The grantors do further grant unto the state of _________, to the use of the state highway administration of the department of transportation, its successors and assigns, the perpetual right to erect and maintain between October 1st and April 1st of each year, snow fences within 100 feet of the land hereby granted in fee simple, provided that said snow fences shall not interfere with the construction and use of buildings now erected or hereafter erected or with growing crops.