EXHIBIT 21 - ----------- SEMCO ENERGY, INC. List of Subsidiaries Exhibit 21 to Form 10-K (2001) As of December 31, 2001, the subsidiaries of SEMCO Energy, Inc. (the Registrant) were: - -- Alaska Pipeline Company, an Alaska corporation - -- NORSTAR Pipeline Company, Inc., an Alaska corporation (a subsidiary of Alaska Pipeline Company) - -- Aretech Information Services, Inc., a Michigan corporation - -- Hotflame Gas, Inc., a Michigan corporation - -- NATCOMM, Inc., a Michigan corporation - -- Flint Construction Company, a Georgia corporation (a subsidiary of NATCOMM, Inc.) - -- Iowa Pipeline Associates, Inc., a Michigan corporation (a subsidiary of NATCOMM, Inc.) - -- K & B Construction, Inc., a Kansas corporation (a subsidiary of Iowa Pipeline Associates, Inc.) - -- KLP Construction Co., Inc., an Illinois corporation (a subsidiary of Iowa Pipeline Associates, Inc.) - -- Long's Underground Technologies, Inc., a Michigan corporation (a subsidiary of NATCOMM, Inc.) - -- NATCOMM Engineering, Inc., a Michigan corporation (a subsidiary of NATCOMM, Inc.) - -- Maverick Pipeline Services, Inc., a Michigan corporation (a subsidiary of NATCOMM Engineering, Inc.) - -- Oilfield Materials Consultants, Inc., a Michigan corporation (a subsidiary of NATCOMM Engineering, Inc.) - -- Sub-Surface Construction Co., a Michigan corporation (a subsidiary of NATCOMM, Inc.) - -- SEMCO Energy Ventures, Inc., a Michigan corporation - -- SEMCO Arkansas Pipeline Company, a Michigan corporation (a subsidiary of SEMCO Energy Ventures, Inc.) - -- SEMCO Gas Storage Company, a Michigan corporation (a subsidiary of SEMCO Energy Ventures, Inc.) - -- SEMCO Pipeline Company, a Michigan corporation (a subsidiary of SEMCO Energy Ventures, Inc.) - -- Southeastern Development Company, a Michigan corporation (a subsidiary of SEMCO Energy Ventures, Inc.) - -- Southeastern Financial Services, Inc., a Michigan corporation (a subsidiary of SEMCO Energy Ventures, Inc.) Each of the above-listed companies does business only under its respective corporate name as indicated above, except as follows: - -- SEMCO Energy, Inc. does business in Alaska under the name ENSTAR Natural Gas Company and in Michigan as SEMCO Energy Gas Company. - -- Aretech Information Services, Inc. does business in Michigan under the name Arenet.net and Arenet. - -- Oilfield Materials Consultants, Inc. does business in Texas under the name Michigan Oilfield Materials Consultants, Inc. - -- Sub-Surface Construction Co. does business in Ohio under the name Sub Surface Gas Services and Main Construction Co.