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STATE OF COLORADO. DIVISION OF MINERALS AND GEOLOGY Department of Natural Resources 7313 Sherman St., Room 215 Denver, Colorado 80203 Phone: (303) 866-3567 FAX: (303) 832-8106 DATE: February 3, 2004 TO: Sandy Brown and Mike ulay FROM: Dan Mathews RE: 2002 and 2003 Water Year Annual Hydrology Reports Seneca II-W Mine, Permit No. C-1982-057 I have completed an initial review of both the 2002 and 2003 AHR's for the Seneca II-W Mine. In general, the reports appear to be thorough and comprehensive. Monitoring appears to have been conducted in compliance with permit specified schedules at approved sites, and for required parameters. Data summarization, presentation, and narrative evaluation of .conformance with PHC projections appears to be adequate, with a few exceptions as noted below. In addition to the AHR review, I also looked closely at PHC sections of the permit relative to AVF material damage assessment, and found certain potentially serious flaws in the projections associated with subirrigated alluvial valley floor pastures on Dry Creek. 2002 AHR ~~ COLORADO DIVISION O P MINERALS GEOLOGY 0.EC LAMATION•MINING sAFETY•SCIEN CE Bill Owens Governor Greg E. Walther Executive Director Ronald W. Cattany Division Director Natural Resource Trustee For various reasons my review of the 2002 AHR was delayed until late December 2003. The only potential issues of concern I noted were in regard to certain wells where observed annual average TDS values exceeded PHC projections (WHAL7-2, WOV17, and WW14-. I would like Mike to consider the operator's explanation for these exceedances, and advise as to whether PHC revisions or other measures appear to be warranted. 2003 AHR There are several items of note in the.2003 AMR, which I would ask Mike to consider and comment on, as a part of his review of the report for PHC conformance. Well TDS values that exceeded PHC projections as noted in 2002 AHR (WHAL7-2, WOV17, WW14). Are PHC revisions or other measures warranted? A number of wells were damaged and rendered inoperable this year, and additional wells ware abandoned for other reasons. WSOV24, WSC 24, WWCOV24, WWCOV24, WWC24, and WWCU24 installations were located between Pond 016 and new Pond 016A. All of these wells were damaged by ground movement in April 2003, and operator's efforts to seal the wells have not been successful. Operator indicates in the AHR that replacement wells will be drilled in 2004. Wells WOV4-1 and WOV4-2 were both abandoned in August 2003. Operator indicates that one replacement well will be drilled in 2004. Office of Office of Colorado Mined Land Reclamation Active and InaRive Mines Geological Survey