The design principles discussed in the AWPI Technical Guidelines (App. B) are generally 

 applicable to steel sheet-pile construction by substituting the structural properties of the 

 steel members used for those of timber construction. Chaney (1961) also provides a treatise 

 on bulkhead design for steel and other materials. 



Several corrosion-retarding procedures have been devised for steel components in a water 

 environment, including galvanizing, aluminizing, flame -spray metal coatings, various types of 

 brush coatings, and cathodic protection. An excellent, economical coating for large 

 members is coal-tar epoxy, shop-applied to wlute metal steel surfaces and, before 

 installation, carefully examined for flaws with approved electrical equipment. Some coatings 

 are available for application in a wet environment, but experience records are too short for 

 reliable determination of their effectiveness. A 15-year experiment was started in 1967 

 (Watkins, 1971) to test the performance of 32 different systems of steel-pile protection in 

 the Atlantic Ocean off the Virginia coast. When completed, this test should provide some 

 fairly reliable data on protective systems in a marine environment. Meanwhile, a good 

 practice is to allow for the loss of 0.003 inch of metal per year from each surface of an 

 uncoated steel section of standard alloy content where the average water temperature ranges 

 between 50° and 70°F. in colder coastal waters (0.002 inch in freshwater). This factor may 

 be decreased sli^tly in colder waters, but must be increased significantly for higher 

 temperatures. A good preservative coating (applied to white metal) should double the 

 effective life of the section. An efficiently operating cathodic-protection system may extend 

 the life of the steel structure indefinitely, but it should be installed by an expert. 



Special precautions should be taken to avoid the use of different metals or even different 

 grades of the same metal in close proximity in seawater because of the galvanic action thus 

 induced. The low conductivity of freshwater does not present a galvanic-action problem, but 

 dissolved oxygen content and splash zone oxidation causes rusting. The Ph factor of the 

 water and the soil into which the piles will be driven should be checked and the 

 recommendations of a corrosion expert obtained wherever a metal sheet-pile system is to be 

 installed in freshwater. UhUg (1953) presents a detailed treatise on corrosion theory and 

 methods of retarding or eliminating corrosion. The compatibiUty of various metallic 

 fasteners with certain base metals in seawater is shown in Table 1. 



Concrete bulkhead walls come in a variety of sections and in combinations with other 

 types of construction. The most commonly used combination in marina construction is a 

 wall with a vertical or slightly battered face extending to about extreme low water level, and 

 a slope extending from that level down to the project depth of the marina. The slope should 

 be armored with riprap from the wall to about 5 feet below extreme low water to prevent 

 wave or eddy current scour at low water levels. Because of the danger of boats grounding on 

 the riprap slope, such construction should not be used where the bulkhead is marginal to a 

 navigation fairway unless the limits of the deepwater channel are marked with buoys, or 

 where berthing facihties or other structures prevent inadvertent navigation close to the wall. 

 This combination of concrete structure and revetted slope is often the most economical 

 solution. 



97 



