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.

TARGETED SOURCE CONTROL

What is needed are the new tools to identify contamination sourceswithin 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

HYDROLOGYOf 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

Deuterium D H20 stable ---

Oxygen- 18 18O H20 Stable ---

Tritium 3H H20 Radiogenic 12.7 years

Sulfur- 35 35S SO42- Radiogenic 87 days

Nitrogen- 15 15N NO3- stable ---

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

CONTROLSDEMONSTRATION 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 Supplement to grant*

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 Supplement to grant*

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

18ArN=22 O2 SO2

SO4-2

Cosmic Rays

35SO42- 35SO4

2-

16 SN=16

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

UNITS: Generally reported asmillebecquerels 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 SO4

2- 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-335S (mBq/L) 10 120

35S (mBq/ mgSO4) 0.3% <0.1%

Atmospheric Sulfate 2.4% <0.1%

18O (‰) -16.2 -18.1

New Water (%) 3% 80%

The MVN stream was characterized by high amounts of 35S, a very low 35S to SO4

2- ratio, and relatively depleted 18O. These results suggest that the MVN stream is characterized by new water and that SO4

2- is from geochemical weathering. In contrast at the GTFI site, there is little new water and a low but much greater percentage of atmospheric SO4

2-.

HYPOTHESIZED ISOTOPES, MMM

18O

3H

35S 35S

3H 18O

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 ofunderground 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 $20 ---

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

-interior streams

-Chalk Creek

-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

ISOTOPE TRACERS AND GROUNDWATER FLOW FROM

ABANDONED MINES IN A FRACTURED ROCK SETTING

Mark Williams

Jen Hazen

Bob Michel

INSTAAR, Stratus Engineering, USGS