Table 27 



Mission Bay Jetties 



Mission Bay Harbor, California 



Date(s) Construction and Rehabilitation History 



1949 Construction of three rubble-mound jetties at the site (Figure 34) 

 was completed. These structures included a 3,300-ft-long north 

 jetty, a 4,270-ft-long middle jetty, and a 950-ft-long south jetty. 

 Typically, the jetties were built with a 16-ft-wide crest at an el 

 of +14 ft mllw with side slopes of 1V:1.5H. 



1955 Sediment from the littoral zone was noted passing through the north 

 jetty into the entrance channel. Sealing stones (3,000 tons) were 

 placed on the seaward slope of the jetty. This measure retarded 

 the movement of sand but did not entirely stop infiltration. 



1959 Approximately 1,300 ft of the middle jetty and 1,000 ft of the 



north jetty were sealed with grout to prevent the movement of sedi- 

 ment through the structures. The original core stone of the jet- 

 ties was constructed at el 0.0 ft mllw. The intruded grout barrier 

 was installed to el +6 ft mllw. The cost of this work was $78,900. 



1970 A 1 ,100-ft-long extension and sealing of the south jetty were com- 

 pleted. Jetty sealing was accomplished by installing a 3-ft layer 

 of sealing stone in the littoral zone. The head of the middle 

 jetty also was repaired in that the cover stone (12- ton) at the 

 head of the jetty was restored. Total cost of the work was about 

 $566,000. 



1986 The existing jetties currently are in satisfactory condition. 



Design has been completed for an offshore breakwater located sea- 

 ward of the north and middle jetties that will provide additional 

 wave protection for Mission Bay Harbor. The proposed offshore 

 breakwater has been model tested (Curren 1983, Markle 1983, Bottin 

 and Acuff 1985) but not yet constructed in the prototype. 



57 



