Dawn Ainsley, staff archaeologist at Canada’s Gold-Rush-era Barkerville historic town and park, was overseeing the installation of a new sewer line in 2012 when diggers struck a different kind of gold: garbage. “Every time we hit a garbage dump we had to stop and monitor it,” says Ainsley of the dig. The site of a largely Chinese-Canadian mining town established in the 1860s, and now an open-air museum, Barkerville is full of meaningful trash, the result of generations of household waste tossed off back porches and into alleyways. But this…