<PAGE>

                                                                    EXHIBIT 31.B

                                 CERTIFICATION

I, Greg G. Gruber, certify that:

     1. I have reviewed this quarterly report on Form 10-Q of ANR Pipeline
Company;

     2. Based on my knowledge, this quarterly report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this quarterly
report;

     3. Based on my knowledge, the financial statements, and other financial
information included in this quarterly report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in this quarterly report;

     4. The registrant's other certifying officer(s) and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

          (a) Designed such disclosure controls and procedures, or caused such
     disclosure controls and procedures to be designed under our supervision, to
     ensure that material information relating to the registrant, including its
     consolidated subsidiaries, is made known to us by others within those
     entities, particularly during the period in which this report is being
     prepared;

          (b) Evaluated the effectiveness of the registrant's disclosure
     controls and procedures and presented in this report our conclusions about
     the effectiveness of the disclosure controls and procedures, as of the end
     of the period covered by this report based on such evaluation; and

          (c) Disclosed in this report any change in the registrant's internal
     control over financial reporting that occurred during the registrant's most
     recent fiscal quarter (the registrant's fourth fiscal quarter in the case
     of an annual report) that has materially affected, or is reasonably likely
     to materially affect, the registrant's internal control over financial
     reporting; and

     5. The registrant's other certifying officer(s) and I have disclosed, based
on our most recent evaluation of internal control over financing reporting, to
the registrant's auditors and the audit committee of registrant's board of
directors (or persons performing the equivalent functions):

          (a) All significant deficiencies and material weaknesses in the design
     or operation of internal control over financial reporting which are
     reasonably likely to adversely affect the registrant's ability to record,
     process, summarize and report financial information; and

          (b) Any fraud, whether or not material, that involves management or
     other employees who have a significant role in the registrant's internal
     control over financial reporting.


                                                  /s/ Greg G. Gruber
                                          --------------------------------------
                                                      Greg G. Gruber
                                                  Senior Vice President,
                                                 Chief Financial Officer,
                                                  Treasurer and Director
                                                 (Principal Financial and
                                                     Accounting Officer)
                                                    ANR Pipeline Company

Date: August 13, 2004