[PDF] - May 28, 2014 File: L020 Marty Sanderson Manager Diamond Resource PDF Document

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May 28, 2014 File: L020 Marty Sanderson Manager Diamond Resource Management North Slave Region, GNWT 16 Yellowknife Airport Yellowknife, NT X1A 3T2 Dear: Mr. Sanderson Re: Snap Lake Mine De Beers Canada Inc. Chloride Exceedance Water Licence #MV2011L2-0004 De Beers Canada Inc. (De Beers) is in receipt of your May 10, 2014 letter regarding the exceedance of the Average Monthly Limit for Chloride at Snap Lake Mine. On May 12, De Beers notified you of a non-compliance of the AML on April 23, April 29, and May 5 (now a confirmed result). Please find herein, a summary of actions undertaken since September 2013, and an action plan intended to prevent non-compliance in the future. Since the previous chloride AML event in September of 2013, Snap Lake Mine has operated within the parameters of its water license, except as previously noted, the reportable chloride AML was out of compliance on three sampling dates. The results of the AMLs calculated to date as they will appear in the April SNP are located in Table 1. The three non- compliant values are highlighted. Table 1: Chloride Concentration in Effluent 02-17B Date Grab (mg/L) Average Monthly 24-Mar-14 262 294 30-Mar-14 369 306 5-Apr-14 310 306 11-Apr-14 316 305 17-Apr-14 314 306 23-Apr-14 309 313 29-Apr-14 307 321 05-May-14 307 311 11-May-14 282 306 17-May-14 296 303

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Note that all grab sample values are well below the limit, and that the three non-compliant monthly average values are due to a single high grab sample result on March 30, of 369 mg/L. De Beers attributes this to the unforeseen intersection of an area of connate water high in total dissolved solids (including chloride), during regular mining operations. Work Completed Since September 2013 Water License Amendment Application Subsequent to the November 26, 2013 letter to the Mackenzie Valley Land and Water Board (Attachment 1) De Beers submitted a Water License Amendment Application on December 20, 2014 to increase the effluent AML for TDS and its constituent ions (including Chloride). De Beers’ application presents evidence that higher limits for chloride and TDS as a whole are appropriate and will ensure protection of the aquatic environment. This process is currently underway. Source Control and Grouting Since mid-2013, De Beers has undertaken monitoring and modeling of geological structures and groundwater flow to better understand the sources, characteristics and interconnectivity

made available to the MVLWB in April. The model has been used to predict future TDS loadings, and on-going monitoring has been used to identify areas of high TDS groundwater in mine workings. From work done to date, it is becoming evident that grouting is not a practical method for completely reducing overall inflows. De Beers continues to investigate the feasibility of controlled grouting in some areas of high TDS inflows as identified through monitoring. At present, dilution is the main method for managing chloride on site. High-TDS water can be and currently is temporarily stored in designated underground sumps and mine headings. Bi-hourly monitoring of conductivity in effluent allows for a controlled dilution of high-TDS water with “clear” water, before being discharged to the lake. The temporary storage of water in mine headings, renders these headings inoperable. This method is currently effective, as chloride AMLs have returned to compliant values. Ongoing work to prevent a recurrence De Beers is currently undergoing an Environmental Assessment and water license process to increase the AML for chloride at end of pipe to 378 mg/L and 604 mg/L Maximum Daily limit, and to apply a TDS AML at end-of-pipe. The proposal is based on on-going comprehensive site-specific toxicity studies, which conclude that higher AMLs will not result

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in harmful effects to the aquatic environment. As such, the non-compliance event in April would not have caused harmful effects to the environment. De Beers has indicated to the MVLWB during Technical Sessions and in information requests submitted on April 30 in support of the Water License Amendment, that it is currently conducting engineering studies and pilot testing of options to manage and process mine water for removal of TDS. Results of pilot studies are expected to be known before the end of 2014. De Beers continues to monitor and manage chloride in mine water to ensure compliance until such time as a decision on the amendment application is complete, which will guide De Beers on further evaluation of mitigation options. Environmental Daily reports which include in house chloride values and 6 day legal samples are forwarded to yourself on a daily basis. Additionally De Beers understands that the Inspector will be collecting a duplicate chloride sample over the next 6 day sampling cycles to determine compliance. Should you have any questions or concerns, please feel free to contact me by phone at (867) 766-8506 or by email at Maxwell.Morapeli@debeersgroup.com . Sincerely, Maxwell Morapeli Mine General Manager Snap Lake Mine DE BEERS CANADA INC. cc G.E. Koropchuk, E. Bonhomme, T. Bradbury, A. Hood, DBCI

GNWT

MVLWB

EC

SLEMA

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Nove Willa Mack PO B Yello X1A 2 Dear Re: S Conc Stati On O Land the s in Se and chlor respo 1.0 B The E

to inf have by ele ember 26, 20 rd Hagen, C kenzie Valley Box 2130 wknife, Nort 2P6 : Mr. Hagen Snap Lake M cerns regar

October 30, and Water tipulated lev

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Background Environment DS and its c the operatio fluences fro increased a evated TDS

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d y Average at #MV2011L2 a Inc. (De B eedance of t eillance Netw monitor the e ved Solids date on the (EAR; De Be nts, and som ater quality discharge ( perations libe

t Surveillan 2-0004 Beers) repor the monthly work Progra effluent resu (TDS) (in la e status of eers 2002) p me metals w in Snap Lak (De Beers 2 erating deep

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Attachment 1

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mperature o the Board to nd establish control and ber 31, 2013 t of TDS in nce requires g or publishe e, with chlori an mentione end between newater from ake). s over the was an an ers has incre uting effects.

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Figur Figur

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re 1a: Comp re 1b: 02-17

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parison bet 7B Chloride

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in ele than Table meas Table

ard Hagen, ember 26, 2 e 4

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identified tw t and treated uly 2013 whe er the power levels from the sampling s stabilized a de Values at

wo possible d from the fo en two powe r outage, de m the stored g results prio after Septem t 02-17B be

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mber 25, 201 fore and aft

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require the

to determine d that the gr educed or ce g may be a m asing water essary.

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y ecological e amount of e appropriat agement me r engineerin to the Board ecember 16

esigned to re ntation and f t system will be economic as possible d storing lar er review. De treatment a TDS Respo aborate on m ment Applic ater License for Chloride eers anticipa

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