The planning council shall be primarily concerned with the planning and development of a region which is initially defined generally as follows: That portion of Township 27 North, Snohomish County, Washington, lying west of the line formed by the east boundaries of Sections 6, 7, 18, 19, 30 and 31, of Range 5 East, W.M. (Added by § 2 of Agreement adopted Jan. 31, 1966).