In addition to the requirements of subparts A and B of this part, a claimant must establish—

(a) The nature of the specific public services provided and the need for those services;

(b) That the services occurred during or after removal activities;

(c) That the services were provided as a result of a discharge of oil and would not otherwise have been provided; and

(d) The net cost for the services and the methods used to compute those costs.