Work crews are completing the installation of a compacted stone dust surface on the Danvers Rail Trail. The new material is being applied over the existing gravel. Large trucks are depositing the stone dust along the trail, and heavy equipment is being used to compact it. The work, which began July 15, is expected to be done by the end of this coming week. The project is being paid for with $50,000 in Federal Highway Administration funds that Danvers and Wenham were jointly awarded by the state last December. Part of the money paid for installing stone dust on a portion of Wenham’s rail trail — the section adjacent to the new SwampWalk that was built over a marsh area in Danvers and Wenham. That work was recently completed.