Couldn't edit my previous post to include this .
The short answer is NO, they cannot place the storm drain on your property without your permission if no easement exists.
You can negotiate and grant them an easement if you'd like. If you refuse, they will have to go to court, at which time you will have the opportunity to make your case why they shouldn't be granted an easement. If the court orders an easement be granted, you will have the opportunity to appeal any compensation they determine.
It would probably be in your best interest to stay out of court, and to set a reasonable compensation for granting them an easement.