2022-01-25_REPORT - M1983194 - Laserfiche WebLink

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1 Introduction This Environmental Monitoring Plan (EMP) was prepared for the Bureau of Land Management (BLM), Environmental Protection Agency (EPA) and the Colorado Division of Reclamation, Mining and Safety (DRMS) pursuant to federal and state requirements concerning the Natural Soda LLC (NS) nahcolite solution mining operations in Rio Blanco County, Colorado. NS operates, monitors, and reports in accordance with stipulations contained in the BLM Record of Decision (ROD), the EPA Area Underground Injection Control (UIC) Permits (permit numbers: CO30358-00000 and CO32169), the DRMS Permit M-1983-194, and any updated or subsequent conditions of approval and required mitigation. NS submits routine reports to the BLM, EPA and DRMS. The NS monitoring programs are intended to provide the Agencies with a means of determining the surface and subsurface environmental impacts of the NS operations. This EMP is designed to comply with the requirements set forth by the regulatory agencies. The Permits were approved for the operational life of the project. The mine has been successfully operating since 1993 without significant environmental issues. The regulatory agencies and NS continue to proceed on a phased approach based upon an updated Mine Plan, which provides more detailed information concerning current operations and operations anticipated in the near future. In addition, the Mine Plan provides general plans for long term operations. 2 Groundwater Monitoring Program 2.1 Groundwater Monitoring Wells Groundwater monitoring wells are established inside and outside of the area of well-field operations. Groundwater monitoring has been ongoing since the late 1980's with long term credible baseline conditions established for all active groundwater monitoring wells. The monitoring wells are completed within the following aquifers: Perched, A-Groove, B-Groove, and Dissolution Surface (DS). Figure 1 illustrates the location of the four aquifers of interest. Groundwater monitoring wells are located up-gradient and down-gradient from the solution- mining well field with respect to groundwater flow. These monitor wells provide a means to assess the impacts of mining operations by comparison of groundwater entering versus exiting the area stratigraphically above the solution-mining horizon. Figure 2 (Natural Soda LLC and Rock School Leases) and Figure 3 (Natural Soda LLC Plant Vicinity) depict the locations of the monitoring wells and the mining area. These figures will be periodically updated as monitor wells are either installed, converted, no longer needed, or plugged and abandoned (P&A). To establish a pre mining baseline, groundwater monitoring wells were established six months prior to the onset of mining. These wells were located immediately down-gradient of planned Daub&Associates, Inc. Page 1 Natural Soda LLC 2022 EMP