(3)(a)The plans maintained under clauses (a), (b), (d), (e), (f) and (g) of sub regulation (1) shall also show surface contour lines drawn at vertical intervals not exceeding five metres (or ten metres in the case of a mine where there are no working belowground or in cases of mines situated in hilly terrain, such other larger interval as the Regional Inspector may permit by an order in writing-and subject to such conditions as he may specify) over the whole area lying within 200 metres of any part of the working.
