2012-10-01_REVISION - M1977310 (10)

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JD -6 Mine Environmental Protection Plan 13 5.4 Environmental Protection Evaluation The SPLP testing (Section 5.3.3.3) identified three constituents in waste rock as a constituent of potential concern (COPC) at the JD -6 Mine based on SPLP leachate concentrations exceeding groundwater standards. These constituents are listed in Table 7 and are described individually in Section 5.4.1, below. The potential for transport to groundwater is discussed in Section 5.4.2. Since no ore will be stored at the surface at the JD -6 Mine, no constituents in the underground ore are considered to be COPCs at the JD -6 Mine. Table 7. Constituents of Potential Concern in JD -6 Waste Rock Pile Parameter Gross alpha (pCi /L) Sulfate TDS Vanadium Waste Rock SPLP JD-6-WRP 52.7 746 D 1,150 0.5 Notes HHS = Human health standard DW = Drinking water standard - -- = Constituent did not exceed standards shown CO = Colorado standard, no federal drinking water standard exists for molybdenum Water Quality Standards Federal Federal Groundwater MCL SMCL Agricultural (Colorado (Colorado Standards HHS) DW Table 2) 15 250 500 01 5.4.1 COPC Chemistry and Occurrence in the Environment 5.4.1.1 Sulfate JD -6 Mine underground waste rock SPLP results exceeded secondary standards for sulfate concentrations by a factor of three. Sulfate concentrations in SPLP leachates from composite samples of ore from the nearby JD -8 Mine exceeded secondary standards by a factor of four. Sulfate is ubiquitous in groundwater in the Paradox Valley. Golder (2009) found that groundwater at the Hermosa/Chinle contact in the Paradox Valley had sulfate concentrations ranging from 1,070 to 1,810 mg /L. These values for naturally occurring sulfate in groundwater are higher than the SPLP leachate concentrations in waste rock from the JD -6 Mine and ore from the JD -8 Mine. SMCLs are non - mandatory, non - enforceable water quality standards that are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL (EPA, 2012). 5.4.1.2 Total Dissolved Solids JD -6 Mine underground waste rock SPLP total dissolved solids (TDS) results exceeded secondary standards by a factor of two. TDS in SPLP leachates from composite samples of ore from the adjacent JD- 8 Mine exceeded secondary standards by a factor of one to four. The federal standard of 500 mg /L is a secondary water quality standard based on a palatability (taste) of drinking water. SMCLs are non - mandatory, non - enforceable water quality standards that are established only as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color and odor. These contaminants are not considered to present a risk to human health at the SMCL (EPA, 2012). TDS is naturally high in groundwater throughout the Paradox Basin and elsewhere in the arid west. Golder (2009) found that total dissolved solids (TDS) in groundwater at the contact of the Moenkopi /Chinle had TDS concentrations between 590 and 1,030 mg /L, while groundwater near the Hermosa/Chinle contact had 4148A.120927 Whetstone Associates •