Hydraulic mining was also used in the Carson River region. Hydraulic mining uses mercury to bond to the gold and silver in the mining slurry. The gold/silver amalgam drops to the bottom of the sluice while gravel and other tailings pass over. As time passes the mercury is ground in to a fine layer that coats the bottom of the sluice and can contaminate the surrounding area through leaks and the effluent of water containing the mercury. It is estimated that this practice in California attributed to mercury losses up to 10-30%.  