Characterizing Ground-Water Flow Paths in High -Altitude Fractured - Rock Settings Impacted by Mining Activities Mike Wireman, U.S. EPA Region 8 Dr. Mark Williams, University of Colorado Mine Design, Operations & Closure Conference -2004

Mary Murphy Gold Mine Applied Research Site Research Objectives: * To Develop Tools for Characterization of Site Hydrology and Geochemistry * To Better Understand Role of Ground Water Transport of Metals to Chalk Creek. Remedial Objectives: * To Determine Metals Loading Sources and Pathways * To Reduce Metal Loadings to Chalk Creek Partners: * USGS, USFS, University of Colorado & CDMG

Mary Murphy Gold Mine—Applied Research Site Mining History Placer Mined in 1860’s-1870: Vein Deposits Located : Period of Greatest Mining Activity Mary Murphy Mine: 1870—1951 * 75% Gold, Silver, Lead, Zinc, Copper * 5 Main Veins * 14 Main Levels * 2200 Vertical Feet * Golf Adit—Drain / Haul Adit * Connected to Iron Chest Mine Remedial Work: * 1991—3 Piles Consolidated 69,000 cu. yds., Golf Tunnel Unplugged, Lined Settling Pond * 1992—Golf Adit Water Rerouted * 1998—1400 Level Opened / Stabilized * 1999—700 Level Partially Opened * 2003—Lady Murphy Adit Opened

Mary Murphy Mine Site Environmental Characterization History > Flow Measurements > Steam Tracing 14 Times –1990—2003 > GW Tracing > Metal Loading > Geochemical 5 Times- 1990—1994 Modeling > Sediment Sampling > Hydrometrics / Sept. ’93 & June ’99 Isotopic Research > Water Chemistry > Surficial 17 Times- 1990—2003 Geophysical Work > Toxicity Testing / Fish Data 11 Times- 1991—2003

Focus Of This Talk > Metals Loading > Stream & Ground-Water Tracing > Hydrometrics / Isotopic Results

Chalk Creek Mining District-Collegiate Range, CO

Geology and Mine Features Mary Murphy Mine & Vicinity

Elements of Conceptual Model Strong GW / SW Interaction > Gaining Streams > Strong Upward Gradient in Valley Bottom Fracture Dominated Flow Paths Multiple GW Flow Systems Many Seeps / Springs Significant Seasonal Variation in Flow and Water Quality ( GW & SW) Several Water Types Chemistry of GW & SW is Strongly Impacted by Geology and Mineralogy of Ore Body, and Mine Features.

Mary Murphy Gold Mine—Chafee County, CO DISSOLVED ZINC CONCENTRATIONS Location Date Conc. (ug/l) Chalk Creek CC-9 9/90 < 100 CC-9 7/ CC-9 7/02 24 CC-9 5/03 Upstream of Pomeroy 35.2 CC-7D 9/ CC-7D 7/02 44 CC-7D 5/03 Upstream of Golf 53.2 CC-7 9/90 18,000 CC-7 7/00 27,710 CC-7 7/02 24,300 CC-7 Golf Adit 3,620 CC-6 9/ CC-6 2/ CC-6 5/03 Upstream of Iron Chest 534 CC-0 9/90 < 100 CC-0 7/02 At Arkansas 08

Mary Murphy Gold Mine—Chafee County, CO DISSOLVED ZINC CONCENTRATIONS Location Date Conc. (ug/l) GW Wells MM-15 9/93 45 MM-15 Bedrock 7/02 08 MM-11 9/ MM-11 7/ MM-11 7/ MM-11 Allurial 5/ MM-3 9/93 17,131 MM-3 7/00 15,830 MM-3 2/02 21,500 MM-3 Bedrock 5/03 5,570 MM-6 9/ MM-6 7/02 13,700 MM-6 Allurial 122,000

Scope of Ground-Water Tracing Mary Murphy Mine—Applied Research Site

Results of Ground Water Tracing Mary Murphy Mine

Inverse Geochemical Modeling

Variation of Discharge Components Versus Time in 1400 Level. Mary Murphy Gold Mine

Delta O-18 in Selected Tributary Inflows, 1400 Level Mary Murphy Gold Mine

Pre-event Water and Event Water in Total Discharge From 1400 Portal Mary Murphy Gold Mine

HELIUM DATA Mary Murphy Mine site  ESTIMATED AGES OF GROUND WATER Using tritium data from different date t = 12.43/ln2. ln ( 1 + [3Het] / [3Ht] ) Clark & Fritz p188  BEDROCK WELLS MM YRSMM YRS MM YRSMM YRS MM 15 - ABOUT 8 YEARS OLDMM 15 - ABOUT 8 YEARS OLD  ALLUVIAL WELLS MM YRSMM YRS  Source – A. Manning -USGS