Sounds like miscommunication on the Officer's part. If you could not see him, and therefore could not be aware of any hand signals, you should not have been cited. If you did not drive around anything blocking the road, you should not have been cited. It appears the Officer ASSUMED other traffic would "know what to do"... it does not work that way in many cases, read the statute for details.
If you fight it, use a diagram like posted here AND take pics of the location. Your defense hinges on 1) you received no direct communication or orders from the officer; 2) no barricades or vehicles were blocking your turn; and 3) your turn was free of obstruction and posed no danger or obstruction to the operations going on.
In other words, you need to demonstrate that it was reasonable to make the turn...