What's going on here? Your basic truck carrying unknown cargo idling on a residential street on the way to the arena site

What's going on here? As Atlantic Yards Watch documented on the morning of Friday, 2/17/12, flaggers on (privatized) Pacific Street between Carlton and Vanderbilt avenues apparently let a delivery truck bound for the Barclays Center site advance onto residential Pacific Street west of Carlton.

It idled more than 20 minutes in the street, as if double-parking. The contents? Apparently "unknown barrels of chemicals."