entrance channel and turning basin also required dredging to remove stone and 
dredged landfill material washed into the harbor. 
The latest rehabilitation was completed in 1994 and consisted of construction 
of a new breakwater that extended from sta 1+75 to sta 6+00, as shown in Fig- 
ure 4. The breakwater was moved back 15.2 m (50 ft) shoreward of the reef in 
order to provide the incoming wave more area between the reef and the structure 
in which to break and dissipate its energy. All loose material seaward of the new 
structure also was removed. The breakwater cross section was modeled at the 
U.S. Army Engineer Waterways Experiment Station (WES) for hydraulic 
stability (Turk 1995). 
For environmental, economic, and logistical reasons, additional basalt stone 
material could not be obtained from either Ofu Island or Tutuila Island to con- 
struct the Ofu Harbor breakwater. Only the stone at the project site that could be 
salvaged was available for use in breakwater construction. The structure, there- 
fore, was built utilizing a unique “concrete design.” Basically, the design 
entailed using various sized concrete units for breakwater construction as 
opposed to using basalt stone. 
The breakwater armor consisted of a single layer of uniformly placed 
4,080-kg (4.5-ton) concrete tribar units (Figure 5). The tribars originated at 
sta 1+75 on the seaward face of the structure and extended to sta 6+00, around 
the head, and then to sta 4+00 on the harbor side of the breakwater. To improve 
the stability of the tribars, work included the construction of a toe trench in order 
to stabilize the armor unit toe, and a concrete rib cap system on the breakwater 
crest to stabilize and buttress tribars at the upper sea-side and harbor-side slopes. 
The rib cap forms were fabricated and concrete poured right into the top section 
of the tribars (Figure 6). The crest elevation of the rib cap was +4.6 m (+15 ft), 
and the slope of the structure was 1V:1.5H. 
Due to the non-availability of local stone as mentioned earlier, concrete 
underlayer units were used during construction of the Ofu Harbor breakwater. A 
unique 1,635-kg (1.8-ton) concrete unit, designed and developed by CEPOD, 
was used as an underlayer for the tribars on the trunk section of the breakwater. 
These units are approximately 1.2 x 1.2 x 0.6 m (4.0 x 4.0 x 2.0 ft) in size with 
chamfered corners. They have 0.4-m- (16-in.-) diameter holes in their centers 
with 0.23-m- (9-in.-) diameter semicircular holes on each side protruding 
through the units from front to back. When placed in a one-layer section on the 
breakwater slope, the holes create void spaces in which wave energy can be 
dissipated. The underlayer unit, with the holes, resembles a slice of swiss cheese 
and has been labeled the “swiss cheese block.” Figure 7 is a view of the unit. 
In addition to the “swiss cheese block” underlayer unit, both 2,270-kg and 
510-kg (2.5-ton and 1,125-Ib) concrete units were formed by pumping high- 
strength, fine-aggregate concrete into geotextile fabric bags. The 2,270-kg 
(2.5-ton) units were used as a rib cap underlayer and were placed along the land- 
fill on the harbor side of the structure between stas 1+75 and 4+00 (Figure 8). 
These units measured approximately 1.4 x 0.9 x 0.8 m (4.5 x 3.0 x 2.5 ft) in size. 
Chapter 1 Introduction 
