CHAPTER 7. CONSTRUCTION CONSIDERATIONS

47. INTRODUCTION.

a. Philosophy. Because of the variety of structures that have been used satisfactorily in various regions of the Country, this section emphasizes general design considerations instead of specific plans and details. By following these recommendations, structures can be constructed that are tailored to individual need, finances, and local conditions.

48. PRESERVATION.

a. Marine Borers. If marine structures are to give long service, it is imperative that timbers be protected from attacks by various insects, fungi, and marine borers. The termite, which is the most common, inhabits many parts of the United States and Canada. It frequently enters the wood at or near the ground line. Fungi may develop any time there is a proper amount of air, warmth, food, and moisture. The discharge of various waste materials into bodies of water is conducive to the growth of wood destroying fungi. The prevalence of marine borers is worldwide, and although they are usually found in salt or brackish waters, slight infestation may be found in rivers above the point of brackishness. No corrosive materials or untreated timbers should be used in salt water.

b. Preservatives. Some of the more generally used preservatives in marina construction are creosote, chromated copper arsenate (CCA), and ammoniacal copper zinc arsenate (ACZA). These treatments have advantages and disadvantages, depending on how the wood is used. The most effective type of wood treatment is the pressure process which forces the preservative into the wood. This pressure process may be either the full cell or empty cell treatment, which differ in the amount of preservative retained in the wood.

c. Piling Protection. In areas where Teredo and pholad attack are expected or known and where Limnoria tripunctata attack is not prevalent, creosote or creosote solution treatment will provide adequate protection. In areas where Teredo and Limnoria tripunctata attack is expected or known and where pholad is not prevalent, either dual treatment or high retention of ACZA or CCA treatment will provide adequate protection. In areas where Limnoria tripunctata and pholad attack is expected or known, dual treatment provides the maximum protection. Proponents are urged to consult with local experts, engineers, the American Wood Preservers Institute, and the National Timber Piling Council, Inc., prior to using any treated lumber or piling on a project.

d. Hinged Connections. Special provisions must be made so that attachment booms and gangways can adjust to fluctuations in water level. One method is to install a fixed hinge at the shoreline in combination with another hinge on the float or runners for the gangway to slide on as the water level changes.