D. Hazardous/Unusual Seafloor Conditions 



- If these conditions are encountered or anticipated, caution is 

 necessary 



- Design possible, but requires more detailed procedures than 

 presented 



Examples of Hazardous/Unusual Seafloor Conditions 



• Submarine lava flows occupying a relatively small and irregular area. 



• Small sediment channels, local extreme bottom slopes, cliff-like 

 topography, or giant seafloor ripples. 



• Erratics from ice-deposited glacial detritus. 



• Metallic nodules or "pavement" formations above soft sediments. 



• Sloping seafloor greater than 10 degrees. 



• Deep ocean siliceaous ooze (>30% biogenic and siliceous). 



• Clean calcareous ooze (>60% biogenic and calcareous). 



• Sensivity >6 in a cohesive soil. 



• Cohesive soil strength varying by more than 50% or + 100% from 

 typical profiles presented. 



• Unconsolidated or very high void ratio clays with c/p values near 

 0.1-0.15. 



• Thin sediment layer above rock. 



• Layered seafloors - soft sediment over stiff/dense sediment or vice 



