Investigation of Spot Treatments for Pockets of Acidic Mine Water, Fire Road Mine Minto, NB Atlantic Reclamation Conference NBCC Miramichi October 16 th , 2018 1
The STOZA Corp. Team • Members • Troy Dobson, EIT • Andrew Floyd • Zach McDougall, Dual MIT • Otillia McLaughlin • Spencer Wastle • Mentors • Dr. B. Broster, P.Geo • Dr. J. Day, P.Geo P.Eng • Gilman Violette, P.Eng • Steven Rossiter, Dual MIT • Dr. K. Butler, P.Geo P.Eng 2 • Dr. N. Susak, P.Geo UNB Geological Engineering Senior Design
Introduction • Fire Road Mine opened in 1982 • ~50 000 tons of coal produced • Coal extracted from seam ~0.5m thick • Mine active for 4 years until pH levels declined to 3 and was subsequently shut down • At end of operations, mine was ~120 ha and disturbed area totalled ~300 ha • Currently being treated with a hydrated 3 lime UNB Geological Engineering Senior Design
Introduction • Geological Background 4 UNB Geological Engineering Senior Design
Introduction • Acid mine drainage • Acidic water created by the reaction of sulphide minerals when exposed to air and water • Naturally formed in common sulphide minerals • The oxidation of pyrite is the most common producer of acid mine drainage due to its high sulphur content 5 UNB Geological Engineering Senior Design
Problem Statement • The purpose of this design report is to investigate possible in situ solutions for areas of high acidity, and perform a cost analysis of the possible solutions. 6 UNB Geological Engineering Senior Design
Requirements Constraints • No surficial disturbance • Conduct a site visit to collect field data and evaluate site • Must be within current conditions. solution parameters • Examine possible in situ • Not interfere with the solutions to treat localized hydrogeological dynamics areas of high acidity • Work within seasonal constraints on the mine site • Quantify and incorporate these solutions with the • Complete work within the current site treatment plan outline of the team schedule 7 UNB Geological Engineering Senior Design
Field Work • November 4 th , 2017 • Electromagnetic geophysical survey using an EM31 • Remarked the geophysical survey lines for reproducibility • Water level, temperature and conductivity measurements • 4 water samples collected from standing water on site • 2 soil samples from problematic areas (wells 3 & 17) • 1 soil sample from non-problematic area (well 27) • November 17 th , 2017 • Slug testing 10 wells chosen based on pH data from 8 GEMTEC reports • Delineating standing water on site UNB Geological Engineering Senior Design
Field School Spring 2018 • Follow up EM-31 and ERI surveys were completed in April 2018 • ERI – Electrical Resistivity Imaging an array of electrodes connected to a central power supply measures voltage UNB Geological Engineering Senior Design drop across electrodes to create a pseudo cross-section. • Data is subsequently inverted with software and user defined parameters to create a geologically reasonable cross-section • Very different groundwater conditions with extensive standing water and high 9 volume recharge of clean meteoric water
Geophysical Analysis • The geophysical survey was done using a Geonics EM-31 Ground Conductivity Meter, a Juniper Systems Data Logger and a Garmin GPS. • A total of 7 surveys lines were conducted over the anomalous area of high acidity. • Standing water delineated with Garmin GPS • Used for comparison of previous geophysical work 10 UNB Geological Engineering Senior Design
Geophysical Analysis Suite • 2014: Peak of 42 mS/m STOZA Corp • 2017: Peak of 40 mS/m, similar November 4 th , 2017 anomaly size, smaller maximum survey area • Site continues to improve over time 11 UNB Geological Engineering Senior Design
Geophysical Analysis Suite • Standing water shows no correlation with areas of high apparent conductivity • Peak near Well #17 • Soil samples taken from anomalously high apparent conductivity zones 12 UNB Geological Engineering Senior Design
Field School Spring 2018, EM-31 • Results replicated in different environmental conditions across the site. • Peak value around 40mS/m UNB Geological Engineering Senior Design • Maximum conductivity centered around well 17 13
Field School Spring 2018, ERI UNB Geological Engineering Senior 14 Design
Bench Scale Experiment A bench scale testing program was conducted to develop a solution to treat the areas of anomalously high acidity Choice of solutions based on: • Locally sourced • Economically viable The proposed treatments included • Previous success with • Biosolids - WWTP treating acid mine drainage • Seafood compost - Envirem Organics Inc. (AMD) 15 • Hydrated lime sludge UNB Geological Engineering Senior Design
Bench Scale Experiment • Same volume of soil was used for each column • Same volume of solution was used for each column • The experiment ran for 3 weeks • 140 mL of water weekly • Water collected on a fixed schedule 16 UNB Geological Engineering Senior Design
Bench Scale Experiment 17 UNB Geological Engineering Senior Design
Bench Scale Testing The following tests were performed throughout and at the end of the bench scale experiments: • pH • Water chemistry analysis • Trace element and total dissolved solids analysis outsourced to Research and Productivity Council (RPC) • Soil chemistry analysis • Portable X-Ray Fluorescence (PXRF) 18 UNB Geological Engineering Senior Design
Bench Scale - Water Chemistry pH Analysis from Bench Scale Test Total Dissolved Solids from Bench Scale Test 8 10000 9000 7 8000 6 7000 5 6000 TDS (Mg/L) pH 4 5000 4000 3 3000 2 2000 1 1000 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 19 Time (Weeks) Time (Weeks) UNB Geological Engineering Senior Design
Bench Scale - Water Chemistry Comparing Trace Elements of Problematic Soil to Treatments at Week 3 Problematic Soil - Problematic Soil - Problematic Soil - • Water chemistry Seafood Compost Hydrated Lime Biosolids Element tested by RPC using Removed Added Removed Added Removed Added (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) Inductively Coupled Aluminium - 3.71 - 2.53 0.31 - Plasma Mass Boron 0.15 - 0.25 - 0.21 - Spectrometry (ICP- Cadmium 0.10 - - - - - Calcium 430.00 - 407.00 - - 31.00 MS) Copper 73.01 - 73.61 - - 4.50 Iron 1653.80 - 1469.00 - 150.00 - • Columns are a Lead 3.70 - 3.73 - - 0.67 Lithium - - - - 0.10 - comparison of Magnesium 32.30 - 28.50 - - 1.30 elements in the Manganese 9.10 - 4.74 - 1.20 - Nickel 2.20 - 2.21 - 0.82 - problematic soil Potassium 63.30 - 63.80 - 18.10 - sample minus the Sodium - 81.00 38.80 - - - Strontium 0.52 - 0.49 - 0.15 - elements in each of 20 Zinc 190.93 - 189.07 - - 14.00 the solutions Note: Detection limit for analysis was in ppb. To be considered for added and removed columns, the ion's concentration must be greater than ±0.1 ppm to be significant. UNB Geological Engineering Senior Design
Bench Scale - Water Chemistry • Absolute concentration of metal ions reported in each solution at Week 3 Effluent Water Chemistry Comparison Zn Mn Mg Pb Ca K Fe ≈ 1680 ppm Fe Al 0 100 200 300 400 500 600 700 800 900 1000 Concentrations (ppm) 21 Seafood Compost Hydrated Lime Sludge Control Problematic Soil UNB Geological Engineering Senior Design
Bench Scale - Soil Chemistry Problematic Soil Pre and Post Leaching 80000 70000 Concentration (ppm) 60000 50000 40000 30000 20000 10000 0 Al Fe K S Si Pre Leach Post Leach • PXRF data from the problematic soil pre- and post-leaching 22 • Post-leaching shows lower concentrations of elements as they have been mobilized and carried out by the water UNB Geological Engineering Senior Design
Bench Scale - Soil Chemistry Problematic Soil and Solutions Post Leach 80000 70000 Concentration (ppm) 60000 50000 40000 30000 20000 10000 0 Al Fe K S Si Problematic Soil Pre Leach Problematic Soil Post Leach Hydrated Lime Sludge Post Leach Biosolid Soil Post Leach Seafood Compost Soil Post Leach • PXRF data comparing the soil columns of the solutions to the problematic soil 23 • Post-leaching shows an improvement in soil chemistry as a higher concentration of elements remained in the soil with treatment UNB Geological Engineering Senior Design
Hydrogeology Models • 3D Surface Topography • Water table topography (unconstrained) • Vector plots • 1 st Derivative water table plots 24 UNB Geological Engineering Senior Design
3D Surface Topography Map Water table elevation set at 125m above CGVD2013 (Geodetic Sea level) 25 0m 100m 200m 300m 1:6400 UNB Geological Engineering Senior Design
Water Table Topography N Contours marked at 1m elevation 125m change. 26 E UTM NAD 83 NB Stereographic UNB Geological Engineering Senior Design
Flow Direction N Water table slopes assuming homogeneous site conditions. Significant shallowing in troubled regions. m/m E 27 UTM NAD 83 NB Stereographic UNB Geological Engineering Senior Design
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