[EarthResearcher333]

Upper Main Spillway Cut Blocks - Workers hammering/chiseling along seams and Concrete Drain Line Cracks.

More photos & discussion:

One close up looks to reveal the bell coupling to a slab drain pipe. Note the crack above the drain in the concrete. Not sure where the dirt/soil came from. The depth of the concrete at this location is inferred at or near 2.5 feet as measured by the foot markers. One worker looks to be hammering out a channel that might be above another drain line. Two on the left may be working on a drain crack line. The worker on the right is chipping/chiseling out the grout placed in a slab joint seam.

The Cut Blocks appear to be spaced and aligning with original Slab Drain lines. (the worker with the hammer is sure pounding away).

[Repeal The 17th]

The bell couplings are oriented towards the “upflow”,
I think that is a “male” pipe end.

[EarthResearcher333]

Seems they didn't like a section of the Upper Main Spillway - New Blast pile - Cavern under spillway slab.

The prior cut blocks to the drains in the center of the spillway look to be resealed (unless the photo angle gives this illusion).