43 CFR 11.35: How does the trustee decide whether to use Type A or Type B procedures?

(a) If the natural resource trustee determines under § 11.34 that a Type A procedure is available, the trustee must then decide whether to use that procedure or use a Type B procedure. The trustee must make this decision by weighing the difficulty of collecting site-specific data against the suitability of the averaged data and simplifying assumptions in the Type A procedure for the release being assessed. The trustee may use a Type B procedure if they can be performed at a reasonable cost and if the increase in accuracy provided by those procedures outweighs the increase in assessment costs.

(b) If there is no appropriate Type A procedure, the trustee must use a Type B procedure to calculate all damages.