<PAGE>

                                                                    Exhibit 10.3











              ---------------------------------------------------
                                     PREMCOR
                              WELFARE BENEFIT PLAN
              ---------------------------------------------------












                                                       Effective January 1, 2003

<PAGE>

                                     Premcor
                              Welfare Benefit Plan

                                Table of Contents

                                                                          Page
Article 1 Definitions .......................................................1
     1.1   "Administrator" or "Plan Administrator" ..........................1
     1.2   "Beneficiary" ....................................................1
     1.3   "Benefit" ........................................................1
     1.4   "Code" ...........................................................1
     1.5   "Company" ........................................................1
     1.6   "Dependent" ......................................................1
     1.7   "Effective Date" .................................................1
     1.8   "Eligible Employee" ..............................................2
     1.9   "Insurance Contract" .............................................2
     1.10  "Insured Welfare Benefit Program" ................................2
     1.11  "Named Fiduciary" ................................................2
     1.12  "Participant" ....................................................2
     1.13  "Participating Employer" .........................................2
     1.14  "Plan" ...........................................................2
     1.15  "Plan Year" ......................................................2
     1.16  "Self-Funded Welfare Benefit Program" ............................2
     1.17  "Summary Plan Description" .......................................2
     1.18  "Welfare Benefit Program" ........................................2
Article 2 Eligibility, Participation And Benefits ...........................3
     2.1   Eligibility to Participate in a Welfare Benefit Program ..........3
     2.2   Benefits Under Welfare Benefit Programs ..........................3


==============================================================================
                                      (i)

<PAGE>

Article 3 Funding The Plan ..................................................3
     3.1   Funding Policy ...................................................3
     3.2   Participating Employer Contributions .............................3
     3.3   Contributions by Participants and Other Individuals Eligible for
           Coverage .........................................................3
     3.4   Priority of Contributions and Reserves ...........................3
     3.5   Liability for Benefits ...........................................4
Article 4 Administration ....................................................4
     4.1   The Company's Responsibilities as Employer .......................4
     4.2   The Company's Responsibilities as Plan Administrator .............4
     4.3   General Duties of Plan Administrator .............................4
     4.4   Books and Records ................................................5
     4.5   Fiduciary Capacity ...............................................5
     4.6   Indemnification ..................................................5
     4.7   Uniform Administration ...........................................5
     4.8   Fiduciary Bonds ..................................................6
Article 5 Claims Procedure ..................................................6
     5.1   Provisions Governing Claims Procedures ...........................6
Article 6 Protected Health Information ......................................6
     6.1   Privacy of Participant Health Information ........................6
     6.2   Use and Disclosure of PHI. .......................................6
     6.3   Company Restrictions Regarding PHI ...............................7
     6.4   Safeguards .......................................................7
     6.5   Accounting of Uses or Disclosures ................................7
     6.6   Disclosures to Workforce and/or Third Parties ....................7
     6.7   Access to Records by the Subject of the Records ..................8
     6.8   Government Access to Records .....................................8
     6.9   Disposition of Records When no Longer Needed .....................8


==============================================================================
                                      (ii)

<PAGE>

     6.10  Security Measures Applicable to Electronic PHI. ..................8
Article 7 Amendment And Termination Of The Plan .............................9
     7.1   Discontinuance of Plan or any Welfare Benefit Program ............9
     7.2   Amendment or Termination .........................................9
Article 8 Miscellaneous .....................................................9
     8.1   Adoption of Welfare Benefit Program by Other Participating
           Employers. .......................................................9
     8.2   Lost Distributees ...............................................10
     8.3   No Guarantee of Employment ......................................10
     8.4   Plan Provisions Binding .........................................10
     8.5   Rules of Interpretation .........................................10
     8.6   Choice of Law ...................................................10
     8.7   Severability ....................................................10
     8.8   Facility of Payment .............................................10
     8.9   Recovery of Excess Payments .....................................10


==============================================================================
                                     (iii)

<PAGE>


                                     Premcor
                              Welfare Benefit Plan

     WHEREAS, The Premcor Refining Group Inc. maintains a welfare benefit plan
referred to as the Premcor Welfare Benefit Plan (Plan No. 501) (the "Plan") for
the benefit of employees eligible to participate thereunder; and

     WHEREAS, the Plan consists of various benefit schemes and structures
outlined in applicable Insurance Contracts, Summary Plan Descriptions and other
documents as hereinafter defined; and

     WHEREAS, The Premcor Refining Group Inc. has determined that it is
necessary and desirable to reduce to writing certain provisions governing the
Plan.

     NOW, THEREFORE, The Premcor Refining Group Inc. hereby adopts this written
documentation of provisions that apply to all Welfare Benefit Programs
maintained under the Plan.

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                                    Article 1
                                   Definitions
--------------------------------------------------------------------------------

     When used in this document, the following words shall have the following
meanings unless the context requires otherwise:

1.1 "Administrator" or "Plan Administrator" means the Company or such other
persons as the Company may appoint to administer the Plan or any Welfare Benefit
Program maintained under the Plan.

1.2 "Beneficiary" means any individual or trust identified as a Participant's
Beneficiary pursuant to the provisions of any Welfare Benefit Program maintained
under the Plan.

1.3 "Benefit" means any benefit provided pursuant to any Welfare Benefit
Program.

1.4 "Code" means the Internal Revenue Code of 1986, as amended from time to
time, and the regulations thereunder.

1.5 "Company" means The Premcor Refining Group Inc., a corporation organized and
existing under the laws of the State of Delaware, successor corporation which
assumes the responsibilities of the Company under the Plan.

1.6 "Dependent" means an individual eligible for coverage as a dependent under
any Welfare Benefit Program.

1.7 "Effective Date" means January 1, 2003.

<PAGE>


1.8 "Eligible Employee" means any individual classified by the Company as an
employee or former employee of a Participating Employer who is eligible for
benefits as specified under any Welfare Benefit Program.

1.9 "Insurance Contract" means any contract or agreement pursuant to which any
Welfare Benefit Program is funded, and under which part or all of the direct
obligation to provide Benefits is transferred to an insurance company, preferred
provider organization ("PPO"), health maintenance organization ("HMO") or
similar entity; provided that a contract under which an insurance company is
obligated to make payments to the Company in the event that Benefits payable
under a self-funded plan exceed the amount specified therein, commonly known as
a stop-loss policy, shall not be treated as an Insurance Contract for purposes
of the Plan.

1.10 "Insured Welfare Benefit Program" means a Welfare Benefit Program funded
pursuant to an Insurance Contract.

1.11 "Named Fiduciary" means the Administrator and any other person designated
by the Administrator who has authority to control and manage the operation and
administration of any Welfare Benefit Program, as reflected in the governing
plan document, Insurance Contract or Summary Plan Description. In the case of
any Insured Welfare Benefit Program, the HMO or other carrier under the
Insurance Contract shall be the sole Named Fiduciary for purposes of determining
Benefits payable thereunder, except as otherwise expressly agreed to in writing
by the Company.

1.12 "Participant" means an Eligible Employee who has satisfied the requirements
for participation in any Welfare Benefit Program.

1.13 "Participating Employer" means the Company and any business entity the
employees of which are eligible to participate in any Welfare Benefit Program
pursuant to any Insurance Contract, Summary Plan Description, or other written
instrument duly authorized by the Company.

1.14 "Plan" means the Premcor Welfare Benefit Plan, including the provisions
hereof and all Insurance Contracts, plan documents and Summary Plan Descriptions
pursuant to which Benefits are provided from time to time.

1.15 "Plan Year" means the calendar year.

1.16 "Self-Funded Welfare Benefit Program" means a Welfare Benefit Program
funded through any method other than an Insurance Contract.

1.17 "Summary Plan Description" means the Summary Plan Description provided to
Participants eligible to participate in each Welfare Benefit Program maintained
under the Plan, as amended or otherwise modified from time to time by Summaries
of Material Modifications or other written notices provided to Eligible
Employees who are Participants thereunder.

1.18 "Welfare Benefit Program" means any program maintained under the Plan for
the purpose of providing medical, dental, surgical or hospital care or benefits,
benefits in the event of

                                        2

<PAGE>


sickness, accident, disability, death or unemployment, or vacation benefits,
apprenticeship or other training programs, or daycare centers, scholarship
funds, or any benefit described in section 302(c) of the Labor Management
Relations Act of 1947 (other than pensions on retirement or death, and insurance
to provide such pensions). A Welfare Benefit Program may become a part of the
Plan either before or after execution of this document by reference in the Plan
document or Summary Plan Description for the Welfare Benefit Program to Plan No.
501 or by reference to the Welfare Benefit Program in the annual return report
(Treasury Form 5500 or any successor thereto) which is filed on behalf of the
Plan, without the execution of any other instrument.

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                                   Article 2
                     Eligibility, Participation And Benefits
--------------------------------------------------------------------------------

2.1 Eligibility to Participate in a Welfare Benefit Program. The classifications
of Eligible Employees and Dependents, the age and service requirements for
participation, the requirements for continuation of participation, and the
events giving rise to termination of participation under any Welfare Benefit
Program shall be as provided for in the separate Summary Plan Description or
Insurance Contract governing that Welfare Benefit Program as in effect from time
to time.

2.2 Benefits Under Welfare Benefit Programs. The Benefits furnished under any
Welfare Benefit Program shall be as provided for in the applicable plan
document, Insurance Contract or Summary Plan Description in effect from time to
time.

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                                   Article 3
                                Funding The Plan
--------------------------------------------------------------------------------

3.1 Funding Policy. The Company in its capacity as employer shall establish and
direct the implementation of a policy and method to fund Benefits under the Plan
which shall be consistent with the objectives of the Plan.

3.2 Participating Employer Contributions. The Company and the other
Participating Employers shall make contributions in such amounts and at such
times as the Company shall from time to time determine.

3.3 Contributions by Participants and Other Individuals Eligible for Coverage.
Each Participant or other individual eligible for coverage under any Welfare
Benefit Program shall make such contributions as the Company may require with
respect to Benefits available to the Participant or other individual and his or
her Dependents or Beneficiaries.

3.4 Priority of Contributions and Reserves. Contributions by Participants and
other individuals shall be applied to fund Benefits, insurance premiums,
administrative expenses and other costs of the Plan first, and Participating
Employer contributions shall be required only as to the difference between the
portion of the Benefits, insurance premiums, administrative expenses and other
costs funded through contributions by Participants and other eligible
individuals and the total Benefits, insurance premiums, administrative expenses
and other costs of the Plan. Any reserves or other assets accumulated under the
Plan from time to time pursuant to any Insurance

                                       3

<PAGE>

Contract shall be deemed Participating Employer contributions to the extent that
such reserves or assets do not exceed the Participating Employers' aggregate
contributions during the period in which the reserves or assets are accumulated.

3.5 Liability for Benefits. Benefits funded pursuant to Insurance Contracts
shall be paid solely by the respective carriers thereunder. Benefits payable
under any Self-funded Welfare Benefit Program shall be paid solely from Company
assets.

--------------------------------------------------------------------------------
                                   Article 4
                                 Administration
--------------------------------------------------------------------------------

4.1 The Company's Responsibilities as Employer. The Company in its capacity as
employer shall have overall responsibility for the establishment, amendment and
termination of the Plan. All responsibilities of the Company as employer under
the Plan shall be carried out by the appropriate officer of the Company or such
officer's delegate.

4.2 The Company's Responsibilities as Plan Administrator. The Company in its
capacity as Plan Administrator shall have overall responsibility for
administration and operation of the Plan. Responsibilities of the Plan
Administrator under the Plan shall be carried out by the carriers under any
Insurance Contracts, any third-party administrators appointed by the Company,
the Benefits Department and any special committees or other persons appointed by
the Company from time to time. The Plan Administrator shall administer the Plan
for the exclusive benefit of Participants, Dependents and Beneficiaries.

4.3 General Duties of Plan Administrator. The Plan Administrator shall enforce
the Plan in accordance with the terms of the governing documents, and shall have
all discretionary powers necessary to accomplish that purpose, including without
limitation the following:

          (a) to select and retain insurance carriers, PPOs, HMOs, third-party
     administrators and other persons to carry out any of its responsibilities
     and to delegate such duties to such persons as the Company deems
     appropriate;

          (b) to issue rules and regulations necessary for the proper conduct
     and administration of the Plan and to change, alter or amend such rules and
     regulations;

          (c) to interpret the Plan and determine all questions arising in the
     administration, interpretation and application of the Plan, and to construe
     any ambiguity, supply any omission and reconcile any inconsistency in such
     manner and to such extent as the Administrator deems proper. Any
     interpretation or construction placed upon any term or provision of the
     Plan by the Administrator, any decisions and determinations of the
     Administrator arising under the Plan, including without limiting the
     generality of the foregoing:

               (i) the eligibility of any individual to become or remain a
          Participant, a Participant's status as such and the eligibility of a
          Participant's family members for coverage as Dependents under the
          Plan;

                                       4

<PAGE>

             (ii) the time, method and amount of payment of Benefits payable
         under the Plan;

             (iii) the rights of Participants, Dependents and Beneficiaries; and

             (iv) any other action or determination or decision whatsoever
         taken or made by the Administrator in good faith, shall be conclusive
         and binding upon all persons concerned, including but not limited to
         the Company, all Participating Employers and all Participants,
         Dependents and Beneficiaries.

         (d) to employ such consultants, accountants, attorneys (who may be
    accountants or attorneys for the Company), and other persons to render
    advice and other services in connection with the Plan as it may deem
    necessary to the performance of its duties; and

         (e) to provide Plan Participants with all notices and documents
    required by law.

    In the case of any inconsistency between the provisions of this document
and the provisions of the Insurance Contract under which any Insured Benefit is
provided or the Summary Plan Description under which any Self-funded Benefit is
provided, the provisions of the Insurance Contract or the Summary Plan
Description shall govern.

4.4 Books and Records. The Administrator shall keep such books, records and
other data as it deems necessary for proper administration of the Plan. The
records of the Administrator shall be binding on all persons unless proved
incorrect to the satisfaction of the Administrator.

4.5 Fiduciary Capacity. Any person or group of persons may serve in more than
one capacity as fiduciary or Named Fiduciary.

4.6 Indemnification. To the extent permitted by law, the Participating Employers
shall indemnify and hold harmless any Company employee to whom any fiduciary
responsibility with respect to the Plan is allocated or delegated from and
against any and all liabilities, costs and expenses incurred by any such person
as a result of any act, or omission to act, in connection with the performance
of his or her duties, responsibilities and obligations under the Plan and under
ERISA, other than such liabilities, costs and expenses as may result from the
gross negligence or willful misconduct of any such person. This right of
indemnification shall be in addition to any other right to which such person may
be entitled as a matter of law or otherwise.

4.7 Uniform Administration. Any discretionary acts taken under the Plan by or on
behalf of the Plan Administrator shall be uniform in their nature and shall
apply to all Participants similarly situated, and no discretionary act shall be
taken which is discriminatory under the provisions of the Code or ERISA. All
rules and decisions made by or on behalf of the

                                        5

<PAGE>

Plan Administrator shall be uniformly and consistently applied to all
Participants in similar circumstances.

4.8 Fiduciary Bonds. To the extent required under Section 412 of ERISA or other
applicable law, fidelity bonds covering Plan fiduciaries and other parties
having authority to handle Plan funds shall be obtained under such legal
requirements.

--------------------------------------------------------------------------------
                                   Article 5
                                Claims Procedure
--------------------------------------------------------------------------------

5.1 Provisions Governing Claims Procedures. The claims procedure for each
Insured Welfare Benefit Program shall be governed by the Insurance Contract, or
as provided in the applicable Summary Plan Description. The claims procedure for
each Self-funded Welfare Benefit Program shall be as provided in the applicable
Summary Plan Description.

--------------------------------------------------------------------------------
                                   Article 6
                          Protected Health Information
--------------------------------------------------------------------------------

6.1 Privacy of Participant Health Information. This Article, other than Section
6.10, shall become effective as of April 14, 2003. Section 6.10 shall become
effective as of April 21, 2005. These provisions are intended to satisfy the
Plan document requirements of the privacy and security regulations issued by the
Department of Health and Human Services ("HHS") under the Health Insurance
Portability and Accountability Act of 1996 ("HIPAA"). The Company may obtain
from the Plan (or portions of the Plan which provide medical benefits and for
which HIPAA is applicable) protected health information ("PHI") as defined in
HIPAA. These provisions are not intended to apply to any information which does
not constitute PHI under HIPAA. The Plan will disclose PHI to the Company only
upon receipt of a certification by the Company that this document has been
amended to incorporate the provisions of this Article 6 and that the Company
agrees to all the terms hereof.

6.2 Use and Disclosure of PHI.

         (a) The Company will use and disclose PHI as reasonably appropriate
    and necessary to carry out its duties as Plan Administrator. The Company
    may use or disclosure PHI for any purpose permitted by the HIPAA
    regulations, including but not limited to: (1) obtaining bids or proposals
    from insurers, PPOs, HMOs, third-party payers, or other entities that may
    provide services related to administering the Plan; (2) conducting
    wellness, case management, utilization review, customer service, customer
    satisfaction or any other administrative function in connection with Plan
    operations; (3) reporting expenses and matters to Company management; and
    (4) giving information to the Company's actuaries and other consultants to
    determine future benefit cost to the Company.

         (b) The Company will comply with any law requiring it to disclose PHI,
    including but not limited to a subpoena, court or administrative agency
    warrant or order, a discovery request in a civil proceeding, a summons
    issued by a court, grand jury,

                                        6

<PAGE>

    inspector or administrative body that can require production of information,
    and any requirement of a federal, state or local public health authority.
    Disclosures may be made to report certain injuries or illnesses to public
    authorities, to a health oversight agency for an audit, investigation,
    inspection, license or disciplinary action, and to a law enforcement
    official.

         (c) Further disclosures of PHI are limited to those for which the
    Company obtains reasonable assurances that the PHI will be held
    confidentially and that any breaches of such confidentiality will be
    reported immediately to the Company.

6.3 Company Restrictions Regarding PHI. The Company will not use or disclose PHI
it receives from the Plan for employment-related actions or for a decision in
connection with any other benefit or employee benefit plan of the Company unless
the Company has received a copy of the applicable authorization for this use,
except as permitted by applicable law with respect to worker's compensation.

6.4 Safeguards. The Company will implement appropriate safeguards to prevent the
unauthorized use or disclosure of PHI and will provide the Plan with information
concerning such safeguards as the Plan may from time to time request. Upon
reasonable request, the Company will give the Plan access for inspection and
copying its books, records, practices, policies and procedures concerning the
use and disclosure of PHI, for the purpose of determining the Company's
compliance with this plan provision.

6.5 Accounting of Uses or Disclosures. The Company agrees to notify the Plan
immediately upon discovery of any unauthorized use or disclosure of PHI. The
Company will provide the following information with respect to such use or
disclosure:

         (a)  The date of the use or disclosure;

         (b)  The name and, if known, the address of the recipient of the PHI;

         (c)  A copy of the request for disclosure, including any consents or
     authorizations received;

         (d)  A brief description of the PHI used or disclosed; and

         (e)  A statement that would reasonably inform the Plan of the purpose
     of the use or disclosure.

6.6 Disclosures to Workforce and/or Third Parties . The Company will require its
workforce, agents and subcontractors and other service providers to adhere to
the restrictions and conditions regarding PHI contained herein, as more fully
described in separate policies and procedures.

         (a) Disclosures to workforce: The Company will not disclose PHI to any
    member of its workforce unless the Company has advised such member of the
    Company's obligation under this section and the consequences for violation
    of these obligations. The individuals at the Company who will have access to
    PHI to be used or


                                       7

<PAGE>


          disclosed will be (i) Chief Administrative Officer, (ii) Director of
          Human Resources, (iii) Benefits Manager, (iv) Benefits Administrator,
          (v) Director of Labor Relations, (vi) Human Resources Manager, (vii)
          Human Resources Supervisor, (viii) Human Resources Representative,
          (ix) Human Resources Administrative Assistant, and (x) members of the
          Information Systems Department who perform administrative services for
          the Plan. The access such persons shall have to PHI and the use by
          such persons of PHI shall be for administrative activities performed
          by the Company on behalf of the Plan. If any such person uses or
          discloses PHI in any way which conflicts with the uses described
          herein or permitted by law, such person shall be subject to
          disciplinary action up to and including discharge.

               (b) Disclosures outside of the workforce: The Company will not
          disclose PHI to any other person or entity without the written
          approval of the Plan except as provided in 6.2 above.

               (c) All disclosures. Any use or disclosures of PHI will be
          limited to the minimum necessary to achieve the purpose for the use or
          disclosure. The Company shall adopt policies and procedures to respond
          to requests for PHI, both routine and non-routine, that comply with
          applicable regulations under HIPAA.

6.7 Access to Records by the Subject of the Records. The Company may create and
maintain records of individual medical plan enrollment, disenrollment and
payment and other health information. Such enrollment and other information may
be considered PHI under HIPAA. The Company will make the information available
to such individual or the individual's legal representative for review in
accordance with HIPAA and applicable regulations. If the individual requests
amendment of PHI, and if such request is approved, the Company will incorporate
such amendments and immediately notify the Plan of such request.

6.8 Government Access to Records. The Company will make available its policies,
books and records relating to the use and disclosure of PHI received from the
Plan to HHS for the purpose of determining whether the Plan is in compliance
with HIPAA.

6.9 Disposition of Records When no Longer Needed. The Company agrees to return
or destroy all PHI received from the Plan that the Company maintains in any form
and the Company will retain no copies of such PHI when no longer needed for the
purpose for which disclosure was made. If such return or destruction of records
is not feasible, the Company will continue to extend the protections of this
provision to such PHI and limit any further use of PHI to those purposes that
make the return or destruction of the PHI infeasible.

6.10 Security Measures Applicable to Electronic PHI.

          (a) The Company shall implement administrative, physical and technical
     safeguards that reasonably and appropriately protect the confidentiality,
     integrity and availability of the electronic PHI that it creates, receives,
     maintains or transmits on behalf of the Plan.

                                       8

<PAGE>

          (b) The Company shall implement reasonable and appropriate security
     measures that support the fact that only those individuals at the Company
     listed in Section 6.6(a) are entitled to use and disclose PHI.

          (c) The Company will require its workforce, agents and subcontractors
     and other service providers to adhere to the restrictions and conditions
     regarding electronic PHI contained in this Section 6.10.

          (d) The Company shall report to the Plan any security incident of
     which it becomes aware.

--------------------------------------------------------------------------------
                                   Article 7
                      Amendment And Termination Of The Plan
--------------------------------------------------------------------------------

7.1 Discontinuance of Plan or any Welfare Benefit Program. It is the expectation
of the Company that the Plan will be continued indefinitely, but the Company and
the Participating Employers do not assume continuation of the Plan or payment of
their respective contributions with respect to the Plan or any Welfare Benefit
Program as a contractual obligation. The Company reserves the right at any time
to reduce, suspend or discontinue the Plan or any Welfare Benefit Program.

7.2 Amendment or Termination. The Company may amend, modify, change, revise,
discontinue or terminate the entire Plan or any Welfare Benefit Program
maintained under the Plan from time to time or at any time, without advance
notice thereof, subject to any collective bargaining agreement between a
Participating Employer and a collective bargaining unit.

--------------------------------------------------------------------------------
                                   Article 8
                                  Miscellaneous
--------------------------------------------------------------------------------

8.1 Adoption of Welfare Benefit Program by Other Participating Employers.

          (a) Any business entity related by common ownership to the Company may
     become a Participating Employer under any Welfare Benefit Program with the
     approval of the Company. Any Participating Employer may withdraw from any
     Welfare Benefit Program at any time with the approval of the Company.

          (b) Any Participating Employer that adopts any Welfare Benefit Program
     shall thereby automatically delegate all rights and duties it might
     otherwise reserve to itself under the Plan to the Company, including full
     authority to amend or terminate the Plan or any Welfare Benefit Program. In
     the event of dissolution, merger, consolidation or spin-off involving a
     Participating Employer with respect to any classification of Eligible
     Employees under the Plan as of the date of dissolution, merger,
     consolidation or spin-off, the entity surviving the transaction shall
     succeed to the rights and duties of the Participating Employer under the
     Plan with respect to the classification of Eligible Employees, without the
     execution of any other instrument.

                                       9

<PAGE>


          (c) A Participating Employer shall automatically withdraw from the
     Plan if and when it ceases to be related to the Company by common ownership
     to the extent provided for in section 414(b) or (c) of the Internal Revenue
     Code, unless such Employer's participation is expressly continued in
     accordance with applicable written documents relating to the change in
     ownership.

8.2 Lost Distributees. If any person to whom a check is issued in payment of a
Benefit under a Self-Funded Welfare Benefit Program cannot be located or does
not present the check for payment, the amount of the check may be applied to
other Plan purposes; provided, if any such person subsequently appears and makes
demand for such payment, the Administrator shall direct that such payment be
made in full as soon as practical.

8.3 No Guarantee of Employment. No provision of the Plan shall restrict any
Participating Employer from discharging a Participant from employment or
restrict any Participant from resigning from employment with any Participating
Employer.

8.4 Plan Provisions Binding. The provisions of the Plan, including the Insurance
Contracts for all Insured Welfare Benefit Programs and the Summary Plan
Descriptions and other documents for all Self-funded Welfare Benefit Programs as
in effect from time to time shall be binding upon the Company, all Participating
Employers, all Eligible Employees, all Dependents and all Beneficiaries and
their respective successors, heirs and legal representatives.

8.5 Rules of Interpretation. Words of gender shall include persons and entities
of any gender, the plural shall include the singular, and the singular shall
include the plural. Captions are intended to assist in reference and shall not
be interpreted as part of the Plan.

8.6 Choice of Law. Subject to the applicable provisions of the Employee
Retirement Income Security Act of 1974 which provide to the contrary, this Plan
shall be administered, construed and enforced according to the laws of State of
Missouri or such other State as may be provided for in an Insurance Contract
with respect to matters governed thereby, and in any case, shall be subject to
the jurisdiction of Courts situated in Missouri or such other state.

8.7 Severability. The invalidity of any particular clause, provision or covenant
herein or in any Insurance Contract or Summary Plan Description shall not
invalidate all or any part of the remainder of the Plan, but such remainder
shall be and remain valid in all respects as fully as the law will permit.

8.8 Facility of Payment. If the Plan Administrator deems any person incapable of
receiving payments by reason of minority, illness, infirmity or other
incapacity, it may direct payment directly for the benefit of such person, or to
any person selected by the Plan Administrator to disburse it. Such payment, to
the extent thereof, shall discharge all liability for such payment under the
Plan. Any payment made in accordance with this Section shall fully release the
Plan of its liabilities with respect to the Participant, Dependent or
Beneficiary.

8.9 Recovery of Excess Payments. In the event payments are made in excess of the
amount necessary to satisfy the applicable provision of the Welfare Benefit
Program, the Plan shall have the right to recover excess payments from any
individual, insurance company or other

                                       10

<PAGE>

organization to whom excess payments are made. The Plan shall also have the
right to withhold payment of future benefits due until the overpayment is
recovered.

                                       11

<PAGE>

     IN WITNESS WHEREOF, the Company has executed this instrument this 11th day
of April, 2003, effective as of January 1, 2003.

                                       THE PREMCOR REFINING GROUP INC.

                                       By /s/ James R. Voss
                                          --------------------------------------
                                          James R. Voss,
                                          Senior Vice-President

                                       12