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prepared by the BLM nor the EPA Statement of Basis offers adequate support for this argument. The DMG must either demand the thorough disclosure and analysis fairly required of a Designated Mining Operation, or deny the permit application. We have thus far described two broad issues, the monitoring plan and the EPP response on toxic materials, with related details. These issues are joined by a third issue, which is the means of monitoring for subsurface subsidence. As we noted in our letter of May 17, 1999, the permit applicant has an obligation to show that it will meet its statutory duty to prevent disturbances to the prevailing hydrologic balance, and to protect the quality and quantity of water in groundwater systems. Setting aside the admitted inadequacy of the groundwater baseline, the proposed monitoring program has not improved with American Soda's most recent submissions to the DMG. American Soda's adequacy response, pg. 3 comment 5 shows how grossly inadequate the subsurface subsidence monitoring plan is. Comment 5 begins: "Because nacholite occupies only 25 to 30% of the bulk volume of rock formation being mined, dissolution and removal of the nacholite does not create a void." If [his is the case, then American Soda's proposal to blanket the solution mining cavities with an inert gas to protect the upper aquifers and cavity integrity is not possible. In order to cap a solution mining cavity with gas, there must be a distinct cavity which allows you to develop agas/liquid interface. Without a void, the necessary cavity for gas won't exist, which raises the question of how the upper aquifers will be protected from the solution mining cavities. American Soda goes o^ to say: "American Soda will conduct an evaluation of current technologies and methods to characterize cavity shape. If a technology or method is found that has a high probability of success, it will be tested for application in American Soda's operation. The shape of the cavity is predicted to be near cylindrical, with an anticipated maximum height of about 650 feet and an anticipated maximum diameter of 200 feet." On numerous occasions we have suggested to the DMG that the use of seismic testing be required. 3-D Seismic testing will not only chazacterize the development of well activity, it will also determine if a breach of any aquifer occurred either via solution mining or via subsidence. Thus, at all times, the operator and the regulators would have a full understanding of the progress of solution mining process. Another advantage of 3-D seismic is that it allows one to characterize a large field or in the case of American Soda, an entire 5 year panel. At General Chemical, we conducted seismic on a 332 acre brine field. The 3-D seismic allows one to characterize size and shape of the cavity, whether or not there is communication between cavities, where subsidence has occurred and more. This is all the information that an agency should request of American Soda if indeed impact to water quality is a concern. 3-D seismic is the most proven accurate form of subterranean chazacterization commonly employed. Consistent with our views about the establishment of baseline, American Soda should conduct a baseline 3-D seismic on their proposed 5-year panel before operations begin. The 3- Dseismic should then be performed at least yeazly. All information derived from 3-D seismic would be run through a computer model to generate an image of the ac[ual below ground