Under s 62(1)(c) of the Mining Act 1992 (NSW), the word 'substantial' qualifies all items in the statutory list, not merely 'building'. The phrase 'or other valuable work or structure' is not limited by the ejusdem generis principle to items of the same genus as those specifically listed, and 'valuable' bears its ordinary meaning. Fences may constitute 'improvements' under the provision. The Mining Warden has no discretion to determine what constitutes an 'improvement' — the question is one of law.
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