March 13, 2014 Michael Jimenez Minerals NEPA Project Manager Superior National Forest 8901 Grand Avenue Place Duluth, MN 55808 Doug Bruner Project Manager United States Army Corps of Engineers, St. Paul District 190 Fifth St. East St. Paul, MN 55101-1638 Lisa Fey EIS Project Manager Environmental Policy and Review Division of Ecological Services 500 Lafayette Road St. Paul, MN 55155 Mr. Jimenez, Mr. Bruner and Ms. Fey, Enclosed please find the comments of Great Lakes Indian Fish and Wildlife Commission (GLIFWC) staff on the Supplemental Draft Environmental Impact Statement (SDEIS) for the proposed PolyMet project. GLIFWC is an intertribal agency exercising delegated authority from 11 federally recognized Ojibwe (or Chippewa) tribes in Wisconsin, Michigan and Minnesota.1

1 GLIFWC member tribes are: in Wisconsin -- the Bad River Band of the Lake Superior Tribe of Chippewa Indians, Lac du Flambeau Band of Lake Superior Chippewa Indians, Lac Courte Oreilles Band of Lake Superior Chippewa Indians, St. Croix Chippewa Indians of Wisconsin, Sokaogon Chippewa Community of the Mole Lake Band, and Red Cliff Band of Lake Superior Chippewa Indians; in Minnesota -- Fond du Lac Chippewa Tribe, and Mille Lacs Band of Chippewa Indians; and in Michigan -- Bay Mills Indian Community, Keweenaw Bay Indian Community, and Lac Vieux Desert Band of Lake Superior Chippewa Indians.

Mr. Doug Bruner and Mr. Bill Johnson March 13, 2014 Page 2 Those tribes have reserved hunting, fishing and gathering rights in territories ceded in various treaties with the United States. GLIFWC’s mission is to assist its member tribes in the conservation and management of natural resources and to protect habitats and ecosystems that support those resources. As you know, the proposed PolyMet mine is located within the territory ceded in the Treaty of 1854. GLIFWC member tribes have expressed concern about the potential impacts of sulfide mining, whether those impacts occur within the 1854 ceded territory, in the 1842 ceded territory, which includes portions of Lake Superior, or the 1837 ceded territory. The following comments are submitted by GLIFWC staff with the explicit understanding that each GLIFWC member tribe or any other tribe may choose to submit comments from its own perspective. Staff remains, as they have for many years, primarily concerned about the scientific validity of the SDEIS with regards to modeling, water quantity, water quality, wetlands, and the assumptions regarding capture efficiencies and long term viability of the engineered structures. Staff also notes that comments and Major Differences of Opinion (MDO) developed for the Pre-draft Supplemental EIS have not been resolved and remain points of disagreement. Specifically, we are submitting comments on the following topics:

• Baseflow in the Partridge River Page 1 • Discharge from East Berm of Flotation Tailings Basin Page 3 • Revised MODFLOW Modeling of Discharge from East Berm Page 7 • SDEIS MODFLOW Modeling of Discarded Basin Design Page 10 • Perpetual Water Treatment Page 17 • Indirect Wetland Impacts Page 19 • Seepage Capture Efficiency Page 21 • Ability of Goldsim to Accurately Predict Contaminant Concentrations Page 28 • Mercury Page 28 • Wild Rice Standard Page 28 • Alternatives Page 29 • No Action Alternative Page 29 • Cumulative Effects Page 29 • Impacts from Rail Car Spillage Page 30 • Loss of High Biodiversity Significance Value Sites Page 30 • Financial Assurance Page 31

Mr. Doug Bruner and Mr. Bill Johnson March 13, 2014 Page 3 As always, we are willing and available to participate as the lead agencies review and revise the EIS document. Please feel free to contact me or Esteban Chiriboga in GLIFWC’s Madison office – (608) 263-2873 if you have any questions or need further information. Sincerely,

John Coleman

GLIFWC Environmental Section Leader Attachments cc. Tamara Cameron, Chief, Regulatory Branch, Army Corps Nancy Schuldt, Fond du Lac Water Projects Coordinator Ken Westlake, USEPA Region 5 Mike Sedlacek, USEPA Region 5 Neil Kmiecik, GLIFWC Biological Services Director Ann McCammon Soltis, GLIFWC Intergovernmental Affairs Director

Baseflow in the Partridge River

The importance of baseflow in understanding site hydrogeology is hard to overstate.

Unfortunately the quality of flow data collected at the Polymet site is poor and fraught with

uncertainty. Because there has not been a Polymet stream gage at the site and Northshore pit

dewatering has occurred into the Partridge at varying and uncertain times, all flow data from the

site is suspect. Simple upstream, at-site, and downstream flow measurement would have

provided higher quality data but was never collected by the applicant nor required by the state.

There have been several work-arounds to try to overcome the lack of good quality flow

data for the site. The latest has been the addition of 1 cubic foot per second (cfs) of flow to the

Goldsim modeling to account for Northshore pit dewatering. The mine site water modeling data

package very clearly states (SDEIS reference Polymet 2013i, pg 123 & 133) that the 1 cfs added

to Goldsim modeling was to account for constituents added to the Partridge by pit dewatering

from Northshore; It is not relevant to baseflow calculations nor is it relevant to determination of

aquifer conductivity or groundwater travel times.

In determination of baseflow, all GLIFWC's calculations have excluded Northshore

pumping from the calculation. The Dec. 17th MNDNR memo (Attachment A) also picked a

period when pumping for Northshore pit dewatering was not occurring so as to calculate true

baseflow. The 1 cfs added to Goldsim modeling of the Partridge, mentioned in various DNR

documents, is irrelevant to the calculation of baseflow and does not solve the modeling problems

in XP-SWMM, MODFLOW and by extension Goldsim. Some of the implications of incorrect

baseflow are highlighted on page 114 of the water modeling data package (March 2013), in our

memo of 2012-03-02, and in GLIFWC's baseflow summary of 2014-02-13 (Attachments B, C,

and D respectively).

Because the implications of baseflow are substantial when it comes to a basic

understanding of the mine site hydrogeology, all modeling of flow and by extension contaminant

transport must be re-calibrated to the higher baseflow numbers indicated by GLIFWC's analysis

1

of 2013-07-02 (Attachment E) and DNR's 2013-12-17 analysis (Attachment A). Page 114 of the

mine site Water Modeling Data Package makes it clear that re-calibration of the MODFLOW

model generates new conductivity values that are then fed into Goldsim. It states:

"The revised model calibration resulted in different optimized values for the horizontal

hydraulic conductivity of the surficial aquifer and bedrock, which are used to establish

the distribution of values used for the probabilistic groundwater flow path modeling

(Section 5.2.3.1)."

It is also clear that higher hydraulic conductivities for the aquifers result in faster contaminant

transport to points of evaluation.

Although baseflow assumptions have significant effects on Goldsim modeling, the

implication of re-calibrating the MODFLOW model go beyond the conductivities used in the

Goldsim modeling. Higher baseflows imply higher conductivities that imply faster and greater

groundwater flow rates. This affects:

1) The amount of water expected to flow into the mine pit as it is excavated.

2) The amount of drawdown of Partridge River flow that can be expected due to pit dewatering.

3) The amount of wetland dewatering that can be expected due to pit dewatering.

Given the uncertainty in baseflow numbers due to the poor quality flow data, it is

reasonable to re-calibrate the MODFLOW model to a range of values that included the

previously assumed baseflow and the newer, higher baseflow numbers.

2

Discharge From East Berm of Flotation Tailings Basin:

Significance:

The contaminant transport analysis at the Flotation Tailings Basin (FTB) does not include

any accounting for discharge through the east berm of the basin. There are 3 reasons why

discharge through the east berm will be enough to cause environmental concern:

1) the flow distance between the final FTB pond in cell 1E and the exterior of the east berm is

relatively short compared to flow distances from the pond to the north and west berms (SDEIS

Figure 3.2-29).

2) the east berm is underlain with 25-50 feet of conductive surficial material (SDEIS Figure

4.2.2.-12 and Figure 2 below).

3) the basin pond level is 1720 ft, the land elevation east of the basin is 1660 ft (Lidar data:

http://www.mngeo.state.mn.us/chouse/elevation/lidar.html). The elevation difference between

the pond and the adjacent land surface is substantial; 1720 ft - 1660 ft = 60 ft.

Because there has been no prediction of discharge from the east side of the FTB, there

was no flow path established or contaminant transport analyzed in the easterly direction. The

SDEIS is completely devoid of any mention or analysis of flow from the basin toward the east.

Receiving waters for the contaminated discharge would be wetlands adjacent to the basin, Spring

Mine Lake, Spring Mine Creek and wetlands to the north if a proposed stormwater drainage

swale is constructed.

Polymet Modeling of Flow from the Basin:

Polymet modeling with MODFLOW (RS13 Attachment A-6 2007; RS13B Attachment

A-6 2008; Polymet 2013j Attachment A 2011), for the FTB has prevented any discharge of basin

water to the east by erecting a no-flow boundary at the surface of the berm and at the ground

surface. This no-flow boundary is an artificial construct that has no basis in reality. In reality,

flow to the east will be controlled by the relative head pressures and the conductivity of the

materials in the FTB, beneath the FTB and in the berms.

3

Geology Beneath the East Berm:

Examination of the geologic data for the site indicates that the east berm of the FTB sits

on a bedrock valley filled with surficial material that is 25 to 50 feet deep. The bedrock valley

under the east berm is the historical stream channel for Trimble Creek prior to the creation of the

current tailings basins (Figure 1). The thickness of the surficial material under the east berm is

indicated as 25 to 50 feet in the depth to bedrock map of the SDEIS Figure 4.2.2.-12 (Figure 2)

and in the depth to bedrock map MN Geological Survey M-126.

Figure 1. USGS Topo map showing the historic stream channel of Trimble Creek.

4

Figure 2. SDEIS Figure 4.2.2.-12: Depth to bedrock map.

The distribution of bedrock under the FTB has been represented in 2 ways during

Polymet MODFLOW modeling. Technical document RS13 of Nov. 16, 2007 Attachment A-6

Fig. 4-2 showed bedrock in the 2007 MODFLOW model as extending under the eastern quarter

of the tailings basin. In technical document RS13b of Sept. 8, 2008 Attachment A-6 Fig. 4-7h,

bedrock in the 2008 model did not extend under the basin but rather showed the basin to be

underlain with surficial material. The text of RS13b, section 4.6.1 of Attachment A-6 states:

"The location of the bedrock hills that flank the Tailings Basin to the east and south were

updated. The location of the bedrock hills is used in the model to define the extent of the

low hydraulic conductivity zone that represents the bedrock. Because the footprint of the

5

Tailings Basin – Mitigation Design is closer to these hills on the southeast side of the

footprint than was the footprint for the proposed design, it was important to get the

location of these hills as accurate as possible. The location of the bedrock hills was

defined using information from the Minnesota Geological Survey’s map M-164. The

resulting zones of hydraulic conductivity can be seen on Figure 4-7."

The extent of the tailings basin footprint represented in RS13b is the same extent as

currently proposed in the SDEIS. However, evaluation of flow from the basin using

MODFLOW and Goldsim appears to have fallen back to the 2007 representation of the basin

footprint and of the underlying bedrock (see GLIFWC comment re: SDEIS modeling and

mitigation basin design).

Conceptual Model of East Berm:

A conceptual diagram of the east berm is provided below. The head difference between

the top of the basin (~1720 ft), the head pressures expected in the surficial deposits below the

center of the basin (1700 ft; RS13b, 2008), and the head pressure at the toe of the basin (1660 ft)

will push water toward the toe of the east berm. The 25-50 feet of surficial deposits in the

bedrock valley under the east berm will conduct water under the east berm and beyond.

Figure 3. Conceptual diagram of the east berm of the FTB. 6

Revised MODFLOW Modeling of Discharge from East Berm:

In order to investigate the approximate magnitude of discharge that would exit the east

berm of the FTB, we conducted modified MODFLOW modeling of basin flows in year 20 of the

project. To simulate the basin but without the no-flow boundary imposed in previous Polymet

modeling, we used the 2008 Polymet MODFLOW model (RS13B Draft-01), with the sole

modification being the placement of model drain cells at the east berm.

The original 2008 model predicted flows of 3340 gpm from the basins, 570 of which was

predicted to flow to the seepage barrier on the south side of the basins (SD026) but no flow to

the east because of the no-flow boundary instituted in that model (RS13B Draft-01). Our

placement of drain cells in the east berm area of the MODFLOW model enabled water to move

east from the berm, rather than reverse flow to the north, west and south as was dictated by the

no-flow boundary. The use of drain cells at the east berm to allow eastward movement of water

is an identical approach as that implemented by Polymet for the south berm of the tailings basin

where the discharge to SD026 is modeled by drain cells.

Depending on the exact placement of the drain cells, the modified modeling resulted in

an estimate of 588 to 847 gpm of flow through the east berm of the basin. This flow is on a scale

similar to the flow predicted for the south berm discharge at SD026 (570 gpm, RS13B Draft-01;

or 540 gpm, Polymet 2013j). That the predicted discharges at the south berm and at the east

berm are similar is logical because both areas are underlain by bedrock valleys filled with high

conductivity surficial deposits. In the context of the predicted total discharge from the FTB at

year 20 (3340 gpm, RS13B; or 3230 gpm, Polymet 2013j) the 588-847 gpm prediction suggests

that approximately 1/5 of the FTB water would exit through the east berm.

Implication of Faulty Modeling of Discharge to the East:

At least three problems arise from the current situation of SDEIS modeling of the FTB

with a no-flow boundary on the east and inaccurate representation of bedrock:

1) There is no contaminant transport modeling or evaluation of the water leaving the east side of

the basin. Without substantial engineering to remove the water, a lake toward the 1680 foot

contour would form (Figure 4) until water spilled toward Spring Mine Lake. The Flotation

7

Tailings Management Plan (Polymet 2013m, page16) discusses the need for a drainage swale to

release stormwater from the topographically closed area to the east of cell 1E. In the SDEIS or

supporting documents, there is no discussion of tailings pond water exiting the basin into this

topographically closed area. There is no accounting for contaminants moving eastward, and there

is no description of their possible impact on receiving ground or surface waters.

Figure 4. Cell 1E discharge area.

2) There are potential receiving surface waters near to the east berm; wetlands at the toe of the

east berm, Spring Mine Lake & Spring Mine Creek to the east, and wetlands and an unnamed

creek to the north of the proposed drainage swale.

3) The Polymet MODFLOW modeling was designed to prevent any water from leaving the east

side of the basin by establishing no-flow boundaries on that side of the model. Because of the no-

flow boundaries, the model output files (Northmet Model Files DVD, BARR July 2012) show

extremely unrealistic groundwater heads in the aquifer surrounding the east side of the FTB. For

example, the Polymet MODFLOW 2011 model predicts groundwater head to be over 1800 ft in

elevation where the ground elevation is 1660 ft on the east side of the tailings basin. A model

with such distorted groundwater head predictions is unlikely to produce accurate flow

8

information, rendering the flowpaths to the north, west and south and flow quantities used by

Goldsim in the SDEIS unreliable.

Realistic flow modeling of the proposed FTB must be conducted to determine flow

directions, flow quantities and travel rates for environmental impact prediction. Information on

water flow direction and quantity is also needed so that water management plans can be

formulated.

9

SDEIS MODFLOW Modeling Appears to be of Fatally Flawed and Discarded

Tailings Basin Design

Modeling in the SDEIS appears to be of a Flotation Tailings Basin (FTB) design that was

discarded several years ago and does not model the currently proposed basin design. The 2007

FTB design, that is modeled in Attachment A (2011) of Polymet 2013j, was deemed to be

"fatally flawed" by the MNDNR (Mitigation Table, Arkley email of 2008/12/09) and was

replaced by the "mitigation" design developed in 2008.

GLIFWC staff have posed a series of questions to the lead agencies regarding the

modeling for water quantity and flow direction at the FTB. ERM has provided a series of written

responses to those questions. The 2014-03-10 Response 4 from ERM re: the Plant Site

MODFLOW modeling identified Attachment A of the Water Modeling Data package of March

2013 (SDEIS reference Polymet 2013j) as the documentation of the tailings basin flow modeling

for the SDEIS.

Careful examination of the scant information in the above referenced Attachment A

(2011) indicates that the modeling done in 2011 for that attachment was not of the FTB as

currently proposed. The footprint modeled for attachment A is the footprint of an early FTB

proposal from 2007 (Figure 5) that was supplanted by the FTB design developed during the

"Mitigation Options" process of 2008. The 2008 mitigation FTB design (Figure 6) is the current

design footprint assumed in the text of the SDEIS (SDEIS Fig. 3.2-23). In addition to using a

discarded FTB design footprint, the modeling in Attachment A also used a crude representation

of bedrock that was supplanted by a more refined bedrock representation during the modeling of

the 2008 mitigation design (RS13B Draft-01, 2008).

The diagrams and model files supporting Appendix A (2011) further demonstrate that the

modeled footprint is of the 2007 fatally flawed FTB design (see footprints in layer 1 of 2007

(Figure 7) and 2011(Figure 8) models, attached), instead of the mitigation basin design (see

footprint in layer 1 of 2008 model, (Figure 9)). The rejected basin design had a smaller footprint

and did not extend as far to the south and south-east. Unlike the current design, the rejected

design did not cover the ash disposal site in the south-east end of the FTB. It appears that the

10

SDEIS Goldsim (water quality) modeling is based on MODFLOW (water quantity) modeling of

an old FTB design that was deemed fatally flawed and is not modeling the currently proposed

FTB design.

11

Figure 5. 2007 FTB Footprint.

12

Figure 6. 2008 FTB Footprint.

13

Figure 7. Footprints in layer 1 of 2007 MODFLOW model.

14

Figure 8. Footprints in layer 1 of 2011 MODFLOW model.

15

Figure 9. Footprints in layer 1 of 2008 MODFLOW model.

16

Perpetual Water Treatment

The proposed Polymet project would require long term treatment of water at both the

plant and mine sites. This treatment would be needed for centuries but the lead agencies have not

required that the applicant provide an estimate of when treatment would no longer be needed.

Therefore, as articulated in Chapter C, GLIFWC staff maintain that water treatment for the

proposed Polymet mine is perpetual.

GLIFWC staff are gravely concerned that the lead agencies are attempting to minimize

the issue of perpetual/long term treatment by using vague and confusing language in the SDEIS.

In addition, the language the lead agencies have used has changed during the development of the

document even though the model results have not.

The SDEIS states on page 5-7:

“Mechanical water treatment is part of the modeled NorthMet Project Proposed Action

for the duration of the simulations (200 years at the Mine Site, and 500 years at the Plant

Site). The duration of the simulations was determined based on capturing the highest

predicted concentrations of the modeled NorthMet Project Proposed Action. It is

uncertain how long the NorthMet Project Proposed Action would require water

treatment, but it is expected to be long term; actual treatment requirements would be

based on measured, rather than modeled, NorthMet Project water quality performance, as

determined through monitoring requirements.” (Emphasis added)

In response to comments on the PSDEIS (Comment GLIFWC1) the Co-Lead agency

disposition states:

“Modeling predicts that treatment activities will be a minimum 200 years at the

Mine Site and a minimum of 500 years at the Plant Site. While long-term, these time

frames are not necessarily perpetual. The owning company would be held accountable to

maintenance and monitoring required under permit and would not be released until all

conditions are met” (Appendix C SDEIS) (Emphasis added)

17

It is impossible to reconcile these 2 statements. We agree that the duration of simulations

were based on capturing the highest predicted concentrations of the modeled action. However,

those concentrations require water treatment to avoid violating water quality standards.

This treatment is at minimum 200 years at the mine site and 500 years at the plant site. As the

lead agencies indicate, these time estimates are only minimums and there is no information that

points to a time when water treatment would not be needed.

Finally, while the maximum contaminant plume is predicted to occur at the 200 and 500

year mark for the mine and plant sites respectively, this does not mean that contaminants

immediately drop to zero. The reduction would be gradual and perhaps last for another few

centuries. In addition the SDEIS states on page 5-56:

“The attenuation effect resulting from sorption is significant enough that arsenic, copper,

and nickel are not predicted to travel from source areas to any evaluation locations or the

Partridge River within the 200 year model simulation period (Barr 2013f). Analytical

calculations suggest that the travel times for these solutes would be in the order of

thousands of years."

This statement suggests that water treatment activities would be required far beyond the

200 year time frame at the mine site and would be on the order of thousands of years. Therefore,

the only logical conclusion is that water treatment is perpetual at this project.

It is also important to note that, in the response to GLIFWC comments on the PSDEIS,

the lead agencies acknowledge monitoring and maintenance requirements during the same 200

(mine site) and 500 (plant site) year timeframe.

The SDEIS requires substantially more transparency on one of the most fundamental

issues at stake for this project. The fundamental question is: how long will the company be

required to operate and maintain expensive mechanical treatment to meet water quality

standards? This singular issue has significant repercussions for the public interest determinations

and the scale of required financial assurance.

18

Indirect Wetland Impacts

The methods used in the analysis of indirect wetland impacts in the SDEIS are essentially

the same as the 2009 DEIS. GLIFWC staff reiterate the comments we have provided in the past

that the method is overly simplistic, based on a flawed conceptual understanding of hydrology at

the mine site and inadequate for the NEPA process of a large scale sulfide mine.

The SDEIS has underestimated baseflow at the mine site. The entire conceptual model of

perched wetlands with hydrology that is completely decoupled from groundwater was supported

by the use of unrealistically low baseflow numbers. Now that the applicant’s XP-SWMM model

has been discredited and that it is obvious that the movement of groundwater at the mine site is 3

times greater than the SDEIS indicates, the assumption that wetlands will not be impacted by

groundwater drawdown should be abandoned. The higher baseflow numbers support the

independent analysis of indirect wetland impacts provided by the tribal cooperating agencies in

Appendix C.

The lead agencies have also based their analysis on the Bog Memo prepared by the Army

Corps of Engineers (Eggers, Steve (2011) MEMORANDUM SUBJECT: Distinguishing

Between Bogs That Are Entirely Precipitation Driven Versus Those with Some Degree of

Mineral Inputs from Groundwater and/or Surface Water Runoff). This memo uses plant

community information to determine the degree of hydrologic connectivity between a wetland

and groundwater. The conclusions in the memo are appropriate for a system that is not

experiencing depressurization of the aquifer (drawdown). However, when mine induced

drawdown occurs, new downward pressure gradients are created. Whittington and Price

documented that these downward hydrologic gradients can in fact dewater wetlands that are

entirely surface water dependent under normal conditions )Whittington, PN and JS Price, The

effects of water table draw‑down (as a surrogate for climate change) on the hydrology of a fen

peatland, Canada. HYDROLOGICAL PROCESSES, 20(17), 3589-3600. 2006). The bog memo

is not an assessment of the hydrologic conditions of wetlands in a dewatered state but rather an

assessment of surface hydrology under normal conditions. The indirect wetland impact analysis

should be performed using realistic hydrologic assumptions and appropriate mitigation should be

required. 19

Figure 10. Summary of issues related to indirect impacts to wetlands.

20

Seepage Capture Efficiency

As detailed in comments submitted to the lead agencies for the 2009 DEIS and for the

current SDEIS, water quality analyses for the Partridge and Embarrass Rivers are inadequate.

The results, be they deterministic (DEIS) or in the form of probability distributions (SDEIS) are

based on a flawed understanding of hydrology at both mine site and plant site. This flawed

understanding, reflected most prominently in the errors in baseflow calculations, is carried

forward to the MODFLOW hydrologic modeling. At the mine site MODFLOW under-predicts

the amount of water that would flow into the mine pits and thus under-predicts the amount of

water treatment needed for both short and long term closure. At the plant site, the MODFLOW

model is constructed in a way that is not representative of reality and therefore yields results that

are not logical. The lead agencies appear to disregard these problems because there is faith that

the seepage capture and treatment systems will work at over 90% effectiveness for centuries. The

SDEIS claims of long term compliance with applicable water quality standards depend entirely

on this leap of faith. On conference calls scheduled to discuss these issues, the lead agency

consultants have stated that the effectiveness of the capture systems have not been questioned

and the lead agencies have not been able to provide any references that would support their

position. We suggest that there are substantial reasons for skepticism regarding capture

efficiency for the flotation tailings basin, hydrometallurgical tailings basin, and category 1

stockpile seepage capture systems. This skepticism is based on available literature and the

performance of other facilities in the immediate vicinity.

The EPA conducted an analysis of the effectiveness of seepage capture systems (Evaluation of

Subsurface Engineered Barriers at Waster Sites, United States Environmental Protection Agency

(EPA), 1998). This analysis looked at capture systems at 36 facilities and evaluated their

effectiveness based on the performance requirements at each site. It is difficult to extrapolate the

results of this analysis to the Polymet setting because a) the required effectiveness varied from

facility to facility; b) the way in which effectiveness was measured was different (i.e. water

quality improvements downstream versus change in hydrologic head pressure) and c) data

collection varied between facilities. Despite these difficulties, the report indicates that 10% of the

reviewed containment systems failed to meet the desired performance objectives and required

21

corrective action. An additional 19% of the evaluated facilities did not have sufficient data to

conclude whether the containment system was operating successfully or not. Furthermore, there

is no information on the effectiveness of any of these facilities at timeframes remotely

comparable to the needs at Polymet. In the EPA report, long term is considered 30 years whereas

the water capture needs at Polymet are perpetual for the flotation tailings basin, category 1

stockpile and hydrometallurgical tailings basin. Finally, none of the facilities in the study are as

large as the one proposed at Polymet.

At the tailings basin, Polymet has proposed to install a seepage collection system around

the north and west sides of the facility. The scale of this engineering control is extensive. It

would be approximately 5 miles long and would have to be keyed to bedrock that is 25 to 50 feet

below ground surface. The most likely pathway for leakage at this barrier will be in the vicinity

of the key with bedrock (EPA 1998). This feature, and the similar containment system at the

Category 1 waste rock stockpile are assumed to capture 93% of water leaving the facilities for an

indeterminate period of time. As previously stated, there is no scientific justification for this

number. The only examples we are able to identify at this time suggest capture rates that are

lower.

22

Figure 11. Summary of issues surrounding the proposed seepage capture systems.

In the Iron Range, GLIFWC staff are aware of 2 examples that are directly analogous to

the proposed Polymet containment system. These are the seepage collection system at SD026 on

the LTV basin itself, and the seepage collection system at the MINTAC tailings basin.

SD026

NorthMet water management plan version 2 states that the south side seepage capture

facility is already operational. The SDEIS further states that the system is operating effectively

and capturing all seepage out of the south end of the facility. This statement is factually

incorrect. MPCA indicates that the seepage capture system at SD026 it is not working properly

and additional work must be performed if it is to achieve the desired water quality improvements

23

in Second Creek (MPCA Personal Communication). There are two immediate comments

regarding SD026. First the SDEIS text must be corrected to accurately describe the lack of

effectiveness of the seepage capture system and second, a quantitative assessment of the

cumulative water quality effects of this wastewater seepage to Second Creek and the Partridge

River should be performed. In addition, the NorthMet water management plan v2 states that the

seepage capture system would be redesigned if necessary. Given that it is necessary, the redesign

of the system should be included in the EIS document.

MINNTAC

The MINNTAC tailings basin is of similar age and design as the LTV tailings basin that Polymet

proposes to use. Both are large, unlined facilities that are designed to allow water seepage to

surface and groundwater in order to maintain structural stability. Both facilities have been

discharging thousands of gallons per minute of high sulfate wastewater into the environment for

decades. MINNTAC, as part of a schedule of compliance, has begun constructing a seepage

capture system that is intended to bring the facility into compliance with applicable water quality

standards. The capture system is similar to the one proposed by Polymet in that it consists of a

trench to capture seepage and a system that would pump tailings water back into the facility. The

MINNTAC system was originally intended to extend to bedrock but that extension was not

possible in some locations because of the presence of large boulders that made construction

difficult. Because the geology of the surficial deposits is similar at the LTV facility, it is likely

that similar difficulties will be encountered by Polymet that would decrease capture efficiency. It

is important to note that seepage capture of greater than 95% is needed at MINNTAC in order to

achieve compliance with applicable water quality standards (Subsurface Evaluation and Seepage

Evaluation Report, MINNTAC Tailings Basin, Mountain Iron Minnesota, US Steel Corp., 2008).

However, this high capture efficiency was not considered feasible and MINNTAC predicted that

their capture efficiencies would not exceed 60% (Subsurface Evaluation and Seepage Evaluation

Report, MINNTAC Tailings Basin, Mountain Iron Minnesota, US Steel Corp., 2008). Actual

performance of the capture system is below 50%. Ultimately, the main purpose of the system is

to comply with water quality standards. The capture system will not be able to achieve that goal.

24

Because MINNTAC is the only facility that is analogous to the LTV basin, there are serious

doubts about the predicted 90% or greater capture efficiency used in the Polymet SDEIS.

Seepage in bedrock is incorrectly characterized. The lead agencies have maintained that

little to no water flows through the bedrock at the site but have not provided sufficient

justification for this assumption. In fact, the SDEIS assumes that the bedrock is a no flow

boundary and therefore assumes that no water moves through bedrock at all. Mapping of known

faulting in the area indicates that there is a strong possibility for water to move quickly through

faults and fractures (Figure 12). Evidence for fault and fracture flow is also found in the water

quality sampling done at the mine site. Water samples in two deep boreholes at the mine site

found Tritium and un-ionized ammonia. The presence of these constituents indicates a

hydrologic connection with surface water. Tritium indicates water found in the deep boreholes

was surface water post 1950, because it is only after nuclear testing that this constituent entered

surface waters. Un-ionized ammonia is produced by blasting activities at taconite facilities. The

Northshore pits, which are the closest sources for this constituent, are located one mile northeast

of the sample boreholes, and are connected to the Polymet mine site through bedrock fractures.

Review of the Northshore pit discharge monitoring data for SD001, in 2006 and 2008, shows the

average concentration of un-ionized ammonia exceeded the 0.04 mg/l NPDES permit limit. This

indicates that groundwater travel time through bedrock faults and fractures will be orders of

magnitude faster than project modeling for Polymet suggests. There is no reason to expect that

fractures and faults do not occur at the plant site. Therefore, tailings water will escape through

bedrock in quantities and speeds that exceed those described in the SDEIS. Finally, faults and

fractures could exacerbate the problem of water bypassing the seepage containment system at the

top of the bedrock.

Summary for Seepage Capture Comments

The prediction of water quality standard compliance for this proposed project hinges on

the perfect operation of the water capture systems. The reliance on this engineered containment

system that uses overly optimistic capture rates and must function in perpetuity is not

scientifically supported and therefore is not appropriate for the SDEIS.

25

The water quality and quantity impacts at both plant site and mine site should be

remodeled by using a range of capture efficiencies. We suggest 60%, 70%, 80% capture rates be

modeled for the tailings basin and category 1 stockpile. Water quality values for each of these

capture rates should be reported. This will allow the public and decision makes to have a realistic

picture of the risk and uncertainty for this project.

Seepage capture at the flotation tailings basin does not account for seepage out of the east

side of the basin. The seepage capture system should be expanded to account for this expected

discharge. A MODFLOW model was developed to assess the amount of seepage that would flow

out of the basin. As detailed in GLIFWC comments, that model is designed in a way that does

not conform to reality and therefore the results are unreliable.

26

Figure 12. Known Faults and Fractures in the area of the Polymet Project. (EMorey, G.B., and Meints, Joyce,

compilers, 2000, Geologic Map of Minnesota, bedrock geology (3rd edition) : Minnesota Geological Survey State

Map Series S-20.) 27

Ability of Goldsim to Accurately Predict Contaminant Concentrations:

We remain concerned about the inability of Goldsim to accurately predict current and

future contaminant concentrations. This is particularly troubling in the lower Partridge River

(e.g. SW005) and in Colby Lake where Goldsim predictions of current conditions appear to be

inaccurate. In recent conversations with the lead agencies and ERM, there has been agreement

that the modeling in the SDEIS does not accurately capture the environmental conditions at

Colby Lake. Additional modeling of this waterbody is needed to assess impacts of the proposed

project and to evaluate the suitability of Colby Lake water for use in augmenting the flow of

other waterbodies. In addition, the discrepancies between modeled and observed data at SW005

should be addressed in detail.

Mercury

The SDEIS does not adequately address mercury concerns as detailed in Appendix C.

The issue of bioaccumulation of methyl mercury in fish, especially in a sulfate rich environment

remains unaddressed for both project specific impacts and cumulative impacts.

Wild Rice Standard

The concerns over the MPCA’s interpretations and recommendations regarding the wild

rice sulfate standard have not been resolved. The information provided in Appendix C is still

applicable to the SDEIS.

In addition, staff believe that water quality modeling underestimates the amount of

sulfate at points of compliance. Even with this problem, contaminant modeling suggests that the

sulfate standard will be violated in the Partridge River points of compliance approximately 10%

of the time. While this may meet the lead agencies arbitrary evaluation criteria (standard met

90% of the time) it certainly is not enough to warrant the issuance of an NPDES permit. At the

Embarrass River the standard is already exceeded at the point of compliance because of historic

contamination from the tailings basin and the area 5 pits. It is not clear if the capture system

around the tailings basin will function well enough to allow the standard to be met.

28

Alternatives

Staff continue to believe that the underground mine and west pit backfill alternatives

have not been properly explored given the environmental benefits they could bring to the project.

Our comments stand as detailed in Appendix C.

In addition, there are a number of alternatives that the SDEIS fails to explore. These

include paste backfill, immediate operation of the RO treatment facility at the mine site, etc.

Additional details are found in the comments submitted by the Fond du Lac Band.

No Action Alternative

During the review of the PSDEIS GLIFWC staff commented that continuation of existing

conditions was not an appropriate No Action Alternative (Table 8-1, Item 10, Chapter 8). The

lead agencies responded by defending their work in the PSDEIS and disagreeing with our

position. However, in the SDEIS the lead agencies completely eliminated any analysis for the No

Action alternative. SDEIS Section 5.2.2.2.3, page 5-78 of the SDEIS was rewritten to point out

that:

"It is important to note, however, that this modeled Continuation of Existing Conditions

Scenario is not the same as the No Action Alternative, which is described in Section

5.2.2.4."

Unfortunately the SDEIS has no serious analysis of a No Action Alternative. Section

5.2.2.4 is less than 1 page long and gives a very general and hypothetical discussion. It in no

way represents a serious analysis of a No Action Alternative. The SDEIS needs to have

modeling of a No Action Alternative, as we describe in SDEIS Appendix C, Hydrology Section,

topic 3 so that the impacts of the proposed action can be compared to a scenario where the

project does not happen.

Cumulative Effects

The concerns regarding the cumulative effects analysis have not been resolved. The

information provided in Appendix C is still applicable to the SDEIS.

29

Impacts from Rail Car Spillage

The concerns regarding the hydrologic impacts of sulfide ore dust spillage along the rail

corridor have not been resolved. The information provided in Appendix C is still applicable to

the SDEIS.

Loss of High Biodiversity Significance Values Sites

The concerns regarding the loss of high biodiversity sites such as the 100 mile swamp,

Lynx and Moose habitat and remaining wildlife corridors have not been resolved. The

information provided in Appendix C is still applicable to the SDEIS.

30

Financial Assurance

The Supplemental Draft Environmental Impact Statement (SDEIS) NorthMet Mining

Project and Land Exchange failed to adequately address closure and maintenance costs and

length of time for post-closure treatment in the context of financial assurance requirements.

The failure of the Army Corps of Engineers and Forest Service to adequately address these areas

in the SDEIS, and instead propose they be addressed at a later time when the Minnesota

Department of Natural Resources undertakes the review of mining permits, is an ill-conceived

attempt to either abdicate their federal trust responsibility or delegate it to the state of Minnesota.

The Fond du Lac Band of Lake Superior Chippewa Indians is a member of the Great

Lakes Indian Fish and Wildlife Commission. The Fond du Lac Band retains off-reservation

rights to hunt, fish and gather under the 1854 Treaty including lands and waters that are adjacent

to the proposed NorthMet mine site. All federal agencies, including the Army Corps of

Engineers and Forest Service, have a federal trust responsibility to protect the habitats that

sustain harvests by treaty signatory tribes when completing Environmental Impact Statements.

The Army Corps of Engineers (ACOE) and Forest Service failed to adequately address

the mine closure and maintenance costs, length of time for post-closure treatment, and financial

assurance requirements in the SDEIS. The ACOE and Forest Service’s position in the SDEIS is

that these items can addressed at a later time by the Minnesota Department of Natural Resources

in the review of future mining permits. This action is an ill-conceived attempt to abdicate their

federal trust responsibility to protect the habitats that support treaty harvests. Despite their

attempts, the ACOE and Forest Service cannot delegate their federal trust responsibility to

protect habitats that sustain treaty harvests to state of Minnesota when it undertakes the process

of permitting the mine.

The SDEIS fails to adequately address the costs for closure and long-term treatment in the context

of financial assurance requirements.

The superficial estimate of financial assurance provides inadequate detail as to how any

of the cost estimates were developed. The DEIS provided a discussion about the options for

31

financial assurance instruments however any substantial discussion of costs and assumptions on

the metrics were not provided and instead postponed until the permitting phase of this Project.

This approach fundamentally contradicts federal environmental policy and must be revised, with

significant additional study, to appropriately evaluate closure, mitigation, reclamation, and

perpetual treatment cost estimates prior to being published in the final EIS. GLIFWC has

identified specific items that need to be addressed in the Final Environmental Impact Statement

on the following pages.

Executive Summary

The Executive Summary fails to provide: 1) an estimated cost for reclamation, 2) an

estimated cost for post‐closure maintenance and water treatment, 3) any realistic estimate as to

the length of time that post‐closure maintenance and water treatment would be required, or 4)

information as to how financial assurance instruments would be structured to ensure the costs of

post‐closure maintenance and water treatment are paid for an uncertain amount of time and for

which models indicate would be longer than 200 years at the mine site and 500 years at the plant

site.

Within the 54 pages of Executive Summary only a single paragraph addresses the issue of

financial assurance as noted below:

“State law requires that PolyMet provide financial assurance before a Permit to Mine

can be granted. Financial assurance instruments, such as bonds or trust funds managed

by the state, would pay the estimated cost of reclamation, should the mine be required to

close for any reason at any time or the company is not able to complete its obligations

under the Permit to Mine”1.

The SDEIS Executive Summary failed to provide either an estimated cost of reclamation

or an estimated cost for post‐closure maintenance and water treatment. Since these costs form the

1 Supplemental Draft Environmental Impact Statement (SDEIS) Executive Summary NorthMet Mining Project and Land Exchange, page ES-54

32

basis for financial assurance requirements and identify key environmental costs of the project

their absence is problematic and a serious omission.

GLIFWC staff have repeatedly requested that the Co-Lead Agencies address the length of

time that post‐closure maintenance and water treatment would be required2, however edits

prepared by the Co-Lead Agencies for the SDEIS failed to identify a defined time period and

noted only that modelling simulations resulted in “(200 years at the Mine Site and 500 years at

the Plant Site)3” and “it is uncertain how long the NorthMet Project Proposed Action would

require water treatment, but it is expected to be long term”. The Executive Summary also failed

to explain how financial assurance instruments can be established to cover the cost of

reclamation and post‐closure maintenance and water treatment costs if “it is uncertain how long

the NorthMet Project Proposed Action would require water treatment4”. The Executive

summary also failed to communicate water treatment would be longer than 200 years at the Mine

Site and 500 years at the Plant Site.

3.2.2.4.1 Cost Coverage and Estimation

The SDEIS provides a listing of items for which costs must be included in the financial

assurance instrument (i.e. demolition of all structures and remediation of sites [fencing the

perimeters, sloping and seeding the overburden, constructing outlet structures, removing

culverts, etc]) yet fails to provide any estimated costs or the basis for these costs. This section

also notes that Reclamation and post-reclamation costs are required yet fails to provide any

estimated costs or the basis for their estimation (i.e. quantities, unit costs, inflation estimates).

The SDEIS notes, PolyMet would ensure that the financial assurance amount is

established as a function of at least three main variables: 1) extent of surface disturbance and

potential releases from waste storage facilities, 2) reclamation and long-term care standards

(including mechanical water treatment), and 3) reasonable assessment of the costs to execute the

2 Supplemental Draft Environmental Impact Statement (SDEIS) NorthMet Mining Project and Land Exchange, Table NorthMet Mining Project and Land Exchange PSDEIS (ver.2) ‐ Tribal Comments and Co‐Lead Agencies' Dispositions 8/19/2013 3 Supplemental Draft Environmental Impact Statement (SDEIS) Executive Summary NorthMet Mining Project and Land Exchange, page 3-59 4 Supplemental Draft Environmental Impact Statement (SDEIS) Executive Summary NorthMet Mining Project and Land Exchange, page 3-59 33

Contingency Reclamation Plan. The SDEIS provides no discussion as to how these variables are

likely to impact overall costs of the financial assurance instrument and how large the variance of

cost estimates are likely to be.

The SDEIS notes, “In addition to the cost of physical closure and reclamation activities as

shown in Table 3.2-15, annual post-closure monitoring and maintenance is estimated to be in the

range of $3.5m - $6m per year. The cost estimates would be finalized by the MDNR during the

permitting processes. “

Table 3.2-15 Preliminary Cost Estimate for Closure Year of Closure (end of

year)

Annual Post-

closure Monitoring

and Maintenance

Year 1 Year 11 Year 20

Estimated Range $50m - $90m $160m - $200m $120m - $170m $3.5m - $6m

Source: Foth 2013.

The costs provided in Table 3.2-15 provide no basis for their estimation or other assumptions. The

SDIES failed to provide detailed costs for the physical closure and reclamation of the mine site that

will need to be covered by Financial Assurance Instruments – a detailed discussion as to how much

money will be needed from financial assurance instruments and when.

The basis for physical closure and reclamation costs need to be based on the private sector

costs and include realistic profit margins when performing cleanup tasks. Cost to be covered by

Financial Assurance need to include detailed information and cover the following areas: 1) interim

operations and maintenance for agencies when a company declares bankruptcy and leaves the site, 2)

water management and treatment, 3) removal of hazardous wastes and substances, 4) demolition,

removal and disposal of facilities and equipment, 5) earthwork (sloping, backfill, grading), 6) re-

vegetation, 7) long-term operations and maintenance, 8) Monitoring costs, 9) detailed inflation

estimates, 9) provide a cash flow analysis, and 10) detail assumptions in the determination of risk and

uncertainty.

The final EIS needs to include the lifecycle of the pollution control structures built, estimates

for their original construction costs, and projections for replacement costs for timeframes exceeding

34

200 years at the Mine Site and 500 years at the Plant Site. In addition to providing detailed cost

estimation, the final EIS needs to clearly identify and communicate assumptions regarding

inflation rates, rates of return, contingencies, and labor rates. Closure and maintenance costs will

need to be covered years into the future, so a net present value must be included in the final EIS.

3.2.2.4.2 Financial Assurance Instruments

The SDEIS provides a listing of contingencies that may have to be covered by financial

instruments including: 1) physical difficulties in implementing reclamation plans, 2) escalating

standards of closure, reclamation, and long-term monitoring, 3) unanticipated liabilities, 4)

unplanned cessation of mining, 5) failure of the mining company, and 6) failure or limitations on the

ability of third parties to pay reclamation costs. Unfortunately the SDEIS provides no discussion as

to any of the costs of the contingencies that are identified. The SDEIS also fails to discuss how

financial instruments would be structured to meet those contingencies or the assumptions made by

PolyMet to ensure an adequate stream of revenue is available to meet closure and maintenance costs

What fundamental economic assumptions are being made when PolyMet proposes to use

surety bonds, irrevocable letters of credit, cash and cash equivalents, trust funds, insurance

policies, or a combination of these Financial Assurance Instruments? The SDEIS failed to clearly

state how the State of Minnesota will determine the maximum bond requirements, how it

estimated direct reclamation costs, how it determined its estimates for inflation (i.e. periodic

bond recalculation or calculate an Inflation factor using a common index, such as the

Construction Cost Indexes (CCI) from the Engineering News Record), and how it will

determine indirect reclamation costs and how it will calculate the total bond amount. The Final

EIS needs to provide information contained in the Reclamation Bond Summary Sheet that is

attached.

3.2.2.4.3 Cessation of Financial Assurance

The SDEIS notes, PolyMet may cancel financial assurance only upon approval by the

MDNR after it is replaced by an alternative mechanism or after being released (in whole or in

35

part) from financial assurance. The SDEIS fails to discuss any federal oversight of this process

and how the federal government will meet its trust responsibility in protecting habitats that

support off-reservation treaty harvests.

4.2.1.4.2 Legacy Contamination

The SDEIS discusses Cliffs Erie site, identifies 62 Areas of Concern (AOC’s), and

discusses PolyMets role in site remediation. The SDEIS failed to provide any information as to

cost estimates for addressing the legal requirements for mitigating the AOC’s as identified. This

information is needed to ascertain if the proposed project would further contaminant AOC’s and

increase clean-up/remediation costs.

36

37

Date: March 8, 2013

NorthMet Project

Water Modeling Data Package

Volume 1 - Mine Site

Version: 12 Page 114

[ ( )] Equation 5-22

For example, if the aquifer length is 1000 meters, then the desired dispersion length from

Equation 5-22 is 11.8 meters. Then, because the dispersion length is equal to one-half the cell

length, the cell lengths should be approximately 23.6 meters. Given the aquifer length and the

optimal cell length, the aquifer will be represented using 42 cells to obtain the desired degree of

dispersion.

5.2.3.7 Groundwater Inflow to Mine Pits

For the DEIS modeling, a MODFLOW model of the Mine Site was used to calculate

groundwater inflow rates to the pits during operations and the expected head distribution and

groundwater flow directions during reclamation and long-term closure (Reference (32)). The

groundwater flow rates to the pits were used to develop the water balances for the pits, which

directly affect the water quality within the pits. The distribution of heads in closure was used to

establish the groundwater flow paths that were used in the MT3D models to evaluate dissolved

solute transport and potential groundwater impacts associated with the Project (Reference (11)).

For current modeling, a similar approach is used; however, several modifications were made to

the previous MODFLOW model to incorporate new information. A brief discussion of the

changes to the model is included here, with additional details regarding model setup presented in

Attachment C. The DEIS MODFLOW model was calibrated to a baseflow estimate of 1.43 cfs at

monitoring station SW004. Revisions to the XP-SWMM model since the DEIS modeling

(Section 5.2.4.3) resulted in different baseflow estimates for the Partridge River. The

MODFLOW model was re-calibrated using target baseflow values of 0.41, 0.51, and 0.92 cfs at

SW002, SW003, and SW004, respectively. In addition, groundwater elevations measured at

Mine Site monitoring wells MW-1 through MW-18 were included as targets in the updated

calibration. The automated-inverse modeling code PEST (Reference (67) and Reference (68))

was used to complete the model calibration. Details of the model calibration are presented in

Attachment C. The revised model calibration resulted in different optimized values for the

horizontal hydraulic conductivity of the surficial aquifer and bedrock, which are used to establish

the distribution of values used for the probabilistic groundwater flow path modeling

(Section 5.2.3.1).

To calculate groundwater inflow rates to the pits during operations, MODFLOW simulations

were developed using methods similar to those used for the DEIS modeling (Reference (32)).

The footprints and vertical extent of the mine features was modified from the DEIS model to

reflect the current Mine Plan. Details regarding the simulation setup and results are included in

Attachment C. The estimates of groundwater inflow rates to the pits were used for the overall

water balance of the pits in the probabilistic model (Section 5.2.2.6.3).

550 Babcock Dr., Rm. B102Madison, WI 53706608-263-2873 Fax 608-262-2500 1 Baseflow_calibration_v2012-03-02.wpd

GREAT LAKES INDIAN FISH AND WILDLIFE COMMISSIONP. O. Box 9 ! Odanah, WI 54861 ! 715/682-6619 ! FAX 715/682-9294

! MEMBER TRIBES ! MICHIGAN WISCONSIN MINNESOTA

Bay Mills Community Bad River Band Red Cliff Band Fond du Lac Band Keweenaw Bay Community Lac Courte Oreilles Band St. Croix Chippewa Mille Lacs Band Lac Vieux Desert Band Lac du Flambeau Band Sokaogon Chippewa

Via Electronic Mail / Original by Mail March 2, 2012

Memorandum

To: Thomas Hingsberger USACEErik Carlson Minnesota DNR

From: John Coleman, Environmental Section Leader

Re: Polymet model calibration to Partridge River low flows

The hydrologic models for the Polymet mine site have been calibrated to targets thatunder-represent true baseflow. Models should be calibrated to a strong set of observational data.Construction of the site’s basic hydrologic model to unrealistically low baseflows hasramifications for all the flow and contaminant modeling at the site.

Under-representation of Partridge River baseflow.

Review of the winter baseflow measurements and comparison to predictions made byXP-SWMM indicate that XP-SWMM substantially underpredicts baseflow (Barr June 9, 2011,Comparison of MDNR winter flow gauging to Partridge River XP-SWMM model). This hasramifications throughout the parameter sets being used in models characterizing hydrology at thePolymet mine site.

In the above referenced memo, Barr points out that the average measured baseflow atDunka Rd. was 5.0 cfs while the XP-SWMM predicted baseflow is 0.4 cfs. Even when dischargefrom Northshore Mining was taken into account, the average baseflow measured at Dunka is 4.3cfs while XP-SWMM predicts 0.42 cfs.

In its memo, Barr correctly points out that: "At all locations along the main stem of thePartridge River, the XP-SWMM-estimated baseflow is less than the MDNR-measured baseflow.The XP-SWMM model provides a conservative estimate of Partridge River baseflow for thepurposes of modeling water quality impacts (e.g., less dilution of loads from the Mine Site)."What is not acknowledged in the Barr memo is that calibration of hydrologic models to anunderestimate of baseflow produces models that characterize the groundwater hydrologic systemas moving an unrealistically small quantity of water.

550 Babcock Dr., Rm. B102Madison, WI 53706608-263-2873 Fax 608-262-2500 2 Baseflow_calibration_v2012-03-02.wpd

Additional flow measures over the last 9 months on the Partridge River at the DunkaRoad (site SW-003) further support the position that baseflow predicted by XP-SWMM under-represents true baseflow. The least flow measured at the Dunka Road site was 3.8 cfs. Whilethere have so far been only 7 measurements taken at that site, the flow measured and the stagerecorded by the gauge do not appear to support XP-SWMM’s low baseflow predictions for theupper Partridge River.

Mis-calibration of groundwater flow models.

The calibration of the Modflow model to a Partridge River baseflow of 0.76 cfs predictedby XP-SWMM results in a model that moves very little water through the groundwater system. This can result in low predicted rates of inflow to the mine pit and slow movement ofcontaminants from sources (stockpiles or reflooded pits) to points of evaluation. More generally,an incorrect baseflow calibration target results in excessively low estimates of recharge andlikely incorrect estimates of horizontal and vertical conductivity. These hydrologic parametersare interrelated and getting one wrong, as appears to be the case with baseflow, will almostcertainly result in the other parameters being incorrectly estimated. Although there has been littlesensitivity analysis conducted in the Polymet modeling efforts, flow models tend to be sensitiveto these interrelated parameters.

Based on Modflow model calibration to a baseflow of 0.76 cfs and recharge values set at0.3 and 1.5 in/yr (see page 61 of Water Modeling Data Package Vol 1-Mine Site v9DEC2011.pdf and page 11 of RS22, Appendix B), some horizontal and vertical conductivities(K) were calculated by Barr using PEST (see Table 1 of Attachment B of Water Modeling DataPackage Vol 1-Mine Site v9 DEC2011.pdf). These K values are likely to be inaccurate sincethey are calculated with a model that is calibrated to a baseflow that appears to be almost anorder of magnitude too low. It is unlikely that any accurate predictions of water movement,transport of contaminant mass, or contaminant levels can be made when the characterization ofthe hydrologic system is so out-of-kilter.

Unusually low recharge and vertical K:

The low values used for recharge (0.3 and 1.5 in/yr) and the low wetland and till verticalK (0.0000033 ft/day [1.16X10-9 cm/s]) used in the Modflow model are a reflection of a modelconstructed and calibrated to move an unrealistically small amount of water through thehydrologic system. For context, note that engineered clay liners in landfills typically aim for1.0X10-7 cm/s hydraulic conductivity. I was unable to find any reference in the literature towetland soil vertical conductivity as low as is used in the Modflow model. The lower end of thespectrum I found for wetland soil vertical conductivity was 1X10-6 cm/s.

Our long standing concern that the mine site hydrologic models incorporate incorrectassumptions about recharge are supported by Fred Marinelli's comment on line 39 and elsewhereof: "Agency Responses MS and PS WP and Waste Characterization Data package V72-7-12.xls". His comment states that "A net infiltration (recharge) range of 0.3 to 1.5 in/yrrepresents 1.1 to 5.4 percent of mean annual precipitation (MAP). This range for local netinfiltration is unrealistically low for this area of the US." These low recharge values and the low

550 Babcock Dr., Rm. B102Madison, WI 53706608-263-2873 Fax 608-262-2500 3 Baseflow_calibration_v2012-03-02.wpd

vertical K values are related to calibration of the Modflow model to low baseflow. UntilModflow, and by extension the other related models XP-SWIMM and GoldSim, are calibrated todata from the site (e.g. observed baseflow and an adequate number of observed heads) andincorporate reasonable recharge rates, the results from the models are unlikely to accuratelysimulate current or future conditions.

Recalibration of models needed:

The Modflow model, in particular, needs to be calibrated with targets based on observedbaseflow and observed well water heads. Calibration to projections by XP-SWMM, that appearto be incorrect, means that the fundamental characterization of the site hydrology is likely to befaulty. In the document referenced above (Agency Responses ...) Barr Engineering states thatmany hydrologic model parameters were “discussed as part of the IAP process and will not beconsidered further at this time.” While some parameters were discussed in the groundwater IAPprocess, the discussion was almost exclusively concerning water quality parameters, not flowmodel parameters such as recharge, baseflow and Kv and Kh. The focus on water qualityparameters to the near exclusion of hydrologic flow parameters is reflected in the GroundwaterIAP summary memo of June 2011. Groundwater flow modeling underpins contaminanttransport modeling and is interrelated to surface flow models. Without adequate vetting of flowmodel parameters and predictions, it is impossible to have confidence in predictions ofcontaminant movement and water quality.

Now that the hydrologic models have been more fully articulated by Barr and additionaldata are available, the models must be calibrated to observed baseflow and well water levels.This should include the new water level data from the newly installed mine site wells. PEST canthen be used to more reasonably estimate values for recharge and conductivity. The observedbaseflow and the PEST estimated recharge and conductivity values should then be used in theXP-SWMM and GoldSim modeling efforts. Modeling efforts that are based on faulty initialassumptions and not on field observations will not be able to reasonably predict impacts. Thecurrent Polymet modeling effort needs to be well founded on a strong base of observations of thephysical conditions at the site.

Thank you for considering this issue. Please contact me at 608-263-2873 if you havequestions.

cc: Mike Olson, Minnesota DNRFred Marinelli, InterralogicMike Sedlacek, USEPAJames Grimes, USEPAMarty Rye, USFSNancy Schuldt, Fond du Lac Environmental ProgramNeil Kmiecik, GLIFWC Biological Services DirectorAnn McCammon Soltis, GLIFWC Policy Analyst

2014-02-13

Baseflow Issue at PolyMet

Stream or river baseflow is a key variable in modeling because it is an indicator of the fundamental characteristics of the groundwater hydrology of a site. It is useful in helping to define the amount and speed at which ground water moves through the system.

Baseflow is usually calculated by measuring rates of stream flow at stream gauges to define low flow conditions for a site. During low flow periods the water found in a stream or river is often assumed to befrom groundwater. For the PolyMet project, the applicant did not install a stream gauge at the site. Instead they used data collected in the 1980’s from a stream gauge located 17 miles downstream. They then used a model (XP-SWMM) to extrapolate that information upstream to the area where the proposed pits would be located (mine site). The result of that extrapolation was a predicted baseflow rate of 0.5 cubic feet per second (cfs) in the Partridge River at the Dunka Road. As part of the process of XP-SWMM prediction of baseflow, periods were chosen when Northshore Mine was not discharging pit water into the upper partridge. Tribal Cooperating agencies have argued since 2008 that the baseflow rate predicted by XP-SWMM is unreasonably low and implies recharge to the groundwater system from precipitation that is not consistent with published literature.

Since the initial calculation of baseflow with XP-SWMM, which was used in the first DEIS, the MNDNR has conducted some limited measurements of flow in the Partridge River during winter. Winter flow is often used as a indicator of baseflow because during winter, it is too cold for rain and other surface water to enter a stream and thus it is assumed that the flow in the stream is a reflection of groundwater discharging to the stream bed. Those measurements suggested that baseflow was significantly higher than the 0.5 cfs predicted by XP-SWMM. GLIFWC staff have, on multiple occasions, provided calculationsof baseflow using alternative methods. Those analyses suggest that baseflow in the Partridge River at the Dunka Road was in the range of approximately 1.1 to 1.8 cfs.

In 2011 Tech Resources arranged for a stream gauge to be installed in the upper Partridge River which has allowed the MNDNR and GLIFWC to conduct calculations of baseflow using data obtained in the mine site area. The MNDNR calculations, released by MNDNR hydrologists in December of 2013, confirmGLIFWC’s position that baseflow was underestimated by the XP-SWMM model and is in fact closer to 1.5cfs rather than the previously predicted 0.5 cfs.

A confounding variable in the calculation of baseflow is the fact that the Northshore Mine discharges pitdewatering water into the Partridge River. This means that if flow measurements are taken during timeswhere Northshore is discharging their pit water, some of the water measured in the Partridge River maybe mistaken for baseflow. This is why both GLIFWC and MNNDNR's December 2013 calculations were careful to only use Partridge River flow data collected when Northshore was not discharging. It is from these times of no Northshore discharge, that the 1.5 cfs of baseflow was calculated.

Baseflow is also highly related to the rate of recharge. Recharge is the process by which rainwater percolates into the ground and into the groundwater aquifers. Because baseflow has been underestimated, the recharge values used in the modeling are also unrealistically low. In fact, the recharge numbers calculated by the applicant and used in the SDEIS are not supported by published literature or data collected in the region.

On January 28th, 2014 the MNDNR released a statement claiming that Polymet modeling has accountedfor the difference between the 0.5 cfs XP-SWMM prediction and the more recent 1.5 cfs estimate of baseflow by adding 1 cfs to the Goldsim model. This explanation is incorrect because it confuses flow (which may be a mix of water from surface water sources and groundwater sources) with baseflow (which is water from groundwater sources only). The MNDNR statement further confuses water quantity models (XP-SWMM and MODFLOW) with the water quality model (Goldsim). Yes, a 1 cfs was added to the water quality model (Goldsim) to account for Northshore pit dewatering discharges but this does not relate to baseflow rates predicted and used in XP-SWMM and MODFLOW.

The difference between flow and baseflow can be demonstrated by the calculation of flow statistics for the stream gauge on the Partridge. The Q90 for the full data record from the gauge is approximately 2.5cfs. In other words, 90% of the time river flow was greater than 2.5 cfs at the gauge site. This is an indication of low flow in the Partridge and includes flow from all sources including groundwater and Northshore pit dewatering. On the other hand, the Q90 for periods when Northshore was not discharging pit water into the Partridge is approximately 1.5 cfs at the gauge site. This is an indication of flow derived from groundwater discharge to the partridge and is therefore considered an indicator of baseflow.

On a conference call conducted on February 12, 2014 the MNDNR confirmed that the 1 cfs was added toaccount for surface water pumping from Northshore in the Goldsim model (water quality) and not for any other purpose.

Why Is this Important?

Neither the direct winter field observations made by MNDNR (minimum of 3.4 cfs) nor the values calculated by GLIFWC and MNDNR from the stream gauge data (approximately 1.5 cfs), support the baseflow predicted by XP-SWMM at SW003 of 0.5 cfs (Water Modeling Data package Vol.1-Mine Site, ver12, p.130 and PSDEIS Table 5.2.2-12). XP-SWMM's low estimates of baseflow have been used in calibration of the MODFLOW model and thus influence many aspects of the site characterization and impact prediction, including pit inflow, dewatering impacts to the Partridge River and wetlands, water treatment needs, groundwater flow rates, contaminant transport times and concentrations, and contaminant dilution in the Partridge watershed.

A higher baseflow rate (1.5 cfs rather than 0.5 cfs) changes the conceptual understanding of how water passes through the groundwater aquifer. That change in understanding impacts predictions of how a mine would affect the aquifer. The conclusions that appear in the SDEIS of no significant impact to rivers, lakes and wetlands in the mine site are based on the concept that groundwater flows very slowly through the aquifer. The applicant has assumed, based on the 0.5 cfs baseflow, that wetlands and the

Partridge River are mostly isolated from the groundwater system and that little water will flow into the open pit from the groundwater system. Higher baseflows in the Partridge River, as demonstrated by GLIFWC's and MNDNR's analyses, strongly suggest that the wetlands and river are more connected to the groundwater aquifer, that mine pit inflow will be greater; and that groundwater travels through the aquifer at a faster rate.

Baseflow is used to formulate the model (MODFLOW) for calculating the amount of water that would flow into the open pits during mining. Therefore, the applicant has underestimated the amount of waterthey would need to pump out of the pits during mining and the amount of water they would need to treat prior to discharge. It is reasonable to assume that costs of treating this increased quantity of water,both short and long term may have also been underestimated.

Because the new baseflow numbers indicate that water moves through the ground faster than the SDEISassumes, the plume of contaminants from the reclaimed mine pits will likely reach points of evaluation faster and and in greater volume. Some have suggested that more water in the system would lead to more dilution of the PolyMet contaminant plume and thus produce less water quality impact. That is a naive, and possibly incorrect, view of a complex system. Higher baseflow relates to higher conductivity of the aquifer which has many impacts on flow and contaminant predictions. With increased flow through the aquifer, contaminant levels at compliance points could decrease, increase or stay the same. Only remodeling of the proposed project using realistic hydrologic inputs for baseflow and recharge can provide an adequate answer to this question.

Subject: Partridge River baseflow, draft analysis of new data suggest XP-SWMM estimate inaccurateFrom: "john.coleman" <jcoleman@glifwc.org>Date: 7/2/2013 11:56 AMAttachments:Baseflow_calibration_v2012-03-02.pdf (32.2 KB), 2012-06-12_baseflow info re NorthMet EIS Mine

Site Hydrology Teleconference.eml (2.8 KB), 2012-06-18_watershed ratio predicts baseflow of 1.2cfsat SW-004 Re Model Calibration, NorthMet EIS.eml (3.1 KB), 2008-09-28_further comments onRS22 AppenB Draft-03.htm (4.5 KB)

To: thomas hingsberger <thomas.j.hingsberger@usace.army.mil>, Ross Vellacott <Ross.Vellacott@erm.com>,"Shirley Frank (USFS)" <safrank@fs.fed.us>, "Bill Johnson ( [...]

CC: "Sedlacek.Michael@epamail.epa.gov" <Sedlacek.Michael@epamail.epa.gov>,"Grimes.James@epamail.epa.gov" <Grimes.James@epamail.epa.gov>

To: Polymet EIS Co-leads 2013-07-02

From: John Coleman, GLIFWC

Re: Partridge River baseflow, draft analysis of new data suggest XP-SWMM estimate inaccurate

We remain concerned that the basic hydrology of the mine site is mis-characterized as being very non-conductive.The baseflow in the Partridge is a fundamental parameter to which many flow and contaminant transport models arecalibrated. Unfortunate the baseflow at the site used in impact prediction is an estimate make by XP-SWMM. XP-SWMM appears to do a poor job of predicting baseflow at the mine site, possibly because it is based on a data setcollected 17 miles downstream. As we note in our recently submitted PSDEIS comments, the MDNR winter flow measurements in the PSDEIS(Table 4.2.2-9) indicate substantially higher baseflow in the Partridge than predicted by XP-SWMM. This is true evenwhen the flow data is corrected for any possible Northshore (NS) discharge to the Partridge by subtracting thefarthest upstream measurement from measurements taken farther downstream. Even more compelling than the winter MDNR flow measurements is the flow data that has been recorded at theDunka Road gage over the last 2 years. I have again calculated some statistics on the flow measurements taken at thePartridge River & Dunka Road, also known as monitoring site SW003. (http://www.dnr.state.mn.us/waters/csg/site_report.html?mode=get_site_report&site=03155002)Earlier comments on this topic are attached and previous analysis was submitted to the lead agencies by email on2012-06-12, 2012-06-18, and on 2008-09-28 (attached).

The stage and flow values measured by stream gage are available at 15 minute intervals. Based on 66,581 stagerecords collected between May 2011 and April 2013 and the DNR rating curve, I found: Q90 at SW003 = 2.32 cfs (90% of the time flow was greater than 2.32 cfs) Q90 is sometimes used as an indicator ofbaseflow

Using 586 daily average flows from 2011-05-26 to 2012-12-31 calculated by the DNR and accounting for winter iceconditions, I found:Q90 at SW003 = 1.9 cfs

Given that Northshore Peter Mitchel (PM) pit intermittently discharges to the Partridge River, I also analyzed 3months in 2011 (Jul,Aug,Sep) and 3 months in 2012 (Feb,Mar,Apr) when Northshore (NS) discharged zero (0)gallons into the Partridge River. Based on average daily flows calculated by the DNR:In the 3 months of no NS pit discharge in 2011 Q90 at SW003 = 1.8 cfsIn the 3 months of no NS pit discharge in 2012 Q90 at SW003 = 1.1 cfs

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Given that both these 3-month periods are typically low flow times, it seems that a baseflow estimate for site SW003of 1 - 2 cfs would be reasonable.While analysis based on only 6 months of flow data is not ideal, it should be noted that the XP-SWMM model iscalibrated to only 2 months when Northshore did not discharge to the Partridge in 1985 (PSDEIS page 4.2.2-44, 1stparagraph).

Neither the direct field observations (minimum of 3.4 cfs) nor the values calculated from the DNR rating curve,support the baseflow predicted by XP-SWMM at SW003 of 0.51 cfs (Water Modeling Data package Vol.1-MineSite, ver12, p.130 and PSDEIS Table 4.2.2-8). XP-SWMM's low estimates of baseflow are used in calibration of theMODFLOW model and thus influence many aspects of the site characterization and impact prediction, including pitinflow, dewatering impacts to the Partridge River, water treatment needs, groundwater flow rates, contaminanttransport times and concentrations, and contaminant dilution in the Partridge watershed.

Although it is now an unfortunate time in the NEPA process to try to adequately characterize basic site hydrology, ifappears that predictions of effects of the project may be far from accurate. It is not easy to say how themis-characterization of river baseflow would affect compliance predictions because, although more baseflow mightmean more dilution of contaminants, it could also mean transport of greater quantities of pollutants to the river andmore drawdown of the Partridge River. We have repeatedly asked that the data at the Dunka Road gage be formallyanalyzed for baseflow as a check of the accuracy of the XP-SWMM modeling. If that analysis indicates that theXP-SWMM predictions under-represents baseflow, as our draft analysis suggests, that result should be incorporatedinto all project model calibration and prediction.

Thank you in considering this issue when revising the SDEIS.

--John Coleman, Madison Office of the Great Lakes Indian Fish & Wildlife CommissionU.W.-Madison Land Information and Computer Graphics Facility550 Babcock Drive, Room B102Madison, WI 53706608-263-2873 or 265-5639jcoleman@glifwc.org

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