In 1887, city engineers extended the Pearl Street sewer over six hundred feet into the Back Bay area. They drove sturdy piles into the tidal flats, girded and planked them with wood, and secured them using bolts and spikes of galvanized iron. Additionally, they built a further extension (shown) into the Back Bay to meet a channel the U.S. government had newly excavated.

In the background, a tall pile driver is visible on a small float with a shed. A close look reveals a man on a skiff nearby. Over on the right lies a sizable pile of planks.

Two Portland city civil engineers, wearing suits and straw hats, pose for the camera with their survey transits. On the right, in the foreground, is William S. Edwards. Behind him, to the left, is Edward H. Foster.