43 CFR §11.35

1. (a)If the authorized official determines under § 11.34 that a type A procedure is available, the authorized official must then decide whether to use that procedure or use type B procedures. The authorized official 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 authorized official may use type B procedures 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. Section 1, Volume I of the NRDAM/CME technical document (incorporated by reference, see § 11.18) lists the simplifying assumptions made in the NRDAM/CME. Volumes III through IV of the NRDAM/CME technical document list the data in the NRDAM/CME. Section 1, Volume I of the NRDAM/GLE technical document (incorporated by reference, see § 11.18) lists the simplifying assumptions made in the NRDAM/GLE. Volume III of the NRDAM/GLE technical document lists the data in the NRDAM/GLE.
2. (b)The authorized official must use type B procedures rather than a type A procedure whenever a potentially responsible party:
   1. (1)Submits a written request for use of type B procedures along with documentation of the reasons supporting the request; and
   2. (2)Advances all reasonable costs of using type B procedures within a time frame acceptable to the authorized official.
3. (c)If there is no available type A procedure, the authorized official must use type B procedures to calculate all damages.
4. (d)Except as provided in paragraph (b) of this section, the authorized official may change the type of procedure used in light of comments received on the Assessment Plan. [See § 11.32(e)(2) to determine if the authorized official must provide for additional public review.] However, if the authorized official decides to use type B procedures in lieu of a type A procedure, and cannot confirm exposure under § 11.37, the authorized official may not then use a type A procedure.