The calculations required by this subchapter for each self-propelled hopper dredge must include--
(a) The free surface effect of consumable liquids and the free surface effect of the dredged spoil in the hoppers; and
(b) Either of the following assumptions when performing the calculations required by Sec. 174.310(b) of this chapter:
(1) If the dredged spoil is assumed to be jettisoned, the free surface of the dredged spoil may be disregarded.
(2) If the dredged spoil is not assumed to be jettisoned. the free surface of the dredged spoil must be calculated. [CGD 76-080, 54 FR 36977, Sept. 6, 1989]