ENCLOSING DAMS. 



77 



Calais. 1 In carrying out the improvements to the harbour 

 very special precautions were necessary to protect the works 

 a large portion of which was on the foreshore from the action 

 of the sea. For this reason the dykes or dams had to be of 



Level of Coping 



FIG. 54. 



unusual dimensions. The most exposed portion of the work 

 was the protecting embankment of the sluicing basin, the level 

 of the beach at this spot being 1 1 feet below high water of high 

 spring tides. 



,- Coping _Leyel. 



H. W.O.S.T. 



L.W.O.S.T. 



SECTION OF EARTH DAM, CHATHAM EXTENSION. 



SCALE 



75 



FIG. 55. 



The dam (Fig. 56^ was formed of a heavy bank of sand with 

 a front slope of 2 to 1, heavily riveted with stone pitching 

 and supported at the foot of the slope by sheet-piling, which 

 was itself protected by a continuous toe of Portland cement 



1 Engineering, vol. xlvii. pp. 577, 609. 



