what is your soil type????

what might a local septic guy say ... thats who i called when i had this local issue ...

ken

It is mainly clay soil but was tilled and amended. The tree is growing well but i am just a little worried about where i placed it.

Over time the amendments will disappear and the soil will return to its original condition. You would have been better off just loosening it for planting, and mulching afterward. Katsura forms a tall tree on soils it likes (such as moist clays) and may get into your septic field over time, it being usual for roots to grow well beyond crown spreads.

30-40 feet? Don't worry about. When in VA, my septic field was carved out of a forest w/80'+ trees all along its periphery (certainly closer than 30'). Never a problem -- the house was 35 yrs old.

Thanks everyone for your help!