Table 11 



Charleston Harbor Jetties 



Charleston, South Carolina, SAC 



Date(s) Construction and Rehabilitation History 



1878- Rubble-mound jetties (Figure 18) with a shoreward submerged weir 

 1886 section and seaward raised section were constructed at Charleston 

 Harbor to provide (in conjunction with dredging) for a navigation 

 channel 21 ft mlw deep. The total lengths of the north and south 

 jetties were 15,400 ft and 19,100 ft, respectively. The distance 

 between the parallel seaward sections of the jetties was 2,900 ft. 

 Shoreward portions of both jetties, each approximately 6,000 ft 

 long, were built up to typical depths of -4 to -12 ft mlw (rising 

 only a few feet above the bottom, with low sections as deep as 15 ft 

 and 28 ft on the north and south jetties, respectively). The outer 

 7,200 ft of the north jetty was raised to an average of +7 to 

 +8 ft mlw, the outer 9,200 ft of the south jetty was raised to an 

 average of +10 ft mlw, and shoreward of this section an additional 

 2,400 ft was raised to +8 ft mlw. A typical section of the raised 

 jetties consisted of a log and brush mattress foundation loaded with 

 30 to 60 tons of small stone weighing 10 to 250 lb. An additional 

 narrow course of small stone was placed, and 1- to 7-ton granite 

 blocks were placed as cover stone. Typical crest widths were 12 to 

 15 ft, 



1935 Only minor dredging between the jetties has been required since the 

 project depth was increased in 1917 to -30 ft mlw. Field survey 

 showed very little deterioration to the submerged or raised portion 

 of the jetties. 



1966 Present channel depth of -35 ft mlw has been maintained since 1961. 

 An inspection survey in August 1966 indicated a general subsidence 

 of 1.5 to 3.5 ft along the raised portion of the jetties, with maxi- 

 mums of 5 and 6 ft over short sections of the north and south jet- 

 ties, respectively. 



1985 Present channel depth (-35 ft mlw) extends approximately 13,000 ft 



beyond the end of the jetties. There has been no history of mainte- 

 nance or repair to the jetties since their completion. 



34 



