Mo. Rev. Stat. § 640.730: Facility to have containment structure.

1. The owner or operator of every facility, with a flush system animal waste wet handling facility that poses a risk as determined by the department to any public drinking water supply or any aquatic life, or lies within a drainage basin and is within three hundred feet of any adjacent landowner, shall have a failsafe containment structure or earthen dam that will contain, in the event of an unauthorized discharge, a minimum volume equal to the maximum capacity of flushing in any twenty-four-hour period from all gravity outfall lines, recycle pump station and* recycle force mains.

2. Construction of such structure or dam, as provided in subsection 1 of this section, shall commence within ninety days of June 25, 1996.