O'Neill Dam and Forebay
are joint Federal-State facilities located on San Luis Creek 2.5 miles downstream from San Luis Dam. O'Neill Forebay Dam is a feature of the Central Valley Project - San Joaquin Division - San Luis Unit
. The reservoir has a surface area of 2,250 acres and 14 miles of shoreline. The Park includes boating, camping, picnic facilities, fishing, hiking, and serves as a major family destination for many in the west central valley. Currently an expansion of the Maderos boat ramp facilities is underway, which will improve boat access and day use facilities.