The Longfellow Bridge has its design challenges ahead, and the BU bridge has been no picnic for engineers.

But another bridge in Boston – the Chelsea Street bridge between Chelsea and East Boston – is a simple affair. By the end of the summer, the new bridge, designed by HNTB and built by J.F. White of Framingham, may be complete. It may even happen ahead of schedule.

Although the men working with iron above the river are having no trouble, the men who move mud below it have been facing a dozen daunting engineering tasks for over a year.

They’re all trying to figure out how to make the channel for oil tankers wider. Engineers, pilots, tug captains, oil companies, private landowners, and Coast Guard and Army personnel have been at the drawing board for two years now.

The new bridge, after all, will span the more than 200-ft. wide channel without interruption. That’s thanks to two superstructures that now dominate the Chelsea skyline (anyone can see them from the Tobin Bridge). So the bridge, when opened, might be wide enough to fit a “Panamax” oil tanker headed to the Gulf, Irving and Global tanks upstream.