WATER QUALITY PREDICTIONS AT HARDROCK MINE SITES: METHODS, MODELS, AND CASE STUDY COMPARISON

1. WATER QUALITY PREDICTIONS AT HARDROCK MINE SITES: METHODS, MODELS, AND CASE STUDY COMPARISON James Kuipers, Kuipers & Assoc Ann Maest, Buka Environmental

2. Study Approach Synthesize existing reviews Develop “toolboxes” Evaluate methods and models Recommendations for improvement Outside peer review (Logsdon, Nordstrom, Lapakko) Case studies Synthesize existing reviews – lead to more depth and breadth Develop characterization and modeling “toolboxes” Evaluate methods and models - uncertainty Recommendations for improvement Outside peer review – in process (Logsdon, Nordstrom, Lapakko) Case studies Characterization Program: scientific and engineering studies that describe the physical, chemical, and biological characteristics of the site, its rocks and minerals, and its fluids allows one to describe the nature and extent of potential physical and chemical impacts to ground and surface water, and the engineering or institutional steps to control potential water-quality impacts. Synthesize existing reviews – lead to more depth and breadth Develop characterization and modeling “toolboxes” Evaluate methods and models - uncertainty Recommendations for improvement Outside peer review – in process (Logsdon, Nordstrom, Lapakko) Case studies Characterization Program: scientific and engineering studies that describe the physical, chemical, and biological characteristics of the site, its rocks and minerals, and its fluids allows one to describe the nature and extent of potential physical and chemical impacts to ground and surface water, and the engineering or institutional steps to control potential water-quality impacts.

3. 47% did no kinetic testing 16% didn’t evaluate AGP 53% did kinetic Doesn’t include characterization of mineralogy, whole rock analysis, paste pH, etc., but only 14/69 = 20% mentioned mineralogy in the EIS. Of those with “None,” only one was for an EA. It may be that the information is in other documents, but these are difficult to obtain and are not really considered publicly available.47% did no kinetic testing 16% didn’t evaluate AGP 53% did kinetic Doesn’t include characterization of mineralogy, whole rock analysis, paste pH, etc., but only 14/69 = 20% mentioned mineralogy in the EIS. Of those with “None,” only one was for an EA. It may be that the information is in other documents, but these are difficult to obtain and are not really considered publicly available.

6. Specific Models Used Water Quantity only (18 mines) Near-surface processes: HEC-1, HELP Sediment transport: SEDCAD, MUSLE, RUSLE, R1/R3SED Storm hydrographs: WASHMO Groundwater flow: MODFLOW, MINEDW Vadose zone: HYDRUS; drawdown

7. Specific Models Used (cont.) Water quantity and quality (21 mines) Water quantity + PHREEQE (3), WATEQ (1), MINTEQ (5) Pyrite oxidation (PYROX) – 3 mines Water balance/contam transport (LEACHM) – 1 mine Pit water flow and quality (limited): CE-QUAL-W2 (3), CE-QUAL-R1 (1) Mass balance/loading: unspecified (4 mines), FLOWPATH Proprietary codes for pit lake water quality or groundwater quality downgradient of waste rock pile (4 mines)

8. Sources of Uncertainty - Modeling Use of proprietary codes need testable, transparent models – difficult to evaluate, should be avoided. Need efforts to expand publicly available pit lake models (chemistry). Modeling inputs large variability in hydrologic parameters; seasonal variability in flow and chemistry; sensitivity analyses (ranges) rather than averages/medians Estimation of uncertainty Acknowledge and evaluate effect on model outputs; test multiple conceptual models “…there is considerable uncertainty associated with long-term predictions of potential impacts to groundwater quality from infiltration through waste rock...for these reasons, predictions should be viewed as indicators of long-term trends rather than absolute values.”; CAEDYM is a publicly available lake model, but it is more of an aquatic ecological model than a hydrogeochemical model. Only addresses Fe, Mn, Al – redox chemistry (including Al redox chemistry???). Can be linked with a 3D hydrodynamic model, but unclear if user would have to input all info on groundwater inputs, loads from wall rock, etc. Hydrologic parameters: hydraulic conductivity Uncertainty analysis: Monte Carlo analysis, stochastic methods, and evaluating a range of model parameters to develop a range of deterministic outcomes (e.g., a range of water quality in a given receptor). These methods account for the fact that, rather than being well described by a single value as required in the model, parameters are better described with a probability distribution (i.e., a mean, variance, skewness, etc.), especially hydraulic conductivity and other hydrologic parameters. Uncertainty may derive from incomplete characterization, an inability to discretize the model domain sufficiently, or incomplete knowledge of the geochemical and hydrologic conditions at the site. CAEDYM is a publicly available lake model, but it is more of an aquatic ecological model than a hydrogeochemical model. Only addresses Fe, Mn, Al – redox chemistry (including Al redox chemistry???). Can be linked with a 3D hydrodynamic model, but unclear if user would have to input all info on groundwater inputs, loads from wall rock, etc. Hydrologic parameters: hydraulic conductivity Uncertainty analysis: Monte Carlo analysis, stochastic methods, and evaluating a range of model parameters to develop a range of deterministic outcomes (e.g., a range of water quality in a given receptor). These methods account for the fact that, rather than being well described by a single value as required in the model, parameters are better described with a probability distribution (i.e., a mean, variance, skewness, etc.), especially hydraulic conductivity and other hydrologic parameters. Uncertainty may derive from incomplete characterization, an inability to discretize the model domain sufficiently, or incomplete knowledge of the geochemical and hydrologic conditions at the site.

10. Summary Characterization methods need major re-evaluation, especially static and short-term leach tests Increased use of mineralogy in characterization – make less expensive, easier to use/interpret Modeling uncertainty needs to be stated and defined Limits to reliability of modeling – use ranges rather than absolute values Increased efforts on long-term case studies

11. Comparison of Predicted and Actual Water Quality

12. EIS Review Mines 183 major, 137 NEPA, 71 NEPA reviewed Similar in location, commodities, extraction, processing, operational status 104 EISs reviewed for 71 mines 16 months to obtain all documents Compared EIS predictions to actual water quality for 25 case study mines 137 NEPA = on federal lands or certain NPDES or ACOE or 404 permits or land on Native American trust lands administered by BIA or state NEPAs (CA, MT, WA, WI) Largest repository of mining EISs in western hemisphere = Jim Kuiper’s office in Butte after I sent him my 10 boxes of EISs137 NEPA = on federal lands or certain NPDES or ACOE or 404 permits or land on Native American trust lands administered by BIA or state NEPAs (CA, MT, WA, WI) Largest repository of mining EISs in western hemisphere = Jim Kuiper’s office in Butte after I sent him my 10 boxes of EISs

13. EIS Years

14. EIS Approach to Impacts

15. Case Study Mines Selection based on ease of access to water quality data variability in geographic location, commodity type, extraction and processing methods variability in EIS elements related to water quality (climate, proximity to water, ADP, CLP) Best professional judgment Similar to all NEPA mines, but more from CA and MT fewer Cu mines more with moderate ADP and CLP more with shallower groundwater depths

16. Case Study Mines: General States AK: 1 - MT: 6 AZ: 2 - NV: 7 CA: 6 - WI: 1 ID: 2 Commodity Au/Ag: 20 - Pb/Zn: 1 Cu/Mo: 2 - PGM: 1 Mo: 1 Extraction type open pit: 19 underground: 4 both: 2 Processing type CN Heap: 12 Vat: 4 Flotation: 7 Dump Leach: 2

17. Case Study Mines Selected

18. Comparison Results Mines with mining-related surface water exceedences: 60% % estimating low impacts pre-mitigation: 27% % estimating low impacts with mitigation: 73% Mines with mining-related groundwater exceedences: 52% % estimating low impacts pre-mitigation: 15% % estimating low impacts with mitigation: 77% Mines with acid drainage on site: 36% % predicting low acid drainage potential: 89% Later compare overall findings with findings for mines with inherent geochemical and hydrologic characteristics.Later compare overall findings with findings for mines with inherent geochemical and hydrologic characteristics.

19. Inherent Factors ore type and association climate proximity to water resources pre-existing water quality constituents of concern acid generation and neutralization potentials contaminant leaching potential This is the type of information on inherent factors we could find in EISs. ore type and association (e.g., commodity, sulfide vs. oxide ore, vein vs. disseminated) • climate (e.g., amount and timing of precipitation, evaporation, temperature) • proximity to water resources (distance to surface water resources, depth to groundwater resources, presence of springs) • pre-existing water quality (baseline groundwater and surface water quality conditions) • constituents of concern • acid generation and neutralization potentials (and timing of their release), and • contaminant generation potential. This is the type of information on inherent factors we could find in EISs. ore type and association (e.g., commodity, sulfide vs. oxide ore, vein vs. disseminated) • climate (e.g., amount and timing of precipitation, evaporation, temperature) • proximity to water resources (distance to surface water resources, depth to groundwater resources, presence of springs) • pre-existing water quality (baseline groundwater and surface water quality conditions) • constituents of concern • acid generation and neutralization potentials (and timing of their release), and • contaminant generation potential.

20. Surface Water Results Arguably, for all case study mines, there were 12/15 that exceeded that predicted no exceedences (Thompson predicted no exceedence in one EIS). This brings % to 80%. All results are for mining-related impacts or exceedences. Suggests that mines with these factors are more likely to have surface water quality problems.Arguably, for all case study mines, there were 12/15 that exceeded that predicted no exceedences (Thompson predicted no exceedence in one EIS). This brings % to 80%. All results are for mining-related impacts or exceedences. Suggests that mines with these factors are more likely to have surface water quality problems.

21. Groundwater Results All results are for mining-related impacts or exceedences. Suggests that mines with these factors are more likely to have groundwater quality problems. All results are for mining-related impacts or exceedences. Suggests that mines with these factors are more likely to have groundwater quality problems.

22. Mines without Inherent Factors California desert mines American Girl, Castle Mountain, Mesquite No groundwater or surface water impacts or exceedences Delayed impacts? Climate change (but less precip predicted) Stillwater, Montana Close to water, low ADP, moderate/high CLP Unused surface water discharge permit Increases in nitrate (predicted from LAD by modeling) in Stillwater River, but no exceedences Mining-related exceedences in adit and groundwater under LAD, but related to previous owners? Inherently lucky – ultramafic mineralogy Check on high %S. Better mines had more accurate predictions – but only b/c ~all said there would be no WQ problems after mitigations were in place Note that “better” performance is generally related to inherent factors, not mitigations or operational controls.Check on high %S. Better mines had more accurate predictions – but only b/c ~all said there would be no WQ problems after mitigations were in place Note that “better” performance is generally related to inherent factors, not mitigations or operational controls.

23. Predicted vs. Actual Water Quality Cascading effect – if geochemi/hydrololic info is wrong, mitigations won’t be what they need to be. Not all exceeds were caused by mitigation failures; some mines had all three kinds of failures (geochem, hydrologic, mitigation). Cascading effect – if geochemi/hydrololic info is wrong, mitigations won’t be what they need to be. Not all exceeds were caused by mitigation failures; some mines had all three kinds of failures (geochem, hydrologic, mitigation).

24. Implications Mines close to water with mod/high ADP/CLP need special attention from regulators Water quality impact predictions before mitigation in place more reliable These can be in error too – geochemical and hydrologic characterization need improvement Why do mitigations fail so often and what can be done about it?

25. Characterization Methods Geology Mineralogy Whole rock analysis Paste pH Sulfur analysis Total inorganic carbon Static testing Short-term leach testing Laboratory kinetic tests Field testing of mined materials

26. Modeling Opportunities

27. Modeling Toolbox Category/subcategory of code Hydrogeologic, geochemical, unit-specific Available codes Special characteristics of codes Inputs required Modeled processes/outputs Step-by-step procedures for modeling water quality at mine facilities

28. EIS Information Reviewed Geology/mineralogy Climate Hydrology Field/lab tests Predictive models used Water quality impact potential Mitigation measures Predicted water quality impacts Discharge information Information was scored (0 – 7). Information derived from Section 3’s of EISs: Environmental Consequences. Didn’t get additional reports, but did look at appendices. Hydrology proximity to surface water Depth to groundwater Water quality impact potential acid drainage (ADP) contaminant leaching (CLP) surface water groundwater pit water Mitigation measures surface water groundwater pit water treatment other Predicted water quality impacts surface water groundwater pit water Discharge information zero discharge surface water groundwaterInformation was scored (0 – 7). Information derived from Section 3’s of EISs: Environmental Consequences. Didn’t get additional reports, but did look at appendices. Hydrology proximity to surface water Depth to groundwater Water quality impact potential acid drainage (ADP) contaminant leaching (CLP) surface water groundwater pit water Mitigation measures surface water groundwater pit water treatment other Predicted water quality impacts surface water groundwater pit water Discharge information zero discharge surface water groundwater

29. Surface Water Examples Flambeau, WI had inherent factors but no impact or exceedence to date Stillwater, MT had an impact (0.7 mg/l nitrate in Stillwater River) but no exceedence McLaughlin, CA predicted exceedences in surface water and was correct McLaughlin Mine: Acid Drainage and Contaminant Leaching Potential: Ninety-two% of the waste rock has been determined to be either neutralizing or itself neutral. Comparison of the (tailings) extract analysis concentrations with the health-based Soluble Threshold Limit Concentration (STLC) based on the WET test shows that the estimated concentration of copper exceeds the STLC which could cause the tailings to be considered hazardous. In addition to high copper values, the tailings extract also had lead, arsenic, silver, and cyanide concentrations in excess of water quality standards. Potential Water-Quality Impacts (before mitigations): Groundwater - Permanent degradation of groundwater quality is expected due to tailings seepage. Surface Water - There are three types of surface water quality impacts that may potentially occur (from the waste rock dumps): (1) increased sedimentation from runoff, (2) increased total dissolved solids from leachate, and (3) increased heavy metal concentrations from acidic leachate. Potential water quality decreases in Hunting Creek from waste rock leachate. Pit Water - Quality of water accumulated in the pit is expected to be of poor quality, with high concentrations of heavy metals and major ions including arsenic, cadmium, iron, lead, manganese, mercury, nickel, boron, sodium, chloride, and sulfate. Mitigations: Groundwater – monitoring. Underdrains for waste rock piles. Surface Water - Sediment basins to protect streams and numerous erosion/sedimentation controls. Potentially acid generating rock will be surrounded by alkaline material during waste rock disposal. Lime will be added to sediment ponds if acidic conditions are encountered during mining. Pit Water – None. Predicted Water-Quality Impacts (after mitigations): Groundwater - Proposed tailings facility would allow 40 gpm of seepage to local groundwater underlying the reservoir. This impact would be long term, resulting in permanent degradation of the local groundwater and potentially of the shallow groundwater flowing toward Hunting Creek. Existing groundwater data in the tailings area show poor quality water with long residence times, and very low permeabilities. Therefore, although the proposed action and alternatives would lead to permanent degradation of localized groundwater, local water supply would not be impacted, because the groundwater regime in Quarry Valley has not been found to be connected to a regional aquifer system, and the dam foundation would penetrate to less permeable material. Possible release of TDS from waste rock dump, but it will be collected in the underdrains, the diversion ditches, or in the sediment impoundment. Surface Water - Modeling indicated that arsenic, nickel, zinc, silver, iron, and copper concentrations would be lower than drinking water standards in Hunting Creek. Manganese was predicted to slightly exceed its standard. There would be no impact to surface water quality under normal operation of the mill facilities. Pit Water - The quality of water accumulated in the pit is expected to be of poor quality, with high concentrations of heavy metals and major ions including arsenic, cadmium, iron, lead, manganese, mercury, nickel, boron, sodium, chloride, and sulfate. Predominance of alkaline producing materials in the rocks would likely produce alkaline pH conditions in the mine pit water and would tend to reduce metals leached from the rocks. Pit water would not reach surface streams, and no impacts on the quality of Hunting, Davis, or Knoxville creeks are anticipated. Surface Water Impacts: Potential surface water quality impacts from tailings were not expected; however, potential impacts from waste rock were recognized and modeled. Modeled arsenic, nickel, zinc, silver, iron and copper concentrations were predicted to be lower and manganese higher than drinking water standards in Hunting Creek. The modeling results were correct for zinc, silver, manganese and copper, which did not exceed standards but were incorrect for arsenic, nickel and iron, which did exceed standards. McLaughlin Mine: Acid Drainage and Contaminant Leaching Potential: Ninety-two% of the waste rock has been determined to be either neutralizing or itself neutral. Comparison of the (tailings) extract analysis concentrations with the health-based Soluble Threshold Limit Concentration (STLC) based on the WET test shows that the estimated concentration of copper exceeds the STLC which could cause the tailings to be considered hazardous. In addition to high copper values, the tailings extract also had lead, arsenic, silver, and cyanide concentrations in excess of water quality standards. Potential Water-Quality Impacts (before mitigations): Groundwater - Permanent degradation of groundwater quality is expected due to tailings seepage. Surface Water - There are three types of surface water quality impacts that may potentially occur (from the waste rock dumps): (1) increased sedimentation from runoff, (2) increased total dissolved solids from leachate, and (3) increased heavy metal concentrations from acidic leachate. Potential water quality decreases in Hunting Creek from waste rock leachate. Pit Water - Quality of water accumulated in the pit is expected to be of poor quality, with high concentrations of heavy metals and major ions including arsenic, cadmium, iron, lead, manganese, mercury, nickel, boron, sodium, chloride, and sulfate. Mitigations: Groundwater – monitoring. Underdrains for waste rock piles. Surface Water - Sediment basins to protect streams and numerous erosion/sedimentation controls. Potentially acid generating rock will be surrounded by alkaline material during waste rock disposal. Lime will be added to sediment ponds if acidic conditions are encountered during mining. Pit Water – None. Predicted Water-Quality Impacts (after mitigations): Groundwater - Proposed tailings facility would allow 40 gpm of seepage to local groundwater underlying the reservoir. This impact would be long term, resulting in permanent degradation of the local groundwater and potentially of the shallow groundwater flowing toward Hunting Creek. Existing groundwater data in the tailings area show poor quality water with long residence times, and very low permeabilities. Therefore, although the proposed action and alternatives would lead to permanent degradation of localized groundwater, local water supply would not be impacted, because the groundwater regime in Quarry Valley has not been found to be connected to a regional aquifer system, and the dam foundation would penetrate to less permeable material. Possible release of TDS from waste rock dump, but it will be collected in the underdrains, the diversion ditches, or in the sediment impoundment. Surface Water - Modeling indicated that arsenic, nickel, zinc, silver, iron, and copper concentrations would be lower than drinking water standards in Hunting Creek. Manganese was predicted to slightly exceed its standard. There would be no impact to surface water quality under normal operation of the mill facilities. Pit Water - The quality of water accumulated in the pit is expected to be of poor quality, with high concentrations of heavy metals and major ions including arsenic, cadmium, iron, lead, manganese, mercury, nickel, boron, sodium, chloride, and sulfate. Predominance of alkaline producing materials in the rocks would likely produce alkaline pH conditions in the mine pit water and would tend to reduce metals leached from the rocks. Pit water would not reach surface streams, and no impacts on the quality of Hunting, Davis, or Knoxville creeks are anticipated. Surface Water Impacts: Potential surface water quality impacts from tailings were not expected; however, potential impacts from waste rock were recognized and modeled. Modeled arsenic, nickel, zinc, silver, iron and copper concentrations were predicted to be lower and manganese higher than drinking water standards in Hunting Creek. The modeling results were correct for zinc, silver, manganese and copper, which did not exceed standards but were incorrect for arsenic, nickel and iron, which did exceed standards.

30. Groundwater Examples Lone Tree, NV had inherent factors but no mining-related impact or exceedence baseline issue McLaughlin, CA had inherent factors and did have exceedences regulatory exclusion for groundwater (poor quality, low K), so no violations 92% of rocks not acid generating Tailings leachate flunked STLC – hazardous aquifer

31. McLaughlin Mine, CA: Waste Rock Monitoring Well Mining started in 1985. Don’t know why concentrations started to decrease.Mining started in 1985. Don’t know why concentrations started to decrease.

32. Case Study Mines: Water Quality Climate Dry/Semi-Arid: 12 Marine West Coast: 1 Humid subtropical: 3 Boreal: 8 Continental: 1 Perennial streams No info: 1 >1 mi: 6 <1 mi: 7 On site: 11 Groundwater depth No info: 1 >200’: 3 50-200’: 4 0-50’/springs: 17 Acid drainage potential No info: 2 Low: 12 Moderate: 8 High: 3 Contaminant leaching No info: 3 Low: 8 Moderate: 10 High: 4 ADP: based on static testing results, sulfur or pyrite contents or simply on statements in the EIS or EA that described the acid drainage potential as “low,” “moderate,” or “high” or that the material does or does not have the potential to produce acid. Identification of existing acid drainage was reported in some cases, but more importance was placed on the potential for acid drainage for the proposed project that was the subject of the EIS or EA. The recorded potential for acid drainage is for unit/material with the greatest potential to produce acid. CLP: Qualitative, or based on short- or long-term leach test results: Low - leachate does not exceed water quality standards (1) • Moderate - leachate exceeds water quality standards by 1-10 times (2) • High - leachate exceeds water quality standards by over 10 times (3) ADP: based on static testing results, sulfur or pyrite contents or simply on statements in the EIS or EA that described the acid drainage potential as “low,” “moderate,” or “high” or that the material does or does not have the potential to produce acid. Identification of existing acid drainage was reported in some cases, but more importance was placed on the potential for acid drainage for the proposed project that was the subject of the EIS or EA. The recorded potential for acid drainage is for unit/material with the greatest potential to produce acid. CLP: Qualitative, or based on short- or long-term leach test results: Low - leachate does not exceed water quality standards (1) • Moderate - leachate exceeds water quality standards by 1-10 times (2) • High - leachate exceeds water quality standards by over 10 times (3)

33. Failure Modes and Effects Analysis

34. Failure Modes and Effects Analysis Hydrological Characterization Failures: 7 of 22 mines exhibited inadequacies in hydrologic characterization At 2 mines dilution was overestimated At 2 mines the presence of surface water from springs or lateral flow of near surface groundwater was not detected At 3 mines the amount of water generated was underestimated

35. Failure Modes and Effects Analysis Geochemical Characterization Failures: 11 of 22 mines exhibited inadequacies in geochemical characterization Geochemical failures resulted from: Assumptions made about geochemical nature of ore deposits and surrounding areas Site analogs inappropriately applied to new proposal Inadequate sampling Failure to conduct and have results for long-term contaminant leaching and acid drainage testing procedures before mining begins. Failure to conduct the proper tests, or to improperly interpret test results, or to apply the proper models Geochemical failures resulted from: (1) - (e.g. mining will only be done in oxidized area) (2) - (e.g. historic underground mine workings do not produce water or did not indicate acid generation) (3) - (e.g. geochemical characterization did not indicate potential due to composite samples or samples not being representative of actual mining) Geochemical failures resulted from: (1) - (e.g. mining will only be done in oxidized area) (2) - (e.g. historic underground mine workings do not produce water or did not indicate acid generation) (3) - (e.g. geochemical characterization did not indicate potential due to composite samples or samples not being representative of actual mining)

36. Failure Modes and Effects Analysis Mitigation Failures: 18 of 22 mines exhibited failures in mitigation measures At 9 of the mines mitigation was not identified, inadequate or not installed At 3 of the mines waste rock mixing and segregation was not effective At 11 of the mines liner leaks, embankment failures or tailings spills resulted in impacts to water resources

37. Failure Modes Root Causes Hydrologic Characterization Failures most often caused by: Over-estimation of dilution effects Failure to recognize hydrological features Underestimation of water production quantities Prediction of storm events or deficiencies in stormwater design criteria is the most typical root cause of hydrologic characterization failures The case studies show the indirect cause and effect relationship between inadequacies in hydrologic characterization methods that have been employed at mine sites and have resulted in impacts to water resources ranging from on-site contamination and contamination of headwaters streams to more extensive off-site contamination of surface water with the potential need for long-term water treatment in some cases. Prediction of storm events or deficiencies in the design criteria (e.g. use of 100-yr storm events) is the most typical root cause of hydrologic characterization failures. Failure to recognize near surface water resulting in lateral flow and spread of contaminants and overestimation of dilution particularly in the presence of headwater streams are also both typical root causes of hydrologic characterization failures. The other root cause of hydrologic characterization failures identified was failure to identify greater quantities of water than expected. The overall degree of impact from this failure mode ranges from moderate to high with the potential for severe impacts. Hydrological characterization failures are most often caused by over-estimation of dilution effects, failure to recognize hydrological features and underestimation of water production quantities and can be addressed by requiring adequate hydrological investigations as well as making conservative assumptions about water quality and quantity.The case studies show the indirect cause and effect relationship between inadequacies in hydrologic characterization methods that have been employed at mine sites and have resulted in impacts to water resources ranging from on-site contamination and contamination of headwaters streams to more extensive off-site contamination of surface water with the potential need for long-term water treatment in some cases. Prediction of storm events or deficiencies in the design criteria (e.g. use of 100-yr storm events) is the most typical root cause of hydrologic characterization failures. Failure to recognize near surface water resulting in lateral flow and spread of contaminants and overestimation of dilution particularly in the presence of headwater streams are also both typical root causes of hydrologic characterization failures. The other root cause of hydrologic characterization failures identified was failure to identify greater quantities of water than expected. The overall degree of impact from this failure mode ranges from moderate to high with the potential for severe impacts. Hydrological characterization failures are most often caused by over-estimation of dilution effects, failure to recognize hydrological features and underestimation of water production quantities and can be addressed by requiring adequate hydrological investigations as well as making conservative assumptions about water quality and quantity.

38. Failure Modes Root Causes Geochemical Characterization Root causes of Geochemical Prediction Failures include: Sample representation Testing methods Modeling/Interpretation Geochemical Characterization Failures can be addressed by: Ensuring sample representation Adequate testing Interpretation The root causes of geochemical predictions failures include sample representation (samples tested are not representative of sources to be created), testing methods (static and kinetic), and modeling/interpretation. In the majority of cases cited in these case studies early naivety about the potential for acid drainage can be observed in the lack of testing conducted and reliance on anecdotal (e.g. no evidence of acid drainage from historic mine features) and often times inaccurate information. While it is less common today with many regulatory jurisdictions requiring that more advanced practices be used to ensure better geochemical characterization takes place, mines are still promoted as being non acid-generating or otherwise benign based on unsubstantiated or inadequate information.The root causes of geochemical predictions failures include sample representation (samples tested are not representative of sources to be created), testing methods (static and kinetic), and modeling/interpretation. In the majority of cases cited in these case studies early naivety about the potential for acid drainage can be observed in the lack of testing conducted and reliance on anecdotal (e.g. no evidence of acid drainage from historic mine features) and often times inaccurate information. While it is less common today with many regulatory jurisdictions requiring that more advanced practices be used to ensure better geochemical characterization takes place, mines are still promoted as being non acid-generating or otherwise benign based on unsubstantiated or inadequate information.

39. Failure Modes Root CausesMitigation Hydrologic and geochemical characterization failures are the most common root cause of mitigation not being identified, inadequate or not installed Most common assumption is that “oxide” will not result in acid generation Mitigations are often based on what is common rather than on site specific characterization The case studies show that in many cases due to geochemical characterization and/or hydrological characterization not identifying potential impacts from acid drainage and other contaminants to water resources, mitigation are either not identified or prove to be inadequate. The most common situation has been the assumption that “oxide” ore will not result in acid generation resulting in inadequate characterization of both sources (e.g. waste rock, tailings) and receptors (hydrology). Most of the case studies cited are examples of characterization practices that had not evolved during the earlier years of the NEPA process, but include some which continued to operate into the 1990s and even currently. In nearly all cases practices have been modified to allow for improved geochemical characterization although the scientific uncertainties are still not well respected in many regulatory decisions. Hydrologic characterizations have improved in most respects, however the application of 100-yr storm events (versus probable maximum precipitation events) continues to be problematic and results inevitably in discharges to water resources. Failure to identify mitigation or to specify inadequate mitigation is always typically caused by inadequate geochemical or hydrological characterizations, or failure to apply the available information. All too often mitigation is based on what is commonly used rather than on site characterization.The case studies show that in many cases due to geochemical characterization and/or hydrological characterization not identifying potential impacts from acid drainage and other contaminants to water resources, mitigation are either not identified or prove to be inadequate. The most common situation has been the assumption that “oxide” ore will not result in acid generation resulting in inadequate characterization of both sources (e.g. waste rock, tailings) and receptors (hydrology). Most of the case studies cited are examples of characterization practices that had not evolved during the earlier years of the NEPA process, but include some which continued to operate into the 1990s and even currently. In nearly all cases practices have been modified to allow for improved geochemical characterization although the scientific uncertainties are still not well respected in many regulatory decisions. Hydrologic characterizations have improved in most respects, however the application of 100-yr storm events (versus probable maximum precipitation events) continues to be problematic and results inevitably in discharges to water resources. Failure to identify mitigation or to specify inadequate mitigation is always typically caused by inadequate geochemical or hydrological characterizations, or failure to apply the available information. All too often mitigation is based on what is commonly used rather than on site characterization.

40. Failure Modes Root CausesMitigation Waste rock mixing and segregation not effective In most cases, no real data is available (e.g. tons of NAG versus tons of PAG and overall ABA accounting) Failures typically caused by: Inadequate neutral material Inability to effectively isolate acid generating material from nearby water resources At many mines waste rock containing acid generating materials is managed by mixing and segregation practices. In most cases no data is available to ascertain the effectiveness of those practices, particularly where there is a significant distance from the source to water resources. The cases cited all have nearby water resources that have been impacted. The data suggests that distance to water resources is potentially the most significant factor as to the effectiveness of waste rock mixing and segregation. Mitigation may depend more on climate and factors such as distance and geology affecting travel time and attenuation of contaminants. Where acid drainage generating materials are present, particularly in areas of headwater streams, waste rock mixing and segregation may not prevent impacts to water resources. Mixing and segregation mitigation failures occur at a moderate frequency and are typically caused by inadequate neutral material and inability to effectively isolate acid generating material from nearby water resources. This can be addressed by requiring adequate geochemical characterization and identification of water resources to ensure that segregation occurs away from potential water pathways.At many mines waste rock containing acid generating materials is managed by mixing and segregation practices. In most cases no data is available to ascertain the effectiveness of those practices, particularly where there is a significant distance from the source to water resources. The cases cited all have nearby water resources that have been impacted. The data suggests that distance to water resources is potentially the most significant factor as to the effectiveness of waste rock mixing and segregation. Mitigation may depend more on climate and factors such as distance and geology affecting travel time and attenuation of contaminants. Where acid drainage generating materials are present, particularly in areas of headwater streams, waste rock mixing and segregation may not prevent impacts to water resources. Mixing and segregation mitigation failures occur at a moderate frequency and are typically caused by inadequate neutral material and inability to effectively isolate acid generating material from nearby water resources. This can be addressed by requiring adequate geochemical characterization and identification of water resources to ensure that segregation occurs away from potential water pathways.

41. Failure Modes Root CausesMitigation Liner leak, embankment failure or tailings spill Mitigation frequently fails to perform and can lead to groundwater and surface water quality impacts Failures are typically caused by: Design mistakes Construction mistakes Operational mistakes The case studies show that mitigation may fail and lead to groundwater and surface water quality impacts. While in most cases impacts are limited to on-site groundwater and nearby surface water in some cases the impacts can result in more extensive surface water impacts and potentially to long-term water treatment. In all cases additional mitigation has resulted in effective capture and treatment of contaminants. Failure of mitigations to perform is typically caused by design, construction, and operational mistakes. Mitigation frequently fails to perform so it is important to consider the likelihood and consequences of those failures and to identify additional mitigations that can be employed in the event of such failures.The case studies show that mitigation may fail and lead to groundwater and surface water quality impacts. While in most cases impacts are limited to on-site groundwater and nearby surface water in some cases the impacts can result in more extensive surface water impacts and potentially to long-term water treatment. In all cases additional mitigation has resulted in effective capture and treatment of contaminants. Failure of mitigations to perform is typically caused by design, construction, and operational mistakes. Mitigation frequently fails to perform so it is important to consider the likelihood and consequences of those failures and to identify additional mitigations that can be employed in the event of such failures.

42. Failure Modes Root CausesRecommendations A more systematic and complete effort should be undertaken when collecting data Recognize the importance of thorough hydrological and geochemical characterization Utilize information in a conservative manner to identify and utilize mitigation measures Consider the likelihood and consequences of mitigation failures A more systematic and complete effort should be undertaken to further gather and collect data to test water quality predictions against actual water quality impacts in follow-up to this study with the cooperation of industry and regulators. As the single-most identifiable root cause of water quality predictions failures and impacts, the elimination of geochemical characterization failures can provide the greatest contribution to ensuring accurate water quality predictions and outcomes at hardrock mine sites. Geochemical characterization failures can be addressed by emphasizing fundamental scientific requirements to ensure sample representation, adequate testing, and interpretations that recognize the fundamental uncertainties and limitations of the characterization processes employed. By ensuring adequate geochemical characterization potential for impacts can be recognized and adequate mitigation identified and implemented. As noted in the companion report (Maest et al., 2005), the same geochemical test units should be used for testing of all sources and parameters used to predict water quality impacts. In addition, more extensive information on mineralogy and mineralization should be included in EIS’s. Failure of mitigations to perform is typically caused by design, construction, and operational mistakes. Mitigation frequently fails to perform so it is important to consider the likelihood and consequences of those failures and to identify additional mitigations that can be employed in the event of such failures.A more systematic and complete effort should be undertaken to further gather and collect data to test water quality predictions against actual water quality impacts in follow-up to this study with the cooperation of industry and regulators. As the single-most identifiable root cause of water quality predictions failures and impacts, the elimination of geochemical characterization failures can provide the greatest contribution to ensuring accurate water quality predictions and outcomes at hardrock mine sites. Geochemical characterization failures can be addressed by emphasizing fundamental scientific requirements to ensure sample representation, adequate testing, and interpretations that recognize the fundamental uncertainties and limitations of the characterization processes employed. By ensuring adequate geochemical characterization potential for impacts can be recognized and adequate mitigation identified and implemented. As noted in the companion report (Maest et al., 2005), the same geochemical test units should be used for testing of all sources and parameters used to predict water quality impacts. In addition, more extensive information on mineralogy and mineralization should be included in EIS’s. Failure of mitigations to perform is typically caused by design, construction, and operational mistakes. Mitigation frequently fails to perform so it is important to consider the likelihood and consequences of those failures and to identify additional mitigations that can be employed in the event of such failures.