2007-04-20_REPORT - M1977004 - Laserfiche WebLink

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Pitch Reclamation Project Colorado Mined • Land Reclamation Board 2006 Annual Reclamation Report 4.2 Inclinometer Evaluation Three (3) inclinometers were installed in October 1998 (198-1, 198-2, and 198-3) to monitor any subsurface movement within the south and east walls of the North Pit. Inclinometer 198-1 is located on the lowest bench on the South Wall; 198-2 is located on the 10,600 ft. bench of the South Wall and; 198-3 is located above the crest of the East Wall. Data collected in 1999 through 2006 from all three inclinometers indicate little to no subsurface slope movement (less than 0.3 ft/year) and is consistent with the surface monument survey data. This movement is within the instrument error for the inclinometer probe of + 0.3 inches per 100 ft. of depth. Homestake will continue to monitor these three inclinometers at a minimum of every two years unless surface monuments detect increasing slope movement. Two temporary inclinometers were installed in Piezometers P-8 and P-10 during the winter of 1997-1998 to provide data in the spring of 1998. These inclinometers were made redundant by the installation of inclinometers 198-1, 198-2, and 198-3. The inclinometers in P-8 and P-10 remain installed, but are not surveyed on a regular • basis. Should surface monuments detect increasing slope movement, data could be collected from these combination piezometerslinclinometers. 4.3 Pinnacle Mine Workings Monitoring A concrete plug was constructed in the Pinnacle Adit in September 1995. Authorization for the placement of the Pinnacle Adit plug was requested by Homestake in Aprii 1995, through Technical Revision #4 (TR4) -Pinnacle Adit Closure, Pitch Project, Technical Revision for Permit #77-4HR (Golder Associates, Inc.). Conditional approval of the Technical Revision request was granted by the Colorado -Division of Minerals and Geology in a letter dated May 26, 1995. The intention of the plug was to partially seal the Pinnacle Adit and allow the area around the mine workings to resaturate. The resaturation of the workings was predicted to re-establish a geochemically reducing environment and lower the solubility of uranium and radium within the underground workings of the Pinnacle Mine. The Division's approval of TR4 required Homestake to monitor the effects of resaturation in the Pinnacle workings for five years or until hydrologic conditions stabilized. Components in the Monitoring Plan outlined in TR4 (Section 4.0), included continuation of discharge water quality monitoring at the POC (SW-33), monitoring of groundwater resaturation levels, annual spring and seep surveys in • areas down-gradient from Pinnacle workings, and monitoring for changes in water 12