2020-02-03_REVISION - M1977378 - Laserfiche WebLink

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Sunnyside Gold Corporation Mayflower Impoundment 4 Monitor wells and Piezometers Permit No. M-1977-378 Technical Revision Narrative Introduction Sunnyside Gold Corporation (SGC)requests a Technical Revision (TR)to its Permit No. M-1977-378, to incorporate monitor wells and piezometers as described in further detail below and in the attachments. The requested TR would cover 17 monitor wells and eight piezometers. These installations are considered permanent. Monitor Wells SGC voluntarily installed nine monitor wells in 2015 as part of an initial site investigation at the Mayflower Impoundments requested by EPA. These wells are numbered MTMW 1 through MTMW 8. Each well was drilled to bedrock. These monitor wells are screened in the alluvium underlying the tails. Where groundwater was encountered in more than one zone,the wells were twinned, with one well drilled to and screened in the shallow water and the other drilled and completed in the deeper zone. This was the case with wells MTMW-6A and 6B. Five additional wells were installed in 2017 pursuant to an Administrative Settlement Agreement and Order on Consent for Remedial Investigation with EPA. The purpose of the wells is to monitor both groundwater chemistry and elevation. The wells are sampled twice annually,and each well is equipped with a pressure transducer to continuously monitor groundwater elevation. Piezometers The first seven piezometers were installed at some time during operation of the impoundment. The actual date is unknown. The eighth piezometer was installed in 2017, as part of the same drilling program as the five monitor wells mentioned above. The piezometers are not sampled for groundwater quality, but each of them is equipped with a pressure transducer. Attachments The attachments include the completed TR form,a spreadsheet with installation information for each well and piezometer and a map showing the location of each installation.