(a) When an applicant can demonstrate that the strict application of the restrictions or requirements of sections 505.7-505.9 of this Part will cause practical difficulty or unnecessary hardship, any such restriction or requirement may be varied or modified, provided that the following criteria are met:

1. (1) no reasonable, prudent, alternative site is available;
2. (2) all responsible means and measures to mitigate adverse impacts on natural systems and the functions and protective values described in section 505.3 of this Part have been incorporated into the project design and will be implemented at the developer's expense;
3. (3) the development will be reasonably safe from flood and erosion damage;
4. (4) the variance requested is the minimum necessary to overcome the practical difficulty or hardship which was the basis for requesting it; and
5. (5) where public funds are utilized, the public benefits clearly outweigh the long-term adverse effects for any proposed activities and development.