Mine failure associated with a pressurized brine horizon: Retsof Salt Mine, western New York

The eventual loss of the Retsof Salt Mine from flooding was initiated on Ma rch 12, 1994 with a magnitude 3.6 earthquake, the collapse of a small-pilla r panel, an initial inrush of brine and gas to the mine and a sustained inf low of fresh water. An examination of closure data for two mine panels invo lved in the inflow suggested an anomalous buildup of fluid pressure above t he panels in the period leading up to their collapse, The initial brine and gas inflow immediately following the collapse coincided with the apparent relief of the excess pressure. The potential existence of a pre-collapse, p ressurized, brine and gas pool above the panels was investigated through an analysis of nineteenth century solution mining data, a review of recent sa lt mine data, and an interpretation of geologic and geophysical data from p ost-collapse investigations. Published reports from the nineteenth century reveal that natural brine and gas pools existed in the region prior to mini ng, Correlation of gamma ray logs with geologic logs from contemporary dril l holes and core holes provided a mechanism for interpreting the distributi on of those natural brine pools, Our investigation indicated that natural g as and brine pools existed within Unit D of the Syracuse Formation approxim ately 160 ft above the mining horizon. Such brine accumulation apparently f ormed from the circulation of meteoric water through vertical discontinuiti es that were connected to overlying fresh water aquifers long before mining began in the valley in the late nineteenth century.