2. The following works may not be included in the investment allowance described in subparagraph d of the first paragraph of section 18 of the Act:(a) diamond drilling of drainage holes;
(b) diamond drilling of pilot holes;
(c) diamond drilling of ventilation holes;
(d) diamond drilling for water supply;
(e) diamond drilling of backfill holes; and
(f) diamond drilling of holes used to grout fractured rock.