Is blocking the main OK?

In all three approaches, it looks like the intermodal tracks will be worked using the main.  The train switching the intermodal area will be blocking the main while it works.  This could create a bottleneck in this section if you are planning on having a lot of traffic run down the main.  I think it might be better to re-work your main so that both the intermodal and the yard can be worked from the same lead, thus leaving the main free for through traffic.

Having said that, if I were to pick from your three scenarios, I would probably go with #2 (longer tracks) or #3 (has a more prototypical feel).

Good luck!

I believe they were single ended

 As far as I know, modern intermodal yards are single ended. One thing that I would do is to give the yard a lead, but to have a connection between that lead and the classification yard lead, even if it fouls the main for a second. This will quicken the exchange of cars from one switcher to the other.

A prototype view

Your #3 reminds me of the trackage at the NS intermodal facility in the Delray area of Detroit.  Here's a Bing view.

The main runs along the bottom, and the yard is worked from the lead on the right (east).  Maybe something like this would work for you. 

Does switching occur in intermodal yards?

I know nothing of intermodal operations, except that containers are loaded & unloaded. Does a train typically pull into the crane area, park while it gets loaded/unloaded and then pull out again? Or are the trains disassembled/assembled here? Are intermodal trains typically switched at the main yard rather than the loading/unloading section? I looked at a few prototype yards on Google Maps but don't necessarily see leads from them. Any insight?

CSX Intermodal Facility

Indianapolis, IN
http://www.in.gov/indot/files/chapter_4.pdf

I'm sure it depends on the size of the facility

I'm most familiar with CN's Moterm facility just north of Detroit.  No intermodal unit trains originate or terminate there.  A yard job or local (or sometimes a manifest freight) will show up, do setouts & pickups like a typical industry, then move on to the next customer.  The local then takes the intermodal cut to its home yard, where it is placed in a normal manifest freight's consist, to be transported to even larger facilities elsewhere.  

If you look at the NS Detroit facility I posted above, there is a small industry support yard just to the south of it. This is used by the local to help switch the yard.  The yard lead stretches off to the east - it's the track to the north of the double-track main.   This overhead Bing image shows some switching action underway.

You certainly don't need a dedicated lead for your intermodal facility if you don't want one, but it may help open up traffic options.

I think you need to do some more thinking...

 Hi Craig,

As someone who has just started building a layout that has an intermodal terminal (it's also the starting point), I think you may have to look at your design again.  I am by no means an expert in layout design or have that much experience, but I have done a lot of research into how to incorporate one into a layout.

The one thing that you need is "room" and a lot of it.  I started out with an area the was around 6' in total length, this has now expanded to an area that is 10' in length in area and takes up 2/3 of one section of our upper deck.  The loading/unloading tracks are themselves now 6' in length by two (about the same area I originally aloud for) and the two sidings for storage of awaiting trains & removal of empties are over 10' in length.

You have to remember that a 89' TT is around 12" in length, if you want to run a train with 10 x  89" flats (as I did) you need some serious siding/s or small staging yard for the terminal, otherwise you are going to foul the main, or your yard and things will grind to halt very quickly.

Looking at your plans all three have issues with fouling the main whilst working the terminal, I'm not sure of scale but there is no dedicated lead to the terminal or a staging/holding yard either.  I'm not sure if you have read any publications about yard design but if you haven't I would get John Armstrong's - Track Planning for Realistic Operations as a starter.

One thing I have picked up is that your 2nd & 3rd example could possible work with a little alteration to your design, on both designs if you swap the lead to the main and main to the lead you know have a sizeable lead to switch from for both the yard & terminal.  You could then re-route the main through the centre of the yard and back out into the return blob on the right.  This would also allow you to have a second yard lead from the main to service the south yard tracks, therefore splitting the yard into two halves.

There are quite a few people on here that also may have better/different ideas, Byron Henderson comes to mind as he does layout design for a living.  I'll dig out my plans in the next day or two and post them so that you can see what I have ended up with.

Cheers,

Jason...

Intermodal rail yards.

Jeff Wilson wrote a book on the subject. It dates back to 2002, but I don't think things have cxhanged that much in this topic.

Irv

Jeff Wilson's book not available?

Unfortunately I haven't been able to find Jeff's book available anywhere. If anyone knows a source please let me know. Thanks....Craig

Amazon

http://www.amazon.com/Model-Railroaders-Intermodal-Equipment-Operations/dp/0890243131/ref=sr_1_3?ie=UTF8&s=books&qid=1298314798&sr=8-3

http://www.amazon.com/Model-Railroaders-Guide-Freight-Railroader/dp/0890245762

Some intermodal yards have

Some intermodal yards have stub ends others are run thru. some have a singel track others 2 or more tracks. Its really up to you how much room you want to use up. the Chicago yards seem to have the trailers staged near the tracks and containers stacked not much farther. the yards have intermodal tracks and the normal freight car tracks all in one.  Some larger intermodal only yards that service UPS or shared with other larger LTL trucking outfits will unload a train and the trucks are pretty much grabing the trailers as they come off. a facility that does this has the storage room but the trailers may be part of a fast freight set up and they just drop them next to the train that they were on. what Im getting at is that you can save some layout room by not having a huge intermodal aera. One thing for sure is that I have never seen a intermodal yard tie up a mainline. at most they may have to enter the main to pull a string of cars out and then push into a yard track but never parked on the main. at least not that I have seen or think is common. The other question is what era do you model?  early "Intermodal" 1950-1960s was simply backing a trailer onto a flat car. some times a car at a time and that did not take up alot of room but lots of moving of the empty/loaded flat cars. ...just my .02

Trent