aracterizing GroundWater Flow Paths in High Altitude actured

aracterizing Ground-Water Flow Paths in High -Altitude actured - Rock Settings Impacted by Mining Activities ke Wireman, U. S. EPA Region 8 Mark Williams, University of Colorado

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 • 1883 -1893: 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 14 Times – 1990— 2003 > Steam Tracing > GW Tracing > Metal Loading 5 Times- 1990— 1994 > Geochemical Modeling > Sediment Sampling Sept. ’ 93 & June ’ 99 > Hydrometrics / Isotopic Research > Water Chemistry 17 Times- 1990— 2003 > Surficial 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 Chalk Creek CC-9 Date Conc. (ug/l) 9/90 7/02 5/03 CC-7 D 9/90 7/02 5/03 CC-7 9/90 7/02 18, 000 27, 710 24, 300 3, 620 CC-6 9/90 2/02 5/03 420 417 534 CC-0 9/90 7/02 Upstream of Pomeroy Upstream of Golf Adit Upstream of Iron Chest At Arkansas < 100 118 24 35. 2 110 44 53. 2 < 100 08

Mary Murphy Gold Mine—Chafee County, CO DISSOLVED ZINC CONCENTRATIONS Location Date GW Wells MM-15 Bedrock 9/93 7/02 45 08 Allurial 9/93 7/00 7/02 5/03 188 210 179 560 Bedrock 9/93 7/00 2/02 5/03 17, 131 15, 830 21, 500 5, 570 9/93 7/02 2605 13, 700 122, 000 MM-11 MM-3 MM-6 Allurial Conc. (ug/l)

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

Results of Ground Water Tracing

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 Ø ESTIMATED AGES OF GROUND WATER • Using tritium data from different date • t = 12. 43/ln 2. ln ( 1 + [3 Het] / [3 Ht] ) Clark & Fritz p 188 § BEDROCK WELLS • MM 3 - 2 -4 YRS • MM 18 - 2 -3 YRS • MM 15 - ABOUT 8 YEARS OLD § ALLUVIAL WELLS • MM 11 - 3 -4 YRS Ø Source – A. Manning -USGS