My obsession with Albuquerque’s plumbing continues with today’s column (sub/ad req), a look at what’s in the stormwater running off of Albuquerque and what the various agencies, primarily federal and local, are doing about it:

After a good rain, the concrete channel that collects rainwater from much of Albuquerque has the dirty-brown look of a silty, Western arroyo in a storm.

But the initial wave of water that traces down the North Diversion Channel is different, quintessentially urban. Water-quality expert Bruce Thomson calls it the “first flush.”

The big stuff is obvious — water bottles, plastic cups, wads of paper. We’re messy, and the North Diversion Channel, which collects runoff from 110 square miles of mostly urban watershed, is the last resting place for a lot of what we idly toss aside.

But what you can’t see may be more important — the thin film of motor oil, toxic metal dust, asbestos from the brake linings of our cars. Perhaps most important, according to state and federal regulators, is fecal coliform bacteria, which indicate the water is contaminated with animal and human feces.

An invisible film of grit builds up on the city when it’s dry, until the next big rain washes it down the North Diversion Channel and toward the Rio Grande.