POD developed plans to improve conditions in the area widi the following 

 plan objectives, taken from POD (1984): 



a. Improve commercial fishing opportunities in the North Hilo and 

 Hamakua Districts during the 1985-2135 period of analysis. 



b. Improve recreational boating opportunities for the people of the North 

 Hilo and Hamakua Districts. 



c. Provide protection for trailer boat launching and recovery during all 

 but storm conditions. 



d. Limit the protected water area to launch and recovery operations, 

 allowing sufficient maneuvering room. 



e. Minimize conflicts with existing and planned uses of the affected area. 



A 250-ft-long rubble-mound breakwater protecting a 9.5-ft-deep entrance 

 channel, 7.5-ft-deep turning basin, and a boat-launching ramp was completed 

 in 1988 (Figures 7 and 8). The design layout for the facility and stability of 

 the breakwater were optimized through physical model studies conducted by 

 CERC (Bottin, Markle, and Mize 1987). The breakwater is armored with 30- 

 ton reinforced dolosse and the crest is stabilized with'a concrete rib cap. The 

 toe of the dolosse was keyed into the hard basalt bottom by means of a trench 

 excavated around the perimeter of the breakwater. The rib cap is supported 

 on concrete pipe columns. 



The initial design of the breakwater core called for the vertical placement 

 of the core stone adjacent to the dolosse and under the concrete rib cap. 

 However, the breakwater stability model study noted that the stone beneath 

 the rib cap showed some displacement and consolidation during testing. The 

 constructability review of the plans also noted that the vertical placement of 

 the breakwater core stone would be a formidable task in the area's year-round 

 rough ocean conditions. 



A stable breakwater core was achieved through the innovative design of a 

 reinforced concrete pipe (RCP) rib cage (Figure 7). The RCP rib cage 

 utilized two rows of 60-in. class 4 RCP, set vertically as columns, on 14-ft 

 center. Each row's RCP columns were spaced 8 ft on center with reinforcing 

 steel and concrete placed inside of each pipe. The RCP columns and concrete 

 rib cap formed a containment cage for the core and capstone. The RCP rib 

 cage clearly provided a stable breakwater core and crest that maintained the 

 energy- dissipating characteristics of the breakwater and was constructable in 

 the rough waters of the project site. 



10 



Chapter 1 Introduction 



