REPAIR OF A FAILED CLASS V INJECTION WELL THREATENING A BURIED PIPELINE

Human development of karst terrain often necessitates the construction of storm water drainage wells along primary karst conduits to reduce the flooding of low-lying areas. These wells are regulated by the U.S. EPA as Class V injection wells. The construction method of these injection wells varies widely. Some inadequate construction methods present potential problems including low drainage capacity, clogging of the karst conduit, and sinkhole collapse. This case study discusses an active sinkhole that was previously converted to a Class V injection well and subsequently failed. The failed well was assessed and repaired to reduce the risks to an adjacent buried pipeline located in Clarksville, Tennessee, U.S.A. Geophysical, geological and geotechnical evaluations of the sinkhole were conducted between 2006 and 2009, and repair design recommendations were made. The design-build team successfully removed the failed injection well in 2009 and installed a new injection well, restoring the grade and effectively mitigating the risk to the pipeline.