“Black mustard” is what people call the thick oil that is often visible — particularly at sunset — on the surface of Newtown Creek, which borders Queens and Brooklyn in New York City. The estimated 30 million gallons of oil is one of many toxins in the creek, an Environmental Protection Agency Superfund site. This would seem an unlikely place to not only inspire, but to also be the venue, for an opera, but it is. The opera "Newtown Odyssey," by UC Davis professor Kurt Rohde, visual artist Marie Lorenz and writer Dana Spiotta, is being premiered soon.