Video summary

Session 1C: Passive Treatment of Artesian Net Acid Mine Drainage in the Western Interior Coal Field

Main summary

Key takeaways

Science and Nature

Summary of scientific concepts, discoveries, and natural/technical phenomena

1) Geologic setting and AMD source (Western Interior Coal Field / Arkoma Basin)

  • The talk describes arthesian (artesian) mine-water discharges occurring in the Western Interior Coal Field, a region dominated by bituminous coal west of the Mississippi and east of the Great Plains.
  • It focuses on AMD abatement in the Arkoma Basin, a folded and faulted coal basin where coal seams crop out and mine workings dip under the basin.
  • Discharges are linked to upwelling groundwater that had originally been accessed/dewatered by mine shafts/wells, then later continues as artesian flow after closure.

2) Water-quality regimes used to choose passive treatment technology

The presentation groups artesian AMD discharges into categories based on:

  • Flow rate: low-flow vs high-flow/high-velocity discharges
  • Acidity (“net acidic” conditions, i.e., AMD remains acidic even after treatment options)
  • Metal loading, especially:
    • Iron (Fe) and sulfate
    • Aluminum (Al) (key controlling parameter for technology selection)

Technology choice is driven by a conceptual/design chart keyed to:

  • Net acidity (requires selecting the “net acidic” side of the design chart)
  • Ion concentrations > 20 mg/L (guiding treatment pathway options)
  • Aluminum concentration threshold (drives whether an Anoxic Limestone Drain (ALD) is feasible)

3) Passive treatment technologies described

The talk presents multiple passive treatment system components, relying on chemistry and redox conditions rather than active dosing/pumping.

Core components

  • Anoxic Limestone Drain (ALD): sealed limestone trench that generates alkalinity without oxygen; promotes metal precipitation downstream after neutralization/oxidation.
  • Oxidation pond: promotes oxidation of dissolved species (notably iron), encouraging precipitation.
  • Aerobic wetland (“aerobic roads” appears to mean aerobic wetlands): further polishing/precipitation and passive filtration processes.
  • Vertical Flow Pond (VFP): water percolates through a reactive limestone medium under conditions that promote alkalinity generation and subsequent metal precipitation.

System logic

  • A two-step style approach:
    • First zone generates alkalinity and/or oxidizes iron to trigger precipitation.
    • Follow-up oxidation/wetlands polish remaining metals.

4) Levos system case study (low-flow, moderate acidity, lower aluminum)

  • The Levos passive treatment system is used as the case example for a low-flow / moderate-acidity / lower-aluminum discharge.
  • Key chemistry insight:
    • In an ALD, alkalinity generation is primarily from limestone dissolution:
      • CaCO₃ + H⁺ → HCO₃⁻ (bicarbonate; alkalinity)
    • The presentation adds an additional “enhancement” mechanism in ALDs:
      • Carbonic acid formation in the closed ALD system can increase dissolution and thus enhance bicarbonate production (alkalinity boosted further than simple dissolution alone).

Performance/outcomes (approximate)

  • Iron passing through ALD: on the order of tens of mg/L (stated ~30–38 mg/L)
  • Alkalinity increased to ~152 mg/L (average) over system life
  • Rapid reduction of iron after downstream oxidation/precipitation at low-pH-buffered conditions
  • Baseline vs long-term stability:
    • Baseline water quality was reported as similar to long-term monitoring from 2003–2021

5) Hartford system case study (high-flow, medium acidity, high aluminum) → Vertical Flow Pond choice

  • For high-flow, higher metal loading discharges (including iron, aluminum, manganese, sulfate), the presentation highlights the Hartford site in Arkansas.

Hartford system components

  • Vertical flow ponds
  • Oxidation ponds
  • Aerobic wetlands/cells (described as aerobic cells)

Reason for technology selection

  • Water fit the “net acidic” regime and had aluminum > 1.5 mg/L, making ALD less suitable.
  • Therefore, VFP was selected as the technology of choice.

Key outcomes reported (approximate/qualitative)

  • Iron removed aggressively in the initial low-pH oxidation pond (noted as somewhat unanticipated)
  • Alkalinity boost reported as >170 mg/L produced in the two vertical flow ponds
  • Subsequent oxidation pond polished remaining iron and aluminum
  • Manganese was not removed well, with limited removal attributed to the system/technology configuration
  • Flow through VFPs could be uneven due to partial plugging of one vertical unit
  • pH increase and buffering were maintained through discharge duration

6) Stacy discharge (large artesian discharge near Howe, Oklahoma) → methodology for planning

  • The Stacy site is presented as a large-flow artesian well discharge with problematic aluminum (and net acidity).

Recon/baseline values mentioned

  • pH ~4.5
  • Iron ~39 mg/L
  • Aluminum ~3 mg/L (identified as problematic for ALD-type approaches)

Technology implication

  • Based on the design chart and chemistry thresholds, vertical flow ponds are suggested as the likely technology of choice (paralleling Hartford’s regime).

Methodology for developing a remediation plan (outline)

  • Detain right-of-entry from the private landowner
  • Conduct:
    • Topographic study
    • Baseline hydrologic study
  • Run jar tests to evaluate local limestone alkalinity-producing capacity
  • Perform geochemical modeling to predict water chemistry interactions
  • Develop a conceptual passive treatment design
  • Construct the system

7) Use of modeling/software and cost framing

  • The talk mentions using AMD treat software / OSM (as stated) to evaluate treatment pathways and estimate sizing/per-cell performance.
  • Reported cost range (conceptual estimate):
    • Treatment using cells alone estimated around $660,000 for a large flow discharge
    • Additional costs for access roads and drainage ditches would increase totals

Researchers / sources featured

Named individuals and organizations mentioned:

  • Oklahoma Conservation Commission (OCC) (agency role in construction completion for the Levos system)
  • Oklahoma Conservation Commission staff:
    • Henry Roy
    • Mike Sharp
  • Arkansas program:
    • Kevin White (manager)
  • Retired mining specialists:
    • Charles McCool
    • Wayne Van Duren
  • Colleagues from the Office of Surface Mining:
    • Lachelle Harris
    • Brian Hicks

(No other external researchers or publications were explicitly cited in the subtitles.)

Original video