There is a lake near me that needs to be dredged, and they are running into the same thing with the hazardous material thing. Different reason, but the same obstacle. Its a developed lake with houses all around it, so no place to put the spoils. Can't haul it on the roadway for fear of "dropping" some, so that option is out.

What I am getting at: Is there an option to dig a pit near the pond to put the spoils into? Use the dirt that comes out of the pit to redirect the bad run-off from the farm. Or, would the farmer allow you to put the spoils on his property? That way you go directly there without involving any outside authorities.

It still don't negate the fact it costs money, and possibly the quotes you got already considered these options.