The local protection program shall not preclude the continuation and expansion of existing nonagricultural uses on sites in Section 11 or 12 of Township 4 North, Range 1 West, Mount Diablo Baseline and Meridian, that were zoned for such uses as of January 1, 1977, and for the conduct of such uses so that they do not cause any substantial, adverse impact on the marsh. The local protection program shall also provide that any other use of these sites in the future shall be compatible with the preservation of the marsh and its wildlife resources.