Can't find anything for WF... D1.1 does address "5.23.6 Variation in Web Flatness
5.23.6.1 Measurements. Variations from flatness of
girder webs shall be determined by measuring the offset
from the actual web centerline to a straight edge whose
length is greater than the least panel dimension and placed
on a plane parallel to the nominal web plane. Measurements
shall be taken prior to erection (see Commentary).
5.23.6.2 Statically Loaded Nontubular Structures.
Variations from flatness of webs having a depth,
D, and a thickness, t, in panels bounded by stiffeners or
flanges, or both, whose least panel dimension is d shall
not exceed the following:
Intermediate stiffeners on both sides of web
where D/t < 150, maximum variation = d/100
where D/t ≥ 150, maximum variation = d/80
Intermediate stiffeners on one side only of web
where D/t < 100, maximum variation = d/100
where D/t ≥ 100, maximum variation = d/67
No intermediate stiffeners
where D/t ≥ 100, maximum variation = D/150
(See Annex D for tabulation.)".

But I believe this refers to built-up beams

hi John,
give you an old general contractor, developers trick
have the local building inspector reject it
they love to be jerks
hope this gives you some ideas
sincerely,
Kent

Hey Stranger, you need to come around more often.  You are greatly missed.

I don't believe you will find anything 'specific' to your query.  As Duke mentioned, most fabricators I have worked with have been very co-operative about using D1.1 Clause 5.23 (which I don't think is specific to 'built up' members Duke, just any 'welded' structural members).  Most of the time these calculations will put you with a variation in flatness of between 1/4" to 1/2".  Anything over 1/4" and I start measuring and calculating to see if it is good or needs corrective action or replacement. 

The bottom line will truly be in D1.1 Clause 5.23.12.

But, notice this in D1.1 C-5.23.6.2  "NOTE: The AISC Specification for Design, Fabrication, and Erection of Structural Steel for Buildings states that the tolerances for flatness of girder webs given in 5.23.6.2 need not apply for statically loaded girders." (emphasis in bold mine for attention).

So, is it really that critical? 

Especially if it is a static girder, I would say you have no worry or fear of the quality of this item.  I would still document it in my report.  If it is not static I would run the calculations to base my decision on and leave it to the engineers who would get a streamlined instant copy of my report. 

Just my two tin pennies worth.

He Is In Control, Have a Great Day,  Brent