Wiring Outdoor Receptacles from Existing Indoor Circuit

I obtained a city building permit this morning for extending the 15 amp arc fault circuit from my master bedroom to two outdoor receptacles. I
have been doing a lot of research to make sure I install this to code (including consulting numerours newsgroups, DIY books and sites, and the NEC 2005 book), but I have a few questions I was hoping I could get some input on here. When I asked the city, they refered me to the 2002 NEC code which they have adopted and said I can't go wrong if I follow this. I can't find the 2002 book online, and even if I could it can be confusing for a beginner and I want input from as many sources as possible before starting this project.
My plan is to replace the last outlet in my master bedroom circuit (which is in the wall that faces the backyard) with a GFCI receptacle. Then I will drill a hole through the back of the blue-plastic junction box of this outlet and run a 12 guage UF wg cable through the wall to the outside. I am using 12 guage even though it is a 15 amp circuit because the run is being extended by about 75 feet. As far as I can tell by code it is ok to use a thicker cable than required. I will wire this cable to the load end of the GFCI through a 1/2" gray PCV nipple with bushings through the wall, then a PVC LB connector and PVC conduit on the other side of the wall. I will bury the cable 12" and use 1/2" PVC conduit to protect the cable. The first receptacle will be in a built-in masonry barbecue island (yet to be built). This will be used to power the occasional CD player or light. I will continue the circuit to another location in the yard and wire the final receptacle as a standalone unit to power a small fountain pump.
My questions are:
-Is 1/2 inch conduit big enough or do I need to use 3/4 to be in compliance (there will only be one cable in the conduit)?
-Is it to code to run the PVC conduit through the aggregate concrete footing of the bbq island?
-Part of the underground run will cross existing wiring for low voltage lighting and poly tubing for drip system. The electrical conduit will be at a much greater depth than the low voltage cable and poly tubing, and will cross it perpendicularly. Is there anything in the code that would prohibit this?
Any input or device would be greatly appreciated.
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1/2 inch is acceptable.
By Southwire at:
http://72.14.253.104/search?q che:fyLDe8Gq13wJ:appprod.southwire.com/ProductCatalog/XTEInterfaceServlet%3FcontentKey%3Dprodcatsheet6+nm+No.+12+AWG+cable+dimensions&hl=en&gl=us&ct=clnk&cd=2
CU-NM-B
No. 12 CU 2 conductor w/gnd has dim of .410 x .179 inches
Code requires we use the major dia of .410 be used
Ref: Chapt 9 Note 9
A multiconductor cable of two or more conductors
shall be treated as a single conductor for calculating
percentage conduit fill area. For cables that have elliptical
cross sections, the cross-sectional area calculation
shall be based on using the major diameter of the ellipse
as a circle diameter.
(9) A multiconductor cable of two or more conductors
shall be treated as a single conductor for calculating
percentage conduit fill area. For cables that have elliptical
cross sections, the cross-sectional area calculation
shall be based on using the major diameter of the ellipse
as a circle diameter.
Therefore by Table 1 53 per cent fill is allowed.
Using this in cable raceway fill calculator at:
http://www.electrician2.com/calculators/cable_raceway_fill_calc_.htm
enter .410 as daimeter and 1 as number of cables.
A 1/2 inch PVC Schedule 40 or 80 is allowed.

Yes
No problem.
However, I do not know if you can feed a GFCI receptacle from an Arc Fault circuit. This is a new one for me. I suppose the listing people would have something to say on this. The question is: has anyone tested a GFCI connected to an arc fault? Maybe someone here has something on this.
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