Mo. Rev. Stat. § 293.390: Standards for roof control — supply of materials required (coal mines).

1. The operator of every coal mine shall compile or have compiled a set of minimum standards for systematic roof control suitable to the roof conditions and mining system of his mine. After written approval by the director, the minimum standards shall be placed in effect and complied with by employees and officials, and additional supports shall be installed wherever it is necessary to afford adequate protection.

2. At all coal mines, the operator shall provide an ample supply of timber and cap pieces or wedge of proper size, roof-bolting materials, or other proper devices with which to secure all places in a safe manner.