The St. Paul Harbor main breakwater is currently functioning in an acceptable 

 manner and is in good condition structurally; however, the armor stone continues to 

 degrade. The number of broken/cracked armor stones on the 320-m-long (1,050-ft- 

 long) breakwater extension increased from 73 in July 1993 to 230 in June 1996. A 

 geologic assessment indicated that about 25 percent of the original stone placed was 

 geologically unacceptable, and a significant amount of the stone on the structure 

 was blast damaged. Continued deterioration is predicted due to freeze-thaw and 

 wet-dry cycles as well as large waves and sea ice action. 



Photogrammetric analysis of the St. Paul Harbor main breakwater proved to be 

 an excellent tool in mapping the above-water portion of the structure extension and 

 quantifying changes in elevation. Results revealed most of the breakwater extension 

 was below its design elevation. Almost a third of the higher portion of the break- 

 water seaward of the harbor roadway was at least 0.61 m (2 ft) below its design el 

 of +11.3 m (+37 ft). Analysis also indicated essentially no change in el of the 

 breakwater crown between 1994 and 1996. 



Recommendations 



Extra precautions should be taken when monitoring future projects in extremely 

 high- wave-energy environments to ensure that required data are obtained. The loss 

 of the prototype wave gauges and the destruction of the wave overtopping container 

 reduced the value of the monitoring effort at St. Paul Harbor. In the future, in-depth 

 research of conditions should be conducted to assure success. 



When monitoring projects in remote areas, logistical problems may be experi- 

 enced. Delivery dates and/or availability of equipment, supplies, materials, etc. are 

 uncertain. These problems should be considered during the development of future 

 monitoring plans in remote locations. Additional time and costs associated with 

 these problems also should be considered. 



The St. Paul Harbor main breakwater should be observed very closely due to the 

 continued degradation of armor stone on the structure. Preparatory work for repair 

 considerations should be initiated since the deterioration rate is not expected to 

 decrease. When repair or rehabilitation occurs, the highest grade of geologically 

 acceptable stone should be placed above the waterline. Inspection of 100 percent of 

 shot stone for near-invisible hairline blast fractures also should be conducted by 

 skilled personnel. Only the most sound and durable stone should be used in this 

 extremely harsh environment. 



58 



Chapter 3 Conclusions and Recommendations 



