<Page>

                                                                    Exhibit 10.6

                 FRACTIONATION, STORAGE AND LOADING AGREEMENT
                                   (Siloam)

     This Fractionation, Storage and Loading Agreement ("Agreement") is made
and entered into this ____ day of ______, 2002, by and between MARKWEST
ENERGY APPALACHIA, L.L.C., a Delaware limited partnership ("MEA"), and
MARKWEST HYDROCARBON, INC.,  a Delaware corporation ("MarkWest"). MEA and
MarkWest may be referred to individually as "Party", or collectively as
"Parties".

     Section 1.     SCOPE OF AGREEMENT AND GENERAL TERMS AND CONDITIONS.
MarkWest agrees to deliver, or cause to be delivered, Raw Make, as defined
below, to MEA, and MEA agrees to receive and fractionate that Raw Make into
Plant Products, as defined below, and to store, load and deliver Plant
Products to MarkWest, all in accordance with this Agreement. This Agreement
does not apply to Raw Make and Plant Products covered by that certain Natural
Gas Liquids Transportation And Fractionation Agreement (Maytown), between
MarkWest and MEA, of even date herewith. This Agreement incorporates and is
subject to all of the General Terms and Conditions attached hereto, together
with any other Exhibits attached hereto.

     Section 2.     EFFECTIVE DATE. The date on which the obligations and
duties of the Parties shall commence, being the "Effective Date", shall be
_______________, 2002.

     Section 3.     TERM. This Agreement shall remain in full force and
effect from the Effective Date through December 31, 2015 (the "Primary
Term"), and shall continue thereafter on a year-to-year basis until
terminated by either Party by providing at least 60 days written notice to
the other Party in advance of the termination of the Primary Term or of any
one-year extension thereof.

     Section 4.     FEES AND CONSIDERATION.

     A.  As full consideration for the services provided by MEA, MarkWest
     shall pay the following fees and MEA shall make the following deliveries:

          i.     For the fractionation of Raw Make into Plant Products, by
          MEA, at Siloam, MarkWest shall pay MEA a Fractionation Fee equal to
          the gallons of Raw Make fractionated multiplied by $*. The
          Fractionation Fee covers, and is inclusive of the MEA's costs for
          fractionating Raw Make, loading Plant Products and above ground
          storage of Plant Products.

          ii.    For the exclusive use of the Cavern for the underground
          storage of MarkWest's Plant Products, MarkWest shall pay MEA an
          Annual Storage Fee equal to $*.

          iii.   Should MarkWest deliver any Raw Make to Siloam by railcar,
          MEA shall unload the Raw Make for fractionation and MarkWest shall
          pay MEA an Unloading Fee of $* per gallon of Raw Make unloaded from
          railcars.

          iv.    A portion of each of the Fractionation Fee, Annual Storage
          Fee and Unloading Fee (collectively, the "Fees") shall be subject to
          annual adjustments.

1

                  *Denotes Confidential Portion Omitted and
                     Filed Separately with the Commission

<Page>

          *% of each of the Fees, shall be adjusted on an annual basis in
          proportion to the percentage change, from the preceding year, in
          the Producer Price Index for oil and gas field services (SIC 138)
          as published by the Department of Labor ("PPI"). The adjustment of
          the Fees shall be made effective January 1 of each year, and shall
          reflect the percentage change in the PPI as it existed for the
          immediately preceding January from the PPI for the second
          immediately preceding January.

          v.     MEA shall deliver and load the Plant Products fractionated
          from MarkWest's Raw Make to the Product Delivery Points in
          accordance with the terms of this Agreement.

     Section 5.     NOTICES. All notices, statements, invoices or other
communications required or permitted between the Parties shall be in writing
and shall be considered as having been given if delivered by mail, courier,
hand delivery, or facsimile to the other Party at the designated address or
facsimile numbers. Normal operating instructions can be delivered by
telephone or other agreed means. Notice of events of Force Majeure may be
made by telephone and confirmed in writing within a reasonable time after the
telephonic notice. Monthly statements, invoices, payments and other
communications shall be deemed delivered when actually received. Either Party
may change its address or facsimile and telephone numbers upon written notice
to the other Party:

     MarkWest:

          Address:       155 Inverness Drive West, Suite 200
                         Englewood, Colorado 80112
                         Attn: Contract Administration
                         Fax: (303)


     MEA:

          Address:       155 Inverness Drive West, Suite 200
                         Englewood, Colorado 80112
                         Attn: Contract Administration
                         Fax: (303)

     Section 6.     EXECUTION. This Agreement may be executed in any number
of counterparts, each of which shall be considered and original, and all of
which shall be considered one instrument.

IN WITNESS WHEREOF, the Parties have executed this Agreement on the date
first set forth above.


                                        MARKWEST HYDROCARBON, INC.


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


2

                  *Denotes Confidential Portion Omitted and
                     Filed Separately with the Commission

<Page>



                                        MARKWEST ENERGY APPALACHIA, L.L.C.


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















3

<Page>

                         GENERAL TERMS AND CONDITIONS
                 ATTACHED TO AND MADE A PART OF THAT CERTAIN
                 FRACTIONATION, STORAGE AND LOADING AGREEMENT
                                   BETWEEN
                  MARKWEST HYDROCARBON, INC., AS "MARKWEST"
                                     AND
                 MARKWEST ENERGY APPALACHIA, L.L.C., AS "MEA"
                                    DATED:



ARTICLE 1:     DEFINITIONS



ACCOUNTING PERIOD.     The period commencing at 8:00 a.m., Eastern Time, on
the first day of a calendar month and ending at 8:00 a.m., Eastern Time, on
the first day of the next succeeding month.

CAVERN.     The two underground Plant Products storage cavern owned and
operated by MEA at Siloam with a capacity of approximately 11,000,000 gallons.

FORCE MAJEURE.     Any cause or condition not within the reasonable control
of the Party claiming suspension and which by the exercise of reasonable
diligence, such Party is unable to prevent or overcome.

FRACTIONATION FUEL.     All Gas, Plant Products, vapors or other forms of
energy utilized as fuel in Siloam.

GAS.     All hydrocarbon and non-hydrocarbon substances in a gaseous state.

INCIDENTAL LOSSES OR GAINS.     The incidental losses incurred in MEA's
facilities, or the losses or gains incurred due to variations in measurement
equipment.

INDEMNIFYING PARTY AND INDEMNIFIED PARTY.     As defined in Article 8, below.

LOSSES.     Any actual loss, cost, expense, liability, damage, demand, suit,
sanction, claim,  judgment, lien, fine or penalty which are incurred by the
applicable Indemnified Party on account of injuries (including death) to any
person or damage to or destruction of any property, sustained or alleged to
have been sustained in connection with or arising out of the matters for
which the Indemnifying Party has indemnified the applicable Indemnified Party.

MEA PLANTS.     Gas processing and extraction plants, owned and/or operated
by MEA.

PLANT PRODUCTS.     The finished liquid products fractionated from the Raw
Make delivered hereunder, including propane, isobutane, normal butane and
natural gasoline.

PLANT PRODUCTS DELIVERY POINT.     The point at which the Plant Products are
delivered to, or for the account of, MarkWest into transportation facilities
furnished by MarkWest.

RAW MAKE.     A combined stream of propane and heavier liquefied
hydrocarbons, including incidental ethane.

RECEIPT POINT.     For Raw Make, the inlet flange of the pipeline at the
point at which MarkWest delivers Raw Make into the pipeline, and for Raw Make
delivered by truck trailer or by tank car, the inlet flange of the Raw Make
unloading facilities of MEA at or near Siloam.

SILOAM.     MEA's Siloam fractionation facility located near South Shore,
Kentucky, including any treating equipment, Plant Products separation and
fractionation vessels, all above ground Plant Products storage vessels and
all below ground Plant Products and Raw Make storage caverns and

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facilities, and associated condensing, heating, pumping, conveying, and other
equipment and instrumentation; including all structures associated with those
facilities; and, all Plant Products loading facilities, including railcar
loading, truck loading and barge loading facilities and including all
easements, rights-of-way, and other property rights pertaining to the
construction and operation of those facilities; wherever those facilities,
structures, easements, rights-of-way, and other property rights are located.

ARTICLE 2:     MARKWEST COMMITMENTS

2.1.     MarkWest hereby commits and agrees to deliver at the Receipt Points
all of MarkWest's Raw Make acquired from the MEA Plants, or from other
extraction plants in the Appalachian region.

ARTICLE 3:     OPERATION OF MEA'S FACILITIES

3.1.     Subject to the other provisions of this Agreement, MEA agrees to
accept all of MarkWest's Raw Make, fractionate the Raw Make into Plant
Products in accordance with this Agreement and to store and load Plant
Products for MarkWest as provided herein.

3.3.     MEA agrees that it shall, at its sole cost, risk, and expense,
furnish all Fractionation Fuel for operating Siloam, and in no event shall
any of MarkWest's Raw Make delivered hereunder or Plant Products or any
vapors therefrom be consumed or utilized by MEA as Fractionation Fuel or in
any other manner prior to delivery of Plant Products to MarkWest as herein
provided.

3.4.     MEA agrees that it shall, at its sole cost, risk, and expense,
operate, maintain, and replace (if necessary) docks, loading racks,
pipelines, and all other facilities for loading each Product for shipment by
highway, rail, and marine transportation from the vicinity of Siloam. MEA
agrees that all facilities operated by MEA which are required in the
performance of the services herein agreed upon shall, at its sole cost, risk,
and expense, be maintained and operated at all times as a prudent operator
would maintain and operate similar facilities. MEA hereby agrees to lease and
let MarkWest, at no additional consideration, trackage rights on MEA's Siloam
railroad siding to move Product hereunder.

3.5.     MEA agrees that it shall, at its sole cost, risk, and expense, be
responsible for all loading of each Product for shipments in accordance with
reasonable authorizations and instructions given from time to time by
MarkWest, including, but not limited to, preparation and distribution of all
shipping papers pertaining to movement of Plant Products from Siloam, rail,
truck and barge bills of lading, loading tickets, and reports and odorization
certifications. MEA shall furnish all trained employees required to perform
these services and shall maintain complete records of all Product
dispositions.

3.6.     MEA agrees that it shall, at its sole risk, be responsible for
placing Plant Products into storage in the Cavern and withdrawing Plant
Products from the Cavern in accordance with reasonable authorizations and
instructions given from time to time by MarkWest.

3.7.     All Incidental Losses and Gains incurred at Siloam shall be for the
benefit or detriment, as applicable, of MarkWest.

ARTICLE 4:     QUALITY

4.1.     RAW MAKE QUALITY.

A.     The Raw Make fractionated under this Agreement is derived from MEA
Plants, and from other plants. As long as the Raw Make delivered hereunder
for fractionation is of a quality which, when fractionated, meets the
applicable specifications set forth on Exhibit A, attached hereto, then MEA
agrees to receive and fractionate that Raw Make into Plant Products meeting
the specifications set forth herein.

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<Page>

B.      Should any of the Raw Make fail to meet the above specifications, then:

        i.     MEA may take receipt of the non-conforming Raw Make, and that
        receipt shall not be construed as a waiver or change of standards for
        future Raw Make deliveries; or

        ii.    MEA may, at its sole discretion, cease receiving the
        non-conforming Raw Make, and shall notify MarkWest that it has, or
        will, cease receiving the non-conforming Raw Make.

4.2     PLANT PRODUCTS QUALITY. MEA shall fractionate all Raw Make meeting
the requirements under Section 4.1, to produce Plant Products meeting the
specifications set forth on Exhibit A, attached hereto.

ARTICLE 5:     MEASUREMENT EQUIPMENT AND PROCEDURES AND ANALYSES

5.1.    RAW MAKE.     Raw Make shall be measured at the respective Receipt
Point(s) and shall conform to applicable API and GPA standards for pipeline,
truck, and rail car measurement as follows:

        (1)    For Raw Make delivered by pipeline:

        A.     MEA shall measure the weight of the Raw Make delivered
        hereunder using either turbine or coriolis mass flow meters installed,
        operated and maintained in accordance with GPA Standard 8182-latest
        edition and/or API Manual of Petroleum Measurement Standards Draft
        Standard, Measurement of Single-Phase, Intermediate and Finished
        Hydrocarbon Fluids by Coriolis Meters-latest edition.

        B.     MEA shall measure the composition of the Raw Make delivered
        hereunder using a chromatograph installed, operated and maintained in
        accordance with GPA Standard 2165-latest edition, GPA Standard
        2145-latest edition, GPA Standard 2261-latest edition, GPA Standard
        2177-latest edition and the manufacturer's specifications and
        standards. Factors for hexanes and heavier shall be in accordance with
        Table IV of GPA Standard 2261-latest edition or determined by periodic
        samples taken by the MEA. Samples shall be taken at intervals not to
        exceed 20 minutes. The arithmetic average of the samples during a day
        shall be deemed to be the Raw Make Composition for such day.

        C.     The weight of each Raw Make component shall be converted to
        gallons at 60DEG.F in accordance with GPA Standard 8173-latest edition
        and GPA Standard 2145-latest edition.

        (2)    The trucks shall be weighed empty and full. GPA Standard 8186,
as revised, is the standard to be used on all truck deliveries.

        (3)    Rail cars shall be measured using strapping tables and liquid
spew gauges. Vapor correction calculations will be made as required by
applicable industry standards.

5.2     PLANT PRODUCTS MEASUREMENT.

Measurement of all Plant Products and deliveries shall be converted to 60oF
and shall conform to applicable API and GPA standards for barge, truck, and
rail car measurement:

        (1)    Barge loading will be by strapping tables. Vapor correction
will be included on delivery tickets on all Plant Products except gasoline.

        (2)    The trucks shall be weighed empty and full. GPA Standard 8186,
as

6

<Page>

revised, is the standard to be used on all truck deliveries.

        (3)    Rail cars shall be measured using strapping tables and liquid
spew gauges. Vapor correction calculations will be made as required by
applicable industry standards.

5.3     INVENTORY.

A.     MEA will maintain and provide MarkWest with daily reports setting
forth the volumes of MarkWest's Raw Make and Plant Products held in inventory
at Siloam.

B.     MEA shall measure the inventory of each above ground storage tank
using tank guages and shall measure the inventory in the Cavern using inlet
and outlet meters and guages. Such meters and guages shall be installed,
operated and maintained in accordance with applicable industry standards.

5.4    ANALYSES.

A.     MEA shall, at its sole cost, risk, and expense, install, operate, and
maintain equipment to analyze the composition of the Raw Make and of the
Plant Products in accordance with applicable GPA standards.

B.     With respect to Raw Make delivered by tank and truck cars, and with
respect to Plant Products, samples shall be analyzed in accordance with
applicable GPA standards. The analysis shall also include the determination
of the molecular weight, density, and heating value of the hexane and heavier
fraction be extended analysis, quarterly in accordance with industry
recognized standards. MarkWest or MEA or their representatives may take
samples for verification of composition and may be present during any of the
other party's sampling operations.

ARTICLE 6:     PAYMENTS

6.1.   MEA shall provide MarkWest with a statement explaining fully how all
consideration due under the terms of this Agreement was determined not later
than the 15th day of the Accounting Period following the Accounting Period
for which the consideration is due.

6.2.   Any sums due MEA under this Agreement shall be paid no later than the
last day of the Accounting Period in which the statement provided under
Section 6.1 was received.

6.3.   Either Party, on 10 days prior written notice, shall have the right at
its expense, at reasonable times during business hours, to audit the books
and records of the other Party to the extent necessary to verify the accuracy
of any statement, measurement, computation, charge, or payment made under or
pursuant to this Agreement. A Party electing to audit ("Auditing Party")
shall complete its audit within 3 months following the date on which the
books and records of the other Party ("Audited Party") are first made
available for inspection following the Auditing Party's notice of audit.
Within that 3-month period, the Auditing Party shall submit, in writing, all
exceptions disclosed by the audit to the Audited Party. The Audited Party
shall have 30 days following receipt of the exceptions in which to respond in
writing to the exceptions. If the Audited Party fails to respond within that
30-day period, the exceptions shall be deemed accepted and appropriate
adjustments and settlements shall be made and, as applicable, paid. If the
Parties are unable to reach agreement as to any exceptions to which the
Audited Party timely responded within 30 days of the Audited Party's
response, then either Party may submit the matter to arbitration in
accordance with the provisions in Article 9.

ARTICLE 7:     FORCE MAJEURE

7.1.   In the event a Party is rendered unable, wholly or in part, by Force
Majeure, to carry out its obligations under this Agreement,

7

<Page>

other than the obligation to make any payments due hereunder, the obligations
of that Party, so far as they are affected by Force Majeure, shall be
suspended from the inception and during the continuance of the inability, and
the cause of the Force Majeure, as far as possible, shall be remedied with
commercially reasonable diligence. The Party affected by Force Majeure shall
provide the other Party with written notice of the Force Majeure event, with
reasonably full detail of the Force Majeure within a reasonable time after
the affected Party learns of the occurrence of the Force Majeure event. The
settlement of strikes, lockouts, and other labor difficulty shall be entirely
within the discretion of the Party having the difficulty and nothing herein
shall require the settlement of strikes, lockouts, or other labor difficulty.

ARTICLE 8:     LIABILITY AND INDEMNIFICATION

8.1.   As among the Parties hereto, MarkWest and any of its designees shall
be in custody, control and possession of the Raw Make hereunder, until the
Raw Make is delivered to MEA at the Receipt Point, and shall be in custody
control and possession of the Plant Products after the Plant Products are
loaded by MEA into transportation facilities provided by MarkWest.

8.2.   As among the Parties hereto, MEA and any of its designees shall be in
custody, control and possession of the Raw Make hereunder after Raw Make is
delivered at the Receipt Point and shall be in custody, control and
possession of the Plant Products until the Plant Products are loaded by MEA
into transportation facilities provided by MarkWest.

8.3.   Each Party ("Indemnifying Party") hereby covenants and agrees with the
other Party, and its affiliates (except for the Indemnifying Party itself),
and each of their directors, officers and employees ("Indemnified Parties"),
that except to the extent caused by the Indemnified Parties' gross negligence
or willful conduct, the Indemnifying Party shall protect, defend, indemnify
and hold harmless the Indemnified Parties from, against and in respect of any
and all Losses incurred by the Indemnified Parties to the extent those Losses
arise from or are related to:  (a)  the Indemnifying Party's facilities; or
(b) the Indemnifying Party's possession and control of the Raw Make or Plant
Products, as applicable.

ARTICLE 9:     MISCELLANEOUS

9.1.   The failure of any Party hereto to exercise any right granted
hereunder shall not impair nor be deemed a waiver of that Party's privilege
of exercising that right at any subsequent time or times.

9.2.   This Agreement shall be governed by, construed, and enforced in
accordance with the laws of the State of Colorado without regard to choice of
law principles.

9.3.   This Agreement shall extend to and inure to the benefit of and be
binding upon the Parties, and their respective successors and assigns,
including any assigns of MarkWest's Interests covered by this Agreement. No
assignment of this Agreement shall be binding on either of the Parties until
the first day of the Accounting Period following the date a certified copy of
the instrument evidencing that sale, transfer, assignment or conveyance has
been delivered to the other Party. Further, each assigning Party shall notify
its assignee of the existence of this Agreement and obtain a ratification of
this Agreement prior to such assignment. No assignment by either Party shall
relieve that Party of its continuing obligations and duties hereunder without
the express consent of the other Party.

9.4.   Any change, modification or alteration of this Agreement shall be in
writing, signed by the Parties; and, no course of dealing between the Parties
shall be construed to alter the terms of this Agreement.

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9.5    This Agreement, including all exhibits and appendices, contains the
entire agreement between the Parties with respect to the subject matter
hereof, and there are no oral or other promises, agreements, warranties,
obligations, assurances, or conditions precedent, affecting it.

9.6    NO BREACH OF THIS AGREEMENT OR CLAIM FOR LOSSES UNDER ANY INDEMNITY
OBLIGATION CONTAINED IN THIS AGREEMENT SHALL CAUSE ANY PARTY TO BE LIABLE
FOR, NOR SHALL LOSSES INCLUDE, ANY DAMAGES OTHER THAN ACTUAL AND DIRECT
DAMAGES, AND EACH PARTY EXPRESSLY WAIVES ANY RIGHT TO CLAIM ANY OTHER
DAMAGES, INCLUDING, WITHOUT LIMITATION, CONSEQUENTIAL, SPECIAL, INDIRECT,
PUNITIVE OR EXEMPLARY DAMAGES.

9.7    DISPUTE RESOLUTION. Any dispute arising under this Agreement
("Arbitrable Dispute") shall be referred to and resolved by binding
arbitration in Denver, Colorado, by three (3) arbitrators, in accordance with
the rules and procedures of the Judicial Arbiter Group ("JAG"); and, to the
maximum extent applicable, the Federal Arbitration Act (Title 9 of the United
States Code). If there is any inconsistency between this Section and any
statute or rules, this Section shall control. Arbitration shall be initiated
within the applicable time limits set forth in this Agreement and not
thereafter or if no time limit is given, within the time period allowed by
the applicable statute of limitations, by one party ("Claimant") giving
written notice to the other party ("Respondent") and to JAG, that the
Claimant elects to refer the Arbitrable Dispute to arbitration, and that the
Claimant has appointed an arbitrator, who shall be identified in such notice.
The Respondent shall notify the Claimant and JAG within thirty (30) Days
after receipt of Claimant's notice, identifying the arbitrator the Respondent
has appointed. The two (2) arbitrators so chosen shall select a third
arbitrator within thirty (30) Days after the second arbitrator has been
appointed (upon failure of a party to act within the time specified for
naming an arbitrator, such arbitrator shall be appointed by the
administrator's designee). MarkWest shall pay the compensation and expenses
of the arbitrator named by or for it, MEA shall pay the compensation and
expenses of the arbitrator named by or for it, and MarkWest and MEA shall
each pay one-half of the compensation and expenses of the third arbitrator.
All arbitrators must be neutral parties who have never been officers,
directors, employees, contractors or agents of the parties or any of their
Affiliates, must have not less than ten (10) years experience in the oil and
gas industry, and must have a formal financial/accounting, engineering or
legal education. The parties shall have all rights of discovery in accordance
with the Federal Rules of Civil Procedure. The hearing shall be commenced
within thirty (30) Days after the selection of the third arbitrator. The
parties and the arbitrators shall proceed diligently and in good faith in
order that the arbitral award shall be made as promptly as possible. The
interpretation, construction and effect of this Agreement shall be governed
by the laws of Colorado, and to the maximum extent allowed by law, in all
arbitration proceedings the laws of Colorado shall be applied, without regard
to any conflicts of laws principles. All statutes of limitation and of repose
that would otherwise be applicable shall apply to any arbitration proceeding.
The tribunal shall not have the authority to grant or award indirect or
consequential damages, punitive damages or exemplary damages.


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<Page>


                                  EXHIBIT A

                       PRODUCTS QUALITY SPECIFICATIONS

<Table>
<Caption>

PROPANE

     PRODUCT CHARACTERISTICS     MINIMUM            MAXIMUM             TEST METHODS
     -----------------------     -------            -------            LATEST REVISION
                                                                       ---------------
<S>                              <C>           <C>                     <C>

1.  COMPOSITION                                                         ASTM E-260
PERCENT BY LIQUID VOLUME:

Ethane                                         As limited by other
                                                 components and
                                                 vapor pressure

HD-5 Propane                        90                 100

Propylene                                               5

Butanes & Heavier                                      2.5              ASTM D-2163

2.  VAPOR PRESSURE (psig @ 100                         208              ASTM D-1267
degrees F.)

3.  CORROSION
Copper Strip @ 100 deg. F.                             1-b              ASTM D-1838

4.  TOTAL SULFUR (PPM by                               123              ASTM D-2784
weight in liquid)

5.  NON-VOLATILE RESIDUE
     a) Milliliters @ 100 deg. F.                      0.05             ASTM D-2158
     b) Oil Stain                                      Pass


</Table>

10

<Page>

<Table>
<Caption>

NORMAL BUTANE

     PRODUCT CHARACTERISTICS     MINIMUM            MAXIMUM             TEST METHODS
     -----------------------     -------            -------            LATEST REVISION
                                                                       ---------------
<S>                              <C>           <C>                     <C>


1.  COMPOSITION                                                         ASTM E-260
PERCENT BY LIQUID VOLUME:

Isobutane and Lighter                                   5               ASTM D-2163

Butylene (Percent of N. Butane)                         1

Normal Butane & Butylene            95                 100               GPA 2165

Pentanes & Heavier                                      2

2.  VAPOR PRESSURE (psig @ 100                          50              ASTM D-1267
degrees F.)

3.  CORROSION
Copper Strip @ 100 deg. F.                             1-b              ASTM D-1838

4.   TOTAL SULFUR (PPM by                              140              ASTM D-3246
weight in liquid)

5.  VOLATILE RESIDUE
95% Evaporated-Temperature,                           plus 36           ASTM D-1837
degrees F.

</Table>




11

<Page>

<Table>
<Caption>

ISOBUTANE

     PRODUCT CHARACTERISTICS     MINIMUM            MAXIMUM             TEST METHODS
     -----------------------     -------            -------            LATEST REVISION
                                                                       ---------------
<S>                              <C>           <C>                     <C>


1.  COMPOSITION                                                         ASTM E-260
PERCENT BY LIQUID VOLUME:

Propane, Propylene and Lighter                          3               ASTM D-2163

Isobutane                           96                 100

Butylene, Normal Butane &                               4
Heavier


2.  VAPOR PRESSURE (psig @ 100                          62              ASTM D-1267
degrees F.)

3.  CORROSION
Copper Strip @ 100 deg. F.                             1-b              ASTM D-1838

4.  TOTAL SULFUR (PPM by                               140              ASTM D-3246
weight in liquid)

5.  VOLATILE RESIDUE
95% Evaporated-Temperature,                           plus 16           ASTM D-1837
degrees F.

6.  DRYNESS                                         No free water          Visual

</Table>





12

<Page>

<Table>
<Caption>

NATURAL GASOLINE

     PRODUCT CHARACTERISTICS     MINIMUM            MAXIMUM             TEST METHODS
     -----------------------     -------            -------            LATEST REVISION
                                                                       ---------------

<S>                              <C>           <C>                     <C>


1.  COMPOSITION                                                         ASTM E-260
PERCENT BY LIQUID VOLUME:

Butanes and Lighter                                     3                GPA 2165

Pentanes & Heavier                  97                 100


2.  VAPOR PRESSURE (psig @ 100                          14              ASTM D-323
degrees F.)

3.  CORROSION
Copper Strip @ 104 deg. F.                             1-b              ASTM D-130

4.  DOCTOR TEST                                      Negative            GPA 1138

5.  DRYNESS                                        No free water          Visual

6.  COLOR                                            No Color          Field White Cup
                                                                           Method
          Saybolt No.            plus 25                                Lab-ASTM D-156

7.  DISTILLATION
     End Point, deg. F.                                    375               ASTM D-216

</Table>



13