No. The ACHP’s regulations do not require the identification of all of the archaeological sites within the area of potential effects (APE). Rather, federal agencies are expected to make a “reasonable and good faith effort” to identify historic properties, including archaeological sites listed or eligible for listing on the National Register in the APE. An agency’s identification effort can be considered reasonable and in good faith when it has appropriately taken into account the factors specified in 36 CFR § 800.4(b)(1) - past planning, research and studies, the magnitude and nature of the undertaking and the degree of federal involvement, the nature and extent of potential effects on historic properties, and the likely nature and location of historic properties within the area of potential effects.
One of the reasons the ACHP’s regulation contains a post-review discovery provision [36 CFR § 800.13]1 is that the level of effort is reasonable and in good faith, not 100 percent or exhaustive. The costs attendant with work stoppage because of a discovery should be reason enough for a federal agency to put forth a competent professional effort at the identification stage.