Pine tree roots broken
Roots of pine trees were broken during excavating for septic system. Trees are over 30 years old and grow in sandy soil. Did the excavating disturb the growth of the trees?
Alpena County Michigan trees and shrubs
The roots of trees are the pathway for water and nutrients to reach the tree. If these pathways have been damaged or completely broken the tree will not be able to take up the nutrients and water it needs to live.
I suggest that you have a professional certified arborist look at the situation to determine exactly what the answer is. Here are two resources for finding a certified arborist in your area.