In working on linear historic sites in Montana, Utah, Idaho, and Washington
I've found quite a variety of thinking on how to assess impacts. The most
common I've encountered from SHPOs is to record the entire site then figure
out what percent of it will be altered by the proposed action and whether
any features critical to the site's integrity will be lost to construction.
If the percents are low and no nifty features will be sacrificed, the answer
is often no adverse effect and some SHPOs occasionally go for no effect.
--
Lee Bennett
Bennett Management Services LLC
Monticello, Utah
435-587-2556 phone & fax