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Colowyo, 01981 -019, PR3 adequacy No. 3 30 July 22, 2011 <br />The response is adequate. <br />3. In the groundwater lab parameter table in Section 4.05.13, please change the analysis for iron <br />from "total" to "dissolved ". Although DRMS Rule 2.04.7(1) specifies analysis for "total" 'iron <br />in baseline data collection, the standards for iron in the Basic Standards for Groundwater <br />(Colorado Water Quality Control Commission Rule 41) are for the "dissolved" concentration. <br />Response is adequate <br />4. DRMS proposes that well MLC -04 -Ol be established as an alluvial ground water point of <br />compliance, based on a) the probable discharges of spoil leachate to Collum Gulch after mining <br />is completed, and b) the discharges can be expected to have a high dissolved solids content <br />which could negatively impact the quality of alluvial ground water in Collum Gulch. The <br />leachate can be expected to have TDS concentrations greater than 3,000 mg/l, compared to <br />native alluvial ground water TDS generally less than 2,000 mg/I. <br />II'. as (CC', response sacs, Hell A- 1LC- 04 -0IC k Inappioju ime ti,r m1 allot dal !round ,1 Me, <br />poiut of congil lance 11CUW,e Ot possihlc u111Oe m11101- mioinc ingnncts. then plca'e 1•1111cr aJd <br />an udditionol Drell to the monitoring plan tort disrinuu;it i ug non- m [III ug impact >. or uopolc <br />anothel � ell as 1111 1111U\ 131 ground titter point of eonlpliuns. Oka Ietterol .April `. 11011 <br />explained the potential tort act IvItIcs proposed by 1'R-03 to ncgati vcl_Y impact the yOil] in of <br />.dlu1 dal ^romtd muter in (0110111 Gulch. Rule 4M3. 1 ',( I I(h) requires one or m0rc points of <br />cumpliauce Ihr nm co;d operation that. in the judgment otthe DID sion. has the potential t0 <br />negatively iutpact the quality of groundwater for which quality standards have been established <br />by the Colorado Water Quality Control Commission (CWQCC). Rule 4.05.13(I)(b)(i(A) <br />inquires a point of compliance for potentially impacted ground water that is subject to the <br />C WQC'C's standards. Collum Gulch alluvial ground water is subject to the Interiul Narrative <br />Standard of the Basic Standards for Ground Water. C'WQC'C Regulation 41 and, therefore, <br />needs a ground water point of compliance. <br />5. DBMS does not propose establishing a ground water point of compliance for bedrock <br />hydrostratigraphic units. DRMS is considering the need for a bedrock ground water monitoring <br />well or wells that would not be established as points of compliance. DBMS will complete its <br />review of the proposed hydrologic monitoring plan after receiving the requested calculations of <br />pitwall seepage and spoil spring discharges. <br />Rule 4.0511( 1 )(e) requires monitoring of ground water when surface mining activities may <br />atfect ground vcarer systems on or off the permit area. The discussion of probable hydrologic <br />consequences in the PR -03 submittal describes potential dewatering of bedrock units during <br />mining, and pussihlc migration of coal spoil leachate from pit backtill into duwndip bedrock <br />units after mining is amtpleted ( pitwtill seepage). Dewatering and leachate migration are <br />❑ffccts 1111 ground water systems on ur off the permit mroa; thcrctilrc. bedrock ground water <br />ni snoring is required under Rule 4.05.13(1 )(c). Please propose a bedrock monitoring well <br />that is properly located for detecting changes in ground vcater quantity and quality caused by <br />the dowatcring and leachate migration. <br />