Miller Creek is a tributary of Soda Butte Creek in south-central Montana near the northeast corner of Yellowstone National Park. Surface-water and streambed-sediment samples were collected from streams and seeps throughout the Miller Creek watershed during low-flow conditions on August 28-31, 2000, to characterize metal concentrations and identify possible sources contributing metal to Miller Creek. Most water in Miller Creek appears to be unaffected by mining disturbances or natural weathering

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... of mineralized rocks, although such effects are common elsewhere in the New World Mining District. Values for pH were near neutral to basic. Total-recoverable copper, lead, and zinc concentrations were low, relative to State of Montana water-quality standards, with many concentrations less than the analytical minimum reporting levels. Metal concentrations in Miller Creek during this study ranged from 1 to 6 micrograms per liter (µg/L) for total-recoverable copper, <1 to 5 µg/L for total-recoverable lead, and <1 to 26 µg/L for total-recoverable zinc. Concentrations of cadmium, copper, lead, and zinc in all samples from Miller Creek were less than the chronic aquatic-life criteria, except for one totalrecoverable lead value (5 µg/L) just downstream from the Black Warrior Mine inflow. Leachable lead and zinc concentrations in streambed-sediment samples collected during this study were highest at the Black Warrior Mine inflow. Leachable concentrations at this site were about 20 times greater for lead and 11 times greater for zinc than concentrations in the streambed-sediment sample collected from Miller Creek upstream from this inflow. However, these elevated concentrations had little effect on the leachable metal concentrations in the streambed-sediment sample collected downstream from the Black Warrior Mine inflow. Metal loading to Miller Creek during this low-flow study was relatively small. Three small leftbank inflows having elevated copper concentrations entered Miller Creek near the middle of the study reach and their combined total-recoverable copper load accounted for about 96 percent of the copper load in Miller Creek. Small loads of lead (about 2 micrograms per second) entered Miller Creek from the Black Warrior Mine inflow and a right bank inflow. None of the loads entering Miller Creek had an appreciable effect on mainstem metal concentrations. In addition, substantial differences between mining related areas and areas influenced by local geology could not be determined. ABSTRACT 1 1) draining the highly mineralized New World Mining District. The New World Mining District extends about 10 miles north and about 5 miles east of the southwest corner at the intersection of the 45th parallel and the 110th meridian (Lovering, 1929) . Mining for gold, copper, silver, lead, and zinc began in the late 1800s and continued through the early 1900s, resulting in mining wastes that have been sporadically distributed throughout the Miller Creek watershed. These metal-enriched wastes have the potential to degrade the water quality of Miller Creek. Metal-loading studies have been a useful tool in characterizing water quality and identifying metal sources in historical mining areas (Kimball, 1997; Kimball and others, 1999; Cleasby and others, 2000; Nimick and Cleasby, 2001) . In these studies, detailed profiles of metal loads (mass of metal transported over a given time) along a stream are developed. Metal loads are calculated at many closely spaced sites by multiplying streamflow and metal concentration. Metals can enter the stream from metal-rich surface inflows such as tributaries, discharge from mine adits, and runoff from waste-rock and tailings piles; or from ground-water discharge (subsurface inflow). In addition, intense rainstorms and snowmelt runoff can flush tailings into streams and cause short-term increases in total-recoverable concentration and load (John H. Lambing, U.S Geological Survey, written commun., 2001). Results from metal-loading studies conducted in the nearby Fisher and Daisy Creek watersheds document elevated metal concentrations and show that substantial metal loads enter both creeks from natural and mining-related sources (Kimball and others, 1999; Nimick and Cleasby, 2001) . Periodic water-quality samples collected in the Miller Creek watershed (URS Operating Services, Inc., 1998) indicate that metal concentrations are typically low and metal loads entering Miller Creek are small compared to the other two watersheds in the mining district. However, a detailed metal-loading study along Miller Creek, similar to those along Fisher and Daisy Creeks, was needed to obtain information to identify sources contributing metals to the stream. Potential metals sources in the Miller Creek watershed were thought to include abandoned mines or tailings piles, natural weathering of the pyrite-rich mineralized rock that surrounds the ore zones and occurs as regional alteration in intrusive rocks, or ground-water discharge from faults that cross the watershed. Identification of metal sources along Miller Creek will aid resource managers in planning and conducting effective remediation activities in this part of the New World Mining District. Purpose and Scope The purpose of this report is to characterize metal concentrations and identify possible sources contributing metals to Miller Creek during low flow. This study was conducted during August 28-31, 2000. Surface-water samples were collected at 55 mainstem and inflow sites along Miller Creek ( fig. 2) and analyzed for pH, major ions, and metals. Streambed-sediment samples were collected at 16 sites and analyzed for metal concentrations. The study reach was about 15,000 ft in length (about 2.8 miles) and covered almost the entire length of Miller Creek. This study was conducted by the U.S. Geological Survey (USGS) in cooperation with the U.S. Department of Agriculture (USDA)-Forest Service.