Sinkhole Response

by Mark Adams

Response to Catastrophic Water Quality Pond Failure as a result of a Large Sinkhole

There are many perplexities involved when dealing with several regulatory entities for a high-profile pond failure as the result of a large sinkhole in the pond. Innovation, dynamic thinking, and regulatory management were employed for finding a solution.

Prior to the involvement of aci, several other companies attempted mitigation plans for the Texas Commission on Environmental Quality (TCEQ), the City of Austin (CoA), and the Barton Springs Edwards Aquifer Conservation District (BSEACD), but these plans were rejected. aci proposed to get the regulators involved in the process and even assist in the data collection.  This process allowed direct feedback from the regulators and a better group understanding of both scientific and bureaucratic issues in a far more timely and cost effective manner. This joint approach was only possible as the result of personal relations between Mark and the regulators.

Using this method and employing unique geophysical methods and some forensic geology, the team was able to establish that failure was the result of a sinkhole forming along a previously unmapped fault.  The high water level was above the clay liner, causing undermining of the liner and the leaching of fine material along the fault. This resulted in a significant collapse, which drained the pond.

Based on the findings of the investigation, a mitigation plan was jointly agreed to by all the regulators prior to final submittal.  The submittal was approved by all the regulatory processes with implementation shortly after. The submittal consisted of a detailed mapping of the sink, historical information of the area, electrical resistivity tomography (ERT), and geologic interpretations and causes along with an engineered cap.