Where the existing gas pipeline crosses belowF1... a ditch or stream it will be protected by a concrete slab and the pipe will be located at such a depth so as to provide at least 1.1 metres cover from the true cleaned bottom of the ditch or stream to the top of the pipe. All ditches, open drains or watercourses interfered with by the exercise of the specified rights will be maintained in effective condition during works by the undertaker and restored to as good a condition as before the commencement of the works.