Document:

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                                                                   EXHIBIT 10.22

                                 AMENDMENT NO. 6

AMENDMENT NO. 6 dated as of August 8, 2002 (this AMENDMENT NO. 6) between: HOLLY
CORPORATION, NAVAJO REFINING COMPANY, L.P., BLACK EAGLE, INC., NAVAJO SOUTHERN,
INC., NAVAJO NORTHERN, INC., LOREFCO, INC., NAVAJO CRUDE OIL PURCHASING, INC.,
NAVAJO HOLDINGS, INC., HOLLY PETROLEUM, INC., NAVAJO PIPELINE CO, L.P., LEA
REFINING COMPANY, NAVAJO WESTERN ASPHALT COMPANY, MONTANA REFINING COMPANY, A
PARTNERSHIP as Borrowers and Guarantors, NAVAJO PIPELINE LP, L.L.C, NAVAJO
PIPELINE GP, L.L.C., NAVAJO REFINING LP, L.L.C., NAVAJO REFINING GP, L.L.C.,
HOLLYCORP AVIATION, L.L.C. and MONTANA RETAIL CORPORATION as Guarantors, the
BANKS listed on the signature pages hereof, CANADIAN IMPERIAL BANK OF COMMERCE,
as Administrative Agent, CIBC INC. as Collateral Agent, FLEET NATIONAL BANK
(formerly known as Bank Boston Corp.), as Documentation Agent, GUARANTY BANK, as
Collateral Monitor, and CIBC WORLD MARKETS CORP, as Sole Lead Arranger and
Bookrunner.

WHEREAS

(A)      The parties hereto are party to an Amended and Restated Credit and
         Reimbursement Agreement dated as of April 14, 2000, as amended by
         Amendment No. 1 dated as of July 7, 2000, Amendment No. 2 dated as of
         April 4, 2001, Amendment No. 3 dated as of August 7, 2001, Amendment
         No. 4 dated as of September 26, 2001 and Amendment No. 5 dated as of
         May 6, 2002 (as in effect on the date hereof, the CREDIT AGREEMENT),
         providing, subject to the terms and conditions thereof, for extensions
         of credit to be made by the Banks to the Borrowers in an aggregate
         principal or face amount not exceeding $100,000,000.

(B)      The Borrowers and the Guarantors wish to amend the Credit Agreement in
         order to extend the maturity date of the credit facility established
         under the Credit Agreement.

(C)      The Bank of Nova Scotia wishes to terminate its Commitments and is
         executing this Amendment No. 6 solely for purposes of obtaining the
         acknowledgement of the Borrowers of such termination and to evidence
         such termination.

(D)      The Banks and Agents agree to amend the Credit Agreement in accordance
         with the provisions contained herein, and accordingly, the parties
         hereto hereby agree as follows:

DEFINITIONS

1. Except as otherwise defined in this Amendment No. 6, terms defined in the
Credit Agreement are used herein as defined therein.

                                                                          Page 1
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AMENDMENTS

2. Subject to the satisfaction of the conditions precedent set forth in Section
4 below, the Credit Agreement shall be amended as follows effective on the date
hereof.

A.       The definition of "Termination Date" in Section 1.1 of the Credit
         Agreement is deleted in its entirety and replaced with the following:

         "TERMINATION DATE means (i) if there is a Satisfactory Resolution in
         respect of the Longhorn Partners Pipeline Litigation prior to October
         10, 2003, October 10, 2004 and (ii) if there is not a Satisfactory
         Resolution in respect of the Longhorn Partners Pipeline Litigation
         prior to October 10, 2003, October 10, 2003 or, if such Termination
         Date is not a Euro-Dollar Business Day, the next preceding Euro-Dollar
         Business Day."

B.       Section 5.8 of the Credit Agreement amended by (i) deleting the
         reference to "$115,000,000" and replacing such reference with
         "$190,000,000", (ii) deleting the phrase "ended after January 31, 2000"
         in clause (ii) thereof and replacing such phrase with the phrase
         "beginning with the quarter ending July 31, 2002" and (iii) deleting
         the reference to "January 31, 2000" in clause (iii) thereof and
         replacing such reference with "July 31, 2002".

C.       Section 5.15 of the Credit Agreement is amended by deleting the
         reference to "$7,000,000" in clause (i) of the second sentence thereof
         and replacing such reference with "$10,000,000".

D.       Each of the lenders that is a signatory hereto identified under the
         caption "BANKS" on the signature pages hereto shall be deemed to be, as
         of the date hereof, a Bank under and for all purposes of the Credit
         Agreement, as amended hereby. The lender which is identified under the
         caption "EXITING BANK" on the signature pages hereto shall, as of the
         date hereof, cease to be a Bank (an EXITING BANK) under and for all
         purposes of the Credit Agreement, as amended hereby, upon payment in
         full by the Borrowers of all Loans, Letters of Credit and all other
         fees, expenses and indemnities owing by the Borrowers to such Bank and
         each Exiting Bank shall have its Commitment reduced to zero and cease
         to have any liabilities or obligations hereunder or under the Credit
         Agreement.

REPRESENTATIONS AND WARRANTIES

3. Each of the Borrowers and the Guarantors represents and warrants to the Banks
and the Agents that (unless specifically limited to an earlier date) the
representations and warranties set forth in Section 4 of the Credit Agreement
are true and complete on and as of the date hereof with the same force and
effect as if made on and as of such date, and as if each reference in said
Section 4 to "this Agreement" included reference to this Amendment No. 6.

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CONDITIONS PRECEDENT

4. As provided in Section 2, the amendments to the Credit Agreement set forth in
said Section 2 shall become effective, as of the date hereof, upon:

         (a)      the receipt of the Administrative Agent of this Amendment No.
                  6, executed by each Borrower and Guarantor, each Agent and the
                  Required Banks;

         (b)      the receipt by each Bank of an amendment fee equal to 0.50% of
                  each Bank's Commitment as of the date hereof;

         (c)      the receipt by the Administrative Agent of a certificate of
                  the Secretary or Assistant Secretary of each Obligor (i)
                  certifying that since April 14, 2001 there have been no
                  changes to the charter and by-laws (or equivalent documents)
                  of such Obligor and (ii) as to all corporate authority (or
                  equivalent authority) for such Obligor (including, without
                  limitation, board of director resolutions and evidence of the
                  incumbency of officers) with respect to the execution,
                  delivery and performance of this Amendment No. 6 and the
                  Credit Agreement as amended hereby and the extensions of
                  credit as amended hereby; and

         (d)      (i) An opinion, dated the date hereof, of Vinson & Elkins
                  L.L.P., special counsel to the Obligors, restating opinions 1,
                  5 and 7 of the opinion delivered by Hughes & Luce, L.L.P. in
                  connection with the original closing of the Credit Agreement
                  (in each case modified to include this Amendment No. 6) and
                  covering such other matters as any Agent or any Bank may
                  reasonably request (and the Company hereby instructs such
                  counsel to deliver such opinion to the Banks and the Agents),
                  and (ii) an opinion, dated the date hereof of the General
                  Counsel of Holly Corporation restating the opinion delivered
                  in connection with the original closing of the Credit
                  Agreement (modified to include this Amendment No. 6) and
                  covering such other matters as any Agent or any Bank may
                  reasonably request (and the Company hereby instructs such
                  General Counsel to deliver such opinion to the Banks and the
                  Agents).

ACKNOWLEDGEMENT OF OBLIGORS

5. Each Obligor hereby (a) agrees that each reference to the Credit Agreement
and words of similar import in each Financing Document to which such Obligor is
party shall be a reference to the Credit Agreement as amended by this Amendment
No. 6 and (b) confirms that its obligations under each Financing Document to
which it is party remain in full force and effect after giving effect to the
amendment of the Credit Agreement by this Amendment No. 6.

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APPOINTMENT OF COLLATERAL MONITOR

6. Pursuant to Section 7.8 of the Credit Agreement, each Bank hereby appoints
Guaranty Bank as Collateral Monitor, and Guaranty Bank hereby accepts such
appointment. Guaranty Business Credit Corporation (the RETIRING AGENT) is hereby
discharged from all its duties and obligations under the Credit Agreement, and
the newly appointed Collateral Monitor shall succeed to and become vested with
all the rights and duties of the Retiring Agent.

MISCELLANEOUS

7. Except as herein provided, the Credit Agreement shall remain unchanged and in
full force and effect This Amendment No. 6 may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
amendatory instrument and any of the parties hereto may execute this Amendment
No. 6 by signing any such counterpart. This Amendment No. 6 shall be governed
by, and construed in accordance with, the law of the State of New York.

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 6 to be
duly executed and delivered as of the day and year first above written.

HOLLY CORPORATION

By: /s/ STEPHEN J. MCDONNELL
    -----------------------------
Name:   Stephen J. McDonnell
Title:  Vice President and Chief Financial Officer

NAVAJO REFINING COMPANY, L.P.
BLACK EAGLE, INC.
NAVAJO SOUTHERN, INC.
NAVAJO NORTHERN, INC.
LOREFCO, INC.
NAVAJO CRUDE OIL PURCHASING, INC.
NAVAJO HOLDINGS, INC.
HOLLY PETROLEUM, INC.
NAVAJO PIPELINE CO., L.P.
LEA REFINING COMPANY
NAVAJO WESTERN ASPHALT COMPANY
NAVAJO PIPELINE GP, L.L.C.
NAVAJO REFINING GP, L.L.C.
HOLLYCORP AVIATION, L.L.C.
MONTANA RETAIL CORPORATION

By: /s/ STEPHEN J. MCDONNELL
    -----------------------------
Name:   Stephen J. McDonnell
Title:  Vice President and Chief Financial Officer

MONTANA REFINING COMPANY, A PARTNERSHIP

By Navajo Northern, Inc., its General Partner

By: /s/ STEPHEN J. MCDONNELL
    -----------------------------
Name:   Stephen J. McDonnell
Title:  Vice President and Chief Financial Officer

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NAVAJO REFINING LP, L.L.C.
NAVAJO PIPELINE LP, L.L.C.

By: /s/ KATHRYN H. WALKER
    -----------------------------
Name:   Kathryn H. Walker
Title:  President

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CANADIAN IMPERIAL BANK OF COMMERCE, as Administrative Agent

By: /s/ MARYBETH ROSS
    -----------------------------
Name:   MARYBETH ROSS
Title:  AUTHORIZED SIGNATORY

                                                                          Page 7
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CIBC INC., as Collateral Agent,

By: /s/ MARYBETH ROSS
    -----------------------------
Name:       MARYBETH ROSS
Title:  AUTHORIZED SIGNATORY

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FLEET NATIONAL BANK, as Documentation Agent

By: /s/ CHRISTOPHER C. HOLMGREN
    -----------------------------
Name:  CHRISTOPHER C. HOLMGREN
Title:  MANANGING DIRECTOR

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GUARANTY BANK, as Collateral Monitor

By: /s/ JIM A. HAMILTON
    -----------------------------
Name:  Jim A. Hamilton
Title: Senior Vice President

                                                                         Page 10
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CIBC WORLD MARKETS CORP., as Sole Lead Arranger and Bookrunner

By: /s/ MARYBETH ROSS
    -----------------------------
Name:      MARYBETH ROSS
Title: AUTHORIZED SIGNATORY

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BANKS

CANADIAN IMPERIAL BANK OP COMMERCE

By: /s/ MARYBETH ROSS
    -----------------------------
Name:      MARYBETH ROSS
Title: AUTHORIZED SIGNATORY

                                                                         Page 12
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FLEET NATIONAL BANK

By: /s/ CHRISTOPHER C. HOLMGREN
    -----------------------------
Name:  CHRISTOPHER C. HOLMGREN
Title:   MANAGING DIRECTOR

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GUARANTY BANK

By: /s/ JIM K. HAMILTON
    -----------------------------
Name:   Jim K. Hamilton
Title:  Senior Vice President

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PNC BANK, NATIONAL ASSOCIATION

By: /s/ DOUG CLARK
    -----------------------------
Name:   Doug Clark
Title:  Vice President

                                                                         Page 15
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HIBERNIA NATIONAL BANK

By: /s/ CORWIN DUPREE
    -----------------------------
Title:  Assistant Vice President

                                                                         Page 16
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EXITING BANK

THE BANK OF NOVA SCOTIA

By:  /s/ NADINE BELL
    ------------------------------
Title: Nadine Bell, Senior Manager

                                                                         Page 17<PAGE>

                AMENDMENT NO. 1 TO OFFICER'S EMPLOYMENT AGREEMENT
                -------------------------------------------------

         This AMENDMENT NO. 1 TO OFFICER'S EMPLOYMENT AGREEMENT (this
"Amendment") effective as of the 1st day of August, 2002, is entered into by and
between H Power Corp., a Delaware corporation (the "Company") and Dudley Castle
Wass II, residing at 9001 Yellow Pine Court, Waxhaw, NC 28173 (hereinafter
referred to as "Executive"). Capitalized terms used and not otherwise defined
herein shall have the meanings ascribed thereto in the Officer's Employment
Agreement (the "Agreement") dated as of June 11, 2001, between the Company and
Executive.

         WHEREAS, the Company and Executive have previously entered into the
Agreement; and

         WHEREAS, in accordance with the provisions of Section 14 of the
Agreement, the Company and Executive desire to amend such agreement.

         NOW, THEREFORE, in consideration of the premises and the covenants and
agreements contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereby
agree as follows:

         1. The first sentence of Section 1 of the Agreement is hereby amended
by deleting the terms "June 11, 2001" and "June 11, 2004" and replacing such
terms with "August 1, 2002" and "July 31, 2003", respectively.

         2. The third paragraph of Section 2 of the Agreement is hereby amended
by deleting the clause "or at such other place or places as the CEO shall
designate,".

         3. Section 4(a) shall be amended by deleting the term "Two Hundred
Thousand Dollars" and the number "200,000" and replacing them with the term "Two
Hundred Fifteen Thousand Dollars" and the number "215,000," respectively.

         4. Section 5(a) shall be amended by adding the following after the last
sentence of the first paragraph thereof:

         "If the Company seeks to terminate this Agreement for "cause," it must
serve written notice upon the Executive which specifically states the grounds
and facts which it claims support its termination and provide Executive with a
thirty-day period in which to substantially cure the conduct. The thirty-day
cure period need not be provided if the "cause" event is such that it is
impossible to cure under any circumstance."

         5. Section 5 shall be amended by adding the following as new Section
5(b) and renumbering the remaining sections as appropriate:

         "For Reasons Other Than Cause. The Company shall have the right to
terminate this Agreement for reasons other than cause by providing thirty days
(30) Notice to Executive. In the event the Executive is terminated for reasons
other than cause, the Company will continue to

<PAGE>

provide benefits and pay the bi-weekly installments of Executive's Base Salary
through the end of the term of employment."

         6. New Section 5(e) shall be amended by deleting the first paragraph in
its entirety and replacing such paragraph with the following:

         "Change in Control. (i) In the event that Executive's employment is
terminated by the Company within one year following a Change in Control (as
defined below) for any reason other than cause, death or disability, or the
Company does not renew the Agreement within the one-year period following a
Change of Control, then the Company shall pay Executive one and one-half his
annual Base Salary at his then current rate and one and one-half the latest
annual incentive compensation payment calculated by taking the highest of the
latest two incentive payments earned and paid multiplied by one and one-half,
such payment to be made in one lump sum payment at the time of termination,
provided that Executive has executed and provided to the Company a general
release in favor of the Company and its affiliates. Such payments shall be in
lieu of any and all other payments due and owing to Executive under the terms of
this Agreement except that the Company shall continue to pay Executive the
automobile allowance for the balance of the term of the Agreement. The Company
shall also provide to the Executive health insurance for a period of one year
following termination of Executive's employment. Executive shall not be required
to seek other employment or to otherwise mitigate the effects of such
termination, and such payments shall not be reduced by any income received from
other sources (all compensation and other benefits described above and the terms
thereof shall hereinafter be referred to collectively as the "Severance
Package"). Executive acknowledges that the Severance Package is specific
consideration for the general release and Executive's obligations under Section
7."

         7. New Section 5(e)(ii)(A) shall be amended by adding the words "change
or" after the word "material" in the first and only sentence thereof.

         8. New Section 5(e)(ii) shall be further amended by deleting the fifth
and final paragraph thereof and replacing it in its entirety with the following:

         "For purposes of this provision, a "Change in Control" shall be deemed
to have occurred if (1) any "person" (as such term is used in Sections 13(d)(3)
and 14(d)(2) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act")), excluding Executive, who is not a shareholder of the Company as of the
date hereof, shall have become the beneficial owner, directly or indirectly, of
Common Stock representing thirty-three and one-third percent (33 1/3%) or more
of the combined voting power of the Company's then outstanding securities,
unless three-quarters of the Board of Directors, as constituted immediately
prior to the date of the Change in Control, decide in their reasonable
discretion that no Change in Control has occurred, Executive not being allowed
to vote on such matter if he is then a Director; provided, however, that if any
such person other than Executive (whether or not a stockholder of the Company as
of the date hereof) shall become the beneficial owner, directly or indirectly,
of Common Stock representing fifty percent (50%) or more of the Company's then
outstanding securities, a Change in Control shall ipso facto have occurred; or
(2) if there is a Change in Control of a nature that, in the opinion of counsel
for the Company, would be required to be reported in response to Item 6(e) of
schedule 14A under the Exchange Act, unless three-quarters of the Board of
Directors, as

                                       -2-
<PAGE>

constituted immediately prior to the date of the Change in Control, decide in
their reasonable discretion that no Change in Control has occurred, Executive
not being allowed to vote on such matter if he is then a Director; or (3) in the
event of a merger in which the Company is a party after which merger the
stockholders of the Company do not retain directly or indirectly at least a
majority of the beneficial interest in the voting stock of the surviving
company; or (4) in the event of the sale, exchange, or transfer of all or
substantially all of the Company's assets. If the provisions of this Section are
in any way involved in litigation or arbitration and Executive incurs legal fees
and expenses or must make a contribution to a judgment or settlement of the
matter, the Company agrees to reimburse him for any and all expenditures."

         9. Section 6 shall be amended by deleting the word "three" and the
number 3 in the first sentence thereof and replacing them with the word "five"
and the number 5, respectively.

         10. This Amendment shall be governed by and construed in accordance
with the laws of the State of Delaware.

         11. This Amendment may not be amended or modified, and no provision
hereof may be waived, without the written consent of the Company and Executive.

         12. This Amendment may be executed in two or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       -3-
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         IN WITNESS WHEREOF, the parties hereto have executed this Amendment No.
1 to Officer's Employment Agreement as of the day and year first above written.

                                     DUDLEY CASTLE WASS II

                                     By: /s/ DUDLEY CASTLE WASS II
                                         ---------------------------------------
                                         Name:
                                         Title:

                                     H POWER CORP.

                                    By: /s/ H. FRANK GIBBARD
                                        ----------------------------------------
                                        Name:
                                        Title:

                                       -4-

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