Continued high levels of mercury in present day river sediments
indicate that the bulk of the estimated 2.5 million pounds of the heavy
metal that were lost in the Bear River Watershed during 32 years of
hydraulic mining are still there, trapped in the 1.5 billion cubic yards
of sediment that were stripped from hillsides by high pressure water
cannons the miners called monitors.
When added to the riffles and troughs of large sluices, liquid
mercury captured gold particles falling out of the tons of gravel and
soil being washed through in the swift current. Mercury was inevitably
lost into the river and accumulating sediments. In the post-hydraulic
mining era, extensive use of mercury in dredging an estimated 3.6
billion cubic yards of flood plain deposits for gold kept contamination
levels rising into the early 1960s.
http://bearriver.us/mercury.php
No comments:
Post a Comment