Three separate and distinct (although interrelated) problems exist at Redondo Beach King Harbor, California, at the present time: recurring, but infrequent, structural damage to the breakwater; excessive wave activity in the harbor caused by waves penetrating through and overtopping the permeable rubble-mound breakwater; and shoaling of the harbor navigation channel and boat mooring area. The US Army Engineer Waterways Experiment Station was requested to: (a) perform a water wave refraction/diffraction/shoaling analysis of the 1983 winter storms to determine the wave characteristics and frequencies-of-occurrence at the breakwater structure site for the extreme storm events of historical record and for the higher sea waves which overtop the lower portion of the breakwater on an average annual basis; (b) determine the magnitude of wave penetration through the permeable rubble-mound structure, overtopping of the structure, and total wave transmission into the harbor; (c) evaluate the effect of raising the crest elevation of the structure on wave transmission into the harbor; (d) estimate the structure armor stone required for stability based on the return period of storm waves of various heights; and (e) propose alternative structural measures for reducing excess waves in Basin 3 and reducing harbor shoaling by sediment penetration through the breakwater. Keywords: Armor stone, Chemical grouts, Overtopping, Permeability, Refraction, Rubble-mound breakwater, Storm damage, Transmission, Water waves.