There's a tank that has fallen under the minimum thickness per API 653 due to localized pitting.  Looking at Section 4.3.2, it appears that there's a method of averaging out the pits in Section 4.3.2.1 provided that the pits are "widely spaced" as specified in Section 4.3.2.2.

Here are my questions:
1.  If t_1 falls below t_min as specified in 4.3.2.1(e)(i) the tank must be taken out of service.
2.  If you're in an area with pitting, when determining L, t_2 is either the measured minimum thickness in an area or at least 0.6xt_min (4.3.2.1(e)(2)).
3.  If the minimum thickness is taken at any point on the tank is less than 0.5 x t_min, the tank needs to be taken out of service.
4.  If there are areas of corrosion that the minimum thickness is less than t_min, and if there are pits that their vertical dimensions exceed 2 inches in an 8 inch length, the tank needs to be taken out of service (4.3.2.2(b))