The title to that portion of the right-of-way acquired by the City of Los Angeles, and furnished to the State of California, for Route 187, but not needed for that route upon its construction, is hereby relinquished to the city. However, before any relinquishment occurs, the department shall concur that such portion is not needed for state highway purposes, and the portion being relinquished shall be precisely described and recorded with the County Recorder of Los Angeles County.