(a) Each hopper dredge under this subpart must be shown by design calculations based on the assumptions under paragraphs (b), (c), (d), and (e) of this section, that it meets—

1. (1) The requirements in §§ 170.170, 170.173, and 170.300 of this chapter in each condition of loading and operation; and
2. (2) The survival conditions of § 174.320 in each condition of loading and operation assuming the character and extent of damage specified in § 174.315.

(b) The calculations required by paragraph (a) of this section must assume:

1. (1) The hoppers are full of seawater;
2. (2) The permeability of flooded spaces is as provided by Table 174.310;
3. (3) The equalization provisions of § 174.325; and
4. (4) The jettisoning provisions of § 174.330.

(c) The calculations required by this section must take into account a sufficient number of loading conditions to identify the condition in which the vessel is least stable, including, but not limited to, the most severe loading condition, and the:

1. (1) Specific gravity of the dredge spoil, from 1.02 up to and including the maximum required by paragraph (e)(1) of this section; and
2. (2) Draft, up to and including the draft corresponding to the working freeboard for the full range of trim.

(e) The following assumptions must be made when doing the calculations required by this section:

1. (1) Dredged spoil in the hopper is a homogeneous liquid with a maximum specific gravity for the areas of operation.

2. (2) When calculating the vessel's righting arm, it is assumed at each angle of heel that the vessel trims free and the trimming moment is zero.

   Table 174.310—Permeability of Floodable Spaces

   Spaces and tanks	Permeability
   Storerooms	0.60
   Accommodation spaces	0.95
   Consumable liquid tanks	0.00 or 0.95—whichever results in the more disabling condition.
   Machinery space	0.85—unless otherwise supported by calculations.
   Cargo tanks	Determined from the actual density and amount of liquid carried in the tank.