slopes of the south jetty system were in good condition, with the excep- 

 tion of the jetty head and the jetty spur head as previously discussed. 



Umpqua River Training Jetty, Oregon 



The Federal Navigation Project at the Umpqua River lies within the 

 lower 19 km (12 miles) of the Umpqua River Estuary. The river entrance 

 is located on the southern Oregon coast approximately 290 km (180 miles) 

 south of the Washington State border and 650 km (405 miles) north of San 

 Francisco Bay, California. Prior to navigation improvements, the river 

 was connected to the ocean through a 275-m-wide (900-ft-wide) gorge. 

 The first major effort to improve the river entrance for navigation was the 

 construction of a 1,035-m-long (3,390-ft-long) north jetty by local inter- 

 ests during the period 1916-1919. In 1930, the north jetty was extended 

 to its present 2,440-m (8,000-ft) length. A short 762-m-long (2,500-ft- 

 long) south jetty was constructed in 1934 and extended to its present 

 length of 1,280 m (4,200 ft) in 1938. A 7.9-m-deep (26-ft-deep) mllw 

 navigation channel, which extended upstream, also was completed in 

 1938. The north jetty was rehabilitated during 1941-1942, and a concrete 

 cap was placed on the outer 1,210 m (3,975 ft). This system did not pro- 

 vide a satisfactory entrance due to ebb tidal currents contributing to dete- 

 rioration and subsidence of the south jetty. In 1951, a 1,290-m-long 

 (4,240-ft-long) training jetty was constructed generally parallel to the en- 

 trance channel, and in 1964 a major rehabilitation of the south jetty was 

 completed. The training jetty was extended 790 m (2,600 ft) in 1980 to 

 the head of the existing south jetty. In general, the training jetty paral- 

 leled the entrance channel and the north jetty. A layout of the structures 

 is shown in Figure 21. The jetties were of randomly placed rubble-mound 

 construction. The main jetties were armored with 9,070- to 15,420-kg 

 (10- to 17-ton) stone. Armor stone on the channel side of the training 

 jetty averaged 9,070 kg (10 tons) and that on the embayment side aver- 

 aged 2,720 kg (3 tons). 



The training jetty at the mouth of the Umpqua River was monitored 

 during the period May 1983 through May 1984 (Herndon et al. 1992). 

 The objective of the monitoring study was to determine if the training 

 jetty was maintaining the navigation channel as predicted by physical 

 model studies. 



The training jetty and south jetty were inspected on 25 June 1997. In- 

 spection of the training jetty revealed that the 1980 extension was in very 

 good condition (Figure 22). Its cross section appeared to be uniform 

 along its length, and very few of the armor stones had cracked. The shore- 

 ward portion of the structure (1951 construction) had some areas that ap- 

 peared to be damaged on the shore side. This was prevalent immediately 

 landward of the shoreline where stone from the back side of the jetty was 

 scattered (Figure 23). The channel-side face of this portion of the train- 

 ing jetty was in good condition. Inspection of the south jetty revealed a 



Chapter 2 Project Descriptions and Inspection Results 



21 



