PS: 6 inches of alpaca manure and 6-12 inch deep paths between rows
is not an absolute requirement, that is simply a best case. If you do
not have that much manure, then you can make the piles shallower
or narrower. If your soil takes a backhoe or a stick of dynamite to
dig a hole in, maybe you can only manage 3 inch deep paths between
rows.
That is still the way to go, though. A 3-inch deep path beside a 3-inch
high pile of alpaca (or horse, or rabbit) manure makes a 6 inch high
row. That gives the water some place to drain off from the rows into.
You want the rows oriented so that the furrows between them run
downhill, even if the grade is minimal, rather than across the grade,
Here is a method for testing manure, compost, etc for contaminants:
http://whatcom.wsu.edu/ag/aminopyralid/bioassay.html
(The alpacas are probably pastured in spring, summer, and fall,
and the pasture may be herbicide-free, but the owner may need
to supplement with commercial hay in mid-winter, thus raising
the risk of undigested herbicides in their manure. Cheap enough
and fast enough test to be sure before using it.)