final sdeis comments from polymet

PolyMet Mining Comments on theSupplemental Draft Environmental Impact StatementFor the NorthMet Mining Project and Land Exchange

March 13, 2014

Comment 1.

Executive Summary, p. ES-7

The third paragraph states that the United States Army Corps of Engineers (USACE)and the Minnesota Department of Natural Resources (MDNR) studied the originalNorthMet Project Proposed Action between 2005 and 2009. Use of the defined termNorthMet Project Proposed Action in this context is confusing because the proposedaction studied in the Draft EIS was substantially different than the proposed action beingstudied in the SDEIS. To avoid confusion over the nature of the alternatives studied inthe two documents, PolyMet recommends changing the language to state thatBetween 2005 and 2009, the USACE and MDNR evaluated PolyMets originalmining proposal.

Comment 2.

Executive Summary, pp. ES-7 and ES-10

The terms NorthMet Mining Project and Land Exchange, rather than the definedterms NorthMet Project Proposed Action and Land Exchange Proposed Action, areused on these pages. To avoid confusion, PolyMet recommends consistent use of thedefined terms.

Comment 3.


Under the heading Cooperating Agencies, the SDEIS describes USEPAsresponsibilities to review and comment on an EIS under Section 309 of the Clean AirAct. USEPA does this for all Environmental Impact Statements, even when it is notacting as a cooperating agency. USEPA has formally participated in the preparation ofthe current SDEIS as a cooperating agency, which is not the same thing as fulfilling itsresponsibilities under CAA Section 309. PolyMet recommends clarifying this point byadding a sentence to this paragraph that explicitly notes EPAs status as a cooperatingagency.

PolyMet CommentsNorthMet Mining Project and Land Exchange SDEIS

March 13, 2014

Page 2 of 70

Comment 4.


The first sentence on this page indicates that completion of mining in the East Pit willoccur in approximately year 11 after the start of mining. By contrast, the first sentencein the paragraph following the three bullet points states that mining in the East Pit willend by year 11 after the start of mining. The second statement is inaccurate. Miningin the East Pit will end approximately 11 years after mining, but not necessarily by year11.

Comment 5.

Executive Summary, pp. ES-23 ES-24

In the last paragraph of the Mining Operations Section on page ES-23, the SDEISdefines process water in connection with the Mine Site. On page ES-24, the SDEISrefers to Plant Site process water. To clarify and define terms, page ES-23 should bechanged to refer to Mine Site process water, and Plant Site process water should bedefined by adding a sentence (see bold text below) to the last paragraph of theProcessing Operations Section on page ES-23:

Water seepage from the Tailings Basin would be collected by the groundwatercontainment system and sent to either the Tailings Basin pond or the Plant Site WWTP.All other water that is collected at the Plant Site, such as water used duringprocessing, and water that contacts the plant site facilities (collectively referredto as Plant Site process water) will also be treated at the Plant Site WWTP. Treatedwater would be used to augment flows in the streams that would otherwise receivereduced flows because of the Tailings Basin groundwater containment system.

Comment 6.

Executive Summary, pp. ES-35 to ES-36

PolyMet recommends that the Executive Summary explicitly state that aluminumconcentrations in the water, or the lowering of the hardness caused by storm water,represent natural or background concentrations and/or are the result of naturalprocesses, not process water from the NorthMet Project.

Comment 7.

Executive Summary, pp. ES-38 ES-39

The SDEIS indicates that the NorthMet Project could potentially affect water quality byincreasing solute concentrations above Class 2B (aquatic life) standards. This appears


March 13, 2014

Page 3 of 70

to refer to the aluminum and lead exceedances discussed earlier in the ExecutiveSummary. As explained in Comment 6 above, PolyMet recommends that the ExecutiveSummary explicitly state that any such exceedances would be the result of backgroundand/or naturally occurring concentrations or processes, not process water from theNorthMet project.

Comment 8.


The second full paragraph beginning with the phrase natural resources does notaccurately summarize the discussion of cultural resources in the SDEIS. PolyMetrecommends that the paragraph be replaced with the following: Cultural resourcesunder NEPA can also include natural resources of cultural importance to the Bands.The Co-lead agencies have considered the effects of the Proposed Action on suchresources, including 1854 Treaty resources, under NEPA. The Co-lead agencies haveconcluded that, while the Proposed Action has the potential to have effects on 1854Treaty resources, construction and operation of the Proposed Action is not likely tosignificantly reduce overall availability of 1854 Treaty resources that are typically part ofsubsistence activities in the 1854 Ceded Territory.

Comment 9.


PolyMet addresses the issue of alternatives development, which is discussed in thissection of the Executive Summary, in Attachment A to these comments.

Comment 10.


PolyMet addresses the issue of the Land Exchange Proposed Action, which isdiscussed on these pages, in Attachment B to these comments.

Comment 11.


In Table 1, the Land Use effects of the Proposed Connected Actions are described inthe first bullet point as [n]o effects on land use that would require changes inordinances or comprehensive forest plans. This language is confusing, given that theNorthMet Project Proposed Action would involve the construction of an open pit mine.PolyMet proposes changing this language to say: Changes in land use would occur


March 13, 2014

Page 4 of 70

after the Land Exchange Proposed Action and would not require changes in ordinancesor comprehensive forest plans.

Comment 12.


Although the co-lead agencies have concluded that a segment of the Beaver Bay toLake Vermilion Trail is an eligible historic property, the SDEIS alternates betweenreferring to the BBLV Trail and the BBLV Trail Segment. To ensure consistency withthe co-leads eligibility determination, PolyMet recommends that the agenciesconsistently refer to the property as the BBLV Trail Segment.

This comment applies throughout all Cultural Resources sections in the SDEIS.

Comment 13.


PolyMet recommends that the section of the chart dealing with Cultural Resources &Historic Properties be referred to simply as Cultural Resources since that term isinclusive of historic properties.

Comment 14.

Section 1.4.5, pp. 1-17 1-18

The second sentence in section 1.4.5, Financial Assurance, explains that financialassurance instruments covering the estimated costs of reclamation must be submittedto and approved by the MDNR. As discussed elsewhere in the SDEIS, Minnesota non-ferrous mining rules also require that that financial assurance estimates be updatedannually. PolyMet recommends noting that fact here.

Comment 15.

Section 2.3.2.2, p. 2-5

The first sentence in Section 2.3.2.2, Revised Proposed Action and Alternatives,states that the NorthMet Project Proposed Action has changed greatly since therelease of the DEIS. The use of the phrase changed greatly is ambiguous. Themodifications to the proposal studied in the DEIS are described in detail elsewhere inthe SDEIS. PolyMet accordingly recommends revising the first sentence in Section2.3.2.2 to read: As a result of input from the public, Cooperating Agencies, and the Co-lead Agencies via the workgroups, and additional modeling and impact analyses,PolyMets mining proposal has been modified since the release of the DEIS.


March 13, 2014

Page 5 of 70

Comment 16.

Section 2.4.2, p. 2-8

The second bullet point in Section 2.4.2, Adequacy Determination/Records ofDecision, states that the USACE will issue a ROD [f]ollowing a 30-day commentperiod. Under NEPA, the 30-day period following issuance of a Final EIS is not acomment period. Rather, under 40 C.F.R. 1506.10(b), agencies are simplyprohibited from making a decision on the proposed action until 90 days after publicationof a notice of availability for a draft EIS, or 30 days after publication of a notice ofavailability for a final EIS. The Council on Environmental Quality regulations do notrequire agencies to solicit comments on the FEIS during this 30-day waiting period.

Comment 17.

Section 2.5, p. 2-8

The first bullet on this page does not specify which permits would be transferred toPolyMet. The Minnesota Pollution Control Agency has stated that the NPDES permitfor the Tailings Basin would not be transferred. Instead, a new permit would be issued.

Comment 18.

Section 3.1.1.5, p. 3-3

The south seepage management system is not mentioned at all in this section. This is arelatively new engineering feature that was constructed as part of the Consent Decree.It should be listed as part of the existing infrastructure, since it is already in place.

Comment 19.

Section 3.2.1, p. 3-7

The fifth bullet on this page refers to temporary features that will be removed andreclaimed before or at closure, including roads. It is important to note, however, that notall of the roads will be removed or reclaimed, as some are needed for the post-closureperiod.

Comment 20.

Section 3.2.1, p. 3-13, Table 3.2-1 (Column: NorthMet Project ProposedAction, Row: Plant Site)

The fourth bullet on this page refers to a bentonite layer on top of the Tailings Basin torestrict oxygen and water infiltration with pond. PolyMet recommends clarifying thatthere is a bentonite layer on the outer dam slopes during construction and that, during


March 13, 2014

Page 6 of 70

closure, a bentonite layer will be added to the top of the Tailings Basin. As currentlywritten, the reader may incorrectly assume that a bentonite layer will be added atconstruction, below the new tailings.

Comment 21.

Section 3.2.1, p. 3-17, Table 3.2-2

Reclamation of the Category 1 Stockpile is scheduled to begin in Year 14. As currentlywritten, reclamation of the Category 1 Stockpile is included only in Years 16-20. Itshould also be included in Years 11-16.

Comment 22.

Section 3.2.1, p. 3-17, Table 3.2-2

The movement of waste rock from the Category 2/3 stockpile to the pit will becompleted by the end of operations (Year 20). As currently written, the SDEISincorrectly indicates that this activity will occur after year 20.

Comment 23.

Section 3.2.2.1.1, pp. 3-23 3-31, Figures 3.2-5 through 3.2-9

The transmission lines are not shown correctly on these figures. The figures shouldshow a connection between the transmission line south of the Central Pit and the linesouth of the Category 1 stockpile.

Comment 24.Section 3.2.2.1.1, p. 3-31, Figure 3.2-9

The process water piping from the Category 1 Stockpile should connect to the WWTF.The drainage from the Category 1 Stockpile Groundwater Containment System will betreated at the WWTF.

Comment 25.

Section 3.2.2.1.7, p. 3-43, Table 3.2-7

This table is titled Key Characteristics of Overburden and Waste Rock Management.However, it does not include any information about overburden management. TheCategory 2/3 and 4 stockpiles will be used to store saturated overburden; however,there is no indication of this in these sections and the Maximum Volume listed forthese stockpiles only includes the volume of waste rock, not the maximum volume ofthe stockpiles. The peat and unsaturated overburden will be stored in the OverburdenStorage and Laydown Area (OSLA), which is also not included in this table.


March 13, 2014

Page 7 of 70

Recommend either changing the table title to Key Characteristics of Waste RockManagement or update the table to include maximum capacity of the stockpiles foroverburden storage, as listed in the Rock and Overburden Management Plan (v5)Section 6.2 (Adaptive Management) and information about the OSLA.

Comment 26.

Section 3.2.2.1.7, p. 3-43, Table 3.2-7

The Category 1 Stockpile category shows that the maximum footprint of 526 acres isreached in year 6. However, the Category 1 Stockpile will reach the maximum footprintof 526 acres in Year 21, after it is reclaimed for the cover. The stockpile footprint is 508acres at the end of Year 6, when the footprint is built with slopes at an angle of repose.The stockpile is regraded to a 3.5:1 slope prior to placement of the stockpile cover,which makes the final footprint 526 acres in Year 21.

Comment 27.

Section 3.2.2.1.7, p. 3-43, Table 3.2-7

The Phases of Development section for the Category 4 Stockpile category shows wastefrom the Category 4 Stockpile being transferred to the East Pit in Years 11-20.However, the Category 4 Stockpile will be moved completely by Year 11 to allow formining of the Central Pit to start that same year.

Comment 28.

Section 3.2.2.1.7, p. 3-44

The second paragraph on this page states that unsaturated overburden use wouldrequire MDNR approval. This is not accurate. Unsaturated overburden should notrequire approval from the MDNR.

Comment 29.

Section 3.2.2.1.7, p. 3-44

The fourth sentence of the third paragraph on this page should state: Applications forsaturated overburden would include those where water contacting the constructionmaterial would be collected or drained to the mine pits, where it would be placed backbelow the water table or above a membrane liner system. There should be an or inthis sentence.


March 13, 2014

Page 8 of 70

Comment 30.

Section 3.2.2.1.8, p. 3-46, Category 1 Stockpile Water ContainmentSystem and Cover

For clarity, PolyMet suggests editing the second paragraph and the beginning of thethird paragraph in this section as follows:

Figure 3.2-11 shows the containment system that would consist of a cutoff wall (a lowpermeability compacted soil hydraulic barrier extending down to bedrock) combinedwith a drainage collection system surrounding the perimeter of the stockpile near its toe.

The cutoff wall would be constructed by excavating a trench down to bedrock backfillingit with a compacted soil material or by placing a manufactured geosynthetic clay barrierin the trench. Compacted soil The cutoff wall material would have a hydraulicconductivity specification of no more than 1x10-5 centimeters per second (cm/sec).

Comment 31.

Section 3.2.2.1.8, p. 3-47

In the first paragraph, the description of the Category 1 Stockpile groundwatercontainment system does not adequately describe the sumps. There are two sumps:one at the northeast corner and one on the south side, along the center of the stockpile.To more accurately describe the system, PolyMet recommends making the followingchanges: Stockpile drainage collected in the sumps would be conveyed to a low pointnear the northeast corner of the stockpile. From the sumps, there, a non-perforatedpipe would convey the drainage to a collection sump where it would be pumped to theWWTF.

Comment 32.

Section 3.2.2.1.10, p. 3-63, Proposed Action and Alternatives

The last sentence in the paragraph under the heading Reclamation Planning correctlystates that PolyMet will submit an annual Contingency Reclamation Plan pursuant toMinnesota Rules 6132.1300. In the interest of completeness, the paragraph shouldalso note that the rules require PolyMet to provide financial assurance sufficient to carryout that reclamation plan.

Comment 33.

Section 3.2.2.1.10, p. 3-63, Rail Transfer Hopper

The second paragraph inaccurately refers to disposal of material (remaining ore andsediment from ditches and process water ponds) in the West Pit. This material would be


March 13, 2014

Page 9 of 70

disposed in the East Pit, as described in Section 2.1.2 of the Reclamation Plan (v3)(Rail Transfer Hopper).

Comment 34.

Section 3.2.2.1.10, p. 3-64, Mine Pit Reclamation

The fifth sentence of the second paragraph on this page refers to the overburdensloping as height-to-vertical ratio of 2.5:1. Height and vertical mean the same thing(i.e., both refer to the vertical plane). PolyMet suggests changing this to read eitherhorizontal-to-vertical or length-to-height.

Comment 35.

Section 3.2.2.1.10, p. 3-64; Section 3.2.2.3.10, p. 3-123

On page 3-64, the SDEIS states: The WWTF would be upgraded to include ROtreatment to achieve an effluent with a sulfate concentration of less than 10 mg/L.

Similarly, the SDEIS states on page 3-123: The WWTP would be constructed south ofthe Tailings Basin near the coarse-crusher and would include a RO unit designed toachieve a sulfate concentration of 10 mg/L in effluent. The design of the WWTP couldbe adjusted to accommodate varying influent streams and discharge requirements.

It is not clear when reading the two statements copied above that the water treatmentgoal for the effluent sulfate concentration of 10 mg/L is based on meeting the current 10mg/L sulfate standard for waters used for the production of wild rice (Minnesota Rule7050.0224, Class 4A water quality standard). To clarify, and because that standard issubject to adjustment, the statement to achieve an effluent sulfate concentrationthat meets the sulfate standard for waters used for the production of wild riceshould be used instead of to achieve an effluent with a sulfate concentration of lessthan 10 mg/L.

Comment 36.

Section 3.2.2.1.10, p. 3-65, Stockpile Reclamation

The last sentence inaccurately states state the Category 4 Stockpile would becompletely removed by year 12 to allow mining in the Central Pit. The Central Pit miningbegins in Year 11, as stated earlier in the SDEIS (such as Table 3.2-4). Therefore, theCategory 4 Stockpile would be completely removed by year 11.


March 13, 2014

Page 10 of 70

Comment 37.

Section 3.2.2.1.10, p. 3-65

The second paragraph describes reclamation of the Ore Surge Pile as any remainingmaterial would be relocated to the West Pit after operations cease. However, nomaterial will be disposed of in the West Pit. As described in Section 7.2.2 of the Rockand Overburden Management Plan (v5), any material remaining in the Ore Surge Pile atthe end of operations will be transported to the Process Plant for processing ordisposed of in the East Pit.

Comment 38.

Section 3.2.2.1.10, p.3-71, Watershed Restoration

The fifth paragraph on this page, which lists all ponds that would be either filled orconverted to wetlands, should include the Rail Transfer Hopper Pond.

Comment 39.


The fourth paragraph under the heading Water Management states that [b]ased onthe current GoldSim P90 model predictions, treatment activities could be required for aminimum of 200 years at the Mine Site . . . . This statement is inaccurate andinconsistent with the discussion of the GoldSim water quality modeling elsewhere in theSDEIS.

Comment 40.

Section 3.2.2.2.2, p. 3-83, Existing Conditions

This section inaccurately describes both the existing Cliffs Erie railroad and DunkaRoad as being within the Transportation and Utility Corridor (see Figure 3.2-20). CliffsErie railroad actually is not within the Transportation and Utility Corridor, as Figure 3.2-20 accurately shows.

Comment 41.

Section 3.2.2.2.3, p.3-83, New Construction and Pre-productionDevelopment

The bulleted list on this page should include construction of approximately 5,750-footconnecting track between the Cliffs Erie track and the existing PolyMet track that servesthe Coarse Crusher Building at the Process Plant. This new track is accurately shown


March 13, 2014

Page 11 of 70

on Figure 3.2-20 as a new construction Railroad Connection, but it is not described inthis sections text.

Comment 42.

Section 3.2.2.3.4, p. 3-102, Beneficiation Process Water

The SDEIS states: Throughout operations, the average annual makeup water drawnfrom Colby Lake would vary between 20 and 810 gallons per minute (gpm), with anaverage annual demand of 275 gpm. These numbers are inaccurate. The sentenceshould be revised to show a variation between 120 and 860 gallons per minute (gpm),with an average annual demand of 320 gpm. This section should also acknowledge thatadditional Colby Lake water would be needed for stream augmentation.

Comment 43.

Section 3.2.2.3.10, p. 3-117, Engineered Water Controls

In the second full paragraph on this page, PolyMet recommends providing additionaldetails on the probable maximum precipitation (PMP) to make it clear that the likelihoodof the emergency overflow channel being used is extremely low. PolyMet suggestsediting the text to read:

Pond elevation would be controlled by pumping any excess FTB pond water to theWWTP. An emergency overflow channel would be constructed as a backup means ofcontrolling pond elevation, but discharge from the emergency overflow is not expected.The emergency overflow is provided for protection of the dams in the rare event thatfreeboard within the FTB is not sufficient to contain all stormwater. Such instances havethe potential to occur in the event of a probable maximum precipitation (PMP) rainfallevent or some fraction thereof. PMP rainfall events are rare and such an event has alow likelihood of being experienced during the life of the basin. The PMP does not havean assigned return period, but it is usually assumed by hydrologists to be on the orderof 100 million to 10 billion years. Based on extrapolation of 72-hour rainfall depth datafrom US Weather Bureau-Office of Hydrology Technical Paper TP 49, and the assumedreturn period of the PMP of 100 million years, a 1/3 PMP event could occur roughlyonce in 1,000 years and a 2/3 PMP could occur once in 500,000 years. On this basis,even though there is a low likelihood of overflow, it is standard practice in dam design toaccommodate even low probability overflows in a manner that protects the integrity ofthe dams. Given the low likelihood that there would ever be flow in the emergencyoverflow channel, it is not considered in the impact analysis.


March 13, 2014

Page 12 of 70

Comment 44.


The third paragraph in Section 3.2.2.3.12, Reclamation and Long-term ClosureManagement, contains a list of reclamation objectives and post-reclamationactivities. These terms are not used consistently with the applicable Minnesota Rules.Under the non-ferrous rules, there are two distinct periods during reclamation: closureand post-closure. Closure is a process that begins when mining ceases, and endswhen the reclamation standards identified in the reclamation plan have been achieved.Thus, while it may be reasonable to describe reclamation objectives for the NorthMetProject Proposed Action, it would be more accurate to indicate that these objectives willbe achieved during the closure process. Post-closure maintenance activities aredefined in the applicable rules as activities necessary to sustain reclamation. Post-closure maintenance activities begin when the closure process is complete, and endwhen active reclamation (e.g., water treatment plants) is no longer necessary to sustainreclamation standards. Thus, the activities described in this paragraph as post-reclamation are more accurately described as post-closure maintenance activities.

The same comment applies to text on page 3-137.

Comment 45.

Section 3.2.2.4, p. 3-136, Proposed Action and Alternatives

The first sentence of the third paragraph in Section 3.2.2.4, Financial Assurance,states that the engineering design and planning needed to calculate financial assuranceis typically made available during the permitting process and was not available at thetime that this SDEIS was prepared. While this statement is generally accurate, itleaves a misleading impression that something is missing from the SDEIS. Theparagraph should specify that NEPA and MEPA regulations do not require a discussionof financial assurance, and that PolyMet has voluntarily provided as much informationas possible at the present time.

Comment 46.


The first sentence in the second full, non-bulleted paragraph on this page indicates thata final Reclamation Plan and Contingency Reclamation Cost Estimate will be based onstudies finalized through permitting (pursuant to the EIS process). This reference topermitting pursuant to the EIS process is confusing and should be clarified. PolyMet isnot certain what the SDEIS is trying to convey about the relationship between thepermitting and EIS processes, but it should be noted that those are separate processes


March 13, 2014

Page 13 of 70

and that information gathered during the EIS process will be used when agencies makepermitting decisions.

Comment 47.

Section 3.2.3, p. 3-139, Alternatives

PolyMet addresses the issue of alternatives development, which is discussed in thissection, in Attachment A to these comments.

Comment 48.

Section 3.2.3.3, p. 3-147, Development of the Northmet Project ProposedAction

Table 3.2-16 on page 3-147 provides a comparison of DEIS and SDEIS proposedactions. The table cell corresponding to the first row/first column of the table shouldstate that Category 1 and 2 waste rock would be stored in a permanent lined/ soil-covered stockpile (Category 1/2 Stockpile) north of the west pit (years 1-11). This editmakes clear that the SDEIS proposed action (described in the second column of thetable as including a geomembrane cover system) will include a significantly improvedcover system relative to the cover described in the DEIS.

The third column of Table 3.2-16 should also acknowledge the other improvedoutcomes related to the addition of a geomembrane cover system to the Category 1Stockpile. For example, the following additional bullet could be added to column three:Substantial reduction of stockpile seepage volume that will need to be collected andtreated at the WWTF and significant improvement in West Pit water quality in closure.

Comment 49.

General comment on all Cultural Resources Sections in Chapters 4, 5and 6

The SDEIS often references consultation with the Bands and SHPO, but fails to includePolyMet in these references. When discussing consultation under Section 106 of theNHPA, PolyMet, as the project proponent, should be identified as a consulting party andshould be included in the explanation of the Section 106 process. Examples of wherePolyMet should be noted/included as a consulting party include: the third to lastsentence on page 4-259 (Section 4.2.8.3); the last full sentence on page 4-262 (Section4.2.9.2.1); the second to last sentence in Section 4.2.9.2.2 on page 4-263; the secondto last sentence in the second to last paragraph on page 4-264; the second to lastparagraph on page 4-302; the last full paragraph on page 4-303; the third paragraph onpage 4-555; the second and third paragraphs on page 5-479; the first full paragraph onpage 5-482; the second to last full paragraph on page 5-483; the last paragraph onpage 5-673; and the first paragraph on page 6-89.


March 13, 2014

Page 14 of 70

Comment 50.

Section 4.2.2.1.2, p. 4-29, Table 4.2.2-2

This table lists the mercury TMDL target date for Sabin Lake, Esquagama Lake, andColby Lake as 2015. The target date for those water bodies is 2025. (source: MPCA2013. Minnesotas Final 2012 TMDL List (Section 303(d) Impaired Waters List. Listapproved by USEPA, July 25, 2013).

Comment 51.

Section 4.2.2.1.4, pp. 4-37 and 4-41

The monitored mercury concentration at PM-13 (Embarrass River) is inaccurately statedas 4.0 ng/L. In fact, PolyMets evaluation of the Plant Site at PM-13 used a backgroundconcentration of 3.1 ng/L.

The same comment applies to Table 4.2.2-4, and the cumulative impactdiscussion at p. 6-33.

Comment 52.

Section 4.2.2.1.4, p. 4-37

The first two paragraphs of this section characterize the Tailings Basin mercury samplesas consistent with baseline levels. This is not consistent with the later conclusion thatthe Tailings Basin acts as a sink for mercury. Data from locations in and near theexisting LTVSMC Tailings Basin is actually lower than concentrations observed in thePartridge River and Embarrass River.

This same comment applies to the second paragraph under Direct release ofmercury to the Embarrass river watershed from the tailings basin in Section5.2.2.3.3 on page 5-205.

Comment 53.

Section 4.2.2.2.1, p. 4-43

In the first sentence of the second paragraph, the order of Duluth Complex andPartridge River intrusion should be switched. The Partridge River intrusion is part of theDuluth Complex.


March 13, 2014

Page 15 of 70

Comment 54.

Section 4.2.2.2.1, p. 4-43

In the second sentence of the second paragraph, the use of "Mesabi Iron Range" ismisleading, as it could give the impression that the Duluth Complex is in direct contactwith the Biwabik Iron Formation, which is not the case. PolyMet recommends listing ageologic unit (Virginia Formation) here, rather than the more vague term "Mesabi IronRange." In addition to the cross-section shown on Figure 3.2-10, it would be helpful toinclude a plan view bedrock geology map to illustrate the geometric relationshipsbetween the various bedrock units.

Comment 55.

Section 4.2.2.2.1, p. 4-46, Groundwater Resources

The second sentence of the second full paragraph states: Based on limited MDNR wellrecords within the NorthMet Project area, natural groundwater levels in the glacial tillvary seasonally between 3 and 10 ft bgs. This sentence incorrectly states that the datais limited. Site-specific data on seasonal water level fluctuations is found in the WaterModeling Data Package Volume 1 Mine Site (referenced in the SDEIS as PolyMet2013i). PolyMet 2013i provides information on water level fluctuations observed in 24wells completed in the glacial till at the Mine Site, some with over nine years of waterlevel measurements. Water level fluctuation varies between wells, but the overall rangeobserved in a single well is typically less than 4 ft.

Comment 56.

Section 4.2.2.2.1, p. 4-53

The range of dates cited in the bullets listed under Baseline Groundwater Quality isinconsistent with the groundwater data used for water quality modeling. For example,2012 data from MW-05-02, MW-05-08, and MW-05-09 were used for the modeling.PolyMet recommends removing the dates from these bullets or revising the list so thatrange of dates is consistent with data used to develop Table 4.2.2-6.

The range of dates for groundwater data used for the water quality modeling is asfollows:

Three older wells in the surficial aquifer, sampled from March 2005 through June2012.21 newer wells in the surficial aquifer, installed in November 2011 February2012, sampled following installation through June 2012.Five observation wells in the upper 100 ft of the bedrock, sampled from 2006 to2010 (current SDEIS text is correct for this bullet).


March 13, 2014

Page 16 of 70

Four large-diameter bedrock wells, sampled during aquifer testing in 2005 and2006.

Comment 57.

Section 4.2.2.2.1, p. 4-42, Table 4.2.2-6; Section 4.2.2.3.1, p. 4-94, Table4.2.2-22

It is not clear how the baseline values that are shown in Table 4.2.2-6, and used forcomparison with the site-specific data, were selected. The Northeast MN baseline dataappear to be derived only from the "unconfined buried Quaternary aquifer" category.However, the MPCA study also includes data for buried Quaternary artesian aquifersand Quaternary water table aquifers. Either the range shown in Table 4.2.2-6 shouldreflect data from all Quaternary aquifers in the MPCA report or the Final EIS shouldprovide an explanation as to why only a certain subset of data presented is provided.

Comment 58.

Section 4.2.2.2.2, p. 4-61

The first paragraph describes USGS gage 04015475 as the flow record mostrepresentative of the Project area. However, this section also should acknowledge thepresence of the recently-installed (for Teck American) flow gage at the Dunka Roadcrossing near the southeast corner of the proposed Mine Site (monitoring location PM-3/SW003) and note that, while closer to the Mine Site, the short period of record isinsufficient for use in the SDEIS. This gage also should be shown on Figure 4.2.2-1.

Comment 59.

Section 4.2.2.2.2, p. 4-67

The first paragraph discusses why the use of the lowest expected baseflow isconservative with respect to impacts to surface waters. The paragraph shouldacknowledge that the use of a higher modeled baseflow would lead to higher rechargeinto groundwater, which would translate into faster solute transport times in groundwater(although not necessarily significantly varied peak concentrations). In addition, higherrecharge would increase the expected groundwater inflow into the dewatered mine pits.

Comment 60.

Section 4.2.2.2.2, p. 4-74

In the first paragraph, the text describing existing upper Partridge River water qualityshould mention mercury and aluminum concentrations exceeding water qualitystandards. The text also describes dissolved oxygen at SW002 as the only consistent


March 13, 2014

Page 17 of 70

exceedences. PolyMet reads the term consistent as meaning that all samples at thatlocation exceeded the standard, but that should be made more clear the text. The termconsistent exceedences also appears in section 4.2.6.1.2 (page 4-220), and it shouldbe used in the same way in that section.

Comment 61.

Section 4.2.2.2.2, p. 4-77, Table 4.2.2-14

There are multiple inaccuracies in Table 4.2.2-14 that should be addressed:

1. The average concentrations presented in Table 2.2.2-14 should include 2012data. The 2012 data is included in Large Table 10 of the Water Modeling DataPackage, Volume 1 Mine Site v12.

2. The number of samples at SW004a and SW004b in footnote 5 is incorrectand should also include 2012 samples. The 2012 data omitted from thenumber of samples is included in Large Table 10 of the Water Modeling DataPackage, Volume 1 Mine Site v12. The number of samples at SW004a andSW004b should be 12 samples for each location.

3. The ranges of concentrations presented in Table 4.2.2-14 do not include the2012 data and, therefore, may be inaccurate if maxima or minima occurred in2012.

4. The range provided for mercury concentrations (


March 13, 2014

Page 18 of 70

Comment 63.

Section 4.2.2.3.1, p. 4-95

The third sentence of the fourth paragraph presents a recharge rate of 0.3 in/yr, which isinconsistent with the mean value of 0.61 in/yr used in the GoldSim model. As discussedin Sections 5.2.1.3.1 and 5.2.1.3.2 of this document, average net recharge in theEmbarrass River watershed is estimated at 0.61 inches per year. A recharge rate of 0.3in/yr represents the minimum value used in the GoldSim recharge distribution (PolyMet,2013j; Section 5.2.1.3.2); however, it would be more appropriate to use the averagevalue, rather than the minimum value, for the groundwater flow discussion in the SDEIS.

Comment 64.

Section 4.2.2.3.1, p.4-110, Table 4.2.2-23

Data for the Cell 1E pond should be included in this table. Cell 1E pond data are shownin Large Table 7 of the NorthMet Project Water Modeling Data Package, Volume 2 -Plant Site, Version 9, March 1, 2013.

Comment 65.

Section 4.2.2.3.2, p. 4-121

Regarding the first sentence, PM-13 is not just downstream of the Heikkila Laketributary. It is more accurate to say PM-13 is downstream of the Unnamed Creektributary.

Comment 66.

Section 4.2.2.3.2, p.4-121

In the second sentence, it is unclear what low flows refers to. Based on the low flowspresented in Table 4.2.2-27, PolyMet assumes the co-leads are referring to baseflow.This should be clarified.

Comment 67.

Section 4.2.2.3.2, p. 4-122

In the third paragraph, the text describing the number of samples collected at PM-12.2,PM-12.3, and PM-12.4 should include data from 2012 (2012 data appears to beincluded in subsequent Table 4.2.2-29). The 2012 data is included in Large Table 4 ofthe Water Modeling Data Package, Volume 2 Plant Site v9.


March 13, 2014

Page 19 of 70

Comment 68.

Section 4.2.2.3.2, p. 4-125, Table 4.2.2-30

The row for PM-12 should reflect that data was collected in 2012 at this location.

Comment 69.

Section 4.2.2.3.2, p. 4-129, Table 4.2.2-34

Data for PM-11 should not be presented in Table 4.2.2-34, which is titled Summary ofSurface Water Quality Monitoring Data for the Tailings Basin Surface Seeps.Monitoring location PM-11 is located downstream of the Tailings Basin on UnnamedCreek and is not representative of a seep. Data for PM-11 should be included in Table4.2.2-35 (which includes tributary streams) instead.

Comment 70.

Section 4.2.3.2.2, p. 4-166, Hydrology, Wetland Vegetation, andCommunity Types

In the second to last sentence of the first full paragraph, it should be clarified thatseepage and dead spruce trees are not a cause-and-effect relationship. There aremany beaver dams in the area that likely play a role in the presence of dead sprucetrees.

Comment 71.

Section 4.2.4.2.1, p. 4-174

The last sentence under National Hierarchical Framework of Ecological Units reads:Inclusion of the One Hundred Mile Swamp would likely complete representation ofprominent ELTs in LTA 212Le11. Polymet suggests clarifying by revising this sentenceis to say: The One Hundred Mile Swamp and the two other sites surveyed provide acomplete representation of the prominent ELTs present within LTA 212Le11.

Comment 72.

Section 4.2.7.2, p. 4-252, Table 4.2.7-1

Footnote 1 indicates it is a State standard, but the listed value is federal standard. TheState 1-hr standard is 0.5 ppmv.


March 13, 2014

Page 20 of 70

Comment 73.

Section 4.2.7.2, p. 4-252, Table 4.2.7-1

Regarding the entry for sulfur dioxide 3-hour, the table could be misunderstood assaying that the state and Federal secondary standard is 0.5. In fact, the state primarystandard is 0.5, and state secondary state standards are as indicated by footnotes. Thisshould be clarified in the Standard Type column and the footnotes.

Comment 74.

Section 4.2.3, p. 4-135, Wetlands

The third sentence of the third paragraph suggests that PolyMet will submit a revisedwetland permit application. In fact, PolyMet has already submitted a revised wetlandpermit application, which appears as PolyMet 2013q. NorthMet Project RevisedWetland Permit Application, Version 1. Issued August 19, 2013 in the references.

Comment 75.

Section 4.2.3.1, p. 4-139, Mine Site and Transportation and UtilityCorridor

The first sentence of this section references three figures for the location of the MineSite, in relation to Iron Lake and the Laurentian Divide. However, none of the figuresshow Iron Lake or the Laurentian Divide. The text should be revised to account for thisor the figures should be edited to include Iron Lake. This issue occurs in other sectionsas well, such as the first sentence of Section 4.3.3.1.

Comment 76.

Section 4.2.3.1.1, p. 4-148, Wetland Delineation and Classification

The third sentence of the first paragraph should cite the USACE memo (USACE, May2013) in addition to the baseline wetland type evaluation.

Comment 77.


The first sentence of the third paragraph reads as though vegetation types are indicativeof pre-settlement conditions. However, this is misleading, as there has been asignificant amount of logging disturbance throughout the mine site.


March 13, 2014

Page 21 of 70

Comment 78.

Section 4.2.4.2.3, p. 4-179, Table 4.2.4-4, Endangered Plant Species

The new Minnesota ETSC list became effective (August 19, 2013). Botrychium pallidum(pale moonwort) is not a state-endangered species anymore. Botrychium rugulosum(St. Louis grapefern) and Eleocharis nitida (neat spikerush) are not state-threatenedanymore. All three plant species are now special concern, which means they are notprotected under Minnesotas Endangered and Threatened Species Statute (MN Statute84.0895). Sparganium glomeratum (clustered bur reed) is not a special concern speciesanymore, and has been removed from the Minnesota ETSC list. The text and Table4.2.4-4 should be revised to reflect the new Minnesota ETSC list.

Changes should be made throughout Section 4.2.4.2.3, including the Species LifeHistories discussion, to make the information current and accurate.

Comment 79.

General comment in Sections 4.2.4, 4.3.4, 5.2.4 and 5.3.4

Scientific and common names are used inconsistently throughout these sections.PolyMet recommends using consistent terms throughout the document for clarity.

Comment 80.

Section 4.2.4.2.1, p. 4-170

On page 4-170, there continues to be an inconsistency between the first paragraphunder Habitat Types and the first sentence of the first paragraph under PlantCommunity Surveys. The first paragraph under Habitat Types states that upland-conifer mixed forest types are among the least represented cover types. This isfurther supported by Table 4.2.4-1, which shows upland conifer-deciduous mixed forestas


March 13, 2014

Page 22 of 70

some species are currently present. The text should clarify where (i.e., the Mesabi IronRange or on the NorthMet Mine Site) these species are present.

Similarly, in Table 4.2.4-2, it is unclear how two of the three species with the highestpercent occurrence are estimated to be uncommon on the site, while three of the fivespecies with the lowest percent occurrence are estimated to be common on the site.This inconsistency should be corrected or explained. The EIS should also explain howestimated abundance at the Mine Site was determined, since the text says that noinventories of non-native invasives were conducted.

Comment 82.

Section 4.2.4.3.2, p. 4-193, Non-native Invasive Plants

The first paragraph text states that no invasive species inventories have beenconducted within the Transportation and Utility Corridor. However, the paragraph laterdiscusses field survey data. This could be confusing. The text should clarify that thefield survey data discussed was not a quantitative survey (i.e., not an inventory), butrather is part of a broader ETSC and qualitative vegetation survey conducted by Barr.

Comment 83.

Section 4.2.4.3.3, p. 4-192, Table 4.2.4-7, ETSC Species

The text on page 4-192 names three ETSC species in Transportation and UtilityCorridor, but Table 4.2.4-7 only lists one of these species. This inconsistency should beresolved.

Comment 84.

General Comment to Sections 4.2.5, 4.3.5, 5.2.5, 5.3.5

PolyMet recommends either substituting the word bat for the term Myotis or adding(bat) after Myotis.

Comment 85.

Section 4.2.5.1.1, p. 4-201, Canada Lynx

The Canada lynx is a Minnesota special concern species effective August 19, 2013.


March 13, 2014

Page 23 of 70

Comment 86.

Section 4.2.5.1.1, p. 4-201, Canada Lynx

In the fifth paragraph, the statement that lynx critical habitat includes most ofnortheastern Minnesota is imprecise. PolyMet recommends adding the clarificationthat the USFWS designated critical habitat does not include most of the Iron Range.

Comment 87.

Section 4.2.5.1.1, p. 4-203, Gray Wolf

The last sentence of the third paragraph references forest and brush habitats butparenthetically cites MIHs 1 to 14. PolyMet believes the citation was intended to beMIHs 1 and 14.

Comment 88.

Section 4.2.5.1.1, p. 4-204, Bald eagle

Regarding the last sentence of the third paragraph, there are no standing dead trees inthe existing LTVSMC Tailings Basin.

Comment 89.

Section 4.2.5.1.3, p. 4-208, RFSS

In the third paragraph, it should be noted that the northern Myotis (Myotisseptentrionalis, Northern long-eared bat) was proposed as a federally listed endangeredspecies by the USFWS on October 2, 2013.

Comment 90.

Section 4.2.5.1.4, p. 4-210

The second paragraph should reference Moose zone 3, not Moose zone 30.

Comment 91.

Section 4.2.5.2.2, p. 4-211

The fourth sentence of the second paragraph incorrectly states that the Tailings Basin isunlikely to be heavily used by wildlife. The Tailings Basin is a local refuge for herds ofdeer, small mammals and wolves.


March 13, 2014

Page 24 of 70

Comment 92.

Section 4.2.6.1.1, p. 4-214, Aquatic Biota

The first sentence in the first paragraph references the Longnose, Wetlegs and Wymancreeks as surface water features in the Upper Partridge River Watershed. However,there is no discussion on these creeks or a reference to a previous discussion in theSDEIS. PolyMet recommends either providing a similar discussion of that provided forMud Lake, Yelp Creek, and Second Creek on page 4-214 or explaining why suchanalysis is not provided.

Comment 93.

Section 4.2.6.1.1, p. 4-219, Aquatic Biota, Watershed Level RiparianConnectivity

The second sentence uses the term watershed while the third sentence uses the termlarger watershed. PolyMet suggests explaining the difference between a "watershed"and a "larger watershed."

Comment 94.

Section 4.2.6.1.3, p. 4-221, Aquatic Biota, Fish Communities

The first sentence of the third paragraph should be revised to add Yelp Creek to the listof streams where no fish or macroinvertebrate community or habitat characteristicscould be documented . . . .

Comment 95.

Section 4.2.6.3.3, p. 4-241, Table 4.2.6-11, Aquatic Biota

The source of data for these stream surveys should be revised as Source: Breneman2005, Barr 2011b, and MPCA 2011c. Barr 2011b is the source of the information forthe PM sites.

Comment 96.

Section 4.2.9.1, p. 4-261

PolyMet recommends that the introductory paragraph state that the NHPA process isproceeding on a parallel path to the NEPA process, and that effects on culturalresources have also been considered and analyzed under NEPA.


March 13, 2014

Page 25 of 70

Comment 97.

Section 4.2.9.1, p. 4-261

The last sentence of the introductory paragraph states: Cooperating agencies have notparticipated in production or endorsement of any components of the EIS or theNorthMet Project. This statement is not entirely accurate, since the tribes haveparticipated in the production of components of the EIS relative to cultural resources aswell as the Major Differences of Opinion. The EIS should describe the tribesparticipation in the development of the EIS.

Comment 98.

Section 4.2.9.2.3, p. 4-269.

The second-to-last paragraph is unclear, both with respect to whether it is discussinggroundwater and/or surface water, and with respect to how that discussion fits into theAPE analysis. Figure 4.2.9-5, which is not referenced in this paragraph, is agroundwater quality APE, but most of the paragraph discusses surface water quality.PolyMet recommends revising this paragraph to explain how groundwater and surfacewater affect the APE.

Comment 99.

Section 4.2.11.1.2, p. 4-349, Visual Resources

The discussion of the NorthMet Projects impacts upon visual resources notes that tribalmembers exercise rights to hunt, fish, and gather on Superior National Forest landsnear the Mine Site. However, it also states that [t]he frequency with which tribalmembers exercise these rights in portions of Superior National Forest with views of theMine Site is not known. In particular because the Bands are cooperating agencies, theyhave had every opportunity to provide evidence of frequency. Accordingly, PolyMetrecommends adjusting this language to state that there is no evidence that tribalmembers regularly exercise their rights in this portion of the forest.

Comment 100.

Section 4.2.14.2.2, p. 4-373, Figure 4.2.14-3

The term Sensitive Fines is used on the Figure, yet neither Geotechnical DataPackage, Vol. 1, Version 4, nor preceding versions use the name Sensitive Fines.April 12, 2013 Geotechnical Data Package, Vol. 1, Version 4 uses the name FineTailings/Slimes. This material type is missing from the Legend on the lower left cornerof Figure 4.2.14-3.


March 13, 2014

Page 26 of 70

Comment 101.

Section 4.2.14.2.2, p. 4-373, Figure 4.2.14-3

Units and labels are missing from axes (e.g., elevation in feet amsl and distance in feet)and the dashed lines in the figures are not in the legend (layers of material).

Comment 102.


In the first full sentence, floodplains should be clearly defined, and PolyMetrecommends including a figure showing mapped floodplains with wetlands.

Comment 103.

Section 4.3.3.2.1, p. 4-447, Table 4.3.3-4

The table combines coniferous bogs and coniferous swamps. PolyMet recommendsseparating these two wetland types here, in the same way that they are separated fordiscussions of the federal lands.

This is also an issue in Tables 4.3.3-6, 4.3.3-8, 4.3.3-10, 4.3.3-12.

Comment 104.

Section 4.3.3.2.2, p.4-450, Table 4.3.3-6

The table contains inaccurate acreage for open bog and shallow marsh. Open bogshould be 2.1 acres, and shallow marsh should be 84.1 acres. In addition, the thirdsentence under Table 4.3.3-6 should also be edited from: Large bogs dominate muchof the east-central portion of Tract 1 to the suggested Shrub swamps dominate muchof the east-central portion of Tract 1. The current sentence is inaccurate because thereare only 2 small bogs (2.1 acres total) on the Hay Lake parcel.

Comment 105.

Section 4.3.4.1.1, p. 4-469, Invasive non-native plants

The first sentence states that non-native invasive species on the federal lands are thesame as the Mine Site because they occupy the same area. This is not accurate. TheMine Site is smaller than the federal lands.


March 13, 2014

Page 27 of 70

Comment 106.

Section 4.3.4.1.1, p. 470, Table 4.3.4-5

In footnote 2, PolyMet suggests deleting the phrase additional populations may bepresent in more marginal, secondary habitat that was not surveyed, or in wetter areas.There is no evidence (no survey) of additional populations in marginal, secondaryhabitat, and the SDEIS should make that clear.

Comment 107.

Section 4.3.4.2.4, p. 4-477, Regional Forester Sensitive Species

The second paragraph appears to suggest that there is a correlation between theacreage of a given MIH cover type and the likelihood that an RFSS species that prefersthat cover type will actually be present. This is not entirely accurate. The paragraphfails to take into account other qualitative factors that influence the likelihood of anRFSS species being present. PolyMet recommends revising the paragraph to state thatthe presence of RFSS species would be further influenced by the quality of the habitatavailable, not just the quantity.

Comment 108.

Sections 4.3.5.2.1 and 4.3.5.2.5

In both of these sections, there is a contradiction between text under federal and state-listed species and the text under RFSS. The text under federal and state-listedspecies says that northern myotis and eastern pipistrelle are potentially present onTracts 1 and 5. The text under RFSS states that only northern myotis is potentiallypresent. This inconsistency should be resolved.

Comment 109.

Section 4.3.5.2.1, Other wildlife species

This section discusses species of tribal concern. This is not a legal category. PolyMetrecommends deleting this phrase.

Comment 110.

Section 4.3.6, p. 4-521, Aquatic Species

The first sentence in the second paragraph should be revised to read Some of tThenon-federal lands. . Not all of the non-federal lands have streams, creeks, rivers, orlakes on them.


March 13, 2014

Page 28 of 70

Comment 111.

General Comment on all Land Exchange sections

The Land Exchange analysis must review FEMA floodplains. Therefore, the LandExchange sections should define whether the floodplains are FEMA or non-FEMA. Forexample, the first sentence of the second paragraph in Section 4.3.6.2.1, p. 4-522,should be revised to read approximately 376 acres of non-FEMA floodplain. Thischange should be reflected throughout the Land Exchange sections.

Comment 112.

Section 4.3.6.2.3, pp. 4-531 4-541, Aquatic Species

This paragraph incorrectly compares Coyote Creek with Stony River. These are notcomparable systems. The Stony River is a higher order, more diverse aquatic systemthan the first order, headwaters Coyote Creek. It cannot be assumed that theconclusions drawn from the studies for Stony River are applicable to Coyote Creek.

Comment 113.

Section 4.3.6.2.5, p. 4-541, Aquatic Species, Surface Water Features

The second paragraph is one sentence and cites MIH 14. PolyMet recommends thatthis paragraph first provide some description of the MIH 14 before making the statementit currently contains.

Comment 114.

Section 5.2.2, p. 5-5, Water Resources

The first sentence of the second full paragraph states that the groundwatercontainment system would capture at least 90 percent of seepage from the TailingsBasin. This is incorrect. The system will capture 100% of surface seepage andupwelled water, and at least 90% of seepage that remains as groundwater flow.Overall, 99% of seepage from both surface and groundwater will be captured. Thesentence, as written, implies that the system will be less effective than it will be.

Similarly, PolyMet suggests revising the first sentence in the second full paragraph onpage 5-6 to read: PolyMet proposes a containment system that would capture about99 percent of seepage from the Tailings Basin...


March 13, 2014

Page 29 of 70

Comment 115.

Section 5.2.2, p. 5-7

The 4th paragraph states: With the proposed design modifications and engineeringcontrols, the water quality model predicts that the NorthMet Project Proposed Actionwould not cause or increase the magnitude of an exceedance of the groundwater andsurface water quality evaluation criteria at the P90 level for any of 28 solutes at 29groundwater or surface water evaluation locations within the Partridge River andEmbarrass River watersheds

PolyMet proposes the following language: With the proposed design modifications andengineering controls, the water quality model predicts that the NorthMet ProjectProposed Action would not cause or increase the magnitude of an exceedance of thegroundwater and surface water quality evaluation criteria at the P90 level for any of the27 solutes and mercury (further addressed below) at 29 groundwater or surface waterevaluation locations within the Partridge River and Embarrass River watersheds

Comment 116.

Section 5.2.2.1.2, p. 5-19

The 3rd paragraph states: Within the water quality modeling, estimated concentrationsfor these six metals are compared to hardness-based standards at each modelevaluation location and each model time step to determine compliance with theevaluation criteria.

PolyMet proposes the following language: Within the water quality modeling, modeledconcentrations for these six metals are compared to hardness-based standards at eachmodel evaluation location and each model time step to determine compliance with theevaluation criteria.

Comment 117.

Section 5.2.2.1.1, p. 5-20

The 4th paragraph states Methylmercury is much more of a problem than inorganicmercury, in that it can accumulate to concentrations of concern in the aquatic foodchain, it is more bioavailable than inorganic mercury, and it can bioaccumulate in fish,wildlife, and humans. The term problem suggests a conclusion, when this sentence isactually describing concerns. PolyMet proposes the following language: Methylmercuryis more of a concern than inorganic mercury, in that it can accumulate to concentrationsof concern in the aquatic food chain, it is more bioavailable than inorganic mercury, andit can bioaccumulate in fish, wildlife, and humans.


March 13, 2014

Page 30 of 70

Comment 118.

Section 5.2.2, p. 5-21, Mercury Evaluation Criteria

The first sentence at the top of the page reads: Research suggests that total mercuryconcentrations in streams and methylmercury content in fish are roughly proportionalwithin individual watersheds (USGS 2010), such that, for example, a 5 percent increasein total mercury in water would be expected to result in about a 5 percent increase inmercury content in fish within that watershed.

This sentence should be changed to clearly state that the potential incremental changein fish mercury concentration is an evaluation criterion and that MPCAs Mercury RiskEstimation Method (MMREM) was used to assess the potential changes in fish mercuryconcentrations in nearby lakes. The MMREM is a method that relies on empirical fishcontamination data, combined with the principle of proportionality between mercury infish and atmospheric deposition (MPCA 2006, MMREM guidance document).

In addition, the following is noted with regard to the first sentence at the top of thereferenced page in the SDEIS, and to the principle of proportionality.

In the references section to the SDEIS, the USGS 2010 reference cited above links tothe following web page: Some Ecosystems Will Respond to Reductions in MercuryEmissions. USGS July 29, 2010.1 The first sentence on this webpage states: Aninternational team of scientists investigating mercury cycling in an experimentalwatershed in Ontario, Canada, conclusively demonstrated at the ecosystem scale thatchanges in mercury loadings are expected to result in proportional or near proportionalchanges in mercury bioaccumulation in fish. PolyMet believes this conclusion ofproportionality is not applicable to this project for at least three reasons.

First, the cited website summarizes the results from a study referred to as the MercuryExperiment to Assess Atmospheric Loading in Canada and the United States(METAALICUS) study, which was conducted on a headwater lake, not in a stream. TheMETAALICUS study itself cites that runoff dominated lakes (flow through systems)would not respond the same as a precipitation-dominated headwater lakes (Harris et al.,2007). Because a stream can also be thought of as a flow through system, it will notrespond in the same way to increases or decrease in atmospheric deposition as aprecipitation-dominated headwater lake. In other words, for a run-off dominated lake(flow-through system), the contribution of ambient (pre-existing) mercury from thewatershed to the lake is much greater than the contribution of new mercury to the watersurface. The same would be true of a stream wherein the new mercury fromatmospheric deposition would be minor compared to the contribution of ambientmercury. In addition, Minnesotas Statewide Mercury TMDL (MPCA 2007, Section 4.1)states that The primary source of mercury to the states water bodies is atmosphericdeposition, which is approximately uniform across the state. Mercury concentrations in

1 Available at http://toxics.usgs.gov/highlights/mercury_response.html.


March 13, 2014

Page 31 of 70

fish, however, vary widely on both large and small scales. . Nutrient loadings,hydrology, presence/absence of wetlands and other factors contribute to different fishmercury concentrations in lakes that are relatively close to each other. Therefore, usingthe concept of proportionality is expected to result in an overestimate of the potentialincremental change in fish mercury concentrations due to an individual projectsmercury air emissions as the concept of proportionality does not seem to be supportedfor individual streams or lakes based on the available data.

Second, steady state was not reached during the 3 year METAALICUS study.Ghorpade (2010 thesis) identifies that 8 years after the study started, steady state wasnot reached and the researchers are not able to predict when steady state might bereached. Therefore, the assumption of proportionality based on the METAALICUS studyis uncertain.

Third, there are several USGS reports that indicate a relationship between filteredmethyl mercury concentration in stream water and fish mercuryconcentration. However, likely because of the watershed specific factors affectingmethylation of mercury, there is not a USGS report, 2010 or otherwise, that identifies astatistically significant relationship between total mercury in surface water and fishmercury concentrations.

Comment 119.

Section 5.2.2.2.1, p. 5-23, Figure 5.2.2-6

Modeling results for location UC-1 are not presented in the SDEIS. Therefore, thislocation should not be shown in Figure 5.2.2-6 as a model evaluation location.

Comment 120.

Section 5.2.2.2.1, p. 5-26

The 3rd and 4th sentences of the first paragraph should be clarified to reflect that thePlant Site MODFLOW model was not calibrated to baseflow in the Embarrass River, norwas the model used to estimate baseflow.

Comment 121.

Section 5.2.2.2.1, p. 5-26

Regarding the last sentence on the page, the regional MODFLOW model calibrationwas not updated to the revised baseflow estimates from XP-SWMM. The Mine SiteWater Modeling Data Package Attachment C provides: The regional model calibrationwas not updated because the original calibration did not incorporate a baseflowestimate and previous sensitivity analysis indicated that the local-scale model resultswere not sensitive to the lateral boundary conditions that were defined by the regional


March 13, 2014

Page 32 of 70

model (Barr, 2007). Therefore, the perimeter boundary conditions for the local-scalemodel remained unchanged.

Comment 122.

Section 5.2.2.2.1, p. 5-41, Table 5.2.2-9

The footnote on the Specific yield column of the table only applies to the surficialdeposits, not the entire column in the data table.

Comment 123.

Section 5.2.2.2.3, p. 5-47

The 1st paragraph states: GoldSim was programmed with a suite of complexalgorithms to estimate the release of contaminants from mine facilities (i.e., sources)and their transport to groundwater and surface water evaluation locations. PolyMetsuggests the following language: GoldSim was programmed with a suite of algorithmsto estimate the release of contaminants from mine facilities (i.e., sources) and theirtransport to groundwater and surface water evaluation locations.

Comment 124.

Section 5.2.2.2.3, p. 5-51

The 1st paragraph states: The onset of acidic pore water is also problematic, as theseconditions cause the rate of sulfide oxidation to increase and the concentration ofmetals to increase as precipitates dissolve. PolyMet suggests the following revision:The onset of acidic pore water is also of concern, as these conditions cause the rate ofsulfide oxidation to increase and the concentration of metals to increase as precipitatesdissolve.

Comment 125.

Section 5.2.2.2.3, p. 5-52, Water Quality Modeling (GoldSim), NorthMetWaste Rock Geochemistry

The bulleted list near the middle of the page provides slightly incorrect sulfide sulfurranges for the waste rock classification criteria, as well as an incorrect reference for thisinformation. The sulfide sulfur classification criteria for the categories of waste rockshould be revised as follows:

Category 1 sulfur content less than or equal to 0.12%.Category 2 sulfur content greater than 0.12% and less than or equal to 0.31%.Category 3 sulfur content greater than 0.31% and less than or equal to 0.60%.


March 13, 2014

Page 33 of 70

Category 4 sulfur content greater than 0.60%.

Categories 2 and 3 are combined to produce Category 2/3 with sulfur content greaterthan 0.12% and less than or equal to 0.60%.

This information can be found in Section 4.4.1 of the Waste Characterization DataPackage v10 (PolyMet 2013)

Comment 126.

Section 5.2.2.2.3, pp. 5-53 5-54, Water Quality Modeling (GoldSim),NorthMet Waste Rock Geochemistry, Constituent Release from WasteRock

The first sentence of the last paragraph on page 5-53 states that the GoldSim modelsimulates constituent release from waste rock based on assumptions that eitherextrapolate from conditions observed under field-scale weathering of similar rock(Category 1 waste rock) or in laboratory tests (Category 2, 3, and 4 waste rock, andore). This should be revised to indicate that constituent release for all categories ofrock is based on data from laboratory tests. Constituent release rates for all categoriesof rock are estimated by applying a scaling factor to lab rates to account for likelydifferences between field and lab conditions. The scaling approach differs betweenCategory 1 and the other categories of rock, but release rates for all categories of rockare based on laboratory data.

The first sentence on page 5-54 states that for Category 1 rock, instead of using labtests, the rate of oxidation and constituent release was estimated from studies ofseepage release measured in Dunka Mine rock. .. PolyMet suggests revising the firstsentence to read instead of using lab tests, the rate of oxidation and constituentrelease in the field was estimated from lab release rates that were scaled using theresults of studies of seepage release measured in Dunka Mine rock .

Comment 127.

Section 5.2.2.3.1, p. 5-80, Plant Site

The second paragraph states: The 80 percent rate is used because seepage from thesouth side of Tailings Basin is likely higher than the flow contribution to Second Creekthat would occur from the Basin footprint for natural ground conditions (i.e., if theTailings Basin were not present). This statement is not correct. The 80% is to limit theproject impact on flow to +/- 20% of existing conditions, as is recommended by MDNRon Page 5-14.


March 13, 2014

Page 34 of 70

Comment 128.


PolyMet suggests revising the third full paragraph as follows: WWTP effluent thatwould be used remaining after flow augmentation to Second Creek would bedischarged to the three Embarrass River tributaries (Unnamed, Trimble, and Mud Lakecreeks), as partial or complete fulfillment of required augmentation to maintaindownstream hydrology and wetland function in Second Creek and the threeEmbarrass River tributaries (Barr 2013a). Pumping from Colby Lake would beused to meet any remaining augmentation requirement.

Comment 129.


The second paragraph states: Tailings seepage bypassing the containment system(approximately 19.4 gpm) would continue . On page 5-8 (Section 5.2.2) and in Table5.2.2-36, the flow bypassing the containment system is said to be about 21 gpm.PolyMet recommends revising for consistency.

Comment 130.

Section 5.2.2.3.2, p. 5-.97, Table 5.2.2-19 (Row: Category 4 Stockpile)

The active source period for the Category 4 Stockpile is incorrect. The stockpile will beremoved during the development of the Central Pit and will be entirely removed by theend of Mine Year 11.

Comment 131.

Section 5.2.2.3.2, p. 5-102

The last full paragraph should acknowledge that the pH in the East Pit backfill will bemonitored and adjusted by the addition of alkaline water from the WWTF as backfillingprogresses in order to maintain circum-neutral conditions in the backfill pore water.

Comment 132.

Section 5.2.2.3.2, p. 5-104, West Pit

The SDEIS states: The quality of this aquifer inflow would reflect the quality of the pitlake water, which would gradually improve over time due to cycling through the WWTF.However, the West Pit water will not be cycled through the WWTF during reclamation.PolyMet suggest revising the text to: The quality of this aquifer inflow would reflect the


March 13, 2014

Page 35 of 70

quality of the pit lake water, which would gradually improve over time due to theeffectiveness of the reclamation activities at the site.

Comment 133.

Section 5.2.2.3.2, p. 5-105, Groundwater Transport and EvaluationLocations

The SDEIS states: Cobalt was generally used to illustrate groundwater transport at theMine Site because it is not attenuated and would enter the surficial flowpaths atconcentrations higher than baseline groundwater. This statement is misleading.PolyMet suggests rewording to the following: Cobalt was generally used to illustrategroundwater transport at the Mine Site because the model did not account forattenuation, and would enter the surficial flowpaths at concentrations higher thanbaseline groundwater.

Comment 134.

Section 5.2.2.3.2, p. 5-121

The first paragraph incorrectly states that flow augmentation must be at least 145 or 180gpm, which is 80% of capture flow rate of the current south-side seepage. Table 5.2.2-40 shows 400 gpm, which is the correct rate for augmentation (see The Water ModelingData Package Volume 2 Plant Site v9).

The same error is made in the last paragraph on Page 5-153 (Section 5.2.2.3.2).

Comment 135.

Section 5.2.2.3.2 p. 5-123, Category 1 Stockpile Seepage

The first paragraph of this section only discusses quantities of seepage during closureand not operations. The paragraph below could be added to discuss these aspectsduring operation:

During operations, the Category 1 Stockpile would be uncovered. Infiltration wouldpercolate to the bottom of the stockpile and be collected by the surroundinggroundwater containment system. As the stockpile footprint is expanded, the totalseepage during operations will increase up to a maximum annual flow of between 290gpm and 440 gpm. Most of this seepage would be collected and sent to the WWTF fortreatment; an estimated peak flow of 20 gpm to 30 gpm would pass below thecontainment system and be drawn by gravity into the dewatered West Pit.


March 13, 2014

Page 36 of 70

Comment 136.

Section 5.2.2.3.2, p. 5-126, Table 5.2.2-28

This table is consistent with what was provided in the AWMP, but the corresponding texton Page 5-125 leaves the inaccurate impression that the effluent targets were what wasmodeled as effluent concentrations. The text should be modified to match the table.

Comment 137.

Section 5.2.2.3.2, p. 5-127, Table 5.2.2-29

The use of the term non-contact stormwater in this table and elsewhere in the text issomewhat confusing, as it seems to imply that this is water being managed by PolyMet.PolyMet recommends using the more appropriate term unimpacted watershed runoff.

Comment 138.

Section 5.2.2.3.2, p. 5-143

The first paragraph on this page should acknowledge that there is a low probability forexceedances caused by the project.

Comment 139.

Section 5.2.2.3.3, p. 5-163, Figure 5.2.2-40

Unnamed Creek should be included in the discharge locations for the WWTP effluent.SD006 is the location for Unnamed Creek, not Second Creek. The table organizationcontradicts language found in the last paragraph of page 5-177, which statesaugmentation flow to Unnamed Creek would be via a single discharge near the currentSD006 discharge.

Comment 140.

Section 5.2.2.3.3, p. 5-165, Groundwater Transport and EvaluationLocations

The text states: The rate at which contaminants would move through the groundwaterwould be the same as the groundwater seepage velocity downgradient of thecontainment system for all but four constituents (arsenic, antimony, copper, and nickel).(See Comment p.5-105). Because no attenuation values are used for the constituents other than arsenic, antimony, copper, and nickel the modeled rate of groundwatertransport will be faster than the actual rate of transport in the ground. PolyMetrecommends noting this fact in the text.


March 13, 2014

Page 37 of 70

Comment 141.

Section 5.2.2.3.3, p. 5-165

The last sentence of the last paragraph states: Transport of other non-attenuatedsolutes should be similar to lead, but the change in concentrations is not always asvisually noticeable as it is for lead. This statement is misleading. Lead is the only soluteof interest where loading to the environment is predicted to increase as a result of theproject, which is why it is the only solute to show a visible concentration front movingthrough groundwater down gradient of the tailings basin. Thus, other solutes do notshow a similar behavior as lead.

Comment 142.

Section 5.2.2.3.3, p. 5-182

The second to last paragraph states: the concentrations of these metals in theWWTP effluent would be significantly higher than the concentrations in the currentTailings Basin seepage This sentence should be revised to use the term modeledconcentrations The modeled effluent concentrations from the WWTP are higher thanthe values reported in pilot testing of the proposed treatment systems for the WWTP,but were selected to be near, and slightly below, the potential effluent limit for themodeled constituents to provide a conservative assessment of potential consequencesrelated to downstream water quality.

PolyMet also recommends making this adjustment in Table 5.2.2-47 on page 5-188.

Comment 143.

Section 5.2.2.3.3, p. 5-189

The second to last paragraph states: the average aluminum concentration in the

Comment 144.

Section 5.2.2.3.3, p. 5-189

The first paragraph following the bulleted list states: This dilution effect is demonstratedby the increase in measured aluminum concentrations from upstream tributary locations(UC-1, TC-1, and MLC-3) to downstream locations (PM-11, PM-19, and MLC-2), where

modeled conditions. The use of the term measured implies reference to actual,observed data, but stating that upstream locations would average less than implies


March 13, 2014

Page 38 of 70

or observed.

Comment 145.

Section 5.2.2.3.3, pp. 5-19 and 5-191

There appears to be inconsistency in the chromium standard that is used in thischapter. The referenced pages state: Among the six constituents with hardness-basedevaluation criteria (cadmium, chromium (III), copper, lead, nickel, and zinc), andTable 5.2.2-4 lists chromium (III), as the evaluation criteria with a hardness basedstandard. However, later in the document, the standard for chromium (VI) is used inTables 5.2.2-30 and 5.2.2-42 for example. Please clarify which standard was used forchromium, and why.

Comment 146.

Section 5.2.2.3.4, p. 5-202, Table 5.2.2-49

The number of pit lakes should be 16, not 21 as reported in this table.

Comment 147.

Section 5.2.2.3.4, p. 5-202

The third paragraph states precipitation, which averages about 9.8 ng/L based onaverage volume-weighted mercury in precipitation as measured at the MarcellExperimental Forest deposition site in Itasca County (NADP 2013). Barrs analysis,consistent with the table on the next page, is based on 13 ng/L deposition based on theFernberg Road site. PolyMet recommends citing the Fernberg Road concentration of13.2 ng/L instead of the Marcell concentration of 9.8 ng/L.

This comment also applies to the SDEISs cumulative impact discussion in thefirst paragraph of p. 6-31 and second paragraph of p. 6-33 (Section 6.2.3.3.4).

Comment 148.

Section 5.2.2.3.4, pp. 5-204 and 5-207

The second full paragraph on page 5-204 states: The NorthMet Project ProposedAction is predicted to result in a net decrease in mercury-loading to the Partridge Riverfrom 24.2 to 23.0 grams per year. The basis for these numbers is not indicated and notconsistent with data provided by Barr 2012b. The loading memo indicated a netdecrease from 12.1 to 10.8 grams per year.


March 13, 2014

Page 39 of 70

Similarly, the first paragraph on page 5-207 states: The NorthMet Project ProposedAction is predicted to result in a net increase in mercury loading to the Embarrass Riverof up to 0.6 grams per year (from 22.3 to 22.9 grams per year), about a 3 percentincrease. The loading memo indicated a net increase from 18.5 to 19.1 grams peryear.

These same comments also apply to pages 6-31 and 6-34 discussing cumulativeimpacts (Section 6.2.3.3.4).

Comment 149.

Section 5.2.2.3.4, p. 5-207

The second bullet, when explaining the predicted increase in mercury loading to theEmbarrass River, states: Tailings Basin containment system, which would collectseepage from the Tailings Basin, with an estimated mercury concentration of 1.1 ng/L,and route it to the WWTP, which would discharge with an assumed mercuryconcentration of 1.3 ng/L, for a net increase of 0.2 ng/L of mercury as a result ofwastewater treatment, which is a conservative assumption. PolyMet suggestsexplaining that the reason this is conservative is because the WWTP would reducemercury concentrations, and any additional mercury removal from installing agreensand filter, are not accounted for.

Comment 150.

Section 5.2.2.3.4, p. 5-210, Mercury Summary

The SDEIS states: Overall, mercury loadings are predicted to increase slightly in theEmbarrass River (3 percent) as a result of the NorthMet Project Proposed Action, butwould be offset by a larger decrease (5 percent) in the Partridge River, resulting in a netdecrease in overall mercury loadings (0.6 grams per year) to the St. Louis River as aresult of the NorthMet Project Proposed Action. The basis for these percentages is notindicated and not consistent with data provided (Barr, 2012b). According to the loadingmemo analysis, the increase at the Embarrass River would be 0.2% and the decreaseat the Partridge would be 0.9%.

This comment also applies to page 6-18 in Section 6.2.3.3.4.

Comment 151.

Section 5.2.2.3.5, p. 5-210, Proposed and Recommended MitigationMeasures

The second bullet under NorthMet Project Proposed Action Design Changes states:The location of the Category 4 Stockpile was shifted such that seepage would becaptured in the Central Pit and East Pit and would minimize effects on surficial


March 13, 2014

Page 40 of 70

groundwater. The terminology and locations used here are confusing. PolyMetsuggests the following instead: The location of the Category 4 Stockpile was shiftedsuch that water contacting the stockpile would be captured in the East Pit and wouldminimize effects on surficial groundwater.

It is important to note that the Central Pit will not exist until after the Category 4Stockpile has been decommissioned and the Category 4 waste rock has been relocatedto the East Pit for subaqueous disposal. The most apparent benefit of relocating theCategory 4 Stockpile as part of the Proposed Action Design Changes is that by locatingthe stockpile over an area that will be subsequently engulfed by the Central Pit, theoverall area of surface disturbance (including vegetation, wetlands, etc) of the NorthMetproject will be reduced.

Comment 152.


The sixth bullet states: Refined Hydrometallurgical Flowsheet A single (rather two)autoclave would be fed with nickel concentrate and produce copper concentrateproduced with beneficiation refinements. The production of hydrometallurgical residuewould be cut approximately in half with this design change. Residual copper would berecovered by cementation (contacting the leach solution with copper concentrate) tofurther upgrade the copper concentrate and to further reduce the production ofhydrometallurgical residue. To be more precise, the last phrase should be changed to:, and to potentially further reduce the production of hydrometallurgical residue.

Comment 153.

Section 5.2.2.3.5, p. 5-211

The first bullet discusses subaqueous disposal of reactive waste rock, but it does notmention subaqueous disposal of some of the Category 1 waste rock. Although Category1 waste rock is considered the least reactive waste rock, it should still be mentionedhere.

Comment 154.

Section 5.2.2.3.5, p. 5-211

The fourth bullet discusses the use of side dump cars to haul ore and states: OreTransport PolyMet proposes to use side-dump rail ore cars that would minimize orespillage (PolyMet 2013c). Side dump rail cars were proposed as part of the DEIS, asdocumented in DEIS Section 3.1.3; therefore, this is not a design change and shouldnot be included in this section.


March 13, 2014

Page 41 of 70

Comment 155.

Section 5.2.2.3.5, p. 5-211

The last bullet discusses the WWTP and states: A WWTP would be added at the PlantSite to treat Tailing Basin seepage through operations. Treatment at the WWTP will notend at the end of operations. The WWTP will actually treat this water through operationsand closure.

Comment 156.

Section 5.2.2.3.5, p. 5-212, Tailings Basin Seepage GroundwaterContainment System

The seventh bullet discusses the tailings basin containment system and refers to it asbeing on the western, northern, and northeastern sides of the existing LTVSMCTailings Basin. The containment system is not located along the northeastern side ofthe tailings basin; it is located on the western and northern sides of the tailings basin, asdescribed appropriately on SDEIS Page 3-116 (under Engineering Water Controls).

Comment 157.


The first bullet, as part of a tabulation of fixed engineering controls, states: Processwater management, including pipes, pumps, and process water ponds that would beused to separate and control stormwater and process waters. This statement does notaccount for the fact that the process water ponds are lined. Accordingly, PolyMetrecommends inserting lined before process water ponds.

Comment 158.

Section 5.2.2.3.6, p. 5-218, Table 5.2.2-53, Stormwater Summary

The flow monitoring for stormwater has footnotes stating that flows would be monitoredcontinuously. There are no pumps associated with this infrastructure, so continuous flowmonitoring is not proposed for stormwater flows. Flows are proposed to be monitored ona monthly basis as specified in the Water Management Plan Mine (v2) Section 5.2.


March 13, 2014

Page 42 of 70

Comment 159.

Section 5.2.2.3.6, p. 5-219, Table 5.2.2-53, Surface Water, Colby Lake andWhitewater Reservoir

This table includes water level monitoring for Whitewater Reservoir. This was notincluded in the Water Management Plan Mine and has never been discussed with theagencies.

Comment 160.

Section 5.2.3.1.2, p. 5-227, Potential Indirect Wetland Effects Resultingfrom Changes in Hydrology Due to Drawdown at the Mine Site

The fourth bulleted item is misleading and should be clarified by changing the text inparentheses to say within Area 1.

Comment 161.

Section 5.2.3.1.2, p. 5-227

The first paragraph states The analog approach was based on similar mine settings(e.g., within the glacial till region). PolyMet proposes the following revision: The analogapproach used observations of groundwater response adjacent to iron range minescharacterized by moderate to high hydraulic conductivity glacial and fluvial depositsoverlying lower hydraulic conductivity bedrock.

Comment 162.

Section 5.2.3.2.2, p. 5-277

The third sentence of the first full paragraph should be clarified by identifying the sourceand rationale behind using 675 square meters of watershed area per meter of track inthe contributing watershed as the method for identifying potentially impacted wetlands.

Comment 163.

Section 5.2.3.3.2 p.3-313, Wetland Mitigation

In the second sentence of the third paragraph, it is an overstatement to suggest thatwetlands represent pre-European settlement conditions, as the area was likely loggedseveral times since settlement.


March 13, 2014

Page 43 of 70

Comment 164.

Section 5.2.3.3.2, p. 5-312

The second bullet should read: In-kind mitigation means the replacement of theimpacted aquatic site with the same wetland plant community type. See USACE, 2009,II.D.3.

Comment 165.

Section 5.2.3.3.2, p. 5-312

The third bullet should read: Out-of-kind mitigation means the replacement of animpacted aquatic site with a different wetland plant community type. See USACE,2009, II.D.3.

Comment 166.

Section 5.2.3.3.2, p. 5-313

In the second paragraph, the rule citation is incorrect as is the interpretation of the rule.The second paragraph should read: The Federal Mitigation Rule also states thatdifficult-to-replace aquatic resources include bogs (33 CFR 332.3(e)(3) and Preamble,page 19633). The majority of the wetlands that would be affected by

final sdeis comments from polymet

Documents