the stockpile were subjected to leaching studies prior to construction of the road. In total, five water quality samples were collected from the monitoring wells at regular intervals, as part of the postconstruction monitoring effort. Almost all the trace element levels in groundwater comply with Illinois Classes I and II standards, and have exhibited a general decreasing trend. Overall, the fly ash subbase has performed without any significant adverse environmental effects on the groundwater and neighboring soils.