<PAGE>   1
                       FIRST AMENDMENT TO CREDIT AGREEMENT


         THIS DOCUMENT is entered into as of July 28, 1998, but is effective as
of June 29, 1998, between TEPPCO COLORADO, LLC, a Delaware limited liability
company ("Borrower"), the Lenders named below, 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, 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, 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)   The words "90 days" in Section 6.1(f) are amended to read "150
days".

         (B)   The table in Section 8.1 and Table 2 in Exhibit C are entirely
amended as follows:
<TABLE>
<CAPTION>
============================= =============
     Quarter(s) Ending           Ratio
============================= =============
<S>                           <C>        
06/30/98 through 03/31/99     0.70 to 1.00
06/30/99 through 12/31/99     0.67 to 1.00
03/31/00 and thereafter       0.65 to 1.00
============================= =============
</TABLE>

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, 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 (E) 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 

                                                                 First Amendment

<PAGE>   2

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.

                                                                 First Amendment
                                      

<PAGE>   3



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

<TABLE>
<S>                                           <C>            
TEPPCO COLORADO, LLC, as Borrower              SUNTRUST BANK, ATLANTA, as   
                                               Agent and a Lender           
By: TE Products Pipeline Company, Limited                
    Partnership, as Sole Member
                                               By   /s/ JOHN A. FIELDS                     
    By: Texas Eastern Products Pipeline             -----------------------------------
        Company, as General Partner                 John A. Fields, Jr., Vice President
                                                         
        By  /s/ CHARLES H. LEONARD   
            -----------------------
            Charles H. Leonard,                 By  /s/ STEVEN J. NEWBY             
            Senior Vice President,                  -----------------------------------
            Chief Financial Officer,                Name:    Steven J. Newby          
            and Treasurer                                 -----------------------------
                                                    Title:   Corporate Banking Officer
                                                          -----------------------------
                                               

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


                                         By   /s/ GARY STONE
                                              -----------------------------------------
                                              Gary Stone, Senior Vice President
</TABLE>

                              CONSENT AND AGREEMENT

         To induce Lender 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 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