(a) You must obtain a monthly grab sample of phosphate rock directly from the rock being fed to the process line before it enters the mill using one of the following methods.
CFR 40-98.264-2013 history
2013CFR 40-98.264-2013 Protection of environment. Part98:Mandatory greenhouse gas reporting. Subpart Z:Phosphoric acid production. Section98.264:Monitoring and QA/QC requirements.