National Geographic Channel tromps into the wild with blue-collar pioneers who shirked conventional 9-to-5 careers to make their living in the deep rivers, soggy mudflats and wild backwoods of America. Filthy Riches, a new series premiering Sunday, April 20, at 10:00 p.m. ET/PT, travels the country with industrious Americans who prove they're not afraid to roll up their sleeves and get their hands dirty in order to make a living. (Source: National Geographic Channel)…