Section 21A. No person shall require or permit any employee to operate a crane, power shovel or other such types of construction equipment in close proximity to overhead high voltage lines; nor to enter upon any land, building or other premises to engage in construction work, including excavation, demolition, repair or other such work or to erect, install, operate or store in or upon such premises any machinery or construction equipment, including well drilling, pile driving or hoisting equipment, where it is intended to perform such work or operate such equipment in close proximity to overhead high voltage lines unless and until contact with said high voltage lines has been effectively guarded against in the manner hereinafter prescribed. For the purposes of this section and sections twenty-one B to twenty-one G the words ”in close proximity to overhead high voltage lines” shall mean within six feet of such lines.