American Electrical Power (AEP) is developing a 348-acre residual waste landfill (RWL) located over portions of an inactive fly ash reservoir (FAR) and an area of historic mine spoil deposits near Brilliant, Ohio. Geosyntec's design required the sequential development of the RWL with a preloading period. To develop a better understanding of the required preloading period, Geosyntec designed and implemented a monitored preload fill (MPF) test program to evaluate the specific in-place compression and drainage characteristics of the fly ash in the FAR.
Geosyntec's Scope of Services
Geosyntec, working with AEP specialists, designed the MPF to be 760 feet by 500 feet with 3H:1V side slopes. The final height of the MPF was approximately 33 feet. The fill used in the program consisted of a mixture of fly ash and mine spoil materials. Geosyntec also designed an instrumentation program consisting of surface monuments, vertical inclinometers, piezometers, and a horizontal profiler. The instrumentation program was designed to collect data consisting of settlement and pore-water pressures induced by the MPF construction. The piezometer data was collected using a data logger with a remote access to allow for continuous monitoring of the change in pore water pressure induced by the preload fill. Geosyntec summarized the monitoring data and developed a vertical settlement profile of the fly ash just beneath the preload fill and at various depths in the FAR. The construction and subsequent removal of the MPF resulted in consolidation and strengthening of the in-place fly ash. Results indicated that the specific in-place fly ash for this project is relatively free draining. For design, this would allow for relatively short preload periods for individual preloads within landfill cells.
This test fill was a first-of-its-kind for assessing the in-place properties of impounded fly ash. The MPF data were used to confirm laboratory results and to reduce uncertainties regarding settlement rate and drainage characteristics of the in-place fly ash. Based on the data generated and analyses conducted as part of the MPF effort, the construction schedule was shortened and design assumptions specific to the site could be used with resultant cost benefits.