Question
I must lay a septic pipe between two spruce trees which are approximately 60 feet high, 6 feet in circumference, and 25 feet apart. They are quite old and magnificent.In addition, the leach field will be quite close.
  A heavy backhoe has already gone between the trees to dig a test hole. I see a couple of severed and damaged roots.
   Will the laying of the pipe and leach field cause serious or fatal damage to these great trees? If so, I will not go through with these plans and try, with limited options, to put the septic elsewhere.
Thank you in advance.
Tom


Answer
The roots of spruce usually spread about 1 1/2 times the width of the foliage. The roots beyond the foliage are smaller and can survive damage much better than the ones inside the foliage spread. I would at all possible keep the digging out from under the foliage and as far as you can from the tree trunk. Up to 25% of the roots of a tree can be cut without causing too much damage as far as die back of the foliage is concerned. Conifers roots seem to heal much faster than hardwoods due to the resin in the sap.

Spruce is not one of the trees that will invade the septic lines. Of course any plant roots will seek water so there maybe some root invasion but spruce roots are not considered a problem.

Try to keep the tree protected during the installation by maybe roping off the area near the tree so the machinery will not dig OR travel over the roots of the trees. This will protect the remaining root system and the trees should be ok.

It is sometimes hard to envision what the landscape looks like from descriptions. Sp if you are in the U.S. and have time you could call the local office of the State Forestry Agency and ask one of their Forester to come out and take a look. This is a free service in most states.