Sentence:  The Secretary of the Interior shall submit a report of his findings , together with recommendations for an effective safety program for metal and nonmetallic <WSD>mines</WSD> ( excluding coal and lignite mines ) based upon such findings , to the Congress not more than two years after the date of enactment of this Act . 
Meaning of the word marked with <WSD> tags:  excavation in the earth from which ores and minerals are extracted