Figure 20. Flow transducers and recorder used to determine overtopping rates 



test series, and the volume of water flowing through the outlet pipe over a certain 

 time period, the overtopping rates may be calculated. 



The first storm of the 1994-95 winter season that produced overtopping of the 

 main breakwater occurred on 3 November 1994. WES personnel were onsite to 

 measure these rates. Data were collected from 10:00 a.m. to 1:00 p.m. Massive 

 overtopping of the structure occurred (Figure 21), and it is estimated that approxi- 

 mately 50 percent of the overtopping waves were not collected due to spray and 

 waves "overshooting" the container. During the storm the apron extending from the 

 top of the container up the slope of the breakwater collapsed, as shown in Figure 22. 

 Before the storm system subsided, the forces of the overtopping waves caused the 

 anchors to pull out of the concrete slab. The container tilted forward (shoreward), 

 bending the pipes used to measure the flow rates. Due to logistical problems, it was 

 not feasible to repair the container. Therefore, data obtained initially on 3 Novem- 

 ber 1994 were the extent of the wave overtopping obtained during the monitoring 

 effort. 



Bathymetry 



Bathymetric data in and adjacent to St. Paul Harbor had been obtained in 

 September 1986 (prior to construction of breakwater improvements) and again in 

 August 1992 (after breakwater construction). These pre- and post-construction data 

 were analyzed to determine the impact of the improvements on bathymetric condi- 

 tions in and adjacent to the harbor. An additional bathymetric survey was com- 

 pleted in July 1995 as part of the monitoring program. This survey was analyzed 



26 



Chapter 2 Monitoring Program 



