The Gravois is the western arm. Sunrise Beach is near the mouth, Laurie is up the arm, and Gravois Mills is farther still. Weekend traffic is heavier near the mouth than in a back cove. Ameren does not publish a wave height for either. It does publish how long a dock may be, and that is the number that decides whether a plan is even worth pricing.
Which limit applies
In a cove up to 500 feet wide, a dock and any breakwater may not extend more than one-third of the distance to the opposite shore, or closer than 25 feet to the center, whichever is more limiting, and never more than 100 feet.
In a cove wider than 500 feet, the cap is 20 percent of the distance to the opposite shore, up to 350 feet.
On the main channel of the Gravois, the dock including breakwaters, plus a 100-foot buffer, may not extend more than 25 percent of the way to the opposite shore. The dock itself, including breakwaters, is limited to 350 feet. In a channel narrower than 1,000 feet, that buffer can be reduced if no dock exceeds 20 percent of the channel width. Measurements are shore to shore at the dock, perpendicular to the channel.
Those sentences are Appendix B. The size page repeats them next to the walkway and slip limits. A residential walkway is still 6 feet wide on the Gravois. The arm does not get a local exception.
What to send
Pick the nearest town: Sunrise Beach, Laurie, or Gravois Mills. On the form, choose Gravois Arm or “a cove,” and name the cove. If you want a new dock, say how many wells. If the cove is shallow at the back, read the Laurie note on walkways versus dredging before you ask for excavation. Dredging is the last option Ameren wants considered.