The barrier was proposed as a 30-foot (9.1 m) high dam near New Castle, Delaware, 53,300 feet (16,200 m) long, equipped with locks for the passage of shipping to Wilmington and Philadelphia.
The study indicated that in the absence of regular tidal flushing there would be a buildup of pollutants in the impoundment that would render the fresh water reservoir unusable.
[2] The barrier itself was proposed as a low dike built using hydraulic fill, armored against storms with concrete paving.
An overflow spillway was to be set in a section of concrete structure, adjacent to four navigation locks that could accommodate vessels of more than 40-foot (12 m) draft.
Costs for an alternative intake from the reservoir behind the existing Conowingo Dam on the Susquehanna River were estimated to be between $140,000,000 and $170,000,000.