Whether or not the easement is exclusive to the Grantee may be irrelevant for this particualr issue (although it clearly gives rise to it's own fight down the road). You may be mich closer to the answer in noting that the Grantee has not complained about water drainage as a barrier to enjoyment of the easement. If in fact water drainage does present such a barrier, you may have a duty to provide a reasonable remedy to the drainage issue. It seems unlikely that the Grantee has the ability to exercise this level of control over the maintenance of the easement at this point in the process. In any event, you certainly do not want to remain silent while the work is done. If the commencement of the work is imminent, you may need to seek a temporary restraining order and injunction until these issues are resolved.