SOLUTION BRINE MINING INDUCED SUBSIDENCE AND OPEN FRACTURES FOLLOWING REGIONAL JOINT SETS, TULLY VALLEY, CENTRAL NEW YORK

From the late 1880's through the 1980's Silurian (Salina Group) halite beds 1,200-1,400 feet below the Tully Valley were solution mined to produce saturated brine for soda ash production. Over 160 solution-brine wells were located in two fields flanking the east and west valley walls. The eventual removal of 150 vertical feet (31,000 acre feet) of halite has led to widespread land-surface bulk subsidence in both brine fields. Additionally, sinkholes formed on the valley floor as a result of chimney collapse below each field.

In response to the land surface subsidence, the steep bedrock valley walls have developed open fractures along regional joint surfaces within the lower Hamilton Group. The orientations of over 400 exposed joints and open fractures were measured revealing a dominant set of NNW, a secondary set of N60¢ªE, and a minimal number of an E-W trending set. These sets respectively correspond to sets I, III, and II described by Parker, 1942 and match the orientations of undisturbed joints measured outside the brine fields. These open fractures include those open from inches to several feet wide as well as "coffin holes" which describe a linear series of soil depressions and intervening "platforms" along a fracture.

The opening of these fractures has also led to the exposure of intersecting joints, which can show an offset along the fracture toward the adjacent valley-floor sinkholes. The open fractures are now responsible for the capture of surface water in at least one stream and the interruption of overland flow; short-circuiting this water into a confined unconsolidated aquifer. This study presents the population, orientation, and spatial distribution of known fractures in the Tully Valley while also drawing comparisons to regional joint sets and discussing possible impacts.