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RULE 4 PERFORMANCE STANDARDS <br />Conclusions <br />The Colowyo Mine has no single or multiple continuous geologic units in the mine that contains <br />ground water under unconfined or confined conditions. The only ground water encountered is the <br />discontinuous perched pockets of ground water. This lack of ground water, except for <br />discontinuous perched ground water pockets, encountered during mining precludes the necessity <br />to monitor ground water on a ridge top. <br />4.05.13 Surface and Groundwater Monitoring <br />The current monitoring program can be found in Section 4.05.13 in Volume 15. <br />The evolution of the Surface and Groundwater Monitoring Plan is as follows (retained for historical <br />information): <br />• In a letter to the Division dated May 2, 1983 Colowyo submitted the surface and groundwater <br />monitoring plan, which was subsequently approved by the Division on May 6, 1983. A copy of <br />the letter is enclosed on pages 4.05-11 through 4.05-14. <br />• Page 4.05-15 further -explains changes to the Surface and Groundwater Monitoring Plan. <br />• Exhibit 18, Revisions for Second Five -Year Term, shows a Minor Revision, "Modification of <br />Groundwater Monitoring", approved August 1989. <br />• Exhibit 7, Hydrology Information, details the "Modification of both Surface Water Monitoring <br />and Alluvial Groundwater Monitoring Locations, 1991 ". <br />• Map IOB, Water Monitoring Sites for Permit No. CO -019-81 shows updated well locations, <br />surface water locations, and NPDES discharge points. <br />• Starting in early 1996 sampling procedures for groundwater wells was changed from total <br />recoverable metals to total dissolved metals. This sampling procedure modification will be noted <br />in future Annual Reclamation/Annual Hydrology Reports. <br />Rule 4 Performance Standards 4-15 Revision Date: 1/31/18 <br />Revision No.: TR -119 <br />