2025-07-28_REVISION - P2023018 - Laserfiche WebLink

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Salt Wash Member 155 1 1 3e-5 1 Summerville I No data (1) Lohman, 1965 (2) EPA, 2017 1.2.Baseline Groundwater Characterization Quarterly samples will be procured for 5 consecutive quarters in order to build an adequate baseline groundwater characterization. Samples will be taken from the three proposed monitoring wells, the existing Burro Mine Vent and Ellison Decline, as well as surface grab samples from upstream and downstream of the river. Site ID Sample Latitude Longitude Surface Top of Total Scree Compl Type Elevati Casing Depth ned etion on Intery Date al Up- Well 38.06044 -108.88403 6180 6183 880 5305- TBD Gradient* 5325 Mid- Well 38.04657 -108.86822 5858 5861 870 4990- TBD Gradient* 5010 Down- Well 38.03729 -108.84389 5765 5768 1000 4765- TBD Gradient* 5785 Burro Mine Mine 38.04653 -108.88836 5578 5581 n/a n/a n/a Vent Ellison Mine 38.03891 -108.88564 5670 n/a n/a n/a n/a Decline River Surface 38.03092 -108.88506 5450 n/a n/a n/a n/a Upstream River Surface 38.04404 -108.90580 5430 n/a n/a n/a n/a Downstream *Values for these monitor wells represent planned construction parameters and may vary depending on in-field conditions and other factors encountered during installation. Five consecutive quarters of water samples were taken from the Burro Vent and Ellison Decline locations from July 2022 to September 2023 and analyzed for RCRA 8, U&V, Salinity, Alkalinity, Ca, Mg,Na, and K at the request of DRMS. Subsequently, samples were taken from the Dolores upstream and downstream locations as well as the Burro Vent and Ellison Decline on 3/11/25 and were tested for all parameters requested in the DRMS 2023 guidance document. Slick Rock Project Groundwater Sampling and Analysis Plan-2025 Slick Rock NOI Modification July 2025 Appendix C Page 8 of 35