Hydraulic Mining was a gold recovery method that was used during many of the gold rushes around the world during the 1800ís. It was used extensively in California's Mother Lode county
during the famous gold rush there.
One of the problems that the early California gold miners faced with basic placer mining was the amount of manual labor that was required to process the gravels. Most of the early placer mining was done by individuals or small groups of men who would shovel material and process it through sluice boxes or other equipment to extract the placer gold. If the prospector was fortunate enough to find a rich pay streak of gold then it was often profitable to work these gravels by hand. Thousands of men tried to strike it rich this way, and sometimes they were successful. However, most of the richest and most easily accessible gravels had been exhausted within just a few short years, and in order to mine profitably, it was necessary to process much more material than could be done with simple hand tools.
Hydraulic mining was the perfect answer to this problem. It used water under high pressure to wash away gravels and high bench deposits, making a slurry that could be run through a sluice box or other equipment to recover the gold. The water was routed from a source such as a nearby river or stream into ditches and flumes, where it was run through a canvas hose to a high pressure nozzle called a monitor. The monitors were huge cannons, some up to 18 feet long, capable of discharging massive amounts of water under extremely high pressure. These jets of water could literally wash away mountains, removing all the material down to bedrock. They were the perfect tool for reaching the ancient river gravels buried underneath mountains.
Due to itís large scale, hydraulic mining was a popular method used by larger mining companies, rather than individual prospectors. These operations would often employ dozens of men. They were extremely efficient at moving tons and tons of material for significantly less cost than other methods. It made many areas with lower paying gravels profitable to mine where it may not have otherwise been cost effective.
Unfortunately, the downside of hydraulic mining was that it dumped massive amounts of discharge material into the nearby streams and rivers, choking them with debris and causing extensive flooding and erosion issues. The miners had no interest in stopping the practice, as it was a profitable venture for them. Farmers cried foul, as their fertile farmlands were covered with silt from the mining upstream. With the huge silt discharges into the river, flooding became a bigger and bigger problem, destroying not only rich farmlands, but towns as well. The war over hydraulic mining continued throughout the 1870ís and 1880ís. Farmers feuded with the miners, politicians got involved, and eventually the practice became outlawed on January 7th, 1884.