<PAGE>   1
                                                                   EXHIBIT 10.28

                      SECOND AMENDMENT TO CREDIT AGREEMENT

         THIS DOCUMENT is entered into as of May 17, 1999, between TEPPCO
COLORADO, LLC, a Delaware limited liability company ("BORROWER"), the Required
Lenders listed on the signature page to this document, and SUNTRUST BANK,
ATLANTA, as Agent for Lenders ("AGENT").

         Borrower, Lenders, and Agent are party to the Credit Agreement (as it
may have been renewed, extended, and amended through the date of this document,
the "CREDIT AGREEMENT") dated as of April 21, 1998, providing for a $38,000,000
term loan to Borrower. Borrower, Required Lenders, and Agent have agreed, upon
the following terms and conditions, to amend the Credit Agreement as provided
in PARAGRAPH 2 below. Accordingly, for adequate and sufficient consideration,
Borrower, Required Lenders, and Agent agree as follows:

1.       TERMS AND REFERENCES. Unless otherwise stated in this document (A)
terms defined in the Credit Agreement have the same meanings when used in this
document and (B) references to "SECTIONS," "SCHEDULES," and "EXHIBITS" are to
the Credit Agreement's sections, schedules, and exhibits.

2.       AMENDMENTS. The Credit Agreement is amended as follows:

         (A)      SECTION 1.1 is amended by entirely amending or adding the
following definitions in alphabetical order with the other definitions in that
section:

                  "ACQUISITION" by any Person means any transaction or series
         of transactions on or after the Closing Date pursuant to which that
         Person directly or indirectly -- whether in the form of a capital
         expenditure, an Investment, a merger, a consolidation, or otherwise
         and whether through a solicitation of tender of equity securities, one
         or more negotiated block, market, private, other transactions, or any
         combination of the foregoing -- purchases (a) all or substantially all
         of the business or assets of any other individual or entity or
         operating division or business unit of any other individual or entity,
         or (b) more than 25% of the equity interest in any other individual or
         entity.

                  "DEBT" means -- for any Person, at any time, and without
         duplication -- the sum of (a) all Funded Debt of that Person, plus (b)
         all obligations arising under acceptance facilities or facilities for
         the discount or sale of accounts receivable, plus (c) all direct or
         contingent obligations in respect of letters of credit, plus (d) each
         obligation for Hedging Exposure of $10,000,000 or more, plus (e) all
         guaranties, endorsements, and other contingent obligations for the
         obligations in respect of obligations of other persons or entities of
         the nature described in CLAUSES (A) through (D) above.

                  "EBITDA" means:

                           (a)    For any period consisting of four consecutive
                  fiscal quarters taken as a single accounting period, for any
                  Person, and without duplication, the sum of (i) Net Income
                  plus (ii) to the extent actually deducted in determining Net
                  Income, Interest Expense, Tax Expense, depreciation, and
                  amortization; and

                           (b)     For purposes of calculating EBITDA in
                  respect of any entity that became a Subsidiary of that Person
                  or was merged with or consolidated into that Person during
                  that period, EBITDA of that Person shall include the EBITDA
                  of that entity during that period and before the date of that
                  acquisition, merger, or consolidation for a total period of
                  four consecutive fiscal quarters.


                                                                SECOND AMENDMENT
<PAGE>   2

                  "FUNDED DEBT" means -- for any Person, at any time, and
         without duplication -- the SUM of (a) the unpaid principal amount or
         component of all obligations for borrowed money, PLUS (b) the unpaid
         principal amount or component of all obligations evidenced by bonds,
         debentures, notes or similar instruments, PLUS (c) the unpaid
         principal amount or component of all obligations to pay the deferred
         purchase price of property or service except trade accounts payable
         arising in the ordinary course of business, PLUS (d) in respect of all
         obligations that are secured (or for which the holder of any such
         obligation has an existing Right, contingent or otherwise, to be so
         secured) by any Lien on property owned or acquired by that Person, the
         lesser of EITHER the unpaid amount of all of those obligations from
         time to time outstanding OR the fair-market value of the property
         securing all of those obligations, liabilities secured (or for which
         the holder of such obligations has an existing Right, contingent or
         otherwise, to be so secured) by any Lien existing on property owned or
         acquired by that Person, PLUS (e) all Capital Lease obligations, PLUS
         (f) the unpaid principal amount or component of all obligations under
         synthetic leases, PLUS (g) the unpaid principal amount or component of
         all guaranties, endorsements, and other contingent obligations in
         respect of obligations of other persons or entities of the nature
         described in CLAUSES (A) through (F) above.

                  "GUARANTOR CREDIT AGREEMENT" means the Credit Agreement dated
         as of May 17, 1999, between Guarantor, certain lenders, and SunTrust
         Bank, Atlanta, as administrative agent for those lenders.

                  "INTEREST EXPENSE" means, for any Person and any period, all
         interest expense (including all amortization of debt discount and
         expenses and reported interest) on all Funded Debt of that Person.

                  "MATERIAL-ADVERSE EVENT" means any circumstance or event
         that, individually or collectively, is, or is reasonably expected to
         result (at any time before the Commitments are fully cancelled or
         terminated and the Obligation is fully paid and performed) in, any (a)
         material impairment of (i) the ability of Borrower or Guarantor to
         perform any of their respective payment or other material obligations
         under any Credit Document, or (ii) the ability of Agent or any Lender
         to enforce any of those obligations or any of their respective Rights
         under the Credit Documents (OTHER THAN as a result of its own act or
         omission), (b) material and adverse effect on the financial condition
         of Guarantor individually, or Parent and its Subsidiaries as a whole
         as represented to Lenders in the Current Financials most recently
         delivered before the date of this agreement, or (c) Event of Default
         or Potential Default.

                  "NET INCOME" means, for any Person and any period, that
         Person's profit or loss (a) after deducting all of its operating
         expenses, provision for Taxes, and reserves (including reserves for
         deferred income Taxes), and all other deductions in accordance with
         GAAP, but (b) excluding (i) extraordinary items, and (ii) the profit
         or loss of any entity accrued before the date that (A) it becomes a
         Subsidiary of such Person, (B) it is merged with such Person or any of
         its Subsidiaries, or (C) its assets are acquired by such Person of any
         of its Subsidiaries.

                  "OTHER CREDIT AGREEMENTS" means the Guarantor Credit
         Agreement and the TEPPCO Crude Credit Agreement.

                  "RESPONSIBLE OFFICER" means the chairman, president, vice
         president, chief executive officer, chief financial officer,
         treasurer, or corporate secretary of General Partner.

                  "TEPPCO CRUDE" means TEPPCO Crude Oil, LLC, a Delaware
         limited liability company.


                                       2                        SECOND AMENDMENT
<PAGE>   3
                  "TEPPCO CRUDE CREDIT AGREEMENT" means the Credit Agreement
         dated as of the date of this agreement, between TEPPCO Crude, certain
         lenders, and SunTrust Bank, Atlanta, as administrative agent for those
         lenders.

                  "Y2K ISSUE" means the risk that computer applications used by
         the Companies or by any of their respective suppliers or vendors may
         be unable properly to recognize and perform date-sensitive functions.

         (B)      A new SECTION 5.20 is added as follows:

                  5.20   Y2K ISSUE. Each Company has (a) initiated a review and
         assessment of all areas within businesses and operations (including
         those affected by suppliers and vendors) that could be adversely
         affected by the Y2K Issue, (b) developed a plan and time line for
         addressing the Y2K Issue on a timely basis, and (c) to date
         implemented in all material respects that plan in accordance with that
         timetable.

         (C)      SECTIONS 6.1(a) and 6.1(b) are entirely amended as follows:

                  (a)    ANNUAL FINANCIALS. Promptly after preparation but no
         later than 90 days after the last day of each fiscal year of: (i)
         Parent, Financials showing the consolidated and consolidating
         financial condition and results of operations of Parent and its
         Subsidiaries as of, and for the year ended on, that last day,
         accompanied by (A) the opinion, without material qualification, of
         KPMG LLP or other firm of nationally-recognized independent certified
         public accountants reasonably acceptable to Required Lenders, based on
         an audit using generally accepted auditing standards, that those
         Financials were prepared in accordance with GAAP and present fairly,
         in all material respects, the consolidated and consolidating financial
         condition and results of operations of Parent and its Subsidiaries,
         and (B) a related Compliance Certificate from a Responsible Officer,
         on behalf of Parent; and (ii) Guarantor, Financials showing the
         consolidated and consolidating financial condition and results of
         operations of Guarantor and its Subsidiaries as of, and for the year
         ended on, that last day, accompanied by a Compliance Certificate,
         together with a completed copy of the schedule to that certificate,
         from a Responsible Officer, on behalf of Guarantor.

                  (b)    QUARTERLY REPORTS. Promptly after preparation but no
         later than 45 days after the last day of each of the first three
         fiscal quarters of Parent and the Companies each year, Financials
         showing the consolidated and consolidating financial condition and
         results of operations of Parent and its Subsidiaries, and of Guarantor
         and its Subsidiaries for that fiscal quarter and for the period from
         the beginning of the current fiscal year to the last day of that
         fiscal quarter, accompanied in each case by a related Compliance
         Certificate, together with a completed copy of the schedule to that
         certificate, signed by a Responsible Officer, on behalf of Parent or
         Guarantor, as the case may be.

         (D)      A new SECTION 6.1(h) is added as follows:

                  (h)    Y2K. Notice promptly after any Company discovers or
         determines that any computer applications (including those of
         suppliers and vendors to any Company) that are material to the
         businesses or operations of any Company will not be compliant in
         timely resolving the Y2K Issue if that failure could reasonably be
         expected to be a Material-Adverse Event.

         (E)      The first sentence of SECTION 7 is amended by inserting the
following parenthetical immediately after the 37th word in that sentence:

                  "(which shall not be unreasonably withheld)"


                                       3                        SECOND AMENDMENT
<PAGE>   4

         (F)      SECTION 7.1 is entirely amended as follows:

                  7.1      DEBT. No Company may have any Debt except the
         following (the "PERMITTED DEBT"):

                           (a)    OBLIGATION.  The Obligation and Guaranty
                  under this agreement.

                           (b)    EXISTING DEBT. The Debt described on SCHEDULE
                  5.12 (other than any such Debt that is described on that
                  schedule as to be paid with the proceeds of the Term Loan),
                  together with all renewals, extensions, amendments,
                  modifications, and refinancings of (but not any principal
                  increases to) any of that Debt.

                           (c)    DEBT OF GUARANTOR. Debt of Guarantor incurred
                  pursuant to the Guarantor Credit Agreement.

                           (d)    HEDGING AGREEMENTS.  Solely in respect of
                  Guarantor, Hedging Agreements.

         (G)      SECTION 7.2 is entirely amended as follows:

                  7.2      SENIOR NOTES. No Company may materially amend or
         modify the terms of the Senior Notes or the related Indenture except
         as permitted by the express terms thereof.

         (H)      SECTION 7.4 is entirely amended as follows:

                  7.4      LIENS. No Company may (a) create, incur, or suffer
         or permit to be created or incurred or to exist any Lien upon any of
         its assets except Permitted Liens or (b) enter into or permit to exist
         any arrangement or agreement that directly or indirectly prohibits any
         Company from creating or incurring any Lien on any of its assets
         EXCEPT (i) the Credit Documents, (ii) the Other Credit Agreements and
         related loan documents, (iii) any lease that places a Lien prohibition
         on only the property subject to that lease, and (iv) arrangements and
         agreements that apply only to property subject to Permitted Liens. The
         following are "PERMITTED LIENS":

                  (a)      EXISTING LIENS. The existing Liens that are
         described on SCHEDULE 5.13 and all renewals, extensions, amendments,
         and modifications of any of them to the extent that the total-
         principal amount each individually secures never exceeds the
         total-principal amount secured by it on the date of this agreement.

                  (b)      THIS TRANSACTION. Liens, if any, ever granted to
         Agent in favor of Lenders to secure all of any part of the Obligation.

                  (c)      BONDS. Liens securing any industrial development,
         pollution control, or similar revenue bonds that never exceed a total
         principal amount of $15,000,000.

                  (d)      FORECLOSED PROPERTIES. Liens existing on any
         property acquired by a Company in connection with the foreclosure or
         other exercise of its Lien on the property.

                  (e)      SETOFFS. Subject to any limitations imposed upon
         them in the Credit Documents, rights of set off or recoupment and
         banker's Liens.

                  (f)      INSURANCE. Pledges or deposits made to secure
         payment of workers' compensation, unemployment insurance, or other
         forms of governmental insurance or benefits or to participate in


                                       4                        SECOND AMENDMENT
<PAGE>   5

         any fund in connection with workers' compensation, unemployment
         insurance, pensions, or other social security programs.

                  (g)      BIDS AND BONDS. Good-faith pledges or deposits (i)
         for 10% or less of the amounts due under (and made to secure) any
         Company's performance of bids, tenders, contracts (EXCEPT for the
         repayment of borrowed money), (ii) in respect of any operating lease,
         that are for up to but not more than the greater of EITHER 10% of the
         total rental obligations for the term of the lease OR 50% of the total
         rental obligations payable during the first year of the lease, or
         (iii) made to secure statutory obligations, surety or appeal bonds, or
         indemnity, performance, or other similar bonds benefitting any Company
         in the ordinary course of its business.

                  (h)      PERMITS. Conditions in any permit, license, or order
         issued by a Governmental Authority for the ownership and operation of
         a pipeline that do not materially impair the ownership or operation of
         the pipeline.

                  (i)      PROPERTY RESTRICTIONS. Zoning and similar
         restrictions on the use of, and easements, restrictions, covenants,
         title defects, and similar encumbrances on, any Real Property or
         pipeline right-of-way that (i) do not materially impair the Company's
         use of the Real Property or pipeline right-of-way and (ii) are not
         violated by existing or proposed structures (including the pipeline)
         or land use.

                  (j)      EMINENT DOMAIN. The Right reserved to, or vested in,
         any Governmental Authority (or granted by a Governmental Authority to
         another Person) by the terms of any Right, franchise, grant, license,
         permit, or Legal Requirements to purchase or recapture, or to
         designate a purchaser of, any property.

                  (k)      INCHOATE LIENS. If no Lien has been filed in any
         jurisdiction or agreed to (i) claims and Liens for Taxes not yet due
         and payable, (ii) mechanic's Liens and materialman's Liens for
         services or materials and similar Liens incident to construction and
         maintenance of real property, in each case for which payment is not
         yet due and payable, (iii) landlord's Liens for rental not yet due and
         payable, and (iv) Liens of warehousemen and carriers and similar Liens
         securing obligations that are not yet due and payable.

                  (l)      MISCELLANEOUS. Any of the following to the extent
         that the validity or amount is being contested in good faith and by
         appropriate and lawful proceedings diligently conducted, reserve or
         other appropriate provision (if any) required by GAAP has been made,
         levy and execution has not issued or continues to be stayed, and they
         do not individually or collectively detract materially from the value
         of the property of the Company in question or materially impair the
         use of that property in the operation of its business: (i) Claims and
         Liens for Taxes; (ii) claims and Liens upon, and defects of title to,
         real or personal property, including any attachment of personal or
         real property or other legal process before adjudication of a dispute
         on the merits; (iii) claims and Liens of mechanics, materialmen,
         warehousemen, carriers, landlords, or other like Liens; (iv)
         Liens incident to construction and maintenance of real property; and
         (v) adverse judgments, attachments, or orders on appeal for the
         payment of money.

         (I)      SECTION 7.8 is entirely amended as follows:

                  7.8      INVESTMENTS. No Company may make any Investments
         except the following (the "PERMITTED INVESTMENTS"):


                                       5                        SECOND AMENDMENT
<PAGE>   6

                           (a)    INVESTMENT POLICY. Investments specifically
                  permitted by General Partner's short-term cash and long-term
                  investment policies, true and correct copies of which have
                  been provided to Agent as they are from time to time in
                  effect.

                           (b)    PERMITTED ACQUISITIONS. Any Acquisition so
                  long as (i) no Event of Default or Potential Default exists
                  immediately before, or will occur as a result of (or
                  otherwise will exist immediately after), that Acquisition,
                  (ii) that Acquisition will not cause any of the
                  representations or warranties (unless they speak to a
                  specific date or are based on facts which have changed by
                  transactions contemplated or expressly permitted by this
                  agreement) in the Credit Documents to be materially
                  incorrect, (iii) that Acquisition is within the same or
                  substantially the same type of business as the Companies as
                  of the Closing Date, (iv) the board of directors (or similar
                  governing body) of the Person to be acquired has not notified
                  any Company or any Lender that it opposes the offer by any
                  Company to acquire that Person and that opposition has not
                  been withdrawn, (v) if structured as a merger or
                  consolidation, SECTION 7.11 is complied with, and (vi)
                  promptly after that Acquisition is completed, Borrower gives
                  to Lenders a written description of the acquired entity and
                  of its business and operations.

         For purposes of this SECTION 7, the total amount outstanding of any
         Investment by any Person in any other Person is to be determined net
         of repayments and dividends to, and sales of securities of the second
         Person by, the first Person.


                                       6                       SECOND AMENDMENT
<PAGE>   7
         (J)      SECTION 7.9 is entirely amended as follows:

                  7.9      DISTRIBUTIONS.  No Company may:

                           (a)    enter into or permit to exist any arrangement
                  or agreement (other than this agreement and the Other Credit
                  Agreements) that prohibits it from paying Distributions to
                  its equity holders; or

                           (b)    declare, make, or pay any Distribution other
                  than (i) Distributions from any Subsidiary of Borrower to its
                  parent corporation and (ii) Distributions from Borrower to
                  Guarantor at any time when no Potential Default or Event of
                  Default exists or would exist immediately after that
                  Distribution.

         (K)      SECTION 7.10(b) is entirely amended as follows:

                           (b)    Guarantor may not sell, assign, lease,
                  transfer, or otherwise dispose of any of its assets
                  (including equity interests in any other Company) OTHER THAN
                  (a) dispositions in the ordinary course of business for a
                  fair and adequate consideration and (b) dispositions of
                  assets that are obsolete or are no longer in use and are not
                  significant to the continuation of Guarantor's business.

         (L)      A new SECTION 7.17 is added as follows:

                  7.17     AMENDMENT OF CONSTITUENT DOCUMENTS. No Company shall
         materially amend or modify (or permit the material amendment or
         modification of) its Constituent Documents.

         (M)      SECTION 8 is entirely amended as follows:

                  SECTION 8.    FINANCIAL COVENANTS. As long as any Lender is
         committed to lend under this agreement and until the Obligation has
         been fully paid and performed, Borrower covenants and agrees with
         Administrative Agent and Lenders that, without first obtaining
         Required Lenders' consent to the contrary, the following may not occur
         or exist as applicable to the Companies and as determined as of the
         last day of each fiscal quarter of Borrower:

                           8.1  MINIMUM NET WORTH. The Companies' stockholders'
                  equity may never be less than the sum of (a) $187,648,000,
                  plus (b) 15% of the Companies' cumulative, quarterly Net
                  Income (without deduction for losses) after December 31,
                  1998, plus (c) 100% of all equity contributions to Guarantor
                  after December 31, 1998.

                           8.2  MAXIMUM FUNDED DEBT TO EBITDA. The ratio of the
                  Companies' Funded Debt to the Companies' EBITDA may never
                  exceed the following, as applicable:


<TABLE>
<CAPTION>
                               ===========================================
                                    QUARTER(S) ENDING            RATIO
                               ===========================================
                               <S>                           <C>
                               06/30/99 through 03/31/01     4.50 to 1.00
                               06/30/01 through 12/31/02     4.00 to 1.00
                               03/31/03 and thereafter       3.75 to 1.00
                               ===========================================
</TABLE>


                                       7                        SECOND AMENDMENT
<PAGE>   8

                           8.3  FIXED CHARGE COVERAGE RATIO. The ratio of (a)
                  the Companies' EBITDA to (b) the Companies' Interest Expense
                  and expenditures for the maintenance or repair of capital
                  assets may never be less than the following, as applicable:


<TABLE>
<CAPTION>
                               ===========================================
                                    QUARTER(S) ENDING            RATIO
                               ===========================================
                               <S>                           <C>
                               06/30/99 through 12/31/00     1.75 to 1.00
                               03/31/01 and thereafter       2.00 to 1.00
                               ===========================================
</TABLE>

         (N)      SECTION 9.3 is entirely amended as follows:

                  9.3      DEBTOR RELIEF. Any Company (a) is not Solvent, (b)
         fails to pay its Debts generally as they become due, (c) voluntarily
         seeks, consents to, or acquiesces in the benefit of any Debtor Law, or
         (d) becomes a party to or is made the subject of any proceeding
         (except as a creditor or claimant) provided for by any Debtor Law
         (unless, if the proceeding is involuntary, the applicable petition is
         dismissed within 60 days after its filing).

         (O)      SECTION 9.4 is entirely amended as follows:

                  9.4      JUDGMENTS AND ATTACHMENTS. Where the amounts in
         controversy or of any judgments, as the case may be, exceed (from and
         after the Closing Date and individually or collectively) $25,000,000
         for Parent or Guarantor or $1,000,000 for any other Company, such
         entity fails (a) to have discharged, within 60 days after its
         commencement, any attachment, sequestration, or similar proceeding
         against any of its assets or (b) to pay any money judgment against it
         within ten days before the date on which any of its assets may be
         lawfully sold to satisfy that judgment.

         (P)      SECTION 9.8 is entirely amended as follows:

                  9.8      OTHER DEBT.

                           (a)    OTHER CREDIT AGREEMENTS.  The existence of
                  an "Event of Default" under either of the Other Credit
                  Agreements.

                           (b)    OTHER. In respect of any Senior Notes or in
                  respect of any other Debt owed by any Company (other than the
                  Obligation) individually or collectively of at least
                  $10,000,000 (a) any Company fails to make any payment when
                  due (inclusive of any grace, extension, forbearance, or
                  similar period), or (b) any default or other event or
                  condition occurs or exists beyond the applicable grace or
                  cure period, the effect of which is to cause or to permit any
                  holder of that Debt to cause (whether or not it elects to
                  cause) any of that Debt to become due before its stated
                  maturity or regularly scheduled payment dates, or (c) any of
                  that Debt is declared to be due and payable or required to be
                  prepaid by any Company before its stated maturity.

         (Q)      EXHIBIT C is entirely amended in the form of, and all
references in the Credit Agreement to that exhibit are changed to, the attached
AMENDED EXHIBIT C.


                                       8                        SECOND AMENDMENT
<PAGE>   9

3.       CONDITIONS PRECEDENT. Notwithstanding any contrary provision, the
foregoing paragraph in this document is not effective unless and until (A) the
representations and warranties in this document are true and correct and (B)
Agent receives counterparts of this document executed by each party named on
the signature page of this document.

4.       REPRESENTATIONS. To induce Lenders and Agent to enter into this
document, Borrower represents and warrants to Lenders and Agent that as of the
date of this document (A) Borrower has all requisite authority and power to
execute, deliver, and perform its obligations under this document, which
execution, delivery, and performance have been duly authorized by all necessary
corporate action, require no action by or filing with any Governmental
Authority, do not violate any of its Constituent Documents or (except where not
a Material-Adverse Event) violate any Legal Requirements applicable to it or
any material agreement to which it or its assets are bound, (B) upon execution
and delivery by all parties to it, this document will constitute Borrower's
legal and binding obligation, enforceable against it in accordance with this
document's terms except as that enforceability may be limited by Debtor Laws
and general principles of equity, (C) all other representations and warranties
in the Credit Documents are true and correct in all material respects except to
the extent that (1) any of them speak to a different specific date or (2) the
facts on which any of them were based have been changed by transactions
contemplated or permitted by the Credit Agreement, and (D) no Material-Adverse
Event, Event of Default, or Potential Default exists.

5.       EXPENSES. Borrower shall pay all costs, fees, and expenses paid or
incurred by Agent incident to this document, including, without limitation, the
reasonable fees and expenses of Agent's special counsel in connection with the
negotiation, preparation, delivery, and execution of this document and any
related documents.

6.       MISCELLANEOUS. All references in the Credit Documents to the "Credit
Agreement" refer to the Credit Agreement as amended by this document. This
document is a "Credit Document" referred to in the Credit Agreement; therefore,
the provisions relating to Credit Documents in SECTIONS 1 and 12 are
incorporated in this document by reference. Except as specifically amended and
modified in this document, the Credit Agreement is unchanged and continues in
full force and effect. This document may be executed in any number of
counterparts with the same effect as if all signatories had signed the same
document. All counterparts must be construed together to constitute one and the
same instrument. This document binds and inures to each of the undersigned and
their respective successors and permitted assigns, subject to SECTION 12.10.
THIS DOCUMENT AND THE OTHER CREDIT DOCUMENTS REPRESENT THE FINAL AGREEMENT
BETWEEN THE PARTIES IN RESPECT OF THE MATTERS COVERED BY THE CREDIT DOCUMENTS
AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR
SUBSEQUENT ORAL AGREEMENTS BY THE PARTIES. THERE ARE NO UNWRITTEN ORAL
AGREEMENTS BETWEEN THE PARTIES.

                     REMAINDER OF PAGE INTENTIONALLY BLANK.
                            SIGNATURE PAGE FOLLOWS.


                                       9                        SECOND AMENDMENT
<PAGE>   10

         EXECUTED as of the date first stated in this Second Amendment to
Credit Agreement.

<TABLE>
<CAPTION>
TEPPCO COLORADO, LLC, as Borrower                 SUNTRUST BANK, ATLANTA, as
                                                  Agent and a Lender

<S>                                               <C>
By:  TE PRODUCTS PIPELINE COMPANY,
     LIMITED PARTNERSHIP, as Sole
     Member

                                                  By          /s/ John A. Fields, Jr.
  By:    TEXAS EASTERN PRODUCTS                        ------------------------------------
         PIPELINE COMPANY, as General                  Name:      John A. Fields, Jr.
         Partner                                              -----------------------------
                                                       Title:     Vice President
                                                              -----------------------------

     By  /s/ Charles H. Leonard                   By       /s/ F. McClellan Deaver, III
         -----------------------------------          -------------------------------------
         Charles H. Leonard, Senior Vice              Name:    F. McClellan Deaver, III
                                                              -----------------------------
         President, Chief Financial Officer,          Title:   Group Vice President
         and Treasurer                                        -----------------------------
</TABLE>

                               BANK ONE, TEXAS, N.A., as a Lender


                               By        /s/  Joseph Giampetroni
                                     -----------------------------------
                                     Joseph Giampetroni, Vice President


                             CONSENT AND AGREEMENT

         To induce Required Lenders to enter into this document, the
undersigned (a) consents and agrees to this document's execution and delivery,
(b) ratifies and confirms that the guaranty granted to Agent and Lenders under
the Credit Documents (as it may have been renewed, extended, and amended) is
not released, diminished, impaired, reduced, or otherwise adversely affected by
this document and continues to guarantee, the full payment and performance of
all present and future Obligation, and (c) waives notice of acceptance of this
consent and agreement, which consent and agreement binds the undersigned and
its successors and permitted assigns and inures to Agent and Required Lenders
and their respective successors and permitted assigns.

                                TE PRODUCTS PIPELINE COMPANY, LIMITED
                                PARTNERSHIP, as Guarantor

                                By:     TEXAS EASTERN PRODUCTS PIPELINE
                                        COMPANY, as General Partner

                                        By      /s/ Charles H. Leonard
                                            -----------------------------------
                                            Charles H. Leonard, Senior Vice
                                            President, Chief Financial Officer,
                                            and Treasurer