The combined Army Harbor Defense Command Post, or HDCP, and Navy Harbor Entrance Command Post is a two story concrete structure, located on the southern end of Rugged Island. The upper level was occupied by a SCR-582 surveillance radar site and an observation station, while the lower level housed utility areas, latrines, office space, and the (anti-)Chemical Warfare Service, or CWS, equipment.
A pair of small free standing power houses were constructed nearby to provide electricity for the facility.
Construction on the facility was still underway when the Harbor Defense Project was canceled, leaving some concrete work and internal construction unfinished and the backfilling operation incomplete.
Due to lack of specific room designations, I have assigned numbers to rooms without a known purpose to facilitate identification. Rooms numbers 1 to 4 are on the east side of the corridor, 5 and 6 are on the west side. See the Annotated Plan for details.    Note: The partition between rooms 1 and 2 was not installed.