The final improvement plan (Plan 19) was developed as a result of the pre- 

 liminary experiments. Plan 19 (Plate 10) consisted of a 107-m-wide (350-ft- 

 wide), 6.7-m-deep (22-ft-deep) entrance channel and a 6.7-m-deep (22-ft-deep) 

 turning area (adjacent to the docks on the causeway) . From this point the channel 

 transitioned to 45.7 m (150 ft) in width and 3.7 m (12 ft) in depth and extended 

 approximately 274 m (900 ft) where it again transitioned to 3 m (10 ft) in depth 

 before extending to the north through the sand spit into Snake River and then 

 easterly to the existing harbor. The breach in the existing causeway was widened 

 to 18.3 m (60 ft) with a depth of 2.4 m (8 ft), and a 6.7-m-deep (22-ft-deep) 

 deposition basin was included eastward of the breach. The plan also entailed a 

 71.6-m-long (235-ft-long) rubble spur breakwater extending to the south from the 

 causeway. The spur had an 8.8-m-wide (29-ft-wide) crest with an elevation of 

 +4.3 m ( + 14 ft) and was armored with 19,958-kg (22-ton) stone on 1V:1.5H 

 side slopes. Underlayer stone ranged from 1,361 to 2,495 kg (3,000 to 5,500 lb) 

 and core stone ranged from 0.45 to 295 kg (1 to 650 lb). Thicknesses of the 

 underlayer and armor layer stone were 2.1 and 4.6 m (7 and 15 ft), respectively. 

 Also in-cluded in the plan was a new 909.8-m-long (2,985-ft-long) rubble-mound 

 breakwater. The breakwater originated approximately 579 m (1,900 ft) east of 

 the causeway and extended seaward 457 m (1,500 ft) parallel to the entrance 

 channels before turning slighdy southwesterly. The breakwater had a 3.7-m-wide 

 (12-ft-wide) crest with an elevation of +4.3 m (+ 14 ft) and was armored with 

 7,257-kg (8-ton) stone on 1V:1.5H side slopes. Underlayer stone ranged from 

 363 to 907 kg (800 to 2,000 lb) and core stone ranged from 0.45 to 295 kg (1 to 

 650 lb). Thicknesses of the underlayer and armor layer stone were 1.5 and 3 m 

 (5 and 10 ft), respectively. The new breakwater included a 9.1-m-wide (30-ft- 

 wide) breach approximately 244 m (800 ft) seaward of its origination point. The 

 navigation opening between the new breakwater toe and the causeway extension 

 toe was 115.8 m (380 ft) wide. The existing entrance to the small-boat harbor 

 also was closed for this plan. 



Wave height experiments 



Wave height experiments were conducted for existing conditions and various 

 improvement plans for representative experimental waves from the various 

 incident directions. Experiments involving some proposed plans were limited to 

 the most critical direction of wave approach. Wave gauge locations are shown in 

 referenced plates. 



Wave-induced current patterns and magnitudes 



Wave-induced current patterns and magnitudes were obtained for existing 

 conditions and selected improvement plans for representative experimental waves 

 from the various incident directions. These experiments were conducted by 

 timing the progress of a dye tracer relative to a known distance on the model 

 surface at selected locations in the model. 



Chapter 4 Experiments and Results 2 1 



