A view overlooking Last Chance Lake west of 70 Mile House, British Columbia.  More info below:

The Clinton and 70 Mile House area is filled with alkaline lakes, easily recognizable by the ring of white soda deposits that line their shores. Once labeled as ‘useless,’ these shallow and often smelly lakes were once a beehive of activity. Although testing of the salt was an occurrence in the late 1890s, the completion of the Pacific Great Eastern, in 1919 provided a more available means of transportation and several lakes went into production. The Pacific Great Eastern was the railway that went north, many of the locals referred to it as the Please Go Easy, because it was so slow. Some lakes were mined for their Epsom salts or magnesium sulphate, the surface was scraped, and the ore put in sacks. Other lakes produced soda carbonate, a product used in washing. Analysis testing done on the soda in 1898 was inconclusive as to what it contained. No two chemists could agree, except that housekeepers pronounced it to be far and away ahead of “Pearline” for washing, and blacksmiths felt that no other soap compared with the native compound. These lakes were mined in the winter, accessibility depending on a thick layer of ice. The soda was in the mud at the bottom of the lake and in the water. The cold weather would bring it up. The ice had to be eight to ten inches thick, strong enough to hold a team of horses. A six to seven inch layer of soda would form under the ice. The ice would be chipped away and the layer of soda broken out and placed on the ice with tongs. Production however at ‘The Last Chance’ was unique. The lake held very little water and there was a lot of mud in the soda. After several experimental trials the British Columbia Chemical Company developed a process to separate the soda from the mud. According to the 1929 Report of the Minister of Mines, a well designed plant was constructed and a good camp for winter operations was provided, having cost the company approximately $50,000. Unfortunately a 1930 report states that “no further operations were carried on at the works of this company... It is reported that results were not satisfactory.” Today you might find a few broken bricks or boards, or further up the hill, remainders of the camp. A scant reminder of this failed scheme, once a ‘Salt Lake City’ of its own.

When this lake dries out further, one can see the circular spots & cracks, bearing a resemblance to the more famous alkaline Spotted Lake at the southern end of the province.  

From: https://www.exploregoldcountry.com/pdf/caches/Last%20Chance%20Lake%20Soda%20Site.pdf