The grantee of your ROW has the right to render your easement effective for the purpose contemplated not just by repair but also by development and improvement, but there is no duty or obligation of any sort upon him to do anything at all at any time. Your right is essentially a simple right to pass and repass strictly in accordance with the wording of your grant, and if you can only now only do this in wellies and a tracked vehicle - tough ! You yourself have no right whatsoever to do anything to the surface and underground, and you can be prevented from doing anything should you attempt it. Further, should you do something which subsequently results in injury to the person or property of a third party then you can be sued to the hilt but cannot insure against this risk. However, if the ROW is your primary access and the grantee is awkward then you have a very good chance of obtaining a Court Order allowing you to restore the surface at least to its original condition at your cost. If it is your secondary access the chances of an Order are still there but somewhat less.