slope. The survey also showed that 50 percent of the broken stones were located on 

 the upper half of the breakwater slopes (27 percent on the sea side and 23 percent 

 on the harbor side); and 27 percent were on the lower half of the structure slopes 

 (18 percent on the sea side and 9 percent on the harbor side). Views of representa- 

 tive types of breaks for the armor stones are shown in Figures 40 through 43. 

 Armor stones with hairline cracks on one side were not counted; only those that 

 were cracked all the way through were considered a break for recording purposes. It 

 was noted during the June 1996 survey that the separated capstones at sta 14+30, 

 initially observed in July 1993, were about in the same position. Overall, the 

 St. Paul Harbor main breakwater appears to be functional and in good condition. 



Prior to the photogrammetric survey work for the St. Paul Harbor main break 

 water, limited ground surveys were conducted. Monuments and targets estabhshed 

 on the breakwater are shown in Figures 44 and 45 for the May 1994 and May 1996 

 surveys, respectively. Positions and elevations of the monuments/targets are pre- 

 sented in Table 6 for the two surveys. Although slight movement may have 

 occurred between 1994 and 1996, the 1994 control points were used for truthing 

 during the 1994 photogrammetric flight and the 1996 control points for the 1996 

 photogrammetric flight. In some cases, targets were re-established. 



An example of photographic stereo pairs secured for the breakwater is shown in 

 Figure 46. After orientation in the stereomodel to the monument and docimient data 

 previously obtained, orthophotos were developed. Accuracy of photogrammetric 

 spot elevations was on the order of ±9 cm (±-0.03 ft). Figure 47 is a typical ortho- 

 photo for a portion of the breakwater. In addition, point plot maps were developed 

 for the breakwater for the 1994 and 1996 surveys. An example of a point plot map 

 showing elevations on the structure is shown in Figure 48. Areas where no eleva- 

 tions are shown are shadowed areas, or voids between the armor stones. Contour 

 maps of the breakwater were developed from the DTM for the 1994 and 1996 

 surveys. Topography of the breakwater in 1996 is shown in Appendix A. Contours 

 depicting the difference in elevations of the breakwater between 1994 and 1996 are 

 shown in Appendix B, and cross sections of the breakwater in 1994 and 1996 are 

 shown in Appendix C. 



An examination of the breakwater topography for 1996 (Appendix A) reveals 

 low areas along much of the breakwater. Only about 5 percent of the higher portion 

 of the structure (sta 7+50 - 15+10) is at its design el of +1 1.3 m (+37 ft), and 9 per- 

 cent of the lower portion of the breakwater (sta 15+10 - 18+00) is at its design el of 

 +9. 1 m (+30 ft). For the higher portion of the structure, the el of about 24 percent 

 of the length of the breakwater is within 0.3 m ( 1 .0 ft) of its design el, or between 

 +1 1.0 and +1 1.3 m (+36 and +37 ft); and approximately 66 percent of the structure 

 is between +1 1.0 and +1 1.3 m (+35 and +37 ft), or within 0.61 m (2 ft) of its design 

 el. About 29 percent of the structure length is below +10.7 m (+35 ft). Most of the 

 low area (that below +10.7 m (+35 ft)) appears to be concentrated between stas 

 13+70 and 15+10. For the lower portion of the structure, the el of about 50 percent 

 of the length of the breakwater is within 0.3 m (1.0 ft) of its design el, or between 

 +8.8 and +9.1 m (+29 and +30 ft); and approximately 89 percent of the structure is 

 within 0.61 m (2.0 ft) of its design el, or between +8.5 and +9.1 m (+28 and +30 ft). 

 Only 2 percent of the structure length is below +8.5 m (+28 ft). 



Chapter 2 Monitoring Program 49 



