U.S. Department of the Interior
U.S. Geological Survey
October 27, 1998
CERTAIN MINING OPERATIONS HAVE NOT HURT PRISTINE ALASKAN RIVER
The water quality of the Fortymile River-a beautiful, wild and scenic river in the remote part of east-central Alaska-has not been adversely impacted by gold placer mining operations according to an integrated study underway by the U.S. Geological Survey and the Alaska Department of Natural Resources.
Warren Day, a USGS research geologist from Denver, Colo. will present "Geologic Setting of the Fortymile River Mining District" on October 27 at the annual Geological Society of America meeting in Toronto, Canada at 1:30 p.m. Recent concern over the impact of suction dredge gold placer mining on the water quality of the Fortymile River prompted the collaborative study, with its overall objective focusing on establishing the baseline and background geologic, geochemical, and botanical framework for the lower Fortymile River area.
Day and his colleagues concluded that concentrations of arsenic found in the bedrock are within the ranges of the background soil and stream sediment values. A companion study of the surface water chemical and turbidity data has shown that any variations due to the suction dredging activity fall within the natural variations in the Fortymile River.
The suction dredge placer miners extract gold from the river gravels by sucking the gold-bearing gravels into the floating dredges, pumping the gravel-water mixture across a settling table where the gold concentrates by gravity, then discharging the gold-free gravel and water back into the river.
The management of the region and its resources is complex due to the many diverse land-use options. Small-scale, family-owned gold mining has been active on the Fortymile since the "gold rush" days of the late 1880's. However, in 1980, the Fortymile River and many of its tributaries received Wild and Scenic River status. Because of this status, mining along the
river must compete with recreational usage such as rafting, canoeing, and fishing.
Violation of mining discharge regulations would close down the small-scale mining operations. No data existed before this study to establish if the mining was degrading the water quality. However, even with the absence of data, environmental groups were active to close down mining on the river citing unsubstantiated possible discharge violations.
This study has found no violations to date to substantiate closure of the small-scale mining operations. The result is a continuance of a way of life on the last American frontier.
Additional information about this study can be found at the following Internet address. This file is in Adobe Acrobat (.pdf) format. If you do not have the Acrobat Reader program, you may download it for free here.
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