which time the north jetty was 7,490 ft long and required 441,237 tons of 

 stone, and the south Jetty was 3,945 ft long and required 196,860 tons of 

 stone. Both jetties had a crest elevation of +15 ft mllw, crest widths of 15 

 to 20 ft, and side slopes of 1:1.5 to 1:2, 



96. The north jetty was rehabilitated during 1957 to 1958. A 600-ft 

 extension to the north Jetty was authorized in 1958, but it was deferred 

 until, in the opinion of the District Engineer, the extension was advisable. 

 In 1981, the Design Memorandum was prepared for extending the north Jetty by 

 2,000 ft, including the 600-ft extension authorized in 1958, and extending the 

 south Jetty by 2,500 ft. The extensions have not been constructed. A chro- 

 nology of events related to the development and repair of the jetty structures 

 is given in Table 29. 



Tillamook Bay, Oregon 



97. Tillamook Bay is located on the Pacific coast of Oregon, about 

 47 miles south of the Columbia River. The project includes two rubble-mound 

 jetties protecting the entrance to the bay and a dike repairing a breach in a 

 spit on the westerly side of the bay. 



98. The 5,700-ft-long north Jetty was authorized in 1912 and con- 

 structed during 1912 to 1914 to 5,400 ft. The Jetty was reconstructed during 

 1931 to 1933, including a 300-ft extension, to the full authorized length. 

 The jetty was rehabilitated during 1963 to 1965 to repair damage caused by 

 undermining of the structure. The Jetty head has received some damage from 

 extreme wave conditions, but no improvements are planned at this time. 



99. The 8,000-ft south Jetty was authorized in 1965, and construction 

 of the first 5,000 ft was initiated in 1969- Deep scouring of the bottom 

 ahead of the Jetty caused overruns, and construction was halted at a length of 

 3,695 ft in 1971. The jetty was extended 2,830 ft during 1972 to 1974, and 

 the distance between the Jetties was decreased from 1,400 to 1,200 ft. The 

 Jetty was extended to the full authorized length of 8,000 ft during 1978 to 

 1979. The final leg of the Jetty has shown some subsidence, but no repair 

 work is planned at this time. A chronology of events related to the develop- 

 ment and repair of the jetty structures is given in Table 30. 



Umpqua River, Oregon 



100. The Umpqua River flows into the Pacific Ocean on the Oregon coast 

 about 178 miles south of the Columbia River. The town of Reedsport, Oregon, 

 is located 12 miles upstream from the mouth of the river. 



29 



