approximately 50 feet deep in the midpoint of Upper Bay. A project to replace two water mains between Brooklyn and Staten Island, which will eventually allowing for dredging of the channel to nearly , was begun in April 2012. The Army Corps has recommended that most channels in the port be maintained at 50 feet deep. Dredging of the canals to 50 feet was completed in August 2016. The channels also include bridges that limit the heights of vessels that can use the harbor. The Verrazzano-Narrows Bridge has a clearance of at mean high water. The Brooklyn Bridge has of clearance, while the Bayonne Bridge has been raised from to . Pilotage The Sandy Hook Pilots are licensed maritime pilots that go aboard oceangoing vessels, passenger liners, freighters, and tankers and are responsible for the navigation of larger ships through port district. History The estuary was originally the territory of the Lenape, a seasonally migrational people who would relocate summer encampments along its shore and use its waterways for transport and fishing. Many of the tidal salt marshes supported vast oyster banks that remained a major source of food for the region until the end of the 19th century, by which time contamination and landfilling had obliterated most of them. The first recorded European visit was that of Giovanni da Verrazzano, who anchored in The Narrows in 1524. For the next hundred years, the region was visited sporadically by ships on fishing trips and slave raids. European colonization began after Henry Hudson's 1609 exploration of the region with the establishment of New Amsterdam, the capital of the Dutch province of New Netherland at the tip of Manhattan. The British colonial era saw a concerted effort to expand the port in the triangular trade between Europe, Africa, and North America with a concentration of wharves along the mouth of the East River. After the Battle of Brooklyn, the British controlled the harbor for the duration of American Revolutionary War, and prison ships housed thousands at Wallabout Bay. In the early 19th century, the Erie Canal (often used for grain) and Morris Canal (mostly used for anthracite) gave the port access to the American interior, leading to transshipment operations, manufacturing, and industrialization. The invention of the steam engine led to expansion of the railroads and vast terminals along the western banks of the Hudson River, complemented by an extensive network of ferries