bturk - if I remember my chem classes, the ice on the pond will be more or less fresh and the salt will be left in solution in the water under the ice. I don't think it is a real problem with corroding ice skate blades since they use a retention pond in Szeged Hungary as a skating rink in winter. That pond is the only one that I saw in the City that obviously was man made. The only other drainage retention area (DRA) I saw looked to be a low spot and was just left full ow willow trees. made a nice green spot in a neighborhood. Without the extensive parking lots we have to have here, its possible to not have a DRA every block or so. Seems to me that parking lots are perhaps the major issue in urban form between Hungary (maybe most of Europe?) and North America.
Planner Girl - We have a large 10 plus acre regional retention pond in Tallahassee, that seems to be ok for ducks and other water birds. And it has the start of vegetation around the edges.
We also have a smaller 5 ? acre "Lake" near the city center that is really a retention area. It is used as the centerpiece of an urban park... sidewalk all around it, a fountain in the Middle (important for water quality dissolved O2 in summer), tot lot , ducks, geese and the long leg waider once in awhile. It works well, but had to be cleaned out a year ago after many years. So plan on cleaning silt and crap off the bottom every 10 years or so.
