In 1890, it was observed that the stability of the north spit was being compro- 

 mised and that the channel was changing positions despite completion of the 930-m- 

 (3,040-ft-) long south jetty. A north jetty structure then was deemed necessary. 

 Construction of the north jetty began in 1891 and employed the same construction 

 techniques as those used to construct the south structure. The north jetty, although 

 started after the south jetty construction had begun, was completed in 1 897, before 

 completion of the south jetty. The total project was completed in 1899. The south 

 jetty had a length of 2,258 m (7,408 ft), while the north jetty had a length of 

 2,460 m (8,068 ft). The jetties were spaced approximately 640 m (2,100 ft) apart 

 and created a stable channel with depths averaging 7.6 m (25 ft). 1 



In 1899, the average cross section for the south jetty had the following charac- 

 teristics (U.S. Army Engineer District (USAED), Los Angeles 1986): 



Ocean-side slope 



1V:2.7H 



Channel-side slope 



1V:2.3 H 



Height 



+3 m (+10 ft) 



Shape (cross sectional) 



Trapezoidal 



Stone size 



Up to 7,260 kg (8 ton) 



Placement 



Random 



The average cross section of the north jetty in 1 899 had the following 

 characteristics: 



Ocean-side slope 



1V:1.9H 



Channel-side slope 



1V:2.4H 



Height 



+3.7 m (+12 ft) 



Shape (cross sectional) 



Trapezoidal 



Stone size 



Up to 7,260 kg (8 ton) 



Placement 



Random 



By 1910, both jetties had been battered down to below mllw and shoals at the 

 seaward ends of the jetties had become so severe that the structures' heads were 

 buried in sand. Reconstruction of the structures was approved in 1910, and con- 

 struction was initiated in 1911. Jetty restoration involved the use of the existing 



'All elevations (el) and depths cited herein are in meters (feet) referred to mean lower low water 

 (mllw). 



Chapter 1 Introduction 



