Chanhassen, MN 9/23/2002 Two whitetail deer peer out of the brush at a passing visitor. The 500 acres on the border of Chanhassen and Chaska include a trout stream and a rare calcereous fen that supports threatened trout species. But the fen and the stream themselves are threatened by booming suburban development. Gov. Jesse Ventura vetoed a $1.5 million bond appropriation to buy part of the property last spring, and a purchase option ran out this month. On Monday the Seminary Fen property was named as one of 10 ``Twin Cities Treasures'' _ examples of rare or endangered open space _ that are objects of a new environmental preservation campaign.