you could be right but there will also be Engineering, Environmental, Security & Administrative costs associated with the work; possibly more (such as a contingency). Often all the other stuff costs more than the actual work of digging and removal. These contracts are usually posted and your MLA could likely get the break down.
I had a look at the Jake's website and in the past they have dug all this stuff out without actually working in the river bed. They dig it out and leave a barrier between the pit and the river and then open a channel. This produces the big frog water holes coho love. I assume work has started. I drove over the Canal at the #1 Saturday. The river was love and clear.