Question
Hi. I live in CA.,zone 7, foothills of the Sierra's. I need to shade the western exposure of my home (it reaches over 100 degrees during the summer) but the septic tank is located about 55 feet from that side of the house and when I dug my hole for a tree I was right on top of the main septic inlet line to the tank. A real bummer. I called our local county environmental dept. and he did give me some good news. He said that becuz my system is fairly new, the materials and the way it was sealed made it vertually invasion proof by tree roots. He said he's seen roots wrap around the line but never actually get inside. I would like to find a shade tree that would grow in this area around 40-50' tall but maybe not so wide so the roots won't have to extend so far. The rooms on the 2nd story are very hot during the summer so if I could find something to shade them as well as part of the roof I think it might help bring down AC costs which are phenomenal in the summer ($775 for 1 month last year). Is this asking too much? The "environmental" guy suggested a fruitless Mulberry but I read they have alot of pollen and my kids suffer from allergies so I had been looking at a London Planetree or Hackberry "Northern". I need help. Oh and did I mention that it would need to be fast growing so we can get cool relatively soon? I guess there's no such thing as a large, fast growing tree with noninvasive roots, right? That would be too much to ask. Suggestions would be sooo appreciated. Thank you.  

Answer
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FOLLOW-UP - You can also buy bigger trees to start with - 4" caliper size and bigger.  Pricy, but then so is $775/month!
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No matter what the "environmental" guy says, I still wouldn't plant a tree right on top of a pipe - roots not only penetrate pipes, they crush them.  A little root becomes a big root in no time.  Off to the side by 5 feet will save you a monser head-ache in the future.

And, yes, there are fast-growing, large trees for your area - some better than others.  Here are a few:

Dawn Redwood - this is a cool one, because it is a shady pine, but it drops its needles in the fall, for passive solar GAIN, for the chilly winter when you want sunshine (gets up to 70 ft.)
Zelkova - to 50'
Tulip Tree - fast to 60' - Thomas Jefferson's favorite
Kentucky Coffee Tree - to 50'
Sweetgum - to 45'
Beech - to 50'
Hackberry - to 40' - deep roots - good call.
London Plane - It's o.k.; Big leaves, messy seed pods, can get anthacnose (a spore-borne disease: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7420.html ).

Yes - I'd avoid Mulberry, too. Also avoid Birch, because even though it is fast, its roots are shallow, and they don't live very long.

I'd suggest heavy shades on the windows, too.  A tree can only do so much for a second floor exposure. (just kidding - it's actually the ROOF that need shade)  

Hope it helps ~Marc