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Memo <br />To: Tony Waldron, Eric Scott <br />From: Robert Hillegas <br />Date: October 4, 2017 <br />Re: Interim Narrative Standard for Groundwater Standards and Climax Groundwater Data <br />Introduction <br />Regulation 41, the Basic Standards for Ground Water, provides the basis for groundwater <br />standards to implementing agencies, such as the Division of Reclamation, Mining and Safety <br />(DRMS), to interpret the Interim Narrative Standard for groundwater. The Interim Narrative <br />Standard (Reg. 41.5(C)(6)) is defined as either the numeric standards in the regulation or the <br />ambient groundwater quality as of January 31, 1994. The regulation allows for an implementing <br />agency to determine if the numeric standard or the ambient groundwater quality as of January <br />31, 1994 is the most appropriate threshold in setting compliance points for regulated activities. <br />Regulation 41.5(C)(6)(b)(iii) states: <br />In applying this interim narrative standard, the Commission intends that <br />agencies with authority to implement this standard will exercise their best <br />professional judgment as to what constitutes adequate information to <br />determine or estimate existing ambient quality, taking into account the <br />location, sampling date, and quality of all available data. Data generated <br />subsequent to January 31, 1994, shall be presumed to be representative <br />of existing quality as of January 31, 1994, if the available information <br />indicates that there have been no new or increased sources of <br />groundwater contamination initiated in the area in question subsequent to <br />that date. If available information is not adequate to otherwise determine <br />or estimate existing ambient quality as of January 31, 1994, such ground <br />water quality for each parameter shall be assumed to be no worse that <br />the most stringent levels provided for in Tables 1 through 4 of "The Basic <br />Standards for Ground Water," unless the Commission has adopted <br />alternative numerical standards for a given specified area. <br />Whereas the implementing authority for Regulation 41 groundwater standards lies with the <br />DRMS, the Water Quality Control Division (WQCD) provides assistance in interpreting <br />groundwater quality data. This memo is intended to memorialize WQCD's analysis of <br />groundwater data provided by Climax. <br />