IT was 5 in the afternoon, and the scratched-up green Dodge pickup was stopped at a light at Foster and Remsen Avenues in Canarsie, Brooklyn. A teetering bureau and a load of wooden slats were in back.

...

"Bobby, they're dumping!" Officer Fontana shouted. "Go down there!"

A man in a plaid work shirt was tossing planks and slats onto the road. As the Jeep rolled up, he began to tip over the bureau. When it hit the ground, Lieutenant DeRossi said: "O.K. Let's get him."

Lieutenant DeRossi and Officer Fontana are members of the Sanitation Department's Illegal Dumping Task Force, a unit of 35 armed plainclothes officers, former sanitation workers all. And this is their busy season. Construction work and spring cleaning pick up in April and May, generating large amounts of debris; some 21 dumpers' vehicles were impounded in May of last year, a number exceeded only in August.