NATURALLY OCCURRING ACID ROCK DRAINAGE AND IMPACTS TO THE UPPER RAPID CREEK WATERSHED NEAR ROCHFORD, SD

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1 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) 83 NATURALLY OCCURRING ACID ROCK DRAINAGE AND IMPACTS TO THE UPPER RAPID CREEK WATERSHED NEAR ROCHFORD, SD Scott L. Miller and Arden D. Davis Department of Geology and Geological Engineering Scott J. Kenner and A.J. Silva Department of Civil and Environmental Engineering South Dakota School of Mines and Technology Rapid City, SD ABSTRACT Naturally occurring acid rock drainage has historically and is presently negatively affecting reaches of North Fork Rapid Creek, North Fork Castle Creek, and Castle Creek in the Upper Rapid Creek Watershed of the Black Hills near Rochford, South Dakota. Samples were collected and assessments were made for these creeks during 2002 and The acid rock drainage has a ph of approximately 2.5 to 3.5 and contains high concentrations of iron, aluminum, and sulfate. Uncontaminated surface water has a ph of approximately 7 to 8.5 and contains high concentrations of calcium, magnesium, and bicarbonate. When the acid drainage mixes with uncontaminated water of these creeks, natural buffering reactions occur, causing iron and aluminum hydroxides to precipitate. Surface water chemistry from upstream to downstream was little affected by the introduction of the acid rock drainage. However, the metal hydroxide precipitates significantly affect the streambed and the fisheries habitat. The metal hydroxide precipitate coats the stream bottom and cements the sediments together, negatively affecting vegetation and macroinvertebrate habitat. Some precipitate is transported downstream, degrading the stream habitat for several hundred meters. Much of the plant and animal life in these areas is stressed, leaving some stream reaches devoid of all life and destroying the fisheries habitat. Natural chemical reactions cause the negative effects to attenuate, restoring the stream s water quality and habitat within approximately one to two km downstream. Keywords Acid rock drainage, iron bog, fisheries habitat

2 84 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) INTRODUCTION Naturally occurring acid rock drainage is actively discharging from iron bogs into North Fork Rapid Creek, North Fork Castle Creek, Castle Creek, and some unnamed tributaries. Iron bogs can develop where ground water discharges at the land surface in the form of springs. The discharge is acidic, contains high concentrations of iron, aluminum, and sulfate, and negatively affects the environment. The Upper Rapid Creek Watershed is in the north-central Black Hills of South Dakota, near the small community of Rochford, approximately 60 km northwest of Rapid City (Figure 1). This research was part of a larger project to Figure 1. Location of North Fork Rapid Creek and generalized geologic map of the Black Hills, South Dakota (modified from Dewitt and others, 1989).

3 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) 85 assess the Upper Rapid Creek Watershed for the South Dakota Department of Environment and Natural Resources, the South Dakota Department of Game, Fish, and Parks, and the Black Hills Flyfishers (in press). HYDROGEOLOGIC SETTING The geology of the Upper Rapid Creek Watershed consists of Precambrian metamorphic rocks overlain with younger Paleozoic sedimentary rocks to the north and west (Figure 1). Precambrian rock types include phyllite, schist, banded iron formation, chert, and quartzite (DeWitt and others, 1989). In the western Black Hills, the Paleozoic rocks are nearly flat lying and consist of, from older to younger, the Deadwood (sandstone), Winnipeg (shale), Whitewood (dolostone and limestone) formations, the Englewood and Pahasapa (Madison) limestone, and dolostone, and the Minnelusa Formation. North Fork Rapid, North Fork Castle, and Castle creeks are gaining streams, where flow increases downstream due to ground water discharging from bedrock and alluvium. The bulk of surface water in all three streams originates as spring flow from the Pahasapa limestone (Carter and others, 2002). Not surprisingly, uncontaminated water quality in these streams is similar to ground water quality of the Pahasapa (Madison) Limestone in the western Black Hills. Surface water in these three creeks and ground water from the Pahasapa limestone typically contain calcium, magnesium, and bicarbonate with trace levels of inorganics (e.g., chloride, fluoride, potassium, sodium and sulfate) and metals (e.g., aluminum). The ph is typically 7.5 to 8.5. Water quality from Precambrian rocks varies greatly but generally contains iron, aluminum, and sometimes sulfate. Acid rock drainage may develop where pyrite is abundant in the Precambrian bedrock. Precambrian rock does not always contain abundant pyrite, therefore, not all ground water and spring discharge from the Precambrian rock is high in acid and metals. Acid rock drainage occurs both naturally and due to anthropogenic disturbances, primarily mining. Most acid rock drainage is found at mine sites where it is commonly referred to as acid mine drainage. Acid rock drainage results from the interaction of sulfide minerals with oxygen and water. Iron-oxidizing bacteria often catalyze these reactions. Pyrite (FeS 2 ) is the most abundant and widespread sulfide mineral and is the primary source for acid rock drainage. Pyrrhotite (FeS) is less common than pyrite and is a minor source material for acid rock drainage (Deer and others, 1980). In this region, the Precambrian metamorphosed sedimentary rocks most likely originated as marine shale under reducing conditions and contain abundant finely disseminated pyrite. This microscopic pyrite is more reactive than larger crystals as the finer crystals have a higher surface area to volume ratio (PDEP, 1998). Figure 2 shows a reach of Castle Creek strongly affected by acid drainage and Figure 3 shows both aluminum and iron hydroxide precipitates at the confluence of an unnamed tributary with Rapid Creek. Iron bogs form where iron-rich, acidic ground water discharges to the land surface as springs or directly into the creek along the banks or within the chan-

Note reach is devoid of most life in channel. Figure 3.

4 86 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) Figure 2. Iron hydroxide precipitate coating stream substrate on reach of North Fork Rapid Creek. Note reach is devoid of most life in channel. Figure 3. Confluence of acid rock drainage and uncontaminated stream. Note red-orange iron hydroxide and white aluminum hydroxide precipitates.

5 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) 87 nel. This spring water comes from a subsurface reducing environment, is acidic (ph approximately 2.5 to 4), and contains high concentrations of iron, aluminum, and sulfate. At the surface, the discharged water is exposed to oxygen from the atmosphere and mixes downstream with well-oxygenated, unpolluted surface water with ph approximately 7 to 8. The resulting mixture has a ph in the range of approximately 6.5 to 7.5 and is nearly saturated in oxygen. These conditions cause the reduced iron (i.e., Fe 2+ or Fe (II)) and aluminum in solution to oxidize. The neutral water is over-saturated in iron and aluminum causing iron and aluminum hydroxides to precipitate, flocculate and accumulate at the spring and along the bottom of the channel. These chemical reactions occur quickly and precipitates can be observed immediately at springs and where acidic water mixes with surface water. The oxidized iron precipitates discolor the water light red-orange. Over longer periods of time (i.e., decades to millennia), the metal hydroxides accumulate, dewater and harden through diagenesis, cementing the stream sediments together. Iron-cemented conglomerate was encountered along streams, flood plains, and stream terraces indicating historic discharges of acid rock drainage in this area. Iron bog deposits contain as much as 50-percent iron. Because of their high iron content, many of the larger bogs in this area were mined for iron from the early 1900s up through the 1950s (USGS, 1975). STUDY METHODS AND RESULTS Field and analytical water quality data collected quarterly during 2002 and 2003 were used to characterize the surface and ground water quality in North Fork Rapid Creek, North Fork Castle Creek, and Castle Creek watersheds. Field data included ferrous (Fe 2+ ) iron concentration, redox potential (Eh), ph, dissolved oxygen, temperature, and specific conductance. Analytical data included general water chemistry consisting of major and minor ions and several metals. Analyses were performed by an EPA-certified laboratory. Selected water quality data collected from Upper Rapid Creek watersheds during 2002 and 2003 are summarized in Table 1. Concentrations of water quality parameters for surface water and spring and ground water vary by up to two orders of magnitude. Piper trilinear diagrams (Piper, 1944) and Stiff diagrams (Stiff, 1951) were used to classify water quality type and visually inspect and compare water quality based on major ions. Ground water and bog water were calcium-magnesium-sulfate rich water. Surface water and Pahasapa limestone water were calcium-magnesium-bicarbonate rich water. Using the U.S. Geological Survey geochemical model, phreeqc (version 2.7) and visible and near infrared reflectance spectroscopy, precipitates appear to be iron hydroxide or yellow boy (Fe(OH) 3 ), geothite (FeO OH), limonite (FeO OH nh 2 O), hematite (Fe 2 O 3 ), jarosite (KFe 3 (SO 4 ) 2 (OH) 6 ), and an aluminum hydroxide, gibbsite (Al(OH) 3 ) or alunite (KAl 3 (SO 4 ) 2 (OH) 6 ).

6 88 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) Table 1: Summary of Selected Water Quality Data from Upper Rapid Creek Stream Water Quality Spring Discharge and Ground Water Quality Total Iron (mg/l) ND Ferrous Iron, Fe 2+ (mg/l) ND ~2 ~3 7 Ferric Iron, Fe 3+ (mg/l) Aluminum (mg/l) Sulfate, SO 4 2+ (mg/l) ,600 8,100 Specific Conductance (μs/cm) DO (mg/l) ~8 10 ~1 35 ph Redox Potential (mvolts) ~ ~ ND = Not detected above detection limit SUMMARY Naturally occurring acid rock drainage has historically and is presently discharging directly to North Fork Rapid Creek, North Fork Castle Creek, Castle Creek, and some unnamed tributaries. Based on surface and ground water data collected for this investigation in 2002 and 2003, the discharge is acidic, contains high concentrations of iron, aluminum, and sulfate, is naturally occurring, and originates from pyrite-rich Precambrian metamorphic rocks. Where the acidic drainage mixes with uncontaminated surface water, red-orange iron hydroxide and white aluminum hydroxide deposits quickly precipitate out of solution and coat the stream substrate. Some of the precipitate remains suspended and is transported downstream, negatively affecting the stream habitat for several hundred meters. With time, diagenetic processes cause the precipitate to dewater and lithify, cementing the stream substrate and ultimately forming iron-cemented conglomerate. While the overall upstream to downstream surface water chemistry is little affected, the precipitates have a significant negative effect on reaches of the stream s habitat. Damage or destruction of the biotic habitat is the primary effect and results from mineral precipitation on and within stream substrate. Plant and animal life are stressed in reaches of the streams. Where effects are great, reaches of stream may be devoid of most life. The absence of plants and macroinvertebrates results in a habitat unfavorable to fish. Natural chemical reactions attenuate the effects, ultimately restoring the stream s water quality and allowing the stream s habitat to become favorable to plants, macroinvertebrates, and fish. This natural restoration appears to occur within approximately one to two km downstream from acid rock drainage discharge locations. The neutralizing capacity of North Fork Castle Creek surface water is exceeded by acid rock discharge and stream quality does not improve before its confluence with Castle Creek. Approximately three to four km of North Fork Castle Creek upstream from its confluence with Castle Creek are negatively

7 Proceedings of the South Dakota Academy of Science, Vol. 83 (2004) 89 affected by acid rock drainage. Based on visual observation, the damage to the stream may be exacerbated by cattle grazing. Iron bogs are depositional features and many were mined from the early 1900s up through the 1960s because of their high iron content (approximately 50-percent iron). While iron bog mines do impact the environment, in this study area, the mines are relatively small. When compared to the total naturally occurring acid discharge in the two watersheds, the mines probably have a negligible effect on overall water chemistry. Even with the absence of mining, iron bogs and acid rock drainage would be present and affecting the environment in this study area. ACKNOWLEDGEMENTS We would like to acknowledge the South Dakota Department of Environment and Natural Resources for their technical support and use of their automated sampling equipment, and the South Dakota Department of Game, Fish and Parks, for their technical support. Dr. Edward Duke of the South Dakota School of Mines and Technology performed the visible and near infrared reflectance spectroscopy. This study was financed through research grants received from the South Dakota Department of Environment and Natural Resources, the South Dakota Department of Game, Fish and Parks, the Black Hills Flyfishers, and the Geological Society of America. REFERENCE CITED Carter, J.M, D.G. Driscoll, J.E. Williamson, and V.A. Lindquist, 2002, Atlas of Water Resources in the Black Hills Area, South Dakota, U.S. Geological Survey, Hydrologic Investigations Atlas HA-747, 120 p. Deer, W.A., Howie R.A., and Zussman, J., 1980, An Introduction to the Rock- Forming Minerals, Longman, London, pp DeWitt, E., J.A. Redden, D. Buscher, A.B. Wilson, 1989, Geologic Map of the Black Hills Area, South Dakota and Wyoming, U.S. Geological Survey, Miscellaneous Investigations Series MAP I Pennsylvania Department of Environmental Protection, 1998, Coal Mine Drainage Prediction and Pollution, Brady, K.B.C., Smith, M.W., Schueck, J. editors, 1998, pp. 1-1 to Piper, Arthur M., 1944, A Graphic Procedure in the Geochemical Interpretation of Water-Analysis, Hydrology Papers, Transactions, American Geophysical Union, pp Stiff, Henry A., Jr., 1951, The Interpretation of Chemical Water Analysis by Means of Patterns, Journal of Petroleum Technology, vol. 3, no.10, pp U.S. Geological Survey, March , phreeqc (Version 2) A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations, Version U.S. Geological Survey, 1975, Mineral and Water Resources of South Dakota, U.S. Government Printing Office, Washington, pp

AMD 101. Chemistry of Abandoned Mine Drainage. Bruce Golden WPCAMR

AMD 101. Chemistry of Abandoned Mine Drainage. Bruce Golden WPCAMR AMD 101 Chemistry of Abandoned Mine Drainage Bruce Golden WPCAMR http://amrclearinghouse.org Western PA Coalition for Abandoned Mine Reclamation A helping hand to watershed groups grappling with the legacy