scientology-connected narconon wants to build center at trout run .
land use laws mean that it must prove site is historic in order to have a medical facility on the land in frederick county .
scientology-affiliated real estate company bought land for $ 4.8 million .
group contends land is significant because herbert hoover fished there .
organization has been criticized after string of mysterious deaths at centers that use saunas and megadoses of niacin to treat drug addicts .