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EME"D ' HOM FEB 202019 ES AYaE x-� UVWN0FW1CLAW 1 Colorado Department of Natural Resources February 19, 2019 ' Division of Reclamation, Mining and Safety Attention: Mineral Division 1313 Sherman Street, Room 215 Denver, CO 80203 RE: HOMESTAKE PITCH RECLAMATION PROJECT ' 2018 ANNUAL GEOTECHNICAL REPORT (MM-19�HR) ' Dear Division: Attached is the 2018 Annual Geotechnical Report for the waste rock management areas at the Homestake Mining Company Pitch Reclamation Project(Figure 1). The purpose of this report is to provide the results of ongoing geotechnical monitoring of the Indian and Tie Camp rock dumps at the Pitch Reclamation Project (Figure 2). The history of the rock dumps has been ' provided in previous annual geotechnical reports and is not repeated here. The Indian and Tie Camp rock dump piezometer water level readings are presented in this report. The 2018 water level measurements are provided in Table 1. Water level data collected since 1996 are shown on Figure 3. As reflected on Figure 3, the water levels in rock dump piezometers show little fluctuation in the fall and winter months, with a temporary rise in response to the spring snow melt or summer rain events. The extent that water levels rise each ' year depends on the fluctuation in snow pack and summer precipitation, and the location of the piezometers within the rock dumps. The onsite precipitation gage recorded 13 inches of precipitation during the 2018 monitoring period (November 2017 through October 2018), ' compared with 20 and 21 inches during the 2016 and 2017 periods, respectively. Precipitation data from 2017 and 2018 is shown in Figure 4. The project experienced a change in the site closure manager in January 2018. Dale Davis retired, and I was his replacement as of February. As a result of the change, the water level measurements in the rock dump piezometers were not documented until May, and intermittently thereafter. As a result, only data from high-flow' and l0w-flow2 monitoring events are used in this ' report. In 2019, transducers will be installed in all of the piezometers to facilitate more frequent water level measurements and to reduce health and safety risks associated with collecting manual water level measurements during the winter months. Inclinometers will continue to be ' monitored in 2019. In 2018, five piezometers at the 10300 level (RD-06, RD-07, RD-08, RD-09, IC-10300R)were used in combination with five shallow piezometers at the toe of the Indian Rock Dump (RD-01, ' RD-02, RD-03, RD-04, RD-05) to facilitate large-scale in situ source zone treatment of uranium, with extraction from four of the five piezometers at the toe of the Indian Rock Dump and ' ' high-flow monitoring typically occurs in late May of each year 2 low-flow monitoring typically occurs in early October of each year Pitch Reclamation Project 2018 Annual Geotechnical Report M-1977-004HR