RE: SSc5.1: It looks like a greenfield site but may not be???

Hi All, I am working on a 200 acre site that looks like greenfield farmland. Aerial photos from the county that go back to the 1930's show that between the 1930's and 1980's there were as many as about a dozen small to medium size buildings on the property and what looks like a road or a very large driveway. These appear to have been demolished by the late 1980's and the entire site (minus the wetlands) seems to have been used as farmland for the last 25-30 years. In looking into whether or not to consider this previously developed/graded land with respect to SSc5.1, it appears that there is some grey area with respect to prior uses. One way to document a previously developed site is to find building permits. However, after contacting the town, I have learned that the town only keeps building permits going back six years. Therefore, the only evidence that I have of the former buildings and road on the site are aerial photos maintained by the county. Is this sufficient evidence to put forth the claim that the site is not a greenfield but a previously developed site and that therefore our project may comply with SSc5.1 by meeting the site restoration requirements for previously developed sites? We believe that it is. But we are also testing the claim. Thank you in advance for taking the time to review this inquiry. Joe