<PAGE>
 
                                                                    EXHIBIT 4(b)

                                             [CONFORMED COPY]
================================================================================


                       TEXAS UTILITIES ELECTRIC COMPANY

                                      TO

                             THE BANK OF NEW YORK,
                        (FORMERLY IRVING TRUST COMPANY)


                                        TRUSTEE UNDER THE TEXAS UTILITIES
                                        ELECTRIC COMPANY MORTGAGE AND
                                        DEED OF TRUST, DATED AS OF
                                        DECEMBER 1, 1983

                              __________________


                      FIFTY-EIGHTH SUPPLEMENTAL INDENTURE

                       PROVIDING AMONG OTHER THINGS FOR
                             FIRST MORTGAGE BONDS,
                          POLLUTION CONTROL SERIES AH

                             FIRST MORTGAGE BONDS,
                          POLLUTION CONTROL SERIES AI

                                      AND

                             FIRST MORTGAGE BONDS,
                          POLLUTION CONTROL SERIES AJ

                              __________________

                           DATED AS OF JULY 1, 1997



            THIS INSTRUMENT GRANTS A SECURITY INTEREST BY A UTILITY
          THIS INSTRUMENT CONTAINS AFTER-ACQUIRED PROPERTY PROVISIONS
<PAGE>
 
            THIS INSTRUMENT GRANTS A SECURITY INTEREST BY A UTILITY
          THIS INSTRUMENT CONTAINS AFTER-ACQUIRED PROPERTY PROVISIONS

                     FIFTY-EIGHTH  SUPPLEMENTAL  INDENTURE

                       _________________________________


     INDENTURE, dated as of July 1, 1997, between TEXAS UTILITIES ELECTRIC
COMPANY, a corporation of the State of Texas, whose address is Energy Plaza,
1601 Bryan Street, Dallas, Texas 75201 (hereinafter sometimes called the
Company), and THE BANK OF NEW YORK (formerly Irving Trust Company), a
corporation of the State of New York, whose address is 101 Barclay Street, New
York, New York 10286 (hereinafter sometimes called the Trustee), Trustee under
the Mortgage and Deed of Trust, dated as of December 1, 1983 (hereinafter called
the Original Indenture, the Original Indenture and any and all indentures and
instruments supplemental thereto being hereinafter sometimes collectively called
the Mortgage), which Original Indenture was executed and delivered by the
Company to secure the payment of bonds issued or to be issued under and in
accordance with the provisions of the Mortgage, reference to which Mortgage is
made, this Indenture (hereinafter called the Fifty-eighth Supplemental
Indenture) being supplemental thereto;

     WHEREAS, said Original Indenture was recorded or filed as required in the
State of Texas; and

     WHEREAS, the Company executed and delivered to the Trustee the following
supplemental indentures:
<TABLE> 
<CAPTION> 
            DESIGNATION                                    DATED AS OF
            -----------                                    ----------- 
<S>                                                        <C>  
First Supplemental Indenture.............................  April 1, 1984
Second Supplemental Indenture............................  September 1, 1984
Third Supplemental Indenture.............................  April 1, 1985
Fourth Supplemental Indenture............................  August 1, 1985
Fifth Supplemental Indenture.............................  September 1, 1985
Sixth Supplemental Indenture.............................  December 1, 1985
Seventh Supplemental Indenture...........................  March 1, 1986
Eighth Supplemental Indenture............................  May 1, 1986
Ninth Supplemental Indenture.............................  October 1, 1986
Tenth Supplemental Indenture.............................  December 1, 1986
Eleventh Supplemental Indenture..........................  December 1, 1986
Twelfth Supplemental Indenture...........................  February 1, 1987
Thirteenth Supplemental Indenture........................  March 1, 1987
Fourteenth Supplemental Indenture........................  April 1, 1987
Fifteenth Supplemental Indenture.........................  July 1, 1987
Sixteenth Supplemental Indenture.........................  September 1, 1987
Seventeenth Supplemental Indenture.......................  October 1, 1987
Eighteenth Supplemental Indenture........................  March 1, 1988
Nineteenth Supplemental Indenture........................  May 1, 1988
</TABLE> 
<PAGE>
 
                                       2

<TABLE>
<CAPTION> 
            DESIGNATION                                    DATED AS OF 
            -----------                                    ----------- 
<S>                                                        <C>  
Twentieth Supplemental Indenture.........................  September 1, 1988
Twenty-first Supplemental Indenture......................  November 1, 1988
Twenty-second Supplemental Indenture.....................  January 1, 1989
Twenty-third Supplemental Indenture......................  August 1, 1989
Twenty-fourth Supplemental Indenture.....................  November 1, 1989
Twenty-fifth Supplemental Indenture......................  December 1, 1989
Twenty-sixth Supplemental Indenture......................  February 1, 1990
Twenty-seventh Supplemental Indenture....................  September 1, 1990
Twenty-eighth Supplemental Indenture.....................  October 1, 1990
Twenty-ninth Supplemental Indenture......................  October 1, 1990
Thirtieth Supplemental Indenture.........................  March 1, 1991
Thirty-first Supplemental Indenture......................  May 1, 1991
Thirty-second Supplemental Indenture.....................  July 1, 1991
Thirty-third Supplemental Indenture......................  February 1, 1992
Thirty-fourth Supplemental Indenture.....................  April 1, 1992
Thirty-fifth Supplemental Indenture......................  April 1, 1992
Thirty-sixth Supplemental Indenture......................  June 1, 1992
Thirty-seventh Supplemental Indenture....................  June 1, 1992
Thirty-eighth Supplemental Indenture.....................  August 1, 1992
Thirty-ninth Supplemental Indenture......................  October 1, 1992
Fortieth Supplemental Indenture..........................  November 1, 1992
Forty-first Supplemental Indenture.......................  December 1, 1992
Forty-second Supplemental Indenture......................  March 1, 1993
Forty-third Supplemental Indenture.......................  April 1, 1993
Forty-fourth Supplemental Indenture......................  April 1, 1993
Forty-fifth Supplemental Indenture.......................  May 1, 1993
Forty-sixth Supplemental Indenture.......................  July 1, 1993
Forty-seventh Supplemental Indenture.....................  October 1, 1993
Forty-eighth Supplemental Indenture......................  November 1, 1993
Forty-ninth Supplemental Indenture.......................  May 1, 1994
Fiftieth Supplemental Indenture..........................  May 1, 1994
Fifty-first Supplemental Indenture.......................  August 1, 1994
Fifty-second Supplemental Indenture......................  April 1, 1995
Fifty-third Supplemental Indenture.......................  June 1, 1995
Fifty-fourth Supplemental Indenture......................  October 1, 1995
Fifty-fifth Supplemental Indenture.......................  March 1, 1996
Fifty-sixth Supplemental Indenture.......................  September 1, 1996
Fifty-seventh Supplemental Indenture.....................  February 1, 1997
</TABLE> 
which supplemental indentures were or are to be recorded or filed as required in
the State of Texas; and

    WHEREAS, by the Original Indenture, the Company covenanted that it would
execute and deliver such supplemental indenture or indentures and such further
instruments and do such further acts as may be necessary or proper to carry out
more effectually the purposes of the Mortgage and to make subject to the Lien of
the Mortgage any property thereafter acquired and intended to be subject to the
Lien thereof; and
<PAGE>
 
                                       3

    WHEREAS, in addition to the property described in the Original Indenture,
the Company has acquired certain other property, rights and interests in
property; and

    WHEREAS, the Company has heretofore issued as of June 30, 1997, in
accordance with the provisions of the Original Indenture, as heretofore
supplemented, the following series of First Mortgage and Collateral Trust Bonds
and First Mortgage Bonds:
<TABLE>
<CAPTION>
 
                                                     Principal      Principal
                                                       Amount         Amount
                     Series                            Issued      Outstanding
                     ------                       --------------  --------------
<S>                                               <C>             <C>
 
12% Series due March 1, 1985......................$    1,000,000  $       None
13 5/8% Series due April 1, 2014..................   100,000,000          None
13 1/2% Series due September 1, 2014..............   150,000,000          None
12 7/8% Series due April 1, 2015..................   150,000,000          None
12% Series due August 1, 2015.....................   100,000,000          None
12% Series due September 1, 2015..................    75,000,000          None
11 1/8% Series due December 1, 2015...............   150,000,000          None
9 3/8% Series due March 1, 2016...................   200,000,000          None
9 3/4% Series due May 1, 2016.....................   200,000,000          None
7 3/4% Pollution Control Series C.................    70,000,000          None
8 1/4% Pollution Control Series D.................   200,000,000          None
9 1/2% Series due December 1, 2016................   300,000,000          None
9 1/4% Series due February 1, 2017................   250,000,000          None
7 7/8% Pollution Control Series E.................   100,000,000          None
10 1/2% Series due April 1, 2017..................   250,000,000          None
9 1/2% Series due July 1, 1997....................   150,000,000          None
10 1/2% Series due July 1, 2017...................   150,000,000          None
9% Pollution Control Series F.....................    55,000,000    51,525,000
9% Pollution Control Series G.....................    12,000,000    12,000,000
9 7/8% Pollution Control Series H.................   112,000,000    28,765,000
9 1/4% Pollution Control Series I.................   100,000,000    54,005,000
10 3/8% Series due May 1, 1998....................   150,000,000          None
11 3/8% Series due May 1, 2018....................   150,000,000          None
Secured Medium-Term Notes, Series A...............   300,000,000    30,000,000
10.44% Series due November 1, 2008................   150,000,000     3,000,000
8 1/4% Pollution Control Series J.................   100,000,000   100,000,000
9 1/2% Series due August 1, 1999..................   200,000,000   200,000,000
10% Series due August 1, 2019.....................   100,000,000          None
9 7/8% Series due November 1, 2019................   150,000,000          None
Secured Medium-Term Notes, Series B...............   150,000,000   114,200,000
8 1/8% Pollution Control Series K.................    50,000,000    50,000,000
8 1/8% Pollution Control Series L.................    40,000,000    40,000,000
10 5/8% Series due September 1, 2020..............   250,000,000          None
Secured Medium-Term Notes, Series C...............   150,000,000          None
8 1/4% Pollution Control Series                   
  due October 1, 2020.............................    11,000,000    11,000,000
7 7/8% Pollution Control Series                   
  due March 1, 2021...............................   100,000,000   100,000,000
9 3/4% Series due May 1, 2021.....................   300,000,000   280,855,000
0% Pollution Control Series M due June 1, 2021....    86,250,000          None
0% Pollution Control Series N due June 1, 2021....    57,500,000          None
0% Pollution Control Series O due June 1, 2021....    57,500,000          None
</TABLE> 
<PAGE>
 
                                       4

<TABLE> 
<S>                                               <C>             <C> 
0% Pollution Control Series P due June 1, 2021....$  115,000,000  $ 47,029,250
8 1/8% Series due February 1, 2002................   150,000,000   150,000,000
8 7/8% Series due February 1, 2022................   175,000,000   175,000,000
8 1/4% Series due April 1, 2004...................   100,000,000   100,000,000
9% Series due April 1, 2022.......................   100,000,000          None
6 3/4% Pollution Control Series due               
  April 1, 2022...................................    50,000,000    50,000,000
7 1/8% Series due June 1, 1997....................   150,000,000          None
8% Series due June 1, 2002........................   147,000,000   147,000,000
6 5/8% Pollution Control Series due               
  June 1, 2022....................................    33,000,000    33,000,000
6 3/8% Series due August 1, 1997..................   175,000,000   175,000,000
7 3/8% Series due August 1, 2001..................   150,000,000   150,000,000
8 1/2% Series due August 1, 2024..................   175,000,000   163,000,000
6.70% Pollution Control Series due                
  October 1, 2022.................................    16,935,000    16,935,000
6.55% Pollution Control Series due                
  October 1, 2022.................................    40,000,000    40,000,000
7 3/8% Series due November 1, 1999................   100,000,000   100,000,000
8 3/4% Series due November 1, 2023................   200,000,000   195,550,000
6 1/2% Pollution Control Series due               
  December 1, 2027................................    46,660,000    46,660,000
6 3/4% Series due March 1, 2003...................   200,000,000   200,000,000
7 7/8% Series due March 1, 2023...................   300,000,000   300,000,000
6.05% Pollution Control Series due                
  April 1, 2025...................................    90,000,000    90,000,000
6.10% Pollution Control Series due                
  April 1, 2028...................................    50,000,000    50,000,000
5 7/8% Series due April 1, 1998...................   175,000,000   175,000,000
6 3/4% Series due April 1, 2003...................   100,000,000   100,000,000
7 7/8% Series due April 1, 2024...................   225,000,000   225,000,000
0% Pollution Control Series due June 1, 2023......   115,000,000   115,000,000
5 3/4% Series due July 1, 1998....................   150,000,000   150,000,000
6 3/4% Series due July 1, 2005....................   100,000,000   100,000,000
7 5/8% Series due July 1, 2025....................   250,000,000   250,000,000
5 1/2% Series due October 1, 1998.................   125,000,000   125,000,000
6 1/4% Series due October 1, 2004.................   125,000,000   125,000,000
7 3/8% Series due October 1, 2025.................   300,000,000   208,000,000
5 1/2% Pollution Control Series due May 1, 2022...    50,000,000    50,000,000
5.55% Pollution Control Series due May 1, 2022....    75,000,000    75,000,000
5.85% Pollution Control Series due May 1, 2022....    33,465,000    33,465,000
Floating Rate Series due May 1, 1999..............   300,000,000   300,000,000
Pollution Control Series Q due May 1, 2029........    45,045,500    45,045,500
Pollution Control Series R due May 1, 2029........    45,045,500    45,045,500
0% Series due 1994................................ 1,013,831,000          None
Pollution Control Series S due April 1, 2030......    58,270,500    58,270,500
Pollution Control Series T due April 1, 2030......    18,400,000    18,400,000
Pollution Control Series U........................   136,108,250   136,108,250
Pollution Control Series V........................   136,108,250   136,108,250
Pollution Control Series W........................    13,857,500    13,857,500
Pollution Control Series X........................    21,246,250    21,246,250
Secured Medium-Term Notes, Series D...............   201,150,000   201,150,000
Pollution Control Series Y........................    28,819,000    28,819,000
Pollution Control Series Z........................    66,642,500    66,642,500
Pollution Control Series AA.......................    28,750,000    28,750,000
Pollution Control Series AB.......................    28,750,000    28,750,000
Pollution Control Series AC.......................    70,397,250    70,397,250
Pollution Control Series AD.......................    57,500,000    57,500,000
</TABLE> 
<PAGE>
 
                                       5

<TABLE> 
<S>                                               <C>             <C> 
Pollution Control Series AE.......................    57,500,000    57,500,000
Pollution Control Series AF.......................    36,000,750    36,000,750
Pollution Control Series AG.......................    28,801,750    28,801,750
</TABLE>

which bonds are also hereinafter sometimes called bonds of the First through
Ninety-fourth Series, respectively; and

     WHEREAS, Section 2.01 of the Original Indenture provides that the form of
each series of bonds (other than the First Series) issued thereunder and of the
coupons to be attached to coupon bonds of such series shall be established by
Resolution of the Board of Directors of the Company, and that the form of such
series, as established by said Board of Directors, shall specify the descriptive
title of the bonds and various other terms thereof, and may also have such
omissions or modifications or contain such provisions not prohibited by the
provisions of the Mortgage as the Board of Directors may, in its discretion,
cause to be inserted therein expressing or referring to the terms and conditions
upon which such bonds are to  be  issued  and/or  secured  under  the  Mortgage;
and

     WHEREAS, Section 22.04 of the Original Indenture provides, among other
things, that any power, privilege or right expressly or impliedly reserved to or
in any way conferred upon the Company by any provision of the Mortgage, whether
such power, privilege or right is in any way restricted or is unrestricted, may
be in whole or in part waived or surrendered or subjected to any restriction if
at the time unrestricted, or to additional restriction if already restricted,
and the Company may enter into any further covenants, limitations, restrictions
or provisions for the benefit of any one or more series of bonds issued
thereunder, or the Company may cure any ambiguity contained therein, or in any
supplemental indenture, or may establish the terms and provisions of any series
of bonds other than the First Series, by an instrument in writing executed and
acknowledged by the Company in such manner as would be necessary to entitle a
conveyance of real estate to be recorded in all of the states in which any
property at the time subject to the Lien of the Mortgage shall be situated; and

     WHEREAS, the Company now desires to create three new series of bonds and to
add to its covenants and agreements contained in the Mortgage certain other
covenants and agreements to be observed by it and to alter and amend in certain
respects the covenants and provisions contained in the Mortgage; and

     WHEREAS, the execution and delivery by the Company of this Fifty-eighth
Supplemental Indenture, and the terms of the bonds of the Ninety-fifth, Ninety-
sixth and Ninety-seventh Series, hereinafter referred to, have been duly
authorized by the Board of Directors of the Company by appropriate resolutions
of said Board of Directors;

     NOW, THEREFORE, THIS INDENTURE WITNESSETH:  That the Company, in
consideration of the premises and of Ten Dollars to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, and in order to secure the payment of both the principal
of and interest and premium, if any, on the bonds from time to time issued under
the Mortgage, according to their tenor 
<PAGE>
 
                                       6

and effect and the performance of all the provisions of the Mortgage (including
any instruments supplemental thereto and any modification made as in the
Mortgage provided) and of said bonds, hath granted, bargained, sold, released,
conveyed, assigned, transferred, mortgaged, hypothecated, affected, pledged, set
over and confirmed and granted a security interest in and by these presents doth
grant, bargain, sell, release, convey, assign, transfer, mortgage, hypothecate,
affect, pledge, set over and confirm and grant a security interest in (subject,
however, to Excepted Encumbrances as defined in Section 1.06 of the Original
Indenture) unto The Bank of New York, Trustee under the Mortgage, and to its
successor or successors in said trust, and to said Trustee and its successors
and assigns forever, all properties of the Company, real, personal and mixed, of
the kind or nature specifically mentioned in the Original Indenture, as
heretofore supplemented, or of any other kind or nature acquired by the Company
on or after the date of the execution and delivery of the Original Indenture
(except any herein or in the Original Indenture expressly excepted), now owned
or, subject to the provisions of Section 18.03 of the Original Indenture,
hereafter acquired by the Company (by purchase, consolidation, merger, donation,
construction, erection or in any other way) and wheresoever situated, including
(without in anywise limiting or impairing by the enumeration of the same, the
scope and intent of the foregoing or of any general description contained in
this Fifty-eighth Supplemental Indenture) all real estate, lands, easements,
servitudes, licenses, permits, franchises, privileges, rights of way and other
rights in or relating to real estate or the occupancy of the same; all power
sites, flowage rights, water rights, water locations, water appropriations,
ditches, flumes, reservoirs, reservoir sites, canals, raceways, waterways, dams,
dam sites, aqueducts, and all other rights or means for appropriating,
conveying, storing and supplying water; all rights of way and roads; all plants
for the generation of electricity by steam, water and/or other power; all power
houses, gas plants, street lighting systems, standards and other equipment
incidental thereto; all telephone, radio and television systems, air-
conditioning systems and equipment incidental thereto, water wheels, water
works, water systems, steam heat and hot water plants, substations, lines,
service and supply systems, bridges, culverts, tracks, ice or refrigeration
plants and equipment, offices, buildings and other structures and the equipment
thereof; all machinery, engines, boilers, dynamos, turbines, electric, gas and
other machines, prime movers, regulators, meters, transformers, generators
(including, but not limited to, engine driven generators and turbo-generator
units), motors, electrical, gas and mechanical appliances, conduits, cables,
water, steam heat, gas or other pipes, gas mains and pipes, service pipes,
fittings, valves and connections, pole and transmission lines, towers, overhead
conductors and devices, underground conduits, underground conductors and
devices, wires, cables, tools, implements, apparatus, storage battery equipment,
and all other fixtures and personalty; all municipal and other franchises,
consents or permits; all lines for the transmission and distribution of electric
current, gas, steam heat or water for any purpose including towers, poles,
wires, cables, pipes, conduits, ducts and all apparatus for use in connection
therewith and (except as herein or in the Original Indenture expressly excepted)
all the right, title and interest of the Company in and to all other property of
any kind or nature appertaining to and/or used and/or occupied and/or enjoyed in
connection with any property hereinbefore or in the Original Indenture
described.
<PAGE>
 
                                       7

     TOGETHER WITH all and singular the tenements, hereditaments, prescriptions,
servitudes and appurtenances belonging or in anywise appertaining to the
aforesaid property or any part thereof, with the reversion and reversions,
remainder and remainders and (subject to the provisions of Section 13.01 of the
Original Indenture) the tolls, rents, revenues, issues, earnings, income,
product and profits thereof, and all the estate, right, title and interest and
claim whatsoever, at law as well as in equity, which the Company now has or may
hereafter acquire in and to the aforesaid property and franchises and every part
and parcel thereof.

     IT IS HEREBY AGREED by the Company that, subject to the provisions of
Section 18.03 of the Original Indenture, all the property, rights and franchises
acquired by the Company (by purchase, consolidation, merger, donation,
construction, erection or in any other way) after the date hereof, except any
herein or in the Original Indenture expressly excepted, shall be and are as
fully granted and conveyed hereby and as fully embraced within the Lien of the
Original Indenture and the Lien hereof as if such property, rights and
franchises were now owned by the Company and were specifically described herein
and conveyed hereby.

     PROVIDED that the following are not and are not intended to be now or
hereafter granted, bargained, sold, released, conveyed, assigned, transferred,
mortgaged, hypothecated, affected, pledged, set over or confirmed hereunder, nor
is a security interest therein hereby or by the Original Indenture, as
heretofore supplemented, granted or intended to be granted, and the same are
hereby expressly excepted from the Lien and operation of the Original Indenture,
as heretofore supplemented, and from the Lien and operation of this Fifty-eighth
Supplemental Indenture, viz.: (1) cash, shares of stock, bonds, notes and other
obligations and other securities not hereinbefore or hereafter specifically
pledged, paid, deposited, delivered or held under the Mortgage or covenanted so
to be; (2) merchandise, equipment, apparatus, materials or supplies held for the
purpose of sale or other disposition in the usual course of business or for the
purpose of repairing or replacing (in whole or in part) any rolling stock,
buses, motor coaches, automobiles or other vehicles or aircraft or boats, ships,
or other vessels and any fuel, oil and similar materials and supplies consumable
in the operation of any of the properties of the Company; rolling stock, buses,
motor coaches, automobiles and other vehicles and all aircraft; boats, ships and
other vessels; all timber, minerals, mineral rights and royalties; (3) bills,
notes and other instruments and accounts receivable, judgments, demands, general
intangibles and choses in action, and all contracts, leases and operating
agreements not specifically pledged hereunder or under the Mortgage or
covenanted so to be; (4) the last day of the term of any lease or leasehold
which may hereafter become subject to the Lien of the Mortgage; (5) electric
energy, gas, water, steam, ice, and other materials or products generated,
manufactured, produced, or purchased by the Company for sale, distribution or
use in the ordinary course of its business; (6) any natural gas wells or natural
gas leases or natural gas transportation lines or other works or property used
primarily and principally in the production of natural gas or its
transportation, primarily for the purpose of sale to natural gas customers or to
a natural gas distribution or pipeline company, up to the point of connection
with any distribution system; and (7) the Company's franchise to be a
corporation; provided, however, that the property and rights
<PAGE>
 
                                       8

expressly excepted from the Lien and operation of the Original Indenture and
this Fifty-eighth Supplemental Indenture in the above subdivisions (2) and (3)
shall (to the extent permitted by law) cease to be so excepted in the event and
as of the date that the Trustee or a receiver or trustee shall enter upon and
take possession of the Mortgaged and Pledged Property in the manner provided in
Article XV of the Original Indenture by reason of the occurrence of a Default.

     TO HAVE AND TO HOLD all such properties, real, personal and mixed, granted,
bargained, sold, released, conveyed, assigned, transferred, mortgaged,
hypothecated, affected, pledged, set over or confirmed or in which a security
interest has been granted by the Company as aforesaid, or intended so to be
(subject, however, to Excepted Encumbrances as defined in Section 1.06 of the
Original Indenture), unto The Bank of New York, Trustee, and its successors and
assigns forever.

     IN TRUST NEVERTHELESS, for the same purposes and upon the same terms,
trusts and conditions and subject to and with the same provisos and covenants as
are set forth in the Original Indenture, as heretofore supplemented, this Fifty-
eighth Supplemental Indenture being supplemental to the Original Indenture.

     AND IT IS HEREBY COVENANTED by the Company that all the terms, conditions,
provisos, covenants and provisions contained in the Original Indenture, as
heretofore supplemented, shall affect and apply to the property hereinbefore
described and conveyed and to the estate, rights, obligations and duties of the
Company and the Trustee and the beneficiaries of the trust with respect to said
property, and to the Trustee and its successors as Trustee of said property, in
the same manner and with the same effect as if said property had been owned by
the Company at the time of the execution of the Original Indenture, and had been
specifically and at length described in and conveyed to said Trustee by the
Original Indenture as a part of the property therein stated to be conveyed.

     The Company further covenants and agrees to and with the Trustee and its
successors in said trust under the Mortgage, as follows:


                                   ARTICLE I

                          NINETY-FIFTH SERIES OF BONDS

     SECTION 1.  There shall be a series of bonds designated "Pollution Control
Series AH" (herein sometimes referred to as the "Ninety-fifth Series"), each of
which shall also bear the descriptive title "First Mortgage Bond", and the form
thereof, which shall be established in accordance with a Resolution of the Board
of Directors of the Company, shall contain suitable provisions with respect to
the matters hereinafter in this Section specified.  Bonds of the Ninety-fifth
Series may be issued in one or more tranches and may be issued with up to one
month's accrued interest.  Bonds of the Ninety-fifth Series shall be issued as
fully registered bonds in denominations of One Hundred Dollars and, at the
option of the Company, in any multiple or multiples thereof (the exercise of
such option 
<PAGE>
 
                                       9

to be evidenced by the execution and delivery thereof); Bonds of the
Ninety-fifth Series shall mature on such date not later than the maturity date
of the Series 1997D Brazos Revenue Bonds, referred to below, shall bear interest
at such rate or rates, payable on such date or dates, and have such other terms
and provisions not inconsistent with the Original Indenture as the proper
officer or officers of the Company may determine in accordance with one or more
Resolutions filed with the Trustee referring to this Fifty-eighth Supplemental
Indenture (such determinations shall be evidenced by or in accordance with one
or more written orders filed with the Trustee for the authentication and
delivery of bonds of the Ninety-fifth Series and shall constitute determinations
of the Board of Directors with respect to such bonds for purposes of the
Mortgage), the principal of each said bond to be payable at the office or agency
of the Company in the Borough of Manhattan, The City of New York, New York, or
at the office or agency of the Company in the City of Dallas, Texas, as the
holder of any said bond may elect, in such coin or currency of the United States
of America as at the time of payment is legal tender for public and private
debts.  Bonds of the Ninety-fifth Series shall be dated as in Section 2.03 of
the Original Indenture provided.

     (I)  The bonds of the Ninety-fifth Series shall be initially issued in an
aggregate principal amount not to exceed $33,079,750 to, and registered in the
name of, the trustee under the Trust Indenture, dated as of July 1, 1997
(hereinafter sometimes called the "1997D Brazos Bond Indenture"), of the Brazos
River Authority (hereinafter sometimes called the "Brazos Authority"), under
which its Collateralized Pollution Control Revenue Refunding Bonds (Texas
Utilities Electric Company Project) Series 1997D (hereinafter sometimes called
the "Series 1997D Brazos Revenue Bonds") are to be issued, in order to provide
the benefit of a lien to secure the obligation of the Company to make the
Installment Payments and Purchase Price payments pursuant to, and as such terms
are defined in, the Series 1997D Installment Sale and Bond Amortization
Agreement, dated as of July 1, 1997 (hereinafter sometimes called the "1997D
Brazos Agreement"), between the Brazos Authority and the Company.  The maximum
amount of bonds of the Ninety-fifth Series that may be issued is unlimited but
the aggregate principal amount of bonds of the Ninety-fifth Series at any one
time Outstanding shall not exceed $33,079,750.  The maximum stated interest rate
for any bonds of the Ninety-fifth Series shall not exceed 15% per annum.

     The Company shall receive a credit against its obligation to make any
payment of the principal of and interest, if any, on any tranche of the bonds of
the Ninety-fifth Series, whether at maturity, upon redemption or otherwise, in
an amount equal to (x) the sum of (a) the amount, if any, on deposit in the Debt
Service Fund maintained under the 1997D Brazos Bond Indenture which reduces the
corresponding Installment Payment and (b) the amount, if any, paid by the
Company pursuant to Section 5.04 of the 1997D Brazos Agreement in respect of the
corresponding Installment Payment multiplied by (y) the ratio of the principal
amount of Outstanding bonds of the Ninety-fifth Series to the principal amount
of outstanding Series 1997D Brazos Revenue Bonds.

     The Trustee may conclusively presume that the obligation of the Company to
pay the principal of, and interest, if any, on any tranche of the bonds of the
Ninety-fifth Series 
<PAGE>
 
                                       10

as the same shall become due and payable shall have been fully satisfied and
discharged unless and until it shall have received a written notice from the
trustee under the 1997D Brazos Bond Indenture, signed by the President, a Vice
President or a Trust Officer of such trustee, stating that the corresponding
Installment Payment or Purchase Price payment has become due and payable and has
not been fully paid and specifying the amount of funds required to make such
payment.

     (II)  In the event that any Series 1997D Brazos Revenue Bonds outstanding
under the 1997D Brazos Bond Indenture shall become immediately due and payable
pursuant to Section 6.02 of the 1997D Brazos Bond Indenture, upon the occurrence
of an Event of Default under Section 6.01(a) of the 1997D Brazos Bond Indenture,
all bonds of the Ninety-fifth Series, then Outstanding, shall be redeemed by the
Company, on the date such Series 1997D Brazos Revenue Bonds shall have become
immediately due and payable, at the principal amount thereof.

     The Trustee may conclusively presume that no redemption of bonds of the
Ninety-fifth Series is required pursuant to the first paragraph of this
subsection (II) unless and until it shall have received a written notice from
the trustee under the 1997D Brazos Bond Indenture, signed by the President, a
Vice President or a Trust Officer of such trustee, stating that Series 1997D
Brazos Revenue Bonds have become immediately due and payable pursuant to Section
6.02 of the 1997D Brazos Bond Indenture, upon the occurrence of an Event of
Default under Section 6.01(a) of the 1997D Brazos Bond Indenture and specifying
the principal amount thereof.  Said notice shall also contain a waiver of notice
of such redemption by the trustee under the 1997D Brazos Bond Indenture, as the
holder of all bonds of the Ninety-fifth Series then Outstanding.

     (III)  The Company hereby waives its right to have any notice of redemption
pursuant to subsection (II) of this Section 1 state that such notice is subject
to the receipt of the redemption moneys by the Trustee on or before the date
fixed for redemption. Notwithstanding the provisions of Section 12.02 of the
Mortgage, any such notice under such subsection shall not be conditional.

     (IV)  At the option of the registered owner, any bonds of the Ninety-fifth
Series, upon surrender thereof for cancellation at the office or agency of the
Company in the Borough of Manhattan, The City of New York, New York, shall be
exchangeable for a like aggregate principal amount of bonds of the same series
of other authorized denominations.

     Bonds of the Ninety-fifth Series shall not be transferrable except to any
successor trustee under the 1997D Brazos Bond Indenture, any such transfer to be
made at the office or agency of the Company in the Borough of Manhattan, The
City of New York, New York.

     The Company hereby waives any right to make a charge for any exchange or
transfer of bonds of the Ninety-fifth Series.
<PAGE>
 
                                       11

                                   ARTICLE II

                          NINETY-SIXTH SERIES OF BONDS

     SECTION 2.  There shall be a series of bonds designated "Pollution Control
Series AI" (herein sometimes referred to as the "Ninety-sixth Series"), each of
which shall also bear the descriptive title "First Mortgage Bond", and the form
thereof, which shall be established in accordance with a Resolution of the Board
of Directors of the Company, shall contain suitable provisions with respect to
the matters hereinafter in this Section specified.  Bonds of the Ninety-sixth
Series may be issued in one or more tranches and may be issued with up to one
month's accrued interest.  Bonds of the Ninety-sixth Series shall be issued as
fully registered bonds in denominations of One Hundred Dollars and, at the
option of the Company, in any multiple or multiples thereof (the exercise of
such option to be evidenced by the execution and delivery thereof); Bonds of the
Ninety-sixth Series shall mature on such date not later than the maturity date
of the Series 1997A Sabine Revenue Bonds, referred to below, shall bear interest
at such rate or rates, payable on such date or dates, and have such other terms
and provisions not inconsistent with the Original Indenture as the proper
officer or officers of the Company may determine in accordance with one or more
Resolutions filed with the Trustee referring to this Fifty-eighth Supplemental
Indenture (such determinations shall be evidenced by or in accordance with one
or more written orders filed with the Trustee for the authentication and
delivery of bonds of the Ninety-sixth Series and shall constitute determinations
of the Board of Directors with respect to such bonds for purposes of the
Mortgage), the principal of each said bond to be payable at the office or agency
of the Company in the Borough of Manhattan, The City of New York, New York, or
at the office or agency of the Company in the City of Dallas, Texas, as the
holder of any said bond may elect, in such coin or currency of the United States
of America as at the time of payment is legal tender for public and private
debts.  Bonds of the Ninety-sixth Series shall be dated as in Section 2.03 of
the Original Indenture provided.

     (I)  The bonds of the Ninety-sixth Series shall be initially issued in an
aggregate principal amount not to exceed $59,253,750 to, and registered in the
name of, the trustee under the Trust Indenture, dated as of July 1, 1997
(hereinafter sometimes called the "1997A Sabine Bond Indenture"), of the Sabine
River Authority of Texas (hereinafter sometimes called the "Sabine Authority"),
under which its Collateralized Pollution Control Revenue Refunding Bonds (Texas
Utilities Electric Company Project) Series 1997A (hereinafter sometimes called
the "Series 1997A Sabine Revenue Bonds") are to be issued, in order to provide
the benefit of a lien to secure the obligation of the Company to make the
Installment Payments and Purchase Price payments pursuant to, and as such terms
are defined in, the Series 1997A Installment Sale and Bond Amortization
Agreement, dated as of July 1, 1997 (hereinafter sometimes called the "1997A
Sabine Agreement"), between the Sabine Authority and the Company.  The maximum
amount of bonds of the Ninety-sixth Series that may be issued is unlimited but
the aggregate principal amount of bonds of the Ninety-sixth Series at any one
time Outstanding shall not exceed $59,253,750.  The 
<PAGE>
 
                                       12

maximum stated interest rate for any bonds of the Ninety-sixth Series shall not
exceed 15% per annum.

     The Company shall receive a credit against its obligation to make any
payment of the principal of and interest, if any, on any tranche of the bonds of
the Ninety-sixth Series, whether at maturity, upon redemption or otherwise, in
an amount equal to (x) the sum of (a) the amount, if any, on deposit in the Debt
Service Fund maintained under the 1997A Sabine Bond Indenture which reduces the
corresponding Installment Payment and (b) the amount, if any, paid by the
Company pursuant to Section 5.04 of the 1997A Sabine Agreement in respect of the
corresponding Installment Payment multiplied by (y) the ratio of the principal
amount of Outstanding bonds of the Ninety-sixth Series to the principal amount
of outstanding Series 1997A Sabine Revenue Bonds.

     The Trustee may conclusively presume that the obligation of the Company to
pay the principal of, and interest, if any, on any tranche of the bonds of the
Ninety-sixth Series as the same shall become due and payable shall have been
fully satisfied and discharged unless and until it shall have received a written
notice from the trustee under the 1997A Sabine Bond Indenture, signed by the
President, a Vice President or a Trust Officer of such trustee, stating that the
corresponding Installment Payment or Purchase Price payment has become due and
payable and has not been fully paid and specifying the amount of funds required
to make such payment.

     (II)  In the event that any Series 1997A Sabine Revenue Bonds outstanding
under the 1997A Sabine Bond Indenture shall become immediately due and payable
pursuant to Section 6.02 of the 1997A Sabine Bond Indenture, upon the occurrence
of an Event of Default under Section 6.01(a) of the 1997A Sabine Bond Indenture,
all bonds of the Ninety-sixth Series, then Outstanding, shall be redeemed by the
Company, on the date such Series 1997A Sabine Revenue Bonds shall have become
immediately due and payable, at the principal amount thereof.

     The Trustee may conclusively presume that no redemption of bonds of the
Ninety-sixth Series is required pursuant to the first paragraph of this
subsection (II) unless and until it shall have received a written notice from
the trustee under the 1997A Sabine Bond Indenture, signed by the President, a
Vice President or a Trust Officer of such trustee, stating that Series 1997A
Sabine Revenue Bonds have become immediately due and payable pursuant to Section
6.02 of the 1997A Sabine Bond Indenture, upon the occurrence of an Event of
Default under Section 6.01(a) of the 1997A Sabine Bond Indenture and specifying
the principal amount thereof.  Said notice shall also contain a waiver of notice
of such redemption by the trustee under the 1997A Sabine Bond Indenture, as the
holder of all bonds of the Ninety-sixth Series then Outstanding.

     (III)  The Company hereby waives its right to have any notice of redemption
pursuant to subsection (II) of this Section 2 state that such notice is subject
to the receipt of the redemption moneys by the Trustee on or before the date
fixed for redemption. Notwithstanding the provisions of Section 12.02 of the
Mortgage, any such notice under such subsection shall not be conditional.
<PAGE>
 
                                       13

     (IV)  At the option of the registered owner, any bonds of the Ninety-sixth
Series, upon surrender thereof for cancellation at the office or agency of the
Company in the Borough of Manhattan, The City of New York, New York, shall be
exchangeable for a like aggregate principal amount of bonds of the same series
of other authorized denominations.

     Bonds of the Ninety-sixth Series shall not be transferrable except to any
successor trustee under the 1997A Sabine Bond Indenture, any such transfer to be
made at the office or agency of the Company in the Borough of Manhattan, The
City of New York, New York.

     The Company hereby waives any right to make a charge for any exchange or
transfer of bonds of the Ninety-sixth Series.



                                  ARTICLE III

                         NINETY-SEVENTH SERIES OF BONDS

     SECTION 3.  There shall be a series of bonds designated "Pollution Control
Series AJ" (herein sometimes referred to as the "Ninety-seventh Series"), each
of which shall also bear the descriptive title "First Mortgage Bond", and the
form thereof, which shall be established in accordance with a Resolution of the
Board of Directors of the Company, shall contain suitable provisions with
respect to the matters hereinafter in this Section specified.  Bonds of the
Ninety-seventh Series may be issued in one or more tranches and may be issued
with up to one month's accrued interest.  Bonds of the Ninety-seventh Series
shall be issued as fully registered bonds in denominations of One Hundred
Dollars and, at the option of the Company, in any multiple or multiples thereof
(the exercise of such option to be evidenced by the execution and delivery
thereof); Bonds of the Ninety-seventh Series shall mature on such date not later
than the maturity date of the Series 1997A Trinity Revenue Bonds, referred to
below, shall bear interest at such rate or rates, payable on such date or dates,
and have such other terms and provisions not inconsistent with the Original
Indenture as the proper officer or officers of the Company may determine in
accordance with one or more Resolutions filed with the Trustee referring to this
Fifty-eighth Supplemental Indenture (such determinations shall be evidenced by
or in accordance with one or more written orders filed with the Trustee for the
authentication and delivery of bonds of the Ninety-seventh Series and shall
constitute determinations of the Board of Directors with respect to such bonds
for purposes of the Mortgage), the principal of each said bond to be payable at
the office or agency of the Company in the Borough of Manhattan, The City of New
York, New York, or at the office or agency of the Company in the City of Dallas,
Texas, as the holder of any said bond may elect, in such coin or currency of the
United States of America as at the time of payment is legal tender for public
and private debts.  Bonds of the Ninety-seventh Series shall be dated as in
Section 2.03 of the Original Indenture provided.
<PAGE>
 
                                       14

     (I)  The bonds of the Ninety-seventh Series shall be initially issued in an
aggregate principal amount not to exceed $13,800,000 to, and registered in the
name of, the trustee under the Trust Indenture, dated as of July 1, 1997
(hereinafter sometimes called the "1997A Trinity Bond Indenture"), of the
Trinity River Authority of Texas (hereinafter sometimes called the "Trinity
Authority"), under which its Collateralized Pollution Control Revenue Refunding
Bonds (Texas Utilities Electric Company Project) Series 1997A (hereinafter
sometimes called the "Series 1997A Trinity Revenue Bonds") are to be issued, in
order to provide the benefit of a lien to secure the obligation of the Company
to make the Installment Payments and Purchase Price payments pursuant to, and as
such terms are defined in, the Series 1997A Installment Sale and Bond
Amortization Agreement, dated as of July 1, 1997 (hereinafter sometimes called
the "1997A Trinity Agreement"), between the Trinity  Authority and the Company.
The maximum amount of bonds of the Ninety-seventh Series that may be issued is
unlimited but the aggregate principal amount of bonds of the Ninety-seventh
Series at any one time Outstanding shall not exceed $13,800,000. The maximum
stated interest rate for any bonds of the Ninety-seventh Series shall not exceed
15% per annum.

     The Company shall receive a credit against its obligation to make any
payment of the principal of and interest, if any, on any tranche of the bonds of
the Ninety-seventh Series, whether at maturity, upon redemption or otherwise, in
an amount equal to (x) the sum of (a) the amount, if any, on deposit in the Debt
Service Fund maintained under the 1997A Trinity Bond Indenture which reduces the
corresponding Installment Payment and (b) the amount, if any, paid by the
Company pursuant to Section 5.04 of the 1997A Trinity Agreement in respect of
the corresponding Installment Payment multiplied by (y) the ratio of the
principal amount of Outstanding bonds of the Ninety-seventh Series to the
principal amount of outstanding Series 1997A Trinity Revenue Bonds.

     The Trustee may conclusively presume that the obligation of the Company to
pay the principal of, and interest, if any, on any tranche of the bonds of the
Ninety-seventh Series as the same shall become due and payable shall have been
fully satisfied and discharged unless and until it shall have received a written
notice from the trustee under the 1997A Trinity Bond Indenture, signed by the
President, a Vice President or a Trust Officer of such trustee, stating that the
corresponding Installment Payment or Purchase Price payment has become due and
payable and has not been fully paid and specifying the amount of funds required
to make such payment.

     (II)  In the event that any Series 1997A Trinity Revenue Bonds outstanding
under the 1997A Trinity Bond Indenture shall become immediately due and payable
pursuant to Section 6.02 of the 1997A Trinity Bond Indenture, upon the
occurrence of an Event of Default under Section 6.01(a) of the 1997A Trinity
Bond Indenture, all bonds of the Ninety-seventh Series, then Outstanding, shall
be redeemed by the Company, on the date such Series 1997A Trinity Revenue Bonds
shall have become immediately due and payable, at the principal amount thereof.

     The Trustee may conclusively presume that no redemption of bonds of the
Ninety-seventh Series is required pursuant to the first paragraph of this
subsection (II) unless and 
<PAGE>
 
                                       15

until it shall have received a written notice from the trustee under the 1997A
Trinity Bond Indenture, signed by the President, a Vice President or a Trust
Officer of such trustee, stating that Series 1997A Trinity Revenue Bonds have
become immediately due and payable pursuant to Section 6.02 of the 1997A Trinity
Bond Indenture, upon the occurrence of an Event of Default under Section 6.01(a)
of the 1997A Trinity Bond Indenture and specifying the principal amount thereof.
Said notice shall also contain a waiver of notice of such redemption by the
trustee under the 1997A Trinity Bond Indenture, as the holder of all bonds of
the Ninety-seventh Series then Outstanding.

     (III)  The Company hereby waives its right to have any notice of redemption
pursuant to subsection (II) of this Section 3 state that such notice is subject
to the receipt of the redemption moneys by the Trustee on or before the date
fixed for redemption. Notwithstanding the provisions of Section 12.02 of the
Mortgage, any such notice under such subsection shall not be conditional.

     (IV)  At the option of the registered owner, any bonds of the Ninety-
seventh Series, upon surrender thereof for cancellation at the office or agency
of the Company in the Borough of Manhattan, The City of New York, New York,
shall be exchangeable for a like aggregate principal amount of bonds of the same
series of other authorized denominations.

     Bonds of the Ninety-seventh Series shall not be transferrable except to any
successor trustee under the 1997A Trinity Bond Indenture, any such transfer to
be made at the office or agency of the Company in the Borough of Manhattan, The
City of New York, New York.

     The Company hereby waives any right to make a charge for any exchange or
transfer of bonds of the Ninety-seventh Series.



                                   ARTICLE IV

                            MISCELLANEOUS PROVISIONS

     SECTION 4.  Subject to the amendments provided for in this Fifty-eighth
Supplemental Indenture, the terms defined in the Original Indenture, as
heretofore supplemented, shall for all purposes of this Fifty-eighth
Supplemental Indenture have the meanings specified in the Original Indenture, as
heretofore supplemented.

     SECTION 5.  The Trustee hereby accepts the trusts herein declared,
provided, created or supplemented and agrees to perform the same upon the terms
and conditions herein and in the Original Indenture, as heretofore supplemented,
set forth and upon the following terms and conditions:
<PAGE>
 
                                       16

     The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Fifty-eighth Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made by the Company solely.  In general, each and every term and
condition contained in Article XIX of the Original Indenture shall apply to and
form part of this Fifty-eighth Supplemental Indenture with the same force and
effect as if the same were herein set forth in full with such omissions,
variations and insertions, if any, as may be appropriate to make the same
conform to the provisions of this Fifty-eighth Supplemental Indenture.

     SECTION 6.  Whenever in this Fifty-eighth Supplemental Indenture either of
the parties hereto is named or referred to, this shall, subject to the
provisions of Articles XVIII and XIX of the Original Indenture, be deemed to
include the successors and assigns of such party, and all the covenants and
agreements in this Fifty-eighth Supplemental Indenture contained, by or on
behalf of the Company, or by or on behalf of the Trustee, shall, subject as
aforesaid, bind and inure to the respective benefits of the respective
successors and assigns of such parties, whether so expressed or not.

     SECTION 7.  Nothing in this Fifty-eighth Supplemental Indenture expressed
or implied, is intended, or shall be construed to confer upon, or to give to,
any person, firm or corporation, other than the parties hereto and the holders
of the bonds and coupons Outstanding under the Mortgage, any right, remedy or
claim under or by reason of this Fifty-eighth Supplemental Indenture or any
covenant, condition, stipulation, promise or agreement hereof, and all the
covenants, conditions, stipulations, promises and agreements in this Fifty-
eighth Supplemental Indenture contained, by or on behalf of the Company, shall
be for the sole and exclusive benefit of the parties hereto, and of the holders
of the bonds and coupons Outstanding under the Mortgage.

     SECTION 8.  This Fifty-eighth Supplemental Indenture shall be executed in
several counterparts, each of which shall be an original and all of which shall
constitute but one and the same instrument.
<PAGE>
 
                                       17

     IN WITNESS WHEREOF, TEXAS UTILITIES ELECTRIC COMPANY has caused its
corporate name to be hereunto affixed, and this instrument to be signed and
sealed by its Chairman of the Board and Chief Executive, President or one of its
Vice Presidents, and its corporate seal to be attested by its Secretary or one
of its Assistant Secretaries for and in its behalf, and THE BANK OF NEW YORK has
caused its corporate name to be hereunto affixed, and this instrument to be
signed and sealed by one of its Vice Presidents or Assistant Vice Presidents and
its corporate seal to be attested by one of its Assistant Vice Presidents,
Assistant Secretaries or Assistant Treasurers, all as of the day and year first
above written.

                                                TEXAS UTILITIES ELECTRIC COMPANY


                                                By       /s/ RON SEIDEL
                                                  ------------------------------
                                                           RON SEIDEL
                                                         Vice President


Attest:

       /s/ GLEN H. HIBBS
---------------------------------
        GLEN H. HIBBS
     Assistant Secretary



Executed, sealed and delivered by
  TEXAS UTILITIES ELECTRIC COMPANY
  in the presence of:


      /s/ W. E. PATTERSON
----------------------------------


     /s/ JUSTUS B. RHODES
---------------------------------
<PAGE>
 
                                       18


                                       THE BANK OF NEW YORK,
                                         Trustee

                                       By     /s/ W. N. GITLIN            
                                       -----------------------------         
                                                W. N. GITLIN     
                                               Vice President


Attest:

    /s/ STEPHEN J. GIURLANDO
----------------------------------
      STEPHEN J. GIURLANDO
    Assistant Vice President


Executed, sealed and delivered by
  THE BANK OF NEW YORK
  in the presence of:


      /s/ JASON B. GREGORY
-----------------------------------


       /s/ ESSIE ELCOCK
---------------------------------------
<PAGE>
 
                                       19

STATE OF TEXAS   )
                 )  SS.:
COUNTY OF DALLAS )


     Before me, a Notary Public in and for said State, on this day personally
appeared RON SEIDEL, known to me to be the person whose name is subscribed to
the foregoing instrument and known to me to be a Vice President of TEXAS
UTILITIES ELECTRIC COMPANY, a Texas corporation, and acknowledged to me that
said person executed said instrument for the purposes and consideration therein
expressed, and as the act of said corporation.

     Given under my hand and seal of office this 23rd day of June, 1997.
                                                 ----                   



                                              /s/ LENAE B. DAVIS
                                    -------------------------------------
                                                LENAE B. DAVIS
                                        Notary Public, State of Texas
                                     My Commission Expires June 23, 2000
<PAGE>
 
                                       20


STATE OF NEW YORK  )
                   )  SS.:
COUNTY OF NEW YORK )


     Before me, a Notary Public in and for said State, on this day personally
appeared W.N. GITLIN, known to me to be the person whose name is subscribed to
the foregoing instrument and known to me to be a Vice President of THE BANK OF
NEW YORK, a New York corporation, and acknowledged to me that said person
executed said instrument for the purposes and consideration therein expressed,
and as the act of said corporation.

     Given under my hand and seal of office this 18th day of June, 1997.
                                                 ----                   



                                                  /s/ WILLIAM J. CASSELS
                                            ------------------------------------
                                                    WILLIAM J. CASSELS
                                              Notary Public, State of New York
                                                      No. 01CA5027729
                                                    Qualified in Bronx
                                            Certificate filed in New York County
                                              Commission Expires May 16, 1998
<PAGE>
 
                                       21

                           SUMMARY OF RECORDING DATA

                      Fifty-eighth Supplemental Indenture
                               Filed July 8, 1997
                 Office of the Secretary of the State of Texas,
                 Utility Security Instrument File No. 83-281286