23 C.F.R. § 774.7 : Highways — FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION — RIGHT-OF-WAY AND ENVIRONMENT — PARKS, RECREATION AREAS, WILDLIFE AND WATERFOWL REFUGES, AND HISTORIC SITES (SECTION 4(F)) — Documentation

(a) A Section 4(f) evaluation prepared under §774.3(a) shall include sufficient supporting documentation to demonstrate why there is no feasible and prudent avoidance alternative and shall summarize the results of all possible planning to minimize harm to the Section 4(f) property.
(b) A de minimis impact determination under §774.3(b) shall include sufficient supporting documentation to demonstrate that the impacts, after avoidance, minimization, mitigation, or enhancement measures are taken into account, are de minimis as defined in §774.17; and that the coordination required in §774.5(b) has been completed.
(c) If there is no feasible and prudent avoidance alternative the Administration may approve only the alternative that causes the least overall harm in accordance with §774.3(c). This analysis must be documented in the Section 4(f) evaluation.
(d) The Administration shall review all Section 4(f) approvals under §§774.3(a) and 774.3 for legal sufficiency.
(e) A Section 4(f) approval may involve different levels of detail where the Section 4(f) involvement is addressed in a tiered EIS under §771.111(g) of this chapter.
(1) When the first-tier, broad-scale EIS is prepared, the detailed information necessary to complete the Section 4(f) approval may not be available at that stage in the development of the action. In such cases, the documentation should address the potential impacts that a proposed action will have on Section 4(f) property and whether those impacts could have a bearing on the decision to be made. A preliminary Section 4(f) approval may be made at this time as to whether the impacts resulting from the use of a Section 4(f) property are de minimis or whether there are feasible and prudent avoidance alternatives. This preliminary approval shall include all possible planning to minimize harm to the extent that the level of detail available at the first-tier EIS stage allows. It is recognized that such planning at this stage may be limited to ensuring that opportunities to minimize harm at subsequent stages in the development process have not been precluded by decisions made at the first-tier stage. This preliminary Section 4(f) approval is then incorporated into the first-tier EIS.
(2) The Section 4(f) approval will be finalized in the second-tier study. If no new Section 4(f) use, other than a de minimis impact, is identified in the second-tier study and if all possible planning to minimize harm has occurred, then the second-tier Section 4(f) approval may finalize the preliminary approval by reference to the first-tier documentation. Re-evaluation of the preliminary Section 4(f) approval is only needed to the extent that new or more detailed information available at the second-tier stage raises new Section 4(f) concerns not already considered.
(3) The final Section 4(f) approval may be made in the second-tier CE, EA, final EIS, ROD or FONSI.
(f) In accordance with §§771.105(a) and 771.133 of this chapter, the documentation supporting a Section 4(f) approval should be included in the EIS, EA, or for a project classified as a CE, in a separate document. If the Section 4(f) documentation cannot be included in the NEPA document, then it shall be presented in a separate document. The Section 4(f) documentation shall be developed by the applicant in cooperation with the Administration.

23 C.F.R. §774.7