On July 13th I sent this open letter to the New York State Department of Conservation and Governor Andrew Cuomo addressing arguments by Cayuga Lake Environmental Action Now (CLEAN) that the NYSDEC should rescind its permission to emplacement of Shaft #4 so that mining to the north is stopped. The letter argues that the construction of Shaft #4 should proceed because it poses no substantial risk to the mine, and that mining should proceed because there is no reason to believe that the NYSDEC’s current yearly monitoring of the Cargill Mine will fail to assure continued safe salt mining under Lake Cayuga.
On July 21, CLEAN responded to my letter with their own letter to Governor Cuomo reiterating their concerns.
On August 7th I responded to CLEANs comments with a second open letter to Governor Cuomo.
Salient points in this discussion include:
- Shaft #4 poses no risk of mine flooding. The strata into which it will be emplaced are of low permeability, and there are no salt excavations into which the shaft the shaft could trigger a collapse. The shaft will be reamed upward from a ~1/2 mile tunnel connecting the mine. The Retsof analogy is not valid.
- Pillar design may need to change to match conditions to the north, but with proper design and monitoring by the NYSDEC there is no reason that mining cannot continue as safely to the north as in the past 95 years of mining operation to the south.
- Mining under Lake Cayuga is safer than mining under land adjacent to Lake Cayuga because the stress on supporting Pillars is less, any confined aquifers are deep, probably saline, and either not or only distally and weakly connected to water wells, and much less human infrastructure can be impacted by mine subsidence. The increase in horizontal stress in valleys is an advantage because it presses vertical fractures together and reduces their permeability.
- Natural flow through Lake Cayuga and the slow nature of mine collapse means that flooding of the Cayuga mine does not pose a significant risk of lake salinification.