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Figure 1 . Project location 



With the successful construction of north and south jetty structures to stabilize 

 the entrance to Yaquina Bay, OR, during the period 1881-1892, the Corps believed 

 that a similar jetty structure would stabilize the spits at the entrance to Humboldt 

 Bay and help to establish a reliable navigation channel by confining the tidal cur- 

 rents. Construction of the south jetty at Humboldt Bay began in 1889. The con- 

 struction technique involved building a trestle over the footprint of the proposed 

 structure and using specially designed railcars to then dump rock weighing up to 

 7,260 kg (8 tons). Scour mats made from willow branches were fabricated and 

 submerged by loading them with rock. The dumped material was allowed to assume 

 its angle of repose, but heavy seas would flatten the slope further. Slope flattening 

 was combated with the placement of more material. Later, as the project pro- 

 gressed, it was found that scouring was occurring around the trestle piles faster than 

 the brush mats could be placed. It was soon discovered that a 0.9-m- (3-ft-) thick 

 layer of small stones could be used as scour protection and could be placed more 

 rapidly than brush mats. 



Chapter 1 Introduction 



