Cargill Mine Shaft #4 Environmental Issues
Relevant documents are available at:
Salinization of Cayuga Lake
In 1994, portions of the largest salt mine in the US, the Akzo-Nobel rock salt mine in Livingston County (“the Retsof mine”), reportedly collapsed due to a combination of overly-wide mining spans, the introduction of smaller yielding pillars, and unanticipated weaknesses in the overlying rock layers. The collapse led to flooding of the entire mine by the local aquifer and significant ground subsidence that damaged roads, bridges, houses, and farmland. Currently,--more than 20 years after the collapse—brine from the flooded mine is beginning to salinize a deep aquifer located to the south of the mine collapse zone.
Geolgoist Ray Vaughan has concluded that this deep aquifer contains relatively fresh, potable water and that it will gradually become salinized and non-potable over a period of decades and centuries as the Retsof mine (now filled with saturated or nearly saturated brine) undergoes room closure, causing the brine to be squeezed out of the gradually closing mine into the aquifer. Vaughan believes that the volume of the deep aquifer is probably not large enough to accept/contain all of the brine and associated salinity that will be squeezed out of the flooded mine. Thus, other higher aquifers will also become salinized and non-potable over a period of decades and centuries.
Unfortunately, the long-term release of brine will not be limited to the volume of brine currently in the Retsof Mine (about 15 billion gallons). Mixing with freshwater will occur creating larger volumes of salinized water and a process of on-going dissolution of salt.
In 1995, legislative hearings[1] raised concern that a similar failure might occur in Cargill’s Cayuga Salt Mine under Cayuga Lake because of similar geology and mining techniques. Assemblyman Martin Luster stated in the hearings that “I have no desire to have, in my district, what might become the world’s third largest in-land body of salt water.” Could such a disaster really happen here? Geologists and company officials have disputed the similarities and differences between the two mines, but the public deserves to hear both sides of the story.
Dr. John Warren, an independent expert on salt geology notes the poor public documentation on the highly-fractured rock around the Mine Shaft #4 location. He is concerned that in reaming the hole for Mine Shaft #4, Cargill could establish an unintended connection between an aquifer beneath Cayuga Lake and the mine itself.Mine flooding—whether accidental or as part of a planned abandonment strategy--could eventually lead to gradual or sudden subsidence of the lakebed and/or communications between the flooded mine and Cayuga Lake. The result could be the same sort of salinization tipping point that is happening at Retsof.
This time, however, it would be lake salinization, not aquifer salinization. Worse, the deepest aquifer between the mine and Cayuga Lake may already be salinized, so our safety margin could be even less, especially if “trough subsidence” caused by salt mining pressurized the saline aquifer resulting in brine flows into Cayuga Lake. No data on subsidence of the lake floor over the mine are publically available. However, a group of 22 subsidence monuments over earlier salt mining under the Town of Lansing indicate subsidence of greater than 1 foot in 35 years.
How likely is a catastrophic lake salinization scenario? Dr. Warren says we won’t know without further public information, which could be provided in a DEIS process.
What is Adequate Bedrock Separation?
A consultant to the DEC, John T. Boyd & Co. included this table in a 2002 review of Cargill’s Mined Land Use Plan:
According to Dr. Warren, 2013 stratigraphic data from Cargill consultant RESPEC indicate that at the latitude of the proposed Shaft 4 project, bedrock separation may be as little as about 500 feet, which is significantly below the Retsof figure of 600 feet. Note also that due to greater depth, dead load pressure on top of arches in the Cayuga Mine is estimated to be 63% higher.
Cargill maintains that its seismic studies, room closure rate data, and other research on the mine and the geology it exists in are trade secrets that a competitor could take advantage of. Cargill disputes whether or not DEC has regulatory jurisdiction over its underground mining activities. Under a “stipulation” dating back to the early 2000s, Cargill agrees to provide certain data to DEC, to pay for a mining consultant to DEC for their mine, and allow an annual tour of the mine by DEC officials. While being held at arms-length in this manner, DEC has thus-far lacked the resolve to have ever required a DEIS any aspect of this mine. This is the same regulatory stasis that led to the Retsof Mine failure.
Greenhouse Gases
Based on the amount of natural gas encountered in Cargill’s test hole at the proposed Shaft 4 site, as much as 4.85 million cubic feet[2] of natural gas could be released during the year or more required to ream and seal the shaft. DEC’s negative declaration makes no mention of climate change impacts, and gives the erroneous impression that methane leaking from the Shaft 4 might actually be contained within the mine. In fact it will be vented from Cargill’s shaft at Portland Point within days. (Cargill is already venting methane from the mine at their Shaft 3, but sends no information to the EPA.) The public deserves to know both the quantity and the potential effects of that natural gas leakage.
Viewshed
DEC’s negative declaration states that “photo simulations” from Taughannock Park and from Frontenac Point indicate that the planned 93’-high shaft building and two other buildings were either “obstructed from view by vegetation or topography or were barely discernible.” No mention is made as to whether the photo simulation was done in summer or winter. However, an independent leaf-off season viewshed map indicates that the tower will be visible from at least three miles of Cayuga Lake’s west shoreline in Tompkins County, and from at least 2.5 miles of west shoreline in Seneca County. Thus far, we know of no landowners in Seneca County that have even been notified of the proposed project.
The nine-story shaft building would be located within a quarter of a mile of Route 34B and it is probable that the top seven stories will be visible from Route 34B and from large areas of the lake, completely changing the ambiance of this scenic rural landscape. The County’s Unique Natural Area No. 24 lies just west of the project site. The public should be informed of the adverse effects the project will have on the viewshed.
Industrialization
The land on either side of Route 34B north of Salmon Creek is zoned agricultural/residential and currently has no hint of industrial activity. Should Cargill apply to expand its permit, much of their salt removal and processing at Portland Point might move to this site. Cargill’s facility on Portland Point is an eyesore on the lake’s 85+ mile circumference. To place a similar facility directly across from Taughannock Park would be a major environmental impact. The public deserves to know if this level of industrialization will be likely if this project is approved.
Water storage
Cargill plans to store all the water that leaks from the mineshaft in the mine itself. However, if the volume of water is large enough, any unsaturated brine will erode the mine support pillars, jeopardizing mine safety--especially if a fire, explosion, earthquake, or pipe or dam failure occurs. Secondly, the presence of fluid storage areas within the mine raises ambient humidity levels. Higher humidity in the mine increase rates of salt creep[3], pillar yield and room closure. Increasing rates of room closure tend to foreshadow ceiling collapses and progressive collapse of rock layers between the mine and any bodies of water located above the mine.
Decommissioning
Cargill should publicly disclose their plans for eventual mine closure, which should account for potential adverse effects. A Cargill executive has stated that when it comes time to abandon the mine (paraphrasing) “We will probably flood the mine to create hydrostatic pressure.” However, Raymond Vaughan, a geologist familiar with the Akzo Nobel’s Retsof mine failure , writes that “…salt mine flooding, whether intentional or inadvertent, is pretty much “game over” for successful containment or control of the salinity associated with the brine that will inevitably be squeezed out of the mine.”
He also writes, “In the worst case, of course, there would be a relatively open upward pathway due to a collapse, as in the case of the Akzo mine.”
At Retsof as much as 70 feet of subsidence occurred at the largest sinkhole at the surface. Flooding of Cayuga mine—whether accidental or intentional—will create a reservoir of saturated brine that will be 7.5 times as saline as sea water. The flooding will cause a certain amount of pillar dissolution and weakening. This weakening in turn could result in the sort of seismic subsidence event that occurred at Retsof--resulting in hydraulic connectivity with both the overlying brine aquifer and with Cayuga Lake. If this happens, brine could gradually or suddenly discharge into the lake as trough subsidence along the length of the lake forces the brine out of both the mined spaces and the overlying brine aquifer.
Vaughan writes:
In my opinion, the brine will find outward pathways from the mine and will flow through these pathways at less-than-lithostatic pressure. It’s also likely, in my opinion, that any closed salt mine in the northeastern U.S. and adjacent Canada will eventually flood, if not already intentionally flooded. Thus, for any closed salt mine, I foresee no successful containment or control of the salinity associated with the brine that will inevitably be squeezed out of the mine. The impacts will be faster if there’s a collapse-induced pathway, or slower otherwise, but in any case there should be a good-faith effort to figure out where the salt will end up. Will it migrate into aquifers and/or surface water bodies such as Cayuga Lake or Lake Erie?[4]
In other words, even if Cargill stopped mining under Cayuga Lake today, residents of Tompkins, Seneca, and Cayuga Counties and all the downstream stakeholders who rely on fresh water, could be facing immense and possibly intractable threats to a very significant portion of our freshwater assets.
Examples from Dr. Warren’s report suggest that the worst-case scenario, resulting from such subsidence and brine discharge into the lake would be a geologically unstable shoreline, the sinking of roads and buildings, the death of aquatic life, and non-potable lake water. The public should be involved in discussing the future of Cayuga Mine and our lake.
Improper Segmentation
Cargill egregiously misled the public and the DEC in its application to mine an additional 150 acres needed to accommodate a 2-mile tunnel to where Shaft 4 would be built. DEC’s Environmental Notice Bulletin for 4/8/15 states, “The reviewed Life of Mine (LOM) expansion area is 150.3 acres, and there are no other proposed changes to the currently permitted operation. All activities associated with this modification will take place underground, and there will be no additional surface development associated with this proposal” (emphasis added).
Yet the mining of a two-mile passage southeastward through that 150.3 acre extension is essential for Cargill to connect Shaft #4 with its northern mining reserves under the lake.In other words, it is very much connected to surface developments.
Cargill’s disingenuous and improperly segmented application violates both the spirit and the letter of DEC’s SEQR process. This breach should be reason enough to require a DEIS and a public hearing. In such a hearing DEC should correct Cargill’s improper application process by recombining Cargill’s improperly segmented permit application so that matters having to do with the future mining of the northern reserves for which Shaft 4 is essential will all be considered in the proper deliberative process. DEC should rescind its 2015 negative declaration for Cargill’s 150.3 acre expansion pending the results of this holistic EIS process.
One likely reason for the segmentation is that gross revenues from the sale of salt from the additional150 acres of minable reserves could well exceed the cost of the entire Shaft 4 project, which is reportedly $47M. Presumably, the Empire State Development Fund would not look favorably on a request for an $8M subsidy if the fund’s directors understood that this Cargill project may actually be self-financing.
Another reason may be that the DEC has raised the question with Cargill as to whether Cargill’s plans to store several million gallons of waters leaking from Shaft 4 in the mine may adversely increase humidity levels in the mine. Segmentation is a means to prevent difficult questions from being raised.
And, thirdly, the construction of Shaft 4 will give Cargill the ability to mine further to the north for another thirty years. Such mining would go further into areas with thinner and thinner bedrock separation when at Milliken Point it appears that Cargill will already be operating with less bedrock separation than existed at Retsof Mine. Only by segmenting the project into two pieces, an innocuous expansion of mining area by a minor amount and a “potential future air shaft” could Cargill be able to argue that these were two separate projects. And, by the time the public became aware of the project on the surface, it would be too late to comment on any adverse impacts that Shaft 4 might have regarding mine stability and safety.
Request
The public needs more disclosure of any and all risks associated with the construction of the proposed new shaft and the immense amount of northward mining under the lake that would be need to take place to amortize this $47M in new investment. The best way to assure protection of the environment and lake safety in this project is to have a fully-informed public discussion of both permit applications together. A DEIS and a public hearing are essential to this public process. Cayuga Lake and the waterways it connects to are too valuable to be put at risk by a cursory regulatory process that issues “negative declarations” under SEQR at every step of the way.
The public needs more disclosure, not only of any and all risks associated with the construction of the proposed new shaft, but also disclosure about the risks associated with the additional thirty-plus years of mining under the lake that the shaft would enable within the problematic northern reserves.
Thank you in advance for urging the DEC to require Cargill to carry out a DEIS.
1
[1]The New York State Assembly Standing Committee on Environmental Conservation / Standing Committee on Agriculture. 1995. In the Matter of a Joint Public Hearing on Underground Mining in New York State. Volume I. 344 pages.
[2]We annualized gas production based on this statement on page 2 of RESPEC’s 2013 report, Cargill De-icing Technology Lansing Mine, Corehole #18 Stratigraphic Test Hole, Installation and Data Collection, “The estimated gas production rate was 13,300 cubic feet per day (cfd).”However, it is possible that this daily production rate could be intermittent rather than a sustained rate of release.
[3]Salt moves slowly (creep) under large pressure differences. “Room closure” refers to the inevitable movement of ceiling and floor toward each other in salt mines. Reportedly, Cargillabandoned gathering room closure information in the eastern section of Cayuga Mine in 2008 due to access issues.
[4]Personal e-mail received on 4 December 2016.