Hi Troy. Welcome.
No definition for any kind of "Positive Drain" in the (2009) IRC. Below is all you're going to get, and it doesn't even apply if your crawlspace doesn't have any usable, habitable space:
R405.1 Concrete or masonry foundations. Drains shall be
provided around all concrete or masonry foundations that
retain earth and enclose habitable or usable spaces located
below grade. Drainage tiles, gravel or crushed stone drains,
perforated pipe or other approved systems or materials shall be
installed at or below the area to be protected and shall discharge
by gravity or mechanical means into an approved drainage sys-
tem. Gravel or crushed stone drains shall extend at least 1 foot
(305 mm) beyond the outside edge of the footing and 6 inches
(152 mm) above the top of the footing and be covered with an
approved filter membrane material. The top of open joints of
drain tiles shall be protected with strips of building paper, and
the drainage tiles or perforated pipe shall be placed on a minimum
of 2 inches (51 mm) of washed gravel or crushed rock at
least one sieve size larger than the tile joint opening or perforation
and covered with not less than 6 inches (152 mm) of the
same material.
Exception: A drainage system is not required when the
foundation is installed on well-drained ground or
sand-gravel mixture soils according to the Unified Soil
Classification System, Group I Soils, as detailed in Table
R405.1.
You may have local amendments/additions to the code that define the term you're looking for; best bet would be to ask your Building Official.
What's the problem you're trying to solve? Is the building dept. asking you to add something, or fix something, or what?