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