Although the city manager, in his capacity as concurrency manager, has basic oversight responsibility for the concurrency management system, the immediate authority for making a concurrency evaluation and finding and the issuance of a concurrency compliance certification shall rest with the building official; however, his determinations on these matters shall be reviewed by the concurrency manager. City officials may obtain assistance, opinions and recommendations from qualified professional engineers and planners in reviewing and evaluating projects for concurrency purposes. The planning and zoning board shall follow its usual review procedures for development proposals, except that any final approvals shall be contingent upon the issuance of a concurrency compliance certification by the building official.