Brunner Island is a three-unit, coal-fired plant owned by PPL Generation, Inc., and located on the west bank of the Susquehanna River. The plant constructed a 130-car rail line extension and storage yard atop a closed coal ash pond. Geosyntec was retained to design and implement a test fill program, prepare and implement a field sampling program, and analyze and conduct preliminary analyses of foundation performance.
Geosyntec’s Scope of Services
Geosyntec developed a field investigation and test fill program to assess the ability of the ash pond material to act as a foundation for the rail line. Geosyntec identified the location of the test fill, the materials and methods to be used in construction of the fill, the data to be collected during construction and deconstruction of the fill, and the approach to be used to analyze the data collected during the fill program. In keeping with the project’s accelerated schedule, Geosyntec prepared the plan within a matter of days, suitable for use by PPL’s contractor for the test fill construction. Geosyntec analyzed the results of the test fill program, back-calculating parameters needed to predict the settlement of the foundation materials under the 130-car rail line extension.
A preliminary geotechnical analysis of the rail line foundation provided a basis for the selection of a foundation improvement approach. We assessed the load that would be applied to the foundation by the rail line and also for the cars that will be housed in the storage yard. Using this information, the distribution of stress from the rail tracks to the top of the ash material was identified. Based on the expected stress distribution and parameters available, Geosyntec conducted a preliminary analysis to identify a range of settlement, factors of safety against slope stability, and bearing capacity of the foundation soils.
We worked with our client to collect samples from the ash pond that might be needed for testing after completion of the test fill program. Samples were collected before identification of the actual tests required, in order to accelerate the schedules for completion of geotechnical analyses and design of the full-scale preload program. Given the sensitive nature of the wet ash samples and difficulties in maintaining the integrity of the samples, we selected an experienced drilling company known for its work on challenging jobs with very successful outcomes.
Geosyntec commenced work immediately, proceeding at a rapid pace to prepare a test fill plan. We scheduled a concurrent sequence of events to fulfill an accelerated schedule and selected an experienced drilling subcontractor to ensure the quality of the sensitive samples. Combined, these actions reduced the need for resampling and reduced the overall cost and schedule of drilling activities. The resulting foundation design was several million dollars less expensive than the original deep-soil-mix design approach.