b. Foundations. Data on soil mechanics for the various substrata of the site are needed 

 to determine the holding resistance of guide piles, the probable lengths of bearing piles and 

 sheet piles required for bulkhead walls and building foundations, the bearing capacity of 

 spread footings, and the active earth pressures to be resisted by bulkheads and retaining 

 walls. Such data can only be obtained by testing core-borings or other undisturbed samples 

 of the substrata in a soils laboratory. 



c. Seismic Activity. Some areas are more prone to earthquakes than others, and all 

 structural works must be designed to resist these seismic forces. The United States has been 

 subdivided into seismic-risk zones according to historical seismic records, and local building 

 codes use this zoning in their design standards. Thus, harbor and related facility 

 construction in any metropolitan area will automatically be governed by the applicable 

 codes. Where local codes have not been prescribed, the Uniform Building Code (1970) gives 

 seismic-design data for buildings; the State of California Bridge Planning and Design Manual 

 (1969) gives seismic-design data for bulkheads and piling in water areas. If possible, areas of 

 active faults should be avoided in siting the harbor. 



d. Material Sources. Stone for breakwaters, jetties, and revetments is usually obtained 

 from the nearest developed rough-stone quarry. If a developed quarry is not near the site, it 

 may be advisable to explore the comparative cost of transporting stone from distant quarries 

 versus conducting a geologic exploration for a potential new quarry. Quarrystone should be 

 sound, durable, hard, and free from laminations, and of such character that it will not 

 disintegrate from the action of air, water, or conditions to be met in handling and placing. 

 Suitable fill material for the marginal area of the harbor is generally available from the 

 harbor excavations. Sometimes this is insufficient to meet the need for landfill or it is of 

 poor quaUty. Fill material then may have to be obtained from other nearby "borrow" areas. 

 Fill is usually not as difficult to obtain as stone, but, like stone, it must be of adequate 

 structural quality. Most clays and fine silts are too plastic for good foundations; the best is a 

 sandy material with the right amount of binder for good cohesion. A variety of qualities 

 may be found in between. Sand and silty sand can be compacted to maximum density by 

 flooding. Other soils must be compacted mechanically to a carefully regulated optimum 

 moisture content. If aggregates for concrete are not available commercially, gravel pits and 

 sand deposits may have to be located for this purpose. 



5. Project Impact on Environment. 



a. Water Quality. This subject has been discussed briefly in relation to site selection, 

 tidal, and riverflow factors. Water is particularly important for health and environmental 

 quality, especially in warmer climates where biological processes are accelerated. Successful 

 control of water quality is usually dependent on periodic exchanges of harbor water with 

 the main water body that the harbor serves. In flowing rivers, the problem is minimized 

 because the river currents will induce circulatory flow even in off-river basins. Tidal or 

 pseudotidal fluctuations are important factors in adequate water exchange in harbors. For 

 single-entrance harbors, an average daily exchange of water equivalent to about one-third of 



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