Laserfiche WebLink
The request for Major Permit Modification No. 9 included three elements: <br />UIC Permit Modification Request that provided suggested language of the various sections to <br />be modified, including a new section relating to the Temporary Suspension Of Mining <br />Operations; <br />Revised Subsidence Plan, dated August 2004, to replace the original Subsidence Plan and <br />include modification of the requirements for Time Domain Reflectometry (TDR); and <br />Revised Ground Water, Surface Water, and Process Monitoring Plan dated September 2004, <br />to include a reduction in the number of monitoring parameters. <br />The EPA has reviewed the above mentioned material and is proposing to modify the Permit as <br />described in this Draft addendum to the Statement of Basis. The following three sections I, II and III <br />provide the rationale for modifications to the Permit. These changes include the replacement of Revised <br />Ground Water, Surface Water, and Process Monitoring Plan (Appendix I) and the Subsidence Monitoring <br />Plan (Appendix J). Background information, original Permit language and proposed changes are <br />discussed below. <br />I. Subsidence Monitoring • Background and Proposed Modifications <br />At the time the UIC permit was issued, American Soda developed a subsidence monitoring plan <br />with input from the BLM, EPA, and CDMG. The subsidence monitoring plan was incorporated into the <br />EPA UIC permit as Appendix J. Several original monitoring measures have not provided the intended <br />information and benefits, and because those measures are ineffective and costly American Soda has <br />requested modification of those elements. The primary elements of concern are related to Time Domain <br />Reflectometry (TDR) monitoring and gamma logging at certain production levels from each cavity. <br />a) Time Domain Reflectometry Monitoring: The existing subsidence monitoring plan calls for <br />the installation of TDR cables in the first 23 of 26 wells in the initial mining panel. The subsidence <br />monitoring plan acknowledged uncertainty about the performance of TDR systems in this application and <br />anticipated evaluating its performance before a final monitoring approach was selected for future mining <br />areas. <br />To date, TDR systems have been installed in all of the 27 existing wells. The TDR systems have <br />failed in every well in which they have been installed. Heat generated in the well bore during mining and <br />water infiltration into the cables from surrounding aquifers are the primary reasons. for the failures. At <br />this point, TDR has been demonstrated to be technically infeasible in this application. Two options for <br />modification are considered: <br />1) Eliminate TDR monitoring; or <br />2) Install TDR after mining is complete as part of the Plugging and Abandonment procedure. <br />This would minimize the potential for heat associated with active mining to affect the <br />TDR system. <br />American Soda previously proposed installing TDR in We1120-12 and testing the viability of the <br />TDR technology in apost-mining application. Minor Modification No. 8 of the permit addressed the use <br />FINAL Addendum to SOB For Modification No. 9, UIC Area Permit No. C030858-00000 Page 2 of 29 <br />