<PAGE>

                                                                   EXHIBIT 99-23

                   TENTH AMENDMENT TO TRUST AGREEMENT BETWEEN
                      FIDELITY MANAGEMENT TRUST COMPANY AND
                           THE DETROIT EDISON COMPANY

      THIS TENTH AMENDMENT, dated as of the first day of May, 2000, by and
between Fidelity Management Trust Company (the "Trustee") and The Detroit Edison
Company (the "Sponsor"):

                                   WITNESSETH:

      WHEREAS, the Trustee and the Sponsor heretofore entered into a Trust
Agreement dated June 30, 1994, as amended with regard to The Detroit Edison
Savings & Investment Plan. The Detroit Edison Savings & Investment Plan for
Employees Represented by Local 17 of the International Brotherhood of Electrical
Workers, and The Detroit Edison Savings & Investment Plan for Employees
Represented by Local 223 of the Utility Workers Union of America (collectively
and individually, the "Plan"); and

      WHEREAS, the Trustee and the Sponsor now desire to amend said Trust
Agreement as provided for in Section 14 thereof:

      NOW THEREFORE, in consideration of the above premises the Trustee and the
Sponsor hereby amend the Trust Agreement by:

      (1)   Amending the "Processing" Section of Schedule "A" to add the
            following:

                  -     Roll-In Processing. The Trustee shall process the
                        qualification of rollover contributions to the Trust.
                        The procedures for qualifying a rollover are directed by
                        the Sponsor and the Trustee shall accept or deny each
                        rollover based upon the Plan's written criteria and any
                        written guidelines presided by the Administrator and
                        documented in the Plan Administrative Manual, or, if
                        none, as set forth below:

                        To process a rollover request the participant must
                        obtain the signature from the distributing plan, trustee
                        or custodian, on the designated form, certifying that
                        the monies distributed originally came from a qualified
                        plan and have not been commingled with any non-eligible
                        money. If a signature cannot be obtained a signed letter
                        from the distributing plan, trustee or custodian on its
                        Company letterhead will also be acceptable.

                        Requests that do not meet the specified criteria will be
                        returned to the participant with further an explanation
                        as to why the request cannot be processed. If the
                        Sponsor or the Trustee determine that a request is not a
                        valid rollover, the full amount of the requested
                        rollover will be distributed to the participant.

      IN WITNESS WHEREOF, the Trustee and the Sponsor have caused this Eighth
Amendment to be executed by their duly authorized officers effective as of the
day and year first above written.

<PAGE>

THE DETROIT EDISON COMPANY                   FIDELITY MANAGEMENT TRUST
                                             COMPANY

By: /s/ Darrell K. Ferrell  04-25-2000       By: /s/ Carolyn Redden   05-03-2000
    ----------------------  ----------           ------------------   ----------
    Darrell K. Ferrell      Date                 Carolyn Redden       Date
                                                 Vice President

                                       2