IDOT has this question regarding a horticulturally valuable tree - a hybrid between pecan and bitternut hickory - that has been used as a cutting source for pecan improvement programs. It occurs along IL Route 30 in NW Illinois. Route 30 will be widened. IDOT wants to know if a distance of twice the drip line from the trunk - measured at 19 ft (i.e., 38 ft) - is a safe enough distance from the trunk to avoid serious root damage from ditch work that would adjoin road widening.

Greetings John:

Although approximately 40' of delineated "safe" zone has been proposed for this tree, my biggest fear is altered hydrology and excessive road salt. Symptoms from such construction projects, as I'm sure you well know, may lay dormant for several years and then manifest themselves 3-8 years later after everything is said and done with the project.

Obviously, I cannot say with absolute certainty that such a safe zone is adequate for this tree as I haven't seen the site or the tree location.

My suggestion is simply to have IDOT request technical assistance from the local IDNR district forester for an on-site assessment and evaluation. In fact, this sort of interagency cooperation is quite common and customary.

Best of luck!