You could do a couple of things re: the poisons that might be there.
build your ponds--sounds like all you have to do is dig a hole- stock it with cheap goldfish and see if they die--or get the water tested to find out what you might be dealing with.
If there is a significant problem with the water quality you could set up reed beds to filter the water first (this is a good idea anyway to help keep sediment down in the pond) and they will pull out lots of the toxins.
the reed bed would basically be a basin that catches the runoff filled with gravel and bulrushes or cattails. If you ever decide to do a grey water system for your house that could use the same reed bed.
depending on your contours, you may have to do some sculpting to concentrate the flows and define an inlet on the far side of the bed from the pond.
The reeds will need to be harvested at intervals to unclog the beds, and the beds may be inactive for periods when it gets cold, but likely this won't make much difference to your fish.
If the runoff is super toxic you may need to get politically active --at least in the sense of going to your neighbors, explaining the problem and ask them to substitute non toxic lawn care--
http://whyy.org/cms/youbetyourgarden/ is one source for that sort of suburban/city advice on organic lawn care
right here on Permies would be another good source to research
If that fails and they are dedicated to supporting Monsanto, you may need to complain to your Board of Supervisors or Planning commission
If that fails, the next link in the chain of command might be the state DEQ or finally the Feds. Each step gets progressively more complicated and I always like to start informally with voluntary cooperation
This is a real problem in some areas, they say more chemicals are used on lawn care than on agricultural crops, but hopefully not in yours.