Wood pilings that have been severed by marine borers have been success- 

 fully restored, in-place, by literally dozens of methods. Most of these are 

 based on external reinforcement, such as heavy wall steel pipe, overlapping 

 the upper and lower pile sections, followed by corrosion protection of the 

 steel by a plastic wrap. Small scale tests in the laboratory have proved 

 the efficiency of these methods in repairing piles, both in the bearing and 

 bending capacity, to achieve their full design loads. 



c. Synthetic Materials Wrap. Wood piles can be protected, in place, 

 from marine borer attack, by wrapping with flexible synthetic sheet such as 

 polyvinyl chloride (PVC) or polyethelene sheeting (cigarette fashion) from 305 

 millimeters (12 inches) below the mud line to 305 millimeters above the 

 highest tide line. In preparing a wood pile for a jacket it is important 

 that all sharp protrusions be removed. In case of barnacles, sharp edges 



can be smoothed by various simple hand or mechanical devices (Fig. 74). 



Modular kits are available which permit fast and positive application 

 from above or below water. This system effectively removes wood piles from 

 their environment. Marine borers attacking the piles while encapsulated 

 under the wraps die from lack of oxygen within 48 hours, while the synthetic 

 sheating prevents further intrusion. 



This system has been successfully used on both coasts of the United 

 States, Germany, Australia, the Bahamas, and elsewhere for more than 20 

 years. The U.S. Navy has also used the system on numerous projects (see 

 NAVFAC specification 75M-B10a) . 



Other methods of wrapping wood piles with synthetic film before driving 

 have also been tried as shown in Figure 75. Unless the piledriving crew are 

 very careful, the PVC jackets can be ripped during driving. Fortunately, 

 permanent repairs can be made by nailing patches of synthetic film over torn 

 areas with aluminum alloy 5056 roofing nails. 



d. In Place Treatment of Timber Cracks. If such cracks make the pile 

 structurally unsound and also expose it to internal marine borer action, 

 the crack can be bolted together with form-fitting steel washers on each 

 side of the pile by one or more bolts. The entire area should then be 

 jacketed with a synthetic film jacket. 



e. Replacement. In wood structures, parts such as framing members are 

 frequently repaired by replacement of the damaged member. Replacement is 

 relatively easy because the fasteners are usually in accessible places and 

 the wood members are in discrete sizes of individual pieces. When repairing 

 treated wood, treatment of the new member must be to the same specification 

 as the original. Cuts and bored holes are to be made prior to pressure 

 treatment in the shop when possible. Cut faces of pieces to remain in place 

 must be coated with similar material as the original. New fasteners should 

 be used where there is any damage or corrosion to the original. 



Damaged wood piles are removed by pulling, after removing deck and 

 stringers when present. Before pulling, remnants of the damaged pile and 



270 



