Leviathan Mine Superfund Site

Julie Sullivan March 10, 2020

3/19/2020 1 U.S. Environmental Protection Agency Presentation Topics

• Introduction & Background • Ongoing Early Response Actions • Biomonitoring & Water Quality • Superfund Process • What’s in progress & where are we going? • Questions

U.S. Environmental Protection Agency 2 Leviathan Mine Site • Mining on and off from 1860s – 1960s • 7000 ft elevation • ~200+ acres • ~20+ miles southeast of Lake Tahoe

3/19/2020 3 Past & Present

3/19/2020 4 Acid Drainage Sources • Adit • Pit Underdrain • Channel Underdrain • Delta Seep • Aspen Seep

5 Early Response Actions Early Response Actions 1996 - 1999 - 2009- 1985 2001 - 2009 present present present Pond water High-density Pollution Aspen Seep (lime) Lime treatment sludge (lime) Abatement Bioreactor treatment system treatment Project system system Conducted / Operated by

Lahontan Lahontan Regional Water Regional Water Quality Control Atlantic Richfield Quality Control Atlantic Richfield Atlantic Richfield Board Company Board Company Company

7 Lahontan Water Board Treatment 2018 – 2019 2018 Early Spring • 0.9 million gallons • ~ 400 tons sludge [2017 (majority) + 2018] Summer • 9.2 million gallons • ~ 800 tons sludge

Discharge Criteria met 2019 Early Spring • 4.6 million gallons • ~ 40 tons sludge Summer

• 11.8 million gallons8 • ~ 1000 tons sludge Atlantic Richfield Treatment Aspen Seep Bioreactor High Density Sludge

NaOH addition - neutralize pH Lime – Flocculant – Recycled Solids Sulfate Reducing Bacteria – Precipitates Metal Sulfides Precipitates Metal Hydroxides

ASB Treatment Summary [5 Year Average] HDS Treatment Summary [5 Year Average]

Percent Reduction pH Yearly Avg Percent Reduction pH Yearly Avg Treated Nickel Treated Nickel (gal) Iron (%) (%) Influent Effluent (gal) Iron (%) (%) Influent Effluent

4 million 99% 95% 2.85 7.39 10 million 99.9% 98% 2.98 8.36 Biomonitoring & water quality indicators • Diversity of organisms, esp. of sensitive insects =EPT • Tolerance to water quality impacts • Density of organisms • Changes (e.g. season, year, management & hydrology) • Comparisons of impacted sites to references/controls

midge

stoneflies caddisflies mayfly

crane fly Collecting stream insects near confluence of Leviathan and Mountaineer Creeks How do insects respond to stream chemistry changes?

Population Response to Definition Metric acids and metals How diverse is the Number of Decrease insect community species

Number of EPT Ephemeroptera (mayflies), Plecoptera (stoneflies), and Decrease Trichoptera (caddisflies) Number of intolerant Count organisms sensitive to insects pollution Decrease

% Tolerant Percent of insect insects community tolerant Increase of pollution Dissolved metals in Surface Water – 1998 - 2017 Insect populations – 1998 - 2017

EPT Taxa Diversity: Mountaineer reference Leviathan below mine 25 Sensitive Taxa Group Leviathan @Mountaineer Bryant below confluence

20

15

10 Mean No. EPT per Siteper EPT No. Mean

5

DRY DRY DRY DRY

0

Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall Fall

Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring Spring 19971998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 TARGET: CENTRAL 90% of References Margin of Safety: Not All References Those would include outliers, errors, local & natural sources of disturbance

NMS = non-metric multidimensional scaling U.S. Environmental Protection Agency 16 What’s in progress?

What else are we doing?

3/19/2020 U.S. Environmental Protection Agency 17 Remedial Investigation and Feasibility Study (RI/FS)

Remedial Investigation (RI) Feasibility Study (FS) o Collect & evaluate data o Identify potential clean-up (historical and recent) technologies o Determine nature and o Evaluate clean-up options extent of contamination to reduce risks o Develop ecological and o Present human health risk recommendations for assessments public comment 18 Where are we going?

• Treatability testing • Focused Feasibility Study (FFS) • Proposed Plan • Early Final Remedial Action ROD

• Draft RI • Draft FS • Final RI/FS U.S. Environmental Protection Agency 19 Thank you

Questions?

U.S. Environmental Protection Agency 20