This is a comprehensive, clearly-written document summarizing potential biophysical and socioeconomic impacts of copper-nickel mining in Minnesota. Special attention is paid to impacts on water resources. Relevant sections are reproduced in their entirely below, not only for historical interest but because of predictive power. Summary: "The Minnesota Environmental Quality Board's Regional Copper-Nickel Study is a comprehensive technical examination of the environmental, social, and economic impacts associated with the potential development of copper-nickel sulfide mineral resources of the Duluth Complex in northeastern Minnesota. This executive summary of the 5 volume, 36 chapter report presents some of the major findings of the Study, but in order to get a complete picture of the complex issues associated with exploiting this valuable mineral resource, the entire document should be examined. In addition to this report over 180 technical reports, extensive environmental monitoring data files, special sample collections, and other information resources were compiled by the Study" (n.b. these documents were not reviewed as part of this current desk review). Consistent with directions from the Minnesota Legislature, the Regional Copper-Nickel Study presents technical findings but does not make policy recommendations based on these findings." "To allow for a discussion of the potential environmental and socio-economic effects of copper-nickel development, an area of approximately 2100 square miles was designated as the Regional Copper-Nickel Study Area (or simply, the Study Area). This area contains Virginia in the southwest corner and Ely in the northeast corner. The major copper-nickel deposits of interest occur along the Duluth Gabbro Contact, in a band three miles wide and fifty miles long (the Resource Area); however, additional deposits may extend beyond this band. The Water Quality Research Area, which includes the complete watersheds of 14 streams of interest, is shown in Figure 2. Waters north of the Laurentian Divide are part of the Rainey River Watershed, which includes a portion of the Boundary Waters Canoe Area, and whose waters eventually drain into Hudson Bay and the North Atlantic. Waters south of the Divide are a part of the St. Louis River Watershed which drains into Lake Superior and eventually into the Atlantic Ocean via the St. Lawrence River.” "Historically, the exploitation of base metal sulfide resources (such as copper-nickel resources) throughout the world has been accompanied by the significant degradation of the quality of water resources and the destruction of aquatic and terrestrial biota m the vicinity of such developments. Acid mine drainage, toxic heavy metals contamination, erosion, sedimentation, increased salinity, and other water pollution problems associated with mining were common. The nonferrous minerals smelting industry (principally copper, lead, and zinc) has also been a major source of manmade air pollutants. Until new technology has been developed to minimize many of these impacts, adverse impacts of past practices continue to cause close scrutiny of new mining proposals.” Water Quantity (Volume 3-Chapter 4). "Surface water is abundant in the Water Research Study Area due to high surface runoff. Average annual runoff in the region is about 10 inches. The Water Research Study Area includes 360 lakes larger than 10 acres, in addition to 14 small rivers and streams. Nearly 75 percent of the Water Research Study Area, and an even larger proportion of the surface water is north of the Laurentian Divide. North of the Divide, lakes are more numerous and larger, and the volume of stream flow is greater because a larger area is being drained. Because some of these waters are inside the BWCA, not all of the water north of the Divide is directly available for use. Annual average flow for 12 streams studied by the U.S. Geological Survey for the Study ranged from 23 to 1,027 cubic feet per second (cfs). High flow generally occurs after heavy precipitation and following the spring snowmelt. Average low flow for seven days is 2 to 186 cfs compared to an average high flow of 87 to 4,763 cfs. Ground water yield is generally low, limited by the low permeability of the Area's bedrock and the often shallow overlaying glacial deposits. Yields generally average less than 5 gallons/minute. Three relatively small areas have high volume aquifers yielding up to 1,000 gallons/minute: the Embarrass Sand Plain, the Dunka River Sand Plain, and the local fractured and leached bedrock areas in the Biwabik Iron Formation.” "Current industrial use of surface water is primarily for electric power generation. Mine-pit dewatering is the greatest groundwater use. At current levels, water use does not cause significant impacts on the region's water resources, although withdrawal from some streams must be reduced during low flow. Surface water, including some of the large on-channel lakes (e.g. Birch Lake), could supply large water users, al though storage may be required for certain streams. The Embarrass River Valley aquifer is the only identified groundwater source in surficial materials that could supply large water users.” Water Quality (Volume 3-Chapter 4). "Because of the large number of streams and lakes in the Study Area, the value of high quality water which supports a significant recreational and wilderness resource of the state and the nation, and the recognized historic relationship between base-metal mining and water pollution, a major responsibility of the Regional Copper-Nickel Study was the collection of baseline surface and ground water quality data (note: data tables and figures and not reproduced). "The quality of the region's water resources is generally very good except for several streams with watersheds affected by extensive taconite mining activities, and for groundwater either from glacial till or wells near the Duluth Gabbro Complex sulfide mineralization. Streams draining largely undisturbed watersheds can be described as containing soft water, having low alkalinity, low total dissolved solids, low nutrients, high color, very low trace metals concentrations, and low fecal coliform counts.” "Streams draining disturbed watersheds (Partridge, Embarrass, Upper St. Louis rivers south of the Laurentian Divide, and the lower Dunka River and Unnamed Creek north of the Divide) would be considered to contain moderately hard to hard waters, with elevated dissolved solids, nutrients, and trace metals concentrations relative to undisturbed watersheds. Color and fecal coliform concentrations are not significantly different in the two watershed classifications. Most water quality parameters tend to be much less variable in undisturbed streams as compared to disturbed streams. The quality of the lakes studied is variable though similar to the quality of undisturbed streams. However, lake values may be less meaningful for determining baseline concentrations than values in streams because of the limited number of samples.” "In general, concentrations of most chemical constituents are higher in the groundwater than in streams and lakes of the area. Groundwater from wells proximate to the Duluth Gabbro contact were found to have higher levels of trace metals and sulfate than wells located at a distance from the contact. Phosphorus and nitrogen are the major nutrients in aquatic systems. Concentrations of both nutrients in study streams are at the low end of the range of values for U.S. streams. Variations in nutrient levels exhibited no clear trends between headwater and downstream stations or between small and large watersheds. Highest concentrations of nitrogen were found downstream from mining operations where blasting compounds containing nitrogen are used. In lakes, nutrient parameters are closely associated with the activities of aquatic organisms. Higher levels of available nutrients encourage greater biological productivity. The ratio of nitrogen (N) to phosphorus (p) can be used to evaluate which of these nutrients limits algal productivity. Lakes with a N:P ratio greater than 14 are considered to be limited by phosphorus. Within the Study Area, median N:P ratios ranged from 14 to 60, and half the lakes studied had ratios greater than 25. Overall concentrations of both nutrients were at the low end. Median values for both nutrients were higher south of the Laurentian Divide than north of it. The most productive lakes were all headwater lakes, usually shallow, and surrounded by extensive bog and marsh areas.” "A major concern related to copper-nickel development is levels of heavy metals in surface waters. At background stream stations, copper, nickel, and zinc levels are generally very low, with median concentrations of copper and zinc in the range of 1-2 ug/liter and nickel around 1 ug/liter. Other trace metals of biological importance (As, Cd, Co, Hg, and Pb) have median concentrations significantly below 1 ug/liter. There is little variability in the levels of arsenic, cobalt, cadmium, mercury, titanium, selenium, and silver across almost all surface waters monitored. As expected, iron, manganese, copper, nickel, zinc, lead, fluoride, and chromium concentrations in streams are significantly higher in disturbed watersheds than in undisturbed areas. The dynamics of metals in lakes are somewhat different from those in streams because the large surface area of bottom sediments with their varying oxidation reduction potentials complicates the picture. Lakes can act as sinks for metals (as is the case with iron at Colby Lake) so that the chemistry of out flowing waters is different from that of inflowing waters. Large lakes may exhibit variability in the concentration of metals within the lake itself (as is the case with nickel in Birch Lake). Similar to streams, iron,' aluminum, and manganese were the most elevated metals in the Study Area lakes. Copper, nickel, and zinc have median levels between 1 and 2 ug/l, whereas arsenic, cobalt, and lead have median levels of 0.6,0.4, and 0.4 ug/l, respectively. Cadmium levels were an order of magnitude (10 times) lower than those for arsenic, cobalt, and lead. The greatest variabilities in concentrations were exhibited by manganese, zinc, cadmium, and aluminum, with arsenic the least variable metal.” "Water quality standards and criteria for many parameters have been adopted or are proposed for adoption by the Minnesota Pollution Control Agency or the U.S. Environmental Protection Agency (EPA). Recommended levels for cadmium, color, copper, iron, lead, manganese, mercury, nickel, nitrogen (as N02 + N03), pH, specific conductance, sulfate, and zinc were exceeded in one or more of the streams monitored. In most cases, these elevated levels occurred in Unnamed Creek, which is affected by mining (see discussion of Unnamed Creek below). The region's streams and lakes have naturally high color levels.” "All streams which were monitored exceeded the EPA water quality criteria for mercury (0.05 ug/liter). The median concentration of mercury for all streams monitored was 0.08 ug/liter with a range of 0.01-0.6 ug/liter. Standards for mercury are based on U.S. Food and Drug Administration guidelines for edible fish. High mercury levels have been found in fish from some of the area's lakes and streams. Because acid precipitation is a potential problem, the quality of precipitation in the Study Area was monitored at several sites. Seventy-seven percent of the samples (41) had a pH less than 5.7, which means that most of the precipitation measured can be considered acidic. Fifty percent of the samples had a pH of 3.6 to 4.4. The geometric mean pH of samples collected in the area was 4.6. These values are comparable to, or even less than values measured in areas of the world where ecological damage has already occurred. Measurements by the Regional Study indicate that the present annual sulfate deposition rate (wet plus dry) across the Study Area is from 10 to 20 kg/ha/yr (9 to 18 lbs/ acre/yr). Atmospheric dispersion modeling indicates that regional sources of S02 are not major contributors to depressed acidity of precipitation and suIfate deposition in the region. This in turn indicates that out-state and out-of-state sources, possibly as far away as St. Louis, Chicago, and Ohio Valley areas, are likely the major cause of acid rain and sulfate deposition in northeastern Minnesota.” "If the patterns of increasingly acidic precipitation continue, it is likely that many of the poorly buffered small streams will have noticeable decreases in aquatic populations (such as fish) during and following spring melt.” "Stream systems are very sensitive because the flush of water from spring snowmelt can represent a majority of the water that the stream may carry through the whole year. Recovery from these episodes may be expected to be fairly rapid (i.e. within months) unless or until the sources of recolonizing organisms are themselves affected (i.e. well buffered lakes or large unaffected streams). Recovery would be very slow once the source areas are affected. The effects of acid precipitation on vegetation range from damage to leaves to increased susceptibility to disease and death (see Volume 4-Chapter 2). A direct causal relationship between acid precipitat ion and reduced forest productivity measured by growth remains to be demonstrated. However, research suggests that acid precipitation is probably a cause of reduced forest growth. Because acidic precipitation and sulfate deposition are primarily related to air pollution sources outside the region and are projected to increase significantly over the next 10-20 years, acidification may represent a serious threat to the ecosystems of northeastern Minnesota, even if copper-nickel development does not occur. Long-term changes in the aquatic communities are probably already underway due to the general decrease in the pH of precipitation and thereby of surface waters in the Study Area. Because the decrease in pH will likely be slow, measurement of biological effects would require intensive long-term monitoring. During this period of decreasing pH, the overall productivity and diversity of the aquatic communities can be expected to decrease.” "One crucial parameter that was monitored is the water's buffering capacity-- its ability to regulate pH changes due to acid inputs from atmospheric deposition or leaching. The resistance to pH change is a function of the type of acid input (i.e. strong or weak acids) and the type of chemical components in the receiving water which can assimilate or bind the hydrogen ions. Calcite saturation indices (csr) were calculated for all study lakes and 30 lakes in the BWCA to measure this buffering capacity. Lakes with a csr less than 3.0 are well buffered; lakes with an index between 3.0 and 5.0 are poorly buffered with the possibility that acidification may already be occurring; and an index over 5.0 indicates lakes with little or no buffering ability and a strong possibility that severe acidification has already occurred.” "The poorly buffered lakes in the region are with few exceptions headwater lakes. This may be explained by the fact that buffering is a function not only of atmospheric processes, but also of watershed geology. The chemistry of headwater lakes often reflects that of precipitation, with watershed contributions to lake chemistry assuming secondary importance. As one proceeds from headwater to downstream lakes 1.U the Study Area, the ability of the lakes to assimilate hydrogen ions generally increases. Headwater areas of the region (which include half the BWCA lakes studied) are generally not well buffered and have limited capacities to assimilate existing acid loadings. Some of the lakes sampled during the study which may be the earliest to be affected by acidic precipitation include: Clearwater, August, Turtle, One, Greenwood, Perch, and Long lakes. These lakes have Calcite Saturation Indices above 3.0. Headwater streams are generally poorly buffered, in part because their water quality is also dependent upon the quality of precipitation.” "Two unique water quality conditions have been identified in the Study Area which are directly related to the presence of copper-nickel sulfide mineralization. In one of these cases, human disturbance of this mineralization has accelerated the chemical/physical weathering (leaching) of this material. Filson Creek, located in the northeastern part of the Study Area adjacent to the BWCA, flows naturally over exposed mineralized gabbro. Within the Filson Creek watershed, total concentrations of copper and nickel 10 the year 1977 generally increased from headwater locations to Filson's point of discharge into the South Kawishiwi River. Total nickel concentrations measured in Filson's headwaters were, except for one sample, less than 1 ug/liter, while the mean nickel concentration near the mouth of the watershed was 3 to 5 ug/liter. The smaller copper and nickel concentrations at Filson Creek headwater locations reflect the smaller percentage of sulfide bearing material in the till and the greater distance from the mineralized contact zone. The elevated metal values measured in Filson Creek may not be completely due to natural weathering of sulfide minerals. Prior to 1977, considerable mineral exploration activities occurred, including the taking of a bulk surface mineral sample. Subsequently, a small volume surface discharge was discovered at the foot of the bulk sample site with elevated metals levels (10,000 to 13,000 ug/l Ni, 360 to 1,000 ug/l Cu, and 190 to 5300 ug/l 2n). This discharge enters a small tributary of Filson Creek and raises the nickel and copper concentrations by about 9 ug/l and 5 ug/l, respectively. This change in trace metal concentrations is not sufficient to result in measureable biological changes in the Creek.” "In the other unique case, a small watershed (Unnamed Creek) which drains into Birch Lake at Bob Bay contains several wastepiles containing mineralized gabbro from a nearby taconite mining operation (Erie Mining Company's Dunka Pit). The large surface area of the waste rock facilitates the chemical weathering process. Surface seeps containing elevated concentrations of sulfates and trace metals (especially nickel) are present. The seeps flow into Unnamed Creek where the influence of this disturbance on water quality is obvious. Median nickel levels in Unnamed Creek were 85 ug/l, compared to 1 ug/l in undisturbed streams (Table 4). Extensive field studies conducted in this watershed have demonstrated that extensive disturbance of the mineralized gabbro without corrective mitigation can result in significant water quality degradation. The magnitude of the potential impacts in this specific case is largely mitigated by natural chemical processes involving adsorption, chemical complexation, and precipitation due largely to the presence of a bog in the watershed. The metal concentrations measured at Bob Bay would be significantly higher if not for the effect of the bog. However, the bog is showing some signs of stress and its beneficial effect on water quality may not continue for long.” Environmental Impact Assessment: Water Use "Water is required in significant quantities as a transport medium for the ore during concentration and for tailing disposal. Additional water is required in the smelting and refining phase for cooling and other purposes. Precipitation partially offsets the major water losses coming from evaporation losses coming from evaporation from tailing basins and water trapped between particles in tailing basins. However, fresh makeup water (estimated to average 0.76-1 b ill ion gallons per year) will be required for all three integrated copper-nickel development models (Volume 2-Chapter 5). Water requirements will vary significantly on a seasonal and annual basis.” "A good water management system is designed to manage and store runoff and seepage on the site (around waste piles, tailing basins, and elsewhere). The specific site and the design of the system will determine whether periodic discharges of waste water will be necessary during periods of above average precipitation. Because of the fairly continuous demand for water and the varying supply of water in lakes and streams in the area, it is estimated that significant water storage (10,000 to 15,000 acre-feet) will be necessary for use during dry periods. This water storage could be supplied by the tailing basin and/or reservoirs. Storage requirements for makeup water supply and containment of polluted water could increase land requirements by 2,000 to 3,000 acres.” "Increased demand for water could become a source of conflict if waters tributary to the BWCA are appropriated for copper-nickel development and if the waters are also diverted for taconite development, such as the Upper St. Louis and Partridge river watersheds. These issues could be considered prior to issuance of a DNR permit which s required for water appropriation. However, if both taconite expansion and copper-nickel development proceed in northeastern Minnesota, a regional comprehensive water management plan and perhaps a cooperative industrial water supply system may need to be considered.” "Quality of tailing water during the operating phase 1S primarily controlled by the concentrating process water. This water is largely recycled and should not be a significant heavy metal pollution source. Seepage can also be collected and recycled if necessary. Elevated levels could occur during the post-operating phase or if more sulfides are deposited in the basin than projected. Local variation in ore mineralogy could result in pockets of tailing having much higher sulfide concentrations which could cause localized leaching problems. Due to limited research on tailing water quality, the unknowns involving the quality of runoff and seepage from a tailing basin are greater than those associated with waste rock piles and create another source of significant risk involving future copper-nickel water management decisions.” "Mine dewatering can also contribute heavy metals, the amount depending upon the quantity of water from precipitation and groundwater sources that must be removed and the metal sulfide content of the mine. No precise conclusions can be made about expected levels of heavy metal release from this source. Smelter and refinery waste water 1S not as significant an issue as waste piles. Production of these waste waters 1S dependent on facility design and operation, and there appears to be no significant post-operational concerns.” "Treatment methods are available to reduce heavy metal concentrations in these waste waters to levels where biological impacts are not expected. Effluent water quality models for impact assessment purposes were developed (Volume 3-Chapter 4) based on the best data available from field and laboratory results, but this information is not sufficient to allow precise statements on the quality of water produced from copper-nickel water pollution sources or on the effectiveness of reclamation practices for specific effluent parameters (e.g. suIfates, trace metaIs, processing reagents). For example, information strongly suggests that runoff from waste piles will contain elevated heavy metals and dissolved solids concentrations as compared to background surface water quality. Heavy metals could be 500 to several thousand times higher than natural water quality levels and sulfates could be ten to several hundred times higher.” "These models reflect an assumption that acid mine drainage problems will not occur because of the natural buffering capacity of the waste materials. If this assumption IS wrong and acid conditions do occur, then projections of water pollution will be significantly underestimated because, as the pH becomes acid, there are dramatic increases in the amount of heavy metals leached from the waste significantly affects whether a metal will be in an aqueous phase (and highly mobile) or in a solid phase.” "Treatment of large amounts of runoff to remove heavy metals to existing background levels may be prohibitively expensive. Additional research is necessary in order to make accurate predictions about effluent quality and the effectiveness of various controls. Cost and time constraints will likely require that the first mining activities proceed without this predictive capability.” Heavy metals have adverse effects on aquatic organisms, the extent depending upon the type of metal (or combination of metals), organism tolerance, and water chemistry (Volume 4-Chapter 1). For example, cold water fisheries are generally more susceptible to heavy metal pollution than warm water fisheries." No mention is made of impacts on wild rice stands.
Minnesota Environmental Quality Board.
The Minnesota Regional Copper-Nickel Study 1976-1979, Volume 1: Executive Summary.
Retrieved from the University of Minnesota Digital Conservancy,
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