At some point, he will start in on the horrors of the M. Kalbfleisch Chemical Works, eventually making his way to the sins of Standard Oil.

Image Credit... The New York Times

If the city’s dead industries leave ghosts behind, Mr. Waxman is an adept medium.

The Newtown Creek watershed, his field of expertise, is a place where such specters are all too real. In the murky depths of the 3.8-mile estuary, the past haunts the present. Since the creek was designated a Superfund site in 2010, contractors from the Environmental Protection Agency have been dredging and testing in search of that past. The sludge acid that the Kalbfleisch factory sluiced into the water back in the 1830s is of more than academic concern.

Not that Mr. Waxman is any sort of an academic. While the Newtown Creek Alliance, an environmental advocacy group, lists him as its resident historian, his credentials were earned on the street and the Internet, through countless solitary walks and countless nights poring over obscure archives. (“Mitch got that title by proving it, over and over,” said Kate Zidar, executive director of the organization.)

Formerly a comic-book artist and writer, Mr. Waxman earns his living doing photo retouching out of his apartment in Astoria, Queens. Since 2009, he has documented his passion for the creek — in oddly beautiful photography and beautifully odd prose — on his blog, The Newtown Pentacle.

Lately, he has been leading public walking tours of the waterfront for the alliance and other groups, as well as personally guiding anyone else who comes calling. He has lectured to local politicians and environmentalists, shepherded documentary filmmakers around Calvary Cemetery and taught German industrial ecology students a thing or two about sewage. Somehow, almost everyone interested in the polluted waterway seems to find his or her way to Mr. Waxman. He’s become a docent of decay, the cicerone of Newtown Creek.