Port Allen Harbor is located on the south coast of the island of Kaua’i, approximately 20 miles from the city of Līhu’e, Kaua’i’s county seat. Port Allen Harbor was authorized by the Rivers and Harbors Acts of 1935 and 1945. The local sponsor is the Harbors Division, Department of Transportation, State of Hawai’i.
The harbor was constructed by the U.S. Army Corps of Engineers in 1948 at a cost of $1,837,513 (Federal: $1,637,513; non-Federal: $200,000). The project consists of a 1,126-foot-long breakwater, a 35-foot-deep basin (1500 feet long, and 1200 feet wide), and an entrance channel 500 feet wide. In January 1984, repairs were made to the breakwater head damaged in November 1982 by Hurricane Iwa. In July 1991, repairs were again made to the breakwater head damaged in 1989 by heavy storms. In 1994, additional repairs to areas damaged by Hurricane Iniki in September 1992 were made. In February 2009, repairs were made at a cost of $1,824,000 to the 280-foot-long breakwater root section, which was damaged as the result of wave action sustained over numerous years.
Port Allen Harbor is one of two commercial harbors on the island of Kaua’i. Port Allen Harbor is particularly important for commercial charter vessels, liquid bulk cargo and military vessels servicing the Navy’s Pacific Missile Range Facility.
The U.S. Army Corps of Engineers is responsible for maintaining the breakwater structure and turning basin project depths. Maintenance dredging was conducted in 1999 and 2021.