Wetland Hydrology Monitoring Report 2007-2009

NorthMet Project

Prepared for PolyMet Mining Inc.

March 2010

NorthMet Project

Prepared for PolyMet Mining Inc.

March 2010

4700 West 77th Street Minneapolis, MN 55435-4803 Phone: (952) 832-2600 Fax: (952) 832-2601 Wetland Hydrology Monitoring Report 2007-2009 PolyMet Mining Inc.

March 2010

Table of Contents

Executive Summary...... vi

1.0 Objectives ...... 1

2.0 Methods...... 2 2.1 Well Placement ...... 2 2.2 Well Construction and Installation...... 3 2.3 Water Level Recording ...... 4

3.0 Wetland Hydrology and Climatic Criteria ...... 5 3.1 Wetland Hydrology Criteria...... 5 3.2 Normal Climatic Conditions ...... 5 3.3 Climatic Conditions - Water Years 2005-2009...... 6

4.0 Monitoring Schedule...... 11

5.0 Results...... 12 5.1 General Site Hydrology...... 12 5.2 Hydrogeologic Conditions ...... 12 5.3 Soil Characteristics...... 14 5.4 Wetland Hydrology...... 15 5.5 Wetland Hydrology Elevations...... 24 5.6 Hydrology Results Summary ...... 24

6.0 Future Actions...... 26

8.0 References...... 27

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\Report

iii List of Tables

Table 1 2007-2009 Wetland Monitoring Well Summary

Table 2 2005-2009 Wetland Water Elevation Summary

Table 3 Precipitation Summary Compared to WETS Data

Table 4 Precipitation During the 2005-2009 Growing Seasons

List of Figures

Figure 1 Project Location

Figure 2 Mine Site Overview

Figure 3 2005-2007 Wetland Monitoring Ground and Water Level Elevations

Figure 4 2008-2009 Wetland Monitoring Ground and Water Level Elevations

Figure 5 Precipitation Statistics for 2004-2009 Water Years

Figure 6 2005-2009 Wetland Hydrology Monitoring Data, Northwest Mine Site Area – Wells 4, 4A, 5, and 18

Figure 7 2005-2009 Wetland Hydrology Monitoring Data, North-Central Mine Site Area – Wells 2, 10, 11, and 12

Figure 8 2005-2009 Wetland Hydrology Monitoring Data, Northeast Mine Site Area – Wells 13, 14, and 15

Figure 9 2005-2009 Wetland Hydrology Monitoring Data, South-Central Mine Site Area – Wells 8, 9, 16, and 21

Figure 10 2005-2009Wetland Hydrology Monitoring Data, Southwest Mine Site Area – Wells 1, 3, 6, 7, 17, 19, and 22

Figure 11 2005-2009 Wetland Hydrology Monitoring Data, Reference Wells West of Mine Site – Reference Wells Ref1 and Ref2

Figure 12 Precipitation Summary for 2005-2009

Figure 13 2006-2009 Wetland Hydrology Monitoring Data – Well 1

iv Appendices

Appendix A 2006 Wetland Hydrology and Water Elevation Data

Appendix B 2007 Wetland Hydrology and Water Elevation Data

Appendix C 2008 Wetland Hydrology and Water Elevation Data

Appendix D 2009 Wetland Hydrology and Water Elevation Data

Appendix E Well Location Photographs

Appendix F Depth to Bedrock

Appendix G 2006 Hydrogeologic Pumping Test

Appendix H Wetland Monitoring Well Transects

Appendix I Water Hydrology by Wetland Type

Executive Summary

• This report was submitted to the U.S. Army Corps of Engineers (Corps) and the Minnesota Department of Natural Resources in March 2010. It is intended to meet the reporting requirements for pre-project wetland hydrology monitoring. The wetland hydrology monitoring study followed the Corps-approved protocols described in the Wetland Hydrology Study Plan (Barr, 2005).

• Documentation is presented in this report for the third, fourth, and fifth years of wetland hydrology monitoring and includes climate, water level, and water elevation data. The data from the first and second years of monitoring were presented in the Preliminary Wetland Hydrology Study Reports (Barr, 2006a and 2006b). One partial year (2005) of data and four full years (2006-2009) of baseline wetland hydrology data have been collected for the NorthMet Site.

• Wells were initially installed in 19 wetland monitoring locations in 2005, four of which were electronic wells. At the end of 2007, two wells were removed from the study because they were determined to be within the proposed project footprint. In 2008, one well was relocated within the same wetland complex, two wells were installed in new wetland locations at the NorthMet Site, and two wells were installed in reference wetlands located west of the NorthMet Site that will not be affected by the proposed project. During 2008-2009, there were a total of 21 sites monitored using manual and electronic wells.

• Water levels were recorded in the electronic wells every two to four hours during the 2005- 2009 monitoring periods. Manual well data was recorded twice per month in 2005-2007 and once per month in 2008-2009. The electronic well data was collected during November 2005, and throughout the 2006-2009 growing seasons (May 9-October 6) for most locations. Frozen or inundated conditions prevented early installation of some electronic wells.

• The 2005-2009 data show the presence of wetland hydrology in all monitored wetlands. The water table within the wetlands was generally within 12 inches of the ground surface for the majority of each growing season, which meets the minimum technical standard for wetland hydrology (Corps, 2005).

• During the past four water years, the annual precipitation was within or above the normal range. During the 2006-2009 growing seasons, the precipitation was drier than normal in 2006 and 2008, wetter than the normal range in 2007, and within the normal range in 2009.

Daily and monthly precipitation data were compared to WETS precipitation statistics from the National Weather Station in Babbitt, MN to determine climatic normalcy.

• The four full years of monitoring data indicate that the majority of the wetlands on the site have hydrology supported primarily by precipitation, with some localized groundwater contributions. The groundwater flow paths are generally short with recharge areas (uplands) located close to the discharge areas (wetlands). Surface water runoff and local groundwater contributions from uplands can cause increased mineral content within the water in adjacent wetlands. Once the water reaches the wetlands, infiltration through the organic soil is limited by the increased decomposition of organic material with depth, and associated decrease in vertical and horizontal hydraulic conductivity.

• There is a lack of connectivity between the shallow water table in the wetlands and the deeper bedrock aquifer. The depth of soil and till overlying the bedrock ranges up to 33 feet, with bedrock outcrops present that alter local groundwater flow paths. A pumping and isotope test conducted in 2006 indicated that the water within the bedrock is derived from aquifer recharge rather than surface water seepage. The variability of the bedrock and soil surface, along with the location of the surface water divide, create localized, short, surficial groundwater flow paths within the watersheds on the NorthMet site.

• The hydrologic regimes are consistent throughout the large wetland complexes. The maximum water level fluctuation was less than 12 inches in two wetlands (58 and 114) and between 12 to 18 inches in all other wetlands from 2005-2009. Wells located in the southwest and south-central areas show the greatest range of water table fluctuations, while wells in the northwest area show the least fluctuation.

• The wetlands exhibit stable year-to-year water levels and elevations. Water levels in all wells fluctuated in direct response to precipitation events, with the exception of Well 9 in 2008- 2009 and Well 7 in 2009. Wells 9 and 7 showed stability indicative of contributing discharge from the larger upstream watersheds.

• The hydrographs in the monitored black spruce and tamarack dominated wetlands (coniferous bogs) exhibited fluctuations indicative of saturated, precipitation-driven hydrology (i.e., rapid response to precipitation with mid-summer drawdown).

• The 2008-2009 data for the reference wetlands provide baseline data for comparison with the black spruce bogs and alder thickets located on the NorthMet Site.

vii

1.0 Objectives

On behalf of PolyMet Mining, Inc., Barr Engineering Company (Barr) is submitting documentation of the third, fourth, and fifth years of wetland hydrology monitoring including hydrology monitoring data, water elevation data, and climatic data for the proposed NorthMet project (Figures 1 and 2). The data from the first and second years of monitoring were presented in the Preliminary Wetland Hydrology Study Reports (Barr, 2006a and 2006b). The monitoring study has primarily followed the protocols described in the Wetland Hydrology Study Plan (Barr, 2005). The objectives of the study are to:

1. Provide a better understanding of the wetland hydrology at the proposed project site.

2. Collect baseline hydrology data to assess the effect of the proposed project on wetland hydrology.

3. Review the data collected in the hydrogeologic study along with the wetland hydrology data to determine whether specific wetlands have perched water tables or are in direct hydrologic connection with the surficial deposits aquifer.

4. Assist in determining the potential for indirect wetland impacts resulting from the proposed project.

2.0 Methods

2.1 Well Placement Wetland hydrology was monitored at the proposed NorthMet Site using manual and electronic/recording wells from 2005-2009. Wetland hydrology monitoring wells were initially installed in 19 wetland locations in 2005 (Figure 3). Twenty manual wells were installed on June 28- 30, 2005 and October 25, 2005. Manual Wells 4 and 5 were placed near each other in the same wetland location. Four recording wells were installed near manual wells (Wells 1, 4, 7, and 12) on November 9-11, 2005. A total of 11 monitoring locations were situated around the perimeter of the project and are not expected to be impacted by the project. The remaining 8 monitoring locations have the potential to be impacted by the project depending on the final mine and stockpile plans. In 2005, the primary differences from the planned well locations in the Wetland Hydrology Study Plan (Barr, 2005) was the relocation of Well 18 to the south, the addition of two wells (Wells 4 and 5) in the northwest corner of the project, and the substitution of Well 4A in the place of the planned locations for Wells 4 and 5. In 2005, the remainder of the wells were installed within the general proximity of the planned locations as presented in the Wetland Hydrology Study Plan (Barr, 2005).

In 2006 and 2007, well monitoring was conducted in the same 19 wetland locations as in 2005, with a total of 20 manual wells and 4 recording wells (Figure 3). Two manual monitoring wells (Wells 3 and 17) were removed from the study after the 2007 monitoring period since they were determined to be located within areas that will be directly impacted by the proposed project.

In 2008, 21 wetland locations were monitored with 22 manual wells and 21 recording wells (manual Wells 4 and 5 are both paired with recording Well 4; Figure 4). Fourteen recording wells were installed near 14 existing manual wells on May 21-23, 2008. Recording Well 9 was installed near manual Well 9 on June 27, 2008. On May 22, 2008 a pair of manual and recording wells were installed at two new locations (Wells 21 and 22). Recording Well 1 and manual Well 1 were relocated on May 22, 2008 since it was determined the original location was within an area to be directly impacted by the proposed project. Two pairs of manual and recording wells were installed as reference wells in two reference wetlands located west of the Mine Site on May 21, 2008. The purpose of monitoring the reference wetlands is to document the natural hydrologic fluctuations in wetlands that will not be affected by the proposed project to facilitate interpretation of the project data in relation to climatic fluctuations. The manual well data were used to validate the general trends of the recording well data.

Tables 1 and 2 provide the Universal Transverse Mercator (UTM) coordinates, ground surface elevation, average depth to water, and average water level elevation for the 2005-2009 monitoring wells. Appendices A, B, C, and D provide wetland hydrology and water elevation data for the monitoring wells for 2006, 2007, 2008, and 2009, respectively. Photographs of the well locations are provided in Appendix E. Monitoring of these wells will continue in accordance with the planned study. If it is determined, at some future time, that the wells are not providing useful information, then the monitoring may cease.

2.2 Well Construction and Installation The manual wells installed in 2005 consisted of an approximately 1.5 to 2.5-foot length of 1.25-inch diameter, 0.01-inch slotted PVC commercial well screen wrapped with a filter sleeve, and threaded to a 1.0 to 2.5-foot riser. The manual wells installed in 2008 consisted of a 2.5-foot length of 1.25-inch diameter, 0.01-inch slot PVC commercial well screen wrapped with a filter sleeve, and threaded to a 2.5-foot solid PVC riser. The well screens were typically installed to a depth of 1.8 to 4.5 feet (14.1 to 44.5 inches) below the ground surface (Table 2).

The recording wells were installed to provide a continuous measurement of water levels during the monitoring period. The recording wells are Ecotone™ WM capacitance water level monitoring instruments manufactured by Remote Data Systems, Inc. The wells consist of a 20-inch (2005 wells) or 32-inch (2008 wells) length of 1.5-inch diameter, 0.01-inch slotted PVC commercial well screen integrated below 14 inches of solid PVC riser. The well screens in 2005 and 2008 were typically installed to a depth of 1.8 to 3.7 feet (21.5 to 44.5 inches) below the ground surface (Table 2).

All wells were backfilled with native soil, which was mounded at the surface to prevent water from preferentially infiltrating the area surrounding the well. None of the wells were installed through a confining soil layer into a more permeable layer below. The soils encountered were typically peats and mucks, however sand, silty loam, and sandy clay were encountered in some wells (Table 1). In situations where mineral soils were present at depth, wells were installed into the mineral layer below the peat since it appeared that the layers were hydraulically connected. Each well was covered with a slip cap and a breather hole was installed near the top of the riser to equalize pressure. A hole was also drilled in the cap at the bottom of each well to allow water to drain out of the well casing. All wells were located with a Global Positioning System (GPS) with 3-meter accuracy immediately after installation. The elevation of the top of the well casing and the ground surface at each well was also surveyed to within approximately 0.1 ft MSL in December 2005, January 2006, December 2007, September 2008, February 2009, and June 2009 using a survey-grade GPS unit.

2.3 Water Level Recording Typically, the data from the recording wells were downloaded twice per month in 2005-2007 and once per month in 2008 and 2009. The recording wells were set up to collect a water level reading every 2 to 4 hours during the monitoring period, which extended from November 11-23, 2005, April 27-October 25, 2006, April 6-November 26, 2007, May 7-November 26, 2008, and April 28-October 29, 2009. Manual water level measurements were recorded in twice per month in June and October- November 2005, twice per month from April-November in 2006-2007, once per month from May- November in 2008, and once per month from April-October in 2009. During the monitoring period, manual water levels were recorded 5-7 times in 2005, 13 times in 2006, 15 times in 2007, 8 times in 2008, and 7 times in 2009.

Frost action and shrinking and swelling of peat soils along with fluctuation in water levels can affect the elevation of the wells. Therefore, the distance from the top of the well casing to the ground surface was measured during each monitoring event to ensure consistent measurement of the water level below the ground surface. The inserts for the recording wells were removed for the winter on November 24-26, 2007, November 24-26, 2008, and October 28-29, 2009. The casings for the recording and manual wells were generally left in place.

3.0 Wetland Hydrology and Climatic Criteria

3.1 Wetland Hydrology Criteria The minimum technical standard for an area to meet the technical wetland hydrology criteria in accordance with the Army Corps of Engineers 1987 Wetland Delineation Manual (1987 Manual) is to have soil saturation to the ground surface, or to be inundated continuously for 5 percent of the growing season in most years. The growing season dates are determined using the 1987 Manual methods, which allow for estimating the starting and ending dates of the growing season based on the average first and last dates on which the air temperature drops to or rises above 280 F based on long- term temperature data. The Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Northcentral and Northeast Region (U.S. Army Corps of Engineers, 2009) more precisely defines the growing season as the period when the soil temperatures exceed 41o F at a depth of 12 inches or that period in which vegetation is actively growing (for trees and shrubs, after bud break in the spring).

According to the Natural Resources Conservation Service WETS data (statistical climate data for determining wetland hydrology), the normal growing season for the Babbitt area, based on the 1961- 1985 climatic record, begins on May 9 and ends October 6, a total of 151 days. Based on the normal growing season in Babbitt, the duration in which soils must be saturated to the surface or be inundated is about 7.6 days (calculated as 151 days x 5 percent = 7.6 days).

3.2 Normal Climatic Conditions Hydrology monitoring studies that evaluate the presence or absence of wetland hydrology must also consider “climatic normalcy.” The wetland hydrology criteria in the 1987 Manual states that soils must be saturated to the surface “in most years,” which means in more than 50 percent of years. This definition acknowledges that some wetlands will not exhibit wetland hydrology in some years (typically years with below normal precipitation).

To evaluate and understand the wetland hydrology monitoring data; precipitation data during the monitoring period was collected and analyzed. The WETS precipitation statistics from the Babbitt National Weather Service (NWS) station were collected for the normal historic period 1961 to 1985 and used to determine precipitation normalcy during the study period (Table 3). Daily precipitation data was collected from the Babbitt NWS station and compared to the Babbitt NWS WETS averages to determine climate normalcy during the 2005-2009 Water Years (e.g., in 2009 the water year is

defined as October 1, 2008 through September 30, 2009). The cumulative 30-day precipitation is shown on Figure 5 in comparison to the long-term range of normal 30-day precipitation. 3.3 Climatic Conditions - Water Years 2005-2009 Prior to the start of the wetland hydrology monitoring in 2005, the prior three water years (2002, 2003, and 2004) were below the normal range for annual precipitation (Table 3). The wetland hydrology monitoring started in late 2005 during a water year that was slightly above the normal range for annual precipitation. The 2006 and 2008 water years were within the normal range for annual precipitation, while annual precipitation during the 2007 water year was above the normal range. Annual precipitation during the 2009 water year was below the normal range. Figure 5 shows multiple periods for Water Years 2005-2009 in which the 30-day cumulative precipitation was both above and below the normal range. The peaks typically occurred after a single large precipitation event (greater than one inch) or after a series of smaller rainfall events over a longer time period (days). The climatic conditions (precipitation, evapotranspiration, etc.) along with the general setting (tree density and type, canopy cover, understory, etc.) influence the water table elevations at the wetland hydrology monitoring sites, as shown in Figures 6-13 and in Appendices A-D.

The precipitation during the normal growing season (May 9- October 6, 151 days) of each year was compared to determine the number of days below the normal range, within the normal range, and above the normal range of annual precipitation (Table 4). While 2005 and 2006 had a similar number of days within the normal range of precipitation, 2005 had 59 days (38 percent) above the normal precipitation range while 2006 only had 20 days (13 percent). In contrast, 2007 and 2008 had similar numbers of days within all three precipitation ranges during the growing season, with precipitation more than one inch below the normal precipitation range during July and August. During the growing season in 2009, there were 114 days within the normal range of precipitation and only 2 days above the normal range of precipitation. In summary, the precipitation during the growing season of 2009 represents normal conditions, 2005 and 2007 were wetter than normal, and 2006 and 2008 represent drier conditions.

The 2005-2009 water years are discussed in more detail as follows:

Water Year 2005

The data show that the 2005 water year was slightly above the normal range for annual precipitation following 3 straight years of annual precipitation below the normal range. The 2005 water year had equal months of precipitation below, within, and above the normal range. The two months during

which the majority of the monitoring was conducted both experienced monthly precipitation above the normal range. Due to the long, dry three-year period preceding this study, it was expected that all of the wetlands monitored may not exhibit their normal hydrologic regime.

There were a total of 8 storm events during 2005 with over 1 inch of precipitation, occurring in May, June, September, and October. The largest event was 2.17 inches of rainfall on May 26, 2005.

Water Year 2006

Precipitation during the 2006 water year was at the low end of the normal range, or 2.5 inches below the average annual precipitation. Monthly precipitation during the 2006 water year was below the normal range in June, August, and September, typically months with warm weather and high rates of evapotranspiration, which contributed to lower water levels in the wetlands. Monthly precipitation was above the normal range in three months early in the 2006 water year (November, February, and March), and one month in summer (July).

For most of the 2006 growing season, the 30-day cumulative precipitation fluctuated in and out of the normal range. Precipitation was within the normal range for about 38 percent (57 days) of the growing season (Table 4). During the remainder of the growing season the 30-day cumulative precipitation was:

• Below the normal range: May 9 (1 day),

• Within the normal range: May 10 – May 12 (3 days),

• Above the normal range: May 13 – May 18 (6 days),

• Within the normal range: May 19 – June 5 (18 days),

• Above the normal range: June 6 – June 8 (3days),

• Within the normal range: June 9 – June 11 (3 days),

• Below the normal range: June 12 – July 23 (42 days),

• Within the normal range: July 24 – July 30 (7 days),

• Above the normal range: July 31 – August 1 (2 days),

• Within the normal range: August 2 – August 13 (12 days),

• Above the normal range: August 14 – August 22 (9 days),

• Within the normal range: August 23 – August 29 (7 days),

• Below the normal range: August 30 – September 10 (12 days),

• Within the normal range: September 11 – September 12 (2 days),

• Below the normal range: September 13 – October 1 (19 days),

• Within the normal range: October 2 – October 6 (5 days).

There were also several spikes when precipitation was above the normal range, however, these periods were short-lived and generally resulted from single storm events (Appendix A). There were a total of 4 storm events during 2006 with over 1 inch of precipitation, all occurring between July 3 and August 14. The largest event was 1.76 inches of rainfall on August 13-14, 2006.

Water Year 2007

The 2007 water year was above the normal range for annual precipitation. During the 2007 water year, precipitation was below the normal range for 4 months, within the normal range for 3 months, and above the normal range for 5 months. During the 8 months of wetland hydrology monitoring in 2007, precipitation was below the normal range in July, August, and November; within the normal range in June; and above the normal range in April, May, September, and October. The dry months of July and August contributed to low water levels in the area. In September and October the area received more than 12 inches of precipitation above the average monthly precipitation.

For most of the 2007 growing season, the 30-day cumulative precipitation fluctuated in and out of the normal range. Precipitation was within the normal range for only about 10 percent (15 days) of the growing season (Table 4). During the remainder of the growing season the 30-day cumulative precipitation was:

• Within the normal range: May 9 – May 20 (12 days),

• Above the normal range: May 21 – June 29 (40 days),

• Within the normal range: June 30 – July 2 (3 days),

• Below the normal range: July 3 – September 9 (69 days),

• Above the normal range: September 10 – October 6 (27 days).

There were several spikes when precipitation was above the normal range, with large events occurring in early September (Appendix B). There were a total of 7 storm events during 2007 with

over 1 inch of precipitation, occurring in April, May, June, September, and October. The largest event was 8.22 inches of rainfall on September 10, 2007.

Water Year 2008

The data show that the 2008 water year was near the upper end of the normal range for annual precipitation. During the 2008 water year, precipitation was below the normal range for 5 months, within the normal range for 1 month, and above the normal range for 6 months. During the 8 months of wetland hydrology monitoring in 2008, precipitation was below normal in July, August, and November; within the normal range in May and October; and above the normal range in April, June, and September. The dry months of July and August contributed to low water levels in the area.

For the 2008 growing season, the 30-day cumulative precipitation data was within the normal range for about 18 percent (27 days) of the growing season (Table 4). During the remainder of the growing season the 30-day cumulative precipitation was:

• Above the normal range: May 9 – May 25 (17 days),

• Within the normal range: May 26 – June 5 (11 days),

• Above the normal range: June 6 – July 4 (29 days),

• Within the normal range: July 5 (1 day),

• Below the normal range: July 6 – September 11 (68 days),

• Within the normal range: September 12 – September 26 (15 days),

• Above the normal range: September 27 – October 6 (10 days).

There were a total of 5 storm events during 2008 with over 1 inch of precipitation, occurring in April, June, and September (Appendix C). The largest event was during a two-day period with 2.93 inches of rainfall on June 5 and 6, 2008.

Water Year 2009

The data show that the 2009 water year was below the normal range for annual precipitation. During the 2009 water year, precipitation was below the normal range for 5 months, within the normal range for 3 months, and above the normal range for 4 months. During the 7 months of wetland hydrology monitoring in 2009, precipitation was below the normal range in May, June, July, and September; within the normal range in August and October; and above the normal range in April.

For the 2009 growing season, the 30-day cumulative precipitation data was within the normal range for about 76 percent (114 days) of the growing season (Table 4). During the remainder of the growing season the 30-day cumulative precipitation was:

• Within the normal range: May 9 – May 16 (7 days),

• Above the normal range: May 16 – May 17 (2 days),

• Within the normal range: May 18 – May 29 (12 days),

• Below the normal range: May 30 – June 8 (10 days),

• Within the normal range: June 9 – July 8 (30 day),

• Below the normal range: July 9 – July 15 (7 days),

• Within the normal range: July 16 – September 18 (65 days),

• Below the normal range: September 19 – October 6 (18 days).

There were a total of 2 storm events during 2009 with over 1 inch of precipitation, occurring in March and August (Appendix D). The largest event was 1.43 inches of rainfall on August 20, 2009.

4.0 Monitoring Schedule

Monitoring started each year shortly before the beginning of the statistical start of the growing season (May 9), in late April 2006, early April 2007, early May 2008, and late April 2009. After installation, water levels were recorded every two to four hours in the recording wells and the data were typically downloaded once every month. Water levels were typically measured in each manual well once every two weeks from April 25-November 22, 2006, April 6-November 26, 2007 and once every month from May 7-November 26, 2008 and April 28-October 29, 2009.

5.0 Results

5.1 General Site Hydrology The Partridge River is located to the north, east, and south of the NorthMet site (Figure 2). The proposed Mine Site is located on the north side of the Dunka Road. There is a surface drainage divide oriented generally from southwest to northeast near the northern border of the site (Figure 2). The majority of the Mine Site (80 percent) drains south through culverts under Dunka Road and on to the Partridge River through extensive wetland complexes. The remaining 20 percent of the Mine Site drains north to Hundred Mile Swamp and the Partridge River or northeast to the Partridge River.

The bedrock surface is variable across the site with bedrock exposed at the surface in some locations (Appendix F). The soil/till thickness is also variable ranging from a thin layer over the bedrock to 50- 60 feet thick. The bedrock has low primary permeability (Siegel and Ericson, 1980) so groundwater flow within the bedrock is through fractures or other secondary porosity features (Barr, 2008b). Because of the low permeability of the bedrock, the interaction between the surficial deposits and the bedrock aquifers is assumed to be insignificant, according to Siegel and Ericson (1980).

The surficial groundwater flow paths are generally very short on the site with recharge areas (uplands) located very close to the discharge areas (wetlands). In addition, bedrock outcrops cause changes in the local flow patterns (Siegel and Ericson, 1980). The surface water divide is located north of the proposed pit locations with surface water north of this boundary flowing north. South of the proposed pit locations, the soil surface and bedrock surface slope southward past Dunka Road and the railroad. This variability of the bedrock and ground surfaces, along with the location of the surface water divide, limits the length of the surficial groundwater flow paths within the watersheds to short localized flowpaths, rather than long regional flowpaths.

5.2 Hydrogeologic Conditions A 30-day aquifer performance test (i.e., pumping test) was conducted from October 19, 2006 through November 18, 2006 to assist in understanding the hydrologic connectivity between the wetlands, the surficial deposits aquifer, and the bedrock aquifer. Well and piezometer locations and data are provided in Appendix G. More detailed information and results of the pumping test are provided in the Phase III Hydrogeologic Investigation report (Barr, 2007). The distance of each observation well from pumping Well P2 is identified in Appendix G, Table 1 and Figure 1. The hydrographs for the wells and piezometers are shown in Appendix G, Figures 2-5.

Water levels in pumping Well P2, observation wells (Ob2, 2, 12, 20), and piezometers (2P, 12P, and 20P) were monitoring using pressure transducers and data loggers. Additional wetland hydrology monitoring well data was evaluated for this section including Wells 1R, 4R, 7R, and 12R. Pumping Well P2 was located in the Virginia Formation and was installed as an open hole bedrock well from 27 to 610 feet below the ground surface (Appendix G, Table 1). Well Ob2 was located in the Duluth Formation and was installed as an open hole bedrock well from 18-100 feet below the ground surface. Wells 4R, 12, and 20 were shallow wells (2.3 to 3 feet total depth) located in organic soil and screened at a depth of 0.8 to 3 feet below the ground surface. Wells 2P, 12P, and 20P were deeper wells (7.5 feet total depth) located in organic soil and screened at 6.5 to 7.5 feet below the ground surface.

Pumping test Well P2 was located in the upland area located south of Well 2 (Wetland 100; Appendix G, Figure 1). Existing wetland hydrology monitoring wells 4R and 12 were used to evaluate effects of bedrock aquifer drawdown on the surficial aquifer along with an additional well location (Well 20) that was established near the edge of Wetland 100, south of Well 2. Continuous recording data loggers were installed in the wells and piezometers and were began operating approximately 30 days prior to the start of the pumping test and continued for 10 days after pumping ceased (Appendix G, Figures 2-5).

The hydrogeologic investigation found that during the pumping test, pumping Well P2 (located in bedrock) the maximum drawdown was 209 feet (Appendix G, Table 1, Figure 2). During the pumping test, Well Ob2, also located in bedrock, the maximum drawdown was 4.6 feet (Appendix G, Table 1, Figures 2 and 3). The wells and piezometers, installed in the organic soils above the bedrock, had maximum drawdowns of 6.0 and 5.4 inches, respectively (Appendix G, Table 1, Figures 2-5). The precipitation during October 2006 was within the normal range, however it was below the normal range for November 2006 (Table 3; Figures 2-5). During the October 19-November 18 period, the 30-day cumulative precipitation was below the normal range for about 58 percent (18/31 days) during the pumping test.

Piezometers 12P and 20P showed a general decrease in water levels with a maximum drawdown during the pumping test of 0.5 feet (Appendix G, Figure 3). Piezometer 20P was located 145 feet away from pumping Well P2 and 12P was located at a distance of 1,400 feet (0.3 miles). However, the maximum drawdown of wells located 0.7 to 1.9 miles from pumping Well P2 were 0.3 to 0.5 feet during the same time period, which indicates the drawdown of the surficial wells and piezometers

during this time period may have been the result of the dry conditions, rather than the pumping test (Appendix G, Table 1).

At the end of pumping test, the water level in Piezometer 20P (installed at a depth of 7.5 feet in organic soil) continues to decrease, while the water level in Well 20 (installed at a depth of 2.4 feet in organic soil) begins to rise. Water levels in other wells and piezometers also continued to generally decrease until rainfall at the end of November. The difference in the response of the Piezometer 20P and Well 20 likely show the lack of hydrologic connectivity between the surficial peat soil and the more decomposed deeper peat soil. Water levels in piezometer 2P fluctuated during the pumping period, but did not display the same overall downward trend as the other wells and piezometers. (Appendix G, Figure 3). The results of the analysis found that with the exception of piezometer 20P, which is the deep piezometer located closest to the pumping well, the decrease in water levels were not attributed to pumping. None of the manual or recording wells monitored for the wetland hydrology study in 2006 showed a response to the pumping test.

Groundwater samples were collected weekly for pumping Well P2 for the duration of the 30-day pumping test. Samples for laboratory analysis of бD, б18O, tritium, and б13C of dissolved organic carbon were collected, filtered, placed into laboratory-supplied containers and submitted for isotope analysis. Water isotope data from pumping Well P2 were plotted with precipitation data from the Marcell Experimental Forest Northern Research Station, located approximately 70 miles west of the Mine Site. The pumping Well P2 data plot very near the inferred meteoric water line. This result suggests the source of the majority of the groundwater that was pumped during the 30-day test was aquifer recharge and not seepage from surface water features, such as the Peter Mitchell Pit or wetlands. Evaporation from open water enriches the water in the heavier isotopes. Groundwater that is derived from seepage from surface water is expected to be enriched in oxygen-18 and deuterium and would not fall on the regional meteoric water line.

5.3 Soil Characteristics The soils on the site have formed from loamy drift and the underlying dense Rainy lobe till of the Late Wisconsinan glaciation (Natural Resources Conservation Service (NRCS) 2008). The dense underlying till acts as an aquitard that restricts downward water flow, therefore, most of the mineral soils in the depressional and flat-bottom areas of the landscape experience perched water tables during late spring and early summer at depths up to 1 to 3 feet. Mineral soil series present at the NorthMet Site include the very poorly-drained Bugcreek, with the better-drained soils including Babbitt, Eaglenest, Eveleth, and Wahlsten.

The upland soils at the Mine Site typically have high infiltration rates with little runoff and are usually found on bedrock-controlled uplands. The majority of the extensive wetland complexes on and adjacent to the site are mapped as ELT 6-LPN-Lowland Organic Acid to Neutral by the U.S. Forest Service (USDA-USFS 2007), which is equivalent to the Rifle mucky peat and Greenwood peat mapping units in the NRCS soil classification system (Figure 2). These soils are typically characterized by having fibric peat in the upper horizons underlain by mucky peat to a depth of up to 5 feet or more.

An overburden characterization study was conducted in 2008 which provided boring logs for upland and wetland points across the site (Appendix H). The depth to bedrock in the wetland profiles ranged from 11 to 33 feet, with depth to bedrock at the upland points ranging from 2 to 22 feet. The surface horizons of the wetland profiles included varying depths of fibric and hemic peat (1 to 9 ft in depth) overlying mineral soil. The mineral soil textures in the profile included clay with sand, silt, sand, gravel, silty sand (or sandy loam), silty gravel and gravelly silt. The soil borings completed in the uplands (Figure 3) are characterized by mineral soil with textures including silty sand, sand with gravel, and sand with silt. Other geotechnical results for surficial deposits indicate the presence of silty sand, clay and organic soils across the Mine Site (Barr, 2006b).

Because of the lack of interaction between the surficial and bedrock aquifers, the hydrology of the wetlands at the site is primarily supported by direct precipitation and subsurface flow from the relatively small watershed areas with shallow local ground water flow making up a more variable component. Net precipitation (precipitation minus evapotranspiration) is positive for the Partridge River watershed since evapotranspiration is low, which is typical for northern Minnesota due to the cooler climates and a shorter growing season. Lateral subsurface flow within peatland soils on extensive flat peatlands is typically very slow to negligible. Surface runoff from these flat peatlands is also generally negligible except during snowmelt, due to the high water-holding capacity of the peat, the flat slopes, and the surface roughness. Surface runoff from the upland areas to the wetlands is not prevalent due to the loamy soils and healthy forest soil structure, which facilitates infiltration. As indicated in the USFS Ecological Classification System, the upland soils yield water to the lower landscape positions mainly through local groundwater flow.

5.4 Wetland Hydrology The wetland hydrology data obtained from 2005-2009 represents pre-project conditions. The water level data and the water elevation data, shown in relation to the ground surface and the cumulative precipitation during the past 30 days, are displayed graphically for 2005-2009 in Figures 6-12. The

monitoring data for 2005 and 2006 were previously described in the 2005 Preliminary Wetland Hydrology Study Report (Barr, 2006a) and the Wetland Hydrology Study Report 2006 (Barr, 2006b). The sources of water supporting the wetland hydrology in these areas are described in the impact evaluation study entitled Indirect Wetland Impacts at the Mine Site (Barr, 2008a).

The 2006-2009 data is provided in Appendices A, B, C, and D, respectively. Photographs of each well location are provided in Appendix E. The data for the wells in similar areas of the site are grouped together on each figure. The areas presented include:

1. Northwest Mine Site area including Wells 4, 4A, 5, and 18 (Figure 6).

2. North-central Mine Site area including Wells 2, 10, 11, and 12 (Figure 7).

3. Northeast Mine Site area including Wells 13, 14, and 15 (Figure 8).

4. South-central Mine Site area including Wells 1, 8, 9, 16, 21, and 22 (Figure 9).

5. Southwest Mine Site area including Wells 3, 6, 7, 17, 19 (Figure 10).

6. West of the site, in wetlands located outside of the proposed Mine Site area including reference Wells Ref1 and Ref2 (Figure 11).

5.4.1 General Observations

The monitoring data obtained from 2005-2009 show the presence of wetland hydrology in all wetlands. Continuous water level recording wells were monitored at well locations 1, 4, 7, and 12 from 2006 through 2009 (Well 1 was relocated within the same wetland complex at the beginning of the 2008 monitoring period), with 19 additional recording wells installed in April 2008, including the establishment of monitoring in two reference wetlands. While the recording well data is helpful in understanding the response of wetland hydrology to specific precipitation events at the Mine Site, it is not necessary for documenting whether or not jurisdictional wetland hydrology is present, since it is clearly present in all wetlands monitored.

Figures 6-11 show the range of depth to water over the 2005-2009 monitoring period. The wells located in the south-central and southwest areas of the Mine Site show the greatest range of water level fluctuations (Figures 9 and 10). The wells in the northwest area show the least fluctuation (Figure 7). Water levels in all wells except 4, 4A, and 5 in the northwest part of the Mine Site dropped below the wetland threshold during the July through August drought period in both 2007 and

2008. In addition, Wells 3 and 9 did not drop below the wetland threshold in 2007 and 2007-2008, respectively. Several wells were dry for up to one month during the drought period in 2007 (1, 6, 8, 10, 11, 18, 13, 14, 15, and 19). The water levels in the northwest wells (3, 4, 4A, 5, and 17) decreased 9 to 10 inches during those periods, but maintained water levels within 12 inches of the ground surface. This drop in water level followed a sustained period of over two months with precipitation well below the normal range (Figure 5). Water levels in all wells recovered quickly with over 12 inches of precipitation in early September 2007.

The monitoring data indicate that the hydroperiod remained stable (water levels fluctuating less than 12 inches) within two wetlands throughout the 2006-2009 monitoring period, including Wetland 58 (Well 9R) and Wetland 114 (Well 4M and 5M) (Table 2). The maximum water level fluctuation was between 12 inches and 18 inches during the 2005-2009 monitoring period in Wetland 48 (Wells 1M, 21R, 22M), Wetland 53 (Well 7M, 7R), Wetland 90 (Wells 14M, 14R, 16R), Wetland 83 (Well 15M), Wetland 100 (Wells 2M, 2R, 10R, 11M, 11R, 12M, 12R, 18R), Wetland 103 (Well 3M, 17M), Wetland 114 (Wells 4AM, 4AR), and the wetland with Reference Well Ref1.

The climatic conditions during the last five years include 2 years with annual precipitation within the normal range and 3 years with annual precipitation below the normal range (Table 3). The wetland hydrology monitoring data provided on the figures in Appendices A-D are shown in relation to the cumulative precipitation during the past 30 days. The 30-day cumulative precipitation is also shown in comparison to the long-term range of normal 30-day precipitation. These data provide valuable insight into the observed wetland hydrology because the majority of the monitored wetlands are supported primarily by precipitation. The influence of precipitation on wetland hydrology is typically shown on the graphs as a sharp increase in the rising leg of the hydrograph in response to a precipitation event. In contrast, the influence of groundwater on wetland hydrology is typically shown as a gradual increase in the water table or a gradual sustained water table over longer time periods (such as weeks or months).

The wetland hydrology observed at the Mine Site appears to be indicative of a system primarily supported by precipitation that is sensitive to climatic fluctuations. Water elevations in all wells fluctuated in direct response to precipitation events with the exception of Well 9 in 2008-2009 and Well 7 in 2009. Other than the prolonged drought period in July-August 2007, Wells 9 and 7 showed stability indicative of contributing discharge from upstream watershed wetlands and groundwater discharge. Precipitation patterns during 2005-2009 were highly variable as discussed in Section 3.3.

5.4.2 Northwest Mine Site Area

Wetland 114 (Wells 4, 4A, 5) and Wetland 100 (Well 18) are located in the northwest area of the Mine Site, northwest of the proposed northwest Category 1 stockpile (Figure 2). These wetlands are located north of the surface water divide, with groundwater moving to the north and into One Hundred Mile Swamp. Wetland 114 is contiguous to and on the south edge of One Hundred Mile Swamp, which provides a large contributing watershed area that helps to maintain more stable hydrology throughout this large wetland complex (Figures 3 and 4). Wetland 100 is also contiguous with One Hundred Mile Swamp, although Well 18 is located on the southern boundary (upstream edge) of the wetland; therefore it has a small watershed contributing to maintain its water level. As a result, the water level in this well exhibits greater diurnal and seasonal fluctuations in response to precipitation events compared to Wells 4, 4A, and 5. All of these wells are installed within black spruce bogs (Table 1).

The hydrographs in Figure 6 show that the water level in Wells 4, 4A, and 5 remained 7 to 13 inches higher than Well 18 throughout the 2005-2009 monitoring period, likely because of the influence of the adjacent large wetland complex (One Hundred Mile Swamp). The hydroperiod is similar for both wetlands, with an immediate increase in the water table in response to precipitation events. The water levels in Wells 4, 4A, and 5 remained about 2-13 inches higher than Well 18 throughout 2005-2009. Fluctuations in response to precipitation for recording Well 18 was generally more than 2 inches, while the response for recording Wells 4 and 4A were generally more subdued and less than 2 inches.

The range of the water table fluctuation in Wells 4, 4A, and 5 was 0.2 to 2.0 feet throughout the 2006-2009 monitoring period, which is greater than the range of water table fluctuations for Well 18 (0.9 to 2.0 ft; Table 3). In 2007, 2008, and 2009 there was a drawdown in all wells in response to a dry period during the mid- to late-summer. The water table in Well 18 dropped below the wetland threshold in all monitoring years, but by late summer to early fall the water level always rebounded to within 12 inches of the ground surface. In contrast, the water levels in Wetland 114 (Wells 4, 4A, 5) remained within 12 inches of the ground surface throughout the entire 2005-2009 monitoring period. The well data showed the presence of wetland hydrology for the majority of each growing season in Wetlands 100 and 114.

5.4.3 North-Central Mine Site Area

Wetland 100 (Wells 2, 10, 11, and 12) is located in the north-central area of the Mine Site, north of the proposed Central and East Pit areas (Figure 2). This wetland is located north of the surface water

divide, with groundwater moving to the north and into One Hundred Mile Swamp. The north boundary of the watershed for this wetland is Yelp Creek and the Partridge River. The wells are installed within black spruce bogs (Table 1).

The hydrographs in Figure 7 show that the water level in Wells 2, 10, 11, and 12 exhibit a similar response to precipitation events as Well 18, which is also located in Wetland 100. The wells indicate the wetland is generally saturated to the surface, with the data showing brief periods of inundation during the 2005 monitoring period. In response to dry climatic conditions, the water levels in all wells generally dropped below the wetland threshold between mid-June to mid-July 2006, early- to mid-July 2007, early- to mid-August 2008, and early- to mid-September 2009. In 2006, Wells 2, 10, and 11 remained below the wetland threshold for the remainder of the growing season, with only Well 12 rebounding above the wetland threshold by late-July. In 2007, all wells rebounded above the wetland threshold by early September after 1.5 inches of rainfall over a 6-day period. In 2008, the water level in all wells increased abruptly with 0.75 inches of rainfall in a 2-day period, with only the water level in Well 2 remaining above the wetland threshold the remainder of the monitoring period. The other wells recovered to above the wetland threshold by early- to mid-September after multiple rainfall events occurring over a 2-week period. In 2009, the water levels in Wells 2 and 12 were above the wetland threshold by late September, while Wells 10 and 11 took longer to rise and stay above the wetland threshold (3-4 weeks). All of these wells generally responded immediately (within the same day) to rainfall events and showed an immediate response to all rainfall events, which indicates the wetland hydrology is primarily supported by precipitation.

The range of water table fluctuations in Wells 2, 10, 11, and 12 was 0.6 to 1.5 feet throughout the 2006-2009 monitoring period, which is similar to the range of water table fluctuations for Well 18 (0.9 to 2.0 ft; Table 3). The water levels in Wells 2, 10, 11, and 12 remained about 2-12 inches lower than Well 18 throughout the growing season. The water table response to precipitation for Wells 2, 10, 11, and 12 was generally more subdued than Well 18, with water table responses generally less than 2 inches. The well data showed the presence of wetland hydrology for the majority of each growing season in Wetland 100.

5.4.4 Northeast Mine Site Area

Wetland 83 (Well 15), Wetland 84 (Well 13), and Wetland 90 (Well 14) are located east of the two proposed east Category 1 stockpiles (Figure 2). Wetland 83 is located south of the surface water divide, with groundwater moving east towards the Partridge River. Wetlands 84 and 90 are located north of the surface water divide, with groundwater moving to the east/northeast towards the

Partridge River. Well 15 is installed at the downstream and east end of an open bog, while Wells 13 and 14 are installed in black spruce bogs (Table 1).

The hydrographs in Figure 8 show that the water level in Wells 13, 14, and 15 exhibit similar responses to precipitation events as Wells 2, 10, 11, 12, and 18, which are also located in black spruce bogs. The water table in Wells 13, 14, and 15 was generally slightly lower than in Wells 2, 10, 11, 12, and 18 during 2008-2009. The well data indicates that wetlands 83, 84, and 85 are generally saturated to the surface, with only one period of inundation in Well 15 after 2.8 inches of rainfall on June 5-6, 2008.

The range of the water table fluctuation in Wells 13, 14, and 15 was 0.4 to 1.9 feet throughout the 2006-2009 monitoring period, which is similar to the range of water table fluctuations for Wells 2, 10, 11, 12, and 18 (0.6 to 2.0 ft; Table 3). Each year from 2006-2009, there was drawdown in Wells 13, 14, and 15 in response to the dry periods during the mid- to late-summer. All wells eventually rebounded to above the wetland threshold during the growing season, with the exception of Well 14 in 2006. The well data showed the presence of wetland hydrology for the majority of each growing season in wetlands 83, 84, and 90.

5.4.5 South-Central Mine Site Area

Wetland 90 (Well 16) and Wetland 48 (Wells 1, 21, 22) are located south of the proposed East and Central Pit areas, Wetland 106 (Well 8) is located south of the proposed lean ore surge pile, and Wetland 58 (Well 9) is located south of the proposed Category 4 stockpile (Figure 2). All the wells are located south of the surface water divide, with Wells 8 and 9 located south of Dunka Road. Well 1 was located in a cedar swamp during 2005-2007; this well was moved in 2008 to a coniferous bog community dominated by tamarack when it was determined that the original location was in an area directly impacted by the proposed haul roads. Well 22 is located in a coniferous bog dominated by tamarack, Wells 8, 16, and 21 are installed in black spruce bogs, and Well 9 is located in an alder thicket (Table 1). Wetland 106 (Well 8) was previously logged. North of Well 9 and Dunka Road, Wetland 8 is impounded with a continuous stream of water flowing south under Dunka Road and the railroad, through Wetland 10, and discharging into Wetland 58 (Well 9).

The hydrographs in Figure 9 show that the water level in Wells 8, 16, and 21 exhibit a similar response to precipitation events as other wells located in black spruce bogs (Wells 2, 10, 11, 12, 13, 14, and 18). The hydrographs for Wells 1 and 22 also exhibit a similar response to the wells located in black spruce bogs. Well 1 was located in a cedar swamp in 2005-2007 and relocated further east in

the same wetland complex to a black spruce bog (Figures 2 and 3). The hydrograph for Well 2 exhibited a similar pattern throughout the 2005-2009 monitoring periods (Figure 13). The water table in Wells 1, 16, 21, and 22 was generally 2 to 8 inches higher than in wetlands 84, 90, and 100 (Wells 2, 10, 11, 12, 13, 14, and 18) throughout the 2006-2009 monitoring period. While the hydrograph for Well 8 is similar to the other wells in black spruce bogs, the water table drawdown during the dry period in August 2008 was at least 10 inches greater. In 2007 and 2008, Well 8 also exhibited higher and lower water levels during the same time periods when compared to the other wells in black spruce bogs. The hydrograph for Well 9 was similar to Wells 8, 16, and 21 in 2006 and 2007. After 2007, the water levels in the wetlands upstream from Wetland 58 (Well 9) have been observed to be inundated year-round with surface water crossing Dunka Road periodically. The constant discharge to Wetland 58 may contribute to the stable water levels recorded for Well 9 in 2008 and 2009. The well data indicates that wetlands 48 and 90 are generally saturated to the surface, with inundated conditions in early June 2006, late September/early October 2007, and early June 2008.

The range of the water table fluctuation in Wells 16 and 21 was 0.4 to 2.8 feet throughout the 2006- 2009 monitoring period, which is similar to the range of water table fluctuations for the other wells located in black spruce bogs (0.6 to 2.0 ft). Well 8 is located in a logged black spruce bog and shows a greater range of the water table fluctuation (0.9 to 2.6 feet; Table 3) than the non-logged black spruce bogs. The range of water table fluctuation in Well 9 was 0.2 to 2.0 feet, with a range of only 0.2 to 0.3 feet in 2008 and 2009 because of sustained water levels. In 2006-2009 all wells (except Well 9 in 2008 and 2009) showed a drawdown in water levels in response to dry periods during the mid- to late-summer. All wells eventually rebounded to above the wetland threshold during the growing season. Water levels in Wetland 48, 90, and 101 fell below the wetland threshold periodically in 2007-2009; however, the threshold for wetland hydrology is met each year. The well data showed the presence of wetland hydrology for the majority of each growing season in wetlands 48, 90, and 106.

5.4.6 Southwest Mine Site Area

Wetland 103 (Wells 3, 17), Wetland 53 (Well 7), Wetland 54 (Well 6), and Wetland 15 (Well 19) are located within, south, or southwest of the proposed West Pit (Figure 2). Wells 3 and 17 were monitored from 2005-2007; these wells were removed after 2007 since it was determined that they would be directly impacted by the project. Wells 22 and 3 was installed in a coniferous bog dominated by black spruce. Well 17 was located in a black spruce bog with interspersed areas of alder that also had an understory of sphagnum mat and Labrador tea. Wells 6 and 7 are located in

alder thickets, and Well 19 is located in a coniferous bog dominated by black spruce and tamarack (Table 1).

In 2006 and 2007, the hydrographs in Figure 10 show that the water levels in Wells 3, 6, 7, 17, and 19 exhibit a response similar to precipitation events, even though these wells are not all located within the same wetland types. Wells 3 and 17 are located in the same wetland complex and have nearly identical hydrographs. All wells generally respond immediately to precipitation events and this type of hydrograph indicates the wetlands are primarily supported by precipitation. Wells 6 and 19 terminate in sand and as a result, capillarity is reduced so the water table drops quickly with a decrease in precipitation compared to wells installed in soils with higher capillarity or water-holding capacity (e.g., organic soil). With the extended drought in July-September 2007, the water level in all wells except Well 3 decreased below the wetland threshold. The water level in all wells began to increase in late August-early September with 1.8 inches of rainfall (August 28 and September 4). Water tables continued to rise and were maintained near or above the ground surface after an 8-inch rainfall event on September 10.

In 2008 and 2009, the hydrographs show that the water levels in Wells 6 and 19 exhibit a response similar to precipitation events, even though these wells are located within different wetland types. All wells generally respond immediately to precipitation events, although the responses are more subdued for Well 7 than in 2006 and 2007. Well 7 fluctuated more in 2006 (1.5 ft) and 2007 (1.2 ft) than in 2008 (1.1 ft) and 2009 (0.6 ft; Table 3). Just as in 2006 and 2007, Wells 6 and 19 generally exhibited the lowest water elevations in 2008 and 2009. The water level in Wells 6 and 18 dropped below the wetland threshold in 2008 and 2009; however in 2008 the water levels rebounded within 6 inches below the ground surface from September-November. In 2008-2009, only Well 7 remained with 6 inches of the ground surface during the entire monitoring period.

The range of water table fluctuations for the wells in alder thickets (Wells 6, 7) was 0.3 to 2.9 feet throughout the 2006-2009 monitoring period, which is similar to the range of water table fluctuations for Reference Well Ref2 (0.4 to 3.1 ft; Table 3), which is also located in an alder thicket. The hydrographs for Wells 6 and 7 are similar except in the pronounced drawdown during drought periods. The drawdown is more pronounced in Well 6, located in Wetland 54, which is isolated compared to Wetland 53 (Well 7) which has a larger contributing watershed area. Wells 3 and 17 were located in black spruce bogs with the range of water table fluctuation (0.7 to 1.2 ft; Table 3) similar to the other wells in black spruce bogs (0.6 to 2.0 ft). The water table fluctuation was 0.3 to 1.0 feet for Reference Well Ref1, which is also located in a black spruce bog. Well 19 is located in a

black spruce bog, but the range of fluctuation was greater (0.6 to 2.6 ft; Table 3) compared to all other wells located in black spruce bogs, this could be partially due to the fact that Well 19 is located near the upstream end of the wetland. All wells showed a drawdown in response to dry periods in mid- to late-summer each year. All wells eventually rebounded above the wetland threshold before the end of the growing season. In 2007-2009, the water levels in most wells were near or above the ground surface except during the drier portions of the year (mid-summer to early-fall). The well data showed the presence of wetland hydrology for the majority of each growing season for wetlands 15, 48, 54, and 103.

5.4.7 Reference Wetlands

Reference Wells Ref1 and Ref2 were installed in April 2008 in wetlands (no identification numbers) located west of the Mine Site (Figure 2). Reference Well Ref1 is installed within a black spruce bog, with an area of cedar located nearby to the west. Reference Well Ref2 is installed in an alder thicket surrounded by a conifer swamp, which is dominated by black spruce and tamarack trees (Table 1).

The hydrographs in Figure 11 show that the water table in Reference Well Ref1 was within 2 inches of the ground surface for most of 2008, dropping to a depth of 11 inches during the drought period from August 3 to September 11. In 2008, Reference Well Ref2 was inundated with up to 7 inches of water, with the exception of August 9 through September 12 when the water table fell below the ground surface. On August 27, 2008 the water table was at more than 17 inches below the ground surface, and after 0.75 inches of rainfall in a 2-day period (August 28-29), the water table rebounded and remained above the ground surface for the remainder of 2008. In 2009, the reference wells exhibited wetland hydrology for the entire monitoring period. Similar to most of the wetlands monitored, the reference wells exhibited a slight decrease in water levels in response to the dry period in late July and August, 2009. The reference wells hydrographs reflect the different climate conditions present in 2008 and 2009.

The water table fluctuation for the reference Wells Ref1 and Ref2 in 2008 was 1.0 and 3.1 feet, respectively (Table 3). In comparison, with a majority of the growing season within the normal range of precipitation in 2009, the range of fluctuation for reference Wells Ref1 and Ref2 was very stable with 0.3 feet and 0.4 feet, respectively. The reference well data showed the presence of wetland hydrology for the majority of each growing season in the reference wetlands.

5.5 Wetland Hydrology Elevations The average water level elevations recorded in the wetland monitoring wells in 2006-2009, along with the ground elevations at each well, are shown spatially on the figures in Appendices A-D, respectively. The water level elevation data is also shown graphically by project area on the figures in Appendices A-D. The wetland water level elevations are provided in Tables 2 and 3 and Figures 2 and 3.

The average water level elevations for each wetland type from 2005-2009 show the long term hydrologic stability despite varying climatic conditions (Appendix I). Throughout 2007-2009, the lowest average wetland water elevation was at Well 7M, located south of Dunka Road, with values ranging from 1557.4-1558.4 ft. MSL (Figures 3 and 4). The highest average wetland water elevation was at Well 4R, located in the northwest corner of the Mine Site, with values ranging from to 1614.7- 1616.1 ft. MSL. The water table gradient throughout the site is very flat, ranging from 0.05 percent to 1.2 percent. The steepest gradient (1.2 percent in 2007-2009) is observed at the edges of the Mine Site and includes transects: between Wells 2 and 12, near the Partridge River; between Wells 19 and 7, in the southwest area; and between Wells 21 and 8. In the headwaters of the Partridge River, between Wells 4 and 4A, the water gradient during 2007-2009 was 0.6 percent, sloped to the northeast. One Hundred Mile Swamp is an extensive flat peatland with an average slope of about 0.2 percent from west to east. The average water table slope between Wells 2, 11, and 18 is about 0.1 percent. In 2007, the average water table slope between Wells 3, 7, 17, and 19 is about 0.8 percent sloping downward to the south (Wells 3 and 17 were removed at the beginning of the 2008 monitoring period).

5.6 Hydrology Results Summary The monitoring data obtained in 2005-2009 shows the presence of sustained wetland hydrology (within 12 inches of the ground surface) in all of the monitored wetlands throughout 2005-2009 (Figures 6-11). Water levels in all wells except the Wells 4, 4A, and 5 in the northwest part of the Mine Site dropped below the wetland threshold during the July through August drought period in both 2007 and 2008. Several wells throughout the Mine Site were dry for up to one month during the drought period in 2007 (6, 19, 10, 11, 18, 1, 8, 13, 14, and 15). The water levels in the northwest wells (3, 4, 4A, 5, and 17) decreased 9 to 10 inches, but maintained water levels within 12 inches of the ground surface. This drop in water levels followed a sustained period of over two months with precipitation well below the normal range. Water levels in all wells recovered quickly with over 12 inches of precipitation in early September 2007.

Figures 6-11 show the range of depth to water over the five-year monitoring period. The wells located in the southwest and south-central areas of the Mine Site show the greatest range of water levels. The wells in the northwest area, located in Hundred Mile Swamp, show the least fluctuation. Continuous water level recording wells were monitored at well locations 1, 4, 7, and 12 from 2006- 2009 (Well 1 was relocated at the beginning of the 2008 monitoring period), with additional wells installed in April 2008. Water levels were recorded once every 2 hours during the 2006-2009 monitoring period. While the recording well data is helpful in understanding the response of wetland hydrology to specific storm events at the Mine Site, it is not necessary for documenting whether or not jurisdictional wetland hydrology is present, since it is clearly present in all wetlands monitored. The recording well data for Wells 4R and 12R, located within the Hundred Mile Swamp complex, indicates very stable hydrology, which is indicative of a large, headwater wetland complex.

On average, wetlands make up 43 percent of the watershed areas within the Mine Site. Within the detailed watersheds shown on Figure 2, wetlands make up 32 percent to 56 percent of the land area within each watershed. The wetland hydrology observed at the Mine Site appears to be indicative of a system primarily supported by precipitation that is sensitive to climatic fluctuations. Precipitation patterns during 2005-2009 were highly variable as discussed in Section 3.3. The large fluctuations in water levels exhibited within the majority of the wetlands are indicative of wetlands supported primarily by precipitation and local surface runoff. The scrub shrub wetlands located near the downstream portion of the project generally show more stable hydrologic regimes due to the upstream contributions and some groundwater component. Without the support of regional ground water systems, the hydrology of these wetlands tends to fluctuate in a pattern that closely mirrors the climatic conditions.

6.0 Future Actions

The wetland hydrology monitoring will continue in 2010 on a monthly basis from approximately early May through late October. A plan to install wetland monitoring wells near the tailings basin is currently under development along with potential modifications to the monitoring plan at the Mine Site. This updated plan will be submitted in March of 2010, with wetland hydrology monitoring beginning in April 2010.

8.0 References

Barr Engineering Company. 2005. Wetland Hydrology Study Plan, PolyMet Mining Inc.. June 24.

Barr Engineering Company. 2006a. 2005 Preliminary Wetland Hydrology Study Report. RS-44. PolyMet Mining Inc.. January 23.

Barr Engineering Company. 2006b. Wetland Hydrology Study Report 2006. RS-44 Draft 02. PolyMet Mining Inc.. November 20.

Barr Engineering Company. 2007. Phase III Hydrogeologic Investigation. PolyMet Mining Inc.. March.

Barr Engineering Company. 2008a. Indirect Wetland Impacts at the Mine Site. Technical Memorandum Submitted to the USACE and MnDNR. June 2.

Barr Engineering Company. 2008b. RS22 Appendix B Groundwater Modeling of the NorthMet Mine Site.” Draft 03, August.

Nichols, D.S. and J.M. Brown. 1980. Evaporation from a sphagnum moss surface. Journal of Hydrology 48:289-302.

Siegle, D.I. and D.W. Ericson. 1980. Hydrology and water quality of the copper-nickel study region, Northeastern Minnesota. U.S. Geological Survey, Water-Resources Investigations, 80-739.

Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Official Soil Series Descriptions. http://soils.usda.gov/technical/classification/osd/index.html. Accessed 10 February 2008. USDA-NRCS, Lincoln, NE.

U.S. Army Corps of Engineers. 1987. Army Corps of Engineers 1987 Wetland Delineation Manual (1987 Manual).

U.S. Army Corps of Engineers. 2005. Technical Standard for Water-Table Monitoring of Potential Wetland Sites. ERDC TN-WRAP-05-2, June.

U.S. Army Corps of Engineers. 2009. Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Northcentral and Northeast Region, ed. J. S. Wakeley, R. W. Lichvar, and C. V. Noble. ERDC/EL TR-09-19. Vicksburg, MS: U.S. Army Engineer Research and Development Center.

U. S. Department of Agriculture - United States Forest Service. 2007. Superior National Forest Ecological Classification Mapping Units.

27 Tables

Table 1 2005-2009 Wetland monitoring Well Summary PolyMet Mining Hoyt Lakes, Minnesota

2005 2006 2007 2008 2009 UTM Coordinates 2009 Average Average Average Average Average Average Average Average Average Average Top of Top of Below Depth to Water Depth to Water Depth to Water Depth to Water Depth to Water Casing to Casing Ground Well Ground Wetland Circ 39 Eggers & Reed Date Initial Water1 Elevation Water1 Elevation Water1 Elevation Water1 Elevation Water1 Elevation Ground Elevation Elevation Length Length Well ID PVC ID ID Type Wetland Type Installed (in) (ft MSL) (in) (ft MSL) (in) (ft MSL) (in) (ft MSL) (in) (ft MSL) X: Y: (in) (ft MSL) (ft MSL) (in) (in) Stratigraphy Notes Well 1M3 --- 48 7 Coniferous swamp 6/28/05 0.0 1586.4 -3.4 1586.1 -2.6 1586.2 ------577670 5273982 ------4" peat, 16" mucky peat Well 1M --- 48 8 Coniferous bog 5/22/08 ------4.3 1592.0 -1.2 1592.2 577786 5274017 7.9 1593.0 1592.3 28.0 20.1 10" fibric peat, sapric peat to depth of well Well 1R3 A3BF0FE 48 7 Coniferous swamp 11/9/05 -0.5 1586.3 -4.1 1586.1 -3.3 1587.2 ------577670 5273982 ------4" peat, 16" mucky peat Well 1R3 A3BF0FE 48 8 Coniferous bog 5/22/08 ------4.4 1592.4 -5.86 1592.2 577788 5274017 7.3 1593.3 1592.7 47.5 40.3 10" fibric peat, sapric peat to depth of well Well 2M M48-0 100 8 Coniferous bog 6/30/05 11.3 1600.7 14.5 1600.5 7.8 1601.0 -7.8 1600.8 -11.0 1600.8 578291 5275294 23.3 1603.6 1601.7 59.5 36.2 no data Well 2R 11311992 100 8 Coniferous bog 5/22/08 ------5.4 1600.8 -7.84 1600.7 578291 5275286 3.0 1601.5 1601.3 47.5 44.5 peat Well 3M2 M15-8A 103 8 Coniferous bog 6/29/05 0.4 1597.0 1.9 1596.9 2.2 1596.8 ------576018 5274075 ------no data Well 4M M15-1 114 8 Coniferous bog 6/28/05 -0.9 1615.7 -2.2 1615.4 0.6 1615.5 -0.9 1615.4 0.7 1615.4 574918 5274129 14.1 1616.5 1615.3 28.8 14.6 15" peat Well 4R4 A3BFEE6 114 8 Coniferous bog 11/9/05 -1.4 1615.5 -0.1 1615.6 -5.9 1616.1 -1.7 1615.2 -1.03 1615.5 574920 5274138 6.0 1616.0 1615.5 33.8 27.8 no data Well 4AM --- 114 8 Coniferous bog 6/29/05 2.7 1597.8 1.0 1598.0 1.5 1597.9 -0.8 1597.7 2.4 1597.9 575669 5274600 13.2 1598.8 1597.7 29.0 15.8 no data Well 4AR 1130ED9F 114 8 Coniferous bog 5/21/08 ------2.0 1597.6 1.22 1597.8 575669 5274600 8.0 1598.4 1597.7 47.5 39.5 fibric peat Well 5M M15-2 114 8 Coniferous bog 6/28/05 -1.2 1615.5 -1.4 1615.6 -0.2 1615.5 -0.8 1615.3 -1.1 1615.4 574918 5274129 12.8 1616.6 1615.5 29.0 16.3 15" peat Well 6M M48-18 54 6 Alder thicket 6/29/05 1.0 1597.8 0.3 1597.8 5.8 1597.4 -0.6 1597.9 0.0 1597.8 574794 5272347 33.4 1600.5 1597.7 59.5 26.1 3" peat, 25" fine sand Well 6R 1130E9C3 54 6 Alder thicket 5/23/08 ------5.1 1597.6 -1.87 1597.8 574794 5272347 6.3 1598.4 1597.8 47.5 41.3 end of well is in sand Well 7M M48-20 53 6 Alder thicket 6/29/05 -1.3 1558.4 2.7 1557.9 -1.5 1558.4 -1.0 1558.2 3.8 1558.2 576323 5272608 31.6 1560.5 1557.9 59.3 27.7 no data Well 7R EBDA9E2 53 6 Alder thicket 11/9/05 0.7 1557.9 3.5 1558.0 -9.6 1559.1 -2.4 1558.1 -1.61 1558.4 576312 5272607 7.5 1559.2 1558.5 29.0 21.5 no data Well 8M M48-17 106 8 Coniferous bog 6/30/05 0.1 1564.1 4.1 1563.8 6.1 1563.6 -5.0 1563.6 -4.1 1563.8 578657 5273785 31.7 1566.8 1564.2 59.3 27.5 8"peat, 12" fine muck (compacted), 8" sand Well 8R 10FACBD2 106 8 Coniferous bog 5/23/08 ------5.9 1563.7 -3.73 1563.7 578657 5273785 8.5 1564.5 1563.8 47.5 39.0 end of well is in sandy clay Well 9M M48-14 58 6 Alder thicket 6/30/05 0.1 1565.8 1.6 1565.7 1.1 1565.8 0.1 1565.5 0.9 1565.8 579257 5274041 27.9 1568.1 1565.7 59.5 31.6 14" peat, 4" muck, 10" sand Well 9R 1130E1CB 58 6 Alder thicket 6/27/08 ------1.0 1565.5 0.27 1565.7 579257 5274041 6.0 1566.2 1565.7 47.5 41.5 muck over sand Well 10M EC-1 100 8 Coniferous bog 10/25/05 12.6 1598.3 12.1 1598.4 9.8 1598.6 -11.2 1597.8 -9.9 1598.1 577169 5275313 7.0 1599.5 1598.9 28.8 21.7 mucky peat Well 10R 11312C31 100 8 Coniferous bog 5/22/08 ------6.8 1598.2 -7.88 1598.1 577165 5275315 5.2 1599.0 1598.6 47.5 42.3 fibric peat Well 11M M15-9 100 8 Coniferous bog 10/25/05 9.0 1597.4 11.6 1597.2 10.1 1597.3 -7.6 1598.3 -6.4 1598.5 577610 5274975 12.7 1600.1 1599.0 28.8 16.1 mucky peat Well 11R 1130F7A0 100 8 Coniferous bog 5/22/08 ------10.0 1598.4 -11.65 1598.4 577624 5274981 5.2 1599.7 1599.3 47.5 42.3 10" fibric peat, sapric peat to depth of well Well 12M M48-1 100 8 Coniferous bog 6/30/05 3.6 1592.4 7.1 1592.1 7.0 1592.1 -5.9 1592.1 -7.8 1591.4 578188 5275487 16.8 1593.5 1592.1 59.5 42.7 14" peat, 4" muck, 10" sand Well 12R A3C03B3 100 8 Coniferous bog 11/9/05 -0.40 1591.6 5.25 1591.2 1.02 1591.9 -8.5 1592.0 -6.66 1592.2 578180 5275483 8.5 1593.4 1592.7 33.8 25.3 no data 6" sphagnum peat, 10" mucky peat, 5" mucky Well 13M --- 84 8 Coniferous bog 6/29/05 17.5 1578.7 7.3 1579.6 8.7 1579.5 -8.0 1579.4 -7.8 1579.4 580022 5275659 9.2 1580.8 1580.1 29.0 19.8 silt loam Well 13R 113137C8 84 8 Coniferous bog 5/23/08 ------10.8 1579.2 -9.84 1579.4 580022 5275659 5.5 1580.6 1580.1 47.5 42.0 sapric peat 4" sphagnum peat, 8" black and dark brown Well 14M --- 90 8 Coniferous bog 6/29/05 13.9 1574.3 14.3 1574.3 9.5 1574.6 -6.6 1574.9 -9.6 1574.3 580480 5275406 11.2 1576.0 1575.1 29.0 17.8 muck w/silt loam, 9" reddish peat Well 14R 10FACBD4 90 8 Coniferous bog 5/23/08 ------11.8 1574.4 -12.07 1574.3 580480 5275406 4.0 1575.5 1575.1 47.5 43.5 sapric peat Well 15M --- 83 8 Coniferous bog 6/29/05 7.5 1572.2 7.5 1572.2 7.3 1572.3 -4.6 1572.0 -5.1 1572.1 580790 5274950 9.1 1573.3 1572.6 29.0 19.9 21" mucky peat w/ some sand, 2+" sand Well 15R 1131251E 83 8 Coniferous bog 5/23/08 ------4.4 1572.1 -3.56 1572.1 580790 5274950 6.0 1572.8 1572.3 47.5 41.5 end of well is in sand Well 16M M48-12 90 8 Coniferous bog 6/30/05 3.9 1586.2 3.6 1586.2 2.9 1586.3 -5.1 1586.3 -5.8 1586.0 579201 5274883 28.3 1588.8 1586.5 59.8 31.5 no data Well 16R 1130EA23 90 8 Coniferous bog 5/22/08 ------4.4 1585.8 -4.18 1586.0 579199 5274883 5.4 1586.7 1586.3 47.5 42.1 fibric peat Well 17M2 M15-8 103 8 Coniferous bog 6/29/05 1.8 1599.2 3.3 1599.1 3.5 1599.1 ------575812 5273791 ------no data Well 18M EC-2 100 8 Coniferous bog 10/25/05 12.7 1595.4 11.1 1595.5 11.7 1595.4 -8.6 1595.9 -8.4 1595.8 577100 5274700 10.0 1597.4 1596.5 28.5 18.5 peat Well 18R 11312B8A 100 8 Coniferous bog 5/22/08 ------7.6 1596.0 -8.54 1595.7 577107 5274695 5.3 1596.8 1596.3 47.5 42.3 fibric peat Well 19M M48-7 15 8 Coniferous bog 6/28/05 1.8 1586.4 4.9 1586.1 5.4 1586.1 -1.0 1586.9 -1.4 1585.6 575729 5272919 31.2 1588.3 1585.7 59.7 28.5 8" peat, 18" 10YR6/1 sand Well 19R 10FAA730 15 8 Coniferous bog 5/21/08 ------4.4 1586.0 -1.08 1585.6 575721 5272927 7.0 1586.2 1585.6 47.5 40.5 20" fine sand, fine sandy clay to depth of well Well 21M --- 48 8 Coniferous bog 5/22/08 ------14.3 1589.1 -7.96 1589.6 578590 5274381 5.9 1590.7 1590.2 60.3 54.3 fibric peat Well 21R 1130F796 48 8 Coniferous bog 5/22/08 ------5.8 1589.8 -5.18 1589.5 578593 5274381 6.1 1590.4 1589.9 47.5 41.4 fibric peat Well 22M --- 48 8 Coniferous bog 5/22/08 ------9.2 1598.3 -3.93 1597.8 577270 5274216 11.4 1599.1 1598.1 41.3 29.8 10" fibric peat, 38" fine sandy clay 10" fibric peat, 18" fine sandy clay, 6" fine Well 22R 11313A5D 48 8 Coniferous bog 5/22/08 ------5.2 1598.0 -6.16 1597.9 577268 5274214 5.0 1598.7 1598.2 47.5 42.5 sandy clay loam Well Ref1M ------8 Coniferous bog 5/21/08 ------0.9 1592.7 -0.08 1592.5 573085 5272649 13.5 1593.6 1592.5 61.0 47.5 fibric peat Well Ref1R 1130EA3A --- 8 Coniferous bog 5/21/08 ------2.6 1592.5 -0.65 1592.4 573085 5272646 7.5 1593.1 1592.5 47.5 40.0 fibric peat Well Ref2M ------6 Alder thicket 5/21/08 ------3.9 1573.6 2.71 1573.6 572981 5270993 15.6 1574.7 1573.4 29.8 14.1 20" fibric peat, sapric peat to depth of well Well Ref2R 113130E8 --- 6 Alder thicket 5/21/08 ------1.6 1574.0 1.06 1573.7 572979 5270994 9.5 1574.3 1573.5 47.5 38.0 20" fibric peat, sapric peat to depth of well 1 Positive numbers represent depth below ground and negative numbers represent standing water on the ground surface. 2 Well was retired from the study after the 2007 monitoring season. 3 Well 1 was relocated in 2008. 4 Well 4R is paired with manual Wells 4 and 5. Bold = Recording wells installed 2008. "R" refers to recording wells; "M" refers to manual wells

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_2009Manualand Recording well Table Table 2 2005-2009 Water Elevation Summary PolyMet Mining Hoyt Lakes, Minnesota

Date 2005 2006 2007 2008 2009 Average Average Average Average Below- Average Water Water Water Water TOC Ground ground Water Elevation Range Elevation Range Elevation Range Elevation Range Elevation Elevation Length Elevation Range Well ID (ft MSL) n (ft) (ft MSL) n (ft) (ft MSL) n (ft) (ft MSL) n (ft) (ft MSL) (ft MSL) (in) (ft MSL) n (ft) 1M - removed 1586.4 5.0 0.2 1586.1 14.0 1.6 1586.2 14.0 2.0 ------1M ------1592.0 7.0 1.0 1593.0 1592.3 20.1 1592.2 6.0 0.8 1R - removed 1586.3 2.0 0.3 1586.1 14.0 2.0 1587.2 13.0 2.0 ------1R ------1592.4 --- 1.8 1593.3 1592.7 40.3 1592.2 --- 1.2 2M 1600.7 6.0 0.5 1600.5 14.0 0.9 1601.0 15.0 1.4 1600.8 7.0 1.5 1603.6 1601.7 36.2 1600.8 6.0 0.6 2R ------1600.8 --- 1.2 1601.5 1601.3 44.5 1600.7 --- 0.7 3M - removed 1597.0 4.0 0.1 1596.9 14.0 0.7 1596.8 14.0 1.1 ------4M 1615.7 6.0 0.3 1615.4 13.0 0.7 1615.5 14.0 0.9 1615.4 5.0 0.0 1616.5 1615.3 14.6 1615.4 6.0 0.5 4R 1615.5 2.0 0.1 1615.6 1.0 1.9 1616.1 14.0 1.4 1615.2 --- 0.9 1616.0 1615.5 27.8 1615.5 --- 0.3 4AM 1597.8 5.0 0.1 1598.0 14.0 0.6 1597.9 14.0 1.2 1597.7 6.0 0.4 1598.8 1597.7 15.8 1597.9 6.0 0.8 4AR ------1597.6 --- 1.0 1598.4 1597.7 39.5 1597.8 --- 0.4 5M 1615.5 6.0 0.3 1615.6 14.0 0.6 1615.5 14.0 0.8 1615.3 5.0 0.2 1616.6 1615.5 16.3 1615.4 6.0 0.3 6M 1597.8 4.0 0.4 1597.8 14.0 1.3 1597.4 14.0 2.7 1597.9 4.0 0.4 1600.5 1597.7 26.1 1597.8 6.0 1.9 6R ------1597.6 --- 2.9 1598.4 1597.8 41.3 1597.8 --- 0.8 7M 1558.4 4.0 0.2 1558.0 14.0 1.2 1558.4 14.0 1.6 1558.2 5.0 0.3 1560.5 1557.9 27.7 1558.2 6.0 0.8 7R 1557.9 2.0 0.1 1557.9 --- 0.3 1559.1 14.0 1.2 1558.1 --- 1.1 1559.2 1558.5 21.5 1558.4 --- 0.6 8M 1564.1 6.0 0.4 1563.8 14.0 0.9 1563.6 14.0 2.6 1563.6 5.0 1.3 1566.8 1564.2 27.5 1563.8 6.0 1.1 8R ------1563.7 --- 2.5 1564.5 1563.8 39.0 1563.7 --- 1.5 9M 1565.8 6.0 0.2 1565.7 14.0 0.8 1565.8 15.0 2.0 1565.5 6.0 0.5 1568.1 1565.7 31.6 1565.8 6.0 0.3 9R ------1565.5 --- 0.3 1566.2 1565.7 41.5 1565.7 --- 0.2 10M 1598.3 4.0 0.9 1598.4 14.0 0.8 1598.6 14.0 1.6 1597.8 6.0 1.1 1599.5 1598.9 21.7 1598.1 6.0 1.1 10R ------1598.2 --- 1.3 1599.0 1598.6 42.3 1598.1 --- 0.7 11M 1597.4 4.0 0.4 1597.2 14.0 0.9 1597.3 14.0 1.1 1598.3 6.0 1.0 1600.1 1599.0 16.1 1598.5 6.0 1.3 11R ------1598.4 --- 1.5 1599.7 1599.3 42.3 1598.4 --- 0.6 12M 1592.4 5.0 0.4 1592.1 14.0 1.0 1592.1 15.0 1.3 1592.1 7.0 1.1 1593.5 1592.1 42.7 1591.4 6.0 0.6 12R 1591.6 1.0 0.0 1591.2 2.0 0.6 1591.9 14.0 1.5 1592.0 --- 1.4 1593.4 1592.7 25.3 1592.2 --- 0.8 13M 1578.7 6.0 0.7 1579.6 8.0 0.4 1579.5 14.0 1.6 1579.4 6.0 1.2 1580.8 1580.1 19.8 1579.4 6.0 1.3 13R ------1579.2 --- 1.8 1580.6 1580.1 42.0 1579.4 --- 1.1 14M 1574.3 6.0 0.9 1574.3 14.0 1.0 1574.6 14.0 1.5 1574.9 7.0 0.6 1576.0 1575.1 17.8 1574.3 6.0 1.1 14R ------1574.4 --- 1.5 1575.5 1575.1 43.5 1574.3 --- 0.9 15M 1572.2 6.0 0.2 1572.2 14.0 0.7 1572.3 14.0 1.5 1572.0 7.0 0.9 1573.3 1572.6 19.9 1572.1 6.0 1.1 15R ------1572.1 --- 1.9 1572.8 1572.3 41.5 1572.1 --- 0.6 16M 1586.2 6.0 0.4 1586.2 14.0 0.7 1586.3 15.0 1.4 1586.3 7.0 1.7 1588.8 1586.5 31.5 1586.0 6.0 1.3 16R ------1585.8 --- 1.3 1586.7 1586.3 42.1 1586.0 --- 0.7 17M - removed 1599.2 4.0 0.2 1599.1 14.0 0.9 1599.1 14.0 1.2 ------18M 1595.4 4.0 1.2 1595.5 14.0 1.0 1595.4 13.0 2.0 1595.9 7.0 1.3 1597.4 1596.5 18.5 1595.8 6.0 1.2 18R ------1596.0 --- 1.3 1596.8 1596.3 42.3 1595.7 --- 0.9 19M 1586.4 7.0 0.4 1586.1 14.0 1.3 1586.1 14.0 2.6 1586.9 7.0 0.8 1588.3 1585.7 28.5 1585.6 --- 1.0 19R ------1586.0 --- 2.3 1586.2 1585.6 40.5 1585.6 --- 0.6 21M ------1589.1 6.0 2.8 1590.7 1590.2 54.3 1589.6 6.0 0.4 21R ------1589.8 --- 1.3 1590.4 1589.9 41.4 1589.5 --- 0.6 22M ------1598.3 5.0 1.5 1599.1 1598.1 29.8 1597.8 --- 1.4 22R ------1598.0 --- 2.2 1598.7 1598.2 42.5 1597.9 --- 0.9 Ref1M ------1592.7 5.0 1.4 1593.6 1592.5 47.5 1592.5 6.0 0.4 Ref1R ------1592.5 --- 1.0 1593.1 1592.5 40.0 1592.4 --- 0.3 Ref2M ------1573.6 5.0 3.1 1574.7 1573.4 14.1 1573.6 6.0 1.2 Ref2R ------1574.0 --- 2.1 1574.3 1573.5 38.0 1573.7 --- 0.4 "R" refers to recording wells; "M" refers to manual wells

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_20092009 Elev_table Table 3 Precipitation Summary Compared to WETS Data 1999-2009 PolyMet Mining Company Hoyt Lakes, Minnesota

30% chance Babbitt Average less than more than 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Inches January 0.88 0.52 1.07 0.73 0.55 1.21 0.12 0.19 1.23 2.15 0.42 1.56 0.69 1.09 February 0.70 0.36 0.86 0.60 0.71 1.77 0.26 0.44 0.23 0.50 0.88 0.34 0.17 1.13 March 1.10 0.63 1.34 1.01 1.11 0.22 0.96 0.82 0.64 0.95 1.69 2.39 0.33 2.81 April 1.96 1.27 2.35 1.70 0.94 5.07 0.47 1.56 1.63 1.91 1.82 3.56 4.46 3.36 May 3.01 1.89 3.63 5.13 3.65 6.69 1.72 2.16 4.53 9.01 3.35 4.31 2.77 1.54 June 4.29 3.26 5.00 3.96 5.89 3.79 4.28 3.36 1.45 5.78 1.71 4.88 5.58 2.30 July 3.37 2.44 3.96 13.51 4.08 4.91 5.13 5.51 3.23 1.42 4.92 1.22 1.31 2.38 August 3.94 2.73 4.70 4.91 5.14 9.59 4.90 1.90 3.01 1.77 2.10 1.05 1.07 3.56 September 3.65 2.44 4.36 5.33 2.23 1.41 3.74 5.42 4.04 2.79 2.13 12.75 4.87 1.12 October 2.88 1.77 3.48 1.48 2.34 4.07 2.16 1.50 3.08 2.78 1.98 6.43 2.28 3.08 November 1.75 1.00 2.13 0.09 1.33 2.02 0.29 1.49 0.34 3.44 0.82 0.77 0.75 1.45 December 1.07 0.74 1.27 0.19 0.81 0.67 0.50 0.88 1.96 0.90 1.03 2.21 1.92 1.38 Annual 28.60 25.96 30.86 38.64 28.78 41.42 24.53 25.23 25.37 33.40 22.85 41.47 26.20 25.20 Water Year 26.06 39.14 28.34 24.31 23.86 31.66 26.14 35.89 30.66 24.24 The only normal period available for Babbitt is 1961-1985, which is the basis of the data above. All data is from Babbitt weather station except box shaded gray, which is from Embarrass weather station. Bold = above the normal range Italics = below the normal range

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_2009.xlsTable 3-BabbittWETS Table 4 Precipitation During the Growing Season (May 9-October 6; 151 days) 2005-2009 PolyMet Mining Company Hoyt Lakes, Minnesota

Year 2005 2006 2007 2008 2009 Days Below Normal Range 35 74 69 68 35 (percent of total days) (23%) (49%) (46%) (45%) (23%)

Days Within Normal Range 57 57 15 27 114 (percent of total days) (39%) (38%) (10%) (18%) (76%)

Days Above Normal Range 59 20 67 56 2 (percent of total days) (38%) (13%) (44%) (37%) (1%)

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_2009.xlsTable 4 Figures

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B k e e Mine Site r USFS Soils Data Monitoring Well Status ranch C B Pa uth rt s So r i g Ecological Land Types !( d e Wells - Removed/Relocated Proposed Project Arleas g t e e R i W ELT 1 - Lowland Loamy Moist (LLM) !( Wells - Existing v Detailed Watersheds e r Figure 2 Surface Water Drainage Divide ELT 2 - Lowland Loamy Wet (LLW) I MINE SITE OVERVIEW Streams ELT 6 - Lowland Organic Acid to Neutral (LPN) 2,000 1,000 0 2,000 PolyMet Mining ELT 16 - Upland Shallow Loamy Dry (USLD) Hoyt Lakes, Minnesota Dunka Road Feet Railroads Not Mapped 273 225 274 228 219 275 226 220 er 222 e Riv 227 218 203 224 g 223 id r 100A rt Well 13 a 294 531 P 221 1580.2 534 530 Well 12 523 1578.7 756 535 1592.7 217 1579.6 295 529 528 524 Well 12R 1592.4 216 755 1592.7 84A 1579.5 Well 14 601 1592.1 2 608 1591.6 508!( 1575.5 281 m r Well 10 1592.1 84 520 a 519 1574.3

532 1591.2 611 : 600 r 1599.4 72 e !( 521 1574.3 266 s 525 1591.9 Well 2 280

U 1598.3 753 44 !( 1574.6 d 533 1601.7 x 516 1598.4 610 m . 527 !( !( 1600.7 609 g 620 536 7627 24 522 282 283 n 1598.6 Well 11 i r 526 1600.5 517 511510 o t i 593 eek 1598.1 267 n 621 Cr 1601.0 Well 15 o 595 602 591 elp 90 M 746 1597.4 745 Y 85 Well 16 1572.8 d 594 100 95 515 n 592 754 1597.2 a 590 !( 1586.5 83 l Well 18 t !( 1572.2 e Well 4A 1597.3 !( 1586.2 34 W 751 1596.4 1572.2 588 7 1598.1 37 90A 0 1595.4 1586.2 285 271

0 1572.3

2 589 1597.8 100 33 _ 587 1595.4 !( 1586.3 29 293 5 Well 5 0 1598.0 509 0 1595.5 77 2 !( 1615.5 767 78 43 3 698747 1597.9 68 202 55 e r 1615.5 Well 4R 98 3 292 u g i 752 97 287 F 1615.6 1615.6 201 1 288 \ 202 289 s Well 3 99 6 p 1615.5 101 7 290 a 1615.5 96 12A m 1597.0 Well 1 Well 1R 11 _ t 1615.6 Well 9 r Well 4 48 8 291 o 1597.0 1586.4 1586.4 p !( 1616.1 1565.9 e 1615.6 !( 18 10 500 284 R 200 !( 1596.9 1586.4 1586.3 _ 750 !( 1565.8 9 1615.7

0 103 1596.8 1586.1 1587.1 0 !( 1565.7 2 1615.4 82 120 \ 1586.2 1587.2 9 19 0 1615.5 109 Well 8 1565.8 0 577 Well 17 48A 2 104 \ !( y 576 1599.4 !( 1564.1 58 505 743 d 88 u 584 t 60 1564.1 324 272 S 583 1599.2 o 585 r 578 579 86 81 105 d 581 1599.1 1563.8 325 y 20 H 5 53B 105A12 501 12 d 604 1599.1 32 1563.6 504 507 n 80 a 580 l 14 t 603 53 503 506 e 573 299

W 51 47 502 \ 582 s d 748 45 53A n 74 a Well 19 l t 544 59 e 553 749 1586.5 107 304 W \ 544 555 318 s 574 56 53C p 554 572 1586.4 52 a 557 300

M 53 \ t 558 57 1586.1 106 k e !( 9 ee 302 m 569 1586.1 9A r 12A r y 211 15 C 303 l e ble o 567 iv b

P 560 53D u \ Well 7 R t t 50 S n 605606 13 e 316 e 62 g i 768 1558.3 l 79 301 606 612 607 id C 559 r \ 571 4 t :

I 562 !(!( 1558.4 46 r 17

Well 7R a : 552 566 570 61 P e 315 l 1558.0 i 551 568 64 1558.3 F 565 22 54 22A 326 550 563564 54A 1557.9 1558.4 M Dunka Road 22B 306 P 329 !( 327 9 619 543 1557.9 307 305 314 5 : 372 1 542 384 Well 6 368 1559.1 0 208 : 382

2 309

1 539 1597.9 378 334 0 380 362 313 1 1597.8

0 330

2 381 377 328 / 539

2 210 1597.8 367

1 331332 317 / 3

1597.4 : 370 e t 208 364 a 335

D 308 379 : 346 333 r 371 e t o 350 o 374 346

F 342 364 r 349 312 r 311 a 213 374 373 342 347 336 310

B k e e r Well Number an Mine Site C Eggers & Reed Wetland Types Br ch P uth ar s So t r g 1587.1 2007 Ground Elevation (ft MSLi ) Detailed Watersheds e Shrub Swamps (Alder thickets & Shrub-carrs) d l t g e 1586.2 Average 2005 Water Elevation (fet MSL) Surface Water Drainage Divide Coniferous bog R Figure 3 W 1586.2 Average 2006 Water Elevation (ft Mi SL) v Streams Coniferous swamp e 1586.2 Average 2007 Water Elevation (ft Mr SL) I 2005-2007 WETLAND MONITORING Dunka Road Deep marsh; Shallow marsh "R" = Recording well 2,000 1,000 0 2,000 GROUND AND WATER LEVEL ELEVATIONS Monitoring Well Status Hardwood swamp 50 Wetland Number PolyMet Mining !( Wells - Existing Open water (Shallow, open water & lakes) Feet Hoyt Lakes, Minnesota !( Wells - Removed/Relocated Open bog Sedge meadow; Wet meadow 234 225 277 233 230 273 322 274 228 219 275 226 220 297 iver 222 e R 227 218 203 224 223 g id 298 r 100A rt 294 a 531 P 221 534 530 Well 13R 523 1580.1 756 535 Well 12R 217 216 529528 1579.2 295 524 1592.7 84A 240 755 532 744 1579.4 608 1592.0 508!( 518 281

2 Well 14R Well 10R 601 753 1592.2 84 520 m 533 519 266 r 1598.6 600 1575.1 611 a 72 242 !( 521 243 : 525 244 r 1598.2 Well 2R 44 1574.4 280 e !( s 1598.1 610 1574.3 516

U 1601.3 !( !( 247 d 620 536 !( 24 609 282 248 x 527 1600.8 27 522 283 267 246 m

. 526 k 1600.7 511 g 593 ree 517 n 621 C i 595 602 lp r 591 746 Ye Well 15R o 745 100 t 85 i 594 Well 11R 95 90 Well 16R 515 1572.3 n 592590 !(!( 83 o Well 18R 1599.3 1586.3 !(

M 1572.1 751 754 !( 34 512 d 588 Well 4AR 1596.3 1598.4 1585.8 n 37 513 1572.1 271 a 285 l 1596.0 t 589 1597.7 1598.4 1586.0 e 100 33 587 1597.6 1595.7 !( 29 293 W 90A 509 9 !( 77 250 0 747 1597.8 78 43 55 0 202 68 Well 21R 2 699 698 767 98 3 292 _ 286 269 8 97 1589.9 287 0 752 Well 4R 201 1 288 270 0 Well 5M 202 Well 22R !( 6 289

2 1589.8 1615.5 101 99 7 290 4 1598.2 251 1615.5 96 1589.5 11 12A e 586 r 1615.2 1598.0 !( 8 u 1615.3 48 291 254 g i !( 1615.5 F 211 1615.4 18 1597.9 10 500 284 \ 200 !( s 750 !( p 599 114 !( Well 1R Well 9R 268 a 598 103 48A!( 120 m 1592.7 1565.7 _ t 19 58 r 109 1592.4 o 697 577 82 104 1565.5 258 p !( !( 256 e 548 546 576 1592.2 Well 8R 1565.7 505 743 R 584 88 _ 583 1563.8 324 272 9 585 0 578 579581 60 86 81 105 0 547 20 1563.7 325 2 \ 5 32 53B 105A12 50112 504 507 259 9 80 1563.7 0 549 580 0 603 544 14 53 503 506 299 2

\ 573 y 51 47 502 d 582 u 53A t 748 45 74 Well 19R S 544 o 59 r 553 749 1585.6 304 d y 555 574 56 1586.0 53C H 554 572 52 318 d 557 n 1585.6 53 300 a l 106 k t 618 Well Ref1R 569 57 !( 9 e 303 e 107 9A 12A re 302 211 15 r le C W 1592.5 e b \ 567 v b 265 s i tu d 1592.5 50 R S n 768 605606 62 13 53D e a g l d 301 t 1592.4 !( 607 79 ri e 571 4 !(!( Well 7R rt 316 46 17 a W 559562 61 \ 566 570 16 P s 568 64 1558.5 315 p 552 565 Well 6R 22A 22 a 54 550 54A 1558.1 326 M 563564 Dunka Road 306 \ 1597.8 22B t 1558.4 329 e 619 !( 543 1597.6 327 307 305 314 m y 369 372 l 542 384 368 o 382 1597.8 378 P

\ 539 t 334 309 n 380 362 313 e

i 212 l 381 377 328 330 C

\ 210 : 332 317 I 331

622 : e l 370 i 622 208

F 335

308 371 379 333 M 346 P 641 5 642 1 350 312 : 2

0 213 k 311 : e 383 349

2 310 e

1 r ranc C B h Pa 0 h out rt 347 1 s S r 209 364 i 342 0 537538 Well Ref2R g 374 d 2 215 e g

/ l 385 541 t 373 e 319 2 1573.5 e R 338 1 348

/ 206 i W v 354 336 320 3 204 e 1574.0 337 : 321 367 r e t 386 1573.7 a 207 !(

D 632 766 345 : r 637 339 e t 355 o 623 361 353 o F

r 631 340 r 634 631 a 352 B Mine Site Eggers & Reed Wetland Types Well Number Detailed Watersheds Shrub Swamps (Alder thickets & Shrub-carrs) 1587.1 2009 Ground Elevation (ft MSL) 1586.2 Average 2008 Water Elevation (ft MSL) Surface Water Drainage Divide Coniferous bog 1586.2 Average 2009 Water Elevation (ft MSL) Figure 4 Streams Coniferous swamp 2008-2009 WETLAND MONITORING "R" = Recording well I Dunka Road Deep marsh; Shallow marsh 50 Wetland Number 2,000 1,000 0 2,000 GROUND AND WATER LEVEL ELEVATIONS !( Wetland Hydrology Monitoring Well Hardwood swamp PolyMet Mining Open water (Shallow, open water & lakes) Feet Hoyt Lakes, Minnesota Open bog Sedge meadow; Wet meadow 18

13 2004 20062007 2008 2009 12 2005

Precipitation (inches) 7

0 1/8/09 2/7/09 3/9/09 4/8/09 5/8/09 6/7/09 7/7/09 8/6/09 9/5/09 10/5/09 10/1/04 1/29/05 2/28/05 3/30/05 4/29/05 5/29/05 6/28/05 7/28/05 8/27/05 9/26/05 1/24/06 2/23/06 3/25/06 4/24/06 5/24/06 6/23/06 7/23/06 8/22/06 9/21/06 1/19/07 2/18/07 3/20/07 4/19/07 5/19/07 6/18/07 7/18/07 8/17/07 9/16/07 1/14/08 2/13/08 3/14/08 4/13/08 5/13/08 6/12/08 7/12/08 8/11/08 9/10/08 11/9/08 12/9/08 10/31/04 11/30/04 12/30/04 10/26/05 11/25/05 12/25/05 10/21/06 11/20/06 12/20/06 10/16/07 11/15/07 12/15/07 10/10/08

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station

Figure 5 PRECIPITATION STATISTICS FOR 2004-2009 WATER YEARS PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_2009Fig 5 2004-2009Precip_graph 12

0 Ground Surface

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) to Water Depth -20

-24

-28

-32

8/9/06 2/5/07 4/6/07 6/5/07 8/4/07 6/15/05 8/14/05 2/10/06 4/11/06 6/10/06 10/8/06 12/7/06 10/3/07 12/2/07 1/31/08 3/31/08 5/30/08 7/29/08 9/27/08 1/25/09 3/26/09 5/25/09 7/24/09 9/22/09 10/13/05 12/12/05 11/26/08 11/21/09 4R 4M 4AR 4AM 5M 18R 18M

R = Recording well and "M" = Manual well Figure 6 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines NORTHWEST MINE SITE AREA with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 12

Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) to Water Depth -20

-24

-28

-32

R = Recording well and "M" = Manual well Figure 7 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines NORTH-CENTRAL MINE SITE AREA with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 12

Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) to Water Depth -20

-24

-28

-32

13R 13M 14R 14M 15R 15M

R = Recording well and "M" = Manual well Figure 8 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines NORTHEAST MINE SITE AREA with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 12

Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) -20

-24

-28

-32

/9/06 /5/07 /6/07 /5/07 /4/07 /15/05 /14/05 /10/06 /11/06 /10/06 8 0/8/06 2/7/06 2 4 6 8 0/3/07 2/2/07 /31/08 /31/08 /30/08 /29/08 /27/08 /25/09 /26/09 /25/09 /24/09 /22/09 6 8 0/13/05 2/12/05 2 4 6 1 1 1 1 1 3 5 7 9 1/26/08 1 3 5 7 9 1/21/09 1 1 1 1 1R 1M 8R 8M 9R 9M 16R 16M 21R 22R

R = Recording well and "M" = Manual well Figure 9 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines SOUTH-CENTRAL MINE SITE AREA with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 12

4 Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) to Water Depth -20

-24

-28

-32

R = Recording well and "M" = Manual well Wells 3M and 17M were removed because Figure 10 Continuous lines without points they were determined to be within the 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines project footprint SOUTHWEST MINE SITE AREA with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 12

4 Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) -20

-24

-28

-32

Ref1R Ref2R

R = Recording well and "M" = Manual well Figure 11 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines REFERENCE WELLS - WEST OF MINE SITE with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009.xls 18 17 16 15 14 13 12 11 10 9 8 7

Precipitation (inches) Precipitation 6 5 4 3 2 1 0

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station

Figure 12 PRECIPITATION SUMMARY 2005-2009 PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Water Elevation Summary_2009Fig 12 2005-2009Precip 12

4 Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) -20

-24

-28

-32

1R - coniferous swamp 1M - coniferous swamp 1R - coniferous bog 1M - coniferous bog

R = Recording well and "M" = Manual well Figure 13 Continuous lines without points 2005-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines Well 1 with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 Appendices

Appendix A

2006 Wetland Hydrology and Water Elevation Data

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

5 Ground Surface 0

-5

-10 Wetland Threshold

-15 Well Depth (in) Well 6M - 30.5 Well 7M - 29.3 -20 Well 7R - 27.3 Well 19R - 29.7 Depth to Water (inches) to Water Depth -25

-30

-35 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

6 7 7R 19

Figure 1 2006 HYDROLOGY MONITORING DATA Southwest Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2007Data\Copy of PolyMet_HydroData_2007.xls Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

10 Well Depth (in) Well 3M - 15.5 Well 4M - 15.3 5 Well 4R - 27.3 Well 5M - 14.0 Well 17M - 16.0 Ground Surface 0

-5

-10 Wetland Threshold Depth to Water (inches) Water to Depth

-15

-20 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

3 4 4A 4R 5 17

Figure 2 2006 HYDROLOGY MONITORING DATA Northwest Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

5 Well Depth (in) Well 2M - 30.0 Well 10M - 20.3 0 Ground Surface Well 11M - 16.8 Well 12M - 32.5 Well 12R - 28.3 Well 18M - 22.5 -5

-10

Wetland Threshold -15 Depth to Water (inches) to Water Depth

-20 Date of Pumping Test Begin: October 19, 2006 End: November 18, 2006 -25 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

2 10 11 12 12R 18

Figure 3 2006 HYDROLOGY MONITORING DATA North-Central Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

5 Ground Surface 0

-5

-10 Wetland Threshold

-15 Well Depth (in) Well 1M - 19.0

Depth to Water (inches) to Water Depth -20 Well 1R - 27.3 Well 8M - 29.3 -25 Well 9M - 29.5

-30 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

1 1R 8 9

Figure 4 2006 HYDROLOGY MONITORING DATA South-Central Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

0 Ground Surface

-5

-10 Wetland Threshold

Well Depth (in) -15 Well 13M - 18.0 Well 14M - 18.5

Depth to Water (inches) to Water Depth Well 15M - 19.5 Well 16M - 27.3 -20

-25 4/1/2006 4/29/2006 5/27/2006 6/24/2006 7/22/2006 8/19/2006 9/16/2006 10/14/2006 11/11/2006

13 14 15 16

Figure 5 2006 HYDROLOGY MONITORING DATA Northeast Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

1600

1595

1590

1585

1580

1575

1570

Water Elevation (ft MSL) Elevation Water 1565

1560

1555 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

6 7 19

Figure 6 2006 HYDROLOGY MONITORING DATA Southwest Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

1620

1615

1610

1605 Water Elevation (ft MSL) Elevation Water 1600

1595 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

3 4 4A 5 17

Figure 7 2006 HYDROLOGY MONITORING DATA Northwest Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

1602

1600

1598

1596

1594 Water Elevation (ft MSL) Elevation Water

1592

1590 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

2 10 11 12 18

Figure 8 2006 HYDROLOGY MONITORING DATA North-Central Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

1590

1585

1580

1575

1570 Water Elevation (ft MSL) Elevation Water 1565

1560 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

1 8 9

Figure 9 2006 HYDROLOGY MONITORING DATA South-Central Mine and Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 6

2 Precipitation (inches) Precipitation

1590

1585

1580

Water Elevation (ft MSL) Elevation Water 1575

1570 4/1/06 4/29/06 5/27/06 6/24/06 7/22/06 8/19/06 9/16/06 10/14/06 11/11/06

13 14 15 16

Figure 10 2006 HYDROLOGY MONITORING DATA Northeast Stockpile Area PolyMet Mining Hoyt Lakes, Minnesota Appendix B

2007 Wetland Hydrology and Water Elevation Data

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20

Depth to Water (inches) -24 Well 18M was dry from Well Depth (in) late July through August. Well 4R - 27.3 -28 Well 4M - 15.3 Well 4AM - 17.5 -32 Well 5M - 16.5 Well 18M - 22.5 -36 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07

4R 4M 4AM 5M 18M

"R" = Recording well and "M" = Manual well Figure 1 2007 WETLAND HYDROLOGY MONITORING DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009 Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20 Well 10 was dry in late August

Depth to Water (inches) to Water Depth -24 Well Depth (in) Well 2M - 36.5 -28 Well 10M - 23.8 Well 11M - 16.8 -32 Well 12R - 28.3 Well 12M - 35.0 -36 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07

2M 10M 11M 12R 12M

"R" = Recording well and "M" = Manual well Figure 2 2007 WETLAND HYDROLOGY MONITORING DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20 Wells 13M and 14M were dry late July through August; Well 15M was dry for the Depth to Water (inches) -24 second half of August.

-28 Well Depth (in) Well 13M - 21.0 -32 Well 14M - 21.0 Well 15M - 22.5 -36 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07

13M 14M 15M

"R" = Recording well and "M" = Manual well Figure 3 2007 WETLAND HYDROLOGY MONITORING DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20

Depth to Water (inches) -24 Well Depth (in) Well 1R - 27.3 -28 Well 8M - 30.3 Well 9M - 31.5 Well 8M was dry in -32 Well 16M - 32.8 mid-August/September -36 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07 1R 8M 9M 16M

"R" = Recording well and "M" = Manual well Figure 4 2007 WETLAND HYDROLOGY MONITORING DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20 Well Depth (in) Depth to Water (inches) -24 Well 6M and Well 19M were dry in mid Well 3M - 15.5 Well 6M - 30.5 August; Well 6 remained dry through -28 Well 7R - 27.3 end of August Well 17M - 16.0 -32 Well 19M - 30.7 -36 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07

1R 3M 6M 7R 17M 19M

"R" = Recording well and "M" = Manual well Figure 5 2007 WETLAND HYDROLOGY MONITORING DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota RangeRangeRange of ofRange ofNormal Normal Normal of Precipitation NormalPrecipitation Precipitation Precipitation Babbitt Babbitt Babbitt NWS NWSBabbitt NWS Station Station StationNWS Station DailyDailyDaily Precipitation Precipitation PrecipitationDaily Precipitation Babbitt Babbitt Babbitt NWS NWSBabbitt NWS Station Station StationNWS Station 30-Day30-Day30-Day Rolling 30-DayRolling Rolling Total TotalRolling Total Precipitation Precipitation Precipitation Total Precipitation MonthlyMonthlyMonthly PrecipitationMonthly Precipitation Precipitation Precipitation Babbitt Babbitt Babbitt NWS NWSBabbitt NWS Station Station StationNWS Station 18999

16888

14777

12666

10555

4844

3633 Precipitation (inches) Precipitation (inches) Precipitation (inches) Precipitation (inches) Precipitation

2422

1211

000

1620

1610

1600

1590

1580

1570 Water Table Range

Water Elevation (ft MSL) Water Elevation Ground Elevation (ft) Well 4R - 1615.6 Well 4R - 1.4 ft (16.8 in) Well 4M - 1615.6 Well 4M - 0.9 ft (10.8 in) 1560 Well 4AM - 1598.1 Well 4AM - 1.2 ft (14.4in) Well 5M - 1615.5 Well 5M - 0.8 ft (9.6 in) Well 18M - 1596.4 Well 18M - 2.0 ft (24 in) 1550 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07 4R 4M 4AM 5M 18M

"R" = Recording well and "M" = Manual well Figure 6 2007 WETLAND WATER ELEVATION DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota RangeRangeRange of of ofRangeNormal Normal Normal of Precipitation Precipitation NormalPrecipitation Precipitation Babbitt Babbitt Babbitt NWS NWS BabbittNWS Station Station Station NWS Station DailyDailyDaily Precipitation Precipitation PrecipitationDaily Precipitation Babbitt Babbitt Babbitt NWS NWS BabbittNWS Station Station Station NWS Station 30-Day30-Day30-Day Rolling Rolling 30-DayRolling Total Total RollingTotal Precipitation Precipitation Precipitation Total Precipitation MonthlyMonthlyMonthly Precipitation PrecipitationMonthly Precipitation Precipitation Babbitt Babbitt Babbitt NWS NWS BabbittNWS Station Station Station NWS Station 91899

81688

71477

61266

51055

4448

3336 Precipitation (inches) Precipitation (inches) Precipitation (inches) Precipitation (inches) Precipitation

2224

1112

000

1620

1610

1600

1590

1580

1570 Ground Elevation (ft) Water Table Range Water Elevation (ft MSL) Water Elevation Well 2M - 1601.7 Well 2M - 1.4 ft (16.8 in) Well 10M - 1599.4 Well 10M - 1.6 ft (19.2 in) 1560 Well 11M - 1598.1 Well 11M - 1.1 ft (13.2 in) Well 12R - 1592.7 Well 12R - 1.5 ft (18.0in) Well 12M - 1592.7 Well 12M - 1.3 ft (15.6 in) 1550 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07

2M 10M 11M 12R 12M

"R" = Recording well and "M" = Manual well Figure 7 2007 WETLAND WATER ELEVATION DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota RangeRange ofRange of Normal Normal of NormalPrecipitation Precipitation Precipitation Babbitt Babbitt NWSBabbitt NWS Station StationNWS Station DailyDaily Precipitation PrecipitationDaily Precipitation Babbitt Babbitt NWSBabbitt NWS Station StationNWS Station 30-Day30-Day 30-DayRolling Rolling TotalRolling Total Precipitation Precipitation Total Precipitation MonthlyMonthlyMonthly Precipitation Precipitation Precipitation Babbitt Babbitt NWSBabbitt NWS Station StationNWS Station 189 9

168 8

147 7

126 6

105 5

484

363 Precipitation (inches) Precipitation Precipitation (inches) Precipitation (inches) Precipitation (inches) Precipitation

242

121

0 0

1620

1610

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation Ground Elevation (ft) Water Table Range Well 13M - 1580.2 Well 13M - 1.6 ft (19.2 in) 1560 Well 14M - 1575.5 Well 14M - 1.5 ft (18.0 in) Well 15M - 1572.8 Well 15M - 1.5 ft (18.0 in) 1550 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07 13M 14M 15M

"R" = Recording well and "M" = Manual well Figure 8 2007 WETLAND WATER ELEVATION DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 18

6 Precipitation (inches) Precipitation

1620 Ground Elev (ft) Well 1R - 1586.4 Water Table Range 1610 Well 1M - 1586.4 Well 1R - 2.0 ft (24.0 in) Well 8M - 1564.1 Well 1M - 2.0 ft (24.0 in) Well 9M - 1565.9 Well 8M - 2.6 ft (31.2 in) Well 16M - 1586.5 Well 9M - 2.0 ft (24.0 in) 1600 Well 16M - 1.4 ft (16.8 in)

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 4/1/07 5/1/07 4/16/07 5/16/07 5/31/07 6/15/07 6/30/07 7/15/07 7/30/07 8/14/07 8/29/07 9/13/07 9/28/07 10/13/07 10/28/07 11/12/07 11/27/07 1R 1M 8M 9M 16M

"R" = Recording well and "M" = Manual well Figure 9 2007 WETLAND WATER ELEVATION DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota RangeRange Rangeof of Normal Normal of Normal Precipitation Precipitation Precipitation Babbitt Babbitt BabbittNWS NWS Station NWSStation Station DailyDaily Precipitation PrecipitationDaily Precipitation Babbitt Babbitt BabbittNWS NWS Station NWSStation Station 30-Day30-Day30-Day Rolling Rolling RollingTotal Total Precipitation PrecipitationTotal Precipitation MonthlyMonthlyMonthly Precipitation Precipitation Precipitation Babbitt Babbitt BabbittNWS NWS Station NWSStation Station 1899

1688

1477

1266

1055

484

363 Precipitation (inches) Precipitation Precipitation (inches) Precipitation (inches) Precipitation

242

121

000

1620 Ground Elevation (ft) Water Table Range Well 3M - 1597.0 Well 7M - 1558.3 Well 3M - 1.1 ft (13.2 in) Well 7M - 1.6 ft (19.2 in) Well 6M - 1597.9 1610 Well 17M - 1599.4 Well 6M - 2.7 ft (32.4 in) Well 17M - 1.2 ft (14.4 in) Well 7R - 1558.3 Well 19M - 1586.5 Well 7R - 1.2 ft (14.4 in) Well 19M - 2.6 ft (31.2 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 04/01/07 04/16/07 05/01/07 05/16/07 05/31/07 06/15/07 06/30/07 07/15/07 07/30/07 08/14/07 08/29/07 09/13/07 09/28/07 10/13/07 10/28/07 11/12/07 11/27/07 3M 6M 7R 7M 17M 19M

"R" = Recording well and "M" = Manual well Figure 10 2007 WETLAND WATER ELEVATION DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Appendix C

2008 Wetland Hydrology and Water Elevation Data

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20

Depth to Water (inches) to Water Depth -22 -24 Well Depth (in) -26 Well 4R - 24.5 Well 4AR - 39.5 -28 Well 5M - 19.7 -30 Well 18R - 44.1 -32 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

4R 4AR 5M 18R

"R" = Recording well and "M" = Manual well Figure 1 2008 WETLAND HYDROLOGY MONITORING DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009.xls Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20 -22 Depth to Water (inches) to Water Depth -24 Well Depth (in) -26 Well 2R - 44.8 -28 Well 10R - 43.5 -30 Well 11R - 42.3 Well 12R - 25.6 -32 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

2R 10R 11R 12R

"R" = Recording well and "M" = Manual well Figure 2 2008 WETLAND HYDROLOGY MONITORING DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 0 Ground Surface -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20 -22 Depth to Water (inches) to Water Depth -24 Well Depth (in) -26 Well 13R - 41.4 -28 Well 14R - 44.7 -30 Well 15R - 42.7 -32 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

13R 14R 15R

"R" = Recording well and "M" = Manual well Figure 3 2008 WETLAND HYDROLOGY MONITORING DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 Ground Surface 2 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20 Well Depth (in) -22 Well 1R - 42.1 Depth to Water (inches) to Water Depth -24 Well 8R - 43.2 -26 Well 9R - 41.1 -28 Well 16R - 42.1 -30 Well 21R - 42.1 -32 Well 22R - 43.1 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

1R 1M 8R 9R 9M 16R 21R 22R

"R" = Recording well and "M" = Manual well Figure 4 2008 WETLAND HYDROLOGY MONITORING DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20

Depth to Water (inches) -22 -24 -26 Well Depth (in) -28 Well 6R - 44.0 -30 Well 7R - 21.5 -32 Well 19R - 40.5 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

6R 7R 19R

"R" = Recording well and "M" = Manual well Figure 5 2008 WETLAND HYDROLOGY MONITORING DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 -16 -18 -20

Depth to Water (inches) to Water Depth -22 -24 -26 -28 Well Depth (in) -30 Well Ref1R - 41.5 -32 Well Ref2R - 37.5 -34 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08 Ref1R Ref2R

"R" = Recordingwell and "M" = Manual well Figure 6 2008 WETLAND HYDROLOGY MONITORING DATA Reference Wells - West of Mine Site PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620

1610

1600

1590

1580

1570 Water Table Range Water Elevation (ft MSL) Elevation Water Ground Elevation (ft) Well 4R - 0.9 ft (10.8 in) Well 4R - 1615.4 Well 4AR - 1.0 ft (12 in) Well 4AR - 1597.7 1560 Well 5M - 0.2 ft (2.4 in) Well 5M - 1615.4 Well 18R - 1.3 ft (15.6 in) Well 18R - 1596.7 1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08 4R 4AR 4AM 5M 18R 18M

"R" = Recording well and "M" = Manual well Figure 7 2008 WETLAND WATER ELEVATION DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620

1610

1600

1590

1580

1570

Water Elevation (ft MSL) Ground Elevation (ft) Water Table Range Well 2R - 1601.3 Well 2R - 1.2 ft (14.4 in) 1560 Well 10R - 1598.8 Well 10R - 1.3 ft (15.6 in) Well 11R - 1599.3 Well 11R - 1.5 ft (18.0 in) Well 12R - 1592.7 Well 12R - 1.4 ft (16.8 in) 1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

2R 2M 10R 10M 11R 11M 12R

"R" = Recording well and "M" = Manual well Figure 8 2008 WETLAND WATER ELEVATION DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620

1610

1600

1590

1580

1570 Water Elevation (ft MSL) Elevation Water Ground Elevation (ft) Water Table Range 1560 Well 13R - 1580.1 Well 13R - 1.8 ft (21.6 in) Well 14R - 1575.4 Well 14R - 1.5 ft (18.0 in) Well 15R - 1572.4 Well 15R - 1.9 ft (22.8 in) 1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08 13R 13M 14R 14M 15R 15M

"R" = Recording well and "M" = Manual well Figure 9 2008 WETLAND WATER ELEVATION DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elev (ft) Water Table Range Well 1R - 1592.8 Well 16R - 1586.2 Well 1R - 1.8 ft (21.6 in) Well 16R - 1.3 ft (15.6 in) 1610 Well 8R - 1564.2 Well 21R - 1590.3 Well 8R - 2.5 ft (30.0 in) Well 21R - 1.3 ft (15.6 in) Well 9R - 1565.6 Well 22R - 1598.5 Well 9R - 0.3 ft (3.6 in) Well 22R - 2.2 ft (26.4 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08 1R 1M 8R 8M 9R 9M 16R 16M 21R 22R

"R" = Recording well and "M" = Manual well Figure 10 2008 WETLAND WATER ELEVATION DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elevation (ft) Water Table Range Well 6R - 1598.0 Well 6R - 2.9 ft (34.8 in) 1610 Well 7R - 1558.3 Well 7R - 1.1 ft (13.2 in) Well 19R - 1586.4 Well 19R - 2.3 ft (27.6 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08

6R 6M 7R 19R 19M

"R" = Recording well and "M" = Manual well Figure 11 2008 WETLAND WATER ELEVATION DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elevation (ft) Water Table Range Well Ref1R - 1592.7 Well Ref1R - 1.0 ft (12.0 in) 1610 Well Ref2R - 1573.9 Well Ref2R - 2.1 ft (25.2 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Elevation Water

1560

1550 5/1/08 5/16/08 5/31/08 6/15/08 6/30/08 7/15/08 7/30/08 8/14/08 8/29/08 9/13/08 9/28/08 10/13/08 10/28/08 11/12/08 11/27/08 Ref1R Ref2R

"R" = Recording well and "M" = Manual well Figure 12 2008 WETLAND WATER ELEVATION DATA Reference Wells - West of Mine Site PolyMet Mining Hoyt Lakes, Minnesota Appendix D

2009 Wetland Hydrology and Water Elevation Data

Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 Depth to Water (inches) to Water Depth -16 Well Depth (in) -18 Well 4R - 27.8 -20 Well 4AR - 39.5 Well 5M - 16.3 -22 Well 18R - 42.3 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

4R 4M 4AR 5M 18R

"R" = Recording well and "M" = Manual well Figure 1 2009 WETLAND HYDROLOGY MONITORING DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009.xls Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 8 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station

3 Precipitation (inches) Precipitation 2

12 10 Well Depth (in) 8 Well 2R - 44.5 Well 10R - 42.3 6 Well 11R - 42.3 4 Well 12R - 25.3 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 Depth to Water (inches) Water to Depth -16 -18 -20 -22 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

2R 2M 10R 11R 11M 12R

"R" = Recording well and "M" = Manual well Figure 2 2009 WETLAND HYDROLOGY MONITORING DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 Well Depth (in) Well 13R - 42.0 8 Well 14R - 43.5 6 Well 15R - 41.5 4 2 Ground Surface 0 -2 -4 -6 -8 -10 -12 Wetland Threshold -14 Depth to Water (inches) to Water Depth -16 -18 -20 -22 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

13R 14R 15R

"R" = Recording well and "M" = Manual well Figure 3 2009 WETLAND HYDROLOGY MONITORING DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 Well Depth (in) Well 1R - 40.3 Well 16R - 42.1 8 Well 8R - 39.0 Well 21R - 41.4 6 Well 9R - 41.5 Well 22R - 42.5 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 Depth to Water (inches) to Water Depth -16 -18 -20 -22 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

1R 1M 8R 9R 16R 21R 22R

"R" = Recording well and "M" = Manual well Figure 4 2009 WETLAND HYDROLOGY MONITORING DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 Well Depth (in) Well 6R - 41.3 8 Well 7R - 21.5 6 Well 19R - 40.5 4 2 0 Ground Surface -2 -4 -6 -8 -10 -12 Wetland Threshold -14 Depth to Water (inches) -16 -18 -20 -22 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

6R 7R 19R

"R" = Recording well and "M" = Manual well Figure 5 2009 WETLAND HYDROLOGY MONITORING DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

12 10 Well Depth (in) Well Ref1R - 40.0 8 Well Ref2R - 38.0 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold -12 -14 Depth to Water (inches) to Water Depth -16 -18 -20 -22 -24 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09 Ref1R Ref2R

"R" = Recordingwell and "M" = Manual well Figure 6 2009 WETLAND HYDROLOGY MONITORING DATA Reference Wells - West of Mine Site PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620

1610

1600

1590

1580

1570 Water Elevation (ft MSL) Elevation Water Ground Elevation (ft) Water Table Range Well 4R - 1615.5 Well 4R - 0.3 ft (3.6 in) 1560 Well 4AR - 1597.7 Well 4AR - 0.4 ft (4.8 in) Well 5M - 1615.5 Well 5M - 0.3 ft (3.6 in) Well 18R - 1596.3 Well 18R - 0.9 ft (10.8 in) 1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09 4R 4M 4AR 18R

"R" = Recording well and "M" = Manual well Figure 7 2009 WETLAND WATER ELEVATION DATA Northwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620

1610

1600

1590

1580

1570 Water Elevation (ft MSL) Ground Elevation (ft) Water Table Range Well 2R - 0.7 ft (8.4 in) 1560 Well 2R - 1601.3 Well 10R - 1598.6 Well 10R - 0.7 ft (8.4 in) Well 11R - 1599.3 Well 11R - 0.6 ft (7.2 in) Well 12R - 1592.7 Well 12R - 0.8 ft (9.6 in) 1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

2R 2M 10R 11R 11M 12R

"R" = Recording well and "M" = Manual well Figure 8 2009 WETLAND WATER ELEVATION DATA North-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elevation (ft) Water Table Range Well 13R - 1580.1 Well 13R - 1.1 ft (13.2 in) 1610 Well 14R - 1575.1 Well 14R - 0.9 ft (10.8 in) Well 15R - 1572.3 Well 15R - 0.6 ft (7.2 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Elevation Water

1560

1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09 13R 14R 15R

"R" = Recording well and "M" = Manual well Figure 9 2009 WETLAND WATER ELEVATION DATA Northeast Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elev (ft) Water Table Range Well 1R - 1592.7 Well 16R - 1586.3 Well 1R - 1.2 ft (14.4 in) Well 16R - 0.7 ft (8.4 in) Well 21R - 1589.9 1610 Well 8R - 1563.8 Well 8R - 1.5 ft (18.0 in) Well 21R - 0.6 ft (7.2 in) Well 9R - 1565.7 Well 22R - 1592.8 Well 9R - 0.2 ft (2.4 in) Well 22R - 0.9 ft (10.8 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

1R 1M 8R 9R 16R 21R 22R

"R" = Recording well and "M" = Manual well Figure 10 2009 WETLAND WATER ELEVATION DATA South-Central Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elevation (ft) Water Table Range Well 6R - 1597.8 Well 6R - 0.8 ft (9.6 in) 1610 Well 7R - 1558.5 Well 7R - 0.6 ft (7.2 in) Well 19R - 1585.6 Well 19 - 0.6 ft (7.2 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Water Elevation

1560

1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09

6R 7R 19R

"R" = Recording well and "M" = Manual well Figure 11 2009 WETLAND WATER ELEVATION DATA Southwest Mine Site Area PolyMet Mining Hoyt Lakes, Minnesota Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 8

3 Precipitation (inches) Precipitation 2

1620 Ground Elevation (ft) Water Table Range Well Ref1R - 1592.5 Well Ref1R - 0.3 ft (3.6 in) 1610 Well Ref2R - 1573.5 Well Ref2R - 0.4 ft (4.8 in)

1600

1590

1580

1570 Water Elevation (ft MSL) Elevation Water

1560

1550 4/28/09 5/13/09 5/28/09 6/12/09 6/27/09 7/12/09 7/27/09 8/11/09 8/26/09 9/10/09 9/25/09 10/10/09 10/25/09 Ref1R Ref2R

Figure 12 2009 WETLAND WATER ELEVATION DATA Reference Wells - West of Mine Site PolyMet Mining Hoyt Lakes, Minnesota Appendix E

Well Location Photographs

Date of Photo: June 28, 2005 Well 1 – Removed in 2008 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 1 – Relocated in 2008 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 2 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Date of Photo: June 29, 2005 Well 3 – Removed in April 2008 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 4 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 4A Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 5 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 6 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 7 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 8 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 9 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 10 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 11 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 12 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 13 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 14 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 15 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 16 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Date of Photo: June 29, 2005 Well 17 – removed in 2008 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 18 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 19 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 21 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Well 22 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Reference Well 1 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN

Top: June 2009 Reference Well 2 Bottom: October 2009 PolyMet Mining Company Hoyt Lakes, MN Appendix F

Depth to Bedrock

PMitchell2 Main08

Main04

iver e R g id r Main07b rt Main07a a PMitchell3 P Main02

Main07e CloquetPit Main05 Main06 eek Cr elp Y Main09 Main01 East Pit PM11 PM13 MudLake02 Central Pit PM12

PM08

PM10 Main10 PM04 PM09 PM06 PM07 West Pit PM01

Main11

ek re r StubbleCr1 C e ble v b i tu PM03 R S e g LongNose1 id r Wetlegs1 rt Main12 a PM02 P Dunka Road StubbleCr2

Main13

Wetlegs2 Main14 SBranch6 SBranch9 Wetlegs3 Barr Footer: Date: 3/8/2010 3:03:43 PM File: I:\Client\Polymet\Maps\Wetlands\WetlandHydroStudy\2009\2009_Report_maps\Figure 1 Depth to Bedrock.mxd User: Depth arm2 to Bedrock.mxd 1 I:\Client\Polymet\Maps\Wetlands\WetlandHydroStudy\2009\2009_Report_maps\Figure File: PM 3:03:43 3/8/2010 Date: Footer: Barr k e e r ranch C B Pa uth rt Dunka Road s Depth to Bedrock (feet) So r i g d e l g t e Proposed Railroad e 0 - 10 R i W v Figure 1 e Existing Railroad 10.1 - 20 r DEPTH TO BEDROCK Streams 20.1 - 30 2,000 1,000 0 2,000 PolyMet Mining 30.1 - 40 Surface Drainage Divide Hoyt Lakes, Minnesota Surface Watersheds 40.1 - 50 Feet Mine Site 50.1 - 58 Appendix G

Phase III Hydrogeology Study

Table 1 Pumping Test Summary 2006 PolyMet Mining Company Hoyt Lakes, Minnesota

Total depth of well/piezometer Screen Depth (ft Distance from Maximum Maximum (ft below ground below ground Geologic Pumping Well P2 Drawdown Drawdown ID Type surface) surface) Deposit (ft) (in) (ft) Pumping well - open None - open from Virginia P2 hole bedrock well 610 27 to 610 ft Formation 0 2519 209.9 20P Piezometer 7.5 7.5 Organic Soil 145 5.4 0.5 20 Well 2.4 2.4 Organic Soil 160 5.8 0.5 None - open from Duluth Ob2 Open hole bedrock well 100 18 to 100 ft Formation 280 55.7 4.6 2P Piezometer 7.5 7.5 Organic Soil 750 1.7 0.1 12 Well 3.0 3 Organic Soil 1,400 2.3 0.2 12P Piezometer 7.5 7.5 Organic Soil 1,400 3.6 0.3 1R Well 2.3 2.3 Organic Soil 3,800 6.0 0.5 7R Well 2.3 2.3 Organic Soil 10,300 3.6 0.3 4R Well 2.3 2.3 Organic Soil 11,500 2.4 0.2

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\Phase III data\Summary_updated 2 m r a

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B k e D e !? Pumping Test Piezometerr Proposed Project Areas ranch C B Pa uth rt s So r i !> Pumping Test Well g Eggers & Reed Wetland Types d e l g t e !( All Other Wetland Mone itoring Wells Shrub Swamps (Alder thickets & Shrub-carrs) R Figure 1 W iv e ") Pumping Well (P2) Coniferous bog r I PUMPING AND OBSERVATION LOCATIONS ") Bedrock Observation Well (Ob2) Coniferous swamp 2,000 1,000 0 2,000 PHASE III HYDROGEOLOGIC INVESTIGATION Surface Water Drainage Divide Deep marsh; Shallow marsh PolyMet Mining Inc. Detailed Watersheds Hardwood swamp Feet Hoyt Lakes, Minnesota Mine Site Open water (Shallow, open water & lakes) Streams Open bog Dunka Road Sedge meadow; Wet meadow Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 5

2 Precipitation (inches) Precipitation

-100

-300

-500

-700

-900

-1100

-1300

-1500

-1700 Drawdown (inches) -1900 -2100

-2300 Pump On Pump Off -2500 10/4/2006 10/6/2006 10/8/2006 11/1/2006 11/3/2006 11/5/2006 11/7/2006 11/9/2006 10/10/2006 10/12/2006 10/14/2006 10/16/2006 10/18/2006 10/20/2006 10/22/2006 10/24/2006 10/26/2006 10/28/2006 10/30/2006 11/11/2006 11/13/2006 11/15/2006 11/17/2006 11/19/2006 11/21/2006 11/23/2006 11/25/2006 11/27/2006 11/29/2006

Pumping 1R 2P 4R 7R 12 12P 20 20P Ob-2 P-2

Figure 2 OBSERVED DRAWDOWN AND RECOVERY PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\Phase III data\Summary_updated Range of Normal Precipitation Babbitt NWS Station Daily Precipitation Babbitt NWS Station 30-Day Rolling Total Precipitation Monthly Precipitation Babbitt NWS Station 5

2 Precipitation (inches) Precipitation

-5

-15

-25

-35

-45 Drawdown (inches) -55

-65 Pump On Pump Off -75 10/4/2006 10/6/2006 10/8/2006 11/1/2006 11/3/2006 11/5/2006 11/7/2006 11/9/2006 10/10/2006 10/12/2006 10/14/2006 10/16/2006 10/18/2006 10/20/2006 10/22/2006 10/24/2006 10/26/2006 10/28/2006 10/30/2006 11/11/2006 11/13/2006 11/15/2006 11/17/2006 11/19/2006 11/21/2006 11/23/2006 11/25/2006 11/27/2006 11/29/2006 Pumping 1R 2P 4R 7R 12 12P 20 20P Ob-2 P-2

Figure 3 OBSERVED DRAWDOWN AND RECOVERY PolyMet Mining Hoyt Lakes, Minnesota

2 Precipitation (inches) Precipitation

-1

-2

-3

-4

Drawdown (inches) -5

-6

-7 Pump On Pump Off -8 10/4/2006 10/6/2006 10/8/2006 11/1/2006 11/3/2006 11/5/2006 11/7/2006 11/9/2006 10/10/2006 10/12/2006 10/14/2006 10/16/2006 10/18/2006 10/20/2006 10/22/2006 10/24/2006 10/26/2006 10/28/2006 10/30/2006 11/11/2006 11/13/2006 11/15/2006 11/17/2006 11/19/2006 11/21/2006 11/23/2006 11/25/2006 11/27/2006 11/29/2006 Pumping 1R 2P 4R 7R 12 12P 20 20P

Figure 4 OBSERVED DRAWDOWN AND RECOVERY PolyMet Mining Hoyt Lakes, Minnesota

2 Precipitation (inches) Precipitation

12 10 8 6 4 2 Ground Surface 0 -2 -4 -6 -8 -10 Wetland Threshold

Depth to Water (inches) to Water Depth -12 -14 Date of Pumping Test Begin: October 19, 2006 -16 End: November 18, 2006 -18 -20 4/1/06 4/8/06 5/6/06 6/3/06 7/1/06 7/8/06 8/5/06 9/2/06 9/9/06 4/15/06 4/22/06 4/29/06 5/13/06 5/20/06 5/27/06 6/10/06 6/17/06 6/24/06 7/15/06 7/22/06 7/29/06 8/12/06 8/19/06 8/26/06 9/16/06 9/23/06 9/30/06 10/7/06 11/4/06 10/14/06 10/21/06 10/28/06 11/11/06 11/18/06 11/25/06

1R 4R 7R 12R

Figure 5 2006 RECORDING WELL MONITORING DATA PolyMet Mining Hoyt Lakes, Minnesota Appendix H

Overburden Boring Logs

iver e R g id r rt a P 2 m r a

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6 1 : 6 0 : 2 1

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: e t a D

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B k e e r ranch C B Pa .! Upland Soil Boring Sites Eggers & Reed Wetland Types uth rt s So r i g d e Wetland Soil Boring Sitl es Shrub Swamps (Alder thickets & Shrub-carrs) g .! t e e R i Mine Site W Coniferous bog v Figure 1 e Streams Coniferous swamp r I LOCATION OF WETLANDS AND Dunka Road Deep marsh; Shallow marsh 2,000 1,000 0 2,000 OVERBURDEN SITES Hardwood swamp PolyMet Mining Inc. Open water (Shallow, open water & lakes) Feet Hoyt Lakes, Minnesota Open bog Sedge meadow; Wet meadow Boring RS-03 Boring RS-04 Boring RS-07 Boring RS-11 Boring RS-13 Surface Elevation 1595.5 ft Surface elevation = 1600.0 ft Surface Elevation 1608.0 ft Surface Elevation 1594.0 ft Surface Elevation 1606.0 ft 1' Oi 2.5YR 2.5/1 peat 1' Oi 10YR 2/2 peat 1' Oa 10YR 2/2 peat FROZEN 1' Oi/Oa 5YR 2.5/1 peat 1.5' sand with silt 7.5YR 2.5/3 soil FROZEN silty sand w/gravel 2.5Y 3/3 soil 2' Oe w/silty sand 10YR 2/2, mottles 10YR 3/3 soil WET silty sand 7.5YR 2.5/3 & 7.5YR 3/1 MOIST VERY w/2.5YR 3/4 mottles 3' gravelly silty sand 2.5YR 3/3, mottles 7.5YR 3/3 2.5' till WET MOIST up to 10% organic material till gravelly silty sand Gley 1 4/5GY 5' sand w/gravel 7.5YR 3/3, mottles 7.5YR 5/8 mottles present Oi/Oa 10YR 2/1 till 6' 6' silty sand w/gravel MOIST Interval is too destroyed by drilling to ID 10YR 4/3 sand w/ssilty gravel 8' 9' 5Y 2.5/1 bedrock sandy silt w/gravel, up to 5% organic matter till 10' 10' 10' 9.5' to 10' gravel w/silt and sand 10YR 3/2 till WET bedrock @ 8' G ley1 5/10Y silty sand w/gravel 11' sandy gravel w/silt Gley 1 2.5/10Y WET 10' to 11.5' silty sand w/gravel to silty gravel w/sand 12' WET 10YR 4/3 WET bedrock 10YR 2/2, mottles 2.5YR 2.5/1 MOIST sandy and gravelly silt, no organic matter 13' bedrock @ 11' 11.5' to 15' gravel w/sand 10YR 2/2 to 10YR 2/1 Gley1 5/10Y silt sand w/gravel 10YR 4/3 to 10YR 3/1 15' 15' mottles present 15' silty sand w/gravel sand w/gravel Gley1 5/10Y silty sand w/gravel 17' 2.5Y 2.5/1 10YR 3/1 sand w/gravel outwash Gley 1 2.5/N 20' 20' 20' gravelly silt MOIST 22' Gley 1 2.5/10Y MOIST silty sand w/gravel 10YR 3/1 sand w/gravel to bedrock 24' Gley 1 2.5/N WET bedrock @ 22' 25' gravel w/ silt & sand Gley1 2.5/N to Gley 1 6/1 bedrock 25' bedrock @ 25' sand w/ silt to sand w/gravel 10YR 2/1 28' gravelly silty sand till WET Gley 1 3/10Y 31' gravelly silty sand 33' Gley 1 3/10Y bedrock bedrock @ 33'

organic soil mineral soil bedrock

Figure 2

OVERBURDEN CHARACTERIZATION PROFILES PolyMet Mining P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\Report\Appendix H - Overburden Boring Logs\boring logs mine site_rev 03 23 2010Wetland Hoyt Lakes, MN Boring RS-06 Boring RS-09 Boring RS-12 Boring RS-16A Boring RS-20A Surface Elevation 1611.0 ft Surface Elevation 1594.0 ft Surface Elevation 1608.0 ft Surface Elevation 1595.5 ft Surface elevation = 1600.0 ft 1' silty sand 10YR 4/4 soil 1' sand with silt 7.5YR 2.5/3 soil FROZEN soil FROZEN 1' silty sand 10YR 3/6 soil MOIST silty sand 2.5 Y 3/3 till 2' silty sand 7.5YR 3/2 2' sandy silt 7.5YR 2.5/2 to 7.5YR 2.5/3 2' 2' to 3.5' silty sand w/gravel 7.5YR 3/4 till MOIST gravelly silty sand outwash bedrock 2.5' <5% mottles 5YR 2.5/1 and 5YR 4/6 10YR 4/4 to 2.5Y 4/4 DRY sand 10YR 5/4 bedrock @ 2' siltly sand with gravel 2.5Y 4/2 5' 3.5' to 4.5' large granitoid boulder TO MOIST 4.5' to 7.5' sandy silt w/gravel 7.5YR 3/4 MOIST 5.5' till DRY 30-40% mottles 10YR 4/6 silty sand with gravel 10YR 4/4 TO 6.5' 8' DRY 7' till <5% mottles 5YR 3/4 MOIST bedrock DRY 7.5' to 21' silty sand w/gravel 8' sandy lean clay with gravel 2.5Y 3/1 WET bedrock @ 6.5' 10YR 4/3 bedrock 10' bedrock @ 8' MOIST silty sand with gravel 2.5Y 4/3 <5% mottles 5YR 5/4 15' WET MOIST to sand with silt and gravel 2.5Y 4/3 WET

WET 19.5' 21' 20.5' sand 10YR 4/3 outwash bedrock 22' silty sand with gravel Gley1 3/N mottles 10YR 5/6 till bedrock @ 21' bedrock bedrock @ 22'

organic soil mineral soil bedrock

Figure 3

Water Hydrology by Wetland Type

Table 1 2005-2009 Average Water Elevation Data PolyMet Mining Hoyt Lakes, Minnesota

Eggers & Reed Wetland Circular 39 Average Water Elevation (ft MSL) Wetland Type ID Type Well ID 2005 2006 2007 2008 2009 Coniferous bog 15 8 Well 19M 1586.4 1586.1 1586.1 1586.9 --- Coniferous bog 15 8 Well 19R ------1586.0 1592.2 Coniferous swamp 48 7 Well 1M 1586.4 1586.1 1586.2 ------Coniferous swamp 48 7 Well 1R 1586.3 1587.1 1587.2 --- 1600.8 Coniferous bog 48 8 Well 1M ------1592.0 1592.2 Coniferous bog 48 8 Well 1R ------1592.4 1600.7 Coniferous bog 48 8 Well 21M ------1589.1 --- Coniferous bog 48 8 Well 21R ------1589.8 1615.4 Coniferous bog 48 8 Well 22M ------1598.3 1615.5 Coniferous bog 48 8 Well 22R ------1598.0 1597.9 Coniferous bog 83 8 Well 15M 1572.2 1572.2 1572.3 1572.0 1563.8 Coniferous bog 83 8 Well 15R ------1572.1 1563.7 Coniferous bog 84 8 Well 13M 1578.7 1579.6 1579.5 1579.4 1565.8 Coniferous bog 84 8 Well 13R ------1579.2 1565.7 Coniferous bog 90 8 Well 14M 1574.3 1574.3 1574.6 1574.9 1598.1 Coniferous bog 90 8 Well 14R ------1574.4 1598.1 Coniferous bog 90 8 Well 16M 1586.2 1586.2 1586.3 1586.3 1598.5 Coniferous bog 90 8 Well 16R ------1585.8 1598.4 Coniferous bog 100 8 Well 2M 1600.7 1600.5 1601.0 1600.8 1591.4 Coniferous bog 100 8 Well 2R ------1600.8 1592.2 Coniferous bog 100 8 Well 10M 1598.3 1598.4 1598.6 1597.8 1579.4 Coniferous bog 100 8 Well 10R ------1598.2 1579.4 Coniferous bog 100 8 Well 11M 1597.4 1597.2 1597.3 1598.3 1574.3 Coniferous bog 100 8 Well 11R ------1598.4 1574.3 Coniferous bog 100 8 Well 12M 1592.4 1592.1 1592.1 1592.1 1572.1 Coniferous bog 100 8 Well 12R 1591.6 1591.2 1591.9 1592.0 1572.1 Coniferous bog 100 8 Well 18M 1595.4 1595.5 1595.4 1595.9 1586.0 Coniferous bog 100 8 Well 18R ------1596.0 1586.0 Coniferous bog 103 8 Well 3M 1597.0 1596.9 1596.8 ------Coniferous bog 103 8 Well 17M 1599.2 1599.1 1599.1 --- 1595.8 Coniferous bog 106 8 Well 8M 1564.1 1563.8 1563.6 1563.6 1595.7 Coniferous bog 106 8 Well 8R ------1563.7 1585.6 Coniferous bog 114 8 Well 4M 1615.7 1615.4 1615.5 1615.4 1585.6 Coniferous bog 114 8 Well 4R 1615.5 1615.6 1616.1 1615.2 1589.6 Coniferous bog 114 8 Well 4AM 1597.8 1598.0 1597.9 1597.7 1589.5 Coniferous bog 114 8 Well 4AR ------1597.6 1597.8 Coniferous bog 114 8 Well 5M 1615.5 1615.6 1615.5 1615.3 1597.9 Coniferous bog --- 8 Well Ref1M ------1592.7 1592.5 Coniferous bog --- 8 Well Ref1R ------1592.5 1592.4 Alder thicket 53 6 Well 7M 1558.4 1557.9 1558.4 1558.2 1597.8 Alder thicket 53 6 Well 7R 1557.9 1558.0 1559.1 1558.1 1615.4 Alder thicket 54 6 Well 6M 1597.8 1597.8 1597.4 1597.9 1597.8 Alder thicket 54 6 Well 6R ------1597.6 1597.8 Alder thicket 58 6 Well 9M 1565.8 1565.7 1565.8 1565.5 1558.2 Alder thicket 58 6 Well 9R ------1565.5 1558.4 Alder thicket --- 6 Well Ref2M ------1573.6 1573.6 Alder thicket --- 6 Well Ref2R ------1574.0 1573.7

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\Report\Appendix I Water elevation\Avg.water elevationAverage water elev. table revis 12

4 Ground Surface 0

-4

-8 Wetland Threshold -12

-16

-20 Depth to Water (inches)

-24

-28

-32

-36

/1/08 5 /31/08 /30/08 /30/08 /29/08 /28/08 /26/09 /25/09 /27/09 /26/09 /26/09 /25/09 /25/09 /24/09 /23/09 5 6 7 8 9 0/28/08 1/27/08 2/27/08 1 2 3 4 5 6 7 8 9 0/23/09 1/22/09 1 1 1 1 1

6R 6M 7R 7M 9R Ref2R

R = Recording well and "M" = Manual well Figure 1 Continuous lines without points 2008-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines WELLS IN ALDER THICKETS with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009.xls 12

4 Ground Surface 0

-4

-8

Wetland Threshold -12

-16 Depth to Water (inches) -20

-24

-28

-32

/1/08 5 /31/08 /30/08 /30/08 /29/08 /28/08 /26/09 /25/09 /27/09 /26/09 /26/09 /25/09 /25/09 /24/09 /23/09 5 6 7 8 9 0/28/08 1/27/08 2/27/08 1 2 3 4 5 6 7 8 9 0/23/09 1/22/09 1 1 1 1 1 1R 2R 3M 4R 4A 5M 8R 10R 11R 12R 13R 14R 15R 16R 18R 19R 19M 21R 22R Ref1R

R = Recording well and "M" = Manual well Figure 2 Continuous lines without points 2008-2009 WETLAND HYDROLOGY MONITORING DATA represent recording wells; lines WELLS IN CONIFEROUS BOGS with points represent manual wells PolyMet Mining Hoyt Lakes, Minnesota

P:\Mpls\23 MN\69\2369862\WorkFiles\WO 008 Corps Wetlands Permit\WetlandHydroStudy\2009Data\2009 PolyMet Well Data\Polymet_Figures_2009.xls