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.

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.

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.

ISOTOPE TABLE Isotope Symbol Molecule Type Half-life D H20 stable --- Deuterium D H20 stable --- Oxygen- 18 18O Stable Tritium 3H Radiogenic 12.7 years Sulfur- 35 35S SO42- 87 days Nitrogen- 15 15N NO3-

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 (‰):

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

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.

Chalk Creek Mine-Groundwater Source Controls Project Tasks & Milestones Task Description Cooperators Fund Source Time Frame Run expanded scope Isotope tracer study of identified inflows and GW sources INSTAAR/CDMG Supplement to grant* Through October 2001 Characterize inflow sources in upper levels of mine workings; sources of metals, metals loading analysis; refine hydrological model CDMG/INSTAAR 2000-2002 Prepare a plan and “EECA” for a full-scale source controls remediation approach addressing up to 85% of metals pollution from the Mary Murphy Mine CDMG/MES/CSM Fall 2001, 2002 Transfer technology on the project methodology through tours, presentations, peer –review papers, and progress reports CDMG/INSTAAR/EPA HQ 104b3 Ongoing, finalize by 2002

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

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

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

35S: UNITS AND VALUES Snowfall  60 mBq/L 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

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

Year 2000: Comparison of sulfur and water isotopes at two internal streams within the Mary Murphy Mine The MVN3 stream has high zinc and the GTFI site has little zinc. Isotope GTFI MVN-3 35S (mBq/L) 10 120 35S (mBq/ mgSO4) 0.3% <0.1% Atmospheric Sulfate 2.4% 18O (‰) -16.2 -18.1 New Water (%) 3% 80% 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-.

HYPOTHESIZED ISOTOPES, MMM

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.

ISOTOPE COSTS Isotope Waterloo INSTAAR USGS D $39 $20 --- 18O $33 3H $135 $100 35S $200 15N18O3 $150

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 -precipitation [5] Discharge -Hydrometric analysis -interior streams [6] Graduate Student -does the work

END OF PIPE STRATEGY

HYDROGRAPH SEPARATION

HYDROGRAPH AND ISOTOPES

ISOTOPES OF INTERIOR STREAMS

ZINC and HYDROGRAPH

SNOWMELT

BASEFLOW

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

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