2018-11-15_HYDROLOGY - M1980244 (6)

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In its August 2019 request,DRMS indicated that: "The 'Interim Narrative Standard' in 41.5(C)(6)(b)(i) below [in the letter] is applicable to all groundwater, to which standards have not already been assigned in the state... Until such time as use classifications and numerical standards are adopted for the groundwater on a site-specific basis throughout the state, and subject to the provisions of subsection (ii) below [in the letter], groundwater quality shall be maintained for each parameter at whichever of the following is less restrictive: (A) Existing ambient quality as of January 31, 1994, or (B) That quality which meets the most stringent criteria set forth in Tables I through 4 of `The Basic Standards for Ground Water"' In Regulation 41, Section 41.5 (c)6)(b)(iii) the WQCC stated its intent regarding the application of the Interim Narrative Standard by implementing agencies including the DRMS: "In applying this narrative standard, the Commission intends that agencies with authority to implement this standard will exercise their best professional judgment as to what constitutes adequate information to determine or estimate existing ambient quality, taking into account the location, sampling date, and quality of all available data. Data generated subsequent to January 31, 1994, shall be presumed to be representative of existing quality as of January 31, 1994, if the available information indicates that there have been no new or increased sources of groundwater contamination initiated in the area in question subsequent to that date. If available information is not adequate to otherwise determine or estimate existing ambient quality as of January 31, 1994, such groundwater quality for each parameter shall be assumed to be no worse than the most stringent level provided for in Tables I through 4 of "The Basic Standards for Ground Water," unless the Commission has adopted alternative numerical standards for a given specific area." In essence, if CC&V has sufficient water quality data to determine or estimate the existing ambient water quality as of January 31, 1994 these data must be used to establish the NPLs. If data are not adequate to determine or estimate the water quality as of 31 January 1994, item B above applies. DRMS asserted in its December 2016 letter: "If an operator wishes to propose a groundwater standard less restrictive than those contained in 'The Basic Standards for Ground Water' tables, it will be the operator's burden to sufficiently demonstrate to DRMS that their circumstances meet at least one of the two conditions outlined below[in the letter], thereby allowing DRMS to apply a less restrictive standard, and still fully implement the requirements of Regulation No. 41." The first narrow circumstance and authority for DRMS to apply a groundwater quality standard that is less restrictive than the Table Value Standards at a Point of Compliance exists when a mine operator provides DRMS with adequate documentation and data to determine, to the satisfaction of DRMS, that the existing ambient groundwater quality on January 31, 1994 was above the Table Value Standard." Only two of the drainages under review have analytical data prior to January 31, 1994: Arequa Gulch (two samples)and Wilson Creek(thirty samples). In this situation,the DRMS letter asserted: "The second narrow circumstance and authority for DRMS to apply a groundwater quality standard less restrictive than the Table Value Standard is when an operator provides DRMS with 2