They’ll probably set up the batch plant adjacent to the pile of rock and concrete they dug up from the riverbed. From there, they’ll set up a belt conveyor over to Moonbeam Canyon. As the mix is placed, dozers will spread and rollers will compact. The RCC will be a “hardened fill.”
Once the canyon is filled, then a conventional slab spillway will be built atop the concrete fill.
That’s my guess.
LOL - I laugh every time I see "moonbeam canyon".
Let's hope that the conventional slab is about twice as thick as the broken one, and with a lot more rebar and anchoring.