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Home My WebLink AboutDRC-2012-001697 - 0901a068802f7a70Dii DRC-2012-001697 DENISON MINES July 13, 2012 VIA PDF AND FEDERAL EXPRESS Mr Rusty Lundberg Director of the Utah Division of Radiation Control State of Utah Department of Environmental Quality 168 North 1950 West PO Box 144850 Salt Lake City, UT 84114-4850 Denison Mines (USA) Corp 1050 17th street, Suite 950 Denver, CO 80265 USA Tel 303 628-7798 Fax 303 389-4125 www denisonmines com Dear Mr Lundberg Re Utah Ground Water Discharge Permit No UGW3700004 Response to May 30, 2012 NOED and RFI Southwest Hydrogeology Investigation Report This letter responds to the above-mentioned Notice of Enforcement Discretion ("NOED") and Request for Information ("RFI") from the Utah Division of Radiation Control ("DRC") dated May 30, 2012 regarding the Southwest Hydrogeology Investigation and Report prepared in response to Part I H 6 of Denison Mines (USA) Corp's (Denison's) Utah Ground Water Discharge Permit No UGW370004 (the "Permit") Pursuant to Part I H 6 of the Permit, Denison submitted on January 12, 2012, the report entitled "Hydrogeology of the Perched Groundwater Zone in the Area Southwest of the Tailings Cells, White Mesa Uranium Mill Site" (the "Southwest Hydrogeology Report") DRC and Denison held telephone conference calls on May 23, 2012 and July 2, 2012 to review DRC's comments on the Southwest Hydrogeology Report Dunng the July 2, 2012 conference call, DRC clanfied that Denison could choose to respond to some of the issues raised in the NOED/RFI either by performing the additional investigations requested therein or, alternatively, by agreeing to prepare a revision to the Southwest Hydrogeology Report reflecting an additional theory as to the sources contnbuting to Cottonwood Seep Per agreements made with Mr Philip Goble dunng the July 2, 2012 conference call, Denison has agreed to respond to several of the issues by prepanng a revision to the report, as discussed below DRC's NOED/RFI letter of May 30, 2012 provided comments on the Southwest Hydrogeology Report For ease of review, each item in the NOED/RFI is provided verbatim in italics, below, followed by Denison's response Notice of Enforcement Discretion DRC Comment Part IH 6(8)2 of the Permit requires DUSA to "a) Install multiple borings and/or monitonng wells to completely enclose and define both Letter to Mr Rusty Lundberg July 13, 2012 Page 2 2) Piezometers or wells that intercept the shallow aquifer and encounter a saturation thickness of 5-feet or more Said wells and piezometers shall have a minimum inside diameter of 3 inches The Permittee shall complete hydraulic testing of all such wells and piezometers in accordance with Part IF 6(c) ofthis Permit " Per DRC review of the Report, it was noted that three of the borings, which had a saturated interval of greater than 5 feet, were abandoned without completion of casings/screens or hydraulic testing Specifically, borings DR-02, DR-16, and DR-25 were abandoned in violation ofthe Permit Part IH 6(a)2 DRC IS providing enforcement discretion for these violations, based on 1 DUSA good faith efforts to provide the southwest hydrogeology study and report, including fieldwork to provide 22 borings used to measure initial water levels, 16 of which were completed as piezometers for ongoing water level measurements and 13 of which were used for falling head slug tests to determine hydraulic properties ofthe Burro Canyon Aquifer 2 The DUSA agreement to conduct additional borings and install additional piezometers in the vicinity of and west of abandoned bonng DR-02, in order to characterize hydraulic properties and ground water flow directions in this area as discussed below Denison Response At the outset, and as discussed with DRC staff, it should be noted that Denison disagrees that the abandonment of three bonngs, which had a saturated thickness of 5-feet or more, constitutes a violation of the Permit Part I H 6(a)2 The Permit does not specify how many bonngs are required or where the bonngs were to be located The Permit merely requires that the charactenzation/definition of the subsurface shall be based on either dry wells, to delineate dry areas, or wet wells to delineate areas that are not dry, in an effort to define the dry zones It further states that in order to qualify as a wet well, the well must have a saturated thickness of at least 5 feet The Permit does not state that all bonngs dniled need to be retained It merely states that enough dry and wet bonngs must be dniled in order to define the dry area Denison and its experts determined that the three bonngs in question were not required in order to define the dry area, so they were abandoned Nonetheless, Denison has agreed to resolve all the issues raised in the NOED as committed in our phone conference of July 2, 2012 and as discussed below Request for Information DRC Comment 1 The Report does not provide field measured evidence to support a hydraulic divide in the area of piezometer DR-05 and abandoned borehole DR-02, as required by the Permit IH 6c Flow path lines as depicted on Figure 1f of the Report west of piezometer DR-05, which discount westerly flow toward Cottonwood Seep, are not supported with measured groundwater elevations and plotted contours that extend into this area The Report data shows relatively significant saturated thickness, > 10 ft, measured at piezometer DR-05 and boring DR-02 (prior to abandonment), but does not provide field data to determine how far west the zone of saturation extends or to provide hydraulic evaluation of that zone Additional borings and study are needed to better characterize flow and hydrogeology of the perched aquifer in the area west of abandoned bonng DR -02 (southwest of Westwater Seep) and to substantiate the statement in the Report that this area is "inadequate as a potential supply to Cottonwood Seep (p 19)" (based on water balance results for DR-10 and DR-05 only) Per Figure E 2 of the Report, the Burro Canyon Formation outcrops continue approximately 0 8 mile west of Westwater Seep (approximately 0 5 miles west of abandoned boring DR-02) Additionally, Figure E 2 of the report shows a significant area of slumps and landslides which extend even farther to the west DENISO MINES Mi Letter to Mr Rusty Lundberg July 13, 2012 Page 3 Denison Response As DRC and Denison have agreed to in the July 2, 2012 phone conference, Denison will prepare a revision of the Southwest Hydrogeology Report, to be submitted on or before August 3, 2012, which will include DRC's additional hypothesis that the perched zone could theoretically contnbute, in part, to flow to Cottonwood Seep Appropnate figures in the Southwest Hydrogeology Report will be modified to depict or to state that the perched zone may have some undefined connectivity to Cottonwood Seep DRC Comment 2 The Report, Table 3, lists slug test results (K and Ss) for the investigation completed piezometers DRC notes that the slug test results for piezometer DR-08 differ by an order of magnitude between the automatically logged data and the hand collected data DRC additionally notes that Table 3 lists, "Not Interpretable" as the K value at DR-08 by the Bouwer-Rice Method using the Hand Collected data Slug tests at piezometer DR-08 need to be repeated in order to validate the reported hydraulic conductivity values, and to substantiate the inclusion of these results in the hydraulic conductivity averages Denison Response Denison agrees to repeat slug tests at piezometer DR-08 as requested DRC Comment 3 The Report does not provide evidence to support the claims of a hydraulic connection between Westwater Creek and Cottonwood Seep as required by the Permit Part IH 6c The Report Figure 16, delineates an area which HGC interprets as the likely source of Cottonwood Seep based on elevation, however no additional information is provided to support the hydraulic connection Such evidence is required to include a Evidence of a continuous zone of higher permeability connecting the likely source area of Westwater Creek with Cottonwood Seep (e g boring logs showing the coarser grained or sandstone layer), b Delineation of stream alluvium deposits within the Cottonwood Creek drainage and especially within the proposed likely stream segment of Cottonwood Seep (to understand the actual zone of influence), c Average flow in the Westwater Drainage, d Evidence that Westwater Creek is a gaming stream in the segment proposed as a recharge source to Cottonwood Seep, d [sic] A detailed evaluation/explanation of the hydraulic mechanism promoting flow into the hypothesized higher permeability layer, instead of stream bed flow Denison Response DRC and Denison agreed dunng the phone conference of July 2, 2012, that Denison would revise the Southwest Hydrogeology Report to remove the discussion regardmg the hydraulic connection between Westwater Creek and Cottonwood seep, in lieu of the alternative of performing the substantial additional investigation required by DRC to provide sufficient evidence to retain the statement As mentioned above, Denison will submit Revision 1 ofthe Southwest Hydrogeology Report, modified per the agreements discussed in the comment responses above, by August 3, 2012 Please contact me If you have any additional questions or require any further information DENISO MINES Letter to Mr Rusty Lundberg July 13, 2012 Page 4 Yours very truly, DUSA MINES (USA) CORP Jo Ann Tischler Director, Compliance and Permitting cc David C Frydenlund Dan Hillsten Harold R Roberts David E Turk KathenneA Weinel DENISO MINES ;F>ii