Table 48 



Twitch Cove and Big Thorofare River Jetties 



Somerset County, Maryland 



Baltimore District 



Date(s) Construction and Rehabilitation History 



1940 Two converging stone jetties were constructed with 23,000 tons of 

 stone at a cost of $112,000 (Figure 61). The north jetty was 

 2,070 ft long, and the south jetty was 1,800 ft long. The design 

 section included a crown elevation of +4.0 ft mlw, a crown width of 

 2.0 ft with the exception of the seaward 120 ft of the north jetty 

 which was 4.0 ft, and side slopes of 1V:2H, except for the bay side 

 of the north jetty which was designed for 1:1 along the landward 

 1,950 ft. No stone size details were given; however, a 1981 survey 

 indicated the side slope stone was approximately 1.5 tons, and the 

 core was of similar stone. The survey also revealed the single cap- 

 stone ranged from 2.0 to 3.0 tons. No apron or bedding was placed 

 during construction or subsequent repairs. 



1945 A condition survey was performed which indicated the north jetty was 

 in a severe state of deterioration. The seaward 1,300 ft of this 

 jetty had a typical subsidence of 0.5 ft below the original eleva- 

 tion, and the seaward 300 ft of this section had a range of subsid- 

 ence of 2.0 to 4.0 ft. The south jetty was flanked, and the seaward 

 400 ft of the south jetty had subsided 0.5 to 1.5 ft. The seaward 

 end of this section had subsided below mlw. Toe areas had scoured 

 from -5.0 to -7.0 ft mlw. 



1952 A condition survey was made on the north jetty. The seaward 570 ft 

 had a range of subsidence from 2.0 to 5.0 ft, and 700 ft landward of 

 this section had subsided 1.0 to 2.0 ft. Jetty cross sections indi- 

 cated most of the subsidence occurred on the bay side. Repairs were 

 made to the seaward 1,030 ft of the north jetty using original design 

 geometry to raise the crest elevation to +3.0 ft mlw. The cost of 

 the repairs and dredging was $33,000. 



1955- A condition survey performed on the south jetty indicated an aver- 

 1956 age subsidence of 0.5 ft over the entire length. The seaward 300 ft 

 had subsided 2.0 to 4.0 ft, and a length of 80 ft had subsided near 

 the landward end. Areas of subsidence were typically 1.0 to 2.0 ft 

 below adjacent sections. Repair work began in 1956 to raise the 

 crest elevation to +3.5 ft mlw using original design geometry. Ap- 

 proximately 1,000 tons of stone were used at a cost of about $35,000 

 which included dredging. Toe areas had scoured to -9.0 ft mlw. 



1962 Both jetties were surveyed and repaired with 2,200 tons of stone for 

 approximately $64,500. The north jetty had been flanked on the 

 landward end, and elevations of the seaward 520 ft ranged from +1.0 

 to +3.0 ft mlw. The seaward 180 ft of the south jetty had elevations 

 ranging from 0.0 to +4.0 ft mlw. The above sections were repaired to 



(Continued) 



97 



