Hulls damaged in storms, collisions, groundings, or by the action of worms or rot also needed work below their waterlines.

Graving docks are costly, difficult to build, and require significant amounts of shoreline real estate.

As ships reached 300 feet (91 m) and longer in the mid-nineteenth century, the investment required to build such a dock became prohibitive.

[4] In 1853, the company commissioned William H. Webb to build the Great Balance Dock at what was estimated to be a cost of $150,000.

To prepare for hauling a ship, a series of hull blocks were placed in the bottom of the Great Balance Dock, labeled "B" in the sectional diagram.

Once the blocks were set, the dock would submerge to the required depth by opening the external doors, labeled "D".

Once submerged, the ship requiring maintenance could be towed into position and secured with lines tied to the dock's sides.

[9] The two steam engines, one on each side of the dock, powered the pumps, "P", to expel the water in the tanks through the openings at "O".

[9] To refloat the vessel was a simple matter of winching up the poles and opening the doors to flood the dock again.

The dock was an integral tool for ship construction, particularly for installing the initial sheathing of copper to protect the hull.

The dock also serviced a steady stream of vessels of all types for routine work on their hulls.