A threat to the Memphis aquifer system is contamination. One site of potential contamination is the former Shelby County Landfill at Shelby Farms. The unlined landfill is a unique research site because it is located hydraulically up-gradient from a breach in the clay layer above the Memphis aquifer, allowing contamination – leachate – to flow into the Memphis aquifer. The landfill is reaching the end of its 30-year post closure monitoring.  However, multiple site investigations including a comprehensive groundwater sampling event in 2011 and annual sampling at wells within the confining unit breach show a continual deterioration of groundwater quality in the Memphis aquifer at the window.    

 CAESER continues to investigate groundwater contamination at the former Shelby County Landfill at Shelby Farms. Efforts have been made to define the extent of the confining unit breach including near-surface geophysics.  A seismic investigation (Waldron et al., 2009) indicated potential ancient streams (paleochannels) that may act as a conduit for leachate to move into the Memphis aquifer.  A recent resistivity study (2012) shows the impact of leachate in groundwater in the area north of the landfill and mirrors the results of the seismic study and groundwater sampling events.  A conceptual model is in the works that will incorporate well boring and near-surface geophysics data to get a better idea of what is happening in the subsurface.   

 The former Shelby County Landfill is just one of many sites in and around confining unit breach in Shelby County.  The breaches pose a threat to the high quality of water found in the Memphis aquifer.  It is important for the community to identify the location of these breaches and the threat posed by contaminated sites nearby.