Minntac Tailings Basin - Proposed WQ Permit Compliance Points Dark CR 668 GW014 Headwater of Dark River or Seep GW013 GW012 Little Sandy Lake Inlet Admiral Lake Proposed Boundary MW Timber Creek

Identified Parameters of Concern Minntac Tailings Basin Groundwater & Drinking Water (trout) Industrial Consumption Agric. and WildlifeObserved Concentrations Parameters of ConcernClass 1 Secondary Drinking Water Standard Class 3B (trout) Class 3C Class 4A (irrig. And wild rice) Class 4B (livestock and wildlife) GW012 Dark CR668 Sand River / Twin Lakes (Twin 1-Sept 2013) Bicarbonates (HCO3 as CaCO3) 250 mg/L N/A Fluoride 4.0 mg/L2.0 mg/L NM8.67 (seep)N/A Hardness (Ca+Mg as CaCO3) 250 mg/L500 mg/L N/A1430NM Specific Conductance 1000 uS N/A Sulfate 250 mg/L 10 mg/L1000 mg/L TDS 500 mg/L 700 mg/L

Potential Analytes in GW and SW Classes

Minntac Tailings Basin Presumed Water Quality Compliance Limits for Permit Reissuance as of 10/21/2013 West Surface WaterEast Surface WaterGroundwater Parameter Dark River Origin Dark River CR668 Dark River (trout) Timber CreekAdmiral Lake Sand River - L. Sandy Lk. GW012GW013GW014GW-Prop Bicarbonate (HCO3 as CaCO3) 250 N/A Hardness (Mg + Ca as CaCO3) N/A Specific Conductance (uS/cm) 1000 N/A Sulfate (mg/L) TDS (mg/L) Fluoride (mg/L)N/A Iron (mg/L) TSS (mg/L) 30 N/A Ammoniaunkown N/A Phosphorusunkown N/A Metalsunkown Surface water limits are the applicable usage class Water Quality Standards since the stream's headwaters are at the tailings basin and receive tailings-impacted baseflow as their main source Sulfate limits for West Surface Water assume Dark River is not deemed "Wild Rice Production Water" Final permit limits will be established based on review by Effluents Limit Staff of monitoring data to be collected and submitted by permittee