Plastic films 20 to 40 mils thick have been used for many years to wrap creosoted timber piles in service to protect them from attack by marine borers. As long as the wrap remains undamaged, this procedure provides complete protection to the pile. Properly applied, wraps generally provide protection for 25 yeara or longer. Polyvinyl chloride (PVC) and polyethylene (PE) films are specially formulated for long service, especially in the intertidal zone where they are exposed to sunlight, wave action and abrasion. Carbon black and other inhbitors are used to prevent degradation from the sun's actinic radiation and embrittlement. The Port of Los Angeles requires a minimum carbon black content, film weight basis, of 1.5% for PVC and 2% for PE. The films differ in handling characteristics in water. PVC is tougher and more flexible than PE but tends to sink whereas PE lends to float. Initially PE is less flexible than PVC but, with time, PVC can lose its plasticizers becoming harder and more brittle than PE. PVC wraps have been in service about 25 years and PE wraps for 5 years with only scattered reports of polads (Martesia) penetrating PVC in Hong Kong, Panama and Brazil. The extent of attack appears slight. Films 10 mils or less in thickness can be damaged by crabs and other marine animals capable of grasping and tearing the film. Usually a diver wraps the film around and fastens it to a pile in place. A diver and a support crew of one or two persons wrap up to 250 linear feet of piles per day at a labor cost of over $900. Depending on diving conditions, the labor cost for wrapping piles ranges from $4.50 to $10.00 per linear foot of pile.

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