Such slopes shall be suitably planted with perennial grasses or other ground cover plantings in accordance with the plans approved by the Planning Board. In areas where excavations or embankments would extend significantly beyond road rights-of-way, thereby causing disruption to the natural environment of the development, the Planning Board may, upon the application of the developer, consider or may, upon its own initiative, direct the use of terraces, retaining walls, crib walls or other means of maintaining roadway slopes. In any event, the entire roadway right-of-way shall be fully graded, and any retaining walls, crib walls or terraces shall be located outside of the roadway right-of-way, and their maintenance shall be the responsibility of the owner of the property on which they are constructed. The developer shall make suitable provisions in the instruments transferring title to any property containing such terraces, retaining walls or crib walls and shall provide a copy thereof to the Planning Board and the Township Clerk. All graded areas within or outside of the roadway right-of-way shall be neatly graded, topsoiled, fertilized and seeded to establish a stand of perennial grasses.