<PAGE>

                                                                     Exhibit 4.3



                            DOMINION RESOURCES, INC.
                                     Issuer

                                       TO

                            THE CHASE MANHATTAN BANK
                                    Trustee

                                -----------------

                          Third Supplemental Indenture

                            Dated as of July 1, 2000

                                -----------------

                                  $400,000,000

                       2000 Series C 7.600% Senior Notes,

                               due July 15, 2003
<PAGE>

                               TABLE OF CONTENTS/1/




                                   ARTICLE I
                       2000 SERIES C 7.600% SENIOR NOTES
<TABLE>
<CAPTION>

<S>                  <C>                                                  <C>
     SECTION 101.    Establishment.......................................  2
     SECTION 102.    Definitions.........................................  2
     SECTION 103.    Payment of Principal and Interest...................  2
     SECTION 104.    Denominations.......................................  2
     SECTION 105.    Global Securities...................................  2
     SECTION 106.    Redemption..........................................  2
     SECTION 107.    Sinking Fund........................................  2
     SECTION 108.    Additional Interest.................................  2
     SECTION 109.    Paying Agent........................................  2
     SECTION 110.    Limitation on Liens.................................  2


                                   ARTICLE II
                            MISCELLANEOUS PROVISIONS


     SECTION 201.    Recitals by Company.................................  2
     SECTION 202.    Ratification and Incorporation of Original Indenture  2
     SECTION 203.    Executed in Counterparts............................  2
     SECTION 204.    Assignment..........................................  2

</TABLE>


________________________
     /1/ This Table of Contents does not constitute part of the Indenture or
have any bearing upon the interpretation of any of its terms and provisions.
<PAGE>

     THIS THIRD SUPPLEMENTAL INDENTURE is made as of the first day of July,
2000, by and between DOMINION RESOURCES, INC., a Virginia corporation, having
its principal office at 120 Tredegar Street, Richmond, Virginia 23219 (the
"Company"), and THE CHASE MANHATTAN BANK, a New York banking corporation, as
Trustee (herein called the "Trustee").

                              W I T N E S S E T H:

     WHEREAS, the Company has heretofore entered into a Senior Indenture, dated
as of June 1, 2000 (the "Original Indenture") and a First Supplemental Indenture
dated as of June 1, 2000 (the "First Supplemental Indenture"), with the Trustee;

     WHEREAS, the Original Indenture is incorporated herein by this reference
and the Original Indenture, as supplemented by the First Supplemental Indenture,
a Second Supplemental Indenture dated as of the date hereof, and this Third
Supplemental Indenture, is herein called the "Indenture";

     WHEREAS, under the Original Indenture, a new series of Securities may at
any time be established in accordance with the provisions of the Original
Indenture and the terms of such series may be described by a supplemental
indenture executed by the Company and the Trustee;

     WHEREAS, the Company proposes to create under the Indenture a series of
Securities;

     WHEREAS, additional Securities of other series hereafter established,
except as may be limited in the Original Indenture as at the time supplemented
and modified, may be issued from time to time pursuant to the Indenture as at
the time supplemented and modified; and

     WHEREAS, all conditions necessary to authorize the execution and delivery
of this Third Supplemental Indenture and to make it a valid and binding
obligation of the Company have been done or performed.

     NOW, THEREFORE, in consideration of the agreements and obligations set
forth herein and for other good and valuable consideration, the sufficiency of
which is hereby acknowledged, the parties hereto hereby agree as follows:

                                   ARTICLE I

                       2000 SERIES C 7.600% SENIOR NOTES

SECTION 101.      Establishment. There is hereby established a new series of
                  -------------
Securities to be issued under the Indenture, to be designated as the Company's
2000 Series C 7.600% Senior Notes, due July 15, 2003 (the "Series C Senior
Notes").

     There are to be initially authenticated and delivered $400,000,000
principal amount of Series C Senior Notes.  Additional Series C Senior Notes
without limitation as to amount, and without the consent of the Holders of the
then Outstanding Series C Senior Notes, may also be authenticated and delivered
in the manner provided in Section 303 of the Original Indenture.
<PAGE>

Any such additional Series C Senior Notes will have the same interest rate,
maturity and other terms as those initially issued. Further Series C Senior
Notes may be also authenticated and delivered as provided by Sections 304, 305,
306, 905 or 1107 of the Original Indenture.

     The Series C Senior Notes shall be issued in definitive fully registered
form without coupons, in substantially the form set out in Exhibit A hereto.
                                                           ---------
The entire initially issued principal amount of the Series C Senior Notes shall
initially be evidenced by one or more certificates issued to Cede & Co., as
nominee for The Depository Trust Company.

     The form of the Trustee's Certificate of Authentication for the Series C
Senior Notes shall be in substantially the form set forth in Exhibit B hereto.
                                                             ---------

     Each Series C Senior Note shall be dated the date of authentication thereof
and shall bear interest from the date of original issuance thereof or from the
most recent Interest Payment Date to which interest has been paid or duly
provided for.

SECTION 102.  Definitions.
              -----------

   The following defined terms used herein shall, unless the context otherwise
requires, have the meanings specified below.  Capitalized terms used herein for
which no definition is provided herein shall have the meanings set forth in the
Original Indenture.

      "Adjusted Treasury Rate" means, with respect to any Redemption Date: (i)
the yield, under the heading which represents the average for the immediately
preceding week, appearing in the most recently published statistical release
designated "H.15(519)" or any successor publication which is published weekly by
the Board of Governors of the Federal Reserve System and which establishes
yields on actively traded United States Treasury securities adjusted to constant
maturity under the caption "Treasury Constant Maturities," for the maturity
corresponding to the Comparable Treasury Issue (if no maturity is within three
months before or after the Remaining Life, yields for the two published
maturities most closely corresponding to the Comparable Treasury Issue shall be
determined and the adjusted Treasury Rate shall be interpolated or extrapolated
from such yields on a straight line basis, rounding to the nearest month); or
(ii) if such release (or any successor release) is not published during the week
preceding the calculation date or does not contain such yields, the rate per
annum equal to the semi-annual equivalent yield to maturity of the Comparable
Treasury Issue, calculated using a price for the Comparable Treasury Issue
(expressed as a percentage of its principal amount) equal to the Comparable
Treasury Price for such Redemption Date.

     "Business Day" means a day other than (i) a Saturday or a Sunday, (ii) a
day on which banks in New York, New York are authorized or obligated by law or
executive order to remain closed or (iii) a day on which the Corporate Trust
Office is closed for business.

     "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining term of the Series C Senior Notes to be redeemed that would be
utilized, at the time of selection and in accordance with customary financial
practice, in pricing new issues of corporate debt securities of comparable
maturity to the remaining term of such Series C Senior Notes ("Remaining Life").

                                       2
<PAGE>

     "Comparable Treasury Price" means (i) the average of five Reference
Treasury Dealer Quotations for such Redemption Date, after excluding the highest
and lowest Reference Treasury Dealer Quotations, or (ii) if the Independent
Investment Banker obtains fewer than five such Reference Treasury Dealer
Quotations, the average of all such quotations.

     "Independent Investment Banker" means any of Banc of America Securities
LLC, Chase Securities Inc. or Lehman Brothers Inc. and their respective
successors as selected by the Company, or if all of such firms are unwilling or
unable to serve as such, an independent investment and banking institution of
national standing appointed by the Company.

     "Interest Payment Dates" means January 15 and July 15 of each year,
commencing on January 15, 2001.

     "Lien" means any mortgage, lien, pledge, security interest or other
encumbrance of any kind.

     "Material Subsidiary" means a Subsidiary of the Company whose total assets
(as determined in accordance with GAAP) represent at least 20% of the total
assets of the Company on a consolidated basis; provided, however, that in no
event shall Dominion Capital, Inc. be included as a Material Subsidiary.

     "Original Issue Date" means July 13, 2000.

     "Outstanding", when used with respect to the Series C Senior Notes, means,
as of the date of determination, all Series C Senior Notes, theretofore
authenticated and delivered under the Indenture, except:

          (i) Series C Senior Notes theretofore canceled by the Trustee or
delivered to the Trustee for cancellation;

          (ii) Series C Senior Notes for whose payment at Maturity the necessary
amount of money or money's worth has been theretofore deposited (other than
pursuant to Section 402) with the Trustee or any Paying Agent (other than the
Company) in trust or set aside and segregated in trust by the Company (if the
Company shall act as its own Paying Agent) for the Holders of such Series C
Senior Notes.

          (iii)  Series C Senior Notes with respect to which the Company has
effected defeasance or covenant defeasance has been effected pursuant to Section
402 of the Original Indenture; and

          (iv) Series C Senior Notes that have been paid pursuant to Section 306
or in exchange for or in lieu of which other Series C Senior Notes have been
authenticated and delivered pursuant to the Indenture, other than any such
Series C Senior Notes in respect of which there shall have been presented to the
Trustee proof satisfactory to it that such Series C Senior Notes are held by a
bona fide purchaser in whose hands such Series C Senior Notes are valid
obligations of the Company;

                                       3
<PAGE>

provided, however, that in determining whether the Holders of the requisite
principal amount of Outstanding Series C Senior Notes have given any request,
demand, authorization, direction, notice, consent or waiver hereunder or are
present at a meeting of Holders of Series C Senior Notes for quorum purposes,
Series C Senior Notes owned by the Company or any other obligor upon the Series
C Senior Notes or any Affiliate of the Company or such other obligor shall be
disregarded and deemed not to be Outstanding, except that, in determining
whether the Trustee shall be protected in making any such determination or
relying upon any such request, demand, authorization, direction, notice, consent
or waiver, only Series C Senior Notes which a Responsible Officer of the Trustee
knows to be so owned shall be so disregarded.  Series C Senior Notes so owned
which shall have been pledged in good faith may be regarded as Outstanding if
the pledgee establishes to the satisfaction of the Trustee (A) the pledgee's
right so to act with respect to such Series C Senior Notes and (B) that the
pledgee is not the Company or any other obligor upon the Series C Senior Notes
or an Affiliate of the Company or such other obligor.

     "Principal Property" means any plant or facility of the Company located in
the United States that in the opinion of the Board of Directors or management of
the Company is of material importance to the business conducted by the Company
and its consolidated Subsidiaries taken as whole.

      "Reference Treasury Dealer" means:  (i) each of Banc of America Securities
LLC, Chase Securities Inc. and Lehman Brothers Inc., and their respective
successors; provided that, if any of the foregoing ceases to be a primary U.S.
Government securities dealer in New York City (a "Primary Treasury Dealer"), the
Company shall substitute another Primary Treasury Dealer; and (ii) up to two
other Primary Treasury Dealers selected by the Company.

      "Reference Treasury Dealer Quotations" means, with respect to each
Reference Treasury Dealer and any Redemption Date, the average, as determined by
the Independent Investment Banker, of the bid and asked prices for the
Comparable Treasury Issue (expressed in each case as a percentage of its
principal amount) quoted in writing to the Independent Investment Banker at 5:00
p.m., New York City time, on the third Business Day preceding such Redemption
Date.

     "Regular Record Date" means, with respect to each Interest Payment Date,
the close of business on the 15th calendar day preceding such Interest Payment
Date.

     "Stated Maturity" means July 15, 2003.

SECTION 103.    Payment of Principal and Interest. The principal of the Series C
Senior Notes shall be due at the Stated Maturity (unless earlier redeemed). The
unpaid principal amount of the Series C Senior Notes shall bear interest at the
rate of 7.600% per annum until paid or duly provided for, such interest to
accrue from the Original Issue Date or from the most recent Interest Payment
Date to which interest has been paid or duly provided for. Interest shall be
paid semi-annually in arrears on each Interest Payment Date to the Person in
whose name the Series C Senior Notes are registered on the Regular Record Date
for such Interest Payment Date; provided that interest payable at the Stated
Maturity of principal or on a Redemption Date as provided herein will be paid to
the Person to whom principal is payable. Any such interest that is not so
punctually paid or duly provided for will forthwith cease to be payable to the
Holders

                                       4
<PAGE>

on such Regular Record Date and may either be paid to the Person or Persons in
whose name the Series C Senior Notes are registered at the close of business on
a Special Record Date for the payment of such defaulted interest to be fixed by
the Trustee (in accordance with Section 307 of the Original Indenture), notice
whereof shall be given to Holders of the Series C Senior Notes not less than ten
(10) days prior to such Special Record Date, or be paid at any time in any other
lawful manner not inconsistent with the requirements of any securities exchange,
if any, on which the Series C Senior Notes may be listed, and upon such notice
as may be required by any such exchange, all as more fully provided in the
Original Indenture.

     Payments of interest on the Series C Senior Notes will include interest
accrued to but excluding the respective Interest Payment Dates. Interest
payments for the Series C Senior Notes shall be computed and paid on the basis
of a 360-day year of twelve 30-day months. In the event that any date on which
interest is payable on the Series C Senior Notes is not a Business Day, then
payment of the interest payable on such date will be made on the next succeeding
day that is a Business Day (and without any interest or payment in respect of
any such delay), in each case with the same force and effect as if made on the
date the payment was originally payable.

     Payment of the principal and interest on the Series C Senior Notes shall be
made at the office of the Paying Agent in such coin or currency of the United
States of America as at the time of payment is legal tender for payment of
public and private debts, with any such payment that is due at the Stated
Maturity of any Series C Senior Notes or on a Redemption Date being made upon
surrender of such Series C Senior Notes to the Paying Agent. Payments of
interest (including interest on any Interest Payment Date) will be made, subject
to such surrender where applicable, at the option of the Company, (i) by check
mailed to the address of the Person entitled thereto as such address shall
appear in the Security Register or (ii) by wire transfer at such place and to
such account at a banking institution in the United States as may be designated
in writing to the Trustee at least sixteen (16) days prior to the date for
payment by the Person entitled thereto.  In the event that any date on which
principal and interest is payable on the Series C Senior Notes is not a Business
Day, then payment of the principal and interest payable on such date will be
made on the next succeeding day that is a Business Day (and without any interest
or payment in respect of any such delay), in each case with the same force and
effect as if made on the date the payment was originally payable.

SECTION 104.  Denominations.
              -------------
    The Series C Senior Notes may be issued in denominations of $1,000, or any
integral multiple thereof.

SECTION 105.  Global Securities . The Series C Senior Notes will be issued
initially in the form of one or more Global Securities registered in the name of
the Depositary (which shall be The Depository Trust Company) or its nominee.
Except under the limited circumstances described below, Series C Senior Notes
represented by such Global Securities will not be exchangeable for, and will not
otherwise be issuable as, Series C Senior Notes in definitive form. The Global
Securities described above may not be transferred except by the Depositary to a
nominee of the Depositary or by a nominee of the Depositary to the Depositary or
another nominee of the Depositary or to a successor Depositary or its nominee.

                                       5
<PAGE>

     Owners of beneficial interests in such a Global Security will not be
considered the Holders thereof for any purpose under the Indenture, and no
Global Security representing a Series C Senior Note shall be exchangeable,
except for another Global Security of like denomination and tenor to be
registered in the name of the Depositary or its nominee or to a successor
Depositary or its nominee or except as described below. The rights of Holders of
such Global Security shall be exercised only through the Depositary.

     A Global Security shall be exchangeable for Series C Senior Notes
registered in the names of persons other than the Depositary or its nominee only
if (i) the Depositary notifies the Company that it is unwilling or unable to
continue as a Depositary for such Global Security and no successor Depositary
shall have been appointed by the Company within 90 days of receipt by the
Company of such notification, or if at any time the Depositary ceases to be a
clearing agency registered under the Exchange Act at a time when the Depositary
is required to be so registered to act as such Depositary and no successor
Depositary shall have been appointed by the Company within 90 days after it
becomes aware of such cessation, or (ii) the Company in its sole discretion
determines that such Global Security shall be so exchangeable.  Any Global
Security that is exchangeable pursuant to the preceding sentence shall be
exchangeable for Series C Senior Notes registered in such names as the
Depositary shall direct.

     SECTION 106.  Redemption.  The Series C Senior Notes are redeemable, in
                   ----------
whole or in part, at any time, and at the option of the Company, at a Redemption
Price equal to the greater of:

      (i)  100% of the principal amount of Series C Senior Notes then
Outstanding to be so redeemed, or

      (ii) the sum of the present values of the remaining scheduled payments of
principal and interest thereon (not including any portion of such payments of
interest accrued as of the Redemption Date) discounted to the Redemption Date on
a semiannual basis (assuming a 360-day year consisting of twelve 30-day months)
at the Adjusted Treasury Rate, plus ten basis points, as calculated by an
Independent Investment Banker,

     plus, in either of the above cases, accrued and unpaid interest thereon to
the Redemption Date.

     Unless the Company defaults in the payment of the Redemption Price, on and
after the Redemption Date, interest will cease to accrue on the Series C Senior
Notes or portions thereof called for redemption.

     The Adjusted Treasury Rate shall be calculated on the third Business Day
preceding the Redemption Date.

     In the event of the redemption of the Series C Senior Notes in part only, a
new Series C Senior Note or Notes for the unredeemed portion will be issued in
the name or names of the Holders thereof upon surrender thereof.

                                       6
<PAGE>

     Notice of redemption shall be given as provided in Section 1104 of the
Original Indenture.

     SECTION 107.  Sinking Fund  The Series C Senior Notes shall not have a
                   ------------
 sinking fund.

     SECTION 108.  Additional Interest Any principal of and installment of
                   -------------------
interest on the Series C Senior Notes that is overdue shall bear interest at the
rate of 7.600% (to the extent that the payment of such interest shall be legally
enforceable), from the dates such amounts are due until they are paid or made
available for payment, and such interest shall be payable on demand.

     SECTION 109.  Paying Agent.  The Trustee shall initially serve as Paying
                   ------------
Agent with respect to the Series C Senior Notes, with the Place of Payment
initially being the Corporate Trust Office of the Trustee.

     SECTION 110.  Limitation on Liens.  The Company will not, while any of the
                   -------------------
Series C Senior Notes remain Outstanding, create, or suffer to be created or to
exist, any Lien upon any Principal Property of the Company or upon any shares of
stock of any Material Subsidiary of the Company, whether such Principal Property
is, or shares of stock are, now owned or hereafter acquired, to secure any
indebtedness for borrowed money of the Company, unless it shall make effective
provision whereby the Series C Senior Notes then Outstanding shall be secured by
such Lien equally and ratably with any and all indebtedness for borrowed money
thereby secured so long as any such indebtedness shall be so secured; provided,
however, that nothing in this Section shall be construed to prevent the Company
from creating, or from suffering to be created or to exist, any Liens, or any
agreements, with respect to:

     (1)  purchase money mortgages, or other purchase money liens, pledges,
          security interests or encumbrances of any kind upon property hereafter
          acquired by the Company, or Liens of any kind existing on any property
          or any shares of stock at the time of the acquisition thereof
          (including Liens which exist on any property or any shares of stock of
          a Person which is consolidated with or merged with or into the Company
          or which transfers or leases all or substantially all of its
          properties to the Company), or conditional sales agreements or other
          title retention agreements and leases in the nature of title retention
          agreements with respect to any property hereafter acquired; provided,
          however, that no such Lien shall extend to or cover any other property
          of the Company;

     (2)  Liens upon any property of the Company or any shares of stock of any
          Material Subsidiary of the Company existing as of the date of the
          initial issuance of the Series C Senior Notes or upon the shares of
          stock of any corporation, which Liens existed at the time such
          corporation became a Material Subsidiary of the Company; liens for
          taxes or assessments or other governmental charges or levies; pledges
          to secure other governmental charges or levies; pledges or deposits to
          secure obligations under worker's compensation laws, unemployment
          insurance and other social security legislation, including liens of
          judgments thereunder

                                       7
<PAGE>

          which are not currently dischargeable; pledges or deposits to secure
          performance in connection with bids, tenders, contracts (other than
          contracts for the payment of money) or leases to which the Company is
          a party; pledges or deposits to secure public or statutory obligations
          of the Company; builders', materialmen's, mechanics', carriers',
          warehousemen's, workers', repairmen's, operators', landlords' or other
          like liens in the ordinary course of business, or deposits to obtain
          the release of such liens; pledges or deposits to secure, or in lieu
          of, surety, stay, appeal, indemnity, customs, performance or
          return-of-money bonds; other pledges or deposits for similar purposes
          in the ordinary course of business; liens created by or resulting from
          any litigation or proceeding which at the time is being contested in
          good faith by appropriate proceedings; liens incurred in connection
          with the issuance of bankers' acceptances and lines of credit,
          bankers' liens or rights of offset and any security given in the
          ordinary course of business to banks or others to secure any
          indebtedness payable on demand or maturing within 12 months of the
          date that such indebtedness is originally incurred; liens incurred in
          connection with repurchase, swap or other similar agreements
          (including, without limitation, commodity price, currency exchange and
          interest rate protection agreements); leases made, or existing on
          property acquired, in the ordinary course of business; liens securing
          industrial revenue or pollution control bonds; liens, pledges,
          security interests or other encumbrances on any property arising in
          connection with any defeasance, covenant defeasance or in-substance
          defeasance of indebtedness of the Company, including the Series C
          Senior Notes; liens created in connection with, and created to secure,
          a non-recourse obligation; zoning restrictions, easements, licenses,
          rights-of-way, restrictions on the use of property or minor
          irregularities in title thereto, which do not, in the opinion of the
          Company, materially impair the use of such property in the operation
          of the business of the Company or the value of such property for the
          purpose of such business;

     (3)  Liens in favor of the United States, any foreign country or any
          department, agency or instrumentality or political subdivision of any
          such jurisdiction, to secure partial, progress, advance or other
          payments pursuant to any contract or statute or to secure any
          indebtedness incurred for the purpose of financing all or any part of
          the purchase price or the cost of constructing or improving the
          property subject to such mortgages, including, without limitation,
          mortgages to secure indebtedness of the pollution control or
          industrial revenue bond type;

     (4)  indebtedness which may be issued by the Company in connection with a
          consolidation or merger of the Company or any Material Subsidiary of
          the Company with or into any other Person (which may be an Affiliate
          of the Company or any Material Subsidiary of the Company) in exchange
          for or otherwise in substitution for secured indebtedness of such
          Person ("Third Party Debt") which by its terms (i) is secured by a
          mortgage on all or a portion of the property of such Person, (ii)
          prohibits secured indebtedness from being incurred by such Person,
          unless the Third Party Debt shall be secured equally and ratably with
          such secured indebtedness or (iii) prohibits secured indebtedness from
          being incurred by such Person;

                                       8
<PAGE>

     (5)  indebtedness of any Person which is required to be assumed by the
          Company in connection with a consolidation or merger of such Person,
          with respect to which any property of the Company is subjected to a
          Lien;

     (6)  Liens of any kind upon any property acquired, constructed, developed
          or improved by the Company (whether alone or in association with
          others) after the date of the initial issuance of the Series C Senior
          Notes which are created prior to, at the time of, or within 18 months
          after such acquisition (or in the case of property constructed,
          developed or improved, after the completion of such construction,
          development or improvement and commencement of full commercial
          operation of such property, whichever is later) to secure or provide
          for the payment of any part of the purchase price or cost thereof;
          provided that in the case of such construction, development or
          improvement the Liens shall not apply to any property theretofore
          owned by the Company other than theretofore unimproved real property;

     (7)  Liens in favor of the Company, one or more Material Subsidiaries of
          the Company, one or more wholly-owned Subsidiaries of the Company or
          any of the foregoing in combination;

     (8)  the replacement, extension or renewal (or successive replacements,
          extensions or renewals), as a whole or in part, of any Lien, or of any
          agreement, referred to above in clauses (1) through (7) inclusive, or
          the replacement, extension or renewal (not exceeding the principal
          amount of indebtedness secured thereby together with any premium,
          interest, fee or expense payable in connection with any such
          replacement, extension or renewal) of the indebtedness secured
          thereby; provided that such replacement, extension or renewal is
          limited to all or a part of the same property that secured the Lien
          replaced, extended or renewed (plus improvements thereon or additions
          or accessions thereto); or

     (9)  any other Lien not excepted by the foregoing clauses (1) through (8);
          provided that immediately after the creation or assumption of such
          Lien, the aggregate principal amount of indebtedness for borrowed
          money of the Company secured by all Liens created or assumed under the
          provisions of this clause (9) shall not exceed an amount equal to 10%
          of the common shareholders' equity of the Company, as shown on its
          consolidated balance sheet for the accounting period occurring
          immediately prior to the creation or assumption of such Lien.

     This Section 110 has been included in this Third Supplemental Indenture
expressly and solely for the benefit of the Series C Senior Notes and shall be
subject to covenant defeasance pursuant to Section 402(3) of the Original
Indenture.

                                       9
<PAGE>

                                  ARTICLE II
                           MISCELLANEOUS PROVISIONS

     SECTION 201.  Recitals by Company. The recitals in this Third Supplemental
                   -------------------
Indenture are made by the Company only and not by the Trustee, and all of the
provisions contained in the Original Indenture in respect of the rights,
privileges, immunities, powers and duties of the Trustee shall be applicable in
respect of the Series C Senior Notes and of this Third Supplemental Indenture as
fully and with like effect as if set forth herein in full.

     SECTION 202.  Ratification and Incorporation of Original Indenture.  As
                   ----------------------------------------------------
supplemented hereby, the Original Indenture is in all respects ratified and
confirmed, and the Original Indenture and this Third Supplemental Indenture
shall be read, taken and construed as one and the same instrument.

     SECTION 203.  Executed in Counterparts.  This Supplemental Indenture may be
                   ------------------------
executed in several counterparts, each of which shall be deemed to be an
original, and such counterparts shall together constitute but one and the same
instrument.

     SECTION 204.  Assignment.  The Company shall have the right at all times to
                   ----------
assign any of its rights or obligations under the Indenture with respect to the
Series C Senior Notes to a direct or indirect wholly-owned subsidiary of the
Company; provided that, in the event of any such assignment, the Company shall
remain primarily liable for the performance of all such obligations. The
Indenture may also be assigned by the Company in connection with a transaction
described in Article Eight of the Original Indenture.

                                       10
<PAGE>

     IN WITNESS WHEREOF, each party hereto has caused this instrument to be
signed in its name and behalf by its duly authorized officer, all as of the day
and year first above written.

                                       DOMINION RESOURCES, INC.



                                        By:___________________________________

                                        Name:_________________________________

                                        Title:________________________________


                                        THE CHASE MANHATTAN BANK, as Trustee



                                        By:____________________________________

                                        Name:__________________________________

                                        Title:_________________________________

                                       11
<PAGE>

                                   EXHIBIT A

                                    FORM OF
                       2000 SERIES C 7.600% SENIOR NOTE,
                               DUE JULY 15, 2003

     [UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) TO THE ISSUER
OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY
CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF [CEDE & CO.] OR SUCH OTHER NAME
AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY AND
ANY PAYMENT IS MADE TO [CEDE & CO.], ANY TRANSFER, PLEDGE OR OTHER USE HEREOF
FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE REGISTERED
OWNER HEREOF, [CEDE & CO.,] HAS AN INTEREST HEREIN.]**

     [THIS SERIES C SENIOR NOTE IS A GLOBAL SECURITY WITHIN THE MEANING OF THE
INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY
OR A NOMINEE THEREOF.  THIS SERIES C SENIOR NOTE MAY NOT BE EXCHANGED IN WHOLE
OR IN PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS SERIES C SENIOR
NOTE IN WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN
SUCH  DEPOSITARY OR A NOMINEE THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES
DESCRIBED IN THE INDENTURE.]/**/


                         ============================
                           DOMINION RESOURCES, INC.
                         ============================

                                $_____________
                       2000 SERIES C 7.600% SENIOR NOTE,
                               DUE JULY 15, 2003

No. ___                                                CUSIP No. ___


     Dominion Resources, Inc., a corporation duly organized and existing under
the laws of Virginia (herein called the "Company", which term includes any
successor Person under the Indenture hereinafter referred to), for value
received, hereby promises to pay to [Cede & Co.] **, or registered assigns (the
"Holder"), the principal sum of ____________ Dollars ($_____) on July 15, 2003
and to pay interest thereon from July 13, 2000 or from the most recent Interest

-----------------------------
** Insert in Global Securities.
<PAGE>

Payment Date to which interest has been paid or duly provided for, semi-annually
on January 15 and July 15 in each year, commencing on January 15, 2001, at the
rate of 7.600% per annum, until the principal hereof is paid or made available
for payment, provided that any principal, and any such installment of interest,
that is overdue shall bear interest at the rate of 7.600% per annum (to the
extent that the payment of such interest shall be legally enforceable), from the
dates such amounts are due until they are paid or made available for payment,
and such interest shall be payable on demand.  The interest so payable, and
punctually paid or duly provided for, on any Interest Payment Date will, as
provided in such Indenture, be paid to the Person in whose name this Series C
Senior Note (or one or more Predecessor Securities) is registered at the close
of business on the Regular Record Date for such interest, which shall be the
fifteenth calendar day (whether or not a Business Day) next preceding such
Interest Payment Date; provided that interest payable at the Stated Maturity of
principal or on a Redemption Date will be paid to the Person to whom principal
is payable.  Any such interest not so punctually paid or duly provided for will
forthwith cease to be payable to the Holder on such Regular Record Date and may
either be paid to the Person in whose name this Series C Senior Note (or one or
more Predecessor Securities) is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of Series C Senior Notes not
less than 10 days prior to such Special Record Date, or be paid at any time in
any other lawful manner not inconsistent with the requirements of any securities
exchange on which the Series C Senior Notes may be listed, and upon such notice
as may be required by such exchange, all as more fully provided in said
Indenture.

     Payment of the principal of and any such interest on this Series C Senior
Note will be made at the office of the Paying Agent, in the Borough of
Manhattan, City and State of New York, in such coin or currency of the United
States of America as at the time of payment is legal tender for payment of
public and private debts, with any such payment that is due at the Stated
Maturity of any Series C Senior Note or on a Redemption Date being made upon
surrender of such Series C Senior Note to such office or agency; provided,
however, that at the option of the Company payment of interest, subject to such
surrender where applicable, may be made (i) by check mailed to the address of
the Person entitled thereto as such address shall appear in the Security
Register or (ii) by wire transfer at such place and to such account at a banking
institution in the United States as may be designated in writing to the Trustee
at least sixteen (16) days prior to the date for payment by the Person entitled
thereto.

     Reference is hereby made to the further provisions of this Series C Senior
Note set forth on the reverse hereof, which further provisions shall for all
purposes have the same effect as if set forth at this place.

     Unless the certificate of authentication hereon has been executed by the
Trustee referred to on the reverse hereof by manual signature, this Series C
Senior Note shall not be entitled to any benefit under the Indenture or be valid
or obligatory for any purpose.

                                       2
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

Dated:                                       Dominion Resources, Inc.


                                             By: ______________________________

                                                 Name: ________________________

                                                 Title: _______________________


                       [REVERSE OF SERIES C SENIOR NOTE]

     This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of June 1, 2000, as supplemented by a First
Supplemental Indenture dated as of June 1, 2000, a Second Supplemental Indenture
dated as of July 1, 2000 and a Third Supplemental Indenture dated as of July 1,
2000 (as amended or supplemented from time to time, herein called the
"Indenture", which term shall have the meaning assigned to it in such
instrument), between the Company and The Chase Manhattan Bank, as Trustee
(herein called the "Trustee", which term includes any successor trustee under
the Indenture), and reference is hereby made to the Indenture for a statement of
the respective rights, limitations of rights, duties and immunities thereunder
of the Company, the Trustee and the Holders of the Securities and of the terms
upon which the Securities are, and are to be, authenticated and delivered.  This
Security is one of the series designated on the face hereof (the "Series C
Senior Notes") which is unlimited in aggregate principal amount.

     The Series C Senior Notes are redeemable, in whole or in part, at any time,
in the manner and with the effect provided in the Indenture.

     If an Event of Default with respect to Series C Senior Notes shall occur
and be continuing, the principal of the Series C Senior Notes may be declared
due and payable in the manner and with the effect provided in the Indenture.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of a majority in principal amount of the Securities at
the time Outstanding of each series to be affected.  The Indenture also contains
provisions permitting the Holders of specified percentages in principal amount
of the Securities of each series at the time Outstanding, on behalf of the
Holders of all Securities of such series, to waive certain past defaults under
the Indenture and their consequences.  Any such consent or waiver by the Holder
of this Series C Senior Note shall be conclusive and binding upon such

                                       3
<PAGE>

Holder and upon all future Holders of this Series C Senior Note and of any
Series C Senior Note issued upon the registration of transfer hereof or in
exchange therefor or in lieu hereof, whether or not notation of such consent or
waiver is made upon this Series C Senior Note.

     As provided in and subject to the provisions of the Indenture, the Holder
of this Series C Senior Note shall not have the right to institute any
proceeding with respect to the Indenture or for the appointment of a receiver or
trustee or for any other remedy thereunder, unless such Holder shall have
previously given the Trustee written notice of a continuing Event of Default
with respect to the Series C Senior Notes, the Holders of not less than a
majority in principal amount of the Series C Senior Notes at the time
Outstanding shall have made written request to the Trustee to institute
proceedings in respect of such Event of Default as Trustee and offered the
Trustee reasonable indemnity, and the Trustee shall not have received from the
Holders of a majority in principal amount of Series C Senior Notes at the time
Outstanding a direction inconsistent with such request, and shall have failed to
institute any such proceeding for 60 days after receipt of such notice, request
and offer of indemnity.  The foregoing shall not apply to any suit instituted by
the Holder of this Series C Senior Note for the enforcement of any payment of
principal hereof or premium, if any, or interest hereon on or after the
respective due dates expressed or provided for herein.

     No reference herein to the Indenture and no provision of this Series C
Senior Note or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of, premium,
if any, and interest on this Series C Senior Note at the times, place and rate,
and in the coin or currency, herein prescribed.

     As provided in the Indenture and subject to certain limitations therein set
forth, the transfer of this Series C Senior Note is registrable in the Security
Register, upon surrender of this Series C Senior Note for registration of
transfer at the office or agency of the Company in any place where the principal
of, premium, if any, and interest on this Series C Senior Note are payable, duly
endorsed by, or accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed by, the
Holder hereof or his attorney duly authorized in writing, and thereupon one or
more new Series C Senior Notes and of like tenor, of authorized denominations
and for the same aggregate principal amount, will be issued to the designated
transferee or transferees.

     The Series C Senior Notes are issuable only in registered form without
coupons in denominations of $1,000 and any integral multiple thereof.  As
provided in the Indenture and subject to certain limitations therein set forth,
Series C Senior Notes are exchangeable for a like aggregate principal amount of
Series C Senior Notes having the same Stated Maturity and of like tenor of any
authorized denominations as requested by the Holder upon surrender of the Series
C Senior Note or Series C Senior Notes to be exchanged at the office or agency
of the Company.

     No service charge shall be made for any such registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

                                       4
<PAGE>

     Prior to due presentment of this Series C Senior Note for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Security is registered as the owner
hereof for all purposes, whether or not this Series C Senior Note be overdue,
and neither the Company, the Trustee nor any such agent shall be affected by
notice to the contrary.

     All terms used in this Series C Senior Note that are defined in the
Indenture shall have the meanings assigned to them in the Indenture.

                                       5
<PAGE>

                                 ABBREVIATIONS

The following abbreviations, when used in the inscription on the face of this
instrument, shall be construed as though they were written out in full according
to applicable laws or regulations:

TEN COM --                 as tenants in common

TEN ENT --                 as tenants by the entireties

JT TEN --                  as joint tenants with rights of survivorship and not
                           as tenants in common

UNIF GIFT MIN ACT --       __________________________________________ Custodian
                           for
                           (Cust)


                           __________________________________________
                           (Minor)

                           Under Uniform Gifts to Minors Act of


                           __________________________________________
                           (State)

Additional abbreviations may also be used though not on the above list.
______________________________________________________________

     FOR VALUE RECEIVED, the undersigned hereby sell(s) and transfer(s) unto
____________________ (please insert Social Security or other identifying number
of assignee).

______________________________________________________________
______________________________________________________________
______________________________________________________________

PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING POSTAL ZIP CODE OF
ASSIGNEE

the within Series C Senior Note and all rights thereunder, hereby irrevocably
constituting and appointing

______________________________________________________________
______________________________________________________________
______________________________________________________________

                                       6
<PAGE>

______________________________________________________________
______________________________________________________________
______________________________________________________________

agent to transfer said Series C Senior Note on the books of the Company, with
full power of substitution in the premises.

Dated: __________________ __, ____


             ------------------------------------------------------


NOTICE:  The signature to this assignment must correspond with the name as
written upon the face of the within instrument in every particular without
alteration or enlargement, or any change whatever.

                                       7
<PAGE>

                                   EXHIBIT B
                         CERTIFICATE OF AUTHENTICATION


     This is one of the Securities of the series designated therein referred to
in the within-mentioned Indenture.

                                             THE CHASE MANHATTAN BANK,
                                             as Trustee


                                             By: _____________________________
                                                 Authorized Officer

                                       8