(a) For work accomplished prior to project authorization, the following local improvements can be construed as compatible and considered for credit:
(1) Work that would constitute an integral part of the Federal project as authorized (integral work);
(2) Work that would have been included in the Federal project if it had not been assumed to be part of the without project condition (external work); and
(3) Work that reduces the construction cost of the Federal plan (substitute work).
(b) For local work accomplished subsequent to project authorization, only work started prior to authorization, and for which credit consideration was requested by letter dated on or before 31 March 1987, is eligible for credit under the provisions of section 104. New non-Federal work initiated after project authorization, provided it is on an element of the authorized project, is subject to limited credit under a separate authority. Such work, if the sponsor desires related credit, should be undertaken under formal agreement pursuant to section 215 of the Flood Control Act of 1968 Pub. L. 90-483, approved August 13, 1968, as amended.
(c) All creditable non-Federal costs for compatible work, and related benefits, may be considered in the project economic evaluation and, to the extent the related benefits are required for economic justification, creditable costs shall be included in total project first costs. In any event, costs for compatible work shall be included in total project first costs to at least the extent that credit is actually given, including LERRD.
(d) Flood control projects authorized in Pub. L. 99-662 subject to sections 903 (a) and (b) or similar provisions 401(b) and 601(b)) of that act fall, with respect to crediting non-Federal costs, under this paragraph. (However, pending completion of the relevant procedural requirements for such projects, as set forth in those provisions of the act, section 215 agreements covering proposed non-Federal accomplishment of compatible work on the project will not be executed.) Works eligible for credit will be explicitly addressed in new project reports submitted to the Secretary of the Army pursuant to sections 903 (a) and (b) or similar provisions.
(e) Formulas for determining the amount of allowable credit in accordance with these guidelines are provided in Appendix B.