What you have looks great! There is a typo i believe in the sentence: "The spillway has sits at an elevation of 1,373 feet. the dam was completed with three 40-foot wide by 30-foot high spillway gates".
If you are wanting to add more I would suggest adding to the environmental impacts the construction of the dam has created on the local ecosystems. Maybe you could look at how it has affected a certain fish species especially if they are migrating fish.
Also, I'm not sure if you have your references on another page or something, just don't forget to cite what you have written. If you want me to check back and reread it after you add more let me know. Good luck!