of +15 feet MSL. On this basis, tests were conducted with depths at the 

 toe of the seawall of 17, 32, 35, and 40 feet referred to a Stillwater 

 level of +15 feet MSL. Wave periods of 3.5, 6.0, 8.0, 8.5, and 9.0 sec- 

 onds were used; wave heights varied from 2.5 to 16 feet. Stability tests 

 to determine the largest waves that will not displace armor units from 

 the test sections, based on the no-damage criterion, require the use of 

 test waves slightly greater in height than the selected prototype design 

 wave. With profile Y (see Fig. 6-43) installed in the model and a 

 Stillwater level of +15 feet MSL, the water depth at the toe of the test 

 sections was 17 feet. Preliminary tests showed that the largest 6-second 

 wave that could be generated in this water depth by the available plunger- 

 type wave generator was 10 feet. Therefore, because the selected proto- 

 type design wave was 15 feet in height, the Stillwater level and the test 

 structure were raised to obtain a depth at the structure toe of 40 feet 

 referred to +15 feet MSL. This was the smallest depth found sufficient 

 to ensure that waves reaching the test sections were large enough to 

 damage the protective cover layers. In developing plans for the pro- 

 posed seawalls, the best design was desired for each type of structure 

 required for the various reaches of the bay shoreline. Four series of 

 tests were conducted and two or more seawall plans were investigated in 

 each test series. Stability tests of the armor-unit cover layers were 

 conducted for each plan in test series 1, 2, and 3. Overtopping data 

 were obtained for at least one plan in each of the test series. Wave 

 forces were determined on incremental sections of one plan in test series 

 3 and three plans in test series 4. The conditions for which breaking 

 waves would attack the test sections were determined for all plans in 

 test series 4. 



(i) Summary of Test Results . Test series 1 consisted of 

 plans for seawalls in the area of profile B (Fig. 6-43) and concerned 

 a simple rubble-mound structure with a vertical, impermeable wall at the 

 centerline. This reach of shoreline would be subjected to the largest 

 waves (6-second period, 15-foot height) likely to attack any section of 

 the proposed seawall. The protective cover layer on the bayside would 

 consist of one layer of the rectangular-shaped, quarried armor stones 

 weighing 8 tons each on a slope of 1:2. Toe units consisted of 3.3-ton 

 stones. Preliminary tests showed that the toe stones were moved down- 

 slope by waves only 8 feet high. The toe section was then redesigned 

 using 6-ton stones and the toe section was extended farther downslope 

 (Fig. 6-44). This plan was found to be stable for the selected design 

 wave; however, because of the lack of space between the shoreline and 

 the existing industrial and commercial developments along parts of this 

 reach of seawall, the plan was judged unacceptable. Another seawall sec- 

 tion consisting of a vertical concrete wall with a rubble mound on the 

 bayside to protect the natural ground was then tested. Initial tests 

 showed that the toe needed added protection. The modified section that 

 was foiand stable for the selected design wave is shown in Figure 6-45. 

 Overtopping tests showed that a maximum of 3.7 cubic feet per second of 

 overtopping water would occur per foot of seawall for the 6-second period 

 and 15-foot height design wave. Wave forces were also measured on the 

 vertical-wall part of the structure. The measured wave forces resulting 



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