QuickLinks -- Click here to rapidly navigate through this document

EXHIBIT 10.1

AMENDED AND RESTATED
CREDIT AGREEMENT

Originally dated as of May 20, 2002 and Amended by First Amendment
dated as of March 28, 2003
and as amended and restated as of December 1, 2003

among

MARKWEST ENERGY OPERATING COMPANY, L.L.C.,
as the Borrower,

MARKWEST ENERGY PARTNERS, L.P.,
as a Guarantor

ROYAL BANK OF CANADA
as Administrative Agent

BANK ONE, NA
as Syndication Agent

FORTIS CAPITAL CORP.
as Documentation Agent

and

The Lenders Party Hereto

$140,000,000

SENIOR CREDIT FACILITY

RBC CAPITAL MARKETS
and
BANC ONE CAPITAL MARKETS, INC.
As Arrangers

Dated as of December 1, 2003

--------------------------------------------------------------------------------

TABLE OF CONTENTS

 
   
   
  Page

--------------------------------------------------------------------------------

ARTICLE I.   1     DEFINITIONS AND ACCOUNTING TERMS   1     1.01   Defined Terms
  1     1.02   Other Interpretive Provisions   20     1.03   Accounting Terms  
20     1.04   Rounding   20     1.05   References to Agreements and Laws   20
ARTICLE II.
 
21     THE COMMITMENTS AND BORROWINGS   21     2.01   Loans   21     2.02  
Intentionally Omitted   21     2.03   Borrowings, Conversions and Continuations
of Loans   21     2.04   Prepayments   22     2.05   Reduction or Termination of
Commitments   23     2.06   Repayment of Loans   23     2.07   Interest   24    
2.08   Fees   24     2.09   Computation of Interest and Fees   24     2.10  
Evidence of Debt   25     2.11   Payments Generally   25     2.12   Sharing of
Payments   27     2.13   Priority of Hedging Obligations and Banking Service
Obligations   28     2.14   Letters of Credit   28
ARTICLE III
 
34     TAXES, YIELD PROTECTION AND ILLEGALITY   34     3.01   Taxes   34    
3.02   Illegality   34     3.03   Inability to Determine Rates   35     3.04  
Increased Cost and Reduced Return; Capital Adequacy; Reserves on Eurodollar Rate
Loans   35     3.05   Funding Losses   36     3.06   Matters Applicable to all
Requests for Compensation   36     3.07   Survival   36
ARTICLE IV.
 
37     CONDITIONS PRECEDENT TO BORROWINGS   37     4.01   Intentionally Omitted
  37     4.02   Conditions Precedent to Amendment and Restatement of Agreement  
37     4.03   Conditions to all Loans and L/C Credit Extension   39     4.04  
Conditions Precedent to Funding Loans for Shell Pipeline Acquisition   40    
4.05   Conditions Precedent to Funding Loans for Acquisitions   42              

i

--------------------------------------------------------------------------------

ARTICLE V.
 
43     REPRESENTATIONS AND WARRANTIES   43     5.01   Existence; Qualification
and Power; Compliance with Laws   43     5.02   Authorization; No Contravention
  43     5.03   Governmental Authorization   43     5.04   Binding Effect   43  
  5.05   Financial Statements; No Material Adverse Effect   43     5.06  
Litigation   44     5.07   No Default   44     5.08   Ownership of Property;
Liens   44     5.09   Environmental Compliance   44     5.10   Insurance   44  
  5.11   Taxes   44     5.12   ERISA Compliance   44     5.13   Subsidiaries and
other Investments   45     5.14   Margin Regulations; Investment Company Act;
Public Utility Holding Company Act; Use of Proceeds   45     5.15   Disclosure  
45     5.16   Labor Matters   46     5.17   Compliance with Laws   46     5.18  
Third Party Approvals   46     5.19   Solvency   46     5.20   Collateral   46
ARTICLE VI.
 
47     AFFIRMATIVE COVENANTS   47     6.01   Financial Statements   47     6.02
  Certificates; Other Information   47     6.03   Notices   48     6.04  
Payment of Obligations   48     6.05   Preservation of Existence, Etc.   48    
6.06   Maintenance of Assets and Business   49     6.07   Maintenance of
Insurance   49     6.08   Compliance with Laws and Contractual Obligations   50
    6.09   Books and Records   50     6.10   Inspection Rights   50     6.11  
Compliance with ERISA   50     6.12   Use of Proceeds   50     6.13   Material
Agreements   51     6.14   Intentionally Omitted   51     6.15   Guaranties   51
    6.16   Further Assurances; Additional Collateral   51              

ii

--------------------------------------------------------------------------------

ARTICLE VII.
 
53     NEGATIVE COVENANTS   53     7.01   Liens   53     7.02   Investments   54
    7.03   Hedging Agreements   54     7.04   Indebtedness   54     7.05   Lease
Obligations   55     7.06   Fundamental Changes   55     7.07   Dispositions  
55     7.08   Restricted Payments; Distributions and Redemptions   56     7.09  
ERISA   56     7.10   Nature of Business; Capital Expenditures; Risk Management
  56     7.11   Transactions with Affiliates   56     7.12   Burdensome
Agreements   57     7.13   Use of Proceeds   57     7.14   Material Agreements  
57     7.15   Financial Covenants   57     7.16   Subordinated Indebtedness   58
    7.17   Counterparty Consents   58
ARTICLE VIII.
 
59     EVENTS OF DEFAULT AND REMEDIES   59     8.01   Events of Default   59    
8.02   Remedies Upon Event of Default   61
ARTICLE IX.
 
62     ADMINISTRATIVE AGENT   62     9.01   Appointment and Authorization of
Agents; Lender Hedging Agreements   62     9.02   Delegation of Duties   62    
9.03   Default; Collateral   62     9.04   Liability of Agents   64     9.05  
Reliance by Administrative Agent   64     9.06   Notice of Default   65     9.07
  Credit Decision; Disclosure of Information by Administrative Agent   65    
9.08   Indemnification of Agents   65     9.09   Administrative Agent in its
Individual Capacity   66     9.10   Successor Administrative Agent   66     9.11
  Syndication Agent; Other Agents; Arrangers   66              

iii

--------------------------------------------------------------------------------

ARTICLE X.
 
67     MISCELLANEOUS   67     10.01   Amendments, Release of Collateral, Etc  
67     10.02   Notices and Other Communications; Facsimile Copies   68     10.03
  No Waiver; Cumulative Remedies   69     10.04   Attorney Costs; Expenses and
Taxes   69     10.05   Indemnification   70     10.06   Payments Set Aside   71
    10.07   Successors and Assigns   71     10.08   Confidentiality   73    
10.09   Set-off   74     10.10   Interest Rate Limitation   74     10.11  
Counterparts   74     10.12   Integration   74     10.16   Governing Law   76  
  10.17   Waiver of Right to Trial by Jury, Etc   76     10.18   Security
Interest In Parent Pledge Agreement   77     10.19   No General Partner's
Liability   77     10.20   Termination of Commitments Under Original Credit
Agreement   77     10.22   ENTIRE AGREEMENT   77

SCHEDULES

2.01   Commitments 5.13   Subsidiaries and other Equity Investments 7.01  
Existing Liens 7.12   Agreements Restricting Liens on Leasehold Interests 10.02
  Addresses for Notices to Borrower, Guarantors and Administrative Agent

EXHIBITS

Exhibit:

--------------------------------------------------------------------------------

  Form of:

--------------------------------------------------------------------------------

A-1   Borrowing Notice A-2   Conversion/Continuation Notice B   Note C  
Compliance Certificate pursuant to Section 6.02(a) D   Assignment and Assumption
E   Subsidiary Guaranty F-1   Legal Opinion of Hogan & Hartson L.L.P. F-2  
Legal Opinion of Hall, Estill, Hardwick, Gable, Golden & Nelson, P.C. G  
Subsidiary Pledge and Security Agreement H   MarkWest Parent Pledge Agreement

iv

--------------------------------------------------------------------------------

AMENDED AND RESTATED CREDIT AGREEMENT

Originally dated as of May 20, 2002 and Amended by First Amendment
dated as of March 28, 2003
and as amended and restated as of December 1, 2003

        THIS AMENDED AND RESTATED CREDIT AGREEMENT ("Agreement") is entered into
as of December 1, 2003, among MARKWEST ENERGY OPERATING COMPANY, L.L.C., a
Delaware limited liability company (the "Borrower"), MARKWEST ENERGY PARTNERS,
L.P., a Delaware limited partnership (the "MLP"), each lender from time to time
party hereto (collectively, the "Lenders" and individually, "Lender"), ROYAL
BANK OF CANADA, as Administrative Agent, and BANK ONE, NA, a national banking
association with its headquarters in Chicago, Illinois, as Syndication Agent.

PRELIMINARY STATEMENTS

        (1)   The Borrower, the MLP, Bank of America, N.A., individually and as
initial administrative agent ("Bank of America"), Fortis Capital Corp.
("Fortis"), Wells Fargo Bank, N.A. ("Wells Fargo"), U.S. Bank, National
Association ("US Bank"), Bank of Oklahoma, N.A. ("Bank of Oklahoma") and Royal
Bank of Canada ("Royal Bank"; Bank of America, Fortis, Wells Fargo, US Bank,
Bank of Oklahoma and Royal Bank collectively called the "Original Lenders")
entered into a Credit Agreement originally dated May 20, 2002, as amended by a
First Amendment to Credit Agreement among the Borrower, the MLP and the Original
Lenders (with Royal Bank succeeding Bank of America as administrative agent)
dated March 28, 2003 (as amended, the "Original Credit Agreement").

        (2)   Pursuant to the provisions of Section 10.07 of the Original Credit
Agreement, each of Bank of America, Fortis, Wells Fargo, US Bank and Bank of
Oklahoma have assigned all of their rights and obligations under the Original
Credit Agreement (including all of their respective commitments and loans and
participations in letters of credit thereunder) to Royal Bank (and Royal Bank,
as administrative agent under the Original Credit Agreement, hereby waives the
$3,500 processing and recordation fee for each such assignment) and Royal Bank,
as administrative agent under the Original Credit Agreement, has accepted and
recorded such assignments and the Borrower has also consented to such
assignment.

        (3)   Concurrent with such assignments, Royal Bank has assigned to Bank
One, NA ("Bank One"), a 50% interest in the commitments and loans and letters of
credit outstanding under the Original Credit Agreement and contemporaneously
with such assignment to Bank One, the Borrower, the MLP, Royal Bank and Bank One
have agreed to amend and restate in its entirety the Original Credit Agreement
on the terms and conditions set forth herein.

        NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained, the parties hereto hereby agree that the Original Credit
Agreement is amended and restated in its entirety to read as follows:

ARTICLE I.
DEFINITIONS AND ACCOUNTING TERMS

        1.01    Defined Terms.    

        As used in this Agreement, the terms defined in the introductory
paragraph hereof and in the preliminary statements hereto shall have the
meanings therein indicated and the following terms shall have the meanings set
forth below:

        Acquisition means any transaction or series of related transactions for
the purpose of, or resulting in, directly or indirectly, (a) the acquisition by
a Company of all or substantially all of the assets located

1

--------------------------------------------------------------------------------

in the United States or Canada of a Person or of any business or division of a
Person; (b) the acquisition by a Company of more than 50% of any class of Voting
Stock (or similar ownership interests) of any Domestic Person; or (c) a merger,
consolidation, amalgamation, or other combination by a Company with another
Person if a Company is the surviving entity, provided that, (i) in any merger
involving the Borrower, the Borrower must be the surviving entity; and (ii) in
any merger involving a Wholly-Owned Subsidiary and another Subsidiary, a
Wholly-Owned Subsidiary shall be the survivor.

        Administrative Agent means Royal Bank of Canada in its capacity as
administrative agent under any of the Loan Documents, or any successor
administrative agent.

        Administrative Agent's Office means the Administrative Agent's address
and, as appropriate, account as set forth on Schedule 10.02, or such other
address or account as the Administrative Agent may from time to time notify to
the Borrower and the Lenders.

        Administrative Details Form means the Administrative Details Reply Form
furnished by a Lender to the Administrative Agent in connection with this
Agreement.

        Affiliate means, as to any Person, any other Person directly or
indirectly controlling, controlled by, or under direct or indirect common
control with, such Person. A Person shall be deemed to be controlled by any
other Person if such other Person possesses, directly or indirectly, power
(a) to vote 10% or more of the securities (on a fully diluted basis) having
ordinary voting power for the election of directors, managing members, or
managing general partners; or (b) to direct or cause the direction of the
management and policies of such Person whether by contract or otherwise.

        Agent/Arranger Fee Letter has the meaning specified in Section 2.08(b)

        Agents means collectively the Administrative Agent and the Syndication
Agent and Agent individually means either of them.

        Agent-Related Persons means the Administrative Agent (including any
successor administrative agent), the Syndication Agent (including any successor
syndication agent) and their respective Affiliates (including the officers,
directors, employees, agents and attorneys-in-fact of such Persons).

        Aggregate Commitments has the meaning set forth in the definition of
"Commitment" and as of the date of the Restatement is $140,000,000.

        Agreement means this Credit Agreement.

        Applicable Rate means the following percentages per annum set forth in
the table below, on any date of determination, with respect to the Type of
Credit Extension or commitment fee that corresponds to the Leverage Ratio at
such date of determination, as calculated based on the quarterly Compliance
Certificate most recently delivered pursuant to Section 6.02(a):

Applicable Rate

--------------------------------------------------------------------------------

Pricing Level

--------------------------------------------------------------------------------

  Leverage Ratio

--------------------------------------------------------------------------------

  Commitment
Fee (bps)

--------------------------------------------------------------------------------

  Letter of Credit
and Eurodollar
Rate + (bps)

--------------------------------------------------------------------------------

  Base Rate + (bps)

--------------------------------------------------------------------------------

1   Less than or equal to 2.00:1.00   37.5   200.0   62.5 2   Greater than
2.00:1.00 but less than or equal to 2.50:1.00   37.5   225.0   87.5 3   Greater
than 2.50:1.00 but less than or equal to 3.00:1.00   50.0   250.0   112.5 4  
Greater than 3.00:1.00 but less than or equal to 3.50:1.00   50.0   275.0  
137.5 5   Greater than 3.50:1.00   50.0   350.0   212.5

2

--------------------------------------------------------------------------------

        Any increase or decrease in the Applicable Rate resulting from a change
in the Leverage Ratio shall become effective as of the first day of the fiscal
quarter of the Borrower immediately following the date of a Compliance
Certificate delivered pursuant to Section 6.02; provided, however,that if no
Compliance Certificate is delivered during a fiscal quarter when due in
accordance with such Section, the Pricing Level 5 shall apply as of the first
day of such following fiscal quarter; provided further within a reasonable
period after the MLP Offering the Borrower may submit an interim Compliance
Certificate and the Applicable Rate for the next Fiscal Quarter following
delivery of such interim Compliance Certificate shall be based upon the Leverage
Ratio reflected in such interim Compliance Certificate. The Applicable Rate in
effect from the Restatement Date through March 31, 2004 shall be based upon
Pricing Level 5.

        American Central Acquisition means the acquisition by MW Western of gas
gathering, pipeline and processing plant assets located in the State of Oklahoma
from American Central Western Oklahoma Gas Company, L.L.C.

        Approved Fund means any Fund that is administered or managed by a
Lender, an Affiliate of a Lender, or an entity or an Affiliate of an entity that
administers or manages a Lender.

        Arrangers means collectively RBC Capital Markets and Banc One Capital
Markets, Inc. in their capacity as joint lead arrangers and book runners.

        Assignment and Assumption means an Assignment and Assumption
substantially in the form of Exhibit D.

        Attorney Costs means and includes the fees and disbursements of any law
firm or other external counsel and the allocated cost of internal legal services
and all disbursements of internal counsel.

        Attributable Indebtedness means, on any date, (a) in respect of any
Capital Lease of any Person, the capitalized amount thereof that would appear on
a balance sheet of such Person prepared as of such date in accordance with GAAP,
and (b) in respect of any Synthetic Lease Obligation, the capitalized amount of
the remaining lease payments under the relevant lease that would appear on a
balance sheet of such Person prepared as of such date in accordance with GAAP if
such lease were accounted for as a capital lease.

        Authorizations means all filings, recordings, and registrations with,
and all validations or exemptions, approvals, orders, authorizations, consents,
franchises, licenses, certificates, and permits from, any Governmental
Authority.

        Bank Guaranties means guaranties or other agreements or instruments
serving a similar function issued by a bank or other financial institution.

        Banking Services means each and any of the following bank services
provided to any Loan Party by any Lender or Affiliate of a Lender:
(i) commercial credit cards, (ii) stored value cards, and (iii) treasury
management services (including, without limitation, controlled disbursement,
automated clearinghouse transactions, return items, overdrafts and interstate
depository network services).

        Banking Service Obligations means any and all obligations of the Loan
Parties, whether absolute or contingent and howsoever created, arising,
evidenced or acquired (including all renewals, extensions and modifications
thereof and substitutions therefor) in connection with Banking Services.

        Base Rate means for any day a fluctuating rate per annum equal to the
higher of (a) the Federal Funds Rate plus 1/2 of 1% and (b) the rate of interest
in effect for such day as publicly announced from time to time by the
Administrative Agent as its "prime rate." Such rate is a rate set by the
Administrative Agent based upon various factors including the Administrative
Agent's costs and desired return, general economic conditions and other factors,
and is used as a reference point for pricing some loans, which may be priced at,
above, or below such announced rate. Any change in such rate

3

--------------------------------------------------------------------------------

announced by the Administrative Agent shall take effect at the opening of
business on the day specified in the public announcement of such change.

        Base Rate Loan means a Loan that bears interest based on the Base Rate.

        Blackhawk Pipeline means that certain natural gas pipeline in Hutchinson
County, Texas, approximately five (5) miles in length, connected and
transporting gas to the electrical generation plant owned by Borger Energy
Associates, LP, known as Blackhawk Station, from the El Paso Pipeline northeast
of Borger, Texas.

        Board means the Board of Governors of the Federal Reserve System of the
United States cf America.

        Borrower Affiliate means the Borrower, the General Partner, the MLP, and
each of their respective Subsidiaries.

        Borrowing means a borrowing consisting of simultaneous Loans of the same
Type and having the same Interest Period made by each of the Lenders pursuant to
Section 2.01.

        Borrowing Notice means a notice of (a) a Borrowing, (b) a conversion of
Loans from one Type to the other, or (c) a continuation of Loans as the same
Type, pursuant to Section 2.03(a), which, if in writing, shall be substantially
in the form of Exhibit A-1 or A-2, as applicable.

        Business Day means any day other than a Saturday, Sunday, or other day
on which commercial banks are authorized to close under the Laws of, or are in
fact closed in, the state where the Administrative Agent's Office is located
and, if such day relates to any Eurodollar Rate Loan, means any such day on
which dealings in Dollar deposits are conducted by and between banks in the
applicable offshore Dollar interbank market.

        Capital Expenditure by a Person means an expenditure (determined in
accordance with GAAP) for any fixed asset owned by such Person for use in the
operations of such Person having a useful life of more than one year, or any
improvements or additions thereto.

        Capital Lease means any capital lease or sublease which should be
capitalized on a balance sheet in accordance with GAAP.

        Cash Collateralize means to pledge and deposit with or deliver to the
Administrative Agent, for the benefit of the L/C Issuer and the Lenders, as
collateral for the L/C Obligations, cash and deposit account balances pursuant
to documentation in form and substance satisfactory to the Administrative Agent
and the L/C Issuer (which documents hereby are consented to by the Lenders).

        Cash Equivalents means:

        (a)   United States Dollars;

        (b)   direct general obligations, or obligations of, or obligations
fully and unconditionally guaranteed as to the timely payment of principal and
interest by, the United States or any agency or instrumentality thereof having
remaining maturities of not more than thirteen (13) months, but excluding any
such securities whose terms do not provide for payment of a fixed dollar amount
upon maturity or call for redemptions;

        (c)   certificates of deposit and eurodollar- time deposits with
maturities of thirteen (13) months or less, bankers acceptances with maturities
not exceeding one hundred eighty (180) days, overnight bank deposits and other
similar short term instruments, in each case with any domestic commercial bank
having capital and surplus in excess of $250,000,000 and having a rating of at
least "A2" by Moody's and at least "A" by S&P;

4

--------------------------------------------------------------------------------

        (d)   repurchase obligations with a term of not more than thirteen
(13) months for underlying securities of the types described in (b) and
(c) above entered into with any financial institution meeting the qualifications
in (c) above;

        (e)   commercial paper (having original maturities of not more than two
hundred seventy (270) days) of any Person rated "P-1" or better by Moody's or
"A-1" or the equivalent by S&P; and

        (f)    money market mutual or similar funds having assets in excess of
$100,000,000, at least 95% of the assets of which are comprised of assets
specified in clause (a) through (e) above.

        Change of Control means (a) MarkWest Parent shall fail to own, directly
or indirectly, or fail to have voting control over, at least 51% of the equity
interest of the General Partner, (b) any Person, entity or group (other than
MarkWest Parent) acquires beneficial ownership (within the meaning of Rule 13d-3
of the Securities and Exchange Commission under the Securities Exchange Act of
1934) of 662/3% or more of the equity interests in the MLP, (c) the MLP shall
fail to own, directly or indirectly, 100% of the equity interests in the
Borrower, or (e) a Parent Change of Control shall occur.

        Change in Law means (a) the adoption of any law, rule or regulation
after the date of this Agreement, (b) any change in any law, rule or regulation
or in the interpretation or application thereof by any Governmental Authority
after the date of this Agreement or (c) compliance by any Lender or the L/C
Issuer (or, for purposes of Section 3.04(b), by any lending office of such
Lender or by such Lender's or the L/C Issuer's holding company, if any) with any
request, guideline or directive (whether or not having the force of law) of any
Governmental Authority made or issued after the date of this Agreement.

        Closing Date means May 20, 2002, the date upon which the Original Credit
Agreement was executed by the Borrower, the MLP, the Original Lenders and the
initial administrative agent.

        Code means the Internal Revenue Code of 1986.

        Collateral means all property and interests in property and proceeds
thereof now owned or hereafter acquired by the MLP, the Borrower, and their
respective Subsidiaries in or upon which a Lien now or hereafter exists in favor
of the Lenders, or the Administrative Agent on behalf of the Lenders, including,
but not limited to substantially all of the assets (including stock and other
equity interests) of the MLP, the Borrower, and their respective Subsidiaries,
whether under this Agreement, the Collateral Documents, or under any other
document executed by any Borrower Affiliate and delivered to the Administrative
Agent or the Lenders.

        Collateral Documents means (a) each guaranty, pledge agreement, security
agreement, mortgage, assignment, and all other security agreements, deeds of
trust, mortgages, chattel mortgages, assignments, pledges, guaranties, financing
statements, continuation statements, extension agreements and other similar
agreements or instruments executed by the Borrower, the MLP, any Guarantor, or
any of their respective Subsidiaries for the benefit of the Lenders now or
hereafter delivered to the Lenders or the Administrative Agent pursuant to or in
connection with the transactions contemplated hereby, and all financing
statements (or comparable documents now or hereafter filed in accordance with
the Uniform Commercial Code or comparable law) against the Borrower, the MLP,
any Guarantor, or any of their respective Subsidiaries as debtor in favor of the
Lenders or the Administrative Agent for the benefit of the Lenders as secured
party to secure or guarantee the payment of any part of the Obligations or the
performance of any other duties and obligations of Borrower under the Loan.
Documents, whenever made or delivered, and (b) any amendments, supplements,
modifications, renewals, replacements, consolidations, substitutions,
restatements, and extensions of any of the foregoing.

5

--------------------------------------------------------------------------------

        Commitment means, as to each Lender, its obligation to make Loans to the
Borrower pursuant to Section 2.01 and to purchase participations in L/C
Obligations pursuant to Section 2.14, in an aggregate principal amount at any
one time outstanding not to exceed the amount stated beside such Lender's name
on the most-recently amended Schedule 2.01 to this Agreement (which amount is
subject to increase, reduction, or cancellation in accordance with the Loan
Documents)(collectively, the Commitments of all the Lenders herein the
"Aggregate Commitments").

        Company and Companies means, on any date of determination thereof, the
MLP, the Borrower and each of their respective Subsidiaries.

        Compensation Period has the meaning set forth in Section 2.11(e)(ii).

        Compliance Certificate means a certificate substantially in the form of
Exhibit C.

        Conditions Effective Date means the first date all the conditions
precedent in Section 4.01 were satisfied or waived in accordance with Section 4.
01 (or, in the case of Sections 4.01(b) and (c), waived by the Person entitled
to receive the applicable payment).

        Consolidated EBITDA means, for any period, for the MLP and its
Subsidiaries on a consolidated basis, an amount equal to the sum of
(a) Consolidated Net Income, (b) Consolidated Interest Charges, (c) the amount
of taxes, based on or measured by income, used or included in the determination
of such Consolidated Net Income, (d) the amount of depreciation, depletion, and
amortization expense deducted in determining such Consolidated Net Income, and
(e) other non-cash charges and expenses, including, without limitation, non-cash
charges and expenses relating to Swap Contracts or resulting from accounting
convention changes, of the MLP and its Subsidiaries on a consolidated basis, all
determined in accordance with GAAP.

        Consolidated Funded Debt means, as of any date of determination, for the
MLP and its Subsidiaries on a consolidated basis, the sum of (a) the outstanding
principal amount of all obligations and liabilities, whether current or
long-term, for borrowed money (including Obligations hereunder), (b) all
reimbursement obligations relating to letters of credit, (c) Capital Leases,
(d) Synthetic Lease Obligations, and (e) without duplication, all Guaranty
Obligations with respect to Indebtedness of the type specified in subsections
(a) through (d) above.

        Consolidated Interest Charges means, for any period, for the MLP and its
Subsidiaries on a consolidated basis, the sum of (a) all interest, premium
payments, fees, charges and related expenses of the MLP and its Subsidiaries in
connection with Indebtedness (including capitalized interest), in each case to
the extent treated as interest in accordance with GAAP, and (b) the portion of
rent expense of the MLP and its Subsidiaries with respect to such period under
Capital Leases that is treated as interest in accordance with GAAP.

        Consolidated Net Income means, for any period, for the MLP and its
Subsidiaries on a consolidated basis, the net income or net loss of the MLP and
its Subsidiaries from continuing operations, provided that there shall be
excluded from such net income (to the extent otherwise included therein):
(a) the income (or loss) of any entity other than a Subsidiary in which the MLP
or any Subsidiary has an ownership interest, except to the extent that any such
income has been actually received by the MLP or such Subsidiary in the form of
cash dividends or similar cash distributions; (b) net extraordinary gains and
losses (other than, in the case of losses, losses resulting from charges against
net income to establish or increase reserves for potential environmental
liabilities and reserves for exposure under rate cases), (c) any gains or losses
attributable to non-cash write-ups or write-downs of assets, (d) proceeds of any
insurance on property, plant or equipment other than business interruption
insurance, (e) any gain or loss, net of taxes, on the sale, retirement or other
disposition of assets (including the capital stock or other equity ownership of
any other Person, but excluding the sale of inventories in the ordinary course
of business), and (f) the cumulative effect of a change in accounting
principles.

6

--------------------------------------------------------------------------------

        Contractual Obligation means, as to any Person, any provision of any
security issued by such Person or of any agreement, instrument or other
undertaking to which such Person is a party or by which it or any of its
property is bound.

        Counterparty Consent means a consent from a counterparty to a pipeline
transportation agreement consenting to the Liens granted by the Collateral
Documents and containing such other terms as are satisfactory to the
Administrative Agent.

        Credit Extension means each of the following: (a) a Borrowing and (b) an
L/C Credit Extension.

        Debtor Relief Laws means the Bankruptcy Code of the United States of
America, and all other liquidation, conservatorship, bankruptcy, assignment for
the benefit of creditors, moratorium, rearrangement, receivership, insolvency,
reorganization, or similar debtor relief Laws of the United States of America or
other applicable jurisdictions from time to time in effect and affecting the
rights of creditors generally.

        Default means any event that, with the giving of any notice, the passage
of time, or both, would be an Event of Default.

        Default Rate means an interest rate equal to (a) the Base Rate plus
(b) the Applicable Rate, if any, applicable to Base Rate Loans plus (c) 2% per
annum; provided, however, that with respect to a Eurodollar Rate Loan, the
Default Rate shall be an interest rate equal to the interest rate (including any
Applicable Rate) otherwise applicable to such Loan plus 2% per annum, in each
case to the fullest extent permitted by applicable Laws.

        Disposition or Dispose means the sale, transfer, license or other
disposition (including any sale and leaseback transaction) of any property
(including stock, partnership and other equity interests) by any Person of
property owned by such Person, including any sale, assignment, transfer or other
disposal, with or without recourse, of any notes or accounts receivable or any
rights and claims associated therewith.

        Distribution Loan means a Loan which is made in whole or in part for the
purpose of (i) paying a Quarterly Distribution, or (ii) reimbursing the purchase
price of partnership units purchased under the MLP's long-term incentive plan,
or (iii) reimbursing the purchase or redemption price of equity interests in the
Borrower or any Guarantor purchased or redeemed from their employees in
accordance with Section 7.08(b)(iii).

        Dollar and $ means lawful money of the United States of America.

        Domestic Person means any corporation, general partnership, limited
partnership, or limited liability company that is organized under the laws of
the United States of America or any state thereof or the District of Columbia.

        Eligible Assignee means (a) a Lender; (b) an Affiliate of a Lender;
(c) an Approved Fund and (d) any other Person (other than a natural Person)
approved by the Administrative Agent and, unless an Event of Default has
occurred and is continuing or in connection with the settlement of a credit
derivative transaction, the Borrower (each such approval not to be unreasonably
withheld or delayed); provided that notwithstanding the foregoing, "Eligible
Assignee" shall not include the Borrower, the MLP, any MarkWest Party, or any of
their respective Affiliates or Subsidiaries.

        Environmental Law means any applicable Law that relates to (a) the
condition or protection of air, groundwater, surface water, soil, or other
environmental media, (b) the environment, including natural resources or any
activity which affects the environment, (c) the regulation of any pollutants,
contaminants, wastes, substances, and Hazardous Substances, including, without
limitation, the Comprehensive Environmental Response, Compensation, and
Liability Act (42 U.S.C. §9601 et seq.) ("CERCLA"), the Clean Air Act (42 U.S.C.
§ 7401 et seq.), the Federal Water Pollution Control Act, as

7

--------------------------------------------------------------------------------

amended by the Clean Water Act (33 U.S.C. § 1251 et seq.), the Federal
Insecticide, Fungicide, and Rodenticide Act (7 U.S.C. § 136 et seq.), the
Emergency Planning and Community Right to Know Act of 1986 (42 U.S.C. § 1100 1
et seq.), the Hazardous Materials Transportation Act (49 U.S.C. § 1801 et seq.),
the National Environmental Policy Act of 1969 (42 U.S.C. § 4321 et seq.), the
Oil Pollution Act (33 U.S.C. § 2701 et seq.), the Resource Conservation and
Recovery Act (42 U.S.C. § 6901 et seq.), the Rivers and Harbors Act (33 U.S.C.
§401 et seq.), the Safe Drinking Water Act (42 U.S.C. § 201 and § 300f et seq.),
the Solid Waste Disposal Act, as amended by the Resource Conservation and
Recovery Act of 1976 and the Hazardous and Solid Waste Amendments of 1984 (42
U.S.C. § 6901 et seq.), the Toxic Substances Control Act (15 U.S.C. § 2601 et
seq.), and analogous state and local Laws, as any of the foregoing may have been
and may be amended or supplemented from time to time, and any analogous enacted
or adopted Law, or (d) the Release or threatened Release of Hazardous
Substances.

        Equitable Agreement means the gas purchase and sale agreement, if any,
to be entered into between Equitable Production Company and MarkWest Parent.

        Equitable Leases means the Lease Agreement executed by Equitable
Production Company as lessor and MarkWest Energy Appalachia, L.L.C. as lessee,
and the Equipment Lease Agreement and Pipeline Lease Agreement for Maytown to
Institute Pipeline dated May 28, 1999, executed by Equitable Production Company
as lessor and MarkWest Energy Appalachia, L.L.C. as lessee.

        ERISA means the Employee Retirement Income Security Act of 1974 and any
regulations issued pursuant thereto.

        ERISA Affiliate means any trade or business (whether or not
incorporated) under common control with the Borrower within the meaning of
Section 414(b) or (c) of the Code (and Sections 414(m) and (o) of the Code for
purposes of provisions of this Agreement relating to obligations imposed under
Section 412 of the Code).

        ERISA Event means (a) a Reportable Event with respect to a Pension Plan;
(b) a withdrawal by the Borrower or any ERISA Affiliate from a Pension Plan
subject to Section 4063 of ERISA during a plan year in which it was a
substantial employer (as defined in Section 4001(a)(2) of ERISA) or a cessation
of operations that is treated as such a withdrawal under Section 4062(e) of
ERISA; (c) a complete or partial withdrawal by the Borrower or any ERISA
Affiliate from a Multiemployer Plan or notification that a Multiemployer Plan is
in reorganization; (d) the filing of a notice of intent to terminate, the
treatment of a Plan amendment as a termination under Sections 4041 or 4041A of
ERISA, or the commencement of proceedings by the PBGC to terminate a Pension
Plan or Multiemployer Plan; (e) an event or condition which might reasonably be
expected to constitute grounds under Section 4042 of ERISA for the termination
of, or the appointment of a trustee to administer, any Pension Plan or
Multiemployer Plan; or (f) the imposition of any liability under Title IV of
ERISA, other than PBGC premiums due but not delinquent under Section 4007 of
ERISA, upon the Borrower or any ERISA Affiliate.

        Eurodollar Rate means for any Interest Period with respect to any
Eurodollar Rate Loan:

        (a)   the rate per annum equal to the rate determined by the
Administrative Agent to be the offered rate that appears on the page (such page
currently being page 3750) of the Telerate screen (or any successor thereto)
that displays an average British Bankers Association Interest Settlement Rate
for deposits in Dollars (for delivery on the first day of such Interest Period)
with a term equivalent to such Interest Period, determined as of approximately
11:00 a.m. (London time) two Business Days prior to the first day of such
Interest Period, or

        (b)   if the rate referenced in the preceding subsection (a) does not
appear on such page or service or such page or service shall cease to be
available, the rate per annum equal to the rate determined by the Administrative
Agent to be the offered rate on such other page or other service that displays
an average British Bankers Association Interest Settlement Rate for deposits in

8

--------------------------------------------------------------------------------

Dollars (for delivery on the first day of such Interest Period) with a term
equivalent to such Interest Period, determined as of approximately 11:00 a.m.
(London time) two Business Days prior to the first day of such Interest Period,
or

        (c)   if the rates referenced in the preceding subsections (a) and
(b) are not available, the rate per annum determined by the Administrative Agent
as the rate of interest (rounded upward to the next 1/100th of 1%) at which
deposits in Dollars for delivery on the first day of such Interest Period in
same day funds in the approximate amount of the Eurodollar Rate Loan being made,
continued or converted by the Administrative Agent and with a term equivalent to
such interest Period would be offered by the Administrative Agent's London
Branch to major banks in the offshore Dollar market at their request at
approximately 11:00 a.m. (London time) two Business Days prior to the first day
of such Interest Period.

        Eurodollar Rate Loan means a Loan that bears interest at a rate based on
the Eurodollar Rate.

        Event of Default means any of the events or circumstances specified in
Article VIII.

        Evergreen Letter of Credit has the meaning specified in
Section 2.14(b)(iii).

        Federal Funds Rate means, for any day, the rate per annum (rounded
upwards to the nearest 1/100 of 1%) equal to the weighted average of the rates
on overnight Federal funds transactions with members of the Federal Reserve
System arranged by Federal funds brokers on such day, as published by the
Federal Reserve Bank on the Business Day next succeeding such day; provided that
(a) if such day is not a Business Day, the Federal Funds Rate for such day shall
be such rate on such transactions on the next preceding Business Day as so
published on the next succeeding Business Day, and (b) if no such rate is so
published on such next succeeding Business Day, the Federal Funds Rate for such
day shall be the average rate charged to the Administrative Agent on such day on
such transactions as determined by the Administrative Agent.

        Fixed Fee Interest Charges means, for any period, the sum of all cash
interest payments made on Indebtedness for borrowed money by the MLP and its
Subsidiaries.

        Fixed Fee Interest Coverage Ratio means, as of any date of
determination, the ratio of (a) Consolidated EBITDA (less the amount, if any, by
which the contractual obligations of MarkWest Parent to the MLP or any of its
Subsidiaries on back-to-back transportation/processing contracts exceed MarkWest
Parent's rights to collect from third Persons under such contracts) for the
period of the four prior fiscal quarters ending on such date to Fixed Fee
Interest Charges during such period.

        Foreign Lender has the meaning specified in Section 10. 15.

        Fractionation, Storage and Loading Agreement (Siloam) means the
Fractionation, Storage and Loading Agreement (Siloam) agreement between MarkWest
Energy Appalachia, L.L.C. and MarkWest Parent dated as of the Conditions
Effective Date.

        Fund means any Person (other than a natural person) that is (or will be)
engaged in making, purchasing, holding or otherwise investing in commercial
loans and similar extensions of credit in the ordinary course of its business.

        GAAP means generally accepted accounting principles set forth in the
opinions and pronouncements of the Accounting Principles Board and the American
Institute of Certified Public Accountants and statements and pronouncements of
the Financial Accounting Standards Board or such other principles as may be
approved by a significant segment of the accounting profession, that are
applicable to the circumstances as of the date of determination, consistently
applied. If at any time any change in GAAP would affect the computation of any
financial ratio or requirement set forth in any Loan Document, and either the
Borrower or the Required Lenders shall so request, the Administrative Agent, the
Lenders and the Borrower shall negotiate in good faith to amend such ratio or
requirement

9

--------------------------------------------------------------------------------

to preserve the original intent thereof in light of such change in GAAP (subject
to the approval of the Required Lenders); provided that, until so amended,
(a) such ratio or requirement shall continue to be computed in accordance with
GAAP prior to such change therein and (b) the Borrower shall provide to the
Administrative Agent and the Lenders financial statements and other documents
required under this Agreement or as reasonably requested hereunder setting forth
a reconciliation between calculations of such ratio or requirement made before
and after giving effect to such change in GAAP.

        Gas Processing Agreement (Kenova, Boldman and Cobb Plants) means the Gas
Processing Agreement (Kenova, Boldman and Cobb Plants) between MarkWest Energy
Appalachia, L.L.C. and MarkWest Parent dated as of the Conditions Effective
Date.

        General Partner means MarkWest Energy GP, L.L.C., the general partner of
the MLP.

        Governmental Authority means any nation or government, any state or
other political subdivision thereof, any agency, authority, instrumentality,
regulatory body, court, administrative tribunal, central bank or other legal
entity exercising executive, legislative, judicial, taxing, regulatory or
administrative powers or functions of or pertaining to government.

        Guarantors means any Person, including the MLP and every present and
future Subsidiary of Borrower and the MLP, which undertakes to be liable for all
or any part of the Obligations by execution of a Guaranty, or otherwise.

        Guaranty means a Guaranty now or hereafter made by any Guarantor in
favor of the Administrative Agent on behalf of the Lenders, substantially in the
form of Exhibit E-1, Exhibit E-2, or Exhibit E-3, as may be amended from time to
time.

        Guaranty Obligation means, as to any Person, (a) any obligation,
contingent or otherwise, of such Person guaranteeing or having the economic
effect of guaranteeing any Indebtedness or other payment obligation of another
Person (the "primary obligor") in any manner, whether directly or indirectly,
and including any obligation of such Person, direct or indirect, (i) to purchase
or pay (or advance or supply funds for the purchase or payment of) such
Indebtedness or other payment obligation, (ii) to purchase or lease property,
securities or services for the purpose of assuring the obligee in respect of
such Indebtedness or other payment obligation of the payment of such
Indebtedness or other payment obligation, (iii) to maintain working capital,
equity capital or any other financial statement condition or liquidity of the
primary obligor so as to enable the primary obligor to pay such Indebtedness or
other payment obligation, or (iv) entered into for the purpose of assuring in
any other manner the obligees in respect of such Indebtedness or other payment
obligation of the payment thereof or to protect such obligees against loss in
respect thereof (in whole or in part), or (b) any Lien on any assets of such
Person securing any Indebtedness or other payment obligation of any other
Person, whether or not such Indebtedness or other payment obligation is assumed
by such Person; provided, however, that the term "Guaranty Obligation" shall not
include endorsements of instruments for deposit or collection in the ordinary
course of business. The amount of any Guaranty Obligation shall be deemed to be
the lesser of (a) an amount equal to the stated or determinable outstanding
amount of the related primary obligation and (b) the maximum amount for which
such guaranteeing Person may be liable pursuant to the terms of the instrument
embodying such Guaranty Obligation, unless the outstanding amount of such
primary obligation and the maximum amount for which such guaranteeing Person may
be liable are not stated or determinable, in which case the amount of such
Guaranty Obligation shall be the maximum reasonably anticipated liability in
respect thereof as determined by the guaranteeing Person in good faith.

        Hazardous Substance means any substance that poses a threat to, or is
regulated to protect, human health, safety, public welfare, or the environment,
including without limitation: (a) any "hazardous substance," pollutant" or
"contaminant," and any "petroleum" or "natural gas liquids" as those terms are
defined or used under Section 101 of the Comprehensive Environmental Response,
Compensation

10

--------------------------------------------------------------------------------

and Liability Act of 1980, as amended (42 U.S.C. §§ 9601 et seq.) ("CERCLA"),
(b) "solid waste" as defined by the federal Solid Waste Disposal Act (42 U. S.C.
§ § 6901 et seq.), (c) asbestos or a material containing asbestos, (d) any
material that contains lead or lead-based paint, (e) any item or equipment that
contains or is contaminated by polychlorinated biphenyls, (f) any radioactive
material, (g) urea formaldehyde, (h) putrescible materials, (i) infectious
materials, (j) toxic microorganisms, including mold, or (k) any substance the
presence or Release of which requires reporting, investigation or remediation
under any Environmental Law.

        Hobbs Pipeline means that certain natural gas pipeline in Lea County,
New Mexico, connected and transporting gas to Southwestern Public Service
Company's Cunningham Station, in Section 28, T18S, R36E, NMPM, and Maddox
Station in Section 25, T18S, R36E, NMPM, Lea County, New Mexico.

        Honor Date has the meaning set forth in Section 2.14(c)(i).

        Indebtedness means, as to any Person at a particular time, all of the
following:

        (a)   all obligations of such Person for borrowed money and all
obligations of such Person evidenced by bonds, debentures, notes, loan
agreements or other similar instruments;

        (b)   the face amount of all letters of credit (including standby and
commercial), banker's acceptances, Bank Guaranties, surety bonds, and similar
instruments issued for the account of such Person, and, without duplication, all
drafts drawn and unpaid thereunder;

        (c)   net obligations under any Swap Contract in an amount equal to
(i) if such Swap Contract has been closed out, the termination value thereof, or
(ii) if such Swap Contract has not been closed out, the mark-to-market value
thereof determined on the basis of readily available quotations provided by any
recognized dealer in such Swap Contract;

        (d)   whether or not so included as liabilities in accordance with GAAP,
all obligations of such Person to pay the deferred purchase price of property or
services, other than trade accounts payable in the ordinary course of business
not overdue by more than 60 days, and indebtedness (excluding prepaid interest
thereon) secured by a Lien on property owned or being purchased by such Person
(including indebtedness arising under conditional sales or other title retention
agreements), whether or not such indebtedness shall have been assumed by such
Person or is limited in recourse;

        (e)   Capital Leases and Synthetic Lease Obligations; and

        (f)    all Guaranty Obligations of such Person in respect of any of the
foregoing.

        For all purposes hereof, the Indebtedness of any Person shall include
the Indebtedness of any partnership or joint venture in which such Person is a
general partner, unless such Indebtedness is expressly made non-recourse to such
Person except for customary exceptions acceptable to the Required Lenders. The
amount of any Capital Lease or Synthetic Lease as of any date shall be deemed to
be the amount of Attributable Indebtedness in respect thereof as of such date.

        Indemnified Liabilities has the meaning set forth in Section 10. 05.

        Indemnitees has the meaning set forth in Section 10.05.

        Insurance Deposit Account has the meaning set forth in Section 6.07(b).

        Interest Coverage Ratio means, as of any date of determination, the
ratio of (a) Consolidated EBITDA for the period of the four prior fiscal
quarters ending on such date to (b) the sum of (i) Consolidated Interest Charges
during such period and (ii) imputed interest charges on Synthetic Leases, of the
MLP and its Subsidiaries during such period.

11

--------------------------------------------------------------------------------

        Interest Payment Date means, (a) as to any Loan other than a Base Rate
Loan, the last day of each Interest Period applicable to such Loan; provided,
however, that if any Interest Period for a Eurodollar Rate Loan exceeds three
months, the respective dates that fall every three months after the beginning of
such Interest Period shall also be Interest Payment Dates; and (b) as to any
Base Rate Loan, the last Business Day of each March, June, September and
December and the Maturity Date.

        Interest Period means, as to each Eurodollar Rate Loan, the period
commencing on the date such Eurodollar Rate Loan is disbursed or converted to or
continued as a Eurodollar Rate Loan and ending on the date one, two, three or
six months thereafter, as selected by the Borrower in its Borrowing Notice;
provided that:

        (i)    any Interest Period that would otherwise end on a day that is not
a Business Day shall be extended to the next succeeding Business Day unless, in
the case of a Eurodollar Rate Loan, such Business Day falls in another calendar
month, in which case such Interest Period shall end on the next preceding
Business Day;

        (ii)   any Interest Period pertaining to a Eurodollar Rate Loan that
begins on the last Business Day of a calendar month (or on a day for which there
is no numerically corresponding day in the calendar month at the end of such
Interest Period) shall end on the last Business Day of the calendar month at the
end of such Interest Period; and

        (iii)  no Interest Period shall extend beyond the scheduled Maturity
Date.

        Investment means, as to any Person, any acquisition or investment by
such Person, whether by means of (a) the purchase or other acquisition of
capital stock or other securities of another Person, (b) a loan, advance or
capital contribution to, guaranty of debt of, or purchase or other acquisition
of any other debt or equity participation or interest in, another Person,
including any partnership or joint venture interest in such other Person, or
(c) the purchase or other acquisition (in one transaction or a series of
transactions) of assets of another Person that constitute a business unit. For
purposes of covenant compliance, the amount of any Investment shall be the
amount actually invested, without adjustment for subsequent increases or
decreases in the value of such Investment, less all returns of principal or
equity thereon, and shall, if made by the transfer or exchange of property other
than cash be deemed to have been made in an amount equal to the fair market
value of such property.

        IRS means the United States Internal Revenue Service.

        ISDA means the International Swaps and Derivatives Association, Inc.

        Lake Whitney Pipeline means that certain natural gas pipeline lateral in
Johnson, Hill and Bosque Counties, Texas, approximately 33 miles in length,
connected and delivering gas to SEI Texas, LP's electrical generation facility
located in Bosque County, Texas.

        Laws means, collectively, all applicable international, foreign,
federal, state and local statutes, treaties, rules, regulations, ordinances,
codes and administrative or judicial precedents or authorities, including the
interpretation or administration thereof by any Governmental Authority charged
with the enforcement, interpretation or administration thereof, and all
applicable administrative orders, licenses, authorizations and permits of, any
Governmental Authority.

        L/C Advance means, with respect to each Lender, such Lender's
participation in any L/C Borrowing in accordance with its Pro Rata Share.

        L/C Borrowing means an extension of credit resulting from a drawing
under any Letter of Credit which has not been reimbursed on the date when made
or refinanced as a Borrowing.

        L/C Credit Extension means, with respect to any Letter of Credit, the
issuance thereof or extension of the expiry date thereof, or the renewal or
increase of the amount thereof.

12

--------------------------------------------------------------------------------

        L/C Issuer means Royal Bank of Canada in its capacity as issuer of
Letters of Credit hereunder, or any successor issuer of Letters of Credit
hereunder.

        L/C Obligations means, as at any date of determination, the aggregate
undrawn face amount of all outstanding Letters of Credit plus the aggregate of
all Unreimbursed Amounts, including all L/C Borrowings.

        Lender has the meaning specified in the introductory paragraph hereto
and, as the context requires, includes the L/C Issuer.

        Lender Hedging Agreement means a Swap Contract between a Company and a
Lender or an Affiliate of a Lender.

        Lending Office means, as to any Lender, the office or offices of such
Lender set forth on its Administrative Details Form, or such other office or
offices as a Lender may from time to time notify the Borrower and the
Administrative Agent.

        Letter of Credit means any standby or commercial letter of credit issued
hereunder.

        Letter of Credit Application means an application and agreement for the
issuance or amendment of a letter of credit in the form from time to time in use
by the L/C Issuer.

        Letter of Credit Expiration Date means the day that is five days prior
to the Maturity Date (or, if such day is not a Business Day, the next preceding
Business Day).

        Letter of Credit Sublimit means an amount equal to the lesser of the
Aggregate Commitments and $5,000,000.

        Leverage Ratio means, for the MLP and its Subsidiaries on a consolidated
basis, the ratio of (a) Consolidated Funded Debt as of the determination date to
(b) Consolidated EBITDA for the period of the four fiscal quarters ending on
such date, or if such date is not the last day of a fiscal quarter, ending on
the last day of the fiscal quarter most recently ended.

        Lien means any mortgage, pledge, hypothecation, assignment, deposit
arrangement, encumbrance, lien (statutory or other), charge, or preference,
priority or other security interest or preferential arrangement of any kind or
nature whatsoever to secure or provide for payment of any obligation of any
Person (including any conditional sale or other title retention agreement, any
financing lease having substantially the same economic effect as any of the
foregoing, and the filing of any financing statement under the Uniform
Commercial Code or comparable Laws of any jurisdiction), including the interest
of a purchaser of accounts receivable.

        Limited Liability Company Agreement (Borrower) means the Amended and
Restated Limited Liability Company Agreement of the Borrower.

        Loan means an extension of credit by a Lender to the Borrower pursuant
to Section 2.01.

        Loan Documents means this Agreement, each Note, each of the Collateral
Documents, the Agent/Arranger Fee Letter, each Borrowing Notice, each Compliance
Certificate, the Guaranties, any Subordination Agreement, each Letter of Credit
Application, and each other agreement, document or instrument delivered by the
Borrower or any of its Subsidiaries from time to time in connection with this
Agreement and the Notes.

        Loan Party means each of the Borrower, each Guarantor, and each other
entity that is an Affiliate of the Borrower that executes one or more Loan
Documents.

        MarkWest Parent means MarkWest Hydrocarbon, Inc., a Delaware
corporation.

13

--------------------------------------------------------------------------------

        MarkWest Parent Pledge Agreement means the Security Agreement of even
date with this Agreement between MarkWest Parent and Borrower pursuant to which
MarkWest Parent pledges a $2,500,000 cash deposit to secure certain obligations
owing to Borrower under one or more Material Agreements.

        MarkWest Party means MarkWest Parent or any Subsidiary of MarkWest
Parent, other than the General Partner, the MLP, the Borrower and its
Subsidiaries.

        Material Adverse Effect means (a) a material adverse change in, or a
material adverse effect upon, the operations, business, properties or condition
(financial or otherwise) or prospects of the Borrower and its Subsidiaries taken
as a whole or the MLP and its Subsidiaries taken as a whole; (b) a material
impairment of the ability of the Borrower, or any other Loan Party to perform
their obligations under the Loan Documents to which it is a party; or (c) a
material adverse effect upon the legality, validity, binding effect or
enforceability against the Borrower or any other Loan Party of any Loan
Documents.

        Material Agreements means the following, which shall be satisfactory to
the Administrative Agent and the Required Lenders: (a) the Omnibus Agreement,
(b) the Gas Processing Agreement (Kenova, Boldman and Cobb Plants), the Pipeline
Liquids Transportation Agreement, the Fractionation, Storage and Loading
Agreement (Siloam), and the Natural Gas Liquids Purchase Agreement (Maytown),
(c) Gas Processing Agreement (Maytown) dated May 28, 1989 between Equitable
Production Company and Borrower as assignee of MarkWest Parent, and (d) any
other contract material to the business of the MLP or the Borrower to which the
Borrower or any Borrower Affiliate is a party. "Material Agreement" means each
of such Material Agreements.

        Maturity Date means (a) the Stated Maturity Date, or (b) such earlier
effective date of any other termination, cancellation, or acceleration of all
Commitments under this Agreement.

        Maximum Amount and Maximum Rate respectively mean, for each Lender, the
maximum nonusurious amount and the maximum non-usurious rate of interest which,
under applicable Law, such Lender is permitted to contract for, charge, take,
reserve, or receive on the Obligations.

        Midstream Businesses means gathering, transportation, fractionation,
processing, marketing, and storage of natural gas, crude oil, natural gas
liquids and other liquid and gaseous hydrocarbons and businesses closely related
to the foregoing.

        MLP Offering means a sale to the public after the Restatement Date of
common or preferred units in the MLP (or any other sale to the public of
partnership interests or other equity interests in the MLP including from debt
convertible into equity in the MLP).

        Mortgaged Properties means collectively all the Mortgaged Property as
defined in the Mortgages and Mortgaged Property individual means any one of such
Mortgaged Properties.

        Mortgages means the mortgages, deeds of trust, or similar instruments
executed by any of the Loan Parties in favor of Administrative Agent, for the
benefit of the Lenders, and all supplements, assignments, amendments, and
restatements thereto (or any agreement in substitution therefore, and "Mortgage"
means each of such Mortgages).

        Multiemployer Plan means any employee benefit plan of the type described
in Section 4001(a)(3) of ERISA, to which the Borrower or any ERISA Affiliate
makes or is obligated to make contributions, or during the preceding three
calendar years, has made or been obligated to make contributions.

        MW Blackhawk means MarkWest Blackhawk L.P., a Texas limited partnership,

        MW GP means MarkWest Texas GP,, L.L.C., a Delaware limited liability
company.

        MW Limited means MarkWest Texas Limited, L.L.C., a Delaware limited
liability company.

        MW Michigan means MarkWest Michigan Pipeline Company, L.L.C., a Michigan
limited liability company.

14

--------------------------------------------------------------------------------

        MW Pinnacle means MarkWest Pinnacle L.P., a Texas limited partnership.

        MW PNG means MarkWest PNG Utility L.P., a Texas limited partnership.

        MW Power Tex means MarkWest Power Tex, L.P., a Texas limited
partnership, formerly known as MarkWest New Mexico, L.P., a Texas limited
partnership, which pursuant to a merger with MW Pinnacle acquired the so-called
Power Tex assets.

        MW Texas PNG means MarkWest Texas PNG Utility L.P., a Texas limited
partnership.

        MW Western means MarkWest Western Oklahoma Gas Company, L.L.C., an
Oklahoma limited liability company.

        Natural Gas Liquids Purchase Agreement (Maytown) means the Natural Gas
Liquids Purchase Agreement (Maytown) between MarkWest Energy Appalachia, L.L.C.
and MarkWest Parent dated as of the Conditions Effective Date.

        Natural Resources/Triana Agreement means the gas processing agreement
between Columbia Natural Resources, LLC, a Triana company, and MarkWest Parent.

        Net Cash Proceeds means (a) with respect to any Disposition, cash
(including any cash received by way of deferred payment as and when received)
received by the Borrower or any of its Subsidiaries in connection with and as
consideration therefor, on or after the date of consummation of such
transaction, after (i) deduction of Taxes payable in connection with or as a
result of such transaction, and (ii) payment of all usual and customary
brokerage commissions and all other reasonable fees and expenses related to such
transaction (including, without limitation, reasonable attorneys' fees and
closing costs incurred in connection with such transaction), and (b) with
respect to any Subordinated Indebtedness, proceeds of such Indebtedness after
payment of all reasonable closing costs.

        Nonrenewal Notice Date has the meaning specified in
Section 2.14(b)(iii).

        Notes means a promissory note of the Borrower, substantially in the form
of Exhibit B hereto, evidencing the obligation of Borrower to repay the Loans,
and "Note" means any one of such promissory notes issued hereunder.

        Obligations means all advances to, and debts, liabilities, obligations,
covenants and duties of, any Loan Party arising under any Loan Document, whether
direct or indirect (including those acquired by assumption), absolute or
contingent, due or to become due, now existing or hereafter arising and
including interest that accrues after the commencement by or against any Loan
Party of any proceeding under any Debtor Relief Laws naming such Person as the
debtor in such proceeding. In addition, all references to the "Obligations" in
the Collateral Documents and in Sections 2.13 and 10.09 of this Agreement shall,
in addition to the foregoing, also include all present and future indebtedness,
liabilities, and obligations (and all renewals and extensions thereof or any
part thereof now or hereafter owed to any Lender or any Affiliate of a Lender
arising pursuant to any Lender Hedging Agreement and all Bank Service
Obligations.

        Obligor means the Borrower or any other Person (other than the
Administrative Agent, Syndication Agent or any Lender) obligated under any Loan
Document.

        Omnibus Agreement means the Omnibus Agreement dated as of May 24, 2002,
among the MLP, the Borrower, and MarkWest Parent.

        Organization Documents means, (a) with respect to any corporation, the
certificate or articles of incorporation and the bylaws; (b) with respect to any
limited liability company, the certificate of formation and operating agreement;
and (c) with respect to any partnership, joint venture, trust or other form of
business entity, the partnership, joint venture or other applicable agreement of
formation and any agreement, instrument, filing or notice with respect thereto
filed in connection with its

15

--------------------------------------------------------------------------------

formation with the secretary of state or other department in the state of its
formation, in each case as amended from time to time.

        Other Taxes has the meaning specified in Section 3. 01(b).

        Outstanding Amount on any date (i) with respect to Loans, means the
aggregate principal amount thereof after giving effect to any Borrowings and
prepayments or repayments occurring on such date, (ii) with respect to any L/C
Obligations, the amount of such L/C Obligations on such date after giving effect
to any L/C Credit Extension occurring on such date and any other changes in the
aggregate amount of the L/C Obligations as of such date, including as a result
of any reimbursements of outstanding unpaid drawings under any Letters of Credit
or any reductions in the maximum amount available for drawing under Letters of
Credit taking effect on such date, and (iii) for purposes of Section 2.11(d)
with respect to Obligations under a Lender Hedging Agreement, means the amount
then due and payable under such Lender Hedging Agreement.

        Parent Change of Control means the acquisition by any Person, or two or
more Persons acting in concert (other than John Fox and members of his family),
of beneficial ownership (within the meaning of Rule 13d-3 of the Securities and
Exchange Commission under the Securities Exchange Act of 1934) of 30% or more of
the outstanding shares of voting stock of MarkWest Parent.

        Parent Credit Agreement means the Fifth Amended and Restated Credit
Agreement dated as of the Conditions Effective Date executed by the MarkWest
Parent, Bank of America, N.A., as administrative agent and as a lender, and the
other lenders parties thereto, as the same may from time to time be amended and
restated.

        Participant has the meaning specified in Section 10.07(d).

        Partnership Agreement (MLP) means the First Amended and Restated
Agreement of Limited Partnership of the MLP.

        PBGC means the Pension Benefit Guaranty Corporation.

        Pension Plan means any "employee pension benefit plan" (as such term is
defined in Section 3(2)(A) of ERISA), other than a Multiemployer Plan, that is
subject to Title IV of ERISA and is sponsored or maintained by the Borrower or
any ERISA Affiliate or to which the Borrower or any ERISA Affiliate contributes
or has an obligation to contribute, or in the case of a multiple employer plan
(as described in Section 4064(a) of ERISA) has made contributions at any time
during the immediately preceding five plan years.

        Permitted Acquisition means an Acquisition by the Borrower or a
Subsidiary of the Borrower resulting in ownership of assets inside the United
States or Canada, or of equity interests in a Domestic Person, so long as the
following requirements have been satisfied:

        (i)    If such Acquisition results in the Borrower's ownership of a
Subsidiary, the Borrower shall have complied with the requirements of Sections
6.15 and 6.16 as of the date of such Acquisition;

        (ii)   If the Purchase Price for such Acquisition, when added to the
purchase price for all Acquisitions made during the most recent twelve
(12) calendar months (including the calendar month in which such Acquisition is
closed), equals or exceeds $10,000,000, then not less than fourteen (14) days
prior to the closing of such Acquisition, the Borrower shall deliver to the
Administrative Agent a certificate of a Responsible Officer of the Borrower
demonstrating pro forma compliance with Sections 7.01, 7.04 and 7.15, as of the
closing of such Acquisition after giving effect thereto and after giving effect
to any Indebtedness (including Obligations) incurred in connection therewith;

16

--------------------------------------------------------------------------------

        (iii)  With respect to Acquisitions involving acquisitions of an equity
interest, such Acquisition shall have been approved or consented to by the board
of directors or similar governing entity of the Person being acquired; and

        (iv)  As of the closing of such Acquisition no Default or Event of
Default shall exist or occur as a result of, and after giving effect to, such
Acquisition.

        Permitted Liens means Liens permitted under Section 7.01 as described in
such Section.

        Person means any individual, trustee, corporation, general partnership,
limited partnership, limited liability company, joint stock company, trust,
unincorporated organization, bank, business association, firm, joint venture or
Governmental Authority.

        Pipeline Liquids Transportation Agreement means the Pipeline Liquids
Transportation Agreement between MarkWest Energy Appalachia, L.L.C. and MarkWest
Parent dated as of the Conditions Effective Date.

        Plan means any "employee benefit plan" (as such term is defined in
Section 3(3) of ERISA) established by the Borrower or any ERISA Affiliate.

        Pro Rata Share means, at any date of determination, for any Lender, the
percentage (carried out to the ninth decimal place) that its Commitment bears to
the Aggregate Commitments.

        Purchase Price means, with respect to any Acquisition, all direct,
indirect, and deferred cash and non-cash payments made to or for the benefit of
the Person being acquired (or whose assets are being acquired), its
shareholders, officers, directors, employees, or Affiliates in connection with
such Acquisition, including, without limitation, the amount of any Indebtedness
being assumed in connection with such Acquisition and (subject to the
limitations on Indebtedness hereunder) seller financing, payments under
non-competition or consulting agreements entered into in connection with such
Acquisition and similar agreements, all non-cash consideration and the value of
any stock, options, or warrants or other rights to acquire stock issued as part
of the consideration in such transaction.

        Quarterly Distributions means with respect to the Borrower, the
distributions by the Borrower of Available Cash (as defined in the Limited
Liability Company Agreement (Borrower)) or with respect to MLP, the
distributions by the MLP of Available Cash (as defined in the Partnership
Agreement (MLP)).

        Reduction Amount has the meaning set forth in the definition of
Triggering Sale.

        Register has the meaning set forth in Section 10.07(c).

        Reinvested means used for any capital expenditures or any Acquisitions
in connection with the Midstream Business of a Company.

        Related Parties means, with respect to any specified Person, such
Person's Affiliates and the respective directors, officers, employees, agents
and advisors of such Person and such Person's Affiliate.

        Release means any spilling, leaking, pumping, pouring, emitting,
emptying, discharging, injecting, escaping, leaching, dumping, disposal,
deposit, dispersal, migrating, or other movement into the air, ground, or
surface water, or soil.

        Reportable Event means any of the events set forth in Section 4043(c) of
ERISA, other than events for which the 30 day notice period has been waived.

        Request for Credit Extension means (a) with respect to a Borrowing,
conversion or continuation of Loans, a Borrowing Notice, and (b) with respect to
an L/C Extension, a Letter of Credit Application.

        Required Lenders means (a) on any date of determination on and after the
Restatement Date and prior to the date of the initial Borrowing under this
Agreement, those Lenders holding more than

17

--------------------------------------------------------------------------------

662/3% of the Commitment, (b) on any date of determination on and after the date
of the initial Borrowing under this Agreement and prior to the Maturity Date,
those Lenders holding more than 662/3% of the Outstanding Amount of Loans.

        Responsible Officer means the president, chief executive officer,
executive vice president, senior vice president, vice president, chief financial
officer, controller, treasurer or assistant treasurer of a Person. Any document
delivered hereunder that is signed by a Responsible Officer of a Loan Party
shall be conclusively presumed to have been authorized by all necessary
corporate, partnership, limited liability company, and/or other action on the
part of such Loan Party and such Responsible Officer shall be conclusively
presumed to have acted on behalf of such Loan Party.

        Restatement Conditions Effective Date means the first date all the
conditions precedent in Section 4.02 are satisfied or waived in accordance with
Section 4. 02 (or, in the case of Sections 4.02(b) and (c), waived by the Person
entitled to receive the applicable payment).

        Restatement Date means the date upon which this Agreement has been
executed by the Borrower, the MLP, the Lenders and the Administrative Agent.

        Restricted Payment by a Person means any dividend or other distribution
(whether in cash, securities or other property) with respect to any equity
interest in such Person, or any payment (whether in cash, securities or other
property), including any sinking fund or similar deposit on account of the
purchase, redemption, retirement, acquisition, cancellation or termination of
any such equity interest or of any option, warrant or other right to acquire any
such equity interest.

        Rights means rights, remedies, powers, privileges, and benefits.

        Rio Nogales Pipelines means those two natural gas pipeline laterals in
Guadalupe and Caldwell Counties, Texas, one approximately twenty-two (22) miles
in length and the other approximately seven (7) miles in length, connected and
transporting gas to Rio Nogales Power Project, LP's electrical generation
facility located in or near the city of Seguin, Guadalupe County, Texas.

        Security Agreements means, collectively, the security agreements, or
similar instruments, executed by any of the Loan Parties in favor of the
Administrative Agent for the benefit of the Lenders, and all supplements,
assignments, amendments, and restatements thereto (or any agreement in
substitution therefore), and "Security Agreement" means each of such Security
Agreements.

        Shell Pipeline Acquisition means the acquisition by MW Michigan of a
crude oil gathering pipeline and related assets located in the State of Michigan
from Shell Pipeline Company, L.P. and Equilon Energy, L.L.C.

        Shell Pipeline Funding Conditions Effective Date means the first date
all the conditions precedent in Section 4.04 were satisfied or waived in
accordance with Section 4. 04 (or, in the case of Sections 4.01(b) and (c),
waived by the Person entitled to receive the applicable payment).

        Stated Maturity Date means November 30, 2006.

        Subsidiary of a Person means a corporation, partnership, joint venture,
limited liability company or other business entity of which a majority of the
shares of securities or other interests having ordinary voting power for the
election of directors or other governing body (other than securities or
interests having such power only by reason of the happening of a contingency)
are at the time beneficially owned, or the management of which is otherwise
controlled, directly, or indirectly through one or more intermediaries, or both,
by such Person. Unless otherwise specified, all references herein to a
"Subsidiary" or to "Subsidiaries" shall refer to a Subsidiary or Subsidiaries of
the Borrower.

        Subordinated Indebtedness has the meaning set forth in Section 7.04(c).

        Subordination Agreement has the meaning set forth in Section 7.04(c).

18

--------------------------------------------------------------------------------

        Swap Contract means (a) any and all rate swap transactions, basis swaps,
credit derivative transactions, forward rate transactions, commodity swaps,
commodity options, forward commodity contracts, equity or equity index swaps or
options, bond or bond price or bond index swaps or options or forward bond or
forward bond price or forward bond index transactions, interest rate options,
forward foreign exchange transactions, cap transactions, floor transactions,
collar transactions, currency swap transactions, cross-currency rate swap
transactions, currency options, spot contracts, or any other similar
transactions or any combination of any of the foregoing (including any options
to enter into any of the foregoing), whether or not any such transaction is
governed by or subject to any master agreement, and (b) any and all transactions
of any kind, and the related confirmations, which are subject to the terms and
conditions of, or governed by, any form of master agreement published by the
International Swaps and Derivatives Association, Inc., any International Foreign
Exchange Master Agreement, or any other master agreement (any such master
agreement, together with any related schedules, a "Master Agreement"), including
any such obligations or liabilities under any Master Agreement.

        Swap Termination Value means, in respect of any one or more Swap
Contracts, after taking into account the effect of any legally enforceable
netting agreement relating to such Swap Contracts, (a) for any date on or after
the date such Swap Contracts have been closed out and termination value(s)
determined in accordance therewith, such termination value(s), and (b) for any
date prior to the date referenced in clause (a) the amount(s) determined as the
mark-to-market value(s) for such Swap Contracts, as determined based upon one or
more mid-market or other readily available quotations provided by any recognized
dealer in such Swap Contracts (which may include any Lender).

        Syndication Agent means Bank One, NA in its capacity as syndication
agent under this Agreement, or any successor syndication agent.

        Synthetic Lease Obligation means the monetary obligation of a Person
under (a) a so-called synthetic or tax retention lease, or (b) an agreement for
the use or possession of property creating obligations that do not appear on the
balance sheet of such Person but which are depreciated for tax purposes by such
Person. The amount of any Synthetic Lease Obligation as of any date shall be
deemed to be the amount of Attributable Indebtedness in respect thereof as of
such date.

        Taxes has the meaning set forth in Section 3.01.

        Threshold Amount at any time means an amount equal to 10% of the MLP's
consolidated assets measured as of the close of the then most recent fiscal
quarter end.

        Triggering Sale means any Disposition (including sales of stock of
Subsidiaries) (other than a Disposition permitted by Section 7.07(a) or (b)) by
the Borrower or any Subsidiary of the Borrower to any other Person (other than
to the Borrower or to a Wholly-Owned Subsidiary of the Borrower) with respect to
which the Net Cash Proceeds realized by any Company for such Disposition, when
aggregated with the Net Cash Proceeds from all such other Dispositions by all
Companies occurring since the Closing Date, equals or exceeds the Threshold
Amount. The portion of the Net Cash Proceeds in excess of the Threshold Amount
is herein called the "Reduction Amount."

        Type means, with respect to a Loan, its character as a Base Rate Loan or
a Eurodollar Rate Loan.

        Unfunded Pension Liability means the excess of a Pension Plan's benefit
liabilities under Section 4001(a)(16) of ERISA, over the current value of that
Pension Plan's assets, determined in accordance with the assumptions used for
funding the Pension Plan pursuant to Section 412 of the Code for the applicable
plan year.

        Unreimbursed Amount has the meaning set forth in Section 2.14(c)(i).

19

--------------------------------------------------------------------------------

        Voting Stock means the capital stock (or equivalent thereof) of any
class or kind, of a Person, the holders of which are entitled to vote for the
election of directors, managers, or other voting members of the governing body
of such Person.

        Wholly-Owned when used in connection with a Person means any Subsidiary
of such Person of which all of the issued and outstanding equity interests
(except shares required as directors' qualifying shares) shall be owned by such
Person or one or more of its Wholly-Owned Subsidiaries.

        1.02    Other Interpretive Provisions.    

        (a)   The meanings of defined terms are equally applicable to the
singular and plural forms of the defined terms.

        (b)   (i) The words "herein" and "hereunder" and words of similar import
when used in any Loan Document shall refer to such Loan Document as a whole and
not to any particular provision thereof.

        (ii)   Unless otherwise specified herein, Article, Section, Exhibit and
Schedule references are to this Agreement.

        (iii)  The term "including" is by way of example and not limitation.

        (iv)  The term "documents" includes any and all instruments, documents,
agreements, certificates, notices, reports, financial statements and other
writings, however evidenced.

        (c)   In the computation of periods of time from a specified date to a
later specified date, the word "from" means "from and including;" the words "to"
and "until" each mean "to but excluding;" and the word "through" means "to and
including."

        (d)   Section headings herein and the other Loan Documents are included
for convenience of reference only and shall not affect the interpretation of
this Agreement or any other Loan Document.

        1.03    Accounting Terms.    

        All accounting terms not specifically or completely defined herein shall
be construed in conformity with, and all financial data required to be submitted
pursuant to this Agreement shall be prepared in conformity with, GAAP applied on
a consistent basis, as in effect from time to time, applied in a manner
consistent with that used in preparing the audited financial statements, except
as otherwise specifically prescribed herein.

        1.04    Rounding.    Any financial ratios required to be maintained by
the Borrower pursuant to this Agreement shall be calculated by dividing the
appropriate component by the other component, carrying the result to one place
more than the number of places by which such ratio is expressed herein and
rounding the result up or down to the nearest number (with a rounding-up if
there is no nearest number).

        1.05    References to Agreements and Laws.    Unless otherwise expressly
provided herein, (a) references to agreements (including the Loan Documents) and
other contractual instruments shall be deemed to include all subsequent
amendments, restatements, extensions, supplements and other modifications
thereto, but only to the extent that such amendments, restatements, extensions,
supplements and other modifications are not prohibited by any Loan Document; and
(b) references to any Law shall include all statutory and regulatory provisions
consolidating, amending, replacing, supplementing or interpreting such Law.

Remainder of this page intentionally left blank.

20

--------------------------------------------------------------------------------

ARTICLE II.
THE COMMITMENTS AND BORROWINGS

        2.01    Loans.    Subject to and in reliance upon the terms, conditions,
representations, and warranties in the Loan Documents, each Lender severally,
but not jointly, agrees to make loans (each such Loan a "Loan") to Borrower from
time to time on any Business Day during the period from the Restatement
Conditions Effective Date to the Maturity Date, in an aggregate amount not to
exceed at any time outstanding the amount of such Lender's Pro Rata Share of one
or more Borrowings not to exceed, when aggregated with the Outstanding Amount of
the L/C Obligations, such Lender's Commitment; provided that until consummation
of the Shell Pipeline Acquisition the aggregate amount of Loans and L/C
Obligations hereunder shall not exceed $116,700,000 (it being agreed and
understood that $23,300,000 of the Aggregate Commitment is reserved exclusively
to fund the Shell Pipeline Acquisition and capital expenditures related thereto
and will be advanced only upon compliance with (or waiver of) the conditions
specified in Section 4.04). Such Borrowings may be repaid and reborrowed from
time to time in accordance with the terms and provisions of the Loan Documents;
provided that, each such Borrowing must occur on a Business Day and no later
than the Business Day immediately preceding the Maturity Date.

        2.02    Intentionally Omitted.    

        2.03    Borrowings, Conversions and Continuations of Loans.    

        (a)   Each Borrowing, each conversion of Loans from one Type to the
other, and each continuation of Loans as the same Type shall be made upon the
Borrower's irrevocable notice to the Administrative Agent, which may be given by
telephone. Each such notice must be received by the Administrative Agent not
later than 10:00 a.m., Houston, Texas time, (i) three Business Days prior to the
requested date of any Borrowing of, conversion to or continuation of Eurodollar
Rate Loans, and (ii) one Business Day prior to the conversion of Eurodollar Rate
Loans to Base Rate Loans, or the requested date of any Borrowing of Base Rate
Loans. Each such telephonic notice must be confirmed promptly by delivery to the
Administrative Agent of a written Borrowing Notice, appropriately completed and
signed by an authorized officer of the Borrower. Each Borrowing of, conversion
to or continuation of Eurodollar Rate Loans shall be in a principal amount of
$500,000 or a whole multiple of $500,000 in excess thereof. Each Borrowing of or
conversion to Base Rate Loans shall be in a principal amount of $500,000 or a
whole multiple of $100,000 in excess thereof. Each Borrowing Notice (whether
telephonic or written) shall specify (i) whether the Borrower is requesting a
Borrowing, a conversion of Loans from one Type to the other, or a continuation
of Loans as the same Type, (ii) the requested date of the Borrowing, conversion
or continuation, as the case may be (which shall be a Business Day), (iii) the
principal amount of Loans to be borrowed, converted or continued, (iv) the Type
of Loans to be borrowed or to which existing Loans are to be converted, and
(v) if applicable, the duration of the Interest Period with respect thereto. If
the Borrower fails to specify a Type of Loan in a Borrowing Notice or if the
Borrower fails to give a timely notice requesting a conversion or continuation,
then the applicable Loans shall be made or continued as, or converted to, Base
Rate Loans. Any such automatic conversion to Base Rate Loans shall be effective
as of the last day of the Interest Period then in effect with respect to the
applicable Eurodollar Rate Loans. If the Borrower requests a Borrowing of,
conversion to, or continuation of Eurodollar Rate Loans in any such Borrowing
Notice, but fails to specify an Interest Period, it will be deemed to have
specified an Interest Period of one month.

        (b)   Following receipt of a Borrowing Notice, the Administrative Agent
shall promptly notify each Lender of its Pro Rata Share of the applicable Loans,
and if no timely notice of a conversion or continuation is provided by the
Borrower, the Administrative Agent shall notify each Lender of the details of
any automatic conversion to Base Rate Loans described in the preceding
subsection. In the case of a Borrowing, each Lender shall make the amount of its
Loan available to the

21

--------------------------------------------------------------------------------

Administrative Agent in immediately available funds at the Administrative
Agent's Office not later than 12:00 Noon, Houston, Texas time, on the Business
Day specified in the applicable Borrowing Notice. Upon satisfaction of the
applicable conditions set forth in Section 4.03 (and Section 4.02 and if such
Borrowing is to fund the Shell Pipeline Acquisition on the Shell Pipeline
Funding Conditions Effective Date, Section 4.04), the Administrative Agent shall
make all funds so received available to the Borrower in like funds as received
by the Administrative Agent either by (i) crediting the account of the Borrower
on the books of the Administrative Agent with the amount of such funds or
(ii) wire transfer of such funds, in each case in accordance with instructions
provided to the Administrative Agent by the Borrower; provided, however, that
if, on the date of the Borrowing there are L/C Borrowings outstanding, then the
proceeds of such Borrowing shall be applied, first, to the payment in full of
any such L/C Borrowings, and second, to the Borrower as provided above.

        (c)   Except as otherwise provided herein, a Eurodollar Rate Loan may be
continued or converted only on the last day of the Interest Period for such
Eurodollar Rate Loan. During the existence of a Default or Event of Default, no
Loans may be requested as, converted to or continued as Eurodollar Rate Loans
without the consent of the Required Lenders, and the Required Lenders may demand
that any or all of the then outstanding Eurodollar Rate Loans be converted
immediately to Base Rate Loans.

        (d)   The Administrative Agent shall promptly notify the Borrower and
the Lenders of the interest rate applicable to any Eurodollar Rate Loan upon
determination of such interest rate. The determination of the Eurodollar Rate by
the Administrative Agent shall be conclusive in the absence of manifest error.

        (e)   After giving effect to all Borrowings, all conversions of Loans
from one Type to the other, and all continuations of Loans as the same Type,
there shall not be more than six (6) Interest Periods in effect at any given
time with respect to Loans.

        2.04    Prepayments.    

        (a)    Optional Prepayments.    The Borrower may, upon notice to the
Administrative Agent, at any time or from time to time voluntarily prepay in
whole or in part Loans outstanding hereunder without premium or penalty;
provided that (i) such notice must be received by the Administrative Agent not
later than 10:00 a.m., Houston, Texas time, (A) three Business Days prior to any
date of prepayment of Eurodollar Rate Loans, and (B) the date of prepayment of
Base Rate Loans; (ii) any prepayment of Eurodollar Rate Loans shall be in a
principal amount of $500,000 or a whole multiple of $500,000 in excess thereof;
and (iii) any prepayment of Base Rate Loans shall be in a principal amount of
$500,000 or a whole multiple of $100,000 in excess thereof. Each such notice
shall specify the date and amount of such prepayment and the Type(s) of Loans to
be prepaid. The Administrative Agent will promptly notify each Lender of its
receipt of each such notice, and of such Lender's Pro Rata Share of such
prepayment. If such notice is given by the Borrower, the Borrower shall make
such prepayment and the payment amount specified in such notice shall be due and
payable on the date specified therein. Any prepayment of a Eurodollar Rate Loan
shall be accompanied by all accrued interest thereon, together with any
additional amounts required pursuant to Section 3.05. Each such prepayment shall
be applied to the Loans of the Lenders in accordance with their respective Pro
Rata Shares.

        Unless a Default or Event of Default has occurred and is continuing or
would arise as a result thereof any payment or prepayment of the Loans may be
reborrowed by Borrower, subject to the terms and conditions hereof.

22

--------------------------------------------------------------------------------

        (b)    Mandatory Prepayments from Net Cash Proceeds.    

        (i)    If any portion of the Net Cash Proceeds realized by a Company
from any Triggering Sale (including any deferred purchase price therefore) has
not been Reinvested within one hundred eighty (180) days from the receipt by
such Company of such Net Cash Proceeds (including receipt of any deferred
payments for any such Triggering Sale or portion thereof, if and when received),
then on the Business Day following such one hundred eightieth (180th) day the
Commitments shall be permanently reduced, and the Loans shall be prepaid, in an
amount equal to the portion of the Reduction Amount that is not so Reinvested.
Net Cash Proceeds of a Disposition that equal, when aggregated with Net Cash
Proceeds of all Dispositions since the Closing Date, an amount less than the
Threshold Amount shall not be required to be used for mandatory prepayments or
commitment reductions pursuant to this Section 2.04(b).

        (ii)   If any Net Cash Proceeds are received by the MLP from an MLP
Offering, the Loans shall be prepaid by the Borrower immediately after receipt
of such Net Cash Proceeds by the MLP, in an amount equal to the amount of Net
Cash Proceeds received by the MLP from such MLP Offering; provided the
Commitments shall not be reduced by the amount of such prepayment; and provided
further that the Borrower, subject to the terms and conditions of this
Agreement, may reborrow all or any portion of the amount so prepaid.

        (iii)  Intentionally Omitted.

        (iv)  The prepayments and commitment reductions provided for in this
Section 2.04(b) shall be applied as follows, unless a Default or Event of
Default has occurred and is continuing or would arise as a result thereof
(whereupon the provisions of Section 2.11(d) shall apply): (A) first, as a
payment of all Unreimbursed Amounts then outstanding, until paid in full, and
(B) second, as a repayment of the principal balance of the Loans, until paid in
full or if a Default or Event of Default exists, as specified by the Agents or
the Required Banks.

        (c)    Mandatory Payments/Reductions.    If for any reason the
Outstanding Amount of all Loans and L/C Obligations at any time exceeds the
Aggregate Commitments then in effect, the Borrower shall immediately prepay
Loans and/or Cash Collateralize the L/C Obligations in an aggregate amount equal
to such excess.

        (d)    Prepayments: Interest/Consequential Loss.    All prepayments
under this Section 2.04 shall be made together with accrued interest to the date
of such prepayment on the principal amount prepaid and any amounts due under
Section 3.05.

        2.05    Reduction or Termination of Commitments.    The Borrower may,
upon notice to the Administrative Agent, terminate the Aggregate Commitments or
permanently reduce the Aggregate Commitments to an amount not less than the sum
of the Outstanding Amount of the then existing (i) principal amount of the Loans
and (ii) L/C Obligations; provided that (i) any such notice shall be received by
the Administrative Agent not later than 11:00 a.m., five Business Days prior to
the date of termination or reduction, and (ii) any such partial reduction shall
be in an aggregate amount of $3,000,000 or any whole multiple of $500,000 in
excess thereof. The Administrative Agent shall promptly notify the Lenders of
any such notice of reduction or termination. Once reduced in accordance with
this Section, the Aggregate Commitments may not be increased. Any reduction of
the Aggregate Commitments shall be applied to the Commitment of each Lender
according to its Pro Rata Share. All commitment fees on the portion of the
Commitment so terminated which have accrued to the effective date of any
termination of Commitments shall be paid on the effective date of such
termination.

        2.06    Repayment of Loans.    The Borrower shall repay to the Lenders
on the Maturity Date the aggregate principal amount of Loans outstanding on such
date.

23

--------------------------------------------------------------------------------

        2.07    Interest.    (a) Subject to the provisions of subsection
(b) below, (i) each Eurodollar Rate Loan shall bear interest on the outstanding
principal amount thereof for each Interest Period at a rate per annum equal to
the Eurodollar Rate for such Interest Period plus the Applicable Rate and
(ii) each Base Rate Loan shall bear interest on the outstanding principal amount
thereof from the applicable borrowing date at a rate per annum equal to the Base
Rate plus the Applicable Rate.

        (b)   While any Event of Default exists or after acceleration (i) the
Borrower shall pay interest on the principal amount of all outstanding
Obligations at a fluctuating interest rate per annum at all times equal to the
Default Rate to the fullest extent permitted by applicable Law, and (ii) accrued
and unpaid interest on past due amounts (including interest on past due
interest) shall be due and payable upon demand.

        (c)   Interest on each Loan shall be due and payable in arrears on each
Interest Payment Date applicable thereto and at such other times as may be
specified herein. Interest hereunder shall be due and payable in accordance with
the terms hereof before and after judgment, and before and after the
commencement of any proceeding under any Debtor Relief Law.

        (d)   If the designated rate applicable to any Borrowing exceeds the
Maximum Rate, the rate of interest on such Borrowing shall be limited to the
Maximum Rate, but any subsequent reductions in such designated rate shall not
reduce the rate of interest thereon below the Maximum Rate until the total
amount of interest accrued thereon equals the amount of interest which would
have accrued thereon if such designated rate had at all times been in effect. In
the event that at maturity (stated or by acceleration), or at final payment of
the Outstanding Amount of any Loans or L/C Obligations, the total amount of
interest paid or accrued is less than the amount of interest which would have
accrued if such designated rates had at all times been in effect, then, at such
time and to the extent permitted by Law, the Borrower shall pay an amount equal
to the difference between (a) the lesser of the amount of interest which would
have accrued if such designated rates had at all times been in effect and the
amount of interest which would have accrued if the Maximum Rate had at all times
been in effect, and (b) the amount of interest actually paid or accrued on such
Outstanding Amount.

        2.08    Fees.    (a) Commitment Fee.    The Borrower shall pay to the
Administrative Agent for the account of each Lender in accordance with its Pro
Rata Share, a commitment fee equal to the Applicable Rate times the actual daily
amount by which the Aggregate Commitments exceed the Outstanding Amount of
Loans. The commitment fee shall accrue at all times from the Restatement Date
until the Maturity Date and shall be due and payable quarterly in arrears on the
last Business Day of each March, June, September and December, commencing with
the first such date to occur after the Restatement Date, and on the Maturity
Date. The commitment fee shall be calculated quarterly in arrears, and if there
is any change in the Applicable Rate during any quarter, the actual daily amount
shall be computed and multiplied by the Applicable Rate separately for each
period during such quarter that such Applicable Rate was in effect. The
commitment fee shall accrue at all times, including at any time during which one
or more of the conditions in Article IV is not met.

        (b)    Arrangers' and Agent's Fees.    On the Restatement Date, the
Borrower shall pay certain fees to the Arrangers and Agents to be shared equally
between them and the Borrower shall pay certain fees to the Administrative Agent
for the Administrative Agent's own account as an administrative agency fee, in
the amounts and at the times specified in the letter agreement dated
November 20, 2003 (the "Agent/Arranger Fee Letter"), between the Borrower, the
Arrangers and the Agents. Such fees shall be fully earned when paid and shall be
nonrefundable for any reason whatsoever.

        2.09    Computation of Interest and Fees.    Computation of interest on
Base Rate Loans shall be calculated on the basis of a year of 365 or 366 days,
as the case may be, and the actual number of days elapsed. Computation of all
other types of interest and all fees shall be calculated on the basis of a

24

--------------------------------------------------------------------------------

year of 360 days and the actual number of days elapsed, which results in a
higher yield to the payee thereof than a method based on a year of 365 or
366 days. Interest shall accrue on each Loan for the day on which the Loan is
made, and shall not accrue on a Loan, or any portion thereof, for the day on
which the Loan or such portion is paid, provided that any Loan that is repaid on
the same day on which it is made shall bear interest for one day.

        2.10    Evidence of Debt.    (a) The Loans made by each Lender shall be
evidenced by one or more accounts or records maintained by such Lender and by
the Administrative Agent in the ordinary course of business. The accounts or
records maintained by the Administrative Agent and each Lender shall be
conclusive absent manifest error of the amount of the Loans made by the Lenders
to the Borrower and the interest and payments thereon. Any failure so to record
or any error in doing so shall not, however, limit or otherwise affect the
obligation of the Borrower hereunder to pay any amount owing with respect to the
Loans or the L/C Obligations. In the event of any conflict between the accounts
and records maintained by any Lender and the accounts and records of the
Administrative Agent in respect of such matters, the accounts and records of
such Lender shall control. Upon the request of any Lender made through the
Administrative Agent, such Lender's Loans may be evidenced by one or more Notes.
Each Lender may attach schedules to its Note(s) and endorse thereon the date,
Type (if applicable), amount and maturity of the applicable Loans and payments
with respect thereto.

        (b)   In addition to the accounts and records referred to in subsection
(a), each Lender and the Administrative Agent shall maintain in accordance with
its usual practice accounts or records evidencing the purchases and sales by
such Lender of participations in Letters of Credit. In the event of any conflict
between the accounts and records maintained by the Administrative Agent and the
accounts and records of any Lender in respect of such matters, the accounts and
records of the Administrative Agent shall control.

        2.11    Payments Generally.    (a) All payments to be made by the
Borrower shall be made without condition or deduction for any counterclaim,
defense, recoupment or setoff. Except as otherwise expressly provided herein,
all payments by the Borrower hereunder shall be made to the Administrative
Agent, for the account of the respective Lenders to which such payment is owed,
at the Administrative Agent's Office in Dollars and in immediately available
funds not later than 11:00 a.m., Houston, Texas time, on the date specified
herein. The Administrative Agent will promptly distribute to each Lender its Pro
Rata Share (or other applicable share as provided herein) of such payment in
like funds as received by wire transfer to such Lender's Lending Office. All
payments received by the Administrative Agent after 11:00 a.m., Houston, Texas
time, shall be deemed received on the next succeeding Business Day and any
applicable interest or fee shall continue to accrue.

        (b)   Subject to the definition of "Interest Period," if any payment to
be made by the Borrower shall come due on a day other than a Business Day,
payment shall be made on the next following Business Day, and such extension of
time shall be reflected in computing interest or fees, as the case may be.

        (c)   If no Default or Event of Default exists and if no order of
application is otherwise specified in the Loan Documents, payments and
prepayments of the Obligations shall be applied first to fees, second to accrued
interest then due and payable on the Outstanding Amount of Loans and L/C
Obligations, and then to the remaining Obligations in the order and manner as
Borrower may direct.

        (d)   If at any time insufficient funds are received by and available to
the Administrative Agent to pay fully the Obligations, or if a Default or Event
of Default exists, any payment or prepayment shall be applied in the following
order: (i) to the payment of enforcement expenses incurred by the Administrative
Agent, including Attorney Costs; (ii) to the ratable payment of all other fees,
expenses, and indemnities for which the Administrative Agent or Lenders have not
been paid or reimbursed in accordance with the Loan Documents (as used in this
Section 2.11(d)(ii) , a "ratable

25

--------------------------------------------------------------------------------

payment" for any Lender or the Administrative Agent shall be, on any date of
determination, that proportion which the portion of the total fees, expenses,
and indemnities owed to such Lender or the Administrative Agent bears to the
total aggregate fees and indemnities owed to all Lenders and the Administrative
Agent on such date of determination); (iii) to the ratable payment of accrued
and unpaid interest on the Outstanding Amount of Loans and the Outstanding
Amount of Obligations under Lender Hedging Agreements (it being understood that
for purposes of this clause (iii) the Outstanding Amount of Obligations under
Lender Hedging Agreements refers only to payments owing pursuant to Section 2(a)
of the 2002 Master Agreement form promulgated by the ISDA (or equivalent type
payment obligation if some other form of Swap Contract is in effect)(as used in
this Section 2.11(d)(iii), "ratable payment" means, for any Lender (or Lender
Affiliate, in the case of Lender Hedging Agreements), on any date of
determination, that proportion which the accrued and unpaid interest on the
Outstanding Amount of Loans and the Outstanding Amount of Obligations under
Lender Hedging Agreements owed to such Lender (or Lender Affiliate, in the case
of Lender Hedging Agreements) bears to the total accrued and unpaid interest on
the Outstanding Amount of Loans and the Outstanding Amount of Obligations under
Lender Hedging Agreements owed to all Lenders (and Affiliates, in the case of
Lender Hedging Agreements)); (iv) to the ratable payment of the Outstanding
Amount of Loans and the Outstanding Amount of Obligations under Lender Hedging
Agreements (it being understood that for purposes of this clause (iv) the
Outstanding Amount of Obligations under Lender Hedging Agreements refers to
payments owing in connection with an Early Termination Payment as defined in the
2002 Master Agreement form promulgated by the ISDA (or equivalent type payment
obligation if some other form of Swap Contract is in effect)(as used in this
Section 2.11(d)(iv), "ratable payment" means for any Lender (or Lender
Affiliate, in the case of Lender Hedging Agreements), on any date of
determination, that proportion which the Outstanding Amount of Loans and the
Outstanding Amount of Obligations under Lender Hedging Agreements owed to such
Lender (or Lender Affiliate, in the case of Lender Hedging Agreements) bears to
the Outstanding Amount of Loans owed to all Lenders)(and Affiliates, in the case
of Lender Hedging Agreements)); (v) to Cash Collateralize the Letters of Credit;
and (vi) to the payment of the remaining Obligations, if any, in the order and
manner the Required Lenders deem appropriate.

        (e)   Unless the Borrower or any Lender has notified the Administrative
Agent prior to the date any payment is required to be made by it to the
Administrative Agent hereunder, that the Borrower or such Lender, as the case
may be, will not make such payment, the Administrative Agent may assume that the
Borrower or such Lender, as the case may be, has timely made such payment and
may (but shall not be so required to), in reliance thereon, make available a
corresponding amount to the Person entitled thereto. If and to the extent that
such payment was not in fact made to the Administrative Agent in immediately
available funds, then:

        (i)    if the Borrower failed to make such payment, each Lender shall
forthwith on demand repay to the Administrative Agent the portion of such
assumed payment that was made available to such Lender in immediately available
funds, together with interest thereon in respect of each day from and including
the date such amount was made available by the Administrative Agent to such
Lender to the date such amount is repaid to the Administrative Agent in
immediately available funds, at the Federal Funds Rate from time to time in
effect; and

        (ii)   if any Lender failed to make such payment, such Lender shall
forthwith on demand pay to the Administrative Agent the amount thereof in
immediately available funds, together with interest thereon for the period from
the date such amount was made available by the Administrative Agent to the
Borrower to the date such amount is recovered by the Administrative Agent (the
"Compensation Period") at a rate per annum equal to the Federal Funds Rate from
time to time in effect. If such Lender pays such amount to the

26

--------------------------------------------------------------------------------

Administrative Agent, then such amount shall constitute such Lender's Loan,
included in the applicable Borrowing. If such Lender does not pay such amount
forthwith upon the Administrative Agent's demand therefor, the Administrative
Agent may make a demand therefor upon the Borrower, and the Borrower shall pay
such amount to the Administrative Agent, together with interest thereon for the
Compensation Period at a rate per annum equal to the rate of interest applicable
to the applicable Borrowing. Nothing herein shall be deemed to relieve any
Lender from its obligation to fulfill its Commitment or to prejudice any rights
which the Administrative Agent or the Borrower may have against any Lender as a
result of any default by such Lender hereunder.

        A notice of the Administrative Agent to any Lender with respect to any
amount owing under this subsection (e) shall be conclusive, absent manifest
error.

        (f)    If any Lender makes available to the Administrative Agent funds
for any Loan to be made by such Lender as provided in the foregoing provisions
of this Article II, and the conditions to the applicable Borrowing set forth in
Article IV are not satisfied or waived in accordance with the terms hereof, the
Administrative Agent shall return such funds (in like funds as received from
such Lender) to such Lender, without interest.

        (g)   The obligations of the Lenders hereunder to make Loans are several
and not joint. The failure of any Lender to make any Loan on any date required
hereunder shall not relieve any other Lender of its corresponding obligation to
do so on such date, and no Lender shall be responsible for the failure of any
other Lender to so make its Loan or purchase its participation.

        (h)   Nothing herein shall be deemed to obligate any Lender to obtain
the funds for any Loan in any particular place or manner or to constitute a
representation by any Lender that it has obtained or will obtain the funds for
any Loan in any particular place or manner.

        2.12    Sharing of Payments.    If, other than as expressly provided
elsewhere herein, any Lender shall obtain on account of the Loans made by it, or
the participations in the L/C Obligations, any payment (whether voluntary,
involuntary, through the exercise of any right of set-off, or otherwise) in
excess of its ratable share (or other share contemplated hereunder) thereof,
such Lender shall immediately (a) notify the Administrative Agent, of such fact,
and (b) purchase from the other Lenders such participations in the Loans made by
them, and/or such subparticipations in the participations in L/C Obligations
held by them as shall be necessary to cause such purchasing Lender to share the
excess payment in respect of such Loan or such participations, as the case may
be, pro rata with each of them; provided, however, that if all or any portion of
such excess payment is thereafter recovered from the purchasing Lender, such
purchase shall to that extent be rescinded and each other Lender shall repay to
the purchasing Lender the purchase price paid therefor, together with an amount
equal to such paying Lender's ratable share (according to the proportion of
(i) the amount of such paying Lender's required repayment to (ii) the total
amount so recovered from the purchasing Lender) of any interest or other amount
paid or payable by the purchasing Lender in respect of the total amount so
recovered. The Borrower agrees that any Lender so purchasing a participation
from another Lender may, to the fullest extent permitted by law, exercise all
its rights of payment (including the right of set-off, but subject to
Section 10.09) with respect to such participation as fully as if such Lender
were the direct creditor of the Borrower in the amount of such participation.
The Administrative Agent will keep records (which shall be conclusive and
binding in the absence of manifest error) of participations purchased under this
Section and will in each case notify the Lenders following any such purchases or
repayments. Each Lender that purchases a participation pursuant to this Section
shall from and after such purchase have the right to give all notices, requests,
demands, directions and other communications under this Agreement with respect
to the portion of the Obligations purchased to the same extent as though the
purchasing Lender were the original owner of the Obligations purchased.

27

--------------------------------------------------------------------------------

        2.13    Priority of Hedging Obligations and Banking Service
Obligations.    Any amounts received in satisfaction of any Obligations arising
under the Loan Documents, including, without limitation, Obligations under this
Agreement, Obligations under any Lender Hedging Agreement and Obligations in
connection with any Banking Services, shall rank pari passu in right of payment
and shall be used to repay such Obligations on a pro rata basis, unless
specified otherwise in Section 2.11(d).

        2.14    Letters of Credit.    (a) The Letter of Credit Commitment.

        (i)    Subject to the terms and conditions set forth herein, (A) the L/C
Issuer agrees, in reliance upon the agreements of the other Lenders set forth in
this Section 2.14, (1) from time to time on any Business Day during the period
from the Restatement Date until the Letter of Credit Expiration Date, to issue
Letters of Credit for the account of the Borrower or its Subsidiaries, and to
amend or renew Letters of Credit previously issued by it, in accordance with
subsection (b) below, and (2) to honor drafts under the Letters of Credit; and
(B) the Lenders severally agree to participate in Letters of Credit issued for
the account of the Borrower and its Subsidiaries; provided that the L/C Issuer
shall not be obligated to make any L/C Credit Extension with respect to any
Letter of Credit, and no Lender shall be obligated to participate in, any Letter
of Credit if as of the date of such L/C Credit Extension, (x) the Outstanding
Amount of all L/C Obligations and all Loans would exceed the Aggregate
Commitments, (y) the aggregate Outstanding Amount of the Loans of any Lender,
plus such Lender's Pro Rata Share of the Outstanding Amount of all L/C
Obligations would exceed such Lender's Commitment, or (z) the Outstanding Amount
of the L/C Obligations would exceed the Letter of Credit Sublimit. Within the
foregoing limits, and subject to the terms and conditions hereof, the Borrower's
ability to obtain Letters of Credit shall be fully revolving, and accordingly
the Borrower may, during the foregoing period, obtain Letters of Credit to
replace Letters of Credit that have expired or that have been drawn upon and
reimbursed.

        (ii)   The L/C Issuer shall be under no obligation to issue any Letter
of Credit if:

        (A)  any order, judgment or decree of any Governmental Authority or
arbitrator shall by its terms purport to enjoin or restrain the L/C Issuer from
issuing such Letter of Credit, or any Law applicable to the L/C Issuer or any
request or directive (whether or not having the force of law) from any
Governmental Authority with jurisdiction over the L/C Issuer shall prohibit, or
request that the L/C Issuer refrain from, the issuance of letters of credit
generally or such Letter of Credit in particular or shall impose upon the L/C
Issuer with respect to such Letter of Credit any restriction, reserve or capital
requirement (for which the L/C Issuer is not otherwise compensated hereunder)
not in effect on the Closing Date, or shall impose upon the L/C Issuer any
unreimbursed loss, cost or expense which was not applicable on the Closing Date
and which the L/C Issuer in good faith deems material to it;

        (B)  subject to Section 2.14(b)(iii), the expiry date of such requested
Letter of Credit would occur more than twelve months after the date of issuance
or last renewal, unless the Required Lenders have approved such expiry date;

        (C)  the expiry date of such requested Letter of Credit would occur
after the Letter of Credit Expiration Date, unless all the Lenders have approved
such expiry date;

        (D)  the issuance of such Letter of Credit would violate one or more
policies of the L/C Issuer generally applicable to all borrowers; or

        (E)  such Letter of Credit is in a face amount less than $100,000, or is
to be used for a purpose other than as described in Section 6.12 or is
denominated in a currency other than Dollars.

28

--------------------------------------------------------------------------------

        (iii)  The L/C Issuer shall be under no obligation to amend any Letter
of Credit if (A) the L/C Issuer would have no obligation at such time to issue
such Letter of Credit in its amended form under the terms hereof, or (B) the
beneficiary of such Letter of Credit does not accept the proposed amendment to
such Letter of Credit.

        (b)   Procedures for Issuance and Amendment of Letters of Credit;
Evergreen Letters of Credit.

        (i)    Each Letter of Credit shall be issued or amended, as the case may
be, upon the request of the Borrower delivered to the L/C Issuer (with a copy to
the Administrative Agent) in the form of a Letter of Credit Application,
appropriately completed and signed by a Responsible Officer of the Borrower.
Such Letter of Credit Application must be received by the L/C Issuer and the
Administrative Agent not later than 11:00 a.m., New York time, at least two
Business Days (or such later date and time as the L/C Issuer may agree in a
particular instance in its sole discretion) prior to the proposed issuance date
or date of amendment, as the case may be. In the case of a request for an
initial issuance of a Letter of Credit, such Letter of Credit Application shall
specify in form and detail satisfactory to the L/C Issuer: (A) the proposed
issuance date of the requested Letter of Credit (which shall be a Business Day);
(B) the amount thereof; (C) the expiry date thereof; (D) the name and address of
the beneficiary thereof; (E) the documents to be presented by such beneficiary
in case of any drawing thereunder; (F) the full text of any certificate to be
presented by such beneficiary in case of any drawing thereunder; and (G) such
other matters as the L/C Issuer may require. In the case of a request for an
amendment of any outstanding Letter of Credit, such Letter of Credit Application
shall specify in form and detail satisfactory to the L/C Issuer (A) the Letter
of Credit to be amended; (B) the proposed date of amendment thereof (which shall
be a Business Day); (C) the nature of the proposed amendment; and (D) such other
matters as the L/C Issuer may require.

        (ii)   Promptly after receipt of any Letter of Credit Application, the
L/C Issuer will confirm with the Administrative Agent (by telephone or in
writing) that the Administrative Agent has received a copy of such Letter of
Credit Application from the Borrower and, if not, the L/C Issuer will provide
the Administrative Agent with a copy thereof. Upon receipt by the L/C Issuer of
confirmation from the Administrative Agent that the requested issuance or
amendment is permitted in accordance with the terms hereof, then, subject to the
terms and conditions hereof, the L/C Issuer shall, on the requested date, issue
a Letter of Credit for the account of the Borrower or enter into the applicable
amendment, as the case may be, in each case in accordance with the L/C Issuer's
usual and customary business practices. Immediately upon the issuance of each
Letter of Credit, each Lender shall be deemed to, and hereby irrevocably and
unconditionally agrees to, purchase from the L/C Issuer a participation in such
Letter of Credit in an amount equal to the product of such Lender's Pro Rata
Share times the amount of such Letter of Credit.

        (iii)  If the Borrower so requests in any applicable Letter of Credit
Application, the L/C Issuer may, in it sole and absolute discretion, agree to
issue a Letter of Credit that has automatic renewal provisions (each, an
"Evergreen Letter of Credit"); provided that any such Evergreen Letter of Credit
must permit the L/C Issuer to prevent any such renewal at least once in each
twelve-month period (commencing with the date of issuance of such Letter of
Credit) by giving prior notice to the beneficiary thereof not later than a day
(the "Nonrenewal Notice Date") in each such twelve-month period to be agreed
upon at the time such Letter of Credit is issued. Unless otherwise directed by
the L/C Issuer, the Borrower shall not be required to make a specific request to
the L/C Issuer for any such renewal. Once an Evergreen Letter of Credit has been
issued, the Lenders shall be deemed to have authorized (but may not require) the
L/C Issuer to permit the renewal of such Letter of Credit at any

29

--------------------------------------------------------------------------------

time to a date not later than the Letter of Credit Expiration Date; provided,
however, that the L/C Issuer shall not permit any such renewal if it has
received notice on or before the Business Day immediately preceding the
Nonrenewal Notice Date (1) from the Administrative Agent that the Required
Lenders have elected not to permit such renewal or (2) from any Lender stating
that one or more of the applicable conditions specified in Section 4.03 is not
then satisfied and directing the L/C Issuer not to permit such renewal.
Notwithstanding anything to the contrary contained herein, the L/C Issuer shall
have no obligation to permit the renewal of any Evergreen Letter of Credit at
any time.

        (iv)  Promptly after its delivery of any Letter of Credit or any
amendment to a Letter of Credit to an advising bank with respect thereto or to
the beneficiary thereof, the L/C Issuer will also deliver to the Borrower and
the Administrative Agent a true and complete copy of such Letter of Credit or
amendment.

        (c)    Drawings and Reimbursements; Funding of Participations.    

        (i)    Upon any drawing under any Letter of Credit, the L/C Issuer shall
notify the Borrower and the Administrative Agent thereof. Not later than
11:00 a.m., New York time, on the date of any payment by the L/C Issuer under a
Letter of Credit (each such date, an "Honor Date"), the Borrower shall reimburse
the L/C Issuer through the Administrative Agent in an amount equal to the amount
of such drawing. If the Borrower fails to so reimburse the L/C Issuer by such
time, the Administrative Agent shall promptly notify each Lender of the Honor
Date, the amount of the unreimbursed drawing (the "Unreimbursed Amount"), and
such Lender's Pro Rata Share thereof. In such event, the Borrower shall be
deemed to have requested a Borrowing of Base Rate Loans to be disbursed on the
Honor Date in an amount equal to the Unreimbursed Amount, without regard to the
minimum and multiples specified in Section 2.03 for the principal amount of Base
Rate Loans, but subject to the amount of the unutilized portion of the Aggregate
Commitments and the conditions set forth in Section 4.03 (other than the
delivery of a Loan Notice). Any notice given by the L/C Issuer or the
Administrative Agent pursuant to this Section 2.14(c) (i) may be given by
telephone if immediately confirmed in writing; provided that the lack of such an
immediate confirmation shall not affect the conclusiveness or binding effect of
such notice.

        (ii)   Each Lender (including the Lender acting as L/C Issuer) shall
upon any notice pursuant to Section 2.14(c)(i) make funds available to the
Administrative Agent for the account of the L/C Issuer at the Administrative
Agent's Office in an amount equal to its Pro Rata Share of the Unreimbursed
Amount not later than 1:00 p.m., New York time, on the Business Day specified in
such notice by the Administrative Agent, whereupon, subject to the provisions of
Section 2.14(c)(iii), each Lender that so makes funds available shall be deemed
to have made a Base Rate Loan to the Borrower in such amount. The Administrative
Agent shall remit the funds so received to the L/C Issuer.

        (iii)  With respect to any Unreimbursed Amount that is not fully
refinanced by a Borrowing of Base Rate Loans because the conditions set forth in
Section 4.03 cannot be satisfied or for any other reason, the Borrower shall be
deemed to have incurred from the L/C Issuer an L/C Borrowing in the amount of
the Unreimbursed Amount that is not so refinanced, which L/C Borrowing shall be
due and payable on demand (together with interest) and shall bear interest at
the Default Rate. In such event, each Lender's payment to the Administrative
Agent for the account of the L/C Issuer pursuant to Section 2.14(c) (ii) shall
be deemed payment in respect of its participation in such L/C Borrowing and
shall constitute an L/C Advance from such Lender in satisfaction of its
participation obligation under this Section 2.14.

30

--------------------------------------------------------------------------------

        (iv)  Until each Lender funds its Loan or L/C Advance pursuant to this
Section 2.14(c) to reimburse the L/C Issuer for any amount drawn under any
Letter of Credit, interest in respect of such Lender's Pro Rata Share of such
amount shall be solely for the account of the L/C Issuer.

        (v)   Each Lender's obligation to make Loans or L/C Advances to
reimburse the L/C Issuer for amounts drawn under Letters of Credit, as
contemplated by this Section 2.14(c), shall be absolute and unconditional and
shall not be affected by any circumstance, including (A) any set-off,
counterclaim, recoupment, defense or other right which such Lender may have
against the L/C Issuer, the Borrower or any other Person for any reason
whatsoever; (B) the occurrence or continuance of a Default or Event of Default,
or (C) any other occurrence, event or condition, whether or not similar to any
of the foregoing. Any such reimbursement shall not relieve or otherwise impair
the obligation of the Borrower to reimburse the L/C Issuer for the amount of any
payment made by the L/C Issuer under any Letter of Credit, together with
interest as provided herein.

        (vi)  If any Lender fails to make available to the Administrative Agent
for the account of the L/C Issuer any amount required to be paid by such Lender
pursuant to the foregoing provisions of this Section 2.14(c) by the time
specified in Section 2.14(c)(ii), the L/C Issuer shall be entitled to recover
from such Lender (acting through the Administrative Agent), on demand, such
amount with interest thereon for the period from the date such payment is
required to the date on which such payment is immediately available to the L/C
Issuer at a rate per annum equal to the Federal Funds Rate from time to time in
effect. A certificate of the L/C Issuer submitted to any Lender (through the
Administrative Agent) with respect to any amounts owing under this clause (vi)
shall be conclusive absent manifest error.

        (d)    Repayment of Participations.    

        (i)    At any time after the L/C Issuer has made a payment under any
Letter of Credit and has received from any Lender such Lender's L/C Advance in
respect of such payment in accordance with Section 2.14(c), if the
Administrative Agent receives for the account of the L/C Issuer any payment
related to such Letter of Credit (whether directly from the Borrower or
otherwise, including proceeds of cash Collateral applied thereto by the
Administrative Agent), or any payment of interest thereon, the Administrative
Agent will distribute to such Lender its Pro Rata Share thereof in the same
funds as those received by the Administrative Agent.

        (ii)   If any payment received by the Administrative Agent for the
account of the L/C Issuer pursuant to Section 2.14(c)(i) is required to be
returned, each Lender shall pay to the Administrative Agent for the account of
the L/C Issuer its Pro Rata Share thereof on demand of the Administrative Agent,
plus interest thereon from the date of such demand to the date such amount is
returned by such Lender, at a rate per annum equal to the Federal Funds Rate
from time to time in effect.

        (e)    Obligations Absolute.    The obligation of the Borrower to
reimburse the L/C Issuer for each drawing under each Letter of Credit, and to
repay each L/C Borrowing and each drawing under a Letter of Credit that is
refinanced by a Borrowing of Loans, shall be absolute, unconditional and
irrevocable, and shall be paid strictly in accordance with the terms of this
Agreement under all circumstances, including the following:

        (i)    any lack of validity or enforceability of such Letter of Credit,
this Agreement, or any other agreement or instrument relating thereto;

        (ii)   the existence of any claim, counterclaim, set-off, defense or
other right that the Borrower may have at any time against any beneficiary or
any transferee of such Letter of Credit (or any Person for whom any such
beneficiary or any such transferee may be acting),

31

--------------------------------------------------------------------------------

the L/C Issuer or any other Person, whether in connection with this Agreement,
the transactions contemplated hereby or by such Letter of Credit or any
agreement or instrument relating thereto, or any unrelated transaction;

        (iii)  any draft, demand, certificate or other document presented under
such Letter of Credit proving to be forged, fraudulent, invalid or insufficient
in any respect or any statement therein being untrue or inaccurate in any
respect; or any loss or delay in the transmission or otherwise of any document
required in order to make a drawing under such Letter of Credit;

        (iv)  any payment by the L/C Issuer under such Letter of Credit against
presentation of a draft or certificate that does not strictly comply with the
terms of such Letter of Credit; or any payment made by the L/C Issuer under such
Letter of Credit to any Person purporting to be a trustee in bankruptcy,
debtor-in-possession, assignee for the benefit of creditors, liquidator,
receiver or other representative of or successor to any beneficiary or any
transferee of such Letter of Credit, including any arising in connection with
any proceeding under any Debtor Relief Law; or

        (v)   any other circumstance or happening whatsoever, whether or not
similar to any of the foregoing, that might otherwise constitute a defense
available to, or a discharge of, the Borrower.

        The Borrower shall promptly examine a copy of each Letter of Credit and
each amendment thereto that is delivered to it and, in the event of any claim of
noncompliance with the Borrower's instructions or other irregularity, the
Borrower will immediately notify the L/C Issuer. The Borrower shall be
conclusively deemed to have waived any such claim against the L/C Issuer and its
correspondents unless such notice is given as aforesaid.

        (f)    Role of L/C Issuer.    Each Lender and the Borrower agree that,
in paying any drawing under a Letter of Credit, the L/C Issuer shall not have
any responsibility to obtain any document (other than any sight draft,
certificates and documents expressly required by the Letter of Credit) or to
ascertain or inquire as to the validity or accuracy of any such document or the
authority of the Person executing or delivering any such document. No
Agent-Related Person nor any of the respective correspondents, participants or
assignees of the L/C Issuer shall be liable to any Lender for (i) any action
taken or omitted in connection herewith at the request or with the approval of
the Lenders or the Required Lenders, as applicable; (ii) any action taken or
omitted in the absence of gross negligence or willful misconduct; or (iii) the
due execution, effectiveness, validity or enforceability of any document or
instrument related to any Letter of Credit or Letter of Credit Application. The
Borrower hereby assumes all risks of the acts or omissions of any beneficiary or
transferee with respect to its use of any Letter of Credit; provided, however,
that this assumption is not intended to, and shall not, preclude the Borrower's
pursuing such rights and remedies as it may have against the beneficiary or
transferee at law or under any other agreement. No Agent-Related Person, nor any
of the respective correspondents, participants or assignees of the L/C Issuer,
shall be liable or responsible for any of the matters described in clauses
(i) through (v) of Section 2.14(e); provided, however, that anything in such
clauses to the contrary notwithstanding, the Borrower may have a claim against
the L/C Issuer, and the L/C Issuer may be liable to the Borrower, to the extent,
but only to the extent, of any direct, as opposed to consequential or exemplary,
damages suffered by the Borrower which the Borrower proves were caused by the
L/C Issuer's willful misconduct or gross negligence or the L/C Issuer's willful
failure to pay under any Letter of Credit after the presentation to it by the
beneficiary of a sight draft and certificate(s) strictly complying with the
terms and conditions of a Letter of Credit. In furtherance and not in limitation
of the foregoing, the L/C Issuer may accept documents that appear on their face
to be in order, without responsibility for further investigation, regardless of
any notice or information to the contrary, and the L/C Issuer shall not be
responsible for the validity or sufficiency of any

32

--------------------------------------------------------------------------------

instrument transferring or assigning or purporting to transfer or assign a
Letter of Credit or the rights or benefits thereunder or proceeds thereof, in
whole or in part, which may prove to be invalid or ineffective for any reason.

        (g)    Cash Collateral.    Upon the request of the Administrative Agent,
(i) if the L/C Issuer has honored any full or partial drawing request under any
Letter of Credit and such drawing has resulted in an L/C Borrowing, or (ii) if,
as of the Letter of Credit Expiration Date, any Letter of Credit may for any
reason remain outstanding and partially or wholly undrawn, the Borrower shall
immediately Cash Collateralize the then Outstanding Amount of all L/C
Obligations (in an amount equal to such Outstanding Amount). The Borrower hereby
grants the Administrative Agent, for the benefit of the L/C Issuer and the
Lenders, a Lien on all such cash and deposit accounts at any Lender.

        (h)    Applicability of ISP98.    Unless otherwise expressly agreed by
the L/C Issuer and the Borrower when a Letter of Credit is issued (including any
such agreement applicable to an Existing Letter of Credit), the rules of the
"International Standby Practices 1998" published by the Institute of
International Banking Law & Practice (or such later version thereof as may be in
effect at the time of issuance) shall apply to each Letter of Credit.

        (i)    Letter of Credit Fees.    The Borrower shall pay to the
Administrative Agent for the account of each Lender in accordance with its Pro
Rata Share a Letter of Credit fee for each Letter of Credit issued equal to the
Applicable Rate times the actual daily undrawn amount under each Letter of
Credit. Such fee for each Letter of Credit shall be due and payable on the last
Business Day of each March, June, September and December, commencing with the
first such date to occur after the issuance of such Letter of Credit, and on the
Letter of Credit Expiration Date. If there is any change in the Applicable Rate
during any quarter, the actual daily undrawn amount of each Letter of Credit
shall be computed and multiplied by the Applicable Rate separately for each
period during such quarter that such Applicable Rate was in effect.

        (j)    Fronting Fee and Documentary and Processing Charges Payable to
L/C Issuer.    The Borrower shall pay directly to the L/C Issuer for its own
account a fronting fee in an amount with respect to each Letter of Credit issued
equal to the greater of (i) $500 or (ii) 1/4 of 1% calculated on the face amount
thereof. In addition, the Borrower shall pay directly to the L/C Issuer for its
own account the customary issuance, presentation, amendment and other processing
fees, and other standard costs and charges, of the L/C Issuer relating to
letters of credit as from time to time in effect. Such fees and charges are due
and payable on demand and are nonrefundable.

        (k)    Conflict with Letter of Credit Application.    In the event of
any conflict between the terms hereof and the terms of any Letter of Credit
Application, the terms hereof shall control.

Remainder of this page intentionally left blank.

33

--------------------------------------------------------------------------------

ARTICLE III.
TAXES, YIELD PROTECTION AND ILLEGALITY

        3.01    Taxes.    

        (a)   Any and all payments by the Borrower to or for the account of the
Administrative Agent or any Lender under any Loan Document shall be made free
and clear of and without deduction for any and all present or future taxes,
duties, levies, imposts, deductions, assessments, fees, withholdings or similar
charges, and all liabilities with respect thereto, excluding, in the case of the
Administrative Agent and each Lender, taxes imposed on or measured by its net
income, and franchise taxes imposed on it (in lieu of net income taxes), by the
jurisdiction (or any political subdivision thereof) under the Laws of which the
Administrative Agent or such Lender, as the case may be, is organized or
maintains its Lending Office (all such non-excluded taxes, duties, levies,
imposts, deductions, assessments, fees, withholdings or similar charges, and
liabilities being hereinafter referred to as "Taxes"). If the Borrower shall be
required by any Laws to deduct any Taxes from or in respect of any sum payable
under any Loan Document to the Administrative Agent or any Lender, (i) the sum
payable shall be increased as necessary so that after making all required
deductions (including deductions applicable to additional sums payable under
this Section), each of the Administrative Agent and such Lender receives an
amount equal to the sum it would have received had no such deductions been made,
(ii) the Borrower shall make such deductions, (iii) the Borrower shall pay the
full amount deducted to the relevant taxation authority or other authority in
accordance with applicable Laws, and (iv) within 30 days after the date of such
payment, the Borrower shall furnish to the Administrative Agent (which shall
forward the same to such Lender) the original or a certified copy of a receipt
evidencing payment thereof.

        (b)   In addition, the Borrower agrees to pay any and all present or
future stamp, court or documentary taxes and any other excise or property taxes
or charges or similar levies which arise from any payment made under any Loan
Document or from the execution, delivery, performance, enforcement or
registration of, or otherwise with respect to, any Loan Document (hereinafter
referred to as "Other Taxes").

        (c)   If the Borrower shall be required to deduct or pay any Taxes or
Other Taxes from or in respect of any sum payable under any Loan Document to the
Administrative Agent or any Lender, the Borrower shall also pay to the
Administrative Agent (for the account of such Lender) or to such Lender, at the
time interest is paid, such additional amount that such Lender specifies as
necessary to preserve the after-tax yield (after factoring in all taxes,
including taxes imposed on or measured by net income) such Lender would have
received if such Taxes or Other Taxes had not been imposed.

        (d)   The Borrower agrees to indemnify the Administrative Agent and each
Lender for (i) the full amount of Taxes and Other Taxes (including any Taxes or
Other Taxes imposed or asserted by any jurisdiction on amounts payable under
this Section) paid by the Administrative Agent and such Lender, (ii) amounts
payable under Section 3.01(c) and (iii) any liability (including penalties,
interest and expenses) arising therefrom or with respect thereto. Payment under
this subsection (d) shall be made within 30 days after the date the Lender or
the Administrative Agent makes a demand therefor.

        3.02    Illegality.    If any Lender determines that any Law has made it
unlawful, or that any Governmental Authority has asserted that it is unlawful,
for any Lender or its applicable Lending Office to make, maintain or fund
Eurodollar Rate Loans, or materially restricts the authority of such Lender to
purchase or sell, or to take deposits of, Dollars in the applicable offshore
Dollar market, or to determine or charge interest rates based upon the
Eurodollar Rate, then, on notice thereof by such Lender to the Borrower through
the Administrative Agent, any obligation of such Lender to make or continue
Eurodollar Rate Loans or to convert Base Rate Loans to Eurodollar Rate Loans
shall be

34

--------------------------------------------------------------------------------

suspended until such Lender notifies the Administrative Agent and the Borrower
that the circumstances giving rise to such determination no longer exist. Upon
receipt of such notice, the Borrower shall, upon demand from such Lender (with a
copy to the Administrative Agent), prepay or, if applicable, convert all
Eurodollar Rate Loans of such Lender to Base Rate Loans, either on the last day
of the Interest Period thereof, if such Lender may lawfully continue to maintain
such Eurodollar Rate Loans to such day, or immediately, if such Lender may not
lawfully continue to maintain such Eurodollar Rate Loans. Upon any such
prepayment or conversion, the Borrower shall also pay interest on the amount so
prepaid or converted. Each Lender agrees to designate a different Lending Office
if such designation will avoid the need for such notice and will not, in the
reasonable judgment of such Lender, otherwise be materially disadvantageous to
such Lender.

        3.03    Inability to Determine Rates.    If the Administrative Agent
determines in connection with any request for a Eurodollar Rate Loan or a
conversion to or continuation thereof that (a) Dollar deposits are not being
offered to banks in the applicable offshore Dollar market for the applicable
amount and Interest Period of such Eurodollar Rate Loan, or adequate and
reasonable means do not exist for determining the Eurodollar Rate for such
Eurodollar Rate Loan, or (b) if the Required Lenders determine and notify the
Administrative Agent that the Eurodollar Rate for such Eurodollar Rate Loan does
not adequately and fairly reflect the cost to the Lenders of funding such
Eurodollar Rate Loan, then the Administrative Agent will promptly notify the
Borrower and all Lenders. Thereafter, the obligation of the Lenders to make or
maintain Eurodollar Rate Loans shall be suspended until the Administrative Agent
revokes such notice. Upon receipt of such notice, the Borrower may revoke any
pending request for a Borrowing, conversion or continuation of Eurodollar Rate
Loans or, failing that, will be deemed to have converted such request into a
request for a Borrowing of Base Rate Loans in the amount specified therein.

        3.04    Increased Cost and Reduced Return; Capital Adequacy; Reserves on
Eurodollar Rate Loans.    

        (a)   If any Lender determines that as a result of a Change in Law, or
such Lender's compliance therewith, there shall be any increase in the cost to
such Lender of agreeing to make or making, funding or maintaining Eurodollar
Rate Loans, or a reduction in the amount received or receivable by such Lender
in connection with any of the foregoing (excluding for purposes of this
subsection (a) any such increased costs or reduction in amount resulting from
(i) Taxes or Other Taxes (as to which Section 3.01 shall govern), (ii) changes
in the basis of taxation of overall net income or overall gross income by the
United States or any foreign jurisdiction or any political subdivision of either
thereof under the Laws of which such Lender is organized or has its Lending
Office, and (iii) reserve requirements contemplated by Section 3.04(c) utilized,
as to Eurodollar Rate Loans, in the determination of the Eurodollar Rate), then
from time to time upon demand of such Lender (with a copy of such demand to the
Administrative Agent), the Borrower shall pay to such Lender such additional
amounts as will compensate such Lender for such increased cost or reduction.

        (b)   If any Lender determines a Change In Law has the effect of
reducing the rate of return on the capital of such Lender or any corporation
controlling such Lender as a consequence of such Lender's obligations hereunder
(taking into consideration its policies with respect to capital adequacy and
such Lender's desired return on capital, then from time to time upon demand of
such Lender (with a copy of such demand to the Administrative Agent), the
Borrower shall pay to such Lender such additional amounts as will compensate
such Lender for such reduction.

        (c)   The Borrower shall pay to each Lender, as long as such Lender
shall be required under regulations of the Board to maintain reserves with
respect to liabilities or assets consisting of or including Eurocurrency funds
or deposits (currently known as "Eurocurrency liabilities"), additional costs on
the unpaid principal amount of each Eurodollar Rate Loan equal to the actual
costs of such reserves allocated to such Loan by such Lender (as determined by
such Lender in good faith,

35

--------------------------------------------------------------------------------

which determination shall be conclusive), which shall be due and payable on each
date on which interest is payable on such Loan, provided the Borrower shall have
received at least 15 days' prior notice (with a copy to the Administrative
Agent) of such additional interest from such Lender. If a Lender fails to give
notice 15 days prior to the relevant Interest Payment Date, such additional
interest shall be due and payable 15 days from receipt of such notice.

        3.05    Funding Losses.    Upon demand of any Lender (with a copy to the
Administrative Agent) from time to time, the Borrower shall promptly compensate
such Lender for and hold such Lender harmless from any loss, cost or expense
incurred by it as a result of:

        (a)   any continuation, conversion, payment or prepayment of any Loan
other than a Base Rate Loan on a day other than the last day of the Interest
Period for such Loan (whether voluntary, mandatory, automatic, by reason of
acceleration, or otherwise); or

        (b)   any failure by the Borrower (for a reason other than the failure
of such Lender to make a Loan) to prepay, borrow, continue or convert any Loan
other than a Base Rate Loan on the date or in the amount notified by the
Borrower; including any loss of anticipated profits and any loss or expense
arising from the liquidation or reemployment of funds obtained by it to maintain
such Loan or from fees payable to terminate the deposits from which such funds
were obtained. The Borrower shall also pay any customary administrative fees
charged by such Lender in connection with the foregoing.

        For purposes of calculating amounts payable by the Borrower to the
Lenders under this Section 3.05, each Lender shall be deemed to have funded each
Eurodollar Rate Loan made by it at the Eurodollar Rate for such Loan by a
matching deposit or other borrowing in the applicable offshore Dollar interbank
market for a comparable amount and for a comparable period, whether or not such
Eurodollar Rate Loan was in fact so funded.

        3.06    Matters Applicable to all Requests for Compensation.    A
certificate of the Administrative Agent or any Lender claiming compensation
under this Article III and setting forth the additional amount or amounts to be
paid to it hereunder shall be conclusive in the absence of manifest error. In
determining such amount, the Administrative Agent or such Lender may use any
reasonable averaging and attribution methods.

        3.07    Survival.    All of the Borrower's obligations under this
Article III shall survive termination of the Commitments and payment in full of
all the other Obligations.

Remainder of this page intentionally left blank.

36

--------------------------------------------------------------------------------

ARTICLE IV.
CONDITIONS PRECEDENT TO BORROWINGS

        4.01    Intentionally Omitted.    

        4.02    Conditions Precedent to Amendment and Restatement of
Agreement.    The amendment and restatement of this Agreement on the Restatement
Date is subject to, and will take effect upon, satisfaction of the following
conditions precedent on or prior to such date:

        (a)   Satisfactory completion of due diligence by the Arrangers,
including without limitation, receipt and review, with results satisfactory to
the Arrangers, of information regarding material contracts, property ownership,
organization structure, litigation, tax, accounting, insurance and environmental
matters (including Phase I and, if any, Phase II environmental studies related
to the American Central Acquisition and Shell Pipeline Acquisition) currently in
the Borrower's possession and relating to the American Central Acquisition and
Shell Pipeline Acquisition.

        (b)   Satisfactory evidence that the American Central Acquisition has
been (or contemporaneously with the funding of the Loans on the Restatement Date
will be) consummated for a purchase price not to exceed $38,750,000 (excluding
acquired working capital and fees/expenses associated therewith) and on terms
and conditions and pursuant to documentation satisfactory to the Agents in all
respects.

        (c)   The Administrative Agent's receipt of the following, each of which
shall be originals or facsimiles (followed promptly by originals) and unless
otherwise specified, each properly executed by an authorized officer of the
signing Loan Party, each dated the Restatement Date (or, in the case of
certificates of governmental officials, a recent date before the Restatement
Date), and each in form and substance satisfactory to the Agents and their legal
counsel:

        (i)    executed counterparts of this Agreement, the Guaranty from MW
Western, the Mortgage from MW Western covering the assets acquired by MW Western
in connection with the American Central Acquisition, an amendment to the pledge
agreement from Borrower pledging 100% of the equity in MW Western, the MarkWest
Parent Pledge Agreement, and all other Collateral Documents each dated as of the
Restatement Date;

        (ii)   Notes executed by the Borrower in favor of each Lender requesting
such Notes, each in a principal amount equal to such Lender's Commitment, each
dated as of the Restatement Date;

        (iii)  such certificates of resolutions or other action, incumbency
certificates and/or other certificates of officers of each Loan Party as the
Agents may require to establish the identities of and verify the authority and
capacity of each officer thereof authorized to act in connection with this
Agreement and the other Loan Documents to which such Loan Party is a party;

        (iv)  such evidence as the Agents may reasonably require to verify that
each Loan Party is duly organized or formed, validly existing, and in good
standing in the jurisdiction of its organization;

        (v)   a certificate signed by a Responsible Officer of the Borrower
certifying (A) that the representations and warranties contained in Article V
are true and correct in all respects on and as of the Restatement Date, (B) that
no Default or Event of Default has occurred and is continuing as of the
Restatement Date or will exist immediately after funding the Loan to finance the
American Central Acquisition, (C) since December 31, 2002 there has occurred no
material adverse change in (x) the business, assets, liabilities (actual or
contingent), operations, or condition (financial or otherwise) or prospects of
the Borrower and Guarantors, taken as a whole, or (y) any of the businesses,
assets or liabilities acquired or assumed or being acquired or assumed by the
Borrower or any of its Subsidiaries, (D) that as of the

37

--------------------------------------------------------------------------------

Restatement Date there are no material environmental or legal issues affecting
any Loan Party or any of the Collateral, (E) all necessary governmental and
third party approvals necessary or required for any Loan Party to enter into
this Agreement or any of the Loan Documents has been obtained, (F) there is no
litigation, investigation or proceeding known to and affecting the Borrower or
any Borrower Affiliate for which the Borrower is required to give notice
pursuant to Section 6.03(c) (or, if there is any such litigation, investigation
or proceeding, then a notice containing the information required by
Section 6.03(c) shall be given concurrently with the delivery of the certificate
given pursuant to this clause (v)), and (G) no action, suit, investigation or
proceeding is pending or threatened in any court or before any arbitrator or
governmental authority by or against the Borrower, any Guarantor, the General
Partner, or any of their respective properties, that (x) contests or seeks to
adversely affect the American Central Acquisition, or (y) could reasonably be
expected to materially and adversely affect the Borrower or any Guarantor, taken
as a whole, or (z) seeks to affect or pertains to any transaction contemplated
hereby or the ability of the Borrower or any Guarantor to perform its
obligations under the Loan Documents;

        (vi)  a certificate of a Responsible Officer (a) of the Borrower
demonstrating compliance with all financial covenants on a pro forma basis for
the quarter ended September 30, 2003, (b) of the Borrower as to the satisfaction
of all conditions specified in this Section 4.02 and Section 4.03, and
(c) providing copies of the following (A) pro forma financial statements of the
MLP on a consolidated basis after giving effect to the American Central
Acquisition and Shell Pipeline Acquisition for the period ended September 30,
2003, (B) a five-year financial forecast for the MLP pro forma after giving
effect to the American Central Acquisition and Shell Pipeline Acquisition, and
(C) such other financial information as the Agents may request;

        (vii) opinions from (A) Hogan & Hartson, L.L.P., counsel to each Loan
Party and the General Partner, in form and substance satisfactory to the Agents
and their counsel, and (B) Hall, Estill, Hardwick, Gable & Nelson, P.C., local
counsel to MW Western with respect to the deed of trust or mortgage executed by
MW Western;

        (viii) a letter from CT Corporation System, Inc., to accept service of
process in the State of Texas on behalf of MW Western;

        (ix)  a certificate of MarkWest Parent stating that no Default or Event
of Default exists under the Parent Credit Agreement or will exist immediately
after the closing of this Agreement as such credit agreements are amended and
restated on the Restatement Date; and

        (x)   such other assurances, certificates, documents, consents or
opinions as the Agents reasonably may require.

        (d)   Any fees due and payable at the Restatement Date shall have been
paid including, without limitation, payment of fees and expenses pursuant to a
fee letter between the Borrower and the Agents.

        (e)   The Borrower shall have paid Attorney Costs of the Administrative
Agent to the extent invoiced prior to, or on, the Restatement Date.

        (f)    Documents, executed by each Company that has assets or conducts
business, in appropriate form for recording, where necessary, together with:

        (i)    such Lien searches as the Administrative Agent shall have
requested, and such termination statements or other documents as may be
necessary to confirm that the Collateral is subject to no other Liens (other
than Permitted Liens) in favor of any Persons;

38

--------------------------------------------------------------------------------

        (ii)   funds sufficient to pay any filing or recording tax or fee in
connection with any and all UCC-1 financing statements or UCC-3 amendment
financing statements, or fees associated with the filing of the Mortgages or
amendments to Mortgages;

        (iii)  evidence that the Administrative Agent has been named as loss
payee under all policies of casualty insurance pertaining to the Collateral;

        (iv)  such consents, estoppels, subordination agreements and other
documents and instruments executed by landlords and other Persons party to
material contracts relating to any Collateral as to which the Administrative
Agent shall be granted a Lien for the benefit of the Lenders, as requested by
the Administrative Agent or any Lender;

        (v)   certificates evidencing all of the issued and outstanding shares
of capital stock, partnership interests, or membership interests pledged
pursuant thereto, which certificates shall in each case be accompanied by
undated stock powers duly executed in blank, or, if any securities pledged
pursuant thereto are uncertificated securities, confirmation and evidence
satisfactory to the Administrative Agent that the security interest in such
uncertificated securities has been transferred to and perfected by the
Administrative Agent for the benefit of the Lenders in accordance with the
Uniform Commercial Code; and

        (vi)  evidence that all other actions necessary or, in the opinion of
the Administrative Agent or the Lenders, desirable to perfect and protect the
first priority Lien created by the Collateral Documents (except to the extent
otherwise permitted hereunder), and to enhance the Administrative Agent's
ability to preserve and protect its interests in and access to the Collateral,
have been taken.

        (g)   The Administrative Agent's receipt (with sufficient copies for all
Lenders) of the certificate of formation of the Borrower, together with all
amendments, certified by an appropriate governmental officer in its jurisdiction
of organization, as well as any other information required by Section 326 of the
USA Patriot Act or necessary for the Agents or any Lender to verify the identity
of Borrower as required by Section 326 of the USA Patriot Act.

        The Agents shall notify the Borrower of the Restatement Date, and such
notice shall be conclusive and binding.

        4.03    Conditions to all Loans and L/C Credit Extension.    The
obligation of each Lender to honor any Borrowing Notice and the obligation of
the L/C Issuer to issue any Letter of Credit is subject to the following
conditions precedent:

        (a)   The representations and warranties of the Loan Parties contained
in Article V, or which are contained in any document furnished at any time under
or in connection herewith, including, but not limited to the Collateral
Documents, shall be true and correct in all material respects on and as of the
date of such Loan is made, continued or converted, as applicable, or such Letter
of Credit is issued except to the extent that such representations and
warranties specifically refer to an earlier date, in which case they shall be
true and correct as of such earlier date.

        (b)   No Default or Event of Default shall exist or would result from
such proposed Loan, continuation or conversion, or L/C Credit Extension.

        (c)   The Administrative Agent and, if applicable, the L/C Issuer, shall
have received a Request for Credit Extension and, if applicable, a Letter of
Credit Application in accordance with the requirements hereof.

        (d)   The Administrative Agent shall have received, in form and
substance reasonably satisfactory to it, such other assurances, certificates,
documents or consents related to the foregoing as the Administrative Agent or
the Required Lenders reasonably may require.

39

--------------------------------------------------------------------------------

        Each Request for Credit Extension submitted by the Borrower shall be
deemed to be a representation and warranty that the conditions specified in
Sections 4.03(a) and (b) have been satisfied on and as of the date of the
applicable Credit Extension.

        4.04    Conditions Precedent to Funding Loans for Shell Pipeline
Acquisition.    The obligation of each Lender to fund its portion of the Loans
to finance the Shell Pipeline Acquisition on the Shell Pipeline Funding
Conditions Effective Date shall be subject to satisfaction of the conditions
precedent set forth in Section 4.03 and to the following conditions precedent:

        (a)   Satisfactory evidence that the Shell Pipeline Acquisition has been
(or contemporaneously with the funding of the Loans on the Shell Pipeline
Funding Conditions Effective Date will be) consummated for a purchase price not
to exceed $23,300,000 (excluding acquired working capital and fees/expenses
associated therewith) and on terms and conditions and pursuant to documentation
satisfactory to the Agents in all respects.

        (b)   The Administrative Agent's receipt of the following, each of which
shall be originals or facsimiles (followed promptly by originals) and unless
otherwise specified, each properly executed by an authorized officer of the
signing Loan Party, each dated the Shell Pipeline Funding Conditions Effective
Date (or, in the case of certificates of governmental officials, a recent date
before the Shell Pipeline Funding Conditions Effective Date), and each in form
and substance satisfactory to the Agents and their legal counsel:

        (i)    executed counterparts of a Guaranty from MW Michigan, a Mortgage
from MW Michigan covering the assets being acquired in connection with the Shell
Pipeline Acquisition, an amendment to the pledge agreement from Borrower
pledging 100% of the equity in MW Michigan, and all other Collateral Documents
each dated as of the Shell Pipeline Funding Conditions Effective Date;

        (ii)   such certificates of resolutions or other action, incumbency
certificates and/or other certificates of officers of each Loan Party as the
Agents may require to establish the identities of and verify the authority and
capacity of each officer thereof authorized to act in connection with this
Agreement and the other Loan Documents to which such Loan Party is a party;

        (iii)  such evidence as the Agents may reasonably require to verify that
each Loan Party is duly organized or formed, validly existing, and in good
standing in the jurisdiction of its organization;

        (iv)  a certificate signed by a Responsible Officer of the Borrower
certifying (A) that the representations and warranties contained in Article V
are true and correct in all respects on and as of the Shell Pipeline Funding
Conditions Effective Date, (B) that no Default or Event of Default has occurred
and is continuing as of the Shell Pipeline Funding Conditions Effective Date or
will exist immediately after funding the Loan to finance the Shell Pipeline
Acquisition, (C) since December 31, 2002 there has occurred no material adverse
change in (x) the business, assets, liabilities (actual or contingent),
operations, or condition (financial or otherwise) or prospects of the Borrower
and Guarantors, taken as a whole, or (y) any of the businesses, assets or
liabilities acquired or assumed or being acquired or assumed by the Borrower or
any of its Subsidiaries, (D) that as of the Shell Pipeline Funding Conditions
Effective Date there are no material environmental or legal issues affecting any
Loan Party or any the Collateral, (E) all necessary governmental and third party
approvals necessary or required for any Loan Party to enter into this Agreement
or any of the Loan Documents has been obtained, (F) there is no litigation,
investigation or proceeding known to and affecting the Borrower or any Borrower
Affiliate for which the Borrower is required to give notice pursuant to
Section 6.03(c) (or, if there is any such litigation, investigation or
proceeding, then a notice containing the information required by Section 6.03(c)
shall be given concurrently with

40

--------------------------------------------------------------------------------

the delivery of the certificate given pursuant to this clause (v)), and (G) no
action, suit, investigation or proceeding is pending or threatened in any court
or before any arbitrator or governmental authority by or against the Borrower,
any Guarantor, the General Partner, or any of their respective properties, that
(x) contests or seeks to adversely affect the Shell Pipeline Acquisition, or
(y) could reasonably be expected to materially and adversely affect the Borrower
or any Guarantor, taken as a whole, or (z) seeks to affect or pertains to any
transaction contemplated hereby or the ability of the Borrower or any Guarantor
to perform its obligations under the Loan Documents;

        (v)   a certificate of a Responsible Officer (a) of the Borrower
demonstrating compliance with all financial covenants on a pro forma basis for
the quarter ended September 30, 2003, (b) of the Borrower as to the satisfaction
of all conditions specified in this Section 4.04 and Section 4.03, and
(c) providing copies of the following (A) pro forma financial statements of the
MLP on a consolidated basis after giving effect to the American Central
Acquisition and Shell Pipeline Acquisition for the period ended September 30,
2003, (B) a five-year financial forecast for the MLP pro forma after giving
effect to the American Central Acquisition and Shell Pipeline Acquisition, and
(C) such other financial information as the Agents may request;

        (vi)  opinions from (A) Hogan & Hartson, L.L.P., counsel to each Loan
Party and the General Partner, in form and substance satisfactory to the Agents
and their counsel, and (B) local counsel to the Company buying the assets in
connection with the Shell Pipeline Acquisition with respect to the deed of trust
or mortgage executed by such Company;

        (vii) a letter from CT Corporation System, Inc., to accept service of
process in the State of Texas on behalf of Company buying the assets in
connection with the Shell Pipeline Acquisition;

        (viii) receipt of evidence that (a) any required approvals have been
obtained from the lenders under the Parent Credit Agreement, and (b) a
certificate of MarkWest Parent stating that no Default or Event of Default
exists under the Parent Credit Agreement or will exist immediately after the
Shell Pipeline Funding Conditions Effective Date; and

        (ix)  such other assurances, certificates, documents, consents or
opinions as the Agents reasonably may require.

        (c)   Any fees due and payable at the Shell Pipeline Funding Conditions
Effective Date shall have been paid.

        (d)   The Borrower shall have paid Attorney Costs of the Administrative
Agent to the extent invoiced prior to, or on, the Shell Pipeline Funding
Conditions Effective Date.

        (e)   Documents, executed by each Company that has assets or conducts
business, in appropriate form for recording, where necessary, together with:

        (i)    such Lien searches as the Administrative Agent shall have
requested, and such termination statements or other documents as may be
necessary to confirm that the Collateral is subject to no other Liens (other
than Permitted Liens) in favor of any Persons;

        (ii)   funds sufficient to pay any filing or recording tax or fee in
connection with any and all UCC-1 financing statements or UCC-3 amendment
financing statements, or fees associated with the filing of the Mortgages or
amendments to Mortgages;

        (iii)  evidence that the Administrative Agent has been named as loss
payee under all policies of casualty insurance pertaining to the Collateral;

41

--------------------------------------------------------------------------------

        (iv)  such consents, estoppels, subordination agreements and other
documents and instruments executed by landlords and other Persons party to
material contracts relating to any Collateral as to which the Administrative
Agent shall be granted a Lien for the benefit of the Lenders, as requested by
the Administrative Agent or any Lender;

        (v)   certificates evidencing all of the issued and outstanding shares
of capital stock, partnership interests, or membership interests pledged
pursuant thereto, which certificates shall in each case be accompanied by
undated stock powers duly executed in blank, or, if any securities pledged
pursuant thereto are uncertificated securities, confirmation and evidence
satisfactory to the Administrative Agent that the security interest in such
uncertificated securities has been transferred to and perfected by the
Administrative Agent for the benefit of the Lenders in accordance with the
Uniform Commercial Code; and

        (vi)  evidence that all other actions necessary or, in the opinion of
the Administrative Agent or the Lenders, desirable to perfect and protect the
first priority Lien created by the Collateral Documents (except to the extent
otherwise permitted hereunder), and to enhance the Administrative Agent's
ability to preserve and protect its interests in and access to the Collateral,
have been taken;

        The Agents shall notify the Borrower of the Shell Pipeline Funding
Conditions Effective Date, and such notice shall be conclusive and binding.

        4.05    Conditions Precedent to Funding Loans for Acquisitions.    The
obligation of each Lender to fund its portion any Loan to finance an Acquisition
(other than the American Central Acquisition and Shell Pipeline Acquisition)
shall be subject to satisfaction of the conditions precedent set forth in
Section 4.03 and to additional condition precedent that the Borrower deliver to
the Lenders at least five Business Days before any requested Loan to fund an
Acquisition copies of historical financial statements pertaining to the Person
or business proposed to be acquired which historical financial statements if
unaudited must be satisfactory in form and substance to the Agents.

Remainder of this page intentionally left blank.

42

--------------------------------------------------------------------------------

ARTICLE V.
REPRESENTATIONS AND WARRANTIES

        Each of the Borrower and the MLP, and each Guarantor by its execution of
a Guaranty, represents and warrants to the Administrative Agent and the Lenders
that:

        5.01    Existence; Qualification and Power; Compliance with Laws.    As
of the Restatement Date, the Borrower is a direct wholly-owned subsidiary of the
MLP and MarkWest Parent owns at least 51% of the General Partner. The General
Partner and each Loan Party (a) is a corporation, partnership or limited
liability company duly organized or formed, validly existing and in good
standing under the Laws of the jurisdiction of its incorporation or
organization, (b) has all requisite power and authority and all governmental
licenses, authorizations, consents and approvals to own its assets, carry on its
business and to execute, deliver, and perform its obligations under the Loan
Documents to which it is a party, (c) is duly qualified and is licensed and in
good standing under the Laws of each jurisdiction where its ownership, lease or
operation of properties or the conduct of its business requires such
qualification or license, and (d) is in compliance with all Laws, except in each
case referred to in clause (e) or this clause (d), to the extent that failure to
do so could not reasonably be expected to have a Material Adverse Effect.

        5.02    Authorization; No Contravention.    The execution, delivery and
performance by each Loan Party of each Loan Document to which such Person is
party, have been duly authorized by all necessary corporate or other
organizational action, and do not and will not (a) contravene the terms of any
of such Person's Organization Documents; (b) conflict with or result in any
breach or contravention of, or the creation of any Lien under, any material
Contractual Obligation to which such Person is a party or any order, injunction,
writ or decree of any Governmental Authority to which such Person or its
property is subject; or (c) violate any Law.

        5.03    Governmental Authorization.    No approval, consent, exemption,
authorization, or other action by, or notice to, or filing with, any
Governmental Authority, except for the filings of mortgages and lien notices in
connection with the granting of security interests pursuant to the Collateral
Documents, is necessary or required in connection with the execution, delivery
or performance by, or enforcement against, any Loan Party of this Agreement or
any other Loan Document.

        5.04    Binding Effect.    This Agreement has been, and each other Loan
Document, when delivered hereunder, will have been duly executed and delivered
by each Loan Party that is party thereto. This Agreement constitutes, and each
other Loan Document when so delivered will constitute, a legal, valid and
binding obligation of such Loan Party, enforceable against each Loan Party that
is party thereto in accordance with its terms.

        5.05    Financial Statements; No Material Adverse Effect.    

        (a)   The audited financial statements delivered to the Lenders were
prepared in accordance with GAAP consistently applied throughout the period
covered thereby, except as otherwise expressly noted therein. Such financial
statements (i) fairly present the financial condition of the entities therein
named and their respective Subsidiaries as of the date thereof and their results
of operations for the period covered thereby in accordance in all material
respects with GAAP consistently applied throughout the period covered thereby,
except as otherwise expressly noted therein; and (ii) show all material
indebtedness and other liabilities, direct or contingent, of the entities
therein named and their Subsidiaries as of the date thereof, including
liabilities for taxes, material commitments and Indebtedness in accordance with
GAAP consistently applied throughout the period covered thereby.

        (b)   Since December 31, 2002, there has been no event or circumstance
that has or could reasonably be expected to have a Material Adverse Effect.

43

--------------------------------------------------------------------------------

        5.06    Litigation.    There are no actions, suits, proceedings, claims
or disputes pending or, to the knowledge of the MLP or the Borrower threatened
or contemplated in writing, at law, in equity, in arbitration or before any
Governmental Authority, by or against the Borrower or any Borrower Affiliate or
against any of their properties or revenues which (a) seek to affect or pertain
to this Agreement or any other Loan Document, the borrowing of Loans, the use of
the proceeds thereof, or the issuance of Letters of Credit hereunder, or (b) if
determined adversely, could reasonably be expected to have a Material Adverse
Effect.

        5.07    No Default.    Neither the Borrower nor any Borrower Affiliate
is in default under or with respect to any Contractual Obligation which could be
reasonably expected to have a Material Adverse Effect. No Default or Event of
Default has occurred and is continuing or would result from the consummation of
the transactions contemplated by this Agreement or any other Loan Document.
There is no default under any Material Agreement.

        5.08    Ownership of Property; Liens.    From and after the Restatement
Date, (a) each Loan Party and its Subsidiaries have good title to, or valid
leasehold interests in, all its real and personal property necessary or used in
the ordinary conduct of its business, except for such defects in title as would
not, individually or in the aggregate, have a Material Adverse Effect, and
(b) the property of the MLP, the Borrower and their respective Subsidiaries is
subject to no Liens, other than Permitted Liens.

        5.09    Environmental Compliance.    The MLP and the Borrower have
reasonably concluded that (a) there are no claims alleging potential liability
under or responsibility for violation of any Environmental Law except any such
claims that could not, individually or in the aggregate, reasonably be expected
to have a Material Adverse Effect, (b) there is no environmental condition or
circumstance, such as the presence or Release of any Hazardous Substance, on any
property owned, operated or used the Borrower or any Borrower Affiliate that
could reasonably be expected to have a Material Adverse Effect, and (c) there is
no violation of or by the Borrower or any Borrower Affiliate of any
Environmental Law, except for such violations as could not, individually or in
the aggregate, reasonably be expected to have a Material Adverse Effect.

        5.10    Insurance.    The properties of the Borrower and the Borrower
Affiliates are insured with financially sound and reputable insurance companies
not Affiliates of the Borrower, in such amounts, with such deductibles and
covering such risks as are customarily carried by companies engaged in similar
businesses and owning similar properties in localities where the Borrower or the
Borrower Affiliates operate.

        5.11    Taxes.    The Borrower and the Borrower Affiliates have filed
all federal, state and other material tax returns and reports required to be
filed, and have paid all federal, state and other material taxes, assessments,
fees and other governmental charges levied or imposed upon them or their
properties, income or assets otherwise due and payable, except those which are
being contested in good faith by appropriate proceedings and for which adequate
reserves have been provided in accordance with GAAP. There is no proposed tax
assessment against any Borrower Affiliate or any of their respective
Subsidiaries that would, if made, have a Material Adverse Effect.

        5.12    ERISA Compliance.    The representations and warranties set
forth in this Section 5.12 shall apply only if the Borrower or an ERISA
Affiliate establishes a Plan.

        (a)   Each Plan is in compliance in all material respects with the
applicable provisions of ERISA, the Code and other federal or state Laws except
to the extent that noncompliance could not reasonably be expected to have a
Material Adverse Effect. Each Plan that is intended to qualify under
Section 401(a) of the Code has received a favorable determination letter from
the IRS or an application for such a letter is currently being processed by the
IRS with respect thereto and, to the best knowledge of the MLP and the Borrower,
nothing has occurred which would prevent, or cause the loss of, such
qualification, except to the extent that nonqualification could

44

--------------------------------------------------------------------------------

not reasonably be expected to have a Material Adverse Effect. The Borrower and
each ERISA Affiliate have made all required contributions to each Plan subject
to Section 412 of the Code, and no application for a funding waiver or an
extension of any amortization period pursuant to Section 412 of the Code has
been made with respect to any Plan, except to the extent that nonpayment could
not reasonably be expected to have a Material Adverse Effect.

        (b)   There are no pending or, to the best knowledge of the MLP or the
Borrower, threatened claims, actions or lawsuits, or action by any Governmental
Authority, with respect to any Plan that could reasonably be expected to have a
Material Adverse Effect. Neither the MLP nor the Borrower nor any ERISA
Affiliate has engaged in or knowingly permitted to occur and, to the Borrower's
and the MLP's knowledge, no other party has engaged in or permitted to occur any
prohibited transaction or violation of the fiduciary responsibility rules with
respect to any Plan that has resulted or could reasonably be expected to result
in a Material Adverse Effect.

        (c)   (i) No ERISA Event has occurred or is reasonably expected to occur
that could reasonably be expected to have a Material Adverse Effect; (ii) no
Pension Plan has any Unfunded Pension Liability that (when aggregated with any
other Unfunded Pension Liability) has resulted or could reasonably be expected
to result in a Material Adverse Effect; and (iii) neither the Borrower nor any
ERISA Affiliate has engaged in a transaction that could be subject to Sections
4069 or 4212(c) of ERISA that could reasonably be expected to have a Material
Adverse Effect.

        5.13    Subsidiaries and other Investments.    As of the Restatement
Date the Borrower will have no Subsidiaries other than those specifically
disclosed in Schedule 5.13, and will have no equity investment in any other
corporation or other entity other than those specifically disclosed in
Schedule 5.13. From and after the Restatement Date the MLP has no Subsidiaries
other than the Borrower and the Borrower's Subsidiaries.

        5.14    Margin Regulations; Investment Company Act; Public Utility
Holding Company Act; Use of Proceeds.    

        (a)   Neither the Borrower nor any Borrower Affiliate is engaged nor
will it engage, principally or as one of its important activities, in the
business of purchasing or carrying margin stock (within the meaning of
Regulation U issued by the Board), or extending credit for the purpose of
purchasing or carrying margin stock. Margin Stock constitutes less than 25% of
those assets of each Loan Party which are subject to any limitation on a sale,
pledge, or other restrictions hereunder.

        (b)   Neither the Borrower nor any Borrower Affiliate, no Person
controlling the Borrower or any Borrower Affiliate, or any Subsidiary thereof
(i) is a "holding company," or a "subsidiary company" of a "holding company," or
an "affiliate" of a "holding company"or of a "subsidiary company" of a "holding
company," within the meaning of the Public Utility Holding Company Act of 1935,
or (ii) is or is required to be registered as an "investment company" under the
Investment Company Act of 1940.

        (c)   The Borrower will use all proceeds of Credit Extension in the
manner set forth in Section 6.12.

        5.15    Disclosure.    All material factual information hereto furnished
by or on behalf of the Borrower in writing to the Administrative Agent or any
Lender for purposes of or in connection with this Agreement or any transaction
contemplated hereby, as modified or supplemented by other information so
furnished, is true and accurate in all material respects, and such information
is not, or shall not be, as the case may be, incomplete by omitting to state any
material fact necessary to make such information not misleading. All estimates
and projections delivered to the Administrative Agent or any Lender were based
upon information that was available at the time such estimates or projections
were prepared and believed to be correct and upon assumptions believed to be
reasonable; however,

45

--------------------------------------------------------------------------------

the Borrower does not warrant that such estimates and projections will
ultimately prove to have been accurate.

        5.16    Labor Matters.    To the Borrower's and the MLP's knowledge,
there are no actual or threatened strikes, labor disputes, slowdowns, walkouts,
or other concerted interruptions of operations that could reasonably be expected
to have a Material Adverse Effect.

        5.17    Compliance with Laws.    Neither the Borrower nor any Borrower
Affiliate is in violation of any Laws, other than such violations which could
not, individually or collectively, reasonably be expected to have a Material
Adverse Effect. Neither the Borrower nor any Borrower Affiliate has received
notice alleging any noncompliance with any Laws, except for such noncompliance
which no longer exists, or which non-compliance could not reasonably be expected
to have a Material Adverse Effect.

        5.18    Third Party Approvals.    No approval, consent, exemption,
authorization, or other action by, or notice to, or filing with, any party that
is not a party to this Agreement is necessary or required in connection with the
execution, delivery or performance by, or enforcement against, any Loan Party of
this Agreement or any other Loan Document except where obtained or where the
failure to receive such approval, consent, exemption, authorization, or the
failure to do such other action by, or provide such notice could not reasonably
be expected to have a Material Adverse Effect and provided, however, that the
transfer of rights in certain Collateral consisting of rights under contracts to
a foreclosure purchaser may, in some instances, require the consent of third
parties who have rights in such Collateral

        5.19    Solvency.    Neither the Borrower and its Subsidiaries on a
consolidated basis nor the MLP and its Subsidiaries on a consolidated basis are
"insolvent" as such term is used and defined in (i) the United States Bankruptcy
Code or (ii) the Texas Uniform Fraudulent Transfer Act, Tex. Bus. & Com. Code
Ann. §24.003.

        5.20    Collateral.    (a) The provisions of each of the Collateral
Documents are effective to create in favor of the Administrative Agent for the
benefit of the Lenders, a legal valid and enforceable first priority security
interest in all right, title and interest of each Company in the Collateral
described therein, except as otherwise permitted hereunder; and financing
statements have been filed in the offices in all of the jurisdictions listed in
the schedule to all Security Agreements and Mortgages.

        (b)   All representations and warranties of each Loan Party thereto
contained in the Collateral Documents are true and correct in all material
respects.

        (c)   None of the terms or provisions of any indenture, mortgage, deed
of trust, agreement or other instrument to which the Borrower or any Borrower
Affiliate is a party or by which the Borrower or any Borrower Affiliate or the
property of the Borrower or any Borrower Affiliate is bound prohibit the filing
or recordation of any of the Loan Documents or any other action which is
necessary or appropriate in connection with the perfection of the Liens on
material assets evidenced and created by any of the Loan Documents.

46

--------------------------------------------------------------------------------

ARTICLE VI.
AFFIRMATIVE COVENANTS

        So long as any Lender shall have any Commitment hereunder, or any Loan
or other Obligation shall remain unpaid or unsatisfied, or any Letter of Credit
shall remain outstanding, each of the Borrower and the MLP shall, and shall
cause each of their Subsidiaries to:

        6.01    Financial Statements.    Deliver to the Administrative Agent and
each Lender, in form and detail reasonably satisfactory to the Administrative
Agent and the Required Lenders:

        (a)   intentionally omitted;

        (b)   as soon as available, but in any event within 90 days after the
end of each fiscal year of the MLP, consolidated balance sheets of the MLP and
its Subsidiaries as at the end of such fiscal year, and the related statements
of income and cash flows for such fiscal year, setting forth in each case in
comparative form the figures for the previous fiscal year of the MLP, if any,
all in reasonable detail, audited and accompanied by a report and opinion of
PriceWaterhouseCoopers LLP or other independent certified public accountant of
nationally recognized standing reasonably acceptable to the Required Lenders,
which report and opinion shall be prepared in accordance with GAAP and shall not
be subject to any qualifications or exceptions as to the scope of the audit nor
to any qualifications and exceptions not reasonably acceptable to the Required
Lenders;

        (c)   as soon as available, but in any event within 90 days after the
end of each fiscal year of the MLP (which shall be the same as the fiscal year
of the Borrower), an unaudited consolidated balance sheet of the Borrower and
its Subsidiaries as at the end of such fiscal year setting forth in each case in
comparative form the figures for the previous fiscal year for the Borrower, if
any, all in reasonable detail, and the related statements of income and cash
flows for such fiscal year, setting forth in each case in comparative form the
figures for the corresponding fiscal year certified by a Responsible Officer of
the Borrower as fairly presenting the financial condition, results of operations
and cash flows of the Borrower and its Subsidiaries in accordance with GAAP;

        (d)   as soon as available, but in any event within 45 days after the
end of each of the first three fiscal quarters of each fiscal year of the MLP,
an unaudited consolidated balance sheet of the MLP and its Subsidiaries and the
Borrower and its Subsidiaries as at the end of such fiscal quarter, and the
related statements of income and cash flows for such fiscal quarter and for the
portion of the MLP's fiscal year then ended, setting forth in each case in
comparative form the figures for the corresponding fiscal quarter of the
previous fiscal year of the MLP or the Borrower, if any, and the corresponding
portion of the previous fiscal year of the MLP or the Borrower, if any, all in
reasonable detail and certified by a Responsible Officer of the MLP or the
Borrower, as applicable, as fairly presenting the financial condition, results
of operations and cash flows of the MLP or the Borrower, as applicable, and
their respective Subsidiaries in accordance with GAAP, subject only to normal
year-end audit adjustments and the absence of footnotes;

        (e)   within 45 days after the end of each Fiscal Year, Borrower shall
deliver a one year projection/budget for the MLP for the year following such
Fiscal Year; and

        (f)    within 90 days after the Restatement Date, the audited financial
statements of the American Central Acquisition and Shell Pipeline Acquisition,
if required by the Securities and Exchange Commission in conjunction with the
MLP's Form S-1 filing.

        6.02    Certificates; Other Information.    Deliver to the
Administrative Agent and each Lender, in form and detail satisfactory to the
Administrative Agent and the Required Lenders:

        (a)   concurrently with the delivery of the financial statements
referred to in Sections 6.01(b), (c) and (d), a duly completed Compliance
Certificate in form of Exhibit C signed by a Responsible Officer of the Borrower
and a Responsible Officer of the MLP;

47

--------------------------------------------------------------------------------

        (b)   promptly after the same are available, copies of each annual
report, proxy or financial statement or other report or written communication
sent to the equity owners of the MLP, and copies of all annual, regular,
periodic and special reports and registration statements which the MLP may file
or be required to file with the Securities and Exchange Commission under
Section 13 or 15(d) of the Securities Exchange Act of 1934, and not otherwise
required to be delivered to the Administrative Agent pursuant hereto;

        (c)   promptly after execution thereof, copies of Material Agreements
and any material amendment thereto; and

        (d)   promptly, such additional information regarding the business,
financial or corporate affairs of any Loan Party as the Administrative Agent, at
the request of any Lender, may from time to time reasonably request, which
information may include copies of any detailed audit reports, if any, management
letters or recommendations submitted to the board of directors (or the audit
committee of the board of directors) of the Borrower by independent accountants
in connection with the accounts or books of the Borrower or any Subsidiary, or
any audit of any of them.

        6.03    Notices.    Promptly notify the Administrative Agent and each
Lender:

        (a)   of the occurrence of any Default or Event of Default, as soon as
possible but in any event within ten (10) days after the occurrence thereof;

        (b)   of any matter that has resulted or could reasonably be expected to
result in a Material Adverse Effect, including any of the following events if
such has resulted or could reasonably be expected to result in a Material
Adverse Effect: (i) breach or non-performance of, or any default under, a
Contractual Obligation of any Loan Party; (ii) any litigation, investigation by
or required by a Governmental Authority, proceeding or suspension of licenses or
permits between any Loan Party and any Governmental Authority; (iii) any
dispute, litigation, investigation or proceeding involving any Loan Party
related to any Environmental Law;

        (c)   of any litigation, investigation or proceeding known to and
affecting the Borrower or any Borrower Affiliate in which (i) the amount
involved exceeds (individually or collectively) $3,500,000, or (ii) injunctive
relief or other relief is sought, which could be reasonably expected to have a
Material Adverse Effect; and

        (d)   of any material change in accounting policies or financial
reporting practices by the Borrower or the MLP.

        Each notice pursuant to this Section shall be accompanied by a statement
of a Responsible Officer of the Borrower setting forth details of the occurrence
referred to therein and stating what action the Borrower has taken and proposes
to take with respect thereto. Each notice pursuant to Section 6.03(a) shall
describe with particularity any and all provisions of this Agreement or other
Loan Document that have been breached.

        6.04    Payment of Obligations.    Pay and discharge as the same shall
become due and payable, all its obligations and liabilities, including (a) the
Obligations, (b) all tax liabilities, assessments and governmental charges or
levies upon it or its properties or assets and (c) all lawful claims which, if
unpaid, would by law become a Lien upon its property, except, in the case of
clause (b) or (c), where (x) the validity thereof are being contested in good
faith by appropriate proceedings and (y) adequate reserves in accordance with
GAAP are being maintained by the appropriate Loan Party.

        6.05    Preservation of Existence, Etc.    (a) Preserve, renew and
maintain in full force and effect its legal existence and good standing under
the Laws of the jurisdiction of its organization, except in a transaction
permitted by Sections 7.06 and 7.07, (b) take all reasonable action to maintain
all rights,

48

--------------------------------------------------------------------------------

privileges, permits, licenses and franchises material to the conduct of its
business, except in a transaction permitted by Sections 7.06 and 7.07.

        6.06    Maintenance of Assets and Business.    (a) Maintain all material
properties, equipment, licenses, permits, and franchises necessary for its
normal business; (b) keep all of its assets which are useful in and necessary to
its business in good working order and condition (ordinary wear and tear
excepted) and make all necessary repairs thereto and replacements thereof,
(c) do all things necessary to obtain, renew, extend, and continue in effect all
Authorizations which may at any time and from time to time be necessary for the
operation of its business in compliance with applicable Law, except where the
failure to so maintain, renew, extend, or continue in effect could not
reasonably be expected to have a Material Adverse Effect; (d) preserve or renew
all of its registered patents, trademarks, trade names and service marks, the
non-preservation of which could reasonably be expected to have a Material
Adverse Effect; and (e) use the standard of care typical in the industry in the
operation and maintenance of its facilities.

        6.07    Maintenance of Insurance.    (a) Maintain with responsible
insurance companies insurance with respect to its properties and business
(including business interruption insurance) against such casualties and
contingencies and of such types and in such amounts as is customary in the case
of similar businesses and which is satisfactory to the Administrative Agent and
the Required Lenders and will (i) furnish to the Administrative Agent on each
anniversary of the Restatement Date a certificate or certificates of insurance
from the applicable insurance company evidencing the existence of insurance
required to be maintained by this Agreement and the other Loan Documents and
evidencing that Administrative Agent is listed as sole loss payee on property
insurance (except as to properties owned by MarkWest Parent or the MarkWest Inc.
Operating Subsidiaries (as defined in the Parent Credit Agreement)) and the
Administrative Agent and Lenders are additional insureds on liability insurance,
and (ii) upon request of the Administrative Agent, furnish to each Lender at
reasonable intervals a certificate of an Authorized Officer of the Borrower
setting forth the nature and extent of all insurance maintained in accordance
with this Section.

        (b)   (i) Except as the Administrative Agent may otherwise consent to in
writing, Borrower will, and will cause each of its Subsidiaries to, forthwith
upon receipt, transmit and deliver to the Administrative Agent, in the form
received, all cash, checks, drafts, chattel paper and other instruments or
writings for the payment of money (properly endorsed, where required, so that
such items may be collected by the Administrative Agent) which may be received
by the Borrower at any time in full or partial payment of amounts due under any
insurance policy. Except as the Administrative Agent may otherwise consent in
writing, any such items which may be received by the Borrower will not be
commingled with any other of its funds or property, but will be held separate
and apart from its own funds or property and upon express trust for the
Administrative Agent until delivery is made to the Administrative Agent.
Borrower will comply with the terms and conditions of any consent given by the
Administrative Agent pursuant to the provisions of this paragraph.

        All items or amounts in excess of $250,000 which are delivered by the
Borrower or by any insurance company to the Administrative Agent on account of
partial or full payment of amounts due under any insurance policy shall be
deposited to the credit of a deposit account (herein called the "Insurance
Deposit Account") of the Borrower with the Administrative Agent, as security for
payment of the Obligations. Borrower shall have no right to withdraw any funds
deposited in the Insurance Deposit Account. Administrative Agent will apply all
or any of the then balance in the Insurance Deposit Account toward payment of
the Obligations, in such order of application as the Administrative Agent may
determine. Administrative Agent may, from time to time, in its reasonable
discretion and with the consent of the Required Lenders, release all or any of
such balance representing collected funds to the Borrower. Administrative Agent
is authorized to

49

--------------------------------------------------------------------------------

endorse, in the name of the Borrower, any item, howsoever received by the
Administrative Agent, representing any payment under any insurance policy.

        (ii)   The Borrower hereby grants to the Administrative Agent, for the
benefit of the Lenders, a lien on and security interest in and to such account
and all monies, cash, checks, drafts, certificates of deposit, instruments,
investment property, and other items ever received by Administrative Agent for
deposit therein and held therein, as security for the Obligations. The rights
granted by this Section 6.07 shall be in addition to the rights of the
Administrative Agent under any statutory banker's Lien or the common law right
of setoff.

        6.08    Compliance with Laws and Contractual Obligations.    (a) Comply
in all material respects with the requirements of all Laws (including
Environmental Laws) applicable to it or to its business or property, except in
such instances in which (i) such requirement of Law is being contested in good
faith or a bona fide dispute exists with respect thereto; or (ii) the failure to
comply therewith could not be reasonably expected to have a Material Adverse
Effect; and (b) comply with all Contractual Obligations, except the failure to
comply therewith could not be reasonably expected to have a Material Adverse
Effect.

        6.09    Books and Records.    Maintain proper books of record and
account, in which full, true and correct entries in conformity with GAAP
consistently applied shall be made of all financial transactions and matters
involving its assets and business; and (b) maintain such books of record and
account in material conformity with all applicable requirements of any
Governmental Authority having regulatory jurisdiction over it.

        6.10    Inspection Rights.    Permit representatives and independent
contractors of the Administrative Agent and each Lender to visit and inspect any
of its properties, to examine its corporate, financial and operating records,
and make copies thereof or abstracts therefrom, and to discuss its affairs,
finances and accounts with its directors, officers, and independent public
accountants, at such reasonable times during normal business hours and as often
as may be reasonably desired, upon reasonable advance notice to the Borrower;
provided, however, that when an Event of Default exists the Administrative Agent
or any Lender (or any of their respective representatives or independent
contractors) may do any of the foregoing at the expense of the Borrower at any
time during normal business hours and without advance notice. Additionally,
Administrative Agent may, at the request of the Required Lenders, conduct or
cause to be conducted a commercial field examination of the Borrower's and its
Subsidiaries' financial and accounting records and Borrower shall pay the cost
of such commercial field examination if such field examination occurs after the
occurrence and during the continuation of an Event of Default.

        6.11    Compliance with ERISA.    With respect to each Plan maintained
by a Company, do each of the following: (a) maintain each Plan in compliance in
all material respects with the applicable provisions of ERISA, the Code and
other federal or state Laws, (b) cause each Plan which is qualified under
Section 401(a) of the Code to maintain such qualification, and (c) make all
required contributions to any Plan subject to Section 412 of the Code, except to
the extent that noncompliance, with respect to each event listed above, could
not be reasonably expected to have a Material Adverse Effect

        6.12    Use of Proceeds.    (a) Use the proceeds (including Letters of
Credit) of the Loans to (i) refinance the Indebtedness outstanding under the
Original Credit Agreement, (ii) finance non-hostile Acquisitions (including the
American Central Acquisition and Shell Pipeline Acquisition) and Capital
Expenditures by the Borrower and its Subsidiaries of Persons or assets subject
to compliance with this Agreement, including Sections 7.02 and 7.10, and
(iii) fund working capital requirements and other general corporate purposes of
the Borrower and its Subsidiaries, (iv) fund Quarterly Distributions to the
extent permitted by Sections 7.08(b) and (c) in an amount not to exceed during
any twelve consecutive month period the product obtained by multiplying the
total number of

50

--------------------------------------------------------------------------------

MLP common and subordinated units outstanding by $0.50, and (v) pay fees, costs
and expenses owed pursuant to this Agreement.

        6.13    Material Agreements.    Enforce the obligations of MarkWest
contained in the indemnification provisions of the Omnibus Agreement, and
enforce all other obligations of the MarkWest Parties contained in the Material
Agreements to the same extent as they would enforce similar obligations of
unrelated third parties.

        6.14    Intentionally Omitted.    

        6.15    Guaranties.    As an inducement to the Administrative Agent and
Lenders to enter into this Agreement, the MLP and each Subsidiary that executed
a Guaranty pursuant to the Original Credit Agreement shall execute a
ratification and confirmation of their Guaranties in connection with this
Agreement, in the form annexed to this Agreement. In addition, at the time of
the formation or acquisition of any Subsidiary of the Borrower or MLP, cause
such Subsidiary to execute and deliver to the Administrative Agent (a) a
Guaranty substantially in the form and upon the terms of Exhibit E, providing
for the guaranty of payment and performance of the Obligations, (b) Collateral
Documents in form and substance satisfactory to the Administrative Agent
creating liens and security interests in all assets and properties of such
Subsidiary and in the equity interests in such Subsidiary, and (c) certified
copies of such Subsidiary's Organization Documents and opinions of counsel with
respect to such Subsidiary and such Guaranty, and (d) such other documents and
instruments as may be required with respect to such Subsidiary pursuant to
Section 6.16.

        6.16    Further Assurances; Additional Collateral.    (a) The Borrower
and the MLP shall cause the MLP and each Subsidiary of the Borrower or the MLP
to take such actions and to execute and deliver such documents and instruments
as the Administrative Agent shall require to ensure that the Administrative
Agent on behalf of the Lenders shall, at all times, have received currently
effective duly executed Loan Documents granting Liens and security interests in
substantially all of the assets of the MLP and each Subsidiary of the Borrower
and the MLP, including all capital stock, partnership, joint venture, membership
interests, or other equity interests; provided, however that (i) MarkWest Energy
Appalachia, L.L.C. shall not be required to grant a Lien on its interests in the
Equitable Leases; and (ii) unless otherwise requested by the Administrative
Agent acting upon the direction of the Required Lenders, neither MW Pinnacle, MW
PNG, MW Texas PNG nor MW Blackhawk shall be required to grant a Lien on any of
their assets, other than assets constituting part of or related to the lateral
pipeline transmission systems located in Texas, and the Appleby and Brahaney gas
gathering, compressor and processing pipeline systems, as applicable.

        (b)   In connection with the actions required pursuant to the foregoing
subsection (a), the Borrower and the MLP shall cause the MLP and each Subsidiary
of the Borrower and the MLP to execute and deliver such stock certificates,
blank stock powers, evidence of corporate authorization, opinions of counsel,
current valuations, evidence of title, title opinions, title insurance and other
documents, and shall use commercially reasonable efforts to obtain landlord and
mortgagee waivers and third party consents, as shall be requested by the
Administrative Agent, in each case in form and substance satisfactory to the
Administrative Agent.

        (c)   The Liens required by this Section 6.16 shall be first priority
perfected Liens in favor of the Administrative Agent for the benefit of the
Lenders, subject to no other Liens except Permitted Liens of the type described
in Section 7.01 (other than Section 7.01(h) ). If the Administrative Agent shall
determine that, as of any date, the Borrower or the MLP shall have failed to
comply with this Section 6.16, the Administrative Agent may (and at the
direction of the Required Lenders, shall) notify the Borrower in writing of such
failure and, within 30 days from and after receipt of such written notice by the
Borrower, the Borrower shall execute and deliver to the Administrative Agent
supplemental or additional Loan Documents, in form and substance satisfactory to
the Administrative Agent and its counsel, securing payment of the Notes and the

51

--------------------------------------------------------------------------------

other Obligations and covering additional assets and properties not then
encumbered by any Loan Documents (together with such other information, as may
be requested by the Administrative Agent, each of which shall be in form and
substance reasonably satisfactory to the Administrative Agent) such that the
Administrative Agent shall have received currently effective duly executed and
perfected Collateral Documents encumbering substantially all of the assets of
the MLP, Borrower and their respective Subsidiaries as required by
Section 6.16(a).

Remainder of this page intentionally left blank.

52

--------------------------------------------------------------------------------

ARTICLE VII.
NEGATIVE COVENANTS

        So long as any Lender shall have any Commitment hereunder, or any Loan
or other Obligations shall remain unpaid or unsatisfied, or any Letter of Credit
shall remain outstanding, each of the MLP and the Borrower agree that they shall
not, nor shall they permit any of their respective Subsidiaries to, directly or
indirectly:

        7.01    Liens.    Create, incur, assume or suffer to exist, any Lien
upon any of its property, assets or revenues, whether now owned or hereafter
acquired, other than the following:

        (a)   Liens pursuant to any Loan Document;

        (b)   Liens existing on the Conditions Effective Date and listed on
Schedule 7.01 to the Original Credit Agreement and any renewals or extensions
thereof, provided that the property covered thereby is not increased, the amount
of the Indebtedness secured thereby is not increased, and any renewal or
extension of the obligations secured or benefitted thereby is permitted under
this Agreement;

        (c)   Liens for taxes not yet due or which are being contested in good
faith and by appropriate proceedings, if adequate reserves with respect thereto
are maintained on the books of the applicable Person in accordance with GAAP;

        (d)   carriers', warehousemen's, mechanics', materialmen's, repairmen's
or other like Liens arising in the ordinary course of business which are not
overdue for a period of more than 30 days or which are being contested in good
faith and by appropriate proceedings, if adequate reserves with respect thereto
are maintained on the books of the applicable Person;

        (e)   pledges or deposits in the ordinary course of business in
connection with workers' compensation, unemployment insurance and other social
security legislation, other than any Lien imposed by ERISA;

        (f)    deposits to secure the performance of bids, trade contracts
(other than for borrowed money), leases, statutory obligations, surety and
appeal bonds, performance bonds and other obligations of a like nature, in each
case incurred in the ordinary course of business;

        (g)   easements, rights-of-way, restrictions and other encumbrances
affecting real property which do not, taken as a whole, materially detract from
the value of the Mortgaged Properties subject thereto or materially interfere
with the ordinary conduct of the business of the applicable Person;

        (h)   judgment Liens not giving rise to an Event of Default;

        (i)    any Lien existing on any asset (other than stock of a Subsidiary)
prior to acquisition thereof by the Borrower or a Subsidiary, and not created in
contemplation of such acquisition, provided that (i) no such Lien shall be
extended to cover property other than the asset being acquired, (ii) such Lien
was not created in contemplation of or in connection with such acquisition, and
(iii) the Indebtedness thereby secured is permitted by Section 7.04(d);

        (j)    Liens securing Capitalized Lease obligations provided that the
Indebtedness in respect of such Capitalized Lease is permitted under
Section 7.04(d);

        (k)   Purchase money Liens upon or in any property acquired by Borrower
or any of is Subsidiaries to secure the deferred portion of the purchase price
of such property or to secure Indebtedness incurred to finance the acquisition
of such property, provided that (i) no such Lien shall be extended to cover
property other than the property being acquired, and (ii) the Indebtedness
thereby secured is permitted by Section 7.04(d);

53

--------------------------------------------------------------------------------

        (l)    Liens reserved in or exercisable under any lease or sublease to
which the Borrower or a Subsidiary is a lessee which secure the payment of rent
or compliance with the terms of such lease or sublease; provided, that the rent
under such lease or sublease is not then overdue and the Borrower or Subsidiary
is in material compliance with the terms and conditions thereof;

        (m)  any interest or title of a lessor under any lease entered into by
the Borrower or any Subsidiary in the ordinary course of its business and
covering only the assets so leased; and

        (n)   Liens incurred in the ordinary course of business in connection
with margin requirements under Lender Hedging Agreements not to exceed in the
aggregate $3,000,000 at any time outstanding.

        7.02    Investments.    Make or own any Investments, except:

        (a)   Investments existing on the Restatement Date and listed in
Section (b) of Schedule 5.13;

        (b)   Cash Equivalents;

        (c)   Investments constituting Indebtedness permitted under
Section 7.04(h);

        (d)   Investments by the MLP in the Borrower;

        (e)   Acquisitions of not more than 5% of the outstanding equity
securities of any Person;

        (f)    Investments by the Borrower and its Subsidiaries in any
Subsidiary of the Borrower that, prior to such Investment, is a Guarantor;

        (g)   Acquisition of assets by the Borrower prior to the Restatement
Date;

        (h)   trade accounts receivable which are for goods furnished or
services rendered in the ordinary course of business; and

        (i)    Permitted Acquisitions by the Borrower or its Subsidiaries.

        7.03    Hedging Agreements.    Enter into any Swap Contracts other than
in the ordinary course of business for the purpose of protecting against
fluctuations in interest rates, commodity prices, or foreign exchange rates and
not for purposes of speculation, provided that the Swap Contract shall not
contain any provision exonerating the non-defaulting party from its obligation
to make payments on outstanding transactions to the defaulting party.

        7.04    Indebtedness.    

        Create, incur, or assume any Indebtedness except:

        (a)   Indebtedness incurred pursuant to the Loan Documents;

        (b)   Indebtedness owed by a Subsidiary to the Borrower or to a
Wholly-Owned Subsidiary or by the Borrower to a Wholly-Owned Subsidiary of the
Borrower, provided, that, in each such case such Indebtedness is evidenced by a
promissory note which has been pledged to secure the Obligations and is in the
possession of the Administrative Agent;

        (c)   Other Indebtedness of the Borrower and the MLP ("Subordinated
Indebtedness") subordinated to the Obligations pursuant to a subordination
agreement in form and substance satisfactory to the Agents in their sole
discretion (a "Subordination Agreement"), provided that such Subordinated
Indebtedness shall bear a market rate of interest and shall not require any
payment of principal earlier than six (6) months after the Stated Maturity Date;

        (d)   Obligations (contingent or otherwise) of the Borrower, the MLP or
any Subsidiary (other than MW Texas PNG, MW New Mexico, MW PNG, and MW
Blackhawk) existing or arising under any Swap Contract to the extent permitted
by Section 7.03;

54

--------------------------------------------------------------------------------

        (e)   Indebtedness of the MLP, the Borrower and their respective
Subsidiaries (other than MW Texas PNG, MW New Mexico, MW PNG, and MW Blackhawk)
in respect of purchase money obligations for fixed or capital assets within the
limitations set forth in Section 7.01(k); provided, however, that the aggregate
amount of such Indebtedness at any one time outstanding shall not exceed
$7,500,000;

        (f)    Other Indebtedness of the MLP, the Borrower and their respective
Subsidiaries (other than MW Texas PNG, MW New Mexico, MW PNG and MW Blackhawk)
not to exceed $7,500,000 in the aggregate principal amount outstanding at any
time.

Provided, that if any Indebtedness is incurred pursuant to this Section 7.04,
both before and after such Indebtedness is created, incurred or assumed, no
Default or Event of Default shall exist.

        7.05    Lease Obligations.    Create or suffer to exist any obligations
for the payment of rent for any property under lease or agreement to lease,
except for operating leases (other than those constituting Synthetic Lease
Obligations) entered into or assumed by the Borrower or any Subsidiary after the
Conditions Effective Date in the ordinary course of business or entered into or
assumed in connection with any Permitted Acquisition, provided that, such
operating leases will not require the payment of an aggregate amount of payments
in excess of (excluding escalations resulting from a rise in the consumer price
or similar index) $7,500,000 during the full remaining term of such Leases,
exclusive of expenses for maintenance, repairs, insurance taxes, assessments and
similar changes.

        7.06    Fundamental Changes.    Merge or consolidate with or into, or
convey, transfer, lease or otherwise Dispose of (whether in one transaction or
in a series of transactions) all or substantially all of its assets (whether now
owned or hereafter acquired) to or in favor of any Person, except that, so long
as no Default or Event of Default exists or would result therefrom:

        (a)   any Person may merge into the Borrower provided that the Borrower
is the surviving entity;

        (b)   any Subsidiary may merge with (i) the Borrower, provided that the
Borrower shall be the continuing or surviving Person, or (ii) any one or more
Subsidiaries, provided that when any Wholly-Owned Subsidiary is merging with
another Subsidiary, a Wholly-Owned Subsidiary shall be the continuing or
surviving Person;

        (c)   any Subsidiary may sell all or substantially all of its assets
(upon voluntary liquidation or otherwise), to the Borrower or to another
Subsidiary; provided that if the seller in such a transaction is a Wholly-Owned
Subsidiary, then the purchaser must also be a Wholly-Owned Subsidiary; and

        (d)   any Person (other than the Borrower or a Subsidiary of the
Borrower) may merge into any Subsidiary, provided that such Subsidiary is the
surviving entity.

        7.07    Dispositions.    

        Make any Disposition or enter into any agreement to make any
Disposition, except:

        (a)   Dispositions by the Borrower or its Subsidiaries of inventory in
the ordinary course of business;

        (b)   Dispositions of property by any Subsidiary to the Borrower, or by
any Subsidiary or by the Borrower, to a Wholly-Owned Subsidiary that is a
Guarantor; or

        (c)   other Dispositions for fair market value, provided no Default or
Event of Default then exists or arises as a result thereof, provided that if the
Disposition is for cash and a prepayment is required by Section 2.04(b)(i), the
Borrower shall make such prepayment in accordance with such Section.

55

--------------------------------------------------------------------------------

        7.08    Restricted Payments; Distributions and Redemptions.    Declare
or make, directly or indirectly, any Restricted Payment, or incur any obligation
(contingent or otherwise) to do so, except that:

        (a)   each Subsidiary may make Restricted Payments to the Borrower and
to Wholly-Owned Subsidiaries of the Borrower;

        (b)   the Borrower (i) may declare and make Quarterly Distributions of
Available Cash (as defined in the Limited Liability Company Agreement
(Borrower)), (ii) may purchase MLP units under the MLP's Long-Term Incentive
Plan in accordance with, and as defined in, the Limited Liability Company
Agreement (Borrower) and the Partnership Agreement (MLP), and (iii) and any
Guarantor may make redemptions of, or purchase equity interest in, the Borrower
or any Guarantor from employees of the Borrower or such Guarantor; provided,
that at the time each Quarterly Distribution is made or any purchase or
redemption is made no Default or Event of Default exists or would result
therefrom; provided further that the aggregate amount expended in any
consecutive 12-month period for purchases or redemptions pursuant to
clause (iii) above shall not exceed $500,000; and

        (c)   the MLP may (i) declare and make Quarterly Distributions of
Available Cash (as defined in the Partnership Agreement (MLP)) to the extent
such Quarterly Distributions in any fiscal quarter do not exceed, in the
aggregate, Available Cash as defined in the Partnership Agreement (MLP) for the
immediately preceding fiscal quarter and are made in accordance with the
Partnership Agreement (MLP) and (ii) purchase MLP units under the MLP's
Long-Term Incentive Plan in accordance with, and as defined in, the Partnership
Agreement (MLP); provided, that at the time each such Quarterly Distribution or
purchase is made no Default or Event of Default exists or would result
therefrom.

        7.09    ERISA.    At any time engage in a transaction which could be
subject to Section 4069 or 4212(c) of ERISA, or permit any Plan maintained by a
Company to (a) engage in any non-exempt "prohibited transaction" (as defined in
Section 4975 of the Code); (b) fail to comply with ERISA or any other applicable
Laws; or (c) incur any material "accumulated funding deficiency" (as defined in
Section 302 of ERISA), which, with respect to each event listed above, could be
reasonably expected to have a Material Adverse Effect.

        7.10    Nature of Business; Capital Expenditures; Risk
Management.    Engage in any line of business other than the Midstream Business,
or make any Capital Expenditures or Acquisitions permitted by Section 7.02
except in connection with the Midstream Business. In addition to the foregoing,
(a) the MLP may not engage in any business other than the ownership of the
Borrower and the operation of the MLP, (b) MW Texas PNG may not engage in any
business other than the ownership and operation of the Rio Nogales Pipelines,
(c) in the event MW New Mexico acquires the Hobbs Pipeline, MW New Mexico may
not engage in any business other than the ownership and operation of the Hobbs
Pipeline, (d) MW Blackhawk may not engage in any business other than the
ownership and operation of the Blackhawk Pipeline, and (e) MW PNG may not engage
in any business other than the ownership and operation of the Lake Whitney
Pipeline. Without the written approval of the Agents, materially change its risk
management policy.

        7.11    Transactions with Affiliates.    Sell, lease or otherwise
transfer any property or assets to, or purchase, lease or otherwise acquire any
property or assets from, or otherwise engage in any other transactions with, any
of its Affiliates, except (i) transactions between or among the Borrower and its
Wholly-Owned Subsidiaries not involving any other Affiliate, and (ii) any
Restricted Payment permitted by Section 7.08, and (iii) in the ordinary course
of business at prices and on terms and conditions not less favorable to the MLP,
the Borrower or such Subsidiary, as applicable, than could be obtained on an
arm's length basis from unrelated third parties.

56

--------------------------------------------------------------------------------

        7.12    Burdensome Agreements.    Enter into any Contractual Obligation
that limits the ability of any Subsidiary to make Restricted Payments to the
Borrower or to otherwise transfer property to the Borrower. Notwithstanding the
foregoing, (i) documents governing a Capitalized Lease or a purchase money Lien
permitted by Sections 7.01(j) and (k) may prohibit other Liens on the asset
encumbered by such Lien, and (ii) the Lenders acknowledge that the real estate
leases described on Schedule 7.12 restrict or prohibit Liens on the Borrower's
or its Subsidiary's leasehold interest.

        7.13    Use of Proceeds.    Use the proceeds of any Loan for purposes
other than those permitted by Section 6.12, or use the proceeds of any Loan,
whether directly or indirectly, and whether immediately, incidentally or
ultimately, to purchase or carry margin stock (within the meaning of
Regulation U of the Board) or to extend credit to others for the purpose of
purchasing or carrying margin stock or to refund indebtedness originally
incurred for such purpose.

        7.14    Material Agreements.    (a) Permit any amendment to any Borrower
Operating Agreement or any Material Agreement, if such amendment could
reasonably be expected to (y) have a material adverse effect on the ability of
the Borrower or any Guarantor to perform its obligations under the Loan
Documents to which it is a party or (z) otherwise materially adversely affect
the Lenders; or (b) permit any assignment of any Material Agreement if such
assignment could reasonably be expected to materially adversely affect the
Lenders or have a Material Adverse Effect on the ability of the Borrower or any
other Loan Party to perform its obligations under the Loan Documents to which it
is a party.

        7.15    Financial Covenants.    

        (a)   Interest Coverage Ratio.    Permit the Interest Coverage Ratio as
of the end of any fiscal quarter to be less than the ratio of 3.5 to 1.0.

        (b)   Leverage Ratio.    Permit the Leverage Ratio at any time prior to
March 31, 2004 to be greater than the ratio of 4.75 to 1.0 or on or after
March 31, 2004 to be greater than the ratio of 3.5 to 1.0.

        (c)   Minimum Net Worth.    Permit the net worth of the Borrower to be
less than the sum of (i) $55,000,000 and (ii) 75% of the proceeds of all equity
issued subsequent to the Closing Date.

        (d)   Fixed Fee Interest Coverage Ratio.    Permit the Fixed Fee
Interest Coverage Ratio as of the end of any fiscal quarter to be less than the
ratio of 3.0 to 1.0. The Fixed Fee Interest Coverage Ratio shall only apply if
freely available cash reserves at the MarkWest Parent (including the balance, if
any, of the $2,500,000 cash deposit pledged pursuant to the MarkWest Parent
Pledge Agreement) are less than $17,500,000 measured as of the end of each
fiscal quarter (or if the Equitable Agreement has been entered into and is
reasonably satisfactory to the Agents, then such freely available cash reserves
shall be not less than $12,500,000) and if the Natural Resources/Triana Energy
Company Agreement has been restructured satisfactorily to the Agents and the
Equitable Agreement has been entered into satisfactorily to the Agents, then
this covenant shall thereafter cease to be in effect.

        (e)   Adjustments for Acquisitions.    For purposes of determining
compliance with Sections 7.15(a), (b) and (d):

        (i)    Consolidated EBITDA shall be calculated after giving effect, on a
pro forma basis for the four consecutive fiscal quarters most recently
completed, to any Permitted Acquisition occurring during such period, as if such
Permitted Acquisition occurred on the first day of such period.

        (ii)   If, in connection with an Acquisition, any Indebtedness is
incurred or assumed by a Company, then Consolidated Interest Charges shall be
calculated, on a pro forma basis (in a

57

--------------------------------------------------------------------------------

manner acceptable to the Required Lenders) for the four quarters most recently
completed, as if such Indebtedness had been incurred on the first day of such
period.

        7.16    Subordinated Indebtedness.    Neither the Borrower nor the MLP
will amend documents governing Subordinated Indebtedness unless approved in
writing by the Required Lenders (other than ministerial amendments and
amendments to extend the time or times for payment). The Borrower shall not make
any payments of interest or any other amounts in respect of the Subordinated
Indebtedness if a Default shall have occurred and be continuing or would result
from such payment. The Borrower will not repay any principal, interest or other
indebtedness in respect of the Subordinated Indebtedness, or make any redemption
or acquisition for value or defeasance, refinancing or exchange thereof or
therefore, or make any payments in contravention of the applicable Subordination
Agreement.

        7.17    Counterparty Consents.        In the event that the Borrower
delivers to the Administrative Agent a Counterparty Consent with respect to the
Blackhawk Pipeline, Hobbs Pipeline, Lake Whitney Pipeline or Rio Nogales
Pipeline, the Borrower may, at the time of such delivery of the Counterparty
Consent, request that the parentheticals set forth in Sections 7.04(d), 7.04(e),
and 7.04(f), and the restrictions set forth in Section 7.10, no longer apply to
the Subsidiary that owns such pipeline. Upon receipt of such Counterparty
Consent and such request, the Administrative Agent shall issue a notice to the
Borrower and the Lenders declaring that from and after the issuance of such
notice, the parenthetical set forth in Sections 7.04(d), 7.04(e), and 7.04(f),
and restrictions set forth in Section 7.10, no longer apply to such Subsidiary.

Remainder of this page intentionally left blank.

58

--------------------------------------------------------------------------------

ARTICLE VIII.
EVENTS OF DEFAULT AND REMEDIES

        8.01    Events of Default.    Any of the following shall constitute an
Event of Default:

        (a)    Non-Payment.    The Borrower fails to pay (i) when and as
required to be paid herein, any amount of principal of any Loan or any L/C
Obligation or (ii) within three Business Days after the same becomes due, any
interest on any Loan, any L/C Obligation, any commitment or other fee due
hereunder, or any other amount payable hereunder or under any other Loan
Document; or

        (b)    Specific Covenants.    The Borrower fails to perform or observe
any term, covenant or agreement contained in any of Section 6.03(a), 6.05 (with
respect to the Borrower's existence), 6.12, 6.15, 6.16, or Article VII; or

        (c)    Other Defaults.    Any Loan Party fails to perform or observe any
other covenant or agreement (not specified in subsection (a) or (b) above)
contained in any Loan Document on its part to be performed or observed and such
failure continues for 15 days after the earlier of (i) the date notice has been
given to the Borrower by the Administrative Agent or a Lender or (ii) the date a
Responsible Officer knew or reasonably should have known of such Default; or

        (d)    Representations and Warranties.    Any representation or warranty
made or deemed made by the Borrower or any other Loan Party herein, in any other
Loan Document, or in any document delivered in connection herewith or therewith
proves to have been incorrect in any material respect when made or deemed made;
or

        (e)    Cross-Default.    (i) The Borrower or any Borrower Affiliate
(A) fails to make any payment when due (whether by scheduled maturity, required
prepayment, acceleration, demand, or otherwise) in respect of any Indebtedness
or Guaranty Obligation (other than Indebtedness under Swap Contracts) having an
aggregate principal amount (or, in the case of a Capitalized Lease or a
Synthetic Lease Obligation, Attributable Indebtedness) (including undrawn or
available amounts and including amounts owing to all creditors under any
combined or syndicated credit arrangement) of more than (individually or
collectively) $5,000,000, or (B) fails to observe or perform any other agreement
or condition relating to any such Indebtedness or Guaranty Obligation or
contained in any instrument or agreement evidencing, securing or relating
thereto, or any other event occurs, the effect of which default or other event
is to cause, or to permit the holder or holders of such Indebtedness, the lessor
under such Synthetic Lease Obligation or the beneficiary or beneficiaries of
such Guaranty Obligation (or a trustee or agent on behalf of such holder or
holders or beneficiary or beneficiaries) to cause, with the giving of notice if
required, such Indebtedness to be demanded or to become due or to be repurchased
or redeemed (automatically or otherwise) prior to its stated maturity, or such
Guaranty Obligation to become payable or cash collateral in respect thereof to
be demanded; or (ii) (A) there occurs under any Swap Contract an Early
Termination Date (as defined in such Swap Contract) resulting from any event of
default under such Swap Contract as to which the Borrower or any Borrower
Affiliate is the Defaulting Party (as defined in such Swap Contract) and the
Swap Termination Value owed by the Borrower or any Borrower Affiliate as a
result thereof is greater than (individually or collectively) $5,000,000, or
(B) there occurs under any Swap Contract an Early Termination Date (as defined
in such Swap Contract) resulting from any Termination Event (as so defined)
under such Swap Contract as to which the Borrower or any Borrower Affiliate is
an Affected Party (as so defined) and the Early Termination Amount owed by the
Borrower and Borrower Affiliate as a result thereof is greater than
(individually or collectively) $5,000,000 and such amount is not paid when due
under such Swap Contract; or

59

--------------------------------------------------------------------------------

        (f)    Insolvency Proceedings, Etc.    (i) The Borrower or any Borrower
Affiliate institutes or consents to the institution of any proceeding under any
Debtor Relief Law, or makes an assignment for the benefit of creditors; or
applies for or consents to the appointment of any receiver, trustee, custodian,
conservator, liquidator, rehabilitator or similar officer for it or for all or
any material part of its property or takes any action to effect any of the
foregoing; or (ii) any receiver, trustee, custodian, conservator, liquidator,
rehabilitator or similar officer is appointed without the application or consent
of such Person and the appointment continues undischarged or unstayed for 60
calendar days; or (iii) any proceeding under any Debtor Relief Law relating to
any such Person or to all or any part of its property is instituted without the
consent of such Person and continues undismissed or unstayed for 60 calendar
days, or an order for relief is entered in any such proceeding; or

        (g)    Inability to Pay Debts; Attachment.    (i) The Borrower or any
Borrower Affiliate becomes unable or admits in writing its inability or fails
generally to pay its debts as they become due, or (ii) any writ or warrant of
attachment or execution or similar process is issued or levied against property
which is a material part of the property of the Borrower and its Subsidiaries
taken as a whole, and is not released, vacated or fully bonded within 45 days
after its issue or levy; or

        (h)    Judgments.    There is entered against the Borrower or any
Borrower Affiliate (i) a final judgment or order for the payment of money in an
aggregate amount exceeding (individually or collectively) $5,000,000 (to the
extent not covered by third-party insurance as to which the insurer does not
dispute coverage), or (ii) any non-monetary final judgment that has or could
reasonably be expected to have a Material Adverse Effect and, in either case,
(A) enforcement proceedings are commenced by any creditor upon such judgment or
order, or (B) there is a period of 3 0 consecutive days during which a stay of
enforcement of such judgment, by reason of a pending appeal or otherwise, is not
in effect; or

        (i)    ERISA.    (i) If the Borrower, any Borrower Affiliate or any of
their ERISA Affiliates maintains any Pension Plan or any Multiemployer Plan, an
ERISA Event occurs with respect to a Pension Plan or Multiemployer Plan which
has resulted or could reasonably be expected to result in liability of the
Borrower or any Borrower Affiliate under Title IV of ERISA to the Pension Plan,
Multiemployer Plan or the PBGC in an aggregate amount in excess of $3,500,000,
or (ii) if there is any Multiemployer Plan, the Borrower, any Borrower Affiliate
or any ERISA Affiliate thereof fails to pay when due, after the expiration of
any applicable grace period, any installment payment with respect to its
withdrawal liability under Section 4201 of ERISA under a Multiemployer Plan in
an aggregate amount in excess of $3,500,000; or

        (j)    Invalidity of Loan Documents.    Any Loan Document, at any time
after its execution and delivery and for any reason other than the agreement of
all the Lenders or termination of all Commitments and satisfaction in full of
all the Obligations, ceases to be in full force and effect, or is declared by a
court of competent jurisdiction to be null and void, invalid or unenforceable in
any material respect; or any Loan Party denies that it has any or further
liability or obligation under any Loan Document, or purports to revoke,
terminate or rescind any Loan Document; or

        (k)    Change of Control.    There occurs any Change of Control; or

        (l)    Dissolution.    The Borrower or any Borrower Affiliate shall
dissolve, liquidate, or otherwise terminate its existence, except as permitted
in Section 7.06; or

        (m)    Material Agreements.    (i) Termination of any Material
Agreement, or any material provision of any of the foregoing if such termination
could reasonably be expected to have a Material Adverse Effect and such
agreement or provision is not replaced (prior to such cessation) in a manner
satisfactory to the Agents; (ii) default by any Person in the performance or
observance of any material term of any Material Agreement which is not cured
within the applicable cure

60

--------------------------------------------------------------------------------

period specified in such Material Agreement, if such default could reasonably be
expected to have a Material Adverse Effect; or (iii) any event or condition
occurs or exists which in the opinion of the Agents is reasonably likely to
(x) have a material adverse effect on the ability of a MarkWest Party to perform
its obligations under a Material Agreement and (y) result in a Material Adverse
Effect hereunder; or

        (n)    Collateral; Impairment of Security, etc.    (i) Any provision of
any Loan Document shall for any reason cease to be valid and binding on or
enforceable against a Loan Party or any Loan Party shall so state in writing or
bring an action to limit its obligations or liabilities thereunder; or (ii) any
Collateral Document shall for any reason (other than pursuant to the terms
thereof) cease to create a valid security interest in the Collateral purported
to be covered thereby or such security interest shall for any reason cease to be
a perfected and first priority security interest subject to Permitted Liens; or
(iii) any provision of a Subordination Agreement shall cease to be effective or
shall not be enforceable, or any holder of Subordinated Indebtedness shall seek
to invalidate any provision of a Subordination Agreement.

        8.02    Remedies Upon Event of Default.    If any Event of Default
occurs, the Administrative Agent shall, at the request of, or may, with the
consent of, the Required Lenders:

        (a)   declare the commitment of each Lender to make Loans and any
obligation of the L/C Issuer to make L/C Credit Extensions to be terminated,
whereupon such commitments and obligations shall be terminated;

        (b)   declare the unpaid principal amount of all outstanding Loans, all
interest accrued and unpaid thereon, and all other amounts owing or payable
hereunder or under any other Loan Document to be immediately due and payable,
without presentment, demand, protest, notice of intent to accelerate, notice of
acceleration or other notice of any kind, all of which are hereby expressly
waived by the Borrower;

        (c)   declare that an amount equal to the then Outstanding Amount of all
L/C Obligations be immediately due and payable by the Borrower, without
presentment, demand, protest, notice of intent to accelerate, notice of
acceleration or other notice of any kind, all of which are hereby expressly
waived by the Borrower, and require that the Borrower deliver such payments to
the Administrative Agent to Cash Collateralize the L/C Obligations (in an amount
equal to the then Outstanding Amount thereof); and

        (d)   exercise on behalf of itself and the Lenders all rights and
remedies available to it and the Lenders under the Loan Documents or applicable
law;

provided, however, that upon the occurrence of any event specified in subsection
(f) of Section 8.01, the obligation of each Lender to make Loans and any
obligation of the L/C Issuer to make L/C Credit Extensions shall automatically
terminate, the unpaid principal amount of all outstanding Loans and all interest
and other amounts as aforesaid shall automatically become due and payable, and
an amount equal to the then Outstanding Amount of all L/C Obligations shall be
deemed to be forthwith due and owing by the Borrower to the L/C Issuer and the
Lenders as of the date of such occurrence and the Borrower's obligation to pay
such amounts shall be absolute and unconditional, without regard to whether any
beneficiary of any such Letter of Credit has attempted to draw down all or a
portion of such amount under the terms of a Letter of Credit and, to the fullest
extent permitted by applicable law, shall not be subject to any defense or be
affected by a right of set-off, counterclaim or recoupment which the Borrower
may now or hereafter have against any such beneficiary, the L/C Issuer, the
Administrative Agent, the Lenders or any other Person for any reason whatsoever.
Such payments shall be delivered to and held by the Administrative Agent as cash
collateral securing the L/C Obligations.

Remainder of this page intentionally left blank.

61

--------------------------------------------------------------------------------

ARTICLE IX.
ADMINISTRATIVE AGENT

        9.01    Appointment and Authorization of Agents; Lender Hedging
Agreements.    (a) Each Lender hereby irrevocably (subject to Section 9.10)
appoints, designates and authorizes the each Agent to take such action on its
behalf under the provisions of this Agreement and each other Loan Document and
to exercise such powers and perform such duties as are expressly delegated to it
by the terms of this Agreement or any other Loan Document, together with such
powers as are reasonably incidental thereto. Notwithstanding any provision to
the contrary contained elsewhere herein or in any other Loan Document, no Agent
shall have any duties or responsibilities, except those expressly set forth
herein, nor shall any Agent have or be deemed to have any fiduciary relationship
with any Lender or participant, and no implied covenants, functions,
responsibilities, duties, obligations or liabilities shall be read into this
Agreement or any other Loan Document or otherwise exist against any Agent.
Without limiting the generality of the foregoing sentence, the use of the term
"agent" herein and in the other Loan Documents with reference to the
Administrative Agent or Syndication Agent is not intended to connote any
fiduciary or other implied (or express) obligations arising under agency
doctrine of any applicable law. Instead, such term is used merely as a matter of
market custom, and is intended to create or reflect only an administrative
relationship between independent contracting parties.

        (b)   The L/C Issuer shall act on behalf of the Lenders with respect to
any Letters of Credit issued by it and the documents associated therewith until
such time (and except for so long) as the Administrative Agent may agree at the
request of the Required Lenders to act for the L/C Issuer with respect thereto;
provided, however, that the L/C Issuer shall have all of the benefits and
immunities (i) provided to the Administrative Agent in this Article IX with
respect to any acts taken or omissions suffered by the L/C Issuer in connection
with Letters of Credit issued by it or proposed to be issued by it and the
application and agreements for letters of credit pertaining to the Letters of
Credit as fully as if the term "Administrative Agent" as used in this Article IX
included the L/C Issuer with respect to such acts or omissions, and (ii) as
additionally provided herein with respect to the L/C Issuer.

        (c)   To the extent any Lender or any Affiliate of a Lender is a party
to a Lender Hedging Agreement and accepts the benefits of the Liens in the
Collateral arising pursuant to the Collateral Documents, such Lender (for itself
and on behalf of any such Affiliates) shall be deemed (i) to appoint the
Administrative Agent, as its nominee and agent, to act for and on behalf of such
Lender or Affiliate thereof in connection with the Collateral Documents and
(ii) to be bound by the terms of this Article IX.

        9.02    Delegation of Duties.    The Agents may execute any of their
respective duties under this Agreement or any other Loan Document by or through
agents, employees or attorneys-in-fact and shall be entitled to advice of
counsel and other consultants or experts concerning all matters pertaining to
such duties. No Agent shall be responsible for the negligence or misconduct of
any agent or attorney-in-fact that it selects in the absence of gross negligence
or willful misconduct.

        9.03    Default; Collateral.    (a) Upon the occurrence and continuance
of a Default or Event of Default, the Lenders agree to promptly confer in order
that Required Lenders or the Lenders, as the case may be, may agree upon a
course of action for the enforcement of the rights of the Lenders; and the
Administrative Agent shall be entitled to refrain from taking any action
(without incurring any liability to any Person for so refraining) unless and
until the Administrative Agent shall have received instructions from Required
Lenders. All rights of action under the Loan Documents and all right to the
Collateral, if any, hereunder may be enforced by the Administrative Agent and
any suit or proceeding instituted by the Administrative Agent in furtherance of
such enforcement shall be brought in its name as the Administrative Agent
without the necessity of joining as plaintiffs or defendants any other Lender,
and the recovery of any judgment shall be for the benefit of the Lenders (and,
with respect to

62

--------------------------------------------------------------------------------

Lender Hedging Agreements, Affiliates, if applicable) subject to the expenses of
the Administrative Agent. In actions with respect to any property of the
Borrower or any other Obligor, the Administrative Agent is acting for the
ratable benefit of each Lender (and, with respect to Lender Hedging Agreement,
Affiliates, if applicable). Any and all agreements to subordinate (whether made
heretofore or hereafter) other indebtedness or obligations of Borrower to the
Obligation shall be construed as being for the ratable benefit of each Lender
(and, with respect to Lender Hedging Agreement, Affiliates, if applicable).

        (b)   Each Lender authorizes and directs the Administrative Agent to
enter into the Collateral Documents on behalf of and for the benefit of the
Lenders (and, with respect to Lender Hedging Agreements, Affiliates, if
applicable)(or if previously entered into, hereby ratifies the Administrative
Agent's previously entering into such agreements and Collateral Documents).

        (c)   Except to the extent unanimity (or other percentage set forth in
Section 10.1) is required hereunder, each Lender agrees that any action taken by
the Required Lenders in accordance with the provisions of the Loan Documents,
and the exercise by the Required Lenders of the power set forth herein or
therein, together with such other powers as are reasonably incidental thereto,
shall be authorized and binding upon all of the Lenders.

        (d)   The Administrative Agent is hereby authorized on behalf of the
Lenders, without the necessity of any notice to or further consent from any
Lender, from time to time to take any action with respect to any Collateral or
Collateral Documents which may be necessary to perfect and maintain perfected
the Liens upon the Collateral granted pursuant to the Collateral Documents.

        (e)   The Administrative Agent shall have no obligation whatsoever to
any Lender or to any other Person to assure that the Collateral exists or is
owned by any Obligor or is cared for, protected, or insured or has been
encumbered or that the Liens granted to the Administrative Agent herein or
pursuant thereto have been properly or sufficiently or lawfully created,
perfected, protected, or enforced, or are entitled to any particular priority,
or to exercise at all or in any particular manner or under any duty of care,
disclosure, or fidelity, or to continue exercising, any of the Rights granted or
available to the Administrative Agent in this Section 9.03 or in any of the
Collateral Documents; it being understood and agreed that in respect of the
Collateral, or any act, omission, or event related thereto, the Administrative
Agent may act in any manner it may deem appropriate, in its sole discretion,
given the Administrative Agent's own interest in the Collateral as one of the
Lenders and that the Administrative Agent shall have no duty or liability
whatsoever to any Lender, other than to act without gross negligence or willful
misconduct.

        (f)    The Lenders hereby irrevocably authorize the Administrative
Agent, at its option and in its discretion, to release any Lien granted to or
held by the Administrative Agent upon any Collateral: (i) constituting property
in which no Obligor owned an interest at the time the Lien was granted or at any
time thereafter; (ii) constituting property leased to an Obligor under a lease
which has expired or been terminated in a transaction permitted under the Loan
Document or is about to expire and which has not been, and is not intended by
such Obligor to be, renewed; and (iii) consisting of an instrument evidencing
Indebtedness pledged to the Administrative Agent (for the benefit of the
Lenders), if the Indebtedness evidenced thereby has been paid in full. In
addition, the Lenders irrevocably authorize the Administrative Agent to release
Liens upon Collateral as contemplated in Section 10.01(c) or (d), or if
approved, authorized, or ratified in writing by the requisite Lenders. Upon
request by the Administrative Agent at any time, the Lenders will confirm in
writing the Administrative Agent's authority to release particular types or
items of Collateral pursuant to this Section 9.03.

        (g)   In furtherance of the authorizations set forth in this
Section 9.03, each Lender hereby irrevocably appoints the Administrative Agent
its attorney-in-fact, with full power of substitution,

63

--------------------------------------------------------------------------------

for and on behalf of and in the name of each such Lender, (i) to enter into
Collateral Documents (including, without limitation, any appointments of
substitute trustees under any Collateral Documents), (ii) to take action with
respect to the Collateral and Collateral Documents to perfect, maintain, and
preserve Lenders' Liens, and (iii) to execute instruments of release or to take
other action necessary to release Liens upon any Collateral to the extent
authorized in paragraph (e) hereof. This power of attorney shall be liberally,
not restrictively, construed so as to give the greatest latitude to the
Administrative Agent's power, as attorney, relative to the Collateral matters
described in this Section 9.03. The powers and authorities herein conferred on
the Administrative Agent may be exercised by the Administrative Agent through
any Person who, at the time of the execution of a particular instrument, is an
officer of the Administrative Agent. The power of attorney conferred by this
Section 9.03(g) is granted for valuable consideration and is coupled with an
interest and is irrevocable so long as the Obligations, or any part thereof,
shall remain unpaid or the Lenders are obligated to make any Borrowings under
the Loan Documents.

        9.04    Liability of Agents.    No Agent-Related Person shall (a) be
liable for any action taken or omitted to be taken by any of them under or in
connection with this Agreement or any other Loan Document or the transactions
contemplated hereby (except for its own gross negligence or willful misconduct
in connection with its duties expressly set forth herein), or (b) be responsible
in any manner to any Lender or participant for any recital, statement,
representation or warranty made by any Loan Party or any officer thereof,
contained herein or in any other Loan Document, or in any certificate, report,
statement or other document referred to or provided for in, or received by any
Agent under or in connection with, this Agreement or any other Loan Document, or
the validity, effectiveness, genuineness, enforceability or sufficiency of this
Agreement or any other Loan Document, or for the creation, perfection or
priority of any Liens purported to be created by any of the Loan Documents, or
the validity, genuineness, enforceability, existence, value or sufficiency of
any collateral security, or to make any inquiry respecting the performance by
the Borrower of its obligations hereunder or under any other Loan Document, or
for any failure of any Loan Party or any other party to any Loan Document to
perform its obligations hereunder or thereunder. No Agent-Related Person shall
be under any obligation to any Lender or participant to ascertain or to inquire
as to the observance or performance of any of the agreements contained in, or
conditions of, this Agreement or any other Loan Document, or to inspect the
properties, books or records of any Loan Party or any Affiliate thereof.

        9.05    Reliance by Administrative Agent.    (a) The Administrative
Agent shall be entitled to rely, and shall be fully protected in relying, upon
any writing, communication, signature, resolution, representation, notice,
consent, certificate, affidavit, letter, telegram, facsimile, telex or telephone
message, statement or other document or conversation believed by it to be
genuine and correct and to have been signed, sent or made by the proper Person
or Persons, and upon advice and statements of legal counsel (including counsel
to any Loan Party), independent accountants and other experts selected by the
Administrative Agent. The Administrative Agent shall be fully justified in
failing or refusing to take any action under any Loan Document unless it shall
first receive such advice or concurrence of the Required Lenders as it deems
appropriate and, if it so requests, it shall first be indemnified to its
satisfaction by the Lenders against any and all liability and expense which may
be incurred by it by reason of taking or continuing to take any such action. The
Administrative Agent shall in all cases be fully protected in acting, or in
refraining from acting, under this Agreement or any other Loan Document in
accordance with a request or consent of the Required Lenders or all the Lenders,
if required hereunder, and such request and any action taken or failure to act
pursuant thereto shall be binding upon all the Lenders and participants. Where
this Agreement expressly permits or prohibits an action unless the Required
Lenders otherwise determine, the Administrative Agent shall, and in all other
instances, the Administrative Agent may, but shall not be required to, initiate
any solicitation for the consent or a vote of the Lenders.

64

--------------------------------------------------------------------------------

        (b)   For purposes of determining compliance with the conditions
specified in Section 4.02, each Lender that has funded its Pro Rata Share of the
Borrowing(s) on the Restatement Date (or, if there is no Borrowing made on such
date, each Lender other than Lenders who gave written objection to the
Administrative Agent prior to such date) shall be deemed to have consented to,
approved or accepted or to be satisfied with, each document or other matter
either sent by the Administrative Agent to such Lender for consent, approval,
acceptance or satisfaction, or required hereunder to be consented to or approved
by or acceptable or satisfactory to a Lender.

        9.06    Notice of Default.    The Administrative Agent shall not be
deemed to have knowledge or notice of the occurrence of any Default or Event of
Default, except with respect to defaults in the payment of principal, interest
and fees required to be paid to the Administrative Agent for the account of the
Lenders, unless the Administrative Agent shall have received written notice from
a Lender or the Borrower referring to this Agreement, describing such Default or
Event of Default and stating that such notice is a "notice of default." The
Administrative Agent will notify the Lenders of its receipt of any such notice.
The Administrative Agent shall take such action with respect to such Default or
Event of Default as may be directed by the Required Lenders in accordance with
Article VIII; provided, however, that unless and until the Administrative Agent
has received any such direction, the Administrative Agent may (but shall not be
obligated to) take such action, or refrain from taking such action, with respect
to such Default or Event of Default as it shall deem advisable or in the best
interest of the Lenders.

        9.07    Credit Decision; Disclosure of Information by Administrative
Agent.    Each Lender acknowledges that no Agent-Related Person has made any
representation or warranty to it, and that no act by any Agent hereinafter
taken, including any consent to and acceptance of any assignment or review of
the affairs of any Loan Party or any Affiliate thereof, shall be deemed to
constitute any representation or warranty by any Agent-Related Person to any
Lender as to any matter, including whether Agent- Related Persons have disclosed
material information in their possession. Each Lender represents to each Agent
that it has, independently and without reliance upon any Agent-Related Person
and based on such documents and information as it has deemed appropriate, made
its own appraisal of and investigation into the business, prospects, operations,
property, financial and other condition and creditworthiness of the Loan Parties
and their respective Subsidiaries, and all applicable bank or other regulatory
Laws relating to the transactions contemplated hereby, and made its own decision
to enter into this Agreement and to extend credit to the Borrower hereunder.
Each Lender also represents that it will, independently and without reliance
upon any Agent-Related Person and based on such documents and information as it
shall deem appropriate at the time, continue to make its own credit analysis,
appraisals and decisions in taking or not taking action under this Agreement and
the other Loan Documents, and to make such investigations as it deems necessary
to inform itself as to the business, prospects, operations, property, financial
and other condition and creditworthiness of the Borrower and the other Loan
Parties. Except for notices, reports and other documents expressly required to
be furnished to the Lenders by the Administrative Agent herein, the
Administrative Agent shall not have any duty or responsibility to provide any
Lender with any credit or other information concerning the business, prospects,
operations, property, financial and other condition or creditworthiness of any
of the Loan Parties or any of their respective Affiliates which may come into
the possession of any Agent Related Person.

        9.08    Indemnification of Agents.    Whether or not the transactions
contemplated hereby are consummated, the Lenders shall indemnify upon demand
each Agent-Related Person (to the extent not reimbursed by or on behalf of any
Loan Party and without limiting the obligation of any Loan Party to do so), pro
rata, and hold harmless each Agent-Related Person from and against any and all
Indemnified Liabilities incurred by it; provided, however, that no Lender shall
be liable for the payment to any Agent-Related Person of any portion of such
Indemnified Liabilities resulting from such Person's gross negligence or willful
misconduct; provided, however, that no action taken in accordance with the

65

--------------------------------------------------------------------------------

directions of the Required Lenders shall be deemed to constitute gross
negligence or willful misconduct for purposes of this Section. Without
limitation of the foregoing, each Lender shall reimburse the Administrative
Agent upon demand for its ratable share of any costs or out-of-pocket expenses
(including Attorney Costs) incurred by the Administrative Agent in connection
with the preparation, execution, delivery, administration, modification,
amendment or enforcement (whether through negotiations, legal proceedings or
otherwise) of, or legal advice in respect of rights or responsibilities under,
this Agreement, any other Loan Document, or any document contemplated by or
referred to herein, to the extent that the Administrative Agent is not
reimbursed for such expenses by or on behalf of the Borrower. The undertaking in
this Section shall survive termination of the Commitments, the payment of all
Obligations hereunder and the resignation or replacement of the Administrative
Agent.

        9.09    Administrative Agent in its Individual Capacity.    Royal Bank
of Canada and its Affiliates may make loans to, accept deposits from, acquire
equity interests in and generally engage in any kind of banking, trust,
financial advisory, underwriting or other business with each of the Loan Parties
and their respective Affiliates as though Royal Bank of Canada were not the
Administrative Agent or the L/C Issuer hereunder and without notice to or
consent of the Lenders. The Lenders acknowledge that, pursuant to such
activities, Royal Bank of Canada or its Affiliates may receive information
regarding any Loan Party or its Affiliates (including information that may be
subject to confidentiality obligations in favor of such Loan Party or such
Affiliate) and acknowledge that the Administrative Agent shall be under no
obligation to provide such information to them. With respect to its Loans, Royal
Bank of Canada shall have the same rights and powers under this Agreement as any
other Lender and may exercise such rights and powers as though it were not the
Administrative Agent or the L/C Issuer, and the terms "Lender" and "Lenders"
include Royal Bank of Canada in its individual capacity.

        9.10    Successor Administrative Agent.    The Administrative Agent may
resign as Administrative Agent upon 30 days' notice to the Lenders with a copy
of such notice to the Borrower. If the Administrative Agent resigns under this
Agreement, the Required Lenders shall appoint from among the Lenders a successor
administrative agent for the Lenders which successor administrative agent shall
be consented to by the Borrower at all times other than during the existence of
an Event of Default (which consent of the Borrower shall not be unreasonably
withheld or delayed). If no successor administrative agent is appointed prior to
the effective date of the resignation of the Administrative Agent, the
Administrative Agent may appoint, after consulting with the Lenders and the
Borrower, a successor administrative agent from among the Lenders. Upon the
acceptance of its appointment as successor administrative agent hereunder, such
successor administrative agent shall succeed to all the rights, powers and
duties of the retiring Administrative Agent and the term "Administrative Agent"
shall mean such successor administrative agent and the retiring Administrative
Agent's appointment, powers and duties as Administrative Agent shall be
terminated. After any retiring Administrative Agent's resignation hereunder as
Administrative Agent, the provisions of this Article IX and Sections 10.03 and
10.13 shall inure to its benefit as to any actions taken or omitted to be taken
by it while it was Administrative Agent under this Agreement. If no successor
administrative agent has accepted appointment as Administrative Agent by the
date which is 30 days following a retiring Administrative Agent's notice of
resignation, the retiring Administrative Agent's resignation shall nevertheless
thereupon become effective and the Lenders shall perform all of the duties of
the Administrative Agent hereunder until such time, if any, as the Required
Lenders appoint a successor agent as provided for above.

        9.11    Syndication Agent; Other Agents; Arrangers.    None of the
Lenders or other Persons identified on the facing page or signature pages of
this Agreement as a "syndication agent," as an "co-documentation agent," any
other type of agent (other than the Administrative Agent and the Syndication
Agent), "co- arranger," or "book manager" shall have any right, power,
obligation, liability, responsibility or duty under this Agreement other than
those applicable to all Lenders as such. Without limiting the foregoing, none of
the Lenders so identified shall have or be deemed to have any fiduciary
relationship with any Lender. Each Lender acknowledges that it has not relied,
and will not rely, on any of the Lenders so identified in deciding to enter into
this Agreement or in taking or not taking action hereunder.

Remainder of this page intentionally left blank.

66

--------------------------------------------------------------------------------

ARTICLE X.
MISCELLANEOUS

        10.01    Amendments, Release of Collateral, Etc.    (a) No amendment or
waiver of any provision of this Agreement or any other Loan Document, and no
consent to any departure by the Borrower or any other Loan Party therefrom,
shall be effective unless in writing signed by the Required Lenders and the
Borrower or the applicable Loan Party, as the case may be, and acknowledged by
the Administrative Agent, and each such waiver or consent shall be effective
only in the specific instance and for the specific purpose for which given;
provided, however, that no such amendment, waiver or consent shall, unless in
writing and signed by each of the Lenders directly affected thereby and by the
Borrower, and acknowledged by the Administrative Agent, do any of the following:

        (i)    extend or increase the Commitment of any Lender (or reinstate any
Commitment terminated pursuant to Section 8.02);

        (ii)   postpone or delay any date fixed by this Agreement or any other
Loan Document for any payment or mandatory prepayment of principal, interest,
fees or other amounts due to the Lenders (or any of them) hereunder or under any
other Loan Document;

        (iii)  reduce the principal of, or the rate of interest specified herein
on, any Loan or L/C Borrowing or (subject to clause (ii) of the proviso below)
any fees or other amounts payable hereunder or under any other Loan Document,
provided, however, that only the consent of the Required Lenders shall be
necessary to amend the definition of "Default Rate" or to waive any obligation
of the Borrower to pay interest at the Default Rate;

        (iv)  change the percentage of the Aggregate Commitments or of the
aggregate unpaid principal amount of the Loans and L/C Obligations which is
required for the Lenders or any of them to take any action hereunder;

        (v)   change the Pro Rata Share of any Lender;

        (vi)  release a material amount of Collateral or release any Guarantor
from a Guaranty (except in connection with a Disposition permitted under
Section 7.07 or as otherwise permitted under this Section 10.01); or

        (vii) amend this Section, or Section 2.12, or any provision herein
providing for unanimous consent or other action by all the Lenders;

and, provided further, that (i) no amendment, waiver or consent shall, unless in
writing and signed by the L/C Issuer in addition to the Required Lenders or all
the Lenders, as the case may be, affect the rights or duties of the L/C Issuer
under this Agreement or any Letter of Credit Application relating to any Letter
of Credit issued or to be issued by it; (ii) no amendment, waiver or consent
shall, unless in writing and signed by the Administrative Agent in addition to
the Required Lenders or all the Lenders, as the case may be, affect the rights
or duties of the Administrative Agent under this Agreement or any other Loan
Document; and (iii) the Agent/Arranger Fee Letter may be amended, or rights or
privileges thereunder waived, in a writing executed only by the parties thereto.
Notwithstanding anything to the contrary herein, any Lender that has failed to
fund any portion of the Loans or participation in L/C Obligations required to be
funded by it hereunder shall not have any right to approve or disapprove any
amendment, waiver or consent hereunder, except that the Pro Rata Share of such
Lender may not be increased without the consent of such Lender.

        (b)   Any amendment to any Loan Document which purports to (i) decrease
the amount of any mandatory prepayment or commitment reduction required by
Section 2.04 or (ii) change this Section 10.01(b), must be by an instrument in
writing executed by Borrower, the Administrative Agent, and the Required
Lenders.

67

--------------------------------------------------------------------------------

        (c)   Upon any sale, transfer, or disposition of Collateral which is
permitted pursuant to the Loan Documents, and upon ten (10) Business Days' prior
written request by the Borrower (which request must be accompanied by (a) true
and correct copies of all material documents of transfer or disposition,
including any contract of sale, (ii) a preliminary closing statement and
instructions to the title company, if any, (iii) all requested release
instruments in form and substance satisfactory to the Administrative Agent) and
(iv) if required, written consent of the requisite Lenders, the Administrative
Agent shall (and is hereby irrevocably authorized by the Lenders to) execute
such documents as may be necessary to evidence the release of Liens granted to
the Administrative Agent for the benefit of the Lenders pursuant hereto in such
Collateral. The Administrative Agent shall not be required to execute any
release instruments on terms which, in the Administrative Agent's opinion, would
expose the Administrative Agent to liability or create any obligation or entail
any consequence other than the release of liens without recourse or warranty. No
such release shall impair the Administrative Agent's lien on the proceeds of
sale of such Collateral.

        (d)   If all outstanding Loans and other Obligations have been
indefeasibly paid in full and the Commitments have terminated or have been
reduced to zero, and, subject to Section 10.01(e) all Lender Hedging Agreement
have terminated, the Administrative Agent agrees to, and the Lenders hereby
instruct the Administrative Agent to, at the Borrower's expense, execute and
authorize such releases of the Collateral Documents as the Borrower shall
reasonably request and this Agreement shall be deemed terminated except that
such termination shall not relieve the Borrower of any obligation to make any
payments to the Administrative Agent or any Lender required by any Loan Document
to the extent accruing, or relating to an event occurring, prior to such
termination.

        (e)   Notwithstanding any provision herein to the contrary, if the
Commitments have been terminated, and the only outstanding Obligations are
amounts owed pursuant to one or more Lender Hedging Agreements, the
Administrative Agent will, and is hereby authorized to, (A) release the Liens
created under the Loan Documents and (B) release all Guaranties of the Borrower,
provided, that contemporaneously with such release, (i) the Borrower (and, if
applicable, the Subsidiary that is a party to such Lender Hedging Agreements)
(A) executes a margin agreement in form and substance acceptable to such
Lender(s) (or its Affiliates) that are parties to such Lender Hedging Agreements
(the "Lender Counterparties") and (B), if required, provides collateral in the
form of cash or a letter of credit having an aggregate value acceptable to such
Lender Counterparties, and (ii) if such Lender Hedging Agreement is executed by
a Subsidiary of the Borrower and the Borrower and the MLP are not parties
thereto, the Borrower and the MLP execute a guaranty covering such Subsidiary's
obligations thereunder, such guaranty to be in form and substance satisfactory
to the Lender Counterparties. Any release under this Section 10.01(e) must be in
writing and signed by the Administrative Agent.

        10.02    Notices and Other Communications; Facsimile Copies.    

        (a)    General.    Unless otherwise expressly provided herein, all
notices and other communications provided for hereunder and under the other Loan
Documents shall be in writing (including by facsimile transmission) and mailed,
faxed or delivered, to the address, facsimile number or (subject to subsection
(c) below) electronic mail address specified for notices on Schedule 10.02 (for
the Borrower, any Guarantor and the Administrative Agent) or on the
Administrative Details Form (for the other Lenders); or, in the case of the
Borrower, the Guarantors, the Administrative Agent, or the L/C Issuer, to such
other address as shall be designated by such party in a notice to the other
parties, and in the case of any other party, to such other address as shall be
designated by such party in a notice to the Borrower, the Administrative Agent
and the L/C Issuer. All such notices and other communications shall be deemed to
be given or made upon the earlier to occur of (i) actual receipt by the intended
recipient and (ii) (A) if delivered by hand or by courier, when signed for by
the intended recipient;

68

--------------------------------------------------------------------------------

(B) if delivered by mail, four Business Days after deposit in the mails, postage
prepaid; (C) if delivered by facsimile, when sent and receipt has been confirmed
by telephone; and (D) if delivered by electronic mail (which form of delivery is
subject to the provisions of subsection (c) below), when delivered; provided,
however, that notices and other communications to the Administrative Agent or
the L/C Issuer pursuant to Article II shall not be effective until actually
received by such Person. Any notice or other communication permitted to be
given, made or confirmed by telephone hereunder shall be given, made or
confirmed by means of a telephone call to the intended recipient at the number
specified in accordance with this Section, it being understood and agreed that a
voicemail message shall in no event be effective as a notice, communication or
confirmation hereunder.

        (b)    Effectiveness of Facsimile Documents and Signatures.    Loan
Documents may be transmitted and/or signed by facsimile. The effectiveness of
any such documents and signatures shall, subject to applicable Law, have the
same force and effect as manually-signed originals and shall be binding on all
Loan Parties, the Administrative Agent and the Lenders. The Administrative Agent
may also require that any such documents and signatures be confirmed by a
manually-signed original thereof; provided, however, that the failure to request
or deliver the same shall not limit the effectiveness of any facsimile document
or signature.

        (c)    Limited Use of Electronic Mail.    Electronic mail and internet
and intranet websites may be used only to distribute routine communications,
such as financial statements and other information, and to distribute Loan
Documents for execution by the parties thereto, and shall not be recognized
hereunder for any other purpose.

        (d)    Reliance by Administrative Agent and Lenders.    The
Administrative Agent and the Lenders shall be entitled to rely and act upon any
notices (including telephonic Borrowing Notices) purportedly given by or on
behalf of the Borrower even if (i) such notices were not made in a manner
specified herein, were incomplete or were not preceded or followed by any other
form of notice specified herein, or (ii) the terms thereof, as understood by the
recipient, varied from any confirmation thereof. The Borrower shall indemnify
each Agent-Related Person and each Lender from all losses, costs, expenses and
liabilities resulting from the reliance by such Person on each notice
purportedly given by or on behalf of the Borrower. All telephonic notices to and
other communications with the Administrative Agent may be recorded by the
Administrative Agent, and each of the parties hereto hereby consents to such
recording.

        10.03    No Waiver; Cumulative Remedies.    No failure by any Lender or
the Administrative Agent to exercise, and no delay by any such Person in
exercising, any right, remedy, power or privilege hereunder shall operate as a
waiver thereof; nor shall any single or partial exercise of any right, remedy,
power or privilege hereunder preclude any other or further exercise thereof or
the exercise of any other right, remedy, power or privilege. The rights,
remedies, powers and privileges herein or therein provided are cumulative and
not exclusive of any rights, remedies, powers and privileges provided by law.

        10.04    Attorney Costs; Expenses and Taxes.    The Borrower agrees
(a) to pay or reimburse the Administrative Agent for all costs and expenses
incurred in connection with the development, preparation, negotiation,
syndication, administration and execution of this Agreement and the other Loan
Documents, including the filing, recording, refiling or rerecording of any
Mortgage, any pledge agreement and any Security Agreement and/or any Uniform
Commercial Code financing statements relating thereto and all amendments,
supplements and modifications to any thereof and any and all other documents or
instruments of further assurance required to be filed or recorded or refiled or
rerecorded by the terms hereof or of any mortgage, any pledge agreement or any
security agreement, and any amendment, waiver, consent or other modification of
the provisions hereof and thereof (whether or not the transactions contemplated
hereby or thereby are consummated), and the

69

--------------------------------------------------------------------------------

consummation and administration of the transactions contemplated hereby and
thereby, including all Attorney Costs, and (b) to pay or reimburse the
Administrative Agent and each Lender for all costs and expenses incurred in
connection with the enforcement, attempted enforcement, or preservation of any
rights or remedies under this Agreement or the other Loan Documents (including
all such costs and expenses incurred during any workout or restructuring in
respect of the Obligations and during any legal proceeding, including any
proceeding under any Debtor Relief Law), including all Attorney Costs. The
foregoing costs and expenses shall include all search, filing, recording, title
insurance and appraisal charges and fees and taxes related thereto, and other
out-of-pocket expenses incurred by the Administrative Agent and the cost of
independent public accountants and other outside experts retained by the
Administrative Agent or any Lender. The agreements in this Section shall survive
the termination of the Commitments and repayment of all the other Obligations.

        10.05    Indemnification.    Whether or not the transactions
contemplated hereby are consummated, each of the Borrower, the MLP and each
other Guarantor (by execution of a Guaranty), jointly and severally, agrees to
indemnify, save and hold harmless each Agent-Related Person, the Syndication
Agent, each Arranger, each Lender, the L/C Issuer and their respective
Affiliates, directors, officers, employees, counsel, agents and
attorneys-in-fact (collectively the "Indemnitees") from and against: (a) any and
all claims, demands, actions or causes of action that are asserted against any
Indemnitee by any Person (other than the Administrative Agent or any Lender)
relating directly or indirectly to a claim, demand, action or cause of action
that such Person asserts or may assert against any Loan Party, any Affiliate of
any Loan Party or any of their respective officers or directors, arising out of
or relating to, the Loan Documents, the Commitments, the use or contemplated use
of the proceeds of any Loans, or the relationship of any Loan Party, the
Administrative Agent, the Syndication Agent, the Lenders and the L/C Issuer
under this Agreement or any other Loan Document; (b) any and all claims,
demands, actions or causes of action that may at any time (including at any time
following repayment of the Obligations and the resignation of the Administrative
Agent or the replacement of any Lender) be asserted or imposed against any
Indemnitee, arising out of or relating to, the Loan Documents, the Commitments,
the use or contemplated use of the proceeds of any Loans, or the relationship of
any Loan Party, the Administrative Agent, the Syndication Agent, the Lenders and
the L/C Issuer under this Agreement or any other Loan Document; (c) without
limiting the foregoing, any and all claims, demands, actions or causes of
action, judgments and orders, penalties and fines that are asserted or imposed
against any Indemnitee, (i) under the application of any Environmental Law
applicable to the Borrower or any of its Subsidiaries or any of their properties
or assets, including the treatment or disposal of Hazardous Substances on any of
their properties or assets, (ii) as a result of the breach or non-compliance by
the Borrower or any Subsidiary with any Environmental Law applicable to the
Borrower or any Subsidiary, (iii) due to past ownership by the Borrower or any
Subsidiary of any of their properties or assets or past activity on any of their
properties or assets which, though lawful and fully permissible at the time,
could result in present liability, (iv) due to the presence, use, storage,
treatment or disposal of Hazardous Substances on or under, or the escape,
seepage, leakage, spillage, discharge, emission or Release from, any of the
properties owned or operated by the Borrower or any Subsidiary (including any
liability asserted or arising under any Environmental Law), regardless of
whether caused by, or within the control of, the Borrower or such Subsidiary, or
(v) due to any other environmental, health or safety condition in connection
with the Loan Documents; (d) any administrative or investigative proceeding by
any Governmental Authority arising out of or related to a claim, demand, action
or cause of action described in subsection (a), (b) or (e) above; and (e) any
and all liabilities (including liabilities under indemnities), losses, costs or
expenses (including Attorney Costs and settlement costs) that any Indemnitee
suffers or incurs as a result of the assertion of any foregoing claim, demand,
action, cause of action or proceeding, or as a result of the preparation of any
defense in connection with any foregoing claim, demand, action, cause of action
or proceeding, in all cases, WHETHER OR NOT ARISING OUT OF THE STRICT LIABILITY
OR NEGLIGENCE OF AN INDEMNITEE, and whether or not an Indemnitee is a party to
such claim, demand, action, cause of

70

--------------------------------------------------------------------------------

action or proceeding (all the foregoing, collectively, the "Indemnified
Liabilities"); provided that no Indemnitee shall be entitled to indemnification
for any claim to the extent caused by its own gross negligence or willful
misconduct. The agreements in this Section shall survive and continue for the
benefit of the Indemnitees at all times after the Borrower's acceptance of the
Lenders' commitments for the Senior Credit Facility, whether or not the
Restatement Date shall occur and shall survive the termination of the
Commitments and repayment of all the other Obligations.

        10.06    Payments Set Aside.    To the extent that the Borrower makes a
payment to the Administrative Agent or any Lender, or the Administrative Agent
or any Lender exercises its right of setoff, and such payment or the proceeds of
such set-off or any part thereof is subsequently invalidated, declared to be
fraudulent or preferential, set aside or required (including pursuant to any
settlement entered into by the Administrative Agent or such Lender in its
discretion) to be repaid to a trustee, receiver or any other party, in
connection with any proceeding under any Debtor Relief Law or otherwise, then
(a) to the extent of such recovery, the obligation or part thereof originally
intended to be satisfied shall be revived and continued in full force and effect
as if such payment had not been made or such setoff had not occurred, and
(b) each Lender severally agrees to pay to the Administrative Agent upon demand
its applicable share of any amount so recovered from or repaid by the
Administrative Agent, plus interest thereon from the date of such demand to the
date such payment is made at a rate per annum equal to the Federal Funds Rate
from time to time in effect.

        10.07    Successors and Assigns.    

        (a)   The provisions of this Agreement shall be binding upon and inure
to the benefit of the parties hereto and their respective successors and assigns
permitted hereby, except that neither the Borrower nor the MLP may assign or
otherwise transfer any of its rights or obligations hereunder without the prior
written consent of each Lender and no Lender may assign or otherwise transfer
any of its rights or obligations hereunder except (i) to an Eligible Assignee in
accordance with the provisions of paragraph (b) of this Section, (ii) by way of
participation in accordance with the provisions of paragraph (d) of this Section
or (iii) by way of pledge or assignment of a security interest subject to the
restrictions of paragraph (f) of this Section (and any other attempted
assignment or transfer by any party hereto shall be null and void). Nothing in
this Agreement, expressed or implied, shall be construed to confer upon any
Person (other than the parties hereto, their respective successors and assigns
permitted hereby, Participants to the extent provided in paragraph (d) of this
Section and, to the extent expressly contemplated hereby, the Related Parties of
each of the Administrative Agent and the Lenders) any legal or equitable right,
remedy or claim under or by reason of this Agreement.

        (b)   Any Lender may at any time assign to one or more Eligible
Assignees all or a portion of its rights and obligations under this Agreement
(including all or a portion of its Commitment and the Loans (including for
purposes of this subsection (b), participations in L/C Obligations) at the time
owing to it); provided that (i) except in the case of an assignment of the
entire remaining amount of the assigning Lender's Commitment and the Loans at
the time owing to it or in the case of an assignment to a Lender or an Affiliate
of a Lender or an Approved Fund with respect to a Lender, the aggregate amount
of the Commitment (which for this purpose includes Loans outstanding thereunder)
or, if the applicable Commitment is not then in effect, the outstanding
principal balance of the Loan of the assigning Lender subject to each such
assignment (determined as of the date the Assignment and Assumption with respect
to such assignment is delivered to the Administrative Agent or, if "Trade Date"
is specified in the Assignment and Assumption, as of the Trade Date) shall not
be less than $5,000,000, unless each of the Administrative Agent and, so long as
no Default has occurred and is continuing, the Borrower otherwise consent (each
such consent not to be unreasonably withheld or delayed); (ii) each partial
assignment shall be made as an assignment of a proportionate part of all the
assigning Lender's rights and obligations under this Agreement with respect to
the Loan or the Commitment assigned, and (iii) the parties to each

71

--------------------------------------------------------------------------------

assignment shall execute and deliver to the Administrative Agent an Assignment
and Assumption, together with a processing and recordation fee of $3,500, and
the Eligible Assignee, if it shall not be a Lender, shall deliver to the
Administrative Agent an Administrative Details Form. Subject to acceptance and
recording thereof by the Administrative Agent pursuant to paragraph (c) of this
Section, from and after the effective date specified in each Assignment and
Assumption, the Eligible Assignee thereunder shall be a party to this Agreement
and, to the extent of the interest assigned by such Assignment and Assumption,
have the rights and obligations of a Lender under this Agreement, and the
assigning Lender thereunder shall, to the extent of the interest assigned by
such Assignment and Assumption, be released from its obligations under this
Agreement (and, in the case of an Assignment and Assumption covering all of the
assigning Lender's rights and obligations under this Agreement, such Lender
shall cease to be a party hereto) but shall continue to be entitled to the
benefits of Sections 3.07, 10.04 and 10.05 with respect to facts and
circumstances occurring prior to the effective date of such assignment. Any
assignment or transfer by a Lender of rights or obligations under this Agreement
that does not comply with this paragraph shall be treated for purposes of this
Agreement as a sale by such Lender of a participation in such rights and
obligations in accordance with paragraph (d) of this Section. Upon the
occurrence and during the continuance of an Event of Default all restrictions on
assignment by any Lender shall cease, including all restrictive clauses driven
by withholding tax considerations.

        (c)   The Administrative Agent, acting solely for this purpose as an
agent of the Borrower, shall maintain at one of its offices a copy of each
Assignment and Assumption delivered to it and a register for the recordation of
the names and addresses of the Lenders, and the Commitments of, and principal
amounts of the Loans and L/C Obligations owing to, each Lender pursuant to the
terms hereof from time to time (the "Register"). The entries in the Register
shall be conclusive absent manifest error, and the Borrower, the Administrative
Agent and the Lenders may treat each Person whose name is recorded in the
Register pursuant to the terms hereof as a Lender hereunder for all purposes of
this Agreement, notwithstanding notice to the contrary. The Register shall be
available for inspection by the Borrower and any Lender, at any reasonable time
and from time to time upon reasonable prior notice.

        (d)   Any Lender may at any time, without the consent of, or notice to,
the Borrower or the Administrative Agent, sell participations to any Person
(other than a natural person or the Borrower or any of the Borrower's Affiliates
or Subsidiaries) (each, a "Participant") in all or a portion of such Lender's
rights and/or obligations under this Agreement (including all or a portion of
its Commitment and/or the Loans (including such Lender's participation in L/C
Obligations) owing to it); provided that (i) such Lender's obligations under
this Agreement shall remain unchanged, (ii) such Lender shall remain solely
responsible to the other parties hereto for the performance of such obligations
and (iii) the Borrower, the Administrative Agent and the other Lenders shall
continue to deal solely and directly with such Lender in connection with such
Lender's rights and obligations under this Agreement. Any agreement or
instrument pursuant to which a Lender sells such a participation shall provide
that such Lender shall retain the sole right to enforce this Agreement and to
approve any amendment, modification or waiver of any provision of this
Agreement; provided that such agreement or instrument may provide that such
Lender will not, without the consent of the Participant, agree to any amendment,
modification or waiver that would (i) postpone any date upon which any payment
of money is scheduled to be paid to such Participant, (ii) reduce the principal,
interest, fees or other amounts payable to such Participant, or (iii) release
the MLP from its Guaranty. Subject to subsection (e) of this Section, the
Borrower agrees that each Participant shall be entitled to the benefits of
Sections 3.01, 3.04 and 3.05 to the same extent as if it were a Lender and had
acquired its interest by assignment pursuant to subsection (b) of this Section.
To the extent permitted by law, each Participant also shall be entitled to the
benefits of Section 10.09 as though it were a Lender, provided such Participant
agrees to be subject to Section 2.12 as though it were a Lender.

72

--------------------------------------------------------------------------------

        (e)   A Participant shall not be entitled to receive any greater payment
under Section 3.01 or 3.04 than the applicable Lender would have been entitled
to receive with respect to the participation sold to such Participant, unless
the sale of the participation to such Participant is made with the Borrower's
prior written consent. A Participant that would be a Foreign Lender if it were a
Lender shall not be entitled to the benefits of Section 3.01 unless the Borrower
is notified of the participation sold to such Participant and such Participant
agrees, for the benefit of the Borrower, to comply with Section 10.15 as though
it were a Lender.

        (f)    Any Lender may at any time pledge or assign a security interest
in all or any portion of its rights under this Agreement (including under its
Notes, if any) to secure obligations of such Lender, including any pledge or
assignment to secure obligations to a Federal Reserve Bank; provided that no
such pledge or assignment shall release a Lender from any of its obligations
hereunder or substitute any such pledgee or assignee for such Lender as a party
hereto.

        (g)   If the consent of the Borrower to an assignment or to an Eligible
Assignee is required hereunder (including a consent to an assignment which does
not meet the minimum assignment threshold specified in clause (i) of the proviso
to the first sentence of Section 10.07(b)), the Borrower shall be deemed to have
given its consent five Business Days after the date notice thereof has been
delivered by the assigning Lender (through the Administrative Agent) unless such
consent is expressly refused by the Borrower prior to such fifth Business Day.

        (h)   Notwithstanding anything to the contrary contained herein, if at
any time Royal Bank of Canada assigns all of its Commitment and Loans pursuant
to subsection (b) above, Royal Bank of Canada may, (i) upon 30 days' notice to
the Borrower and the Lenders, resign as L/C Issuer. In the event of any such
resignation as L/C Issuer, the Borrower shall be entitled to appoint from among
the Lenders a successor L/C Issuer hereunder; provided, however, that no failure
by the Borrower to appoint any such successor shall affect the resignation of
Royal Bank of Canada as L/C Issuer. Royal Bank of Canada shall retain all the
rights and obligations of the L/C Issuer hereunder with respect to all Letters
of Credit outstanding as of the effective date of its resignation as L/C Issuer
and all L/C Obligations with respect thereto (including the right to require the
Lenders to make Base Rate Loans or fund participations in Unreimbursed Amounts
pursuant to Section 2.14(c)).

        10.08    Confidentiality.    Each Lender agrees that it will not
disclose without the prior consent of the Borrower (other than to directors,
officers, employees, auditors, accountants, counsel or other professional
advisors of the Administrative Agent or any Lender) any information with respect
to the Borrower or its Subsidiaries, which is furnished pursuant to this
Agreement and which (i) the Borrower in good faith considers to be confidential
and (ii) is either clearly marked confidential or is designated by the Borrower
to the Administrative Agent or the Lenders in writing as confidential, provided
that any Lender may disclose any such information (a) as has become generally
available to the public, (b) as may be required or appropriate in any report,
statement or testimony submitted to or required by any municipal, state or
federal regulatory body having or claiming to have jurisdiction over such Lender
or submitted to or required by the Board or the Federal Deposit Insurance
Corporation or similar organizations (whether in the United States of America or
elsewhere) or their successors, (c) as may be required or appropriate in
response to any summons or subpoena in connection with any litigation, (d) in
order to comply with any law, order, regulation or ruling applicable to such
Lender, (e) to any Eligible Assignee of or Participant in, or any prospective
Eligible Assignee of or Participant in, any of its rights or obligations under
this Agreement, provided that such Eligible Assignee or Participant or
prospective Eligible Assignee or Participant executes an agreement containing
provisions substantially similar to those contained in this Section 10.08,
(f) in connection with the exercise of any remedy by such Lender following an
Event of Default pertaining to the Loan Documents, (g) in connection with any
litigation involving such Lender pertaining to the Loan Documents, (h) to any
Lender or the Administrative Agent, or (i) to any Affiliate of any Lender (it
being understood that the

73

--------------------------------------------------------------------------------

Persons to whom such disclosure is made will be informed of the confidential
nature of such information and obligated to keep such information confidential);
provided further, that notwithstanding anything in this Agreement to the
contrary, the Borrower, the Administrative Agent, the Syndication Agent, the L/C
Bank, each Lender and each Related Party may disclose to any and all Persons,
without limitation of any kind, the tax treatment and tax structure of the
transactions contemplated hereby and all materials of any kind (including
opinions or other tax analysis) that are provided to it relating to such tax
treatment and tax structure; and nothing in the foregoing authorization shall
apply to any disclosure that would constitute a violation of applicable federal
or state securities laws.

        10.09    Set-off.    In addition to any rights and remedies of the
Lenders provided by law, upon the occurrence and during the continuance of any
Event of Default, each Lender is authorized at any time and from time to time,
without prior notice to the Borrower or any other Loan Party, any such notice
being waived by the Borrower (on its own behalf and on behalf of each Loan
Party) to the fullest extent permitted by law, to set off and apply any and all
deposits (general or special, time or demand, provisional or final) at any time
held by, and other indebtedness at any time owing by, such Lender to or for the
credit or the account of the respective Loan Parties against any and all
Obligations owing to the Administrative Agent and the Lenders, now or hereafter
existing, irrespective of whether or not the Administrative Agent or such Lender
shall have made demand under this Agreement or any other Loan Document and
although such Obligations may be contingent or unmatured. Each Lender agrees
promptly to notify the Borrower and the Administrative Agent after any such
set-off and application made by such Lender; provided, however, that the failure
to give such notice shall not affect the validity of such set-off and
application.

        10.10    Interest Rate Limitation.    Regardless of any provision
contained in any Loan Document, neither the Administrative Agent nor any Lender
shall ever be entitled to contract for, charge, take, reserve, receive, or
apply, as interest on all or any part of the Obligations, any amount in excess
of the Maximum Rate, and, if any Lender ever does so, then such excess shall be
deemed a partial prepayment of principal and treated hereunder as such and any
remaining excess shall be refunded to the Borrower. In determining if the
interest paid or payable exceeds the Maximum Rate, the Borrower and the Lenders
shall, to the maximum extent permitted under applicable Law, (a) treat all
Borrowings as but a single extension of credit (and the Lenders and the Borrower
agree that such is the case and that provision herein for multiple Borrowings is
for convenience only), (b) characterize any nonprincipal payment as an expense,
fee, or premium rather than as interest, (c) exclude voluntary prepayments and
the effects thereof, and (d) amortize, prorate, allocate, and spread the total
amount of interest throughout the entire contemplated term of the Obligations.
However, if the Obligations are paid and performed in full prior to the end of
the full contemplated term thereof, and if the interest received for the actual
period of existence thereof exceeds the Maximum Amount, the Lenders shall refund
such excess, and, in such event, the Lenders shall not, to the extent permitted
by Law, be subject to any penalties provided by any Laws for contracting for,
charging, taking, reserving or receiving interest in excess of the Maximum
Amount. To the extent the Laws of the State of Texas are applicable for purposes
of determining the "Maximum Rate" or the "Maximum Amount," then those terms mean
the "weekly ceiling" from time to time in effect under Texas Finance Code §
303.001, as limited by Texas Finance Code § 303.009. The Borrower agrees that
Chapter 346 of the Texas Finance Code, as amended (which regulates certain
revolving credit loan accounts and revolving tri-party accounts), does not apply
to the Obligations.

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

        10.12    Integration.    This Agreement, together with the other Loan
Documents, comprises the complete and integrated agreement of the parties on the
subject matter hereof and thereof and supersedes all prior agreements, written
or oral, on such subject matter. In the event of any conflict

74

--------------------------------------------------------------------------------

between the provisions of this Agreement and those of any other Loan Document,
the provisions of this Agreement shall control; provided that the inclusion of
supplemental rights or remedies in favor of the Administrative Agent or the
Lenders in any other Loan Document shall not be deemed a conflict with this
Agreement. Each Loan Document was drafted with the joint participation of the
respective parties thereto and shall be construed neither against nor in favor
of any party, but rather in accordance with the fair meaning thereof.

        10.13    Survival of Representations and Warranties.    All
representations and warranties made hereunder and in any other Loan Document or
other document delivered pursuant hereto or thereto or in connection herewith or
therewith shall survive the execution and delivery hereof and thereof. Such
representations and warranties have been or will be relied upon by the
Administrative Agent and each Lender, regardless of any investigation made by
the Administrative Agent or any Lender or on their behalf and notwithstanding
that the Administrative Agent or any Lender may have had notice or knowledge of
any Default or Event of Default at the time of any Borrowing, and shall continue
in full force and effect as long as any Loan or any other Obligation shall
remain unpaid or unsatisfied.

        10.14    Severability.    Any provision of this Agreement and the other
Loan Documents to which the Borrower is a party that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions thereof, and any such prohibition or unenforceability in
any jurisdiction shall not invalidate or render unenforceable such provision in
any other jurisdiction.

        10.15    Foreign Lenders.    Each Lender that is a "foreign corporation,
partnership or trust" within the meaning of the Code (a "Foreign Lender") shall
deliver to the Administrative Agent, prior to receipt of any payment subject to
withholding under the Code (or after accepting an assignment of an interest
herein), two duly signed completed copies of either IRS Form W-8BEN or any
successor thereto (relating to such Person and entitling it to an exemption
from, or reduction of, withholding tax on all payments to be made to such Person
by the Borrower pursuant to this Agreement) or IRS Form W-8ECI or any successor
thereto (relating to all payments to be made to such Person by the Borrower
pursuant to this Agreement) or such other evidence satisfactory to the Borrower
and the Administrative Agent that such Person is entitled to an exemption from,
or reduction of, U.S. withholding tax. Thereafter and from time to time, each
such Person shall (a) promptly submit to the Administrative Agent such
additional duly completed and signed copies of one of such forms (or such
successor forms as shall be adopted from time to time by the relevant United
States taxing authorities) as may then be available under then current United
States laws and regulations to avoid, or such evidence as is satisfactory to the
Borrower and the Administrative Agent of any available exemption from or
reduction of, United States withholding taxes in respect of all payments to be
made to such Person by the Borrower pursuant to this Agreement, (b) promptly
notify the Administrative Agent of any change in circumstances which would
modify or render invalid any claimed exemption or reduction, and (c) take such
steps as shall not be materially disadvantageous to it, in the reasonable
judgment of such Lender, and as may be reasonably necessary (including the
re-designation of its Lending Office) to avoid any requirement of applicable
Laws that the Borrower make any deduction or withholding for taxes from amounts
payable to such Person. If such Person fails to deliver the above forms or other
documentation, then the Administrative Agent may withhold from any interest
payment to such Person an amount equivalent to the applicable withholding tax
imposed by Sections 1441 and 1442 of the Code, without reduction. If any
Governmental Authority asserts that the Administrative Agent did not properly
withhold any tax or other amount from payments made in respect of such Person,
such Person shall indemnify the Administrative Agent therefor, including all
penalties and interest, any taxes imposed by any jurisdiction on the amounts
payable to the Agent under this Section, and costs and expenses (including
Attorney Costs) of the Administrative Agent. The obligation of the Lenders under
this Section shall survive the payment of all Obligations and the resignation or
replacement of the Administrative Agent.

75

--------------------------------------------------------------------------------

        10.16    Governing Law.    

        (a)   THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE
WITH, THE LAW OF THE STATE OF TEXAS APPLICABLE TO AGREEMENTS MADE AND TO BE
PERFORMED ENTIRELY WITHIN SUCH STATE; PROVIDED THAT THE ADMINISTRATIVE AGENT AND
EACH LENDER SHALL RETAIN ALL RIGHTS ARISING UNDER UNITED STATES FEDERAL LAW.

        (b)   EACH COMPANY AND OTHER PARTY HERETO, AND EACH GUARANTOR, BY
EXECUTION OF A GUARANTY, AGREES AS TO THIS SECTION 10.16(b). ANY LEGAL ACTION OR
PROCEEDING WITH RESPECT TO THIS AGREEMENT OR ANY OTHER LOAN DOCUMENT MAY BE
BROUGHT IN THE COURTS OF THE STATE OF TEXAS SITTING IN HARRIS COUNTY OR OF THE
UNITED STATES FOR THE SOUTHERN DISTRICT OF SUCH STATE, AND BY EXECUTION AND
DELIVERY OF THIS AGREEMENT, THE BORROWER, THE ADMINISTRATIVE AGENT AND EACH
LENDER CONSENTS, AND BY EXECUTION OF A GUARANTY, EACH GUARANTOR CONSENTS, FOR
ITSELF AND IN RESPECT OF ITS PROPERTY, TO THE NON-EXCLUSIVE JURISDICTION OF
THOSE COURTS. THE BORROWER, EACH GUARANTOR, THE ADMINISTRATIVE AGENT AND EACH
LENDER (1) IRREVOCABLY WAIVES ANY OBJECTION, INCLUDING ANY OBJECTION TO THE
LAYING OF VENUE OR BASED ON THE GROUNDS OF FORUM NON CONVENIENS, WHICH IT MAY
NOW OR HEREAFTER HAVE TO THE BRINGING OF ANY ACTION OR PROCEEDING IN SUCH
JURISDICTION IN RESPECT OF ANY LOAN DOCUMENT OR OTHER DOCUMENT RELATED THERETO,
AND (2) IRREVOCABLY CONSENTS TO THE SERVICE OF PROCESS OUT OF ANY OF THE
AFOREMENTIONED COURTS IN ANY SUCH ACTION OR PROCEEDING BY THE MAILING OF COPIES
THEREOF BY CERTIFIED MAIL, RETURN RECEIPT REQUESTED, POSTAGE PREPAID, AT ITS
ADDRESS FOR NOTICES DESIGNATED HEREIN. THE BORROWER, EACH GUARANTOR, THE
ADMINISTRATIVE AGENT AND EACH LENDER WAIVES PERSONAL SERVICE OF ANY SUMMONS,
COMPLAINT OR OTHER PROCESS, WHICH MAY BE MADE BY ANY OTHER MEANS PERMITTED BY
THE LAW OF SUCH STATE. THE BORROWER AND EACH GUARANTOR, BY ITS EXECUTION OF A
GUARANTY, HEREBY IRREVOCABLY APPOINTS CT CORPORATION SYSTEM, WITH AN ADDRESS AT
350 N. ST. PAUL STREET, DALLAS, TEXAS 75201 (THE "TEXAS PROCESS AGENT") AS
PROCESS AGENT IN ITS NAME, PLACE AND STEAD TO RECEIVE AND FORWARD SERVICE OF ANY
AND ALL WRITS, SUMMONSES AND OTHER LEGAL PROCESS IN ANY SUIT, ACTION OR
PROCEEDING BROUGHT IN THE STATE OF TEXAS, AGREES THAT SUCH SERVICE IN ANY SUCH
SUIT, ACTION OR PROCEEDING MAY BE MADE UPON THE TEXAS PROCESS AGENT, AND AGREES
TO TAKE ALL SUCH ACTION AS MAY BE NECESSARY TO CONTINUE SAID APPOINTMENT IN FULL
FORCE AND EFFECT.

        10.17    Waiver of Right to Trial by Jury, Etc.    EACH PARTY TO THIS
AGREEMENT AND EACH GUARANTOR, BY EXECUTION OF A GUARANTY, HEREBY (a) EXPRESSLY
AND IRREVOCABLY WAIVES ANY RIGHT TO TRIAL BY JURY OF ANY CLAIM, DEMAND, ACTION
OR CAUSE OF ACTION ARISING UNDER ANY LOAN DOCUMENT OR IN ANY WAY CONNECTED WITH
OR RELATED OR INCIDENTAL TO THE DEALINGS OF THE PARTIES TO THE LOAN DOCUMENTS OR
ANY OF THEM WITH RESPECT TO ANY LOAN DOCUMENT, OR THE TRANSACTIONS RELATED
THERETO, IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER ARISING, AND WHETHER
FOUNDED IN CONTRACT OR TORT OR OTHERWISE; AND EACH PARTY HEREBY AGREES AND
CONSENTS THAT ANY SUCH CLAIM, DEMAND, ACTION OR CAUSE OF ACTION SHALL BE DECIDED
BY COURT TRIAL WITHOUT A JURY, AND THAT ANY PARTY TO THIS AGREEMENT MAY FILE AN

76

--------------------------------------------------------------------------------

ORIGINAL COUNTERPART OR A COPY OF THIS SECTION WITH ANY COURT AS WRITTEN
EVIDENCE OF THE CONSENT OF THE COMPANIES TO THE WAIVER OF THEIR RIGHT TO TRIAL
BY JURY; AND (b) EXPRESSLY AND IRREVOCABLY WAIVES, TO THE MAXIMUM EXTENT NOT
PROHIBITED BY LAW, ANY RIGHT IT MAY HAVE TO CLAIM OR RECOVER IN ANY SUCH ACTION
ANY SPECIAL, EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES, OR DAMAGES OTHER
THAN, OR IN ADDITION TO, ACTUAL DAMAGES, PROVIDED THAT THE WAIVER CONTAINED IN
THIS SECTION 10.17(b) SHALL NOT APPLY TO THE EXTENT THAT THE PARTY AGAINST WHOM
DAMAGES ARE SOUGHT HAS ENGAGED IN GROSS NEGLIGENCE OR WILLFUL MISCONDUCT.

        10.18    Security Interest In Parent Pledge Agreement.    The Borrower
hereby grants to the Administrative Agent, for the benefit of the Lenders, a
lien on and security interest in and to the Borrower's rights, titles and
interest in and to the Parent Pledge Agreement and in the Cash (as therein
defined), the Demand Account (as therein defined) and the Collateral (as therein
defined) as security for the Obligations. The rights granted by this
Section 10.18 shall be in addition to the rights of any Agent under any
statutory banker's Lien or the common law right of setoff.

        10.19    No General Partner's Liability.    The Administrative Agent and
the Lenders agree for themselves and their respective successors and assigns,
including any subsequent holder of any Note, that no claim under this Agreement,
under the Guaranty executed on behalf of the MLP, or under any other Loan
Document shall be made against the General Partner, and that no judgment, order
or execution entered in any suit, action or proceeding, whether legal or
equitable, hereunder, on such Guaranty, or on any other Loan Document shall be
obtained or enforced, against the General Partner or its assets for the purpose
of obtaining satisfaction and payment of amounts owed under this Agreement, such
Guaranty or any other Loan Document. Nothing in this Section 10.19, however,
shall be construed so as to prevent the Administrative Agent, any Lender or any
other holder of any Note from commencing any action, suit or proceeding with
respect to or causing legal papers to be served upon the General Partner for the
sole purpose of obtaining jurisdiction over the MLP.

        10.20    Termination of Commitments Under Original Credit
Agreement.    As of the Restatement Date the Commitments under the Original
Credit Agreement are terminated and the Administrative Agent and the Lenders
hereby waive any right to receive prior notice of such termination. Each Lender
agrees upon the Restatement Date to return to Borrower with reasonable
promptness all "Notes" as defined under the Original Credit Agreement which were
delivered by the Borrower in exchange for new Notes to be issued pursuant to
this Agreement.

        10.21    No Novations, Etc.    To the extent of the aggregate commitment
outstanding under the Original Credit Agreement ($75,000,000) nothing contained
herein shall be deemed a novation of or a repayment or new advance of any
obligation of the Borrower hereunder. Only to the extent of an increase in the
Aggregate Commitment over that amount shall there be deemed to be a new advance
by the Lenders to the Borrower under this Agreement. The Indebtedness owing
under the Original Credit Agreement is renewed, rearranged, extended and carried
forward by this Agreement and all of the liens and security interests securing
the "Obligations" as defined in the Original Credit Agreement are carried
forward and secure, without interruption or loss or priority, the Obligations
under this Agreement.

        10.22    ENTIRE AGREEMENT.    THIS AGREEMENT AND THE OTHER LOAN
DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.

[REMAINDER OF PAGE INTENTIONALLY BLANK;
SIGNATURES BEGIN ON NEXT PAGE]

77

--------------------------------------------------------------------------------

        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the date first above written.

    MARKWEST ENERGY OPERATING COMPANY, L.L.C.,
a Delaware limited liability company, as Borrower
 
 
By:
MarkWest Energy Partners, L.P.
its Managing Member
 
 
By:
MarkWest Energy GP, L.L.C.,
Its General Partner
 
 
By:
/s/  ANDREW L. SCHROEDER      

--------------------------------------------------------------------------------

Andrew L. Schroeder
Vice President and Treasurer
 
 
MARKWEST ENERGY PARTNERS, L.P.,
a Delaware limited partnership, as a Guarantor
 
 
By:
MarkWest Energy GP, L.L.C.,
its General Partner
 
 
By:
/s/  ANDREW L. SCHROEDER      

--------------------------------------------------------------------------------

Andrew L. Schroeder
Vice President and Treasurer
 
 
ROYAL BANK OF CANADA,
as Administrative Agent
 
 
By:
/s/  GAIL WATKIN      

--------------------------------------------------------------------------------

Gail Watkin
Manager, Agency
 
 
ROYAL BANK OF CANADA, as Lender
and L/C Issuer
 
 
By:
/s/  LORNE GARTNER      

--------------------------------------------------------------------------------

Lorne Gartner
Authorized Signatory
 
 
BANK ONE, NA,
(Main Office Chicago)
as Syndication Agent
 
 
By:
/s/  JANET BEADLE      

--------------------------------------------------------------------------------

Janet Beadle
Director
 
 
BANK ONE, NA,
(Main Office Chicago)
as Lender
 
 
By:
/s/  JOSEPH C. GIAMPETRONI      

--------------------------------------------------------------------------------

Joseph C. Giampetroni
Director        

--------------------------------------------------------------------------------

 
 
FORTIS CAPITAL CORP.
as Documentation Agent and as Lender
 
 
By:
/s/  DARRELL W. HOLLEY      

--------------------------------------------------------------------------------

Darrell W. Holley
Managing Director
 
 
By:
/s/  CASEY LOWARY      

--------------------------------------------------------------------------------

Casey Lowary
Senior Vice President

--------------------------------------------------------------------------------

QuickLinks

EXHIBIT 10.1

TABLE OF CONTENTS
AMENDED AND RESTATED CREDIT AGREEMENT
PRELIMINARY STATEMENTS
ARTICLE I. DEFINITIONS AND ACCOUNTING TERMS
ARTICLE II. THE COMMITMENTS AND BORROWINGS
ARTICLE III. TAXES, YIELD PROTECTION AND ILLEGALITY
ARTICLE IV. CONDITIONS PRECEDENT TO BORROWINGS
ARTICLE V. REPRESENTATIONS AND WARRANTIES
ARTICLE VI. AFFIRMATIVE COVENANTS
ARTICLE VII. NEGATIVE COVENANTS
ARTICLE VIII. EVENTS OF DEFAULT AND REMEDIES
ARTICLE IX. ADMINISTRATIVE AGENT
ARTICLE X. MISCELLANEOUS