March 13, 2014 Michael Jimenez Minerals NEPA Project Manager Superior National Forest 8901 Grand Avenue Place Duluth, MN 55808 Doug Bruner Project Manager United States Army Corps of Engineers, St. Paul District 190 Fifth St. East St. Paul, MN 55101-1638 Lisa Fey EIS Project Manager Environmental Policy and Review Division of Ecological Services 500 Lafayette Road St. Paul, MN 55155 Mr. Jimenez, Mr. Bruner and Ms. Fey, Enclosed please find the comments of Great Lakes Indian Fish and Wildlife Commission (GLIFWC) staff on the Supplemental Draft Environmental Impact Statement (SDEIS) for the proposed PolyMet project. GLIFWC is an intertribal agency exercising delegated authority from 11 federally recognized Ojibwe (or Chippewa) tribes in Wisconsin, Michigan and Minnesota. 1 1 GLIFWC member tribes are: in Wisconsin -- the Bad River Band of the Lake Superior Tribe of Chippewa Indians, Lac du Flambeau Band of Lake Superior Chippewa Indians, Lac Courte Oreilles Band of Lake Superior Chippewa Indians, St. Croix Chippewa Indians of Wisconsin, Sokaogon Chippewa Community of the Mole Lake Band, and Red Cliff Band of Lake Superior Chippewa Indians; in Minnesota -- Fond du Lac Chippewa Tribe, and Mille Lacs Band of Chippewa Indians; and in Michigan -- Bay Mills Indian Community, Keweenaw Bay Indian Community, and Lac Vieux Desert Band of Lake Superior Chippewa Indians.
Comments of the Great Lakes Indian Fish and Wildlife Commission on the PolyMet SDEIS, March 2014.
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March 13, 2014 Michael Jimenez Minerals NEPA Project Manager Superior National Forest 8901 Grand Avenue Place Duluth, MN 55808 Doug Bruner Project Manager United States Army Corps of Engineers, St. Paul District 190 Fifth St. East St. Paul, MN 55101-1638 Lisa Fey EIS Project Manager Environmental Policy and Review Division of Ecological Services 500 Lafayette Road St. Paul, MN 55155 Mr. Jimenez, Mr. Bruner and Ms. Fey, Enclosed please find the comments of Great Lakes Indian Fish and Wildlife Commission (GLIFWC) staff on the Supplemental Draft Environmental Impact Statement (SDEIS) for the proposed PolyMet project. GLIFWC is an intertribal agency exercising delegated authority from 11 federally recognized Ojibwe (or Chippewa) tribes in Wisconsin, Michigan and Minnesota.1
1 GLIFWC member tribes are: in Wisconsin -- the Bad River Band of the Lake Superior Tribe of Chippewa Indians, Lac du Flambeau Band of Lake Superior Chippewa Indians, Lac Courte Oreilles Band of Lake Superior Chippewa Indians, St. Croix Chippewa Indians of Wisconsin, Sokaogon Chippewa Community of the Mole Lake Band, and Red Cliff Band of Lake Superior Chippewa Indians; in Minnesota -- Fond du Lac Chippewa Tribe, and Mille Lacs Band of Chippewa Indians; and in Michigan -- Bay Mills Indian Community, Keweenaw Bay Indian Community, and Lac Vieux Desert Band of Lake Superior Chippewa Indians.
Mr. Doug Bruner and Mr. Bill Johnson March 13, 2014 Page 2 Those tribes have reserved hunting, fishing and gathering rights in territories ceded in various treaties with the United States. GLIFWC’s mission is to assist its member tribes in the conservation and management of natural resources and to protect habitats and ecosystems that support those resources. As you know, the proposed PolyMet mine is located within the territory ceded in the Treaty of 1854. GLIFWC member tribes have expressed concern about the potential impacts of sulfide mining, whether those impacts occur within the 1854 ceded territory, in the 1842 ceded territory, which includes portions of Lake Superior, or the 1837 ceded territory. The following comments are submitted by GLIFWC staff with the explicit understanding that each GLIFWC member tribe or any other tribe may choose to submit comments from its own perspective. Staff remains, as they have for many years, primarily concerned about the scientific validity of the SDEIS with regards to modeling, water quantity, water quality, wetlands, and the assumptions regarding capture efficiencies and long term viability of the engineered structures. Staff also notes that comments and Major Differences of Opinion (MDO) developed for the Pre-draft Supplemental EIS have not been resolved and remain points of disagreement. Specifically, we are submitting comments on the following topics:
• Baseflow in the Partridge River Page 1 • Discharge from East Berm of Flotation Tailings Basin Page 3 • Revised MODFLOW Modeling of Discharge from East Berm Page 7 • SDEIS MODFLOW Modeling of Discarded Basin Design Page 10 • Perpetual Water Treatment Page 17 • Indirect Wetland Impacts Page 19 • Seepage Capture Efficiency Page 21 • Ability of Goldsim to Accurately Predict Contaminant Concentrations Page 28 • Mercury Page 28 • Wild Rice Standard Page 28 • Alternatives Page 29 • No Action Alternative Page 29 • Cumulative Effects Page 29 • Impacts from Rail Car Spillage Page 30 • Loss of High Biodiversity Significance Value Sites Page 30 • Financial Assurance Page 31
Mr. Doug Bruner and Mr. Bill Johnson March 13, 2014 Page 3 As always, we are willing and available to participate as the lead agencies review and revise the EIS document. Please feel free to contact me or Esteban Chiriboga in GLIFWC’s Madison office – (608) 263-2873 if you have any questions or need further information. Sincerely,
John Coleman
GLIFWC Environmental Section Leader Attachments cc. Tamara Cameron, Chief, Regulatory Branch, Army Corps Nancy Schuldt, Fond du Lac Water Projects Coordinator Ken Westlake, USEPA Region 5 Mike Sedlacek, USEPA Region 5 Neil Kmiecik, GLIFWC Biological Services Director Ann McCammon Soltis, GLIFWC Intergovernmental Affairs Director
Baseflow in the Partridge River
The importance of baseflow in understanding site hydrogeology is hard to overstate.
Unfortunately the quality of flow data collected at the Polymet site is poor and fraught with
uncertainty. Because there has not been a Polymet stream gage at the site and Northshore pit
dewatering has occurred into the Partridge at varying and uncertain times, all flow data from the
site is suspect. Simple upstream, at-site, and downstream flow measurement would have
provided higher quality data but was never collected by the applicant nor required by the state.
There have been several work-arounds to try to overcome the lack of good quality flow
data for the site. The latest has been the addition of 1 cubic foot per second (cfs) of flow to the
Goldsim modeling to account for Northshore pit dewatering. The mine site water modeling data
package very clearly states (SDEIS reference Polymet 2013i, pg 123 & 133) that the 1 cfs added
to Goldsim modeling was to account for constituents added to the Partridge by pit dewatering
from Northshore; It is not relevant to baseflow calculations nor is it relevant to determination of
aquifer conductivity or groundwater travel times.
In determination of baseflow, all GLIFWC's calculations have excluded Northshore
pumping from the calculation. The Dec. 17th MNDNR memo (Attachment A) also picked a
period when pumping for Northshore pit dewatering was not occurring so as to calculate true
baseflow. The 1 cfs added to Goldsim modeling of the Partridge, mentioned in various DNR
documents, is irrelevant to the calculation of baseflow and does not solve the modeling problems
in XP-SWMM, MODFLOW and by extension Goldsim. Some of the implications of incorrect
baseflow are highlighted on page 114 of the water modeling data package (March 2013), in our
memo of 2012-03-02, and in GLIFWC's baseflow summary of 2014-02-13 (Attachments B, C,
and D respectively).
Because the implications of baseflow are substantial when it comes to a basic
understanding of the mine site hydrogeology, all modeling of flow and by extension contaminant
transport must be re-calibrated to the higher baseflow numbers indicated by GLIFWC's analysis
1
of 2013-07-02 (Attachment E) and DNR's 2013-12-17 analysis (Attachment A). Page 114 of the
mine site Water Modeling Data Package makes it clear that re-calibration of the MODFLOW
model generates new conductivity values that are then fed into Goldsim. It states:
"The revised model calibration resulted in different optimized values for the horizontal
hydraulic conductivity of the surficial aquifer and bedrock, which are used to establish
the distribution of values used for the probabilistic groundwater flow path modeling
(Section 5.2.3.1)."
It is also clear that higher hydraulic conductivities for the aquifers result in faster contaminant
transport to points of evaluation.
Although baseflow assumptions have significant effects on Goldsim modeling, the
implication of re-calibrating the MODFLOW model go beyond the conductivities used in the
Goldsim modeling. Higher baseflows imply higher conductivities that imply faster and greater
groundwater flow rates. This affects:
1) The amount of water expected to flow into the mine pit as it is excavated.
2) The amount of drawdown of Partridge River flow that can be expected due to pit dewatering.
3) The amount of wetland dewatering that can be expected due to pit dewatering.
Given the uncertainty in baseflow numbers due to the poor quality flow data, it is
reasonable to re-calibrate the MODFLOW model to a range of values that included the
previously assumed baseflow and the newer, higher baseflow numbers.
2
Discharge From East Berm of Flotation Tailings Basin:
Significance:
The contaminant transport analysis at the Flotation Tailings Basin (FTB) does not include
any accounting for discharge through the east berm of the basin. There are 3 reasons why
discharge through the east berm will be enough to cause environmental concern:
1) the flow distance between the final FTB pond in cell 1E and the exterior of the east berm is
relatively short compared to flow distances from the pond to the north and west berms (SDEIS
Figure 3.2-29).
2) the east berm is underlain with 25-50 feet of conductive surficial material (SDEIS Figure
4.2.2.-12 and Figure 2 below).
3) the basin pond level is 1720 ft, the land elevation east of the basin is 1660 ft (Lidar data:
http://www.mngeo.state.mn.us/chouse/elevation/lidar.html). The elevation difference between
the pond and the adjacent land surface is substantial; 1720 ft - 1660 ft = 60 ft.
Because there has been no prediction of discharge from the east side of the FTB, there
was no flow path established or contaminant transport analyzed in the easterly direction. The
SDEIS is completely devoid of any mention or analysis of flow from the basin toward the east.
Receiving waters for the contaminated discharge would be wetlands adjacent to the basin, Spring
Mine Lake, Spring Mine Creek and wetlands to the north if a proposed stormwater drainage
swale is constructed.
Polymet Modeling of Flow from the Basin:
Polymet modeling with MODFLOW (RS13 Attachment A-6 2007; RS13B Attachment
A-6 2008; Polymet 2013j Attachment A 2011), for the FTB has prevented any discharge of basin
water to the east by erecting a no-flow boundary at the surface of the berm and at the ground
surface. This no-flow boundary is an artificial construct that has no basis in reality. In reality,
flow to the east will be controlled by the relative head pressures and the conductivity of the
materials in the FTB, beneath the FTB and in the berms.
GREAT LAKES INDIAN FISH AND WILDLIFE COMMISSIONP. O. Box 9 ! Odanah, WI 54861 ! 715/682-6619 ! FAX 715/682-9294
! MEMBER TRIBES ! MICHIGAN WISCONSIN MINNESOTA
Bay Mills Community Bad River Band Red Cliff Band Fond du Lac Band Keweenaw Bay Community Lac Courte Oreilles Band St. Croix Chippewa Mille Lacs Band Lac Vieux Desert Band Lac du Flambeau Band Sokaogon Chippewa
Via Electronic Mail / Original by Mail March 2, 2012
Memorandum
To: Thomas Hingsberger USACEErik Carlson Minnesota DNR
From: John Coleman, Environmental Section Leader
Re: Polymet model calibration to Partridge River low flows
The hydrologic models for the Polymet mine site have been calibrated to targets thatunder-represent true baseflow. Models should be calibrated to a strong set of observational data.Construction of the site’s basic hydrologic model to unrealistically low baseflows hasramifications for all the flow and contaminant modeling at the site.
Under-representation of Partridge River baseflow.
Review of the winter baseflow measurements and comparison to predictions made byXP-SWMM indicate that XP-SWMM substantially underpredicts baseflow (Barr June 9, 2011,Comparison of MDNR winter flow gauging to Partridge River XP-SWMM model). This hasramifications throughout the parameter sets being used in models characterizing hydrology at thePolymet mine site.
In the above referenced memo, Barr points out that the average measured baseflow atDunka Rd. was 5.0 cfs while the XP-SWMM predicted baseflow is 0.4 cfs. Even when dischargefrom Northshore Mining was taken into account, the average baseflow measured at Dunka is 4.3cfs while XP-SWMM predicts 0.42 cfs.
In its memo, Barr correctly points out that: "At all locations along the main stem of thePartridge River, the XP-SWMM-estimated baseflow is less than the MDNR-measured baseflow.The XP-SWMM model provides a conservative estimate of Partridge River baseflow for thepurposes of modeling water quality impacts (e.g., less dilution of loads from the Mine Site)."What is not acknowledged in the Barr memo is that calibration of hydrologic models to anunderestimate of baseflow produces models that characterize the groundwater hydrologic systemas moving an unrealistically small quantity of water.
Additional flow measures over the last 9 months on the Partridge River at the DunkaRoad (site SW-003) further support the position that baseflow predicted by XP-SWMM under-represents true baseflow. The least flow measured at the Dunka Road site was 3.8 cfs. Whilethere have so far been only 7 measurements taken at that site, the flow measured and the stagerecorded by the gauge do not appear to support XP-SWMM’s low baseflow predictions for theupper Partridge River.
Mis-calibration of groundwater flow models.
The calibration of the Modflow model to a Partridge River baseflow of 0.76 cfs predictedby XP-SWMM results in a model that moves very little water through the groundwater system. This can result in low predicted rates of inflow to the mine pit and slow movement ofcontaminants from sources (stockpiles or reflooded pits) to points of evaluation. More generally,an incorrect baseflow calibration target results in excessively low estimates of recharge andlikely incorrect estimates of horizontal and vertical conductivity. These hydrologic parametersare interrelated and getting one wrong, as appears to be the case with baseflow, will almostcertainly result in the other parameters being incorrectly estimated. Although there has been littlesensitivity analysis conducted in the Polymet modeling efforts, flow models tend to be sensitiveto these interrelated parameters.
Based on Modflow model calibration to a baseflow of 0.76 cfs and recharge values set at0.3 and 1.5 in/yr (see page 61 of Water Modeling Data Package Vol 1-Mine Site v9DEC2011.pdf and page 11 of RS22, Appendix B), some horizontal and vertical conductivities(K) were calculated by Barr using PEST (see Table 1 of Attachment B of Water Modeling DataPackage Vol 1-Mine Site v9 DEC2011.pdf). These K values are likely to be inaccurate sincethey are calculated with a model that is calibrated to a baseflow that appears to be almost anorder of magnitude too low. It is unlikely that any accurate predictions of water movement,transport of contaminant mass, or contaminant levels can be made when the characterization ofthe hydrologic system is so out-of-kilter.
Unusually low recharge and vertical K:
The low values used for recharge (0.3 and 1.5 in/yr) and the low wetland and till verticalK (0.0000033 ft/day [1.16X10-9 cm/s]) used in the Modflow model are a reflection of a modelconstructed and calibrated to move an unrealistically small amount of water through thehydrologic system. For context, note that engineered clay liners in landfills typically aim for1.0X10-7 cm/s hydraulic conductivity. I was unable to find any reference in the literature towetland soil vertical conductivity as low as is used in the Modflow model. The lower end of thespectrum I found for wetland soil vertical conductivity was 1X10-6 cm/s.
Our long standing concern that the mine site hydrologic models incorporate incorrectassumptions about recharge are supported by Fred Marinelli's comment on line 39 and elsewhereof: "Agency Responses MS and PS WP and Waste Characterization Data package V72-7-12.xls". His comment states that "A net infiltration (recharge) range of 0.3 to 1.5 in/yrrepresents 1.1 to 5.4 percent of mean annual precipitation (MAP). This range for local netinfiltration is unrealistically low for this area of the US." These low recharge values and the low
vertical K values are related to calibration of the Modflow model to low baseflow. UntilModflow, and by extension the other related models XP-SWIMM and GoldSim, are calibrated todata from the site (e.g. observed baseflow and an adequate number of observed heads) andincorporate reasonable recharge rates, the results from the models are unlikely to accuratelysimulate current or future conditions.
Recalibration of models needed:
The Modflow model, in particular, needs to be calibrated with targets based on observedbaseflow and observed well water heads. Calibration to projections by XP-SWMM, that appearto be incorrect, means that the fundamental characterization of the site hydrology is likely to befaulty. In the document referenced above (Agency Responses ...) Barr Engineering states thatmany hydrologic model parameters were “discussed as part of the IAP process and will not beconsidered further at this time.” While some parameters were discussed in the groundwater IAPprocess, the discussion was almost exclusively concerning water quality parameters, not flowmodel parameters such as recharge, baseflow and Kv and Kh. The focus on water qualityparameters to the near exclusion of hydrologic flow parameters is reflected in the GroundwaterIAP summary memo of June 2011. Groundwater flow modeling underpins contaminanttransport modeling and is interrelated to surface flow models. Without adequate vetting of flowmodel parameters and predictions, it is impossible to have confidence in predictions ofcontaminant movement and water quality.
Now that the hydrologic models have been more fully articulated by Barr and additionaldata are available, the models must be calibrated to observed baseflow and well water levels.This should include the new water level data from the newly installed mine site wells. PEST canthen be used to more reasonably estimate values for recharge and conductivity. The observedbaseflow and the PEST estimated recharge and conductivity values should then be used in theXP-SWMM and GoldSim modeling efforts. Modeling efforts that are based on faulty initialassumptions and not on field observations will not be able to reasonably predict impacts. Thecurrent Polymet modeling effort needs to be well founded on a strong base of observations of thephysical conditions at the site.
Thank you for considering this issue. Please contact me at 608-263-2873 if you havequestions.
Stream or river baseflow is a key variable in modeling because it is an indicator of the fundamental characteristics of the groundwater hydrology of a site. It is useful in helping to define the amount and speed at which ground water moves through the system.
Baseflow is usually calculated by measuring rates of stream flow at stream gauges to define low flow conditions for a site. During low flow periods the water found in a stream or river is often assumed to befrom groundwater. For the PolyMet project, the applicant did not install a stream gauge at the site. Instead they used data collected in the 1980’s from a stream gauge located 17 miles downstream. They then used a model (XP-SWMM) to extrapolate that information upstream to the area where the proposed pits would be located (mine site). The result of that extrapolation was a predicted baseflow rate of 0.5 cubic feet per second (cfs) in the Partridge River at the Dunka Road. As part of the process of XP-SWMM prediction of baseflow, periods were chosen when Northshore Mine was not discharging pit water into the upper partridge. Tribal Cooperating agencies have argued since 2008 that the baseflow rate predicted by XP-SWMM is unreasonably low and implies recharge to the groundwater system from precipitation that is not consistent with published literature.
Since the initial calculation of baseflow with XP-SWMM, which was used in the first DEIS, the MNDNR has conducted some limited measurements of flow in the Partridge River during winter. Winter flow is often used as a indicator of baseflow because during winter, it is too cold for rain and other surface water to enter a stream and thus it is assumed that the flow in the stream is a reflection of groundwater discharging to the stream bed. Those measurements suggested that baseflow was significantly higher than the 0.5 cfs predicted by XP-SWMM. GLIFWC staff have, on multiple occasions, provided calculationsof baseflow using alternative methods. Those analyses suggest that baseflow in the Partridge River at the Dunka Road was in the range of approximately 1.1 to 1.8 cfs.
In 2011 Tech Resources arranged for a stream gauge to be installed in the upper Partridge River which has allowed the MNDNR and GLIFWC to conduct calculations of baseflow using data obtained in the mine site area. The MNDNR calculations, released by MNDNR hydrologists in December of 2013, confirmGLIFWC’s position that baseflow was underestimated by the XP-SWMM model and is in fact closer to 1.5cfs rather than the previously predicted 0.5 cfs.
A confounding variable in the calculation of baseflow is the fact that the Northshore Mine discharges pitdewatering water into the Partridge River. This means that if flow measurements are taken during timeswhere Northshore is discharging their pit water, some of the water measured in the Partridge River maybe mistaken for baseflow. This is why both GLIFWC and MNNDNR's December 2013 calculations were careful to only use Partridge River flow data collected when Northshore was not discharging. It is from these times of no Northshore discharge, that the 1.5 cfs of baseflow was calculated.
Esteban
Typewritten Text
Attachment D
Baseflow is also highly related to the rate of recharge. Recharge is the process by which rainwater percolates into the ground and into the groundwater aquifers. Because baseflow has been underestimated, the recharge values used in the modeling are also unrealistically low. In fact, the recharge numbers calculated by the applicant and used in the SDEIS are not supported by published literature or data collected in the region.
On January 28th, 2014 the MNDNR released a statement claiming that Polymet modeling has accountedfor the difference between the 0.5 cfs XP-SWMM prediction and the more recent 1.5 cfs estimate of baseflow by adding 1 cfs to the Goldsim model. This explanation is incorrect because it confuses flow (which may be a mix of water from surface water sources and groundwater sources) with baseflow (which is water from groundwater sources only). The MNDNR statement further confuses water quantity models (XP-SWMM and MODFLOW) with the water quality model (Goldsim). Yes, a 1 cfs was added to the water quality model (Goldsim) to account for Northshore pit dewatering discharges but this does not relate to baseflow rates predicted and used in XP-SWMM and MODFLOW.
The difference between flow and baseflow can be demonstrated by the calculation of flow statistics for the stream gauge on the Partridge. The Q90 for the full data record from the gauge is approximately 2.5cfs. In other words, 90% of the time river flow was greater than 2.5 cfs at the gauge site. This is an indication of low flow in the Partridge and includes flow from all sources including groundwater and Northshore pit dewatering. On the other hand, the Q90 for periods when Northshore was not discharging pit water into the Partridge is approximately 1.5 cfs at the gauge site. This is an indication of flow derived from groundwater discharge to the partridge and is therefore considered an indicator of baseflow.
On a conference call conducted on February 12, 2014 the MNDNR confirmed that the 1 cfs was added toaccount for surface water pumping from Northshore in the Goldsim model (water quality) and not for any other purpose.
Why Is this Important?
Neither the direct winter field observations made by MNDNR (minimum of 3.4 cfs) nor the values calculated by GLIFWC and MNDNR from the stream gauge data (approximately 1.5 cfs), support the baseflow predicted by XP-SWMM at SW003 of 0.5 cfs (Water Modeling Data package Vol.1-Mine Site, ver12, p.130 and PSDEIS Table 5.2.2-12). XP-SWMM's low estimates of baseflow have been used in calibration of the MODFLOW model and thus influence many aspects of the site characterization and impact prediction, including pit inflow, dewatering impacts to the Partridge River and wetlands, water treatment needs, groundwater flow rates, contaminant transport times and concentrations, and contaminant dilution in the Partridge watershed.
A higher baseflow rate (1.5 cfs rather than 0.5 cfs) changes the conceptual understanding of how water passes through the groundwater aquifer. That change in understanding impacts predictions of how a mine would affect the aquifer. The conclusions that appear in the SDEIS of no significant impact to rivers, lakes and wetlands in the mine site are based on the concept that groundwater flows very slowly through the aquifer. The applicant has assumed, based on the 0.5 cfs baseflow, that wetlands and the
Partridge River are mostly isolated from the groundwater system and that little water will flow into the open pit from the groundwater system. Higher baseflows in the Partridge River, as demonstrated by GLIFWC's and MNDNR's analyses, strongly suggest that the wetlands and river are more connected to the groundwater aquifer, that mine pit inflow will be greater; and that groundwater travels through the aquifer at a faster rate.
Baseflow is used to formulate the model (MODFLOW) for calculating the amount of water that would flow into the open pits during mining. Therefore, the applicant has underestimated the amount of waterthey would need to pump out of the pits during mining and the amount of water they would need to treat prior to discharge. It is reasonable to assume that costs of treating this increased quantity of water,both short and long term may have also been underestimated.
Because the new baseflow numbers indicate that water moves through the ground faster than the SDEISassumes, the plume of contaminants from the reclaimed mine pits will likely reach points of evaluation faster and and in greater volume. Some have suggested that more water in the system would lead to more dilution of the PolyMet contaminant plume and thus produce less water quality impact. That is a naive, and possibly incorrect, view of a complex system. Higher baseflow relates to higher conductivity of the aquifer which has many impacts on flow and contaminant predictions. With increased flow through the aquifer, contaminant levels at compliance points could decrease, increase or stay the same. Only remodeling of the proposed project using realistic hydrologic inputs for baseflow and recharge can provide an adequate answer to this question.
Subject: Partridge River baseflow, draft analysis of new data suggest XP-SWMM estimate inaccurateFrom: "john.coleman" <[email protected]>Date: 7/2/2013 11:56 AMAttachments:Baseflow_calibration_v2012-03-02.pdf (32.2 KB), 2012-06-12_baseflow info re NorthMet EIS Mine
Site Hydrology Teleconference.eml (2.8 KB), 2012-06-18_watershed ratio predicts baseflow of 1.2cfsat SW-004 Re Model Calibration, NorthMet EIS.eml (3.1 KB), 2008-09-28_further comments onRS22 AppenB Draft-03.htm (4.5 KB)
Re: Partridge River baseflow, draft analysis of new data suggest XP-SWMM estimate inaccurate
We remain concerned that the basic hydrology of the mine site is mis-characterized as being very non-conductive.The baseflow in the Partridge is a fundamental parameter to which many flow and contaminant transport models arecalibrated. Unfortunate the baseflow at the site used in impact prediction is an estimate make by XP-SWMM. XP-SWMM appears to do a poor job of predicting baseflow at the mine site, possibly because it is based on a data setcollected 17 miles downstream. As we note in our recently submitted PSDEIS comments, the MDNR winter flow measurements in the PSDEIS(Table 4.2.2-9) indicate substantially higher baseflow in the Partridge than predicted by XP-SWMM. This is true evenwhen the flow data is corrected for any possible Northshore (NS) discharge to the Partridge by subtracting thefarthest upstream measurement from measurements taken farther downstream. Even more compelling than the winter MDNR flow measurements is the flow data that has been recorded at theDunka Road gage over the last 2 years. I have again calculated some statistics on the flow measurements taken at thePartridge River & Dunka Road, also known as monitoring site SW003. (http://www.dnr.state.mn.us/waters/csg/site_report.html?mode=get_site_report&site=03155002)Earlier comments on this topic are attached and previous analysis was submitted to the lead agencies by email on2012-06-12, 2012-06-18, and on 2008-09-28 (attached).
The stage and flow values measured by stream gage are available at 15 minute intervals. Based on 66,581 stagerecords collected between May 2011 and April 2013 and the DNR rating curve, I found: Q90 at SW003 = 2.32 cfs (90% of the time flow was greater than 2.32 cfs) Q90 is sometimes used as an indicator ofbaseflow
Using 586 daily average flows from 2011-05-26 to 2012-12-31 calculated by the DNR and accounting for winter iceconditions, I found:Q90 at SW003 = 1.9 cfs
Given that Northshore Peter Mitchel (PM) pit intermittently discharges to the Partridge River, I also analyzed 3months in 2011 (Jul,Aug,Sep) and 3 months in 2012 (Feb,Mar,Apr) when Northshore (NS) discharged zero (0)gallons into the Partridge River. Based on average daily flows calculated by the DNR:In the 3 months of no NS pit discharge in 2011 Q90 at SW003 = 1.8 cfsIn the 3 months of no NS pit discharge in 2012 Q90 at SW003 = 1.1 cfs
Given that both these 3-month periods are typically low flow times, it seems that a baseflow estimate for site SW003of 1 - 2 cfs would be reasonable.While analysis based on only 6 months of flow data is not ideal, it should be noted that the XP-SWMM model iscalibrated to only 2 months when Northshore did not discharge to the Partridge in 1985 (PSDEIS page 4.2.2-44, 1stparagraph).
Neither the direct field observations (minimum of 3.4 cfs) nor the values calculated from the DNR rating curve,support the baseflow predicted by XP-SWMM at SW003 of 0.51 cfs (Water Modeling Data package Vol.1-MineSite, ver12, p.130 and PSDEIS Table 4.2.2-8). XP-SWMM's low estimates of baseflow are used in calibration of theMODFLOW model and thus influence many aspects of the site characterization and impact prediction, including pitinflow, dewatering impacts to the Partridge River, water treatment needs, groundwater flow rates, contaminanttransport times and concentrations, and contaminant dilution in the Partridge watershed.
Although it is now an unfortunate time in the NEPA process to try to adequately characterize basic site hydrology, ifappears that predictions of effects of the project may be far from accurate. It is not easy to say how themis-characterization of river baseflow would affect compliance predictions because, although more baseflow mightmean more dilution of contaminants, it could also mean transport of greater quantities of pollutants to the river andmore drawdown of the Partridge River. We have repeatedly asked that the data at the Dunka Road gage be formallyanalyzed for baseflow as a check of the accuracy of the XP-SWMM modeling. If that analysis indicates that theXP-SWMM predictions under-represents baseflow, as our draft analysis suggests, that result should be incorporatedinto all project model calibration and prediction.
Thank you in considering this issue when revising the SDEIS.
--John Coleman, Madison Office of the Great Lakes Indian Fish & Wildlife CommissionU.W.-Madison Land Information and Computer Graphics Facility550 Babcock Drive, Room B102Madison, WI 53706608-263-2873 or [email protected]