| http://www.w3.org/ns/prov#value | - (v) the choke section, except for pipes and cableways meeting the requirements of subparagraphs (e)(iii) and (e)(iv) of this paragraph, is filled with stemming material having a bulk density no less than 60 percent of the average density of the surrounding rock, and has a product of density and thickness no less than 250 grams per square centimeter;
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