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tD St4t UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 10 1200 Sixth Avenue, Sufte 155 Seattle, WA 9S101-3123 OFFICEOFRGI0NAL q PRCct ADMINISTRATOR JUL - I ZOIS Shane McCoy, Program Manager U.S. Army Corps of Engineers, Alaska District 645 G Street, Suite 100-921 Anchorage, Alaska 99501 Dear Mr. McCoy: In accordance with our responsibilities under the National Environmental Policy Act and Section 309 of the Clean Air Act, the U.S. Environmental Protection Agency has reviewed the U.S. Army Corps of Engineers’ February 2019 Draft Environmental Impact Statement for the Pebble Project (CEQ Number 20190018; EPA Region 10 Project Number 18-0002-CUE). The EPA is also supporting the Corps in development of specific sections of the EIS as a cooperating agency in accordance with the cooperating agency agreement. As a cooperating agency, we have participated in meetings and provided comments on early drafts of EN material, including on sections of the Preliminary DEIS in December 2018. We also provided scoping comments to the Corps on June 29, 2018. Project Background The Pebble Limited Partnership (PLP) is proposing to develop the Pebble copper, gold, and molybdenum ore deposit in southwest Alaska. The Pebble deposit lies within the Nushagak and Kvichak watersheds, which together account for more than half of the land area in the Bristol Bay watershed. The proposed project includes an open-pit mine, tailings storage facilities (TSFs), water management ponds, a mill facility, a natural gas-fired power plant, and other mine site facilities. Approximately 1.3 billion tons of ore would be processed at a rate of 180,000 tons of ore per day, over the proposed mine operating life of 20 years. The initial surface disturbance footprint is approximately 8,086 acres and the 608-acre pit would have a maximum pit depth of 1,970 feet. Potentially acid generating (PAG) tailings and non-PAG bulk tailings would be disposed in two tailings facilities that would cover a total of approximately 3,867 acres. Water discharges from the pit lake following mine closure would require water treatment in perpetuity. The proposed project also includes development of a 188-mile natural gas pipeline across Cook Inlet and Lake Iliamna and two compressor stations used to transport natural gas from the Kenai Peninsula to the mine site. The proposed transportation network would include construction of: 77 miles of new roads, including mine and port access roads and spur roads to communities; ferry terminals on the north and south shores of Lake Iliamna for use by an ice-breaking ferry; and the Amakdedori Port on Cook Inlet. In addition to the no action alternative and the proposed action (Alternative I), the DEIS analyzes two additional alternatives and includes variants to the alternatives. 1

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Page 1: Seattle, WA 9S101-3123 q PRCct ADMINISTRATOR JUL I ZOIS · Compensatory Mitigation Plan. This recommendation is further discussed in the EPA’s separate comments to the Corps on

tD St4t

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION 10

1200 Sixth Avenue, Sufte 155Seattle, WA 9S101-3123 OFFICEOFRGI0NAL

q PRCct ADMINISTRATOR

JUL - I ZOIS

Shane McCoy, Program ManagerU.S. Army Corps of Engineers, Alaska District645 G Street, Suite 100-921Anchorage, Alaska 99501

Dear Mr. McCoy:

In accordance with our responsibilities under the National Environmental Policy Act and Section 309 ofthe Clean Air Act, the U.S. Environmental Protection Agency has reviewed the U.S. Army Corps ofEngineers’ February 2019 Draft Environmental Impact Statement for the Pebble Project (CEQ Number20190018; EPA Region 10 Project Number 18-0002-CUE). The EPA is also supporting the Corps indevelopment of specific sections of the EIS as a cooperating agency in accordance with the cooperatingagency agreement. As a cooperating agency, we have participated in meetings and provided commentson early drafts of EN material, including on sections of the Preliminary DEIS in December 2018. Wealso provided scoping comments to the Corps on June 29, 2018.

Project Background

The Pebble Limited Partnership (PLP) is proposing to develop the Pebble copper, gold, andmolybdenum ore deposit in southwest Alaska. The Pebble deposit lies within the Nushagak and Kvichakwatersheds, which together account for more than half of the land area in the Bristol Bay watershed.

The proposed project includes an open-pit mine, tailings storage facilities (TSFs), water managementponds, a mill facility, a natural gas-fired power plant, and other mine site facilities. Approximately 1.3billion tons of ore would be processed at a rate of 180,000 tons of ore per day, over the proposed mineoperating life of 20 years. The initial surface disturbance footprint is approximately 8,086 acres and the608-acre pit would have a maximum pit depth of 1,970 feet. Potentially acid generating (PAG) tailingsand non-PAG bulk tailings would be disposed in two tailings facilities that would cover a total ofapproximately 3,867 acres. Water discharges from the pit lake following mine closure would requirewater treatment in perpetuity.

The proposed project also includes development of a 188-mile natural gas pipeline across Cook Inletand Lake Iliamna and two compressor stations used to transport natural gas from the Kenai Peninsula tothe mine site. The proposed transportation network would include construction of: 77 miles of newroads, including mine and port access roads and spur roads to communities; ferry terminals on the northand south shores of Lake Iliamna for use by an ice-breaking ferry; and the Amakdedori Port on CookInlet.

In addition to the no action alternative and the proposed action (Alternative I), the DEIS analyzestwo additional alternatives and includes variants to the alternatives.

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Overview of Comments and Recommendations

We appreciate the progress that the Corps has made and the improvement to the analysis resulting fromengagement with the EPA early in the NEPA process. However, the DEIS appears to lack certain criticalinformation about the proposed project and mitigation, and there may be aspects of the environmentalmodeling and impact analysis which would benefit from being corrected, strengthened, or revised.Because of this, the DEIS likely underestimates impacts and risks to groundwater and surface waterflows, water quality, wetlands, aquatic resources, and air quality from the Pebble Project. Inclusion ofthe additional information and analyses we have identified, or further explanation in the EIS of theseissues, is essential to more fully evaluate and disclose the potential project impacts and identifypracticable measures to mitigate those impacts. The EPA is committed to working with the Corps toprovide our expertise where it can be of assistance.

Our priority comments and recommendations are summarized below. We have enclosed detailedcomments explaining these priority comments and recommendations. Our detailed comments alsoaddress other issues identified in the EPA’s review of the DEIS. including geohazards, environmentaljustice, and subsistence.

Project Description and Mitigation DetailsThe DEIS and supporting reference information acknowledge that key aspects of the Pebble Project areat a conceptual level (i.e., early or initial stage) of design and development. Critical but conceptuallydeveloped project components include: the open pit mine dewatering system; the dams retaining themine’s tailings and main water management pond; the collection, pumpback, and monitoring systemsfor managing seepage from the TSFs and main water management pond; and the closure water treatmentplant. Critical plans that are yet to be developed or are only conceptually described in the DEIS includeplans for: mine reclamation and closure; environmental monitoring; adaptive management; tailings andwaste rock characterization and management; fugitive dust control; and strategic timing of waterdischarges.

More detailed versions of these project components and plans, however, are critical to the evaluation ofenvironmental impacts, alternatives and mitigation. Without more detail, many of the predictionsassociated with these components and plans in the DETS do not appear to be fully supported based onthe current level of documentation. Given the scale of the project and importance of the aquaticresources in the Bristol Bay watershed, we recommend including more developed designs and plans inthe EIS to provide a level of detail that will allow for more meaningful disclosure of the project’spotential impacts and the effectiveness of its pollution control infrastructure and plans that are importantfor environmental protection and mitigation.

Range ofAlternativesThe DEIS predicts that groundwater contamination would occur under the bulk TSR We thereforerecommend that the EIS include as an alternative, variant, or mitigation measure the use of a Liner underthe bulk TSF (with appropriate overdrains to ensure stability). In addition, we recommend that the EISdiscuss in detail an alternative or variant that includes the infrastructure elements that would beanticipated under the Pebble Mine Expanded Development Scenario (i.e., diesel pipeline, port site atIniskin Bay). This would enable consideration of options that would avoid or minimize cumulativeimpacts that would occur as result of redundant infrastructure associated with expanded development.The EPA recommends that these alternatives or variants be further analyzed in the NEPA analysis asthey may be components for the least environmentally damaging practicable alternative (LEDPA) under

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Section 404 of the Clean Water Act. We recommend that the aLternatives analysis provide theinformation necessary to support an evaluation of alternatives under the Clean Water Act Section404(b)(l) Guidelines, including information to support identification of the LEDPA. This issue is furtherdiscussed in the EPA’s separate comments to the Corps on the Clean Water Act Section 404 PublicNotice.

Alternative 3 includes a port site variant that would include a water treatment plant at the port to treatand discharge process wastewater from the concentrate pipeline to Cook Inlet. The discharge of processwastewater alone as defined under this variant likely is not allowed under the Clean Water Act and theNational Pollutant Discharge Elimination System (NPDES) regulations (see 40 CFR 440 Subparts J andL). Therefore, we recommend that this variant be reconsidered.

Groundwater and Streaniflow InpactsThe DEIS relies on watershed, groundwater, and water balance models to predict how mine siteactivities will change groundwater conditions and impact surface water and aquatic resources. Theuncertainty analysis for the groundwater model, however, concludes that the model may significantlyunderpredict the amount of water produced during mine pit dewatering. The DEIS discloses that thiscould result in the groundwater zone of influence being larger than predicted and North Fork Koktuli,South Fork Koktuli, Upper Talarik Creek, and tributary stream flows being reduced to a greater extentthan is currently predicted in the DEIS. Significant adverse impacts to wetlands and to streams withdocumented anadromous fish occurrence may result from such stream flow reductions. We recommendthat the groundwater model be revised to reduce this uncertainty and provide more accurate predictionsassociated with open pit dewatering. We have additional recommendations to verify the water balancemodel and clarify how uncertainties associated with the watershed model effect EIS predictions. Werecommend that the ETS fully analyze the potential adverse impacts to groundwater, wetlands, andstreams with documented anadromous fish occurrence based on the results of the revised modeling.

Water Quality ImpactsThe DEIS may substantially underpredict potentially significant impacts to water quality. Our keycomments are:

• The DEIS provides inadequate support for several assumptions regarding the behavior ofleachate and relies on very limited sample representativeness for prediction of acid rock drainageand metal leaching. This may result in unanticipated leaching of metals/metalloids at elevatedconcentrations;

• The DEIS lacks critical details regarding the design and operation of the water treatment plants,particularly at closure. The DEIS reference material states that there is insufficient availableinformation to evaluate the effectiveness of the closure water treatment plant to meet waterquality criteria. This prevents meaningful anaLysis and disclosure of potential water qualityimpacts related to water treatment;

• As a result of groundwater model uncertainty, the DEIS states that the water treatment plantsmay need to treat and discharge more mining process water than that for which the plants arecurrently designed. Significant impacts to water quality could occur if that is the case; and

• Use of conceptual drainage and seepage containment systems for the TSFs and watermanagement pond do not fully support the DEIS assumption that 100% of the seepage would becaptured.

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The EPA also recommends that the EIS include a data quality assessment for background water qualitydata, a modeling sensitivity analysis of the water quality modeling and inputs, a reasonably completeanalysis of water quality impacts in the closure and post-closure phases, and monitoring and adaptivemanagement plans.

Wetlands Impacts and Conipensaron’ MitigationThe Pebble Project would result in the permanent loss of approximately 3,560 acres of jurisdictionalwetlands and other aquatic resources, including 3,443 acres of wetlands, 55 acres of lakes and ponds, 81miles (50 acres) of stream channels, and 11 acres of marine waters. An additional 510 acres of streams,wetlands, lakes, ponds, and marine waters would be temporarily filled for construction access, and 2,345acres would experience secondary impacts due to groundwater drawdown (449 acres) and fugitive dust(1,896 acres). The DEIS, however, does nor fully identify and characterize existing aquatic resourcesand wetland functions to establish the environmentaL baseline for an impact analysis and mitigationconsiderations because the analysis area is limited and salient available site-specific data is not utilized.In addition, the EPA recommends a more complete analysis of secondary/indirect effects, which isimportant to analyze project impacts and compare alternatives.

In terms of compensatory mitigation, the draft Compensatory Mitigation Plan includes only a conceptualdiscussion, notwithstanding the proposed project’s substantial impacts to wetlands and aquaticresources. The plan also does not fully address the types of direct and indirect impacts to waters of theU.S. that may occur and does not identify specific mitigation projects. Therefore, the availability,practicability, and effectiveness of compensatory mitigation to offset unavoidable impacts isunsupported. To ensure disclosure of practicable means to mitigate the direct, indirect, and cumulativeimpacts of the Pebble Project, the EPA recommends the EIS include a reasonably detailed draftCompensatory Mitigation Plan. This recommendation is further discussed in the EPA’s separatecomments to the Corps on the CWA Section 404 Public Notice.

Impacts to Fish and Fish HabitatThe impacts on ecologically important streams, wetlands, lakes, and ponds and the fishery areas theysupport should be more fully addressed in the EIS. The EPA recommends significant improvements to:habitat characterization, assessment, quantification, and spatial referencing; assessment of linkagesbetween the loss and/or degradation of habitat and impacts to fish species and life stages (i.e., incubatingeggs, spawning fish, and rearing juveniles); groundwater and surface water flow characterization at ascale that is more relevant to fish and fish habitat; and analysis of the potential population-level effectsand effects on genetic diversity in the context of the Bristol Bay salmon portfolio. We recommend thatthe analysis in the DEIS be revised to address these issues.

Air Quality ImpactsPriority issues associated with the air quality analysis include:

• Particulate matter impacts from the mine site may be underpredicted in the EIS based on themodeling parameters used to predict impacts from the mine pit; and

• Assumptions and potential errors in the air quality modeling assessment for the port facilitiesinclude lack of evaluation of substantial mobile emissions from vessel traffic, and differences in

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meteorological conditions at the Diamond Point port site as compared to the Amakdedori portsite.

Our detailed comments provide recommendations to strengthen the air quality analysis.

Tailings Containnzent and Spill RiskThe DEN does not fully characterize the stability and performance of the dams containing tailings andcontact water in the event of an earthquake. A deformation analysis and seismic safety factor weredetermined for a past design of the bulk TSP, but this analysis was not provided for the current TSF damdesign or for the other dams. The TSFs and main water management pond dams are significantstructures that range in height up to 545 feet with combined lengths of 7.2 miles (for the TSP dams) and3.6 miles (for the WMP dams). We recommend seismic safety factors and potential earthquake inducedstability impacts be assessed for these dams so that the ETS discloses how the dams will be impacted bya potential earthquake.

The DEIS, based on conclusions of a Failure Modes Effects Analysis (FMEA), does not evaluate thepotential release of tailings from the bulk TSFdue to a dam breach or failure. The FMEA risk register,referenced in the DEIS, identifies a number of adverse factors that could occur during engineering,construction, and operations, but assumes that all of these challenges would be overcome. Support forthis determination is limited given the simplified conceptual dam designs, lack of operational,monitoring, and closure plans and lack of representative seismic analysis for the bulk TSP. Werecommend that a bulk TSP breach or failure scenario be developed, and potential impacts be evaluatedand disclosed.

In addition, the spill risk analysis for concentrate and tailings warrants improvement. The currentanalysis may underpredict impacts of spills due to assumptions and incomplete information related tothe role of oxygen in aquatic environments, timing for release of mineral components, and reactivity inporewater. We recommend revising the analysis to address these issues, so that potential adverseimpacts to water and sediment quality from leaching of metals are fully disclosed, as well as anyassociated impacts on fish populations.

Indirect Effects and Cumulative ImpactsThe DEIS summarizes potential indirect effects and cumulative impacts in genera! terms, with limitedquantitative analysis of large-scale additional impacts resulting from reasonably foreseeable futureactions. We recommend a more robust evaluation of indirect impacts and cumulative effects,particularly in terms of the Pebble Mine Expanded Development Scenario.

Conclusion

The enclosure includes detailed discussion and specific recommendations regarding the key issuessummarized above, as well as other issues identified in the EPA’s review. Given the substantial potentialimpacts and risks of the proposed project and weaknesses in the DEIS, the DEIS likely underestimatesadverse impacts to groundwater and surface water flows, water quality, wetlands, fish resources, and airquality. Therefore, conclusions that the project will not violate applicable water quality and air qualitystandards should be further supported. Our detailed comments include recommendations to provide

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significant additional information about key project components and plans and improve theenvironmental modeling and other aspects of the impact assessment)

We will continue to work constructively with the Corps as a cooperating agency, providing specialexpertise in specific areas requested by the Corps, including: alternatives; recreation; aesthetics andvisual resources; soils; surface- and groundwater hydrology; water and sediment quality; wetlands andspecial aquatic sites; vegetation; and mitigation. We also continue to request the ability to assist theCorps in additional areas of the Pebble Project EIS, including fisheries and air quality, where we havespecial expertise and jurisdiction. In addition, we recommend that resource-specific interagencytechnical workgroups be developed to work through significant issues. We look forward to working withyou and the other cooperating agencies on the next steps in the NEPA process.

if you have questions concerning our comments, please contact Patty McGrath, Mining Advisor andlead for the Pebble Project NEPNPermitting Team, at [email protected] or 206-553-6113, orMolly Vaughan, NEPA Reviewer, at [email protected] or 907-271-1215.

Regional Administrator

Enclosure: U.S. Environmental Protection Agency Detailed Comments for the Pebble Project DraftEnvironmental Impact Statement

cc: Colonel Phillip Borders, USACE Alaska District

‘Effective October 22. 2018, the EPA no longer includes ratings in our comment letters. Information about this change isexplained in the Memorandum on Changes to EPA’s Environmental Review Rating Process, available at

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Page 16: Seattle, WA 9S101-3123 q PRCct ADMINISTRATOR JUL I ZOIS · Compensatory Mitigation Plan. This recommendation is further discussed in the EPA’s separate comments to the Corps on

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