2016-12-01_PERMIT FILE - C1980007A

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HYDROLOGIC CHARACTERIZATION AND MONITORING PLAN 12 4.0 COMPREHENSIVE HYDROLOGIC MONITORING PLAN The MCC hydrologic monitoring program is designed to collect the monitoring data needed to assess mining -related impacts on hydrologic resources. CDRMS approved a revised hydrologic monitoring plan for MCC in October 2016 (CDRMS, 2016). A description of the revised monitoring plan, effective WY 2017, is presented in the following sections. The hydrologic monitoring plan for the permit area includes monitoring surface water resources, springs and seeps, groundwater resources, the coal refuse pile underdrains, and pertinent mine water sites. Routine monitoring, i.e. monitoring done subsequent to the baseline monitoring period, includes collecting field water quality data (pH, electrical conductivity [EC], and temperature) and collecting a sample for independent laboratory analysis annually. Flow or water level measurements are collected three times per year corresponding with the rising limb period, between April 3rd and May 13th; the peak flow period, between April 21" and June 26th; and the low flow period, between July 10th and October 8th, as shown on Table 5. The hydrologic monitoring plan for MCC incorporates a separate baseline monitoring schedule for potential new monitoring sites for approximately one year prior to the time when mine development operations expand into new possibly affected areas. The baseline monitoring schedule protocols specify collecting monthly field water quality data, flow or water level measurements, and collecting samples for laboratory analysis for the year prior to initiation of mining and potential impacts (Table 5). Site-specific baseline schedules are dependent on site accessibility and mine development timing. In general, baseline monitoring is conducted for at least six consecutive months, usually from April through September, in order to provide adequate data to show seasonal variations in water quality and quantity. Winter access to most sites within the MCC permit area is impractical and not feasible, so baseline monthly monitoring is generally not performed from October through March. A summary of the approved baseline and routine monitoring program frequencies is presented in Table 5. The chemical analyte suite for the first five years of sampling for both groundwater and surface water samples, including one year of baseline sampling, is presented in Table 6. After monitoring sites have been monitored for five years (including approximately one year of baseline monitoring), the analytical parameter suite list is reduced and samples are submitted for laboratory analysis of total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC), pH, dissolved iron, and total iron. Field parameters (pH, EC, temperature, and flow or water level) are also recorded. The Upper and Lower North Fork and Middle Sylvester Gulch monitoring sites have expanded analytical parameter suite lists, in order to provide data for the on-going characterization of the North Fork. The North Fork and Middle Sylvester Gulch lab parameters include those listed in Table 6, plus chromium, nickel, silver (total), cyanide (total), iron (total recoverable), alkalinity (total CaCOA bicarbonate, carbonate, hydroxide, nitrogen (ammonia), ortho-phosphorus (dissolved), and sodium adsorption ratio (SAR). Revised 09/07- PR12; 08/16- TR139 MydroGeo, Inc