GREAT LAKES INDIAN FISH AND WILDLIFE COMMISSION P. O. Box 9 Odanah, WI / FAX 715/

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1 GREAT LAKES INDIAN FISH AND WILDLIFE COMMISSION P. O. Box 9 Odanah, WI / FAX 715/ 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 December 13, 2015 Michael Jimenez Minerals NEPA Project Manager Superior National Forest 8901 Grand Avenue Place Duluth, MN Doug Bruner Project Manager United States Army Corps of Engineers, St. Paul District 190 Fifth St. East St. Paul, MN Lisa Fay EIS Project Manager Environmental Policy and Review Division of Ecological Services 500 Lafayette Road St. Paul, MN Comments on NorthMet FEIS and Section 404 permitting Re: Hypothetical groundwater mound between PolyMet and Peter-Mitchel pits NorthMet EIS Co-lead Agency Project Managers: GLIFWC staff are writing in response to the co-lead agency memo of October 12th (FEIS reference MDNR 2015c) that identified a naturally occurring bedrock groundwater mound of approximately 1602 foot hydraulic head level 1 as a mechanism that could prevent the northward flow of contaminants from the PolyMet project. There are two points that make a natural groundwater mound adequate to prevent northward flow impossible at the PolyMet site. They are: 1. Land surface in the 100 Mile Swamp is at approximately 1600 feet elevation, making a bedrock groundwater mound of 1602 foot hydraulic head level impossible, and 2. Darcy's Law dictates that there must be a gradient to move water through geologic materials, yet there is little or no gradient to move leakage into the bedrock under the scenarios proposed by the co-lead agencies. 1 Hydraulic head is the level to which water will rise in a well. It is the combination of water pressure and water elevation. At the water table the hydraulic head equals the elevation but in deeper formations such as the bedrock at the PolyMet project, total head is the pressure head plus the elevation head. In their memo the co-lead seem to refer to elevated hydraulic head in the bedrock simply as "a bedrock groundwater mound" Fax of _letter_PolyMet_GWmound_at_closure.doc

2 GLIFWC is acting in coordination with our member tribes, including the Fond du Lac Band, to review and contribute to the PolyMet EIS process. As you may know, GLIFWC is an agency exercising delegated authority from 11 federally recognized Ojibwe (or Chippewa) tribes in Wisconsin, Michigan and Minnesota. 1 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. The proposed PolyMet mine is located within the territory ceded by the Treaty of The consulting firm for the co-lead agencies, Environmental Resource Management (ERM), conducted MathCad modeling to identify the amount of water that would need to flow into the bedrock in order to create a natural groundwater mound adequate to prevent northward flow of PolyMet pit water at closure. That analysis was discussed during a July 22, 2015 EIS inter-agency meeting and formed part of the basis of the co-lead agencies October 12, 2015 response memo titled: NorthMet Environmental Impact Statement Co-lead Agencies Consideration of Possible Mine Site Bedrock Northward Flowpath referenced in the FEIS as MDNR et al. 2015c. ERM's analysis illustrated that when the Peter-Mitchel taconite pits are dewatered to an elevation of 1300 feet, 8 inches per year of flux into the bedrock would be needed to create a bedrock groundwater mound of 1602 feet elevation, high enough to prevent northward flow. In their memo the co-lead agencies state: Figure 5 shows the computed bedrock groundwater-level profiles for different values of downward leakage at the end of Northshore operations. This is when the NorthMet East Pit has completely refilled to elevation 1,592 ft amsl and the Northshore Area 003 East Pit is completely dewatered to the pit bottom elevation of about 1,300 ft amsl. A groundwater mound occurs when the highest elevation of the groundwater-level profile is above the pit water levels at each end of the flow system. The mound represents a groundwater divide between the mines and would indicate that there is no continuous unidirectional flow across the flow system, which in this case is from NorthMet to Northshore. As shown on Figure 5, to have a mound that could be verified by field measurements would require an estimated downward leakage flux of about 8 in/yr. It is true that, conceptually, a bedrock mound between the mine projects would be enough to prevent northward flow from the PolyMet east pit at closure. However, the memo does not identify under what real-life conditions could there be enough flux into the bedrock to prevent northward flow. Analysis, within the physical constraints of the mine site, can be conducted to determine if such a bedrock groundwater mound high enough to prevent northward flow could be maintained. Such analysis is reported below. Review of site conditions: The physical conditions between the PolyMet and Peter-Mitchel mine pits play an important 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 Fax of _letter_PolyMet_GWmound_at_closure.doc

3 role in determining if a groundwater mound in the bedrock of sufficient head to stop northward flow can be maintained at closure. Land surface elevation.- Between the PolyMet east pit and the P-M Area-003 east pit lies the 100 Mile Swamp. The water elevation in the surficial aquifer within the swamp is at, or just below, the land surface. The land surface elevation is best described by the Lidar data collected in 2011 by the Minnesota DNR ( According to the MN-DNR the accuracy of the data set is just under a foot. (Tim Loesch, 2013, The base of surficial deposits is erroneously illustrated in Figure 5 of the co-lead agency October 12th memo (attached as Figure 1) as being at foot elevation. However, the land surface in that area is close to 1600 feet elevation (attached Figure 2). Neither the top of the surficial deposits (land surface) nor the thickness of the surficial deposits is identified in Figure 5 or in the text of the co-leads memo. Erroneously placing the surficial deposits above the actual land surface of the 100 Mile Swamp is no simple graphical error but critical to the co-lead argument that a natural bedrock groundwater mound could exist. Only with the surficial deposits (and thus the land surface) more than 25 to 50 feet in the air, could the mound described by the co-leads exist, not a logical scenario. Bedrock elevation.- The bedrock surface has been well described by the Minnesota Geological Survey. According to the Minnesota Geological Survey, the thickness of the surficial deposits vary from approximately 10 feet to 50 feet in depth under the 100 Mile Swamp (Minnesota Geological Survey, 2005: M-158 Bedrock geology database, bedrock topography, and depth to bedrock maps of the eastern half of the Mesabi Iron Range, northern Minnesota ) available at: Table 1. Elevation of land surface and top of bedrock and the calculated thickness of the surficial deposits along transect C-C' between the PolyMet east pit and the Peter-Mitchel pits. Values referenced in the text are highlighted. Distance from PolyMet east pit (feet) Elevation of Land surface Bottom of surficial deposits Thickness of surficial deposits (feet) along C-C' Thickness of surficial deposits.- Using the State of Minnesota information on the elevation of the land surface and the top of the bedrock, it is possible to calculate the thickness of the surficial deposits under the 100 Mile Swamp, i.e. the thickness of surficial deposits that water must pass through in order to contribute to a bedrock groundwater mound. For analysis purposes, a transect C-C' was identified between the PolyMet east pit and the Peter-Mitchel Area003-east pit (Figure 3). At 200 foot intervals along that transect the surface elevation and the elevation of the top of bedrock were identified from the state data sets in a GIS system (Table 1). At 200 feet north of the Polymet east pit Fax of _letter_PolyMet_GWmound_at_closure.doc

4 the thickness of the surficial deposits is calculated from state data as 14.4 feet thick. On the other hand, PolyMet's map of depth to bedrock (FEIS reference PolyMet 2015m, Large Figure 12) indicates that 200 feet north of the PolyMet east pit along cross-section C-C', the surficial deposits are 30 feet thick. It appears that the estimates using Minnesota DNR data may be underestimates of surficial deposits thickness, at least near the PolyMet east pit. In any case, it appears from the available State and PolyMet data, that the surficial deposits in the 100 Mile Swamp along transect C-C' are more than 14 feet thick. Vertical conductivity.- The vertical conductivity of the surficial deposits is an important parameter in determining the feasibility of a natural groundwater mound between Polymet and Peter- Mitchel pits. High values of vertical conductivity could be used in the Darcy's Law calculation. However, to put the vertical conductivity of the wetland deposits used in the FEIS in context, the applicant and co-leads originally proposed a vertical conductivity of ft/day for the wetland and glacial deposits that make up the surficial layer. That vertical conductivity, used in the project DEIS, was 3 orders of magnitude lower than that used in the FEIS ( ft/day). In a June 27, 2012 memo (SDEIS reference Polymet 2013i; available at: ), Barr Engineering discussed the conductivity switch from ft/day to ft/day and claimed that vertical conductivity in the surficial layer higher than ft/day (1X10-6 cm/s) would be "unrealistic." Water table head needed to cause 8 in/yr of leakage through the surficial deposits. Fundamental hydrologic principles must be considered when evaluating under what conditions 8 in/yr of flux could pass through the surficial formation into the bedrock. The controlling principle is known as Darcy's Law (see attached Addendum 1), which allows calculation of flux through a formation. Darcy's Law is based on the concept that water moves from areas of high hydraulic head level to areas of low head level and the flux is controlled by the conductivity of the formation. It is a form of Newton's Second Law applied to flow of water through an aquifer. Calculating flux through a formation requires knowledge of both the hydraulic head gradient and the conductivity of the formation material. The hydraulic gradient to move water vertically through the surficial aquifer into the bedrock is calculated as the water elevation at the top of the aquifer, i.e. the water elevation in the 100 Mile Swamp, minus the hydraulic head level in the bedrock. If the water head level in the bedrock is below the bottom of the surficial deposit, the gradient is considered to be 1. If the water head level is higher than the bottom of the surficial deposits the gradient is less than 1. If the hydraulic head in the bedrock is near the top of the surficial deposits (i.e. near the land surface) there is very little gradient and there can be little or no leakage. The quantity of flux through the surficial deposits that can be induced by the dewatering of adjacent mine pits is dependent on the conductivity of the surficial deposits and the groundwater head gradient across those deposits. As the water head level in the bedrock decreases the gradient increases. When a gradient of 1 is reached, the maximum flux, equivalent to the deposit vertical conductivity, will flow through the deposits. In the case of the deposits under the 100 Mile Swamp, the co-leads propose that the vertical conductivity is feet/day (12.26 inches/year). In order to get the substantial flux identified by the co-leads (8 in/yr) as necessary to maintain a groundwater mound, the gradient must be over 0.65 (8/12.26 = 0.65). Consider that at 1200 feet north of the PolyMet east pit, the location that ERM identified as the apex of the hypothetical groundwater mound (attached Figure 1), the surficial deposits are 41.3 feet Fax of _letter_PolyMet_GWmound_at_closure.doc

5 thick, the water level in the surficial deposits would need to be 26.8 feet (41.3X0.65) higher than the water head level in the bedrock in order to push 8 in/yr of leakage through the surficial deposits to the bedrock top. Given that the land surface is at feet, there is not enough vertical space to have the water table 26.8 feet higher than the 1602 bedrock mound proposed by the co-leads. As noted by the consultants for the co-leads (ERM) during the July 22, 2015 inter-agency technical meeting, the mechanism for 8 in/yr to move through the surficial deposits to the bedrock was not considered during their conceptual modeling. If that had been considered, ERM and the co-leads would have realized that the maintenance of anything close to a 1602 foot bedrock groundwater mound between the projects is impossible given that the land surface in the 100 Mile Swamp is at an approximate 1600 foot elevation. What downward leakage can the natural system provide? Using Darcy's Law, the height of the water in the 100 Mile Swamp (essentially the elevation of land surface), the surficial deposit thickness, and the hydraulic head level in the bedrock aquifer, one can calculate the flux that is possible given the proposed vertical conductivity (Kv) of the surficial deposits (Table 2). Table 2. Leakage (in/year) to the bedrock when the surficial deposits are 41.3 feet thick (i.e feet north of the PolyMet east pit) At 1200 feet from the PolyMet east pit, the location that ERM identified as the apex of the hypothetical groundwater mound (attached Figure 1), the land surface is at feet elevation (Table 1), the surficial deposits are 41.3 feet thick and 7.99 inches/year of flux is only possible if the water head level in the bedrock is less than 1576 feet (Table 2). If the water head level in the bedrock is 1592 feet (the elevation of the PolyMet east pit) the head gradient is reduced to 0.26 and only 3.24 in/yr of flux can pass through the surficial deposits. Even if the vertical conductivity is twice what has been proposed by PolyMet and the co-leads (i.e. Kv= ft/day rather than ft/day), only 6.48 in/yr of flux can pass through the surficial deposits if the bedrock water head level is 1592 feet (Table 2). It is apparent that with the vertical conductivity proposed by the co-leads, it is impossible for enough water to pass through the surficial deposits to maintain a mound above 1592 feet, much less ERM's hypothetical 1602 foot mound. In the middle of the 100 Mile Swamp, at the Partridge River, the surficial deposits are even thicker. It does not appear that under values of Kv that have been identified by the applicant and the co-leads as realistic, a groundwater mound adequate to prevent northward flow is possible. Conclusion: The fundamental problem with the hypothesized mound is, that: 1) A bedrock groundwater mound of 1602 feet is above the 1600 foot land surface; and 2) In order to for the needed leakage (8 in/yr) to occur, either (a) the bedrock mound must be below the level needed to prevent northward flow, or (b) the water table at the surface must be well above the land surface Fax of _letter_PolyMet_GWmound_at_closure.doc

6 Therefore, we do not believe that the hypothetical bedrock groundwater mound suggested by the co-leads can exist at the site post-closure. Analysis based on information from the site, i.e. land and formation elevations, support the conclusion that a natural bedrock groundwater mound high enough to stop northward flow is not possible. It is only with assumed conditions that have not been proposed to occur at the site (i.e. high wetland soil vertical conductivity and higher than existing land elevations) that a natural groundwater mound, adequate to stop northward flow, could be maintained at closure. Thank you for considering this issue. As we have in the past, we ask to have technical discussions with other agency staff so that a more feasible representation of hydrology at the site can be developed. Sincerely, John Coleman, GLIFWC Environmental Section Leader cc: Randall Doneen, Environmental Review Unit Supervisor, MN-DNR Brenda Halter, Forest Supervisor, Superior National Forest Tamera Cameron, Chief, Regulatory Branch, St Paul District of the Army Corps of Engineers Kenneth Westlake, NEPA Coordinator, USEPA Region 5 Nancy Schuldt, Water Projects Coordinator, Fond du Lac Environmental Program Neil Kmiecik, GLIFWC Biological Services Director Ann McCammon Soltis, Director, GLIFWC Division of Intergovernmental Affairs Fax of _letter_PolyMet_GWmound_at_closure.doc

7 Figure 5: Scoping Calculation - Year Effect of Downward Leakage Rates on Bedrock Groundwater-Level Profiles Flooded NorthMet East Pit Water Level = 1592 ft msl Elevation (ft msl) Downward Leakage (in/yr) Downward leakage from surficial deposits into bedock Virginia Fm BIF Dewatered Area 003 East Pit Water Level = 1300 ft msl Distance North of NorthMet East Pit (ft)

8 Figure 5: Scoping Calculation - Year Effect of Downward Leakage Rates on Bedrock Groundwater-Level Profiles Flooded NorthMet East Pit Water Level = 1592 ft msl Elevation (ft msl) Downward Leakage (in/yr) Downward leakage from surficial deposits into bedock Virginia Fm BIF Dewatered Area 003 East Pit Water Level = 1300 ft msl Distance North of NorthMet East Pit (ft)

9 Figure 3

10 Addendum 1: The flow of ground water follows a relation called Darcy s Law. The flux of ground water (discharge per unit cross-sectional area) is equal to the product of the hydraulic gradient and the hydraulic conductivity of the medium through which the flux is moving. Gradient is measured in the direction of the flow while the relevant conductivity is that measured perpendicular to the flow. It is expressed as: q = (K) (I), where: q = ground water flux (discharge per unit area) dimensions = [(L 3 /T)/L 2 ] = [L/T] K = hydraulic gradient [L/T], and I = hydraulic gradient [L/L]. I = delta H/B, where: delta H is the head drop across the transmitting medium (the unconsolidated sediments in this case). Dimensions = [L], and B = the thickness of the transmitting medium [L] In this case, delta H will be the difference in head between the water table near the top of the sediments and that in the bedrock below them. It has been proposed that a vertical influx of 8 in/yr is needed to produce a bedrock ground water mound north of the PolyMet site adequate to prevent northward flow when the adjacent taconite pits are at 1300 feet. The vertical conductivity (Kv) of the unconsolidated sediments around the site has also been argued to be ft/day (12.26 in/yr). Therefore, the gradient need to drive a flux of 8 /yr = I = q/k = (8/(12.26) = This value is dimensionless, meaning it can be either (m/m) or (ft/ft). For the sediment thickness at 1200 ft north, the head of the water table needs to be: delta H = 0.65 * 41.3 ft = 26.8 feet above the head in the bedrock. 1/1