Conn. Agencies Regs. § 13b-17-45
The greatest care shall be exercised to protect tree roots from damage, not only when excavating but also on all subsequent operations of construction and backfilling. Power machinery, such as trench diggers and shovels, shall not be allowed to operate within the root areas of trees in State highways except when specifically authorized by the Department. When roots are encountered near the base of a tree, the permittee will be required to tunnel under the root systems as directed by the Inspector. When earth has been removed from around tree roots, the roots shall be protected by wrapping with burlap or by covering with mulch. When excavated materials must be piled around the base of trees, the trunks shall be wrapped with burlap from the ground surface to a height well above that of the materials. No stones, metal products, lumber or other hard substances shall be piled in direct contact with burlap so placed. A section of trench passing within the confines of the crown spread of any tree shall be backfilled with a soil having texture and fertility sufficient to sustain plant life. No rubbish or rock shall be placed in this area at any time. Where trench sheeting or bracing is necessary within the root areas of trees on State highways, it shall be placed so that the root systems sustain the least damage.
Conn. Agencies Regs. § 13b-17-45