TARGETED SOURCE CONTROL

1. TARGETED SOURCE CONTROL What is needed are the new tools to identify contamination sources within a mine so that the source control work can be targeted. We believe that that a combination of isotopic, hydrometric, and chemical characterization of water in and near mine-impacted regions can identify contaminated and clean water WITHIN hardrock mines and associated structures such as tailing piles. Targeted source control techniques have the potential for tremendous long-term cost savings relative to the prevalent end-of-pipe treatment strategies.

2. TRACERS IN HYDROLOGY • HYDROLOGY Of all the methods used to model hydrological processes in small watersheds, tracers (isotopic and chemical) have provided the best new insights into the age, origin, and pathway of water movement. The are among the few truly integrated measures of watershed function. Nevertheless, these techniques are not often used because the are seen as too complex, too costly, or too difficult to use. • MINE REMEDIATION Tracers are under-utilized to even a much larger extent than in hydrology.

3. ISOTOPES IN HYDROLOGY • What are environmental isotopes? Environmental isotopes of an element are part of the natural environment. They are ideal for use as fingerprinting tracers since they are already present in the system they are not added to the environment. • Why would you use environmental isotopes? The identification of fluid sources and pathways is often aided by the use of environmental isotopes. For example, waters from different areas may contain different isotopic fingerprints allowing the identification of the source.

4. ISOTOPE TABLE

5. ISOTOPIC RATIOS , DELTAS, and PERMILS Isotopic concentration are expressed as the difference the measured ratios of the sample and reference over the measured ratio of the reference. This is expressed using the delta (d) notation: Since the differences in mass are generally small, delta values are often expressed as parts per thousand or permil (‰):

6. CHALK CREEK MINE:GROUNDWATER SOURCE CONTROLSDEMONSTRATION PROJECT EPA VIII 104(b)3 Program SUPPLEMENTAL FUNDING REQUEST Assistance Agreement MM998404-02

7. Objectives [1] Use new procedures and techniques to refine the problem of identifying and isolating clean water inflows within the mine before they become contaminated by the orebody. [2]Demonstrate that we can reduce the export of zinc by up to 85% using a source controls approach. [3] Identify low-cost alternatives to remediation by preparing a detailed engineering evaluation an cost analysis (EECA) for a source controls program. The EECA will provide the foundation to test additional source control approaches at the Mary Murphy Mine proposed through the Hazardous Waste Center. [4] Transfer technology on the methods developed from this proposal through reports to the EPA, peer-review papers, and personal contacts with state and reclamation professionals.

8. Chalk Creek Mine-Groundwater Source Controls Project Tasks & Milestones

9. 35S: APPLICATIONS FOR MINE REMEDIATION • 1. ESTIMATE AGE OF WATER • Very effective for time scale less than one year • Few other environmental tracers can do this • 2. DISCRIMINATE “NEW” vs. “OLD” WATER SOURCES • Particularly good for identifying snowmelt in mine discharge • 3. DATE AGE OF SULFATE • Date age of atmospheric –deposited sulfate less than one year old • 4. DISCRIMINATE ATMOSHPERIC FROM GEOCHEMICAL SOURCES OF SULFATE

10. Sulfur-35 (35S) IN THE ENVIRONMENT • Radioactive isotope of sulfate • Half-life of about 87 days • Produced by spallation of argon atoms in the atmosphere by cosmic rays 18Ar N=22 16 S N=16 Cosmic Rays O2 SO2 35SO42- 35SO42- SO4-2

11. EVAPORATION USING WATER ISOTOPES Calculated tritium output curve for the Grafendorf spring, Massenberg Mountain, Austria. A similar approach can be used to age water bodies inside the Mary Murphy Mine

12. 35S: UNITS AND VALUES UNITS: Generally reported as millebecquerels per Liter (mBq/L) millebecquerels per mgSO4 (mBq/ mgSO4) CONCENTRATIONS: Snowfall  60 mBq/L Snowmelt  20 mBq/L because of decay of snowpack Rain(Summer)  100 mBq/L FACTORS- extent of atmospheric mixing of stratospheric air into troposphere; greatest in summer

13. 35S: Collection and Analysis Sample Collection • Need 1-20 Liters of sample • pass sample through ion exchange resin in the field • elute SO42- from resin with barium chloride • final volume  100 ml Sample Analysis • Liquid scintillation counting • Count twice, about 4 months apart as part of QA/QC

14. Year 2000: Comparison of sulfur and water isotopes at two internal streams within the Mary Murphy MineThe MVN3 stream has high zinc and the GTFI site has little zinc. The MVN stream was characterized by high amounts of 35S, a very low 35S to SO42- ratio, and relatively depleted 18O. These results suggest that the MVN stream is characterized by new water and that SO42- is from geochemical weathering. In contrast at the GTFI site, there is little new water and a low but much greater percentage of atmospheric SO42-.

15. HYPOTHESIZED ISOTOPES, MMM  18O  18O  3H  3H  35S  35S

16. SURFACE HYDROLOGY OF HARDROCK MINES Hydrogeological settings: • Steep slops on mountainsides • thin soil • highly fractured bedrock Water flow occurs primarily as fracture flow, reducing the effectiveness of the classic porous medium approach for understanding hydraulic connections within mine structures. The subsurface hydrology is further complicated by the presence of underground workings (adits, stopes, crosscuts, shafts, etc.), which perturb the local and intermediate groundwater systems. Relying only on monitoring wells and the assumptions associated with their use often leads to an inadequate description of groundwater flow and contaminant flux.

17. ISOTOPE COSTS

18. RECOMMENDATIONS FOR ADDITIONAL RESEARCH Sample Analysis Reason [1] all samples 18O and Zn [2] 35S -separate ppt from groundwater -700’ level -other interior streams -Chalk Creek -methods development [3] 3H -age groundwater streams -interior streams -Chalk Creek [4] 15N18O3 - -source of NO3 -interior streams -Chalk Creek -precipitation [5] Discharge -Hydrometric analysis -interior streams [6] Graduate Student -does the work

19. END OF PIPE STRATEGY

32. HYDROGRAPH SEPARATION

33. HYDROGRAPH AND ISOTOPES

34. ISOTOPES OF INTERIOR STREAMS

35. ZINC and HYDROGRAPH

37. SNOWMELT

38. BASEFLOW

39. END OF PIPE TREATMENT STRATEGY • Millions of dollars to install • Expensive to operate • Operate for long-term • Need low-cost alternatives

40. ISOTOPE TRACERS AND GROUNDWATER FLOW FROM ABANDONED MINES IN A FRACTURED ROCK SETTING Mark Williams Jen Hazen Bob Michel INSTAAR, Stratus Engineering, USGS