Gold behind Dam?

[Smokehouse_83]

Just found out the city is dredging the river behind a dam they use to catch water for their city water holding ponds and me and a buddy got access to the dirt. I've never panned in the river because I am new to this gold stuff and have been waiting on warm weather and time, but I've heard that people make good money working the river upstream closer to the head waters. What do you guys think the chances of this stuff being full of gold? We had a 100 year flood two years ago on the river, it rained for a week straight. I ran the Grizzly Gold Trap in the river way downstream by my house two weekends ago and found nothing so I'm thinking something is catching or caught all the yellow.
We are contemplating building a self contained 55 gallon barrel trommel on a trailer to run the stuff. So whats the word on gold being caught in front of dam's?

 

[MTTreasureHunter]

Hello If there were or are Precious Metals in the dam reservoir they would be concentrated mostly around the mouths of the incoming rivers the more powerful the runoff the further out but generally 50 to 150 out also if you can find out where they dumped any soil from that aera it would be a helpful start