Engineering drawings, is NRCS involved?

I can't read any of the details as rendered on my computer (and eyeballs). Looks like a beauty, though!

Do you have enough clay on site for the core trench of the dam?

Any rocks or big sand layers in the sub-grade? You can easily build to the design, if all of the material behave. If you have a chance of material that might not behave, then be flexible on changing the plans as needed.

Will part of the excavation be below the groundwater table? Contractor prepared to continually drain the site knowing that ahead of time will make things go much more smoothly.

Good luck on your new build!