I was only verifying what ctacker stated about sequence Line closest to the arrow is first operation, not bottom up, as can clearly be seen from the picture. The rest of the question will have to be left up to someone else.

Hi Lar!
I really hate to correct you (Heck! I may just be the one who is incorrect if the current version of A3.0 has a different abbreviation ;) ) but, I know that you would do the same for me so, here goes...

"Then likely CAAC gouged to clean metal" The abbreviation should be "CAC-A" instead according to AWS A3.0:2001 (is this the current version?), on page 2... In my next reply, I'll refer to A2.4-98 (I don't have the current version) in attempting to explain the order or sequence of operation with respect to the multiple reference line welding symbol shown in the picture posted by "irnwlkr"... I would do it in this post but then I would lose everything I typed so far so, please bear with me ;)

Wait a second!!! I just remembered about the multiple tabbing option in Mozilla Firefox which is very helpful in this situation...

A couple of observations I need to point out in order to avoid confusion from what the original poster is asking clarification for, and the picture provided by "irnwlkr" which according to my observation, is much different than what "Inspectkta" is describing... This is what is described in the original post:

My weld symbol has 2 lines:  the first line is a double bevel cjp with backgouging,  the second is a 5/16 fillet all the way around with metal core wire 100% C02.

Application is for a modular expansion dam... Is this "modular expansion dam" a bridge component? Also, is it somewhat vaguely described in the following .pdf file from pages 2 through 7? If this is indeed the situation, then you need to clarify your second question below with the EOR because from what I read in the .pdf file, with respect to the testing of the installed modular expansion device... In order to pass the test, no leakage is allowed plus a few other discontinuities that may be interpreted as a manufacturing defect as described in pages 6 &7.

http://fhwapap04.fhwa.dot.gov/nhswp/agency/Colorado/Standard%20Specifications%20and%20Supplements/E%20-%20Structures/518.pdf

Is this .pdf file a better representation of what you mean by a "modular expansion dam?"

http://esvc000298.bne102u.server-web.com/Documents/TrelleborgModExpansion.pdf

Here's some more examples of bridge repair projects in the great state of Washington:

http://www.wsdot.wa.gov/eesc/bridge/preservation/pdf/2007_09-statewide-SPECIAL.pdf

This is more on a national level:

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_319.pdf
For the purpose of comparison, the symbol that "Inspectkta" describes has only two lines as opposed to three lines in the picture provided by "irnwlkr" so, that's the first comparable difference...

The second difference is what is described in the initial post: "the first line is a double bevel cjp" so, I would envision a tee joint with a bevel required on both sides of of the vertical or horizontal member plate (If that is - the member is a plate and not some other structural shape???) which would then be positioned either perpendicular to the surface of the other member or, at a "skewed?" angle which could be the case of this scenario since "Inspectkta" did mention in the second question: "how can one weld a fillet weld all the way around if 2 sides are not at right angles, due to the weld size being limited to the shortest length of substrate?" This is why a picture or drawing speaks volumes, and prevents confusion from attempting to interpret a situation or scenario with only limited data in which requires much more details than originally offered in order to assist in giving "comprehensive" answers to your questions :(

So "Inspectkta", if you would be so kind in offering more specific details such as in a drawing, or sketch of the detail(s) & dimensions, the corresponding welding symbol(s), and any other information that would help us understand your scenario better, I'm sure that we could help answer your questions concisely and without any misinterpretations or misrepresentation. ;)

Now that I got that out of the way, let's attempt to understand better what you mean by using the term "substrate." The reason I'm asking for clarification here is because as far as I understand it, the term is used to describe "any material to which a thermal spray deposit is applied" according to AWS publication A3.0:2001 "Standard Welding Terms and Definitions" on page 38.

Of course, the term may or may not be used in a different context for AWS D1.1 of what year? I've got the 2002 edition so let's see if there's a reference to the term "substrate..." Well as far as these old & tired eyes are concerned, I couldn't find anything referring to the term "substrate" in my 2002 edition of AWS D1.1 ,and the use of the term "substrate" in the context of what you're attempting to describe is in the very least confusing!!! Unless you really are describing what the actual term substrate is defined as according to AWS A3.0:2001.

Also when you referred to the two sides: fillet weld all the way around if 2 sides are not at right angles... Can you be more specific??? Do you mean the 2 sides of the beveled member or, are you describing the 2 ends of the joint where one would "wrap" or, continue depositing the fillet weld around from one side to the other side of the member? Does one end of the joint prohibit the 'wrapping around" or, continuous deposit of the fillet weld to the opposite or other side of the beveled member?

Q:  Does the all around symbol on the top line for the fillet weld transfer down to the double bevel weld, if there is no all the way around symbol on that weld line?

Q: D1.1 says that the CJP weld should only be as long as the thinnest substrate piece, how can one weld a fillet weld all the way around if 2 sides are not at right angles, due to the weld size being limited to the shortest length of substrate?

Now getting back to comparing the two welding symbols in which only one is actually shown in a picture, and the other described in text form..."irnwlkr" picture (.jpg) shows a bent or broken arrow which means one member - specifically the one the arrowhead of the leader line is pointing towards, is the member to be prepared...

However the difference is that the .jpg has a single bevel weld symbol on the arrow side of the reference line only as opposed to what "Inspectkta" is describing as a double bevel - meaning both sides of the one member that makes up the "T" joint is beveled... So right there it's obvious that the .jpg is not the same welding symbol, and the intent of "irnwlkr" was to show via .jpg how the sequence or order of operation works with a multiple reference line welding symbol.

Finally, here's what one will find when one refers to ANSI/AWS A2.4-98 version of "Standard Symbols for Welding, Brazing, and Nondestructive Examination:

On page 25, 4.7 "Back and Backing welds"
4.7.1 General. the back and backing weld symbols are identical. The sequence of welding determines which designation applies. The back weld is made after the groove weld, and the backing weld is made before the groove weld (see 4.7.2 and 4.7.3).

4.7.2 Back Weld Symbol. The back weld symbol is placed on the side of the reference line opposite a groove weld symbol (Remember the difference between the term: "Welding Symbol" & "Weld Symbol"). When a single reference line is used, "Back Weld" shall be specified in the tail of the welding symbol. Alternately, if multiple reference lines are used, the back weld symbol shall be placed on a reference line subsequent to the reference line specifying the groove weld [see Figure 27 (A) located on page 25].

4.7.3 Backing Weld Symbol. The backing weld symbol is placed on the side of the reference line opposite a grrove weld symbol. When a single reference line is used, "backing weld" shall be specified in the tail of the welding symbol. Alternately, if multiple reference lines are used, the backing weld symbol shall be placed on a reference line prior to the reference line specifying the groove weld [see Figures 27 (B) and (C) located on page 26].

Oh and btw, "awspartb"? A less confusing way to describe the sequence of operation for a multiple reference line welding symbol would be to mention that the first sequence of operation is determined by the reference line closest to the apex of the leader & 1st reference line with the next operation being determined by the reference line further away from the 1st reference line and if there are more than 2 reference lines in the welding symbol, the next reference line after the second one & further still - away from the apex of the leader & 1st reference line of the welding symbol would be the next or final operation sequence that is - unless there is another reference line still further away in distance from the apex of the leader & 1st reference line of the welding symbol... "Bottom, Middle, and Top" can easily be misinterpreted as you already found out. ;)

I await your response from the questions I posted "Inspectkta!!!"  

Respectfully,
Henry