Monitoring and Modeling of Acid Mine Drainage from Waste Rocks Dumps

201 Pages·2001·20.15 MB·English

MONITORING AND MODELING OF
ACID MINE DRAINAGE FROM
WASTEROCK!3DUMPS
La Mine Doyen Case Study
MEND Report 1.14.2 g
This work was done on behalf of MEND and sponsoredb y
Cambrior Incorporated,
Lac Minerals,
the Province of Québec , and
the Canada Centre for Mineral and Energy Technology (CANMET)
through the CANADA/Québcc Mineral Development Agreement
June 1994
GREGI
GROUPED E RECHERCHE EN GÉOLOGIE DE L’INGÉNIEUR
RAPPORT GREGI 1994-12
MONITORING AND MODELING OF ACID MINE
DRAINAGE FROM WASTE ROCKS DUMPS
LA MINE DOYON CASE STUDY
BY
Pierre Gélinas, René Lefebvre, Marc Choquette,
Denis Isabel, Jacques Locat and Roger Guay
Final Report presentedt o
MEND Prediction committee
DSS contract 23440-3-923V ol-SQ
August 1994
Revised September1 994
DÉPARTEMENT DE GÉNIEG ÉOLOGIQUE
Facultéd ess ciencese t de génie
Cité Universitaire, Sainte-Foy,
Québec GlK 7P4
MONITORING AND MODELING OF ACID MINE DRAINAGE
FROM WASTE ROCK DUMP - LA MINE DOYON CASE STUDY
EXECUTNE SUMMMY
This report presents a summary of work done on the monitoring and modeling of acid mine
drainage from the South waste rock dump at La Mine Doyon for the period between September
1991 and December 1993. The main purposeo f the study was to measurep hysical and chemical
properties of an actual waste dump and to identify the key processesc ontributing to the generation
of acid rock drainage: hydrology, geochemistry, microbiology, and physical processess uch as
oxygen, mass, and heat transfer.
Important physical parameterss uch as climatic data, temperaturep rofiles within the dump, total
dischargeo f acid drainage from collecting ditches and chemical composition of the effluents were
monitored on a regular basis. Other parametersw ere measuredo nce or at irregular intervals: gas
composition, piezometric levels, leachatec omposition in the unsaturatedz one, infiltration rates,
particle size, surfacet emperature. It is the fïrst time that such a coherenta nd comprehensives et of
parametersis assembledin a large waste rock dump.
The data collected were presentedi n a progressr eport in November 1992 (Gélinas et al. 1992) and
a series of interim reports on specific topics from February 1993 to March 1994: Guay, 1993
(procedure to enumerate iron bacteria); Choquette et al., 1993a (rapid chemical techniques to
monitor acid drainage) and 1993b (chemical monitoring data at Mine Doyon); Lefebvre et al.,
1993 (heat transfer analysis); Locat et al., 1994 (physico-chemicala nd mechanical properties of
waste rocks); Choquette and Gélinas, 1994 (mineralogy and geochemicalp rocesses); Isabel et
al., 1994 (hydrology and water budget); Guay, 1994 (microbiological diversity). Reports from
Phase1 of the project are also used here to presentd ata on monitoring installations and complete
chemical analyses( including trace metals)o f selectedm onitoring points (Gélinase t al. 1991).
Again, this report does not present all the data available at the site but rather integrates the
information and analysesf rom the above sources,t o present a general synthesiso f physical and
chemical processesa ctive in an acid generating waste rock dump. We are also presenting some
new information on numerical modeling of acid mine drainagep roduction in waste dumps.
SURVEILLANCEETMODÉLISATIONDUDRAINAGEMINIERACIDEDANS
UNEH~EDESTÉ~LES-ÉT~DEDUCASDEL~MINEDOYON
SOMMAZRE
Voici un resumé du travail de surveillance et de modélisation du drainage minier acide dans
la halde sud de la mine Doyon, entre septembre 1991 et décembre 1993. Le but premier de
l’étude était de mesurer les propriétés physiques et chimiques d’une halde de stériles et de
determiner les principaux processusq ui contribuent au drainage minier acide : hydrologique,
géochimique et microbiologique ainsi que les processusp hysiques comme le transfert
d’oxygène, le transfert de massee t la dissipation de la chaleur.
On a surveillé régulièrement l’évaluation des paramètresp hysiques importants comme les
données climatiques, les profils de température dans la halde, la quantité totale du drainage
acide dans les fossés collecteurs et la composition chimique des effluents. Les autres
paramétres qui ont été mesuresu ne fois ou a intervalles irréguliers sont : la composition des
gaz, les niveaux piézométriques, la composition du lixiviat dans la zone non saturée, les taux
d’infiltration, la granulométrie et la température de la surface. C’est la première fois que l’on
constitue un ensemble de paramètres aussi cohérent et aussi complet pour une halde de
stériles aussi vaste.
Les données recueillies ont été présentéesd ans un rapport d’étape en novembre 1992
(Gélinas et coll. 1992) et dans une série de rapports provisoires sur des projets précis remis
entre février 1993 et mars 1994 : Guay, 1993 (procédure pour le dénombrement des
bactéries du fer); Choquette et coll., 1993a (techniques chimiques rapides pour la
surveillance du drainage minier acide) et 1993b (donnéesd e surveillance chimique à la mine
Doyon); Lefebvre et coll. 1993 (analyse des transferts thermiques); Locat et coll., 1994
(propriétés physico-chimiques et mécaniquesd es stériles); Choquette et Gélinas, 1994
(minéralogie et processus géochimiques); Isabel et coll., 1994 (hydrologie et bilan
hydrologique); Guay, 1994 (diversité microbiologique), On s’est aussi servi des rapports de
la première phase du projet pour obtenir des données sur les installations de surveillance et
des analyses chimiques complètes (y compris sur les métaux-trace) des points de surveillance
choisis (Gélinas et coll., 1991).
Je vous rappelle que le rapport ne fournit pas toutes les donnéesd, isponibles à la mine, mais
regroupe les renseignementse t les analysesf ournis par les sources susmentionnéesa fin de
présenter une synthèse générale des processusp hysiques et chimiques actifs dans une halde
de stériles qui produit du drainage acide. Nous vous donnons aussi de nouveaux
renseignementss ur la modélisation numérique de la production du drainage acide dans les
haldes de stériles.
ii
Table of contents
Executive Summary ................................................................................ i
Table of contents ................................................................................... ii
List of tables ........................................................................................ vi
...
List of figures .................................................................................... VI11
1. INTRODUCTION ........................................................................ 1.1
1.1 Scope and objectives of the Mine Doyon project ......................... 1.1
1.2 Site characteristics .................................................................. 1.2
1.2.1 Location.. ........................................................................... 1.2
1.2.2 Generalg eology of the Mine Doyon site ........................................ 1.2
1.3 Acid rock drainage at Mine Doyon ........................................... 1.7
1.3.1 Early observations. ................................................................ 1.7
1.3.2 Estimateso f acid/basea ccountinga nd pyrite content. ......................... 1.8
1.4 Organization of the report ....................................................... 1.8
2. PIELD INSTRUMENTATION, CHARACTERIZATION AND
MONITORING ............................................................................ 2.1
2.1 Introduction.. ........................................................................ 2.1
2.2 Instrumentation ..................................................................... 2.1
2.2.1 Exploration trenches. .............................................................. 2.1
2.2.2 Boreholesi nstallation. ............................................................. 2.2
2.2.3 Boreholese quipment. ............................................................. 2.2
2.2.4 Lysimetersi nstallation. ............................................................ 2.4
2.2.5 Collection ditches and weir stations.. ............................................ 2.4
2.2.6 Water samplesc ollection .......................................................... 2.5
2.2.7 Weathers tation. .................................................................... 2.5
2.3 Physical characterization.. ....................................................... 2.6
2.3.1 Particles ize ......................................................................... 2.6
2.3.2 Water content. ...................................................................... 2.7
2.3.3 Bulk density ........................................................................ 2.7
2.3.4 Porosity ............................................................................. 2.9
2.3.5 Degree of saturation ................................................................ 2.10
2.3.6 Gas composition and pressure. ................................................... 2.10
2.3.7 Infrared thermography ............................................................. 2.13
. . .
ln
3. MECHANICAL AND PHYSICAL PROPERTIES OF MINE DOYON
WASTE ROCKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*................. 3.1
3.2 Materials investigated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*............. 3.2
3.3 Specific surface area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2
3.4 Mechanical tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3
3 5 Acoustic celerometer test . . . . . . . . . . . . . . . ..*...................................... 3.6
3.6 Evaluation of pyrite surface area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7
3.6.1 Hydrogen peroxide (H202) tests.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7
3.6.2 Imageanalysisofpyritecontent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8
3.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9
4. WATERBALANCEFORTHEWASTEROCKDUMP.. ................. -4.1
4.1 Introduction .......................................................................... 4.1
4.1.1 Problem definition ................................................................. 4.1
4.1.2 Objectives ........................................................................... 4.1
4.1.3 Methodology.. ..................................................................... .4.2
4.2 Hydrologie data collection ....................................................... 4.2
4.2.1 Regional meteorological data .................................................... .4.2
4.2.2 On site meteorological instrumentation .......................................... 4.3
4.2.3 Local meteorological data ......................................................... 4.5
4.2.4 On site hydrological instrumentation.. ........................................... 4.5
4.2.5 Hydrological data .................................................................. 4.6
4.3 Data analysis .......................................................................... 4.11
4.3.1 Annual and monthly hydrologie bbalances ...................................... 4.11
4.3.2 Single rainfall runoff events analysis ........................................... .4.16
4.3.3 Hydrogeologic modeling ......................................................... .4.20
4.3.4 Overall hydrologie balance ........................................................ 4.30
4.4 Conclusion ............................................................................ 4.33
5. GEOCHEMICAL, MINERALOGICAL AND MICROBIOLOGICAL
CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1
5.1 Introduction .......................................................................... 5.1
5.2 Monitor-mg and geochemical evolution of acid rock drainage ...... .5.2
5.2.1 Monitoring ARD ................................................................... 5.2
5.2.2 ARD in the saturated zone of the waste rock dump ............................ 5.3
iv
5.2.3 Groundwaters ampleso utside the waste rock dump ........................... 5.5
5.2.4 Acid rock drainage at weir stations ............................................... 5.7
5.2.5 Acid leachatein the gravity lysimeters ........................................... 5.15
5.2.6 Extractedp ore water samples.. ................................................... 5.15
5.2.7 Chemical characterization using a leaching technique... ....................... 5.2 1
5.3 Mineralogical transformations associated with ARD .................. .5.2 1
5.3.1 Oxidation processes.. .............................................................. 5.22
5.3.2 Processeso f neutralization. ....................................................... 5.23
5.3.3 Samplec ollection and methodso f investigation. ............................... 5.24
5.3.4 Results.. ............................................................................. 5.26
5.3.5 Discussion .......................................................................... 5.42
5.3.6 Conclusion and recommendationsf rom mineralogical observations.. ....... 5.48
5.4 Microbiological diversity and ARD production .......................... 5.49
5.4.1 Biological oxidation processes.. ................................................. 5.49
5.4.2 Samples collection and methods of investigation.. ............................. 5.49
5.4.3 Results.. ............................................................................. 5.51
5.4.4 Conclusionsf rom microbiological observations. .............................. 5.56
6. THERMAL PROCESSES DURING AMD PRODUCTION . . . . . . . . . . . . . . . .6.1
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1
6.2 Interpretation of cyclic temperature variations ........................... 6.2
6.2.1 Descriptiono f cyclic temperaturev ariations .................................... 6.2
6.2.2 Fourier analysiso f cyclic temperaturev ariations. .............................. 6.4
6.2.3 Evaluation of the thermal propertieso f waster ocks ........................... 6.9
6.3 Heat production in waste rocks ................................................. 6.12
6.3.1 Simple conductionm ode1. ........................................................ 6.12
6.3.2 Conduction and advection mode1. ................................................ 6.13
6.3.3 Air convectionc onceptuaml ode1.. ............................................... 6.17
7. NUMERICAL MODELING OF AMD PRODUCTION IN WASTE
ROCKS ...................................................................................... .7.1
7.1 Introduction .......................................................................... 7.1
7.1.1 Numerical modeling objectives. .................................................. 7.1
7.1.2 Requiredm ode1c haracteristics.. ................................................. 7.2
7.1.3 Description of the approacht aken. ............................................... 7.3
7.2 Reaction tore mode1. .............................................................. 7.4
7.2.1 Generalc oncepts. .................................................................. 7.4
7.2.2 Formulation of the reaction tore mode1. ......................................... 7.6
V
7.3 Numerical methods used in TOUGH AMD ................................ 7.10
7.3.1 Physicalp rocessesa nd equation system. ....................................... 7.10
7.3.2 Primary and secondai-yth ermodynamicv ariables. ............................. 7.13
7.4 TOUGH AMD description ....................................................... 7.14
7.4.1 TOUGH2 features. ................................................................ 7.14
7.4.2 Changes required to create TOUGH AMD ...................................... 7.14
7.4.3 TOUGHAMDgeneralcapabalities.. ............................................ 7.15
7.5 Applications of AMD numerical modeling ................................. 7.16
7.5.1 Mode1p arametersa nd conditions ................................................ 7.16
7.5.2 Physicalc onditions within the dump ............................................. 7.18
7.5.3 Physical transfer processes.. ..................................................... 7.18
7.5.4 Evolution of AMD productionw ith time ........................................ 7.22
7.5.5 Impact of permeability anisotropy.. .............................................. 7.24
7.5.6 Effects of a border membrane to control AMD production.. .................. 7.24
7.5.7 Mode1 limitations and future research. ........................................... 7.30
8. CONCLUSION ................................................................................ 8.1
8.1 Contributions to WRD characterization ..................................... 8.1
8.2 Contributions to the understanding of key processesc ontroling acid
rock drainage ........................................................................ 8.4
8.3 Modeling water, mass, and energy tranfers in WRD.. ................. .8.5
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rl
vi
List of tables
Chapter 1.
Table 1.1 Maximum potential acidity from sulfides content and neutralization potential from
carbonate analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9
Chapter 3.
Table 3.1 Results of standard tests .................................................................... 3.4
Table 3.2 Changes in specific surface during Los Angeles tests .................................. 3.4
Table 3.3 Compression and shear waves velocities in waste rocks .............................. 3.6
Table 3.4 Pyrite grains dimensions from image analysis .......................................... 3.8
Chapter 4.
Table 4.1 Location of regional weather sations .................................................... .4.3
Table 4.2 Monthly precipitations for 199 1 ......................................................... .4.12
Table 4.3 Monthly precipitations for 1992 ......................................................... .4.12
Table 4.4 Results of base flow separation ........................................................... 4.12
Table 4.5 List of site subdivisions.. ................................................................. .4.13
Table 4.6 Watershed surface composition .......................................................... .4.15
Table 4.7 Base flow for the WRD and other soi1 surfaces.. ...................................... .4.15
Table 4.8 Selected rainfall-runoff events ............................................................ 4.16
Table 4.9 Results of single event analysis .......................................................... .4.17
Table 4.10 Geological layers definition for the MODFLOW mode1 .............................. .4.20
Table 4.11 Hydrogeologic balance.. .................................................................. .4.28
Table4.12 Waterbudgetsummary.. ................................................................. .4.33
Chapter 5.
Table 5.1 Chemical analysis of the leachate in the piezometers inside the dump.. ............. .5,4
Table 5.2 Chemical analysis of the leachate in the peripheral piezometers.. .................... .5.6
Table 5.3 Typical chemical analysis of the leachate at the three weir stations .................. .5.8
Table 5.4 Ditches acidity. Statistical data 1991-1993 .............................................. 5.9
Table 5.5 Acid production summary from the South dump (1991-1993) ...................... .5.14
Table 5.6 Composition of the leachate in lysimeters T92-1 (3A, 3B and 4A). ................. .5.16
Table 5.7 Composition of the leachate in lysimeters T92- 1 (4B, 5A and 5B). ................. .5.17
Table 5.8 Composition of the leachate in lysimeters T92-2 (3A, 3B and 4A). ................. .5.18
Vii
Table 5.9 Composition of the leachate in lysimeters T92-2 (4B, 5A and 5B) . . .. . .. .. . .. . .. . . . . 5.19
Table 5.10 Chemicald ata T92-2 Chemicala nalysiso f extractedp ore-watera nd characteristicso f
leach solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.20
Table 5.11 Qualitative mineralogicalc ompositiono f boreholeB H-7, T91-2 and T92-2.. . . . . . .5.28
Table 5.12 Base equationsu sedt o calculatem asst ransfer in BH-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.44
Table 5.13 Specific equationsu sedt o calculatem asst ransfer in BH-7 (exclusiveo f chlorite and
muscovite). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.45
Table 5.14 Chemical compositiono f mineralsu sedi n the masst ransferc alculations. . . . . . . . . . .5.45
Table 5.15 Calculatedm ineral masst ransferi n BH-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.46
Chapter 6.
Table 6.1 Thermal conductivity and fluid flux from Stallman’ss olution . . . . . . . . . . . . . . . . . . . . . . . .6.10
Chapter 7.
Table 7.1 Phasesa nd componentso f the system. .................................................. 7.13
Table 7.2 Physicalp ropertieso f the basec ase. ..................................................... 7.17