Salt Lake County commissioners have named a new member to the county Planning Commission, replacing a retiring member who by ordinance cannot be reappointed.

Effective immediately, Barbara Slaymaker will assume the Planning Commission seat formerly held by Chandler St. John. Her term will run through Feb. 20, 1991.St. John has served for six years on the Planning Commission. County ordinance limits members of county volunteer boards to two three-year terms on any one board.

Planning Commission members are volunteers who serve without pay.