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RULE 4 PERFORMANCE STANDARDS <br /> <br />Rule 4 Performance Standards 4-18 Revision Date: 4/29/19 <br /> Revision No.: MR-201 <br /> <br />Conclusions <br /> <br />The Colowyo Mine has no single or multiple continuous geologic units in the mine that <br />contains ground water under unconfined or confined conditions. The only ground water <br />encountered is the discontinuous perched pockets of ground water. This lack of ground <br />water, except for discontinuous perched ground water pockets, encountered during mining <br />precludes the necessity to monitor ground water on a ridge top. <br /> <br />4.05.13 Surface and Groundwater Monitoring <br /> <br />The current monitoring program can be found in Section 4.05.13 in Volume 15. <br /> <br />The evolution of the Surface and Groundwater Monitoring Plan is as follows (retained for <br />historical information): <br /> <br /> In a letter to the Division dated May 2, 1983 Colowyo submitted the surface and <br />groundwater monitoring plan, which was subsequently approved by the Division on May <br />6, 1983. A copy of the letter is enclosed on pages 4.05-11 through 4.05-14. <br /> <br /> Page 4.05-15 further -explains changes to the Surface and Groundwater Monitoring Plan. <br /> <br /> Exhibit 18, Revisions for Second Five-Year Term, shows a Minor Revision, “Modification <br />of Groundwater Monitoring”, approved August 1989. <br /> <br /> Exhibit 7, Hydrology Information, details the “Modification of both Surface Water <br />Monitoring and Alluvial Groundwater Monitoring Locations, 1991”. <br /> <br /> Map 10B, Water Monitoring Sites for Permit No. CO-019-81 shows updated well <br />locations, surface water locations, and NPDES discharge points. <br /> <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 <br />noted in future Annual Reclamation/Annual Hydrology Reports.