Post on 19-Jan-2016
description
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
Mary Murphy Gold MineMary Murphy Gold MineApplied Research SiteApplied 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 SiteMining 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 > 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 FeaturesMary 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 CreekCC-9 9/90 < 100CC-9 7/00 118CC-9 7/02 24CC-9 5/03 Upstream of Pomeroy 35.2
CC-7D 9/90 110CC-7D 7/02 44CC-7D 5/03 Upstream of Golf 53.2
CC-7 9/90 18,000CC-7 7/00 27,710CC-7 7/02 24,300CC-7 Golf Adit 3,620
CC-6 9/90 420CC-6 2/02 417CC-6 5/03 Upstream of Iron Chest 534
CC-0 9/90 < 100CC-0 7/02 At Arkansas 08
Mary Murphy Gold Mine—Chafee County, CO DISSOLVED ZINC CONCENTRATIONS
Location Date Conc. (ug/l)GW WellsMM-15 9/93 45MM-15 Bedrock 7/02 08
MM-11 9/93 188MM-11 7/00 210MM-11 7/02 179MM-11 Allurial 5/03 560
MM-3 9/93 17,131MM-3 7/00 15,830MM-3 2/02 21,500MM-3 Bedrock 5/03 5,570
MM-6 9/93 2605MM-6 7/02 13,700MM-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 LevelMary Murphy Gold Mine
Pre-event Water and Event Water in Total Discharge From 1400 PortalMary Murphy Gold Mine
Tritium vs Delta O-18 Mary Murphy Mine Site (2002-2003)
-22.00
-20.00
-18.00
-16.00
-14.00
-12.00
-10.00
8 10 12 14 16 18 20
Tritium (TU)
Del
ta O
-18Surface Water
Alluvial Wells
Bedrock Wells
Snow
Mine Samples
HELIUM DATAMary 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 3 - 2-4 YRSMM 3 - 2-4 YRS
• MM 18 - 2-3 YRSMM 18 - 2-3 YRS
• MM 15 - ABOUT 8 YEARS OLDMM 15 - ABOUT 8 YEARS OLD
ALLUVIAL WELLS• MM11 - 3-4 YRSMM11 - 3-4 YRS
Source – A. Manning -USGSSource – A. Manning -USGS