Document:

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                                                                Exhibit 10.10(b)

"Pages where confidential treatment has been requested are marked 'Confidential
Treatment Requested.' The redacted material has been separately filed with the
Commission, and the appropriate section has been marked at the appropriate place
and in the margin with a star (*)."

                       'Confidential Treatment Requested'

                                SECOND AMENDMENT
                                       TO
                  MASTER NATURAL GAS LIQUIDS PURCHASE AGREEMENT

          This Amendment is executed this 22 day of March, 1999, to be effective
as of the Effective Date provided herein, by and between CHEVRON U.S.A. INC.
("Chevron") and DYNEGY MIDSTREAM SERVICES, LIMITED PARTNERSHIP ("Dynegy").

          WHEREAS, Chevron and Dynegy (formerly known as Warren Petroleum
Company, Limited Partnership) entered into that certain Master Natural Gas
Liquids Purchase Agreement, effective as of September 1, 1996 (the "Master NGL
Agreement"), as amended, under which Dynegy agreed to purchase, and Chevron
agreed to sell, all of Chevron's right, title and interest in certain natural
gas liquids ("NGLs"), as further described in the Master NGL Agreement; and

          WHEREAS, Chevron and Dynegy now wish to amend the Master NGL Agreement
as set forth herein;

          NOW THEREFORE, in consideration of the premises and other valuable
consideration, Chevron and Dynegy agree as follows:

          1. All references in the Master NGL Agreement to "Warren Petroleum
Company, Limited Partnership" shall hereafter be deemed to refer to Dynegy.

          2. Section 5.1 of the Master NGL Agreement is hereby deleted in its
entirety and replaced by the following new Section 5.1:

               5.1 Except as otherwise provided herein, WPC shall pay CUSA for
*         the NGLs purchased hereunder (i) a price equal to [REDACTED] as
          quoted by the Oil Price Information Service ("OPIS") for Mont
          Belvieu, Texas (Non-TET) for the Month in which NGLs are delivered
          to WPC, less Mont Belvieu T&F Costs, for the volumes of NGLs
          delivered to WPC at the applicable Delivery Point at the tailgate of
          the Plants listed in Exhibit "B" which is attached hereto and made a
*         part hereof, (ii) a price equal to [REDACTED] as quoted by OPIS for
          Group 140 (Conway, Kansas) for the Month in which NGLs are delivered
          to WPC, less Conway T&F Costs, for the volumes of NGLs delivered to
          WPC at the applicable Delivery Point at the tailgate of the Plants
          listed in Exhibit "C" which is attached hereto and made a part
*         hereof (iii) a price equal to [REDACTED] as quoted by OPIS for Mont
          Belvieu, Texas (Non-TET) for the Month in which NGLs are delivered
          to WPC, less Mont Belvieu T&F Costs, plus the T&F Costs paid by CUSA
          to a third Person to fractionate Raw NGL Mix into Fractionated NGLs
          for the volumes of NGLs delivered to WPC at the applicable Delivery
          Point at the tailgate of the Plants listed in Exhibit "D" which is
          attached hereto and made a part hereof, (iv)

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                        'Confidential Treatment Requested'

*         [REDACTED] percent of the Netback Price for the volumes of NGLs
          delivered to WPC at the applicable Delivery Point at the tailgate of
          the Plants listed in Exhibit "E" which is attached hereto and made a
          part hereof, and (v) the price for each NGL delivered to WPC at the
          Delivery Point at the tailgate of the Venice Fractionator as set
          forth in Exhibit "F" which is attached hereto and made a part
          hereof. WPC shall use every reasonable effort to obtain the highest
          Netback Price for NGLs. Notwithstanding the foregoing, it is
          understood and agreed that WPC's share of the Netback Price received
*         from the disposition of NGLs (i.e., [REDACTED] as set forth in (iv)
*         above), shall never be less than [REDACTED] per Gallon of each NGL
          delivered to WPC at the Delivery Point. The Parties recognize and
          acknowledge that during any given Month, NGLs delivered to WPC may
          be sold to WPC under different pricing scenarios as set forth in (i)
          through (iv) above, depending on the particular market for such NGLs
          as set forth in Exhibits "B", "C", "D" and "E".

          3. This Amendment is effective on and after February 1, 1999 (the
"Effective Date").

          4. All other provisions of the Master NGL Agreement shall remain in
full force and effect.

          IN WITNESS WHEREOF, Chevron and Dynegy have each caused their duly
authorized representative to execute this Amendment.

DYNEGY MIDSTREAM SERVICES,                  CHEVRON U.S.A. INC.
LIMITED PARTNERSHIP
By Dynegy Midstream G.P., Inc.,
its General Partner

By: /s/ Ron Logan                           By:    /s/ Larry D. Robison
Name:   Ron Logan                           Name:  Larry D. Robison
Title:  DIRECTOR SUPPLY AND                 Title: Manager, Transportation and
        TERM SALES                          Regulatory

                                      2<Page>

                                                        Exhibit 10.10(c)

                                  AMENDMENT TO
                           MASTER NATURAL GAS LIQUIDS
                               PURCHASE AGREEMENT

     This Amendment to Master Natural Gas Liquids Purchase Agreement is executed
this 27th day of November, 2000, to be effective as of the Effective Date
provided herein, by and between CHEVRON U.S.A. INC. ("Chevron") and DYNEGY
MIDSTREAM SERVICES, LIMITED PARTNERSHIP ("Dynegy"), formerly known as Warren
Petroleum Company, Limited Partnership.

     WHEREAS, Chevron and Dynegy entered into that certain Master Natural Gas
Liquids Purchase Agreement, effective as of September 1, 1996, as previously
amended (the "NGL Agreement"), pursuant to which Chevron agreed to sell certain
NGLs to Dynegy and Dynegy agreed to purchase such NGLs from Chevron; and

     WHEREAS, by Amendment to Natural Gas Liquids Purchase Agreement dated
September 12, 2000 (the "September Amendment"), Chevron and Dynegy amended
certain portions of the NGL Agreement.

     WHEREAS, in Section 4 of the September Amendment, Dynegy and Chevron agreed
that the Temporary Revision to Exhibit "B" (product pricing provisions) would be
effective through November 30, 2000;

     WHEREAS, Chevron and Dynegy now desire to extend the effectiveness of the
Temporary Revision to Exhibit "B."

     NOW THEREFORE, in consideration of the mutual covenants and agreements
herein contained, Dynegy and Chevron agree as follows:

     1.   For the purpose of this Amendment, capitalized terms used but not
defined herein shall have the same meaning as set forth in the NGL Agreement
and/or the September Amendment.

     2.   Section 3 of the September Amendment is hereby deleted and replaced in
its entirety with the following:

               3.   For the period from September 1, 2000, through March 31,
          2002 (the "Temporary Period"), Exhibit "F" to the NGL Agreement is
          hereby deleted in its entirety and replaced with the Temporary
          Revision to Exhibit "F" which is attached hereto and made a part
          hereof.

     3.   Section 4 of the September Amendment is hereby deleted and replaced in
its entirety with the following:
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               4.   It is understood and agreed that during the Temporary Period
          the provisions of Section 5.5 of the NGL Agreement, providing for the
          annual renegotiation of the pricing/basis differentials, are hereby
          suspended. Upon expiration of the Temporary Period, the provisions of
          Section 5.5 of the NGL Agreement shall thereafter apply, except that
          (a) the Parties hereby acknowledge that timely notice requesting a
          renegotiation which would otherwise be required to be made at least
          ninety (90) Days prior to September 1, 2001, is deemed to have already
          been given and no further notice will be required, (b) the effective
          date of any change to such basis differentials as a result of such
          renegotiations, whether determined by mutual agreement or otherwise,
          shall be April 1, 2002, and (c) nothing in this provision is intended
          to change the notice requirements or effective date of any subsequent
          annual renegotiation.

     4.   Except as specifically set forth herein, the NGL Agreement remains in
full force and effect according to its terms.

     IN WITNESS WHEREOF, the Parties hereto have caused this Amendment to be
executed by their duly authorized representatives.

DYNEGY MIDSTREAM SERVICES,                CHEVRON U.S.A. INC.
       LIMITED PARTNERSHIP
By:    Dynegy Midstream G.P., Inc.,
       General Partner

By: /s/ Ron M. Logan                      By: /s/ R.C. NEFF
   -----------------------------------       -----------------------------------

Printed Name:  Ron M. Logan               Printed Name: R.C. NEFF
             -------------------------                 -------------------------

Title: VICE PRESIDENT                     Title: Manager, Midstream
      --------------------------------          --------------------------------<PAGE>

                                                         Exhibit 10.10(d)

"Pages where confidential treatment has been requested are marked 'Confidential
Treatment Requested.' The redacted material has been separately filed with the
Commission, and the appropriate section has been marked at the appropriate
place and in the margin with a star (*)."

                     'Confidential Treatment Requested'

                                  AMENDMENT TO
                  MASTER NATURAL GAS LIQUIDS PURCHASE AGREEMENT

          This Amendment is executed this 29th day of November, 2001, to be
effective as the Effective Date, as such term is defined hereinafter, by and
between CHEVRON U.S.A. INC. ("CUSA") and DYNEGY MIDSTREAM SERVICES, LIMITED
PARTNERSHIP ("Dynegy"), formerly known as Warren Petroleum Company, Limited
Partnership.

          WHEREAS, CUSA and Dynegy entered into that certain Master Natural Gas
Liquids Purchase Agreement, effective as of September 1, 1996, as amended (the
Master Agreement"), under which Dynegy agreed to purchase, and Chevron agreed to
sell, all of CUSA's right, title and interest in certain natural gas liquids
("NGLs") produced at a number of facilities more particularly described in the
Master Agreement (the "Facilities"); and

          WHEREAS, pursuant to Section 5.4 of the Master Agreement, CUSA and
Dynegy have negotiated new pricing provisions applicable at some of the
Facilities and now wish to amend the Master Agreement in order to implement such
new pricing provisions;

          NOW THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, CUSA and Dynegy agree as follows:

          1. Article I, DEFINITIONS, the definition of "Mont Belvieu T&F Costs"
shall be deleted in its entirety and replaced with the following definition:

          MONT BELVIEU T&F COSTS shall mean Pipeline Transportation Costs to
          Mont Belvieu, a loss allowance no greater than that charged to an
          unaffiliated third Person, and a per Gallon fractionation fee
          calculated as follows:

               Fractionation Fee Formula (cents per Gallon):

*              [[REDACTED] + [REDACTED] * (Fuel cm/ Fuel base) + [REDACTED]
*              (Elec pm/ Elec base) + [REDACTED] * (CPIU/CPI base)]

               Where:

               Fuel cm   = The current Month fuel cost (in $/MMBtu) equivalent
                           to the Houston Ship Channel Index of INSIDE FERC'S
                           GAS MARKET REPORT, for natural gas (large packages).

*              Fuel base = [REDACTED] per MMBtu

               Elec pm   = The combined average cost of purchased electricity
                           (in CENTS/Kilowatt hour) at the Fractionator during
                           the preceding Month.

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                            'Confidential Treatment Requested'

*              Elec base = [REDACTED] per Kilowatt hour.

               CPIU      = The latest available Consumer Price Index, All Urban
                           Consumers - ("CPI-U"), U.S. city average, All Items,
                           as published by the United States Bureau of Labor
                           Statistics (the "BLS") or any successor agency
                           thereto (the "CPI-U Index"). The CPI-U Index shall
                           be taken from the data published by the Bureau of
                           Labor Statistics, as of the date hereof,
                           electronically at the following Internet address:
                           ftp://ftp.bls.gov/pub/special.reguests/cpi/cpiai.txt,
                           or at any successor Internet address or as same is
                           published in hardcopy form.

               CPIU base = The Consumer Price Index, All Urban Consumers -
                           ("CPI-U"), U.S. city average, All Items, as
                           published by the United States Bureau of Labor
                           Statistics for the Month of July 2001.

          2. Article V, PRICE, Section 5.1 shall be deleted in its entirety and
replaced with the following:

               5.1 Except as otherwise provided herein, Dynegy shall pay CUSA
*         for the NGLs purchased hereunder (i) a price equal to [REDACTED] as
          quoted by the Oil Price Information Service ("OPIS") for Mont Belvieu,
          Texas (Non-TET) for the Month in which NGLs are delivered to Dynegy,
          less Mont Belvieu T&F Costs, for the volumes of NGLs delivered to
          Dynegy at the applicable Delivery Point at the tailgate of the Plants
          listed in Exhibit "B" which is attached hereto and made a part hereof,
          EXCEPT THAT (1) the OPIS category for EP Mix at Mont Belvieu, Texas
          will be used in pricing the Ethane Component and (2) the OPIS category
          "Other (Non-TET)" at Mont Belvieu, Texas will be used in pricing the
*         Normal Butane Component, (ii) a price equal to [REDACTED] as quoted
          by OPIS for Group 140 (Conway, Kansas) for the Month in which NGLs are
          delivered to Dynegy, less Conway T&F Costs, for the volumes of NGLs
          delivered to Dynegy at the applicable Delivery Point at the tailgate
          of the Plants listed in Exhibit "C" which is attached hereto and made
*         a part hereof, (iii) a price equal to [REDACTED] as quoted by OPIS for
          Mont Belvieu, Texas (Non-TET) for the Month in which NGLs are
          delivered to Dynegy, less Mont Belvieu T&F Costs, plus the T&F Costs
          paid by CUSA to a third Person to fractionate Raw NGL Mix into
          Fractionated NGLs for the volumes of NGLs delivered to Dynegy at the
          applicable Delivery Point at the tailgate of the Plants listed in
          Exhibit "D" which is attached hereto and made a part hereof, (iv)
*         [REDACTED] percent of the Netback Price for the volumes of NGLs
          delivered to Dynegy at the applicable Delivery Point at the tailgate
          of the Plants listed in Exhibit "E" which is attached hereto and made
          a part hereof, EXCEPT THAT, with respect to the NGLs produced at the
          Plants listed in Exhibit "E" situated in the State of California and
          sold to Dynegy, the price payable by Dynegy to CUSA shall be
*         [REDACTED] percent of the Netback Price, and (v) the price for each
          NGL delivered to Dynegy at the Delivery Point at the tailgate of the
          Venice Fractionator as set forth in Exhibit "F" which is attached
          hereto and made a part hereof. Dynegy shall use every reasonable
          effort to obtain the highest

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                      'Confidential Treatment Requested'

          Netback Price for NGLs. Notwithstanding the foregoing, it is
          understood and agreed that Dynegy's share of the Netback Price
          received from the disposition of NGLs, shall never be less than
*         [REDACTED] per Gallon of each NGL delivered to Dynegy at the
          Delivery Point. The Parties recognize and acknowledge that during any
          given Month, NGLs delivered to Dynegy may be sold to Dynegy under
          different pricing scenarios as set forth in (i) through (iv) above,
          depending on the particular market for such NGLs as set forth in
          Exhibits "B", "C", "D" and "E".

          3. Article V, PRICE, Section 5.2 shall be deleted in its entirety and
replaced with the following:

               5.2 With respect to the Raw NGL Mix delivered by or on behalf of
          CUSA to Dynegy, the price set forth in Section 5.1 above shall be
          based on the Components contained in the Raw NGL Mix delivered to
          Dynegy at the tailgate of the applicable processing Plant, EXCEPT
          THAT, for any Raw NGL Mix transported to Mont Belvieu for
          fractionation, (i) the OPIS category for EP Mix at Mont Belvieu, Texas
          will be used in pricing the Ethane Component and (ii) the OPIS
          category "Other (Non-TET)" at Mont Belvieu, Texas will be used in
          pricing the Normal Butane Component.

          4. Notwithstanding the provisions of Section 5.4 of the Master
Agreement, the parties hereto acknowledge that the new pricing provision set
forth above as implemented by this Amendment shall be effective on and after
October 1, 2001 (the "Effective Date"). The parties hereto further acknowledge
and agree that the pricing provision as set forth in the Master Agreement prior
to this Amendment shall continue to apply to those NGLs delivered to Dynegy at
the Delivery Points prior to October 1, 2001.

          5. All other provisions of the Master Agreement shall remain in full
force and effect.

          IN WITNESS WHEREOF, CUSA and Dynegy have each caused their duly
authorized representative to execute this Amendment effective as of the
Effective Date.

DYNEGY MIDSTREAM SERVICES,                          CHEVRON U.S.A. INC.
LIMITED PARTNERSHIP
By Dynegy Midstream G.P., Inc.,
its General Partner

By: /s/ Stephen A. Furbacher                       By:   /s/ R.C. Neff
   -------------------------                           ----------------
Name:  Stephen A. Furbacher                        Name:   R.C. Neff
     -------------------------                          ---------------
Title: President                                   Title: Manager, Midstream

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