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Open-File Report 2006-1377

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- Search CMG | Distribution, thickness, and volume of fine-grained sediment from precipitation of metals from acid-mine waters in Keswick Reservoir, Shasta County, California*by*
Terry R. Bruns1, Charles N. Alpers2, and Paul Carlson1

2006

1U.S. Geological Survey, Menlo Park, CA2U.S. Geological Survey, Sacramento, CA 			
Abstract
 				In February 1993, the U.S. Geological Survey (USGS) acquired high-resolution seismic-reflection data to  				map the distribution and thickness of fine-grained sediments associated with acid-mine drainage in  				Keswick Reservoir on the Sacramento River, near Redding, California. In the Spring Creek Arm of  				Keswick Reservoir, the sediments occurred in three distinct accumulations; thicknesses are greater  				than 2 meters (m) in the western accumulation, greater than 5 m in the central accumulation, and  				up to 8 m in the eastern accumulation. In Keswick Reservoir, fine-grained sediments related to acid-mine  				drainage were present from slightly north of the Spring Creek Arm downstream to the Keswick  				Dam. Sediment thickness varies from about 3 m opposite the mouth of the Spring Creek Arm to less  				than 1 m near Keswick Dam. 			

 				Our estimate for the total volume of fine-grained sediments in the Spring Creek Arm at the time of  				the geophysical survey in February 1993 is about 152,000 cubic meters in three sediment  				accumulations, with about 14,000, 32,000, and 105,000 cubic meters respectively in the western,  				central, and eastern accumulations. We interpreted that an additional 110, 000 cubic meters of  				material was present in the main part of Keswick Reservoir. At the time of data collection, we  				therefore estimate that the total volume of fine-grained sediment was 260,000 cubic meters. In  				the main part of Keswick Reservoir, 42% to 50% of the reservoir area contiguous to Spring Creek  				Arm had mappable fine-grained sediments. Decreasing sediment supply down-reservoir meant that  				mappable sediment covered only about 35% of the reservoir in the area to the south, decreasing  				to about 12% near Keswick Dam. Much of the reservoir bottom below the Spring Creek Arm could  				have had a thin (less than 20-30 cm) cover of fine-grained sediment that was not mappable using  				the seismic-reflection data. 			
						For more information contact: Charles Alpers |
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U.S. Department of the Interior |		U.S. Geological Survey		URL: http://pubs.usgs.gov/of/2006/1377/index.html		Page Contact Information: Michael Diggles		Page Last Modified: 21 December 2006 (mfd)