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This report presents water quality data for samples collected in September, 1994, September, 1996, and June, 1997 in Great Smoky Mountains National Park from the areas around the abandoned Fontana and Hazel Creek mines in North Carolina, and the upper reaches of the West Prong of the Little Pigeon River in Tennessee. Data include temperature, pH, specific conductance, dissolved oxygen, alkalinity, flow, total acid soluble and dissolved major and trace element concentrations. Data are interpreted in terms of their impact on the surrounding environment with enumeration of remediation options around the mine sites. STATEMENT OF PROBLEM The U. S. Geological Survey (USGS), in cooperation with the National Park Service (NPS), initiated a study of the factors that affect water quality associated with the abandoned Fontana and Hazel Creek mines in Great Smoky Mountains National Park in 1996. The USGS also conducted reconnaissance sampling in 1994. The goals of the research were to (1) assess the quality of water within the abandoned mine workings; (2) assess the environmental impact of waters issuing from the abandoned mines and surrounding country rock; and (3) suggest options for remediation of the sites. Acid-mine drainage is produced by the weathering and oxidation of pyrite and other heavymetal sulfide ore minerals in surficial environments. Acid drainage can also occur naturally from weathering of pyrite-bearing rocks such as the Anakeesta Schist found in the park. A key aspect of the evaluation of the environmental impact of acid-mine drainage is the comparison of acid-mine drainage with naturally occurring acid-rock drainage associated with the weathering of the Anakeesta Formation. Any remediation efforts directed at mine drainage should consider the natural background water composition in the watershed as a reference. In some cases, acid-mine drainage problems are naturally mitigated. Dilution of acidic, heavy metal laden streams by inflowing tributaries can quickly attenuate acid mine drainage problems. Heavy-metal concentrations and acidity can be diluted below toxic levels over short distances. Likewise, reducing environments such as natural wetlands can strip heavy metals from acidic drainage by precipitating heavy-metal sulfide minerals. PREVIOUS WORK To date, no published reports are available on water quality associated with the abandoned Fontana and Hazel Creek mines. However, several studies have investigated various aspects of water quality associated with drainage from watersheds underlain by the Anakeesta Schist, and water quality issues related to acid deposition. Abernathy and others (1984) studied the heavy-metal concentrations of surficial sediments in Fontana Lake. Samples from the mouths of the Eagle Creek and Hazel Creek watersheds which host the Fontana and Hazel Creek mines contain elevated zinc and copper concentrations relative to other parts of the lake. Lesure and others (1977) reported geochemical data for stream sediments, soils, and forest litter (ash) from the Fontana and Hazel Creek mine areas. Flohr and others (1995) identified a number of secondary minerals at Alum Cave, which form from the evaporation of ground waters in the sheltered environment of Alum Cave. When wetted by heavy rains, these secondary salt minerals readily dissolve and release acid and heavy metals to the watershed. Similar salts have been identified along the Road To Nowhere. Southworth (1995) mapped the distribution of pyritic rocks in the southern part of the park around the mines. Schultz (1998) mapped the distribution of pyritic rocks and landslides in the Mount Le Conte quadrangle. Flum and Nodvin (1995) and Nodvin and others (1995) investigated the effects of acidic atmospheric deposition on the Great Smoky Mountains ecosystem. Numerous workers have investigated acid drainage generated by road construction in the Anakeesta Formation (Huckbee and others, 1975; Bacon and Maas, 1979; Mathews and Morgan, 1982; Kucken and others, 1994; Byerly, 1996; Schaeffer and Clawson, 1996). GEOLOGICAL SETTING The bedrock geology of the Great Smoky Mountains National Park is dominated by metamorphosed sedimentary rocks of the Ocoee Supergroup, which is between 1 billion and 545 million years old (Fig. 1; King and others, 1964). From oldest to youngest, the supergroup consists of the Elkmont Sandstone, the Thunderhead Sandstone, the Anakeesta Formation, the Copper Hill Formation, and the Wehutty Formation (Southworth, 1995). Also, in the Cades Cove area are exposures of the 475 million year old (Ordovician) Jonesboro Formation (Fig. 1). The rocks of the park represent a number of fault blocks which are bound by faults that dip shallowly to the southeast (Southworth, 1995). From an acid-drainage perspective, some of the most important attributes of the rock units are their acid-buffering (neutralization) and acid-generating capacities. These characteristics are best assessed through the mineralogy and lithogeochemistry (rock chemistry) of the units. Limestone and dolomite units such as the Jonesboro Formation have high acid-buffering potential, but because of their limited geographic extent, they have little effect of the overall water quality of the park. Quartzrich units such as the Elkmont Sandstone and the Thunderhead Sandstone may be considered generally inert, non-reactive units with respect to acid buffering and generation. However, it is important to realize that on a local scale, these units may contain narrow horizons that may be acid neutralizers or acid generators. Shale units and the metamorphosed equivalents, such as the Anakeesta Formation and parts of the Copper Hill and Wehutty formations, have extremely low acid-buffering capacity. Other important aspects of the Anakeesta, Copper Hill, and Wehutty formations are that they contain trace amounts of pyrite and pyrrhotite (iron-sulfide minerals) and metamorphosed organic matter, which imparts a black color to the rocks. The weathering of pyrite from these rocks is a significant source of acid. The ancient environment on the ocean floor where these sediments were deposited was anoxic (oxygen-poor) which promoted the accumulation of organic matter and the formation of pyrite in the sediments. This reducing environment is also conducive to enrichment of the sediments in heavy metals such as copper, lead, zinc, and cadmium, among others. In turn, these may be reflected in the modern ground and surface waters that weather these rocks. Copper-rich massive sulfide deposits such as those at the Fontana and Hazel Creek mines and at Ducktown, TN to the southwest also form in this type of environment. The Fontana and Hazel Creek mines are hosted by shaly portions of the L im es to ne /d ol om ite Sc hi st /s la te /s ilt st on e Sa nd st on e/ co ng lo m er at e/ ra tl in bu r / ! V J d ll ll lL 'U .A gn ei ss /s ch is t G lin gm ah -s D om e '.' 1 " V i / . . , . .' " . ' . . . Fi gu re 1 . L ith og eo ch em ic al m ap o f t he G re at S m ok y M ou nt ai ns N at io na l P ar k sh ow in g th e di st ri bu tio n of v ar io us r oc k ty pe s. H ea vy li ne s ar e fa ul ts . T he lo ca tio n of th e W es t P ro ng o f t he L itt le P ig eo n R iv er is s ho w n fo r r ef er en ce . M od if ie d fr om S ou th w or th ( 19 95 ). Copper Hill Formation. Thus, ground and surface waters around the mines would be expected to have naturally elevated acidity and heavy-metal contents relative to waters draining sandstone or carbonate rocks in the Park. For the Anakeesta Formation, in particular, a thin regolith develops on the rock and high rainfall events have historically resulted in debris flows on the steep slopes underlain by the unit. The exposure of fresh rock during debris flows serves to enhance naturally the generation of acid from these rocks. MINERAL DEPOSITS There are over 100 inactive or abandoned mines and prospects in the southern Appalachians near the Great Smoky Mountains National Park. These sites represent a number of different types of mineral deposits, and produced a variety of different commodities including copper, zinc, lead, silver, and gold. The Fontana and Hazel Creek deposits within the southern boundary of the park (Figs. 1 and 2) are classified as massive sulfide deposits because they are sheet-like bodies dominated by greater than 50 % heavy metal sulfide minerals such as pyrrhotite (Fe^S), pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS), and galena (PbS). The deposits are enclosed within thick sequences of metamorphosed sedimentary or volcanic rocks. These types of deposits have the potential to adversely affect water quality for two reasons: (1) they contain high concentrations of sulfide minerals that can readily oxidize and decompose on weathering to produce sulfuric acid that is enriched in heavy metals, and (2) the rocks around the deposits typically have limited ability to neutralize the acid. The mineral deposits around Ducktown, TN are geologically similar to the Fontana and Hazel Creek deposits. Both the Fontana and the Hazel Creek deposits are deeply weathered. So any primary sulfide ore minerals that were once at the earth's surface are oxidized and decomposed. What remains at the surface is a reddish-brown cap of iron-oxide minerals called a gossan The minerals in the gossan, dominantly goethite and quartz, represent the weathered remnants of the sulfide ores. The unweathered primary sulfide ore lies below the surface, underneath the gossan. An intermediate zone develops between the gossan and the primary ore; this intermediate zone of secondary enrichment is called the supergene zone. It forms as the primary sulfide ore weathers and reacts with ground water. As sulfide minerals dissolve at the surface, copper can leach downward and react to form new copper-bearing minerals. The supergene zone can be as much as 3 meters thick and can contain very high-grade ores. Over time, fluctuations in the water table and in climatic condi

u.s. geological survey open file report/open-file report

Preliminary report on water quality associated with the abandoned Fontana and Hazel Creek Mines, Great Smoky Mountains National Park, North Carolina and Tennessee