I decided that I could get some ground "infiltration" with this method with one of my two garage downspouts (instead of just shooting it into the alley):

How To Recess Downspouts In About Four Minutes - YouTube
http://www.youtube.com/watch?v=rLnE14wCt1o&feature=related

Took me a lot longer than four minutes they claimed in the video, but here is what I did:

Trenched and laid pipe (painted and attached elbow and cover first)- then, adjusted drain level and buried (see images of what I did below).

First section of 4" pipe is solid; second 10 feet is perforated:
4 in. x 10 ft. HDPE Corrugated Perforated Drain Pipe-4040010 at The Home Depot

Question.
I've been exploring above ground gutter extensions to run water into my yard from my house gutters, but having tried this technique, I think I want to try it with a couple of house downspouts.

I'm really focusing on getting water away from the foundation because it has suffered quite a bit of damage in the past (don't want to go with splash blocks).

What unintended/unforeseen negative consequences might there be?

Would the 4" perforated plastic pipe (small slit openings, not the larger round holes found in the white drain pipes) fill with grass roots to the point it becomes useless as a drain. Wouldn't the large diameter - 4"pipe - be able to keep of with root infiltration? The first 10 foot section of pipe would be solid and then transition to perforated.

Winter time (in Denver; buried maybe 4" deep) freezing up?

I guess I could dig large capacity drain holes and place plastic drain boxes, but I think that's kind of extreme - especially if the above plan will work just about as well.

Thoughts?

thanks

The downspout should be directed into a 3" or 4" PVC or ABS wye fitting above grade. This provides a cleanout point should you ever need it.

At the end of the run, you use a "popup". It stays closed until there's water flow, then closes when the water stops flowing. This deters critters from taking residence in your drains.

The corrugated pipes you're using should be those that have a sleeve around them to resist plant roots attracted to the water.

To help with drainage, I rest the pipes on a bed of free-flowing gravel. No fines.

I installed hard and corrugated downspout drainage all round for our last home that we had six years. This is a cold climate and there were no problems. I did notice that some of the unsleeved corrugated lines we dug up for a pool were infiltrated by shrubbery roots. I've use similar drainage at corners of a couple of homes I've built since, also with no problems reported. I often see new homes where the builders dump the downspouts onto driveways, which turn into sheets of deadly ice in the winter. Underground drainage is a cheap safe alternative.

The only odd side effect I noticed was that the grass around the drainage lines was much lusher and healthier than the rest of our lawn. (But, then, I'm not much of a gardener.)

Encouraging to hear that freezing should not be a problem.

"...unsleeved corrugated lines we dug up for a pool were infiltrated by shrubbery roots."

Yes, when I do my house I will use a "sock" designed to keep the fines, and hopefully roots, out of the perforated pipe.