structure until sand has built up around the groin itself. Creosoted 

 timber piles eight to ten feet long are driven on -8 feet centers 

 along the centerline of the groin starting at high water line and ex- 

 tending to low water line with about four feet extending above the 

 surface of the sand. Hot sand-asphalt mix is placed around the piles 

 in a straight line to a height of about L, feet, the base of the groin 

 being about six feet wide. The apron, 15 feet wide and 2 inches thick, 

 is constructed along both sides of the groin and around the seaward 

 end. The asphalt is placed at a temperature between 250° and 300° F 

 and tamped while hot. The aprons on the sides are rolled with a small 

 hand roller. A typical section of this type of groin is shown in 

 Figure 14.6. 



20' 



1 E 



-Apron Extends Around 

 Seaward End of Groin. 



20' 



mm E 



I Creosoted Pile 8'- 10' Long 



I on 8' Centers 



FIGURE 146 -ASPHALT GROIN USING LOCAL BEACH SAND 



4.53. Selection of Type . - Every beach has its inherent physical 

 characteristics. These include the range of tide, littoral drift, beach 

 composition, wave characteristics, tidal currents, marine borers, and 

 beach dimensions and slope. Other factors to be considered include beach 

 and upland topography, the character of the foundation, the availability 

 and cost of construction materials, maintenance costs, economic life, 

 and the use made of the upland areas, .\fter planning considerations 

 have indicated that use of groins is practicable, the selection of groin 

 type is affected in overlapping and varying degrees by the foregoing 

 inter-related factors. 



217 



