MIL-HDBK-1011/1
drainage and erosion control plan be prepared for the site as a part of the
design package.
2.4
Pile Foundation Systems. In certain coastal areas of the tropics,
such as Pearl Harbor in Hawaii, Apra Harbor in Guam, and Subic Bay in the
Philippines, thick layers of soft marine sediments often cause difficult
design problems for naval shore facilities. Consider pile foundation systems.
Design and construction guidelines and specifications for pile foundation
systems are given in NAVFAC military handbooks. However, no determination or
selection of a pile foundation system can be made until a thorough site
investigation, including subsurface borings, has been made and evaluated.
2.4.1
Precast Concrete Piles. Concrete piles are the most often used and
preferred pile foundation system in the tropics because of their durability
and ease of manufacturing. The selection of pile size and casting length is
often dictated by the capability and the availability of construction
equipment. Therefore, determining local construction capabilities is an
important factor in pile design. Prestressed, precast concrete piles, if
available, are a preferred choice because of their superior corrosion
2.4.2
Timber Piles. Timber piles are often used on waterfront projects
for ship mooring dolphins and wharf fender systems because of their high
energy absorbing characteristics. Wood in a tropical environment is very
susceptible to decay fungi, termites, and other wood boring insects and marine
borers. To resist deterioration, pressure treat marine piles in areas where
Limnoria Tripunctata (gribbles) are active with a waterborne arsenical salt
such as chromated copper arsenate (CCA), ammoniacal copper arsenate (ACA), or
ammoniacal copper zinc arsenate (ACZA) in accordance with the American Wood
Preservers Bureau (AWPB) Standard MP4, Standard for Marine Pilings Pressure
Treated with Creosote, for Use in Marine Waters, to a retention of 2.5 pounds
per cubic foot (pcf).
In waters infested with both limnoria and teredines (shipworms),
use dual treated piling with 1.0 pcf of a waterborne arsenical salt and 20 pcf
creosote in accordance with AWPB MP-1, Procedure for Dual Treatment of Marine
Pilinq Pressure Treated With Water-Borne Preservent and Creosote for Use in
Marine Water. Creosote treated piling is only effective against teredines and
pholads; in those waters use piling treated according to the AWPB Standard
MP2, Standard for Marine Pilings Pressure Treated with Creosote. for Use in
Marine Waters, at 20 pcf.
Most tropical waters will require either the waterborne arsenical
salt or the dual treated piling. Properly selected marine piling can be
expected to provide a normal service life of at least fifteen years. Piling
subjected to excessive physical contact and damage may require more frequent
replacement.
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