Figure 7-24. - Broken wood piles.

cut off as far down as possible and a new pile driven alongside of it. After driving, the head of the new pile is pulled into place and fastened to the cap with a driftpin or with the use of fishplates (fig. 7-25). Treated replacement piles should be used for all structural pier piles; however, on major operations and supply piers, where the life expectancy of the fender system is relatively short because of its continued exposure to the berthing of major ships, the use of untreated, unskinned piles may be considered structurally suitable and economically sound.

Piles that have been weakened by marine borers can be strengthened and protected by encasing them in concrete jackets. Steel reinforcing can be used in the concrete jacket either in the form of bars or wire mesh. Concrete encasement may be used to cover a short section of the pile where damage is limited, as shown in figure 7-26, or may be extended well below the waterline, as shown in figure 7-27. The damaged surface of the pile must be scraped to sound wood. Either metal or wood forms may be used. If wood forms are used, a 2-inch creosoted tongue-and-groove material should be used and left in place. Fender piles that are broken between the top and bottom wales, as shown in figure 7- 28, can be repaired by cutting off the pile just below the break and, then installing a new section of pile and fitting. Place and bolt a pile section or timber section directly behind the fender pile from the top to the bottom wales. A metal wearing strip should be spiked to the wearing edge of the pile.

Figure 7-25. - Wood pile replacement.

Figure 7-26. - Concrete encasement of short section of wood pile.

Sheeting Piers and quay walls may have a bulkhead of wood sheet pile to retain the fill on the shoreside. Riprap is usually placed at the foot of the sheeting for strengthening. Extensive deterioration of the bulkhead will result in the loss of fill and settlement above the affected area. Repairs usually require the driving of sheetpiling to form a new bulkhead a minimum of 1 foot inside the old one to avoid the driving frames or wales attached to the old bulkhead. New sheetpiling may be pressure-treated wood, concrete, or sheet steel. Steel sheetpiling is normally used for the new bulkhead because oftentimes the work must be done inside a pier shed. In this case, steel piling is driven in maximum lengths possible and additional lengths welded on successively. The new sheet pile should