2019-05-31_REVISION - M1977004 - Laserfiche WebLink

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Mr. Dustin Czapla Page 3 of 7 • Advancement of 25 characterization boreholes and reagent injection/monitoring wells within the former Pinnacle Mine Dump boundary (Figure 3) in a phased approach between 2019 and 2021. Elevated uranium concentrations were identified in this area during 2018 characterization activities. o In 2019, up to five characterization boreholes will be advanced. Up to three of the boreholes may be converted into injection/recirculation/monitoring wells. o In subsequent years (tentatively planned for 2020 and 2021), additional drilling will be conducted in this area, including installation of up to 20 characterization boreholes and conversion of up to 12 of the boreholes into injection/recirculation/monitoring wells. • Expanded phosphate-based injections into the Indian Rock Dump. Associated activities will include the installation of piping to connect the newly installed Pinnacle Mine Dump wells to the treatment systems installed in 2017. • Continued operation of the phosphate injection system at the underground mine workings and the engineered treatment cells constructed in 2018 to treat water emanating from the Chester Fault springs (Figure 3). • Implementation of active management strategies, should they become necessary, to control "treatment residuals" (i.e., residual dissolved constituents present in water resulting from reagent usage) in surface water upstream of the CDPS permit outfall (SW-33). In particular, residual phosphate in surface water resulting from phosphate injections will be managed if needed. The following sections provide the proposed work to be conducted to support alternatives advancement and design, and information on reclamation of disturbed areas following LPL implementation. Additional details associated with prior field work is provided in the 2016 Alternatives Analysis Report, submitted to the Water Quality Control Division, the U.S. Environmental Protection Agency, and DRMS on December 6, 2016 (Arcadis 2016). In advance of the uranium load reduction field work, approvals will also be requested from the Colorado Department of Public Health and Environment (CDPHE) Water Quality Control Division as required by the CDPS permit, the CDPHE Radiation Management Program (RMP) as required by the site Radioactive Materials License (RML), and the United States Environmental Protection Agency for Class V aquifer remediation injection well "authorization by rule" in accordance with Title 40 Code of Federal Regulations (40 CFR) Sections 144.24 and 144.84(a). Monitoring Well Construction and Borehole Advancement Advancement of up to 25 characterization boreholes are proposed at the Pitch Reclamation Project in a 3-phased approach starting in 2019. The purpose of the boreholes is to characterize solid materials and assess the area for of the potential for subsurface water. Based on the screening results, boreholes may be converted to wells for use in the injection, recirculation, and/or monitoring of phosphate-based reagents and conservative tracer(s) at the Site. HOMESTAKE MINING COMPANY '. 1 1 2 MARSHALL STREET, SARGENTS, COLORADO a 1 248