Cox Hollow #2 Dam (a/k/a Twin Valley Lake Dam, Key Seq No 14) in Governor Dodge State Park, Iowa County (lat 43.0252 long -90.0837) is a 630-foot long 55-foot high earthen embankment dam whose primary spillway consists of a large concrete riser tower. The riser tower is approximately 44’ deep and has a main spillway vault with horizontal dimensions of 4’-6” x 13’-6” and a low-flow intake vault with horizontal dimensions of 3’-0” x 4’-6”. There is a 36” diameter reinforced concrete pipe (RCP) leading into the low-flow intake vault from the impoundment and a 4’-6”x4’-6” reinforced concrete box (RCB) leading out of the main spillway vault to the downstream creek; pipes come into and out of the riser tower at the bottom. The intake vault is separated from the main vault by a vertical interior wall of reinforced concrete; the wall is equipped with a 36” square slide gate that is set near the bottom of the structure. The slide gate is operated by a crank set on the vault’s top slab.
