l;5'ij-» With considera-fcion to beach and upland topography, a steep 

 beach is an indication of hea-vy wave action and genera].ly requires sub- 

 stantial structures, usually of concrete, stone, or steels Under these 

 conditions light timber groins will not be adequate seaward of the crest 

 of berm. However, timber can be used for the inshore section above the 

 crest of berm if the beach is backed by sandy areas such as sand dunes. 

 On gently sloping beaches, lighter construction of timber, steel, or 

 concrete generally can be used except in the vicinity of inlets, the 

 cheaper construction being justified on the basis of its economic life. 

 A thorough consideration of foundation materials is essential to the 

 seleiction of groin type. Borings and probings should be taken to deter- 

 mine the subsurface conditions for penetration of piling. Where the 

 foundations are poor or where little penetration is possible, some type 

 of cellular or stone groin may be indicated despite its greater cost. 

 Good penetration may indicate the economy of sheet piling, provided 

 materials are available, 



h$^' Availability of raaterials affects selection of type because 

 of the economic aspects. It may happen that the material, which would 

 normally be the most economic with full consideration given to life of 

 the material and maintenance costs, is not available except at a cost 

 that would make some other material or type of construction more economic. 

 This involves the question of the economic life of the material together 

 with the annual cost of maintenance to attain that economic life. The 

 first costs of timber groins and of steel sheet pile groins, in that 

 order, are nearly alxirays less than for other types of construction. The 

 concrete groin is considerably more expensive, but usually costs less than 

 does the massive stone groin. However, concrete and stone groins require 

 less maintenance and have much longer economic life than do the timber or 

 steel sheet pile groins. With this in mind, and the amount of funds 

 available for initial construction, the period during which protection 

 will be required must be studied before deciding on a particular type. 



i;56. No universal plan of protection can be prescribed because of 

 the wide variation in conditions at each location. However, the informa- 

 tion required in a problem and the general factors to be considered to 

 determine the groin type are generally the sarae and depend on the location 

 and characteristics of the area for detail. The groins constructed at 

 Coney Island, j^^ew ^ork, are used as a typical exaniple to demonstrate 

 the selection of type. These groins were designed to retain the artificial- 

 ly placed protective beach. Profiles taken before fill or groin con- 

 struction was started showed a general slope of about 1 on 2ij., which 

 would be considered steep and ordinarily require heavy s tone structures. 

 However, good penetration could be obtained throughout the area, and 

 because the fill >7ould be added as the groin construction progressed, 

 providing protection from heavy viaves to the landward ends of the groins, 

 timber imperraeable groins l60 feet long, heavily creosoted to resist 

 attack by marijie borers, were chosen for the inshore section. Seaward 

 of this timber section, the groins were constructed of stone for a 



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