Mo. Rev. Stat. § 242.750

In the event that the drainage operations conducted by any such drainage district shall not drain any tract of land therein to the depth of mining operations conducted on such tract, necessitating the operation by the owner of such tract or his agents or lessees or sublessees, of pumps additional to the pumps operated by such district, then the pumping tax or taxes levied against such tract shall be credited with the amount actually and necessarily spent in such additional pumping operations by such owners, his agents, lessees, or sublessees.