Mining Remed ediation on T Technol olog ogy Advancements U Using Magnesia Applied Chemistries and New Methods to Remediate and Mitigate Heavy Metal Contamination and Mine Drainage Derek Pizarro, CPG General Manager - EnviroBlend - Premier Magnesia, LLC for RE3 Conference, 15-17 September 2015
Mine I e Issues es No Not Rare • Mining has contaminated 40% of Western • Notable headwaters (EPA, 2011) • Columbia River, MT • As, Cd, Cu, Hg, Zn • Issues besides traditional mines • AMD and MD • Mid-Atlantic • Lake Coeur d’Alene, ID • 4,785 mi streams, pH impacted (EPA, 2012) • 75 million tons of heavy metal-impacted sediment, mainly mine-derived • Mainly coal mining (SO2) • Cd, Cu, Pb, Zn • In-situ mined waste, Bevill-exempt under RCRA • Irwin Syncline, PA • Incomplete Inventory • Metals, AMD • Deep mine discharge • US GAO, 2015 Estimated 4,722 mine sites contaminated • Abandoned Mines (BLM, 2015) • >30,000 sites (47 states) • 100,000 sites (CA, NV, UT) • • USDA Forest Service, 2015 27,000 to 39,000 abandoned mines • 20% pose HH/Eco risk •
Mine P e Proc oces esses es • Techniques • Processes • Shaft • Gravity Concentration • Open Pit • Magnetic Separation • Dredging • Electrostatic • In-Situ Solution • Flotation • Leaching • Acid (Cu) • Cyanide (Au) • Salt solution
Acid Rock Dr ck Drai ainag age • Many mines are not underground • Construction projects/sites • Road cuts • OB removal • Same problems in different setting • AMD ARD • EPA 1994, Technical Document- Acid Mine Drainage Prediction • “Mining is a Western problem”
AMD/ARD RD, Ho How does es it form? • Pathway 1, water floods mine • pH decrease is continual • Initial leaching • Amplification cycling • Pathway 2, rock exposed to oxygen • Excavation • Collapse/slide • Metal sulfides oxidize in ore/tailings/dump/ponds • Typically Pyrite • Bacteria can catalyze • H+ released
Why P Problematic? • Formational • Water source • Less competent rock • Rain • Outcropping • Snowmelt • Pond water • Type • Groundwater • Open Pit • Weather event types • Strip • Mountain Topping • Slug • Dry deposition (air) • Flushing • Freeze-thaw • Abandoned/sealed/compromised shafts • Slides • Underground Tunnels • Tailing piles/dumps • Documentation and History
Off ff-Site I Impact • Dry riverbeds • Not connecting to streams or water bodies • Rain event, flash-flood mobilization • Rivers • Path of least resistance • Ecological impacts • pH/sediment flux • Conversion from “dead” to functional stream, 6-11 years avg. (EPA, 2012)
Remed edies es • Chemical Stabilization • Selection • Chemically less hazardous • Interactions • Convert solubility, toxicity, species, or • Metal affinities mobility • Exothermic • Not necessarily physical change(s) • Adverse Interactions • Cost/ton vs. Dosage rate • Solidification • Neutralization/buffering capacity • Physical, possibly monolithic, alters mobility • Not necessarily complete envelopment • Not necessarily without chemical change(s) • Encapsulation • Complete envelopment of contaminant • Coating deprives interaction • Monolithic
Amen endmen ents/Trea eatmen ent Chem emicals Conventional Modern • Lime • Resin • Limestone • Wetlands • Slag • Paste • Magnesia • Oxide • Hydroxide • Blend
Max B Buff ffers • Magnesium hydroxide • pH = 10.35 • pOH = 3.65 • Calcium hydroxide • pH = 12.40 (concentration 112x that of mag) • pOH = 1.60 • Portland Cement Type I, cured 28 days • pH = 13.48 (concentration 1,349x that of mag) • pOH = 0.52
Granular M Magnesia • Non-hazardous • Application • Mixed • Non-toxic • Hydraulically emplaced • Neutralization capacity • Activated magnesia (alternative) • 25-40% more than lime • Same chemistries • 35-50% more than caustic • Plus activator • Product tolerances • Solidification • GRAS • Magnesia-amended OPC • pH • More competent unit • Durability, reduced cracking and • Range control shrinkage • 6-10 S.U. • 1-5% wt./wt. addition • Additives • Easily mixed • Compatibility
Magnesia Slurry y • Non-hazardous • Less sludge formation in RWTP • Non-toxic • Compact sludge • Neutralization capacity • Easily dewatered • 21% more lime • pH • 27% more caustic • Simple rise to 6 S.U. • Product tolerances • Control options • GRAS • Microns matter • Liquor (10) • Lower freezing point • Slurry (45)
Blends ds • pH control • Benefits of both fixation and stasis • Fixative • Co-beneficial effects • Redox • Most suitable treatment for • Autocatalytic SPLP, MEP, and LEAF
Case Studies • Ore Hill Mine (NH) • Confidential Client (Rare Earth Metals) • Callahan Mine Superfund (ME) • Confidential Client (Closed Mine)
CERCLA removal action Treatment area with repository area Human & Biota Exposure Ore H Hill M ill Min ine Former mineral mine (est. ca. 1834) • New Hampshire Fe, Pb, Zn, Ag • Owner : USDA Forest Service Up to 100,000 tons total production • Onsite smelter • 36,000 yd3 tailings and rock • pH (3.3 S.U.) • Pb, Zn, Cu, Cd, As • Previous pumping efforts • Surface water, seeps, tributaries • Toxic, aquatic life impacts up to one mile • Reduce leachability and bioavailability- TCLP, SPLP, MEP • Chemical stabilization, unlined cradle with soil cap • Buffered fixation > PC Type I • Freeze/thaw climate • Lower-construction costs • Lower O&M costs • 50 years vs. 100-1,000 years (PC vs. EB) • Treated leachable metals at or below background • pH restored to neutral range (6.2 S.U.) • Cost Summary • Capital: $3.2M • O&M: $10k/yr (engineering controls) • Monitoring: $30k/yr (testing) •
Rare E Earth M Metal al Former open-pit mine Waterway receptors Min inin ing S Sit ite Off-site impact, long-term exposure, and pond concerns Continental United States • Site Access Owner : Confidential • Mine tailings (5,000 tons) chemically stabilized • Pond sludge (2,500 tons) neutralization and treatment • Treatment in-situ with EnviroBlend • Offsite disposal • Site improvements to manage/minimize run-off • Low dosages for both tailings and sludge • Less over-road trucking • Product Commons, wikipedia • Disposal • Lower disposal fees
Ch Chart rter Co r Contracting Callahan Mine S Super erfund 150-acre former zinc/copper open-pit mine Adjacent residential neighborhood Site R Rem emedia ial A l Actio ion Human contact, long-term exposure, and groundwater concerns Brooksville, ME Owner : Maine Department of Environmental Protection • 3,000 tons Pb mine waste treated on-site with EnviroBlend; offsite disposal (TCLP) • 5,000 cy Pb- and As-impacted soil removed and relocated from residential properties • Excavated, stockpiled, characterized, and disposed of 15,000 tons PCB-impacted soils • Reutilized 22,000 cy of ore/tailings material as multi-layer soil and geotextile cap of soils <10ppm PCBs • Managed a total of 65,000 tons impacted material from mine and adjacent properties • Site improvements to minimize discharge run-off
Form rmer M r Min ine Sit ite- Leachate Co Colle lectio ion Industrial mineral mine Managed landfill unit Syst stem Rain event management Continental U.S. Owner : Confidential • No over-treatment problems (pH 9 max) • Initially, caustic treatment for drainage • Personnel safety/easy handling collection system • Low system maintenance • Changeover to EnviroBlend AQ slurry • Low 32˚F freezing point • No sulfate sludge • High solids level • Produces less soluble salts (TDS) • Reduces metal sludge volume Equivalent Ratio to Other Alkali EnviroBlend AQ 1.00 Hydrated Lime 1.27 Caustic Soda 1.37 Soda Ash 1.82 Caustic Potash 1.92
Question ons? Derek Pizarro, CPG EnviroBlend Premier Magnesia, LLC dpizarro@premiermagnesia.com 610-517-8242 EnviroBlend Sales Offices: Philadelphia (PA), Columbus (NJ), Raleigh (NC), Holland (OH), Sacramento (CA)
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