SCS Engineers worked with Independence Power & Light Co. (IPL), in Independence, Missouri, to perform an engineering evaluation of the Blue Valley Power Station ash impoundments.
As a result of the U.S. Environmental Protection Agency’s (USEPA) ongoing national effort to evaluate the management of coal combustion residuals (CCR), a USEPA contractor conducted a review of the available documentation on the North and South Fly Ash Ponds and the Bottom Ash Pond.
Due to recommendations from that review, IPL requested our involvement in evaluating the construction and stability of the clay embankments, as well as a number of wet areas within the storm water drainage ditch running along the toe of the east dike of the North Fly Ash Pond.
SCS ultimately performed a number of borings through and adjoining the existing pond dike system to assess the stratigraphy of the embankment materials and associated foundations as well as to collect soil samples for laboratory analysis. Thereafter, a seepage and slope stability analysis was performed to assess the long-term stability of the structural dikes.
Following a historical data review, a geotechnical work plan was developed and eight direct push probes were completed to obtain electrical conductivity (EC) data to evaluate the embankment and foundation stratigraphy and to identify possible sand zones. This work provided needed information on the nature of the dike construction and the underlying foundation soil stratigraphy.
Following the EC survey, an additional six borings were performed and completed with nested piezometers to provide a detailed piezometric surface through the embankment. Armed with the historic geotechnical data, the EC data, additional boring and laboratory data, and piezometric data, SCS evaluated three critical profiles that transected the external embankment of the North and South Fly Ash Pond and the Bottom Ash Pond.
SCS assessed and modeled multiple scenarios to evaluate the long-term stability of the embankments in both the static and seismic loading condition. SCS summarized the findings of the stability and seismic evaluation of the ash impoundments in a report submitted to IPL. Seepage analysis indicated the standing water was not related to seepage through the dike.
