<PAGE>

                                FOURTH AMENDMENT

         THIS FOURTH AMENDMENT dated as of March 16, 2001 (this "Amendment")
amends the Second Amended and Restated Credit Agreement dated as of February
3, 1999 (as previously amended, the "Credit Agreement") among U S Liquids
Inc. (the "Company"), various financial institutions (the "Banks"), Fleet
National Bank, as Syndication Agent, and Bank of America, N.A. (formerly
known as Bank of America National Trust and Savings Association), as
administrative agent (in such capacity, the "Administrative Agent"). Terms
defined in the Credit Agreement are, unless otherwise defined herein or the
context otherwise requires, used herein as defined therein.

         WHEREAS, the Company, the Banks and the Administrative Agent have
entered into the Credit Agreement; and

         WHEREAS, the parties hereto desire to amend the Credit Agreement in
certain respects as more fully set forth herein;

         NOW, THEREFORE, the parties hereto agree as follows:

         SECTION 1 AMENDMENTS REQUIRING THE CONSENT OF THE REQUIRED BANKS.
Subject to the satisfaction of the conditions precedent set forth in SECTION
5(a), the Credit Agreement shall be amended as follows.

         1.1 DELETION OF DEFINITIONS. The definitions of "Shreveport Facility
Reserve Charges" and "Third Quarter Special Charges" are deleted in their
entirety.

         1.2 ADDITION OF DEFINITIONS. The following definitions are added to
the Credit Agreement in appropriate alphabetical sequence:

             ADJUSTED EBITDA means, for any Computation Period, the total of (i)
         EBITDA for such Computation Period plus (ii) any Fourth Quarter Special
         Charges taken during such Computation Period plus (iii) any Detroit
         Facility Reserve Charges taken during such Computation Period minus
         (iv) any non-cash income during such Computation Period resulting from
         the Settlement Agreement dated December 21, 2000 between the Company
         and Waste Management, Inc.

             ADJUSTED WORKING CAPITAL means, at any time, the excess of:

             (a) (i) the consolidated current assets of the Company and its
         Subsidiaries (other than deferred taxes and assets held for sale as
         shown on the most recent financial statements delivered by the Company
         pursuant to SECTION 10.1) LESS (ii)

<PAGE>

         the amount of cash and cash equivalents included in such consolidated
         current assets;

         OVER

             (b) (i) the consolidated current liabilities of the Company and its
         Subsidiaries LESS (ii) to the extent included in such consolidated
         current liabilities, the sum of (x) all short-term Debt of the Company
         and its Subsidiaries and (y) any portion of long-term Debt of the
         Company and its Subsidiaries which is payable within one year from the
         date of determination.

             ASSET SALE means the sale, lease, assignment or other transfer for
         value by the Company or any Subsidiary to any Person (other than the
         Company or any Subsidiary) of any asset or right of the Company or such
         Subsidiary (including any sale or other transfer of stock of any
         Subsidiary, whether by merger, consolidation or otherwise, but
         excluding any sale of assets or rights in the ordinary course of
         business).

             AVAILABILITY AMOUNT means the Commitment Amount minus $5,000,000
         (or minus such lesser amount as the Required Banks, in their sole and
         complete discretion, may specify in writing to the Company).

                  EXCESS CASH FLOW means, for any period, the remainder of

             (a) EBITDA for such period (excluding any portion of EBITDA
         attributable to any settlement with National Steel, Inc. for such
         period),

             LESS

             (b) the total, without duplication of

             (i) regularly scheduled principal payments made with respect to any
         long-term Debt of the Company and its Subsidiaries (other than the
         Loans) during such period,

             PLUS

             (ii) cash payments made in such period with respect to Capital
         Expenditures,

             PLUS

                                       2
<PAGE>

             (iii) all federal, state, local and foreign income taxes paid by
         the Company and its Subsidiaries during such period,

             PLUS

             (iv) cash Interest Expense of the Company and its Subsidiaries
         during such period,

             PLUS

             (v) any increase in Adjusted Working Capital during such period,

             MINUS

             (vi) any decrease in Adjusted Working Capital during such period.

             FOURTH QUARTER SPECIAL CHARGES means the up to $35,970,000 of
         special charges taken by the Company for the fourth Fiscal Quarter of
         2000.

             NET CASH PROCEEDS means:

             (a) with respect to any Asset Sale, the aggregate cash proceeds
         (including cash proceeds received by way of deferred payment of
         principal pursuant to a note, installment receivable or otherwise, but
         only as and when available to the Company) received by the Company or
         any Subsidiary pursuant to such Asset Sale, net of (i) the direct costs
         relating to such Asset Sale (including sales commissions, legal,
         accounting and investment banking fees and severance payments for
         discharged employees), (ii) taxes paid or reasonably estimated by the
         Company to be payable as a result thereof (after taking into account
         any available tax credits or deductions and any tax sharing
         arrangements), and (iii) amounts required to be applied to the
         repayment of any Debt secured by a Lien on the asset subject to such
         Asset Sale (other than Debt hereunder);

             (b) with respect to any issuance of equity securities, the
         aggregate cash proceeds received by the Company or any Subsidiary
         pursuant to such issuance, net of the direct costs relating to such
         issuance (including sales and underwriter's discounts and commissions
         and legal, accounting and investment banking fees); and

             (c) with respect to any settlement with National Steel, Inc., the
         aggregate proceeds received by the Company pursuant to such agreement,
         net of (i) the direct costs relating to the execution of such agreement
         (including legal


                                       3
<PAGE>


         fees) and (ii) taxes paid or reasonably estimated by the Company to be
         payable as a result thereof (after taking into account any available
         tax credits or deductions and any tax sharing arrangements).

             SPECIFIED PROPERTY means, as the context requires, (i) the property
         in Los Fresnos, Texas owned by U S Liquids of Central Texas, L.L.C. or
         (ii) the Allison Grease plant and the Re-Claim plant in Houston, Texas
         owned by U S Liquids of Houston, L.L.C.

         1.3 AMENDMENTS TO DEFINITIONS. (a) The definition of "Commitment
Amount" is amended by deleting the reference to "$150,000,000" therein and
substituting "$120,000,000" therefor.

         (b) The definition of "EBITDA" is amended by deleting the proviso at
the end thereof.

         (c) The definition of "Interest Expense" is amended by deleting the
proviso at the end thereof.

         (d) The definitions of "Funded Debt to EBITDA Ratio," "Interest
Coverage Ratio" and "Recoveries" are amended in their entirety to read as
follows, respectively:

             FUNDED DEBT TO ADJUSTED EBITDA RATIO means, at any time, the ratio
         of (a) Funded Debt at such time to (b) Adjusted EBITDA for the
         Computation Period ending on the last day of the most recent Fiscal
         Quarter with respect to which the Company has delivered financial
         statements.

             INTEREST COVERAGE RATIO means, for any Computation Period, the
         ratio of (a) Adjusted EBITDA to (b) cash Interest Expense for such
         Computation Period.

             RECOVERIES means, without duplication, (i) any amounts (including
         insurance proceeds and proceeds from any judgment or settlement)
         received by the Company or any Subsidiary arising out of any matter
         which gave rise to any Detroit Facility Reserve Charges and (ii) any
         reversal of any reserve established in connection with any Detroit
         Facility Reserve Charges.

         1.4 AMENDMENT TO SECTION 2.1.1. Section 2.1.1 is amended by deleting
the reference to "Commitment Amount" therein and substituting "Availability
Amount" therefor.

         1.5 AMENDMENT TO SECTION 2.1.2. Section 2.1.2 is amended by deleting
the reference to "Commitment Amount" therein and substituting "Availability
Amount" therefor.


                                       4
<PAGE>

         1.6 DELETION OF SECTION 2.1.3. Section 2.1.3 is deleted in its
entirety.

         1.7 AMENDMENT TO SECTION 2.4.1. Section 2.4.1 is amended by (a)
deleting the reference to "$15,000,000" therein and substituting "$5,000,000"
therefor and (b) deleting the reference to "Commitment Amount" therein and
substituting "Availability Amount" therefor.

         1.8 AMENDMENT TO SECTION 4.3. Section 4.3 is amended by (a) deleting
the second reference to "Commitment Amount" contained in the last sentence of
that Section and substituting "Availability Amount" therefor and (b) deleting
the reference to "SECTION 6.1.2" therein and substituting "SECTION 6.1(b)".

         1.9 AMENDMENTS TO SECTION 6.1. Section 6.1 is amended as set forth
below.

         (a) The caption "(a) VOLUNTARY REDUCTION OR TERMINATION OF THE
COMMITMENTS." is inserted at the beginning of such Section.

         (b) The following new subsections (b)(i) through (b)(iv) are inserted
at the end thereof:

             (b) MANDATORY REDUCTIONS OF THE COMMITMENTS. (i) The Commitment
         Amount shall be permanently reduced by (A) $5,000,000 on each of July
         31, 2001 and December 31, 2001 and (B) $2,500,000 on the last day of
         each Fiscal Quarter thereafter.

             (ii) Concurrently with the receipt by the Company or any Subsidiary
         of any Net Cash Proceeds from any Asset Sale, issuance of equity (other
         than any equity issued in connection with the employee stock purchase
         plan of the Company), issuance of Debt (other than Debt permitted under
         SECTION 10.7(a), (b), (c), (d), (e), (g) or (h)) or any settlement with
         National Steel, Inc., the Commitment Amount shall be permanently
         reduced by an amount (rounded down, if necessary, to an integral
         multiple of $100,000) equal to (A) so long as (and to the extent that)
         the Commitment Amount has not previously or concurrently been reduced
         by $10,000,000 after the effective date of the Fourth Amendment to this
         Agreement, 100% of such Net Cash Proceeds; and (B) thereafter, (x) 100%
         of all Net Cash Proceeds from any Asset Sale and (y) 50% of all other
         such Net Cash Proceeds; PROVIDED that the requirements of this CLAUSE
         (ii) shall not apply to any Net Cash Proceeds from any Asset Sale that
         are used to purchase similar assets within 60 days after such Asset
         Sale. All reductions of the Commitment Amount pursuant to CLAUSE (A) of
         the preceding sentence shall be applied to reduce the remaining
         scheduled reductions of the Commitment Amount pursuant to SUBSECTION
         (b) above in chronological order. All reductions of the Commitment
         Amount pursuant to CLAUSE (B) of the second preceding sentence


                                       5
<PAGE>

         shall be applied to reduce the Commitment Amount without reducing any
         scheduled reduction of the Commitment Amount pursuant to CLAUSE (B).

             (iii) Concurrently with the delivery of the compliance certificate
         as of the end of any Fiscal Year pursuant to SECTION 10.1.3, beginning
         with the Fiscal Year ending December 31, 2001, the Commitment Amount
         shall be permanently reduced by an amount (rounded down, if necessary,
         to an integral multiple of $100,000) equal to 100% of Excess Cash Flow
         for such Fiscal Year.

             (iv) Any reduction of the Commitment Amount pursuant to CLAUSES (i)
         through (iii) above shall reduce the Commitments pro rata among the
         Banks according to their respective Percentages.

         1.10 AMENDMENT TO SECTION 6.2. Section 6.2 is amended by (a) inserting
the caption "(a) VOLUNTARY PREPAYMENTS." at the beginning of such Section, (b)
deleting the last two sentences of the existing Section 6.2 and (c) inserting
the following new subsections (b) and (c) at the end thereof:

             (b) MANDATORY PREPAYMENTS. On each date on which the Commitment
         Amount is reduced pursuant to SECTION 6.1, the Company shall prepay
         Loans in the amount, if any, by which the Total Outstandings exceed the
         Availability Amount after giving effect to such reduction.

             (c) ALL PREPAYMENTS. Each partial prepayment shall be in a
         principal amount of $100,000 or a higher integral multiple thereof. Any
         prepayment of a Eurodollar Loan on a day other than the last day of an
         Interest Period therefor shall include interest on the principal amount
         being repaid and shall be subject to SECTION 8.4.

         1.11 AMENDMENT TO SECTION 9.5. Section 9.5 is amended by deleting the
reference to "December 31, 1997" therein and substituting "December 31, 2000"
therefor.

         1.12 AMENDMENT TO SECTION 10.6.1. Section 10.6.1 is amended by (a)
deleting the reference to "$100,000,000" and substituting "$148,400,000"
therefor, (b) deleting the reference to "October 1, 1998" and substituting
"December 31, 2000" therefor and (c) deleting the reference to "the Effective
Date" and substituting "December 31, 2000" therefor.

         1.13 AMENDMENT TO SECTION 10.6.2. Section 10.6.2 is amended in its
entirety to read as follows:


                                       6
<PAGE>

             10.6.2 MINIMUM INTEREST COVERAGE. Not permit the Interest Coverage
         Ratio for any Computation Period to be less than the applicable ratio
         set forth below:

<TABLE>
<CAPTION>
                           Computation                        Interest
                           Period Ending                     Coverage Ratio
                           -------------                     --------------
<S>                                                          <C>
                  12/31/00 through 6/30/01                    2.25 to 1.0
                  7/1/01 through 9/30/01                      2.50 to 1.0
                  10/1/01 and thereafter                      3.00 to 1.0.
</TABLE>

         1.14 AMENDMENT TO SECTION 10.6.3. Section 10.6.3 is amended in its
entirety to read as follows:

             10.6.3 FUNDED DEBT TO ADJUSTED EBITDA RATIO. Not permit the Funded
         Debt to Adjusted EBITDA Ratio during any period set forth below to
         exceed the applicable ratio set forth below:

<TABLE>
<CAPTION>
                                                           Funded Debt
                           Period                    to Adjusted EBITDA Ratio
                           ------                    ------------------------
<S>                                                  <C>
                  12/31/00 through 6/29/01                4.50 to 1.0
                  6/30/01 through 9/29/01                 4.25 to 1.0
                  9/30/01 through 12/30/01                3.75 to 1.0
                  12/31/01 and thereafter                 3.00 to 1.0.
</TABLE>

         1.15 AMENDMENT TO SECTION 10.6.4. Section 10.6.4 is amended in its
entirety to read as follows:

             10.6.4 CAPITAL EXPENDITURES. Not permit the aggregate amount of
         Capital Expenditures (excluding amounts, if any, paid to consummate
         acquisitions permitted by SECTION 10.11(c) which constitute Capital
         Expenditures) made by the Company and its Subsidiaries to exceed (a)
         $6,000,000 during the first two Fiscal Quarters of any Fiscal Year
         ending after December 31, 2000 or (b) $10,000,000 during any Fiscal
         Year ending after December 31, 2000.

         1.16 AMENDMENT TO SECTION 10.7. Section 10.7 is amended as follows:

         (a) Subsection (b) is amended by deleting the reference to
"$10,000,000" therein and substituting "$5,000,000" therefor.


                                       7
<PAGE>

         (b) Subsection (c) is amended by deleting the reference to
"$20,000,000" therein and substituting "$5,000,000" therefor.

         1.17 AMENDMENT TO SECTION 10.9. Section 10.9 is amended by deleting the
reference to "$9,000,000" therein and substituting "$6,000,000" therefor.


         1.18 AMENDMENT TO SECTION 10.11. Section 10.11 is amended as follows:

         (a) Subsection (c) is amended in its entirety to read as follows:

             (c) any such other purchase or acquisition by the Company or any
         Subsidiary of the assets or stock of any other Person made with the
         prior written consent of all Banks;

         (b) Subsection (d) is amended in its entirety to read as follows:

             (d) sales and dispositions of assets (including the stock of
         Subsidiaries) so long as the net book value of all assets sold or
         otherwise disposed of in any Fiscal Year (excluding the stock or assets
         of the entities listed on SCHEDULE 10.9(d) and any Specified Property)
         does not exceed $500,000.

         1.19 AMENDMENT TO SECTION 10.23. Section 10.23 is amended by (a)
deleting the reference to "$300,000" therein and substituting "$1,500,000"
therefor and (b) deleting the reference to "fair market value" therein and
substituting "net book value" therefor.

         1.20 AMENDMENT TO SECTION 10.24. Section 10.24 is amended by (a)
deleting the reference to "$300,000" therein and substituting "$1,500,000"
therefor and (b) deleting the reference to "fair market value" therein and
substituting "net book value" therefor.

         1.21 ADDITION OF SECTION 10.26. A new Section 10.26 is added to the
Credit Agreement to read as follows:

             10.26 MINIMUM CUMULATIVE EBITDA. Not permit cumulative EBITDA for
         any period beginning on January 1, 2001 and ending on the last day of
         any month thereafter to be less the applicable amount set forth below:

<TABLE>
<CAPTION>
                      Period Ending                    Cumulative EBITDA
                      -------------                    -----------------
<S>                                                    <C>
                  January 31, 2001                     $1,572,292
                  February 28, 2001                    $3,853,461
                  March 31, 2001                       $6,704,909
                  April 30, 2001                       $9,285,012

                                       8
<PAGE>

                  May 31, 2001                         $12,164,383
                  June 30, 2001                        $15,721,004
                  July 31, 2001                        $19,000,514
                  August 31, 2001                      $22,423,370
                  September 30, 2001                   $25,971,274
                  October 31, 2001                     $29,241,373
                  November 30, 2001                    $32,203,966
                  December 31, 2001                    $34,842,397;
</TABLE>

         PROVIDED that, for any period after the sale by the Company of any of
         the Subsidiaries listed on SCHEDULE 10.9(d) or the Specified Property
         located in Los Fresnos, Texas, there shall be subtracted from the
         amounts set forth above the projected EBITDA for such Subsidiary (or
         the relevant assets of such Subsidiary) set forth on SCHEDULE 10.26 for
         each month from the month in which such sale occurs.

         1.22 AMENDMENT TO SCHEDULES 1.1, 9.6, 9.8 AND 9.15. Each of Schedules
1.1, 9.6, 9.8 and 9.15 is amended in its entirety to read as set forth on
SCHEDULE 1.1, SCHEDULE 9.6, SCHEDULE 9.8 and SCHEDULE 9.15 hereto, respectively.

         1.23 AMENDMENT TO EXHIBIT B. Exhibit B is amended in its entirety to
read as set forth on EXHIBIT B hereto.

         1.24 ADDITION OF SCHEDULES 10.9(d) AND 10.26. New Schedules 10.9(d) and
10.26 are added to the Credit Agreement to read as set forth on SCHEDULE 10.9(d)
and SCHEDULE 10.26 hereto, respectively.

         SECTION 2 AMENDMENT REQUIRING THE CONSENT OF EACH BANK. Subject to the
satisfaction of the conditions precedent set forth in SECTION 5(b), the
definition of "Termination Date" set forth in Section 1.1 is amended in its
entirety to read as follows:

             TERMINATION DATE means the earlier to occur of (a) December 2,
         2002; PROVIDED that, without in any way affecting the rights of the
         Agent and the Banks under SECTION 12.2, if any Event of Default occurs
         after March 16, 2001 and on or prior to September 2, 2002, the
         scheduled Termination Date shall, upon notice by the Required Banks to
         the Agent, be rescheduled to be the later of February 1, 2002 or the
         90th day after the occurrence of such Event of Default; and (b) such
         other date on which the Commitments shall terminate pursuant to SECTION
         6 or SECTION 12.

         SECTION 3 WAIVERS. Subject to the satisfaction of the conditions
precedent set forth in SECTION 5(a), the Required Banks hereby waive (a) the
Company's non-compliance with


                                       9
<PAGE>

Sections 10.6.1, 10.6.2, 10.6.3, 10.23 and 10.24 of the Credit Agreement for all
periods ended on or prior to December 31, 2000 and (b) the Company's
non-compliance with Section 12.1.11(c) of the Credit Agreement resulting from
the resignation of W. Gregory Orr.

         SECTION 4 REPRESENTATIONS AND WARRANTIES. The Company represents and
warrants to the Administrative Agent and the Banks that, after giving effect to
the effectiveness hereof, (a) each warranty set forth in Section 9 (excluding
Section 9.14 with respect to Re-Claim Louisiana L.L.C. and Waste Research and
Recovery, Inc.) of the Credit Agreement is true and correct as of the date of
the execution and delivery of this Amendment by the Company, with the same
effect as if made on such date, and (b) no Event of Default or Unmatured Event
of Default exists.

         SECTION 5 EFFECTIVENESS. (a) The amendments set forth in SECTION 1
above shall become effective when the Administrative Agent shall have received
(i) counterparts of this Amendment executed by the Company and the Required
Banks, (ii) a Confirmation, substantially in the form of EXHIBIT A, signed by
the Company and each Subsidiary, and (iii) an amendment fee for each Bank which,
on or before March 16, 2001, executes and delivers to the Administrative Agent a
counterpart hereof agreeing to the amendments set forth in SECTION 1, such fee
to be in an amount equal to 0.25% of such Bank's Commitment after giving effect
to the amendment in SECTION 1.3(a).

         (b) The amendment set forth in SECTION 2 shall become effective when
the Administrative Agent shall have received (i) counterparts of this Amendment
executed by the Company and each Bank and (ii) an extension fee in the amount of
$300,000 (to be shared among the Banks pro rata according to their respective
Commitments after giving effect to the amendment in SECTION 1.3(a)).

         (c) Any Bank may, in its discretion, agree to the amendments set forth
in SECTION 1 but not the amendments (and extension) set forth in SECTION 2 by
delivering to the Administrative Agent, concurrently with its delivery of its
signature pages hereto, a notice in the form of ANNEX 1 hereto.

         SECTION 6 MISCELLANEOUS.

         6.1 CONTINUING EFFECTIVENESS, ETC. As herein amended, the Credit
Agreement shall remain in full force and effect and is hereby ratified and
confirmed in all respects. After the effectiveness of this Amendment, all
references in the Credit Agreement and the other Loan Documents to "Credit
Agreement" or similar terms shall refer to the Credit Agreement as amended
hereby.

         6.2 COUNTERPARTS. This Amendment may be executed in any number of
counterparts and by the different parties on separate counterparts, and each
such counterpart shall be deemed to be an original but all such counterparts
shall together constitute one and the same Amendment.


                                       10
<PAGE>

         6.3 GOVERNING LAW. This Amendment shall be a contract made under and
governed by the laws of the State of Illinois applicable to contracts made and
to be performed entirely within such state.

         6.4 SUCCESSORS AND ASSIGNS. This Amendment shall be binding upon the
Company, the Banks and the Administrative Agent and their respective successors
and assigns, and shall inure to the benefit of the Company, the Banks and the
Administrative Agent and the respective successors and assigns of the Banks and
the Administrative Agent.

         6.5 FACILITY FEE. The Company agrees to pay a facility fee to the
Administrative Agent in an amount equal to 0.25% of the Commitment Amount on the
applicable date (to be shared among the Banks pro rata according to their
respective Commitments) (i) on February 1, 2002 if the Company has not received
a commitment letter from a financial institution to refinance the Credit
Agreement on or prior to January 31, 2002 or (ii) on March 15, 2002 if (x) the
Loans have not been paid in full and the Commitments terminated on or prior to
such date and (y) no facility fee has previously been paid by the Company
pursuant to CLAUSE (i).

         6.6 CONSENT TO SALES. Notwithstanding any provision of Section 10.11 of
the Credit Agreement to the contrary, the Required Banks hereby agree that the
Company may sell all of the stock or all or a portion of the assets of any of
the Subsidiaries listed on SCHEDULE 10.9(d) and any Specified Property so long
as the Net Cash Proceeds from any such sale are at least equal to the net book
value of such Subsidiary or assets, as applicable.


                                       11
<PAGE>

         Delivered at Chicago, Illinois, as of the day and year first above
written.

                                       U S LIQUIDS INC.


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       BANK OF AMERICA, N.A., as Administrative
                                       Agent


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       BANK OF AMERICA, N.A., as a Bank


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       FLEET NATIONAL BANK, as Syndication Agent
                                       and as a Bank


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       BANK ONE TEXAS, N.A.


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       S-1
<PAGE>


                                       THE BANK OF NOVA SCOTIA


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       UNION BANK OF CALIFORNIA


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       COMERICA BANK


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       WELLS FARGO BANK, N.A.


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       BNP PARIBAS


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       By
                                          -----------------------------------
                                       Title
                                             --------------------------------


                                       S-2
<PAGE>

                                                                       EXHIBIT A


                                  CONFIRMATION

                           Dated as of March 16, 2001

To: Bank of America, N.A., individually and as Agent, and the other financial
    institutions party to the Credit Agreement referred to below

         Please refer to (a) the Second Amended and Restated Credit Agreement
dated as of February 3, 1999 (as amended, the "Credit Agreement") among U S
Liquids Inc., various financial institutions (the "Banks") and Bank of
America, N.A., as agent (the "Agent"); (b) the other "Loan Documents" (as
defined in the Credit Agreement), including the Guaranty and the Security
Agreement; and (c) the Fourth Amendment dated as of March 16, 2001 to the
Credit Agreement (the "Fourth Amendment").

         Each of the undersigned hereby confirms to the Agent and the Banks
that, after giving effect to the Fourth Amendment and the transactions
contemplated thereby, each Loan Document to which such undersigned is a party
continues in full force and effect and is the legal, valid and binding
obligation of such undersigned, enforceable against such undersigned in
accordance with its terms.

                      U S LIQUIDS INC.
                                              By:___________________________
                      Name Printed:_________________
                      Title:________________________

                      DOMBROWSKI & HOLMES, INC.
                      EARTH BLENDS, INC.
                      MBO, INC.
                      THE NATIONAL SOLVENT EXCHANGE CORP.
                      NORTHERN A-1 SANITATION SERVICES, INC.
                      PARALLEL PRODUCTS OF FLORIDA, INC.
                      PARALLEL PRODUCTS OF KENTUCKY, INC.
                      RE-CLAIM ENVIRONMENTAL LOUISIANA,      L.L.C.
                      ROMIC ENVIRONMENTAL TECHNOLOGIES
                         CORPORATION
                      STA DECANTING, INC.
                      USL FIRST SOURCE, INC.
                      U S LIQUIDS OF HOUSTON, L.L.C.
                      U S LIQUIDS OF DALLAS, L.L.C.
                      U S LIQUIDS OF CENTRAL TEXAS, L.L.C.
                      U S LIQUIDS OF CONNECTICUT, INC.


                                       A-1
<PAGE>

                      U S LIQUIDS OF ILLINOIS, INC.
                      U S LIQUIDS OF PENNSYLVANIA, INC.
                      U S LIQUIDS OF TEXAS, INC.
                      U S LIQUIDS LP HOLDING CO.
                      U S LIQUIDS NORTHEAST, INC.
                      U S LIQUIDS TERMINAL SERVICES, INC.
                      U S LIQUIDS OF DETROIT, INC.
                      U S LIQUIDS OF FLORIDA, INC.
                      USL ENVIRONMENTAL SERVICES, INC.
                      USL GENERAL MANAGEMENT, INC.
                      USL PARALLEL PRODUCTS OF CALIFORNIA
                      WASTE RESEARCH AND RECOVERY, INC.
                      WASTE STREAM ENVIRONMENTAL, INC.


                      By:
                          -----------------------------------------------------
                      Name:
                            ---------------------------------------------------
                      Title:
                             --------------------------------------------------


                      U S LIQUIDS OF LA, L.P.

                      By:  MBO, Inc., its General Partner

                      By:
                          -----------------------------------------------------
                      Name:
                            ---------------------------------------------------
                      Title:
                            ---------------------------------------------------


                      USL MANAGEMENT LIMITED
                      PARTNERSHIP

                      By:  USL General Management, Inc., its General Partner

                      By:
                         ------------------------------------------------------
                      Name:
                           ----------------------------------------------------
                      Title:
                            ---------------------------------------------------

                      GEM MANAGEMENT, INC.

                      By:
                         ------------------------------------------------------
                      Name:
                           ----------------------------------------------------
                      Title:
                            ---------------------------------------------------


<PAGE>


                                  SCHEDULE 1.1

                                PRICING SCHEDULE

         The Floating Rate Margin, the Eurodollar Margin, the rate per annum for
non-use fees and the rate per annum for letter of credit fees for Financial
Letters of Credit and Non-Financial Letters of Credit, respectively, shall be
determined in accordance with the table below and the other provisions of this
SCHEDULE 1.1.

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------
                                 Level I         Level II         Level III         Level IV          Level V
--------------------------------------------------------------------------------------------------------------
<S>                            <C>            <C>               <C>              <C>               <C>
Rate for
Non-Use Fee                      0.550%           0.500%            0.450%           0.400%           0.350%
--------------------------------------------------------------------------------------------------------------
Eurodollar Margin                3.750%           3.500%            3.250%           3.000%           2.750%
--------------------------------------------------------------------------------------------------------------
Floating Rate
Margin                           2.250%           2.000%            1.750%           1.500%           1.250%
--------------------------------------------------------------------------------------------------------------
Rate for
Non-Financial LC                 2.250%           2.125%            2.000%           1.875%           1.750%
Fee
--------------------------------------------------------------------------------------------------------------
Rate for
Financial LC Fee                 3.750%           3.500%            3.250%           3.000%           2.750%
--------------------------------------------------------------------------------------------------------------
</TABLE>

         LEVEL I applies when the ratio of Funded Debt to Adjusted EBITDA is
equal to or greater than 4.00 to 1.0.

         LEVEL II applies when the ratio of Funded Debt to Adjusted EBITDA is
equal to or greater than 3.50 to 1.0 but less than 4.00 to 1.0.

         LEVEL III applies when the ratio of Funded Debt to Adjusted EBITDA is
equal to or greater than 3.00 to 1.0 but less than 3.50 to 1.0.

         LEVEL IV applies when the ratio of Funded Debt to Adjusted EBITDA is
equal to or greater than 2.50 to 1.0 but less than 3.00 to 1.0.

         LEVEL V applies when the ratio of Funded Debt to Adjusted EBITDA is
less than 2.50 to 1.0.

         The applicable Level shall be Level I during the period from the date
of the effectiveness of the Fourth Amendment to this Agreement through the first
date on which the applicable Level is adjusted pursuant to the following
sentence. Subject to the foregoing provisions of this SCHEDULE 1.1, the
applicable Level shall be adjusted, to the extent applicable, 45 days (or, in
the

<PAGE>

case of the last Fiscal Quarter of any Fiscal Year, 90 days) after the end of
each Fiscal Quarter based on the Funded Debt to Adjusted EBITDA Ratio as of
the last day of such Fiscal Quarter; PROVIDED that if the Company fails to
deliver the financial statements required by SECTION 10.1.1 or 10.1.2, as
applicable, and the related certificate required by SECTION 10.1.3 by the
45th day (or, if applicable, the 90th day) after any Fiscal Quarter, Level I
shall apply until such financial statements are delivered.

<PAGE>

                                 SCHEDULE 9.6(a)

                      LITIGATION AND CONTINGENT LIABILITIES


                  REDACTED - CONFIDENTIAL TREATMENT REQUESTED.


<PAGE>

                                 SCHEDULE 9.6(b)



                  REDACTED - CONFIDENTIAL TREATMENT REQUESTED.


<PAGE>

                                  SCHEDULE 9.8
                                  SUBSIDIARIES


Dombrowski & Holmes, Inc.
Earth Blends, Inc.
MBO, Inc.
The National Solvent Exchange Corp.
Northern A-1 Sanitation Services, Inc.
Parallel Products of Florida, Inc.
Parallel Products of Kentucky, Inc.
Re-Claim Environmental Louisiana, L.L.C.
Romic Environmental Technologies Corporation
STA Decanting, Inc.
U S Liquids of Houston, L.L.C.
U S Liquids of Dallas, L.L.C.
U S Liquids of Central Texas, L.L.C.
U S Liquids of Connecticut, Inc.
U S Liquids of Illinois, Inc.
U S Liquids of Pennsylvania, Inc.
U S Liquids of Texas, Inc.
U S Liquids LP Holding Co.
U S Liquids Northeast, Inc.
U S Liquids Terminal Services, Inc.
U S Liquids of Detroit, Inc.
U S Liquids of Florida, Inc.
USL Environmental Services, Inc.
USL First Source, Inc.
USL General Management, Inc.
USL Parallel Products of California
Waste Research and Recovery, Inc.
Waste Stream Environmental, Inc.
U S Liquids of LA, L.P.
USL Management Limited Partnership
GEM Management, Inc.


<PAGE>

                                  SCHEDULE 9.15
                              ENVIRONMENTAL MATTERS


                  REDACTED - CONFIDENTIAL TREATMENT REQUESTED.


<PAGE>

                                Schedule 10.9(d)

                              ASSETS HELD FOR SALE


                  REDACTED - CONFIDENTIAL TREATMENT REQUESTED.


<PAGE>

                                 SCHEDULE 10.26

                    PROJECTED EBITDA FOR VARIOUS SUBSIDIARIES


                  REDACTED - CONFIDENTIAL TREATMENT REQUESTED.


<PAGE>
                                                                       EXHIBIT B

                                U S LIQUIDS INC.
                        FINANCIAL COMPLIANCE CERTIFICATE
             FOR PERIOD ENDED _____________ (the "COMPUTATION DATE")


To:   Bank of America, N.A., as Agent

         Reference is made to Section 10.1.3 of the Second Amended and Restated
Credit Agreement dated as of February 3, 1999 (as amended or otherwise modified
from time to time, the "CREDIT AGREEMENT") among U S Liquids Inc. (the
"COMPANY"), various financial institutions and Bank of America, N.A. (formerly
known as Bank of America National Trust and Savings Association), as Agent for
the Banks. Capitalized terms used but not otherwise defined herein are used as
defined in the Credit Agreement.

         The Company hereby certifies and warrants to you that the computations
of the various financial ratios and restrictions set forth in Section 10 of the
Credit Agreement are as set forth on Schedule A.

         The Company further certifies to you that no Event of Default or
Unmatured Event of Default has occurred and is continuing.

         IN WITNESS WHEREOF, the Company has caused this Certificate to be
executed and delivered by its duly authorized officer this ____ day of
_________, ____.


                                         U S LIQUIDS INC.


                                         By_________________________
                                         Title______________________

<PAGE>

                                   Schedule A
                        Financial Ratios and Restrictions

<TABLE>
<S>                                                             <C>                      <C>
VII.    MINIMUM NET WORTH (Section 10.6.1)

A.    Initial Minimum Net Worth:                                 $148,400,000
B.    75% of the sum of Consolidated Net Income
      for each Fiscal Quarter (which shall not be
      less than zero) from and after December 31,
      2000 to the Computation Date                               $__________
C.    100% of net proceeds of any equity issued by
      the Company or any of its Subsidiaries after
      December 31, 2000                                          $__________
D.    Actual Net Worth                                                                     $_____________
E.    Minimum Required Net Worth (IA+ IB+IC)                                               $_____________

II.   MINIMUM INTEREST COVERAGE (Section 10.6.2)

A.    Consolidated Net Income                                    $__________
B.    Interest Expense                                           $__________
C.    Income tax expense                                         $__________
D.    Depreciation and Amortization                              $__________
E.    EBITDA (IIA+IIB+IIC+IID)                                   $__________
F.    Fourth Quarter Special Charges                             $__________
G.    Detroit Facility Reserve Charges                           $__________
H.    Non-cash income resulting from Waste
      Management Settlement Agreement                            $__________
I.    Adjusted EBITDA (IIE+IIF+IIG-IIH)                                                    $__________
J.    Cash Interest Expense                                                                $__________
K.    Interest Coverage Ratio (III/IIJ)                                                    ____ to 1.0


<PAGE>

Minimum Required:

COMPUTATION PERIOD ENDING
12/31/00 through 6/30/01                                                                   2.25 to 1.0
7/1/01 through 9/30/01                                                                     2.50 to 1.0
10/1/01 and thereafter                                                                     3.00 to 1.0

III.  FUNDED DEBT TO ADJUSTED EBITDA RATIO (Section 10.6.3)

A.    Funded Debt                                                                          $__________
B.    Adjusted EBITDA (III above)                                                          $__________
C.    Funded Debt to Adjusted EBITDA Ratio                                                 ____ to 1.0
      (IIIA/IIIB)

Maximum Allowed:

PERIOD ENDING
12/31/00 through 6/29/01                                                                   4.50 to 1.0
6/30/01 through 9/29/01                                                                    4.25 to 1.0
9/30/01 through 12/30/01                                                                   3.75 to 1.0
12/31/01 and thereafter                                                                    3.00 to 1.0

IV. CAPITAL EXPENDITURES (Section 10.6.4)

A.    Aggregate Capital Expenditures made since
      the first day of current Fiscal Year (maximum              $___________
      $10,000,000 in any Fiscal Year)
B.    Aggregate Capital Expenditures made during
      the first two Fiscal Quarters of current Fiscal
      Year (maximum $6,000,000 in the first two                  $____________
      Fiscal Quarters of any Fiscal Year)

V.    DEBT (Section 10.7)

A.    Unsecured Debt of Company (maximum
      $5,000,000 in aggregate principal amount at
      any time)                                                  $____________
B.    Debt secured by Liens permitted by Sections
      10.8(c) or (d) (maximum $5,000,000 in
      aggregate principal amount at any time)                    $____________


<PAGE>

C.    Contingent Payments (maximum
      $10,000,000 at any time)

VI.   OPERATING LEASES (Section 10.9)

Aggregate amount of all rental payments made by Company and Subsidiaries on
Operating Leases with a term greater than three months (maximum $6,000,000 on a
consolidated basis in any Fiscal
Year)                                                            $____________


VII.  INVESTMENTS (Section 10.21)

A.    Loans to officers and employees (not to                    [Describe]
      exceed $200,000 per loan or $500,000 in the
      aggregate)
B.    Aggregate amount of Investments described
      in Section 10.21(j)                                        $___________

VIII. PROPERTY AT ETHANOL PLANT SITE (Section 10.23)

Net book value of property of the Company and its
Subsidiaries located at the Ethanol Plant Site (not
to exceed $1,500,000)                                            $___________

IX.   PROPERTY OWNED BY PARALLEL PRODUCTS OF FLORIDA (Section 10.24)

Net book value of property owned by Parallel
Products of Florida, Inc. (not to exceed
$1,500,000)                                                      $___________
</TABLE>

<PAGE>

                                     ANNEX I

                                     NOTICE

To:  Bank of America, N.A.

         Please refer to the Fourth Amendment dated as of March 16, 2001 (the
"Fourth Amendment") to the Second Amended and Restated Credit Agreement dated
as of February 3, 1999 among U S Liquids Inc., various financial institutions
and Bank of America, N.A., as Agent. Terms defined in the Fourth Amendment
are used herein as defined therein.

         Concurrently herewith, the undersigned is delivering to the Agent a
counterpart signature page to the Fourth Amendment. The undersigned hereby
notifies the Agent and the Company that such counterpart signature page is
being delivered subject to the qualification that the undersigned has not
agreed to Section 2 of the Fourth Amendment or to the extension of the
Termination Date referred to therein.



                                   ------------------------------------------
                                   [Type or print name of Bank]

                                   By:_______________________________________
                                   Title: ___________________________________