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Filed Pursuant to Rule 424(b)(2)
Commission File No. 333-164323

This prospectus supplement relates to an effective registration statement under the Securities Act of 1933, but is not complete and may be changed. This prospectus supplement and the accompanying base prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to Completion, dated February 9, 2011

PROSPECTUS SUPPLEMENT
(To Prospectus dated January 13, 2010)

$300,000,000

MarkWest Energy Partners, L.P.
MarkWest Energy Finance Corporation

         % Senior Notes due 2021

MarkWest Energy Partners, L.P. and MarkWest Energy Finance Corporation are offering $300,000,000 aggregate principal amount of         % Senior Notes due 2021.

The notes will mature on                           , 2021. Interest on the notes will accrue from                           , 2011 and we will pay interest twice a year, beginning on                           , 2011.

We may redeem some or all of the notes at any time on or after                           , 2016 at the redemption prices listed in this prospectus supplement, together with accrued and unpaid interest, if any, to the date of redemption, and we may redeem all of the notes at any time prior to                           , 2016 at the make-whole redemption price specified in this prospectus supplement. In addition, prior to                           , 2014, we may redeem up to 35% of the aggregate principal amount of the notes in an amount not greater than the proceeds of certain equity offerings at the redemption price specified in this prospectus supplement under "Description of Notes—Optional Redemption." If we sell certain of our assets or experience specific kinds of changes of control, we must offer to repurchase the notes.

The notes will be the senior unsecured obligations of MarkWest Energy Partners, L.P. and MarkWest Energy Finance Corporation, a wholly-owned subsidiary of ours that has no material assets and was formed for the sole purpose of being a co-issuer of some of our indebtedness, including the notes. The notes will rank equally with all of our existing and future senior debt, senior to all of our future subordinated debt and effectively junior in right of payment to all of our existing and future senior secured debt to the extent of the value of the collateral securing such indebtedness. The notes will be guaranteed on a senior unsecured basis by each of our existing wholly-owned subsidiaries and certain of our future subsidiaries.

Investing in the notes involves risks. Please read "Risk Factors" beginning on page S-17.

None of the Securities and Exchange Commission, any state securities commission or any other regulatory body has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying base prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Barclays Capital Inc. expects that the delivery of the notes will be made to investors in book-entry form through The Depository Trust Company on or about                           , 2011.

Sole Book Running Manager

Barclays Capital

Prospectus Supplement dated                           , 2011

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Prospectus Supplement

        This document is in two parts. The first part is this prospectus supplement, which describes our business and the specific terms of this offering of the notes. The second part is the accompanying base prospectus, which gives more general information, some of which may not apply to this offering of the notes. Generally, when we refer only to the "prospectus," we are referring to both parts combined. If the information about the notes offering varies between this prospectus supplement and the accompanying base prospectus, you should rely on the information in this prospectus supplement.

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        Any statement made in this prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other subsequently filed document that is also incorporated by reference into this prospectus modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus. Please read "Where You Can Find More Information" on page S-82 of this prospectus supplement.

        We expect delivery of the notes will be made against payment therefor on or about                        , 2011, which is the tenth business day following the date of pricing of the notes (such settlement being referred to as "T+10"). Under Rule 15(c)6-1 of the Securities Exchange Act of 1934, as amended, trades in the secondary market generally are required to settle in three business days unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes on the date of pricing of the notes or during the next succeeding seven business days will be required, by virtue of the fact that the notes initially will settle in T+10, to specify an alternate settlement cycle at the time of any such trade to prevent failed settlement and should consult their own advisers.

        You should rely only on the information contained in or incorporated by reference into this prospectus supplement, the accompanying base prospectus and any free writing prospectus relating to this offering of the notes. Neither we nor the underwriter has authorized anyone to provide you with additional or different information. If anyone provides you with additional, different or inconsistent information, you should not rely on it. We are offering to sell the notes, and seeking offers to buy the notes, only in jurisdictions where offers and sales are permitted. You should not assume that the information contained in this prospectus supplement, the accompanying base prospectus or any free writing prospectus is accurate as of any date other than the dates shown in these documents or that any information we have incorporated by reference herein is accurate as of any date other than the date of the document incorporated by reference. Our business, financial condition, results of operations and prospects may have changed since such dates.

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SUMMARY

        This summary highlights information contained elsewhere in this prospectus supplement and the accompanying base prospectus. It does not contain all of the information that you should consider before making an investment decision. For a more complete understanding of this offering, you should read this entire prospectus supplement, the accompanying base prospectus, any free writing prospectus relating to the notes and the documents incorporated herein by reference, including our historical financial statements and the notes thereto, which are incorporated herein by reference from our annual report on Form 10-K for the year ended December 31, 2009, and our quarterly reports on Form 10-Q for the quarters ended March 31, 2010, June 30, 2010 and September 30, 2010. Please read "Where You Can Find More Information" on page S-82 of this prospectus supplement. Please read "Risk Factors" beginning on page S-17 of this prospectus supplement and Item 1A. "Risk Factors" in our annual report on Form 10-K for the year ended December 31, 2009 and our quarterly report on Form 10-Q for the quarter ended September 30, 2010 for information regarding risks you should consider before buying notes in this offering. We include a glossary of some of the terms used in this prospectus supplement as Appendix A.

        For purposes of this prospectus supplement and the accompanying base prospectus, unless the context clearly indicates otherwise, "we," "us," "our" and the "Partnership" refer to MarkWest Energy Partners, L.P. and, when applicable, its consolidated subsidiaries; and "MarkWest Hydrocarbon" refers to MarkWest Hydrocarbon, Inc. and its direct and indirect consolidated subsidiaries.

MarkWest Energy Partners, L.P.

        We are a master limited partnership engaged in the gathering, transportation and processing of natural gas; the transportation, fractionation, marketing and storage of NGLs; and the gathering and transportation of crude oil. We have extensive natural gas gathering, processing and transmission operations in the southwest, Gulf Coast and northeast regions of the United States, including the Marcellus Shale, and we are the largest natural gas processor in the Appalachian region.

Business Strategy

        Our primary business strategy is to provide top-tier midstream services by developing and operating high-quality, strategically-located assets in the United States. We plan to accomplish this through the following:

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Developing long-term integrated relationships with our producer customers.  As a top-rated midstream service provider, we have worked to redefine our relationships with our key producer customers, as evidenced by our relationships with the primary producers in the Woodford Shale, the Marcellus Shale and the Huron/Berea Shale. We will continue to develop relationships that are characterized by joint planning for the development of the emerging resource plays and our commitment to grow to meet the specific needs of our customers.



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Expanding operations through organic growth projects.  By expanding our existing infrastructure and customer relationships, we intend to continue to grow in our primary areas of operation to meet the anticipated demand for additional midstream services. During 2010, we estimate that we and our joint venture partner spent approximately $500 million in total capital to develop midstream infrastructure in the Marcellus Shale through MarkWest Liberty Midstream & Resources, L.L.C. ("Liberty Midstream"), a joint venture with The Energy & Minerals Group ("EMG"), and expanded several of our gathering and processing operations in our Southwest segment, including the Woodford gathering system in the Arkoma Basin, and our operations in East Texas and in Western Oklahoma, including Stiles Ranch. Our share of these growth and expansion capital expenditures is estimated to be approximately $300 million, and the remainder was funded through contributions from our Liberty Midstream joint venture partner and existing cash balances in the joint venture.

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Maintaining our financial flexibility.  In April 2010, we received net proceeds of approximately $142.3 million from the issuance of common units. In July 2010, we entered into an amended and restated credit agreement (the "Amended and Restated Credit Agreement") that provides for a revolving loan facility (the "Credit Facility") of up to $705 million, with an uncommitted accordion feature of up to $195 million. In November 2010, we received net proceeds of approximately $491 million from the issuance of long-term debt, a portion of which we used to retire all of our outstanding 6.875% senior notes due 2014 (the "2014 Notes"). In January 2011, we received net proceeds of approximately $138.1 million from the issuance of common units, which we used to fund a portion of the cost associated with the EQT Transaction (as defined below). Our goal is to maintain a capital structure with approximately equal amounts of debt and equity on a long-term basis. We also consider the use of alternative financial strategies such as entering into joint venture arrangements and the sale of selected assets that are not a core component of our long-term objectives. Our ability to borrow under our Credit Facility and ability to issue additional partnership units and long-term debt, our strong relationships with our joint venture partners, and the opportunistic sale of non-strategic assets should provide us with the flexibility to facilitate the execution of our business strategy.



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Reducing the sensitivity of our cash flows to commodity price fluctuations.  We intend to continue to secure long-term, fee-based contracts in order to further minimize our exposure to short-term changes in commodity prices. We expect that our fee-based contracts will account for approximately 50% of our net operating margin by 2012. We also engage in risk management activities in order to reduce the effect of commodity price volatility related to future sales of natural gas, NGLs and crude oil. We may utilize a combination of fixed-price forward contracts, fixed-for-floating price swaps, and options available in the over-the-counter market. We monitor these activities through enforcement of our commodity risk management policy. For more details about our commodity risk management policy, please read Item 1—"Financial Statements" and Item 3—"Quantitative and Qualitative Disclosures about Market Risk" included in our quarterly report on Form 10-Q for the quarter ended September 30, 2010, which is incorporated herein by reference.



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Increasing utilization of our facilities.  We seek to increase the utilization of our existing facilities by providing additional services to our existing customers, and by establishing relationships with new customers. We also continue to develop additional capacity at several of our facilities, which enables us to increase throughput with minimal incremental costs.



•

Expanding operations through strategic acquisitions.  We intend to continue pursuing strategic acquisitions of assets and businesses in our existing areas of operation that leverage our current asset base, personnel and customer relationships. We may also seek to acquire assets in certain regions outside of our current areas of operation. We believe that our capital structure, which no longer includes incentive distribution rights, positions us to compete more effectively for future transactions.

        Execution of our business strategy has allowed us to grow substantially since our inception. The majority of our growth since 2006 has focused on the development of natural gas supplies in emerging resource plays. As a result, we now have a strong presence in emerging resource plays that are expected to be significant sources of domestic natural gas production in the future, including the

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Woodford Shale, Haynesville Shale, Granite Wash, Marcellus Shale and the Huron/Berea Shale. The following table summarizes the capital investments associated with growth projects and acquisitions.

Competitive Strengths

        We believe that the following competitive strengths position us to continue to successfully execute our primary business strategy:

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Leading position in the early development of the Marcellus Shale.  As a result of strategic agreements with key producers, we are currently the largest gatherer and processor of natural gas in the Marcellus Shale. These long-term agreements include significant acreage dedications in the rich-gas areas of the shale. Our gathering systems and processing plants in the Marcellus Shale are relatively new and highly efficient, and we continue to expand these facilities with a strong financial partner in EMG under the Liberty Midstream joint venture arrangement. Leveraging our current and planned fractionation capacity, our strategic transportation and storage agreements that provide access to NGL markets, and our extensive marketing experience in the northeast region, we are positioned to offer fully integrated midstream services for the producers in the Marcellus Shale.



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Strategic and growing position with high-quality assets in the Southwest and the Gulf Coast.  Our acquisitions and internal growth projects have allowed us to establish and expand our presence in several long-lived natural gas supply basins in the Southwest, particularly in Texas and Oklahoma. In late 2006, we built the largest gathering system to date in the Woodford Shale play in Southeast Oklahoma pursuant to our agreement with Newfield Exploration Mid-Continent Inc. Our Gulf Coast assets provide high quality service to six strategically located Gulf Coast refineries that we believe will continue to play a key role in supporting U.S. demand for refined petroleum products in the long term. All of our major acquisitions in these regions have been characterized by several common critical success factors that include:



•

an existing strong competitive position;



•

access to a significant reserve or customer base with a stable or growing production profile;



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ample opportunities for long-term continued organic growth;



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ready access to markets; and



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close proximity to other acquisition or expansion opportunities.

Specifically, our East Texas and Appleby gathering systems are located in the East Texas Basin, producing from both the Cotton Valley and Travis Peak reservoirs as well as the Haynesville

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Shale. Our western Oklahoma assets include the Foss Lake gathering system and the associated Arapaho gas processing plants located in the Anadarko Basin in Oklahoma and our Granite Wash gathering system in the Texas panhandle. Additionally, as mentioned above, our Woodford gathering system is located in the Woodford Shale reservoir. Our gathering systems are relatively new and provide producers with low-pressure and fuel-efficient service, a significant competitive advantage for us over many competing gathering systems in those areas.

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Leading position and continued expansion in the Appalachian Basin.  We are the largest processor of natural gas in Appalachia. We believe our significant presence and asset base provide us with a competitive advantage in capturing and contracting for new supplies of natural gas. The Appalachian Basin is a large natural gas-producing region characterized by long-lived reserves with modest decline rates and natural gas with high NGL content. Our concentrated infrastructure, available land, storage assets and expansion plans in Appalachia should continue to provide us with a platform for additional cost-effective expansion opportunities. In addition, on February 1, 2011, we acquired from EQT Corporation (together with its affiliates, "EQT") two gas processing plants located near Langley and Maytown, Kentucky as well as a partially constructed NGL pipeline. The acquisition expands our long-standing relationship with EQT, which is a leading producer in the Huron/Berea Shale in Kentucky and West Virginia and further solidifies our position as the largest processor of natural gas in the Appalachian region and the leading provider of fractionation and marketing services in the Northeast. Please read "—Recent Developments—EQT Transaction" for additional information regarding the acquisition.



•

Long-term contracts.  We believe that our long-term contracts, which we define as contracts with remaining terms of four years or more, enhance the stability of our cash flow profile. In East Texas, approximately 73% of our gathering volumes were under contract for longer than five years as of December 31, 2009. Due to new contracts signed in late 2008 and 2009, as of December 31, 2009, approximately 57% of our daily throughput in the Western Oklahoma gathering system and Arapaho processing plants was subject to contracts with remaining terms of more than eight years. As of December 31, 2009, approximately 94% of our throughput in the Woodford gathering system was subject to contracts with remaining terms of more than seven years. Also, as of December 31, 2009, in our Southwest segment, two of our lateral pipelines operated under fixed-fee contracts for the transmission of natural gas that expire in approximately 19 and 11 years, respectively. In Appalachia, our natural gas processing and NGL fractionation contracts with remaining terms of more than five years accounted for approximately 83% of our volumes as of December 31, 2009. In our Gulf Coast segment, as of December 31, 2009, approximately 56% of our volumes were under contract for more than four years. In our Liberty segment, as of December 31, 2009, all gathering and processing agreements with significant dedicated acreage had remaining terms of at least ten years.



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Experienced management team with operational, technical and acquisition expertise.  Each member of our executive management team has substantial experience in the energy industry. Our facility managers have extensive experience operating our facilities. Our operational and technical expertise has enabled us to upgrade our existing facilities, as well as to design and build new facilities. Since our initial public offering in May 2002, our management team has utilized a disciplined approach to analyze and evaluate numerous acquisition opportunities, and has completed twelve acquisitions.

Our Operations

        We conduct our business in four reportable segments: Southwest, Northeast, Liberty and Gulf Coast. In addition to our non-controlling interest in Centrahoma Processing LLC ("Centrahoma"), we have seven distinct operating areas within these segments that are described below. For full-year 2010,

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we estimate that total capital to fund identified organic growth and expansion projects was approximately $500 million. Our share of this total capital was approximately $300 million, and the remainder was funded through contributions from our Liberty Midstream joint venture partner and existing cash balances in the Liberty Midstream joint venture.

Southwest

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East Texas.  We own a system that consists of natural gas gathering pipelines, centralized compressor stations, a natural gas processing facility and an NGL pipeline. The East Texas system is located in Panola, Harrison and Rusk Counties and services the Carthage Field. Producing formations in Panola County consist of the Cotton Valley, Pettit, Travis Peak and Haynesville formations. For natural gas that is processed in this area, we purchase the NGLs from the producers primarily under percent-of-proceeds arrangements, or we transport volumes for a fee.



•

Oklahoma.  We own a Foss Lake natural gas gathering system and the Arapaho I and II natural gas processing plants, all located in Roger Mills, Custer and Ellis Counties of western Oklahoma. The gathering portion consists of a pipeline system that is connected to natural gas wells and associated compression facilities. The majority of the gathered gas ultimately is compressed and delivered to the processing plants. We also own and operate a gathering system in the Granite Wash formation in the Texas panhandle that is connected to our Foss Lake processing plants and our Grimes gathering system that is located in Roger Mills and Beckham Counties in western Oklahoma. In addition, we own a natural gas gathering system in the Woodford Shale in the Arkoma Basin of southeast Oklahoma. Natural gas gathered in the Woodford system is processed by Centrahoma, in which we have a 40% non-operating membership interest.

Through our joint venture MarkWest Pioneer, L.L.C. ("MarkWest Pioneer"), we operate the Arkoma Connector Pipeline, a 50-mile FERC-regulated pipeline that interconnects with Midcontinent Express Pipeline and Gulf Crossing Pipeline at Bennington, Oklahoma and is designed to provide approximately 638,000 Dth/d of Arkoma Basin takeaway capacity. For a complete discussion of the formation of, and accounting treatment for, MarkWest Pioneer, please read Note 4 to our historical consolidated financial statements included in our annual report on Form 10-K for the year ended December 31, 2009.

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Other Southwest.  We own a number of natural gas gathering systems in Texas, Louisiana, Mississippi and New Mexico, including the Appleby gathering system in Nacogdoches County, Texas. We gather a significant portion of the natural gas produced from fields adjacent to our gathering systems, including from wells targeting the Haynesville formation. In many areas we are the primary gatherer, and in some of the areas served by our smaller systems we are the sole gatherer. In addition, we own four lateral pipelines in Texas and New Mexico.

Northeast

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Appalachia.  We are the largest processor of natural gas in the Appalachian Basin, with fully integrated processing, fractionation, storage and marketing operations. The Appalachian Basin is a large natural gas producing region characterized by long-lived reserves and modest decline rates. Our Appalachian assets include the Kenova, Boldman, Cobb and Kermit natural gas processing plants, an NGL pipeline, the Siloam NGL fractionation plant and two caverns for storing propane. In addition, on February 1, 2011, we acquired from EQT two gas processing plants located near Langley and Maytown, Kentucky as well as a partially constructed NGL pipeline. Please read "—Recent Developments—EQT Transaction" for additional information

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regarding the acquisition. The Appalachia operations include fractionation and marketing services on behalf of the Liberty segment.

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Michigan.  We own and operate a FERC-regulated crude oil pipeline in Michigan that provides transportation services for three shippers.

Liberty

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Marcellus Shale.  We operate natural gas gathering systems and processing facilities located primarily in southwestern Pennsylvania and northern West Virginia through Liberty Midstream. We have 155 MMcf/d of cryogenic processing capacity at our Houston, Pennsylvania processing complex and plan to complete the installation of a 200 MMcf/d cryogenic plant in the first half of 2011. We also plan to complete a 60,000 Bbl/d fractionation facility at our Houston complex in 2011. We commenced operation of a 135 MMcf/d cryogenic plant at our Majorsville site in the third quarter of 2010 and expect to increase the cryogenic processing capacity at this site to approximately 270 MMcf/d by the third quarter of 2011. In addition, in January 2011, we announced that Liberty Midstream intends to construct a 120 MMcf/d cryogenic processing plant and associated NGL gas pipeline in Logansport, West Virginia to process liquids-rich gas transported on EQT's Equitrans gas pipeline. Please read "—Recent Developments—Logansport Expansion" for additional information regarding the planned expansion. We expect the total planned processing capacity to be supported by existing and new long-term agreements with our producer customers. Until we have completed construction of our Houston fractionation facility, a significant portion of the raw NGLs produced at our Liberty facilities are fractionated at the Siloam NGL fractionation plant in our Northeast segment. Certain volumes of propane and raw NGLs produced at the Liberty facilities are sold without fractionation at Siloam. We have completed construction of an interconnect with a key interstate NGL pipeline, providing an additional market outlet for the propane. In addition, we are developing a market outlet for the ethane produced in the Marcellus Shale through a combined pipeline and marine project (the "Mariner Project") to deliver purity ethane to Gulf Coast markets. The Mariner Project is a joint project with Sunoco Logistics that is anticipated to have initial capacity to transport up to 50,000 Bbl/d of ethane by mid-2012 and may be expanded to support additional Marcellus production. For a complete discussion of the formation of, and accounting treatment for, Liberty Midstream, please read Note 4 to our historical consolidated financial statements included in our annual report on Form 10-K for the year ended December 31, 2009.

Gulf Coast

•

Javelina.  We own and operate the Javelina processing facility, a natural gas processing facility in Corpus Christi, Texas that treats and processes off-gas from six local refineries operated by three different refinery customers. We have a hydrogen supply agreement creating a long-term contractual obligation for the payment of processing fees in exchange for all of the hydrogen processed by the steam methane reformer ("SMR") that is operated by a third party. The hydrogen received under this agreement will be sold to a refinery customer pursuant to a corresponding long-term agreement. For further discussion of this agreement and the related divestiture of the SMR, please read Note 6 to our historical consolidated financial statements included in our annual report on Form 10-K for the year ended December 31, 2009.

Recent Developments

Senior Notes Offering and Tender Offers

        On November 2, 2010, we closed a public offering of $500 million aggregate principal amount of our 6.75% senior notes due 2020, resulting in net proceeds of approximately $491 million. Concurrently

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with the launch of our offering of senior notes due 2020, we commenced tender offers for any and all of the $375.0 million of our outstanding 2014 Notes.

        We used a portion of the net proceeds from the public offering to fund the tender offers for our 2014 Notes and a subsequent redemption in December 2010 of the 2014 Notes not purchased in the tender offers.

Logansport Expansion

        On January 4, 2011, Liberty Midstream announced it will construct a 120 MMcf/d cryogenic gas processing facility and associated NGL pipeline in Logansport, West Virginia by mid 2012 to process liquids-rich gas transported in EQT's Equitrans gas pipeline, which recently announced a significant expansion to increase transmission capacity. EQT has substantial rich-gas Marcellus acreage in northern West Virginia and has contracted with Liberty Midstream for the majority of the Logansport plant capacity. The NGLs recovered at Logansport will be transported via pipeline to Liberty Midstream's fractionation, storage, and marketing complex in Houston, Pennsylvania.

January Common Unit Offering

        On January 14, 2011, we completed a public offering of 3,450,000 common units at $40.13 per common unit, which included 450,000 common units sold pursuant to the underwriter's option to purchase additional common units. We received net proceeds of approximately $138 million from this common unit offering, after deducting underwriting discounts and estimated offering expenses, which we used to fund a portion of the cost associated with the EQT Transaction.

Majorsville Services Agreement

        On January 19, 2011, we announced that Liberty Midstream entered into a long-term agreement with affiliates of Chesapeake Energy Corporation ("Chesapeake") to provide additional natural gas midstream services for Chesapeake's substantial rich-gas Marcellus acreage in northern West Virginia. Liberty Midstream will provide the midstream services at its Majorsville, West Virginia processing complex, which includes a 135 MMcf/d cryogenic gas processing plant that is operating near capacity. Liberty Midstream is nearing completion of a second 135 MMcf/d cryogenic plant at Majorsville and is evaluating the addition of a third plant. The NGLs recovered at Majorsville are transported via pipeline to Liberty Midstream's fractionation, storage, and marketing complex in Houston, Pennsylvania.

EQT Transaction

        On February 1, 2011, we acquired from EQT a natural gas processing complex located near Maytown and Langley, Kentucky and an associated NGL pipeline for approximately $230 million, subject to post-closing purchase price adjustments (the "EQT Transaction"). The acquisition includes a 100 MMcf/d cryogenic processing plant, a 75 MMcf/d refrigeration processing plant, approximately 28,000 horsepower of compression, and a partially constructed NGL pipeline that we plan to complete. In conjunction with the acquisition, we executed a long-term agreement with EQT to provide processing services for EQT's Kentucky Huron shale gas and extended our existing agreement with EQT to provide NGL transportation, fractionation, and marketing services.

Tender Offer for 2016 Notes

        Concurrently with the launch of this offering, we commenced a tender offer for any and all of our outstanding 8.5% senior notes due 2016 (the "2016 Notes"). The aggregate principal amount outstanding of the 2016 Notes is $275 million. We are also soliciting consents to certain proposed amendments to the indenture governing the notes. We are offering to purchase the 2016 Notes for cash equal to 104.25% of their principal amount, together with accrued and unpaid interest to the purchase

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date, and pay for consents to the indenture amendments in an amount equal to an additional 3.0% of the principal amount of notes tendered before 5:00 p.m., New York City time, on February 23, 2011, unless extended by us. No consent fees will be paid to holders who tender their notes after 5:00 p.m., New York City time, February 23, 2011 and prior to the expiration of the tender offer at 11:59 p.m., New York City time, on March 9, 2011, unless extended by us. Our offer to purchase the 2016 Notes is being made on the terms and subject to the conditions set forth in an Offer to Purchase and Consent Solicitation Statement dated February 9, 2011.

        The tender offer and consent solicitation are conditioned upon, among other things, our completion of this offering so that with the net proceeds from this offering, together, if necessary, with cash on hand and borrowings under our Credit Facility, we will have sufficient funds to pay for all tendered 2016 Notes and delivered consents plus all related fees and expenses. However, this offering is not conditioned upon the consummation of the tender offer at any minimum level of acceptance.

        If fully subscribed by February 23, 2011, we expect that the tender offer and consent solicitation will result in a pre-tax charge to our net income of approximately $21 million, and that they will cost approximately $298 million (including accrued and unpaid interest and the consent fees), which would be funded predominately with a portion of net proceeds from this offering as described in "Use of Proceeds."

        There is no assurance that the tender offer for the 2016 Notes will be subscribed for in any amount.

Tender Offer for 2018 Notes

        Concurrently with the launch of this offering, we commenced a tender offer for up to $125 million aggregate principal amount of our outstanding 8.75% senior notes due 2018 (the "2018 Notes"). The aggregate principal amount outstanding of the 2018 Notes is $500 million. We are offering to purchase the 2018 Notes for cash in an amount to be determined based on a modified "dutch auction" procedure. In this procedure, each holder that tenders 2018 Notes will specify a bid price between 109.0% and 111.5% of the principal amount of 2018 Notes, which represents the minimum consideration such holder is willing to receive for those 2018 Notes. These bid amounts include an early tender payment of 3.0% of the principal amount of 2018 Notes tendered before 5:00 p.m., New York City time, on February 23, 2011 unless extended by us. No early tender payment will be paid to holders who tender their notes after 5:00 p.m., New York City time, on February 23, 2011, and prior to the expiration of the tender offer at 11:59 p.m., New York City time, on March 9, 2011, unless extended by us. Our offer to purchase the 2018 Notes is being made on the terms and subject to the conditions set forth in an Offer to Purchase dated February 9, 2011.

        The tender offer for our 2018 Notes is conditioned upon, among other things, the consummation of a new capital markets debt financing raising proceeds in an amount, when combined with cash on hand and borrowings under the Credit Facility, sufficient to pay for all tendered 2018 Notes, plus all related fees and expenses. However, this offering is not conditioned upon the consummation of the tender offer for the 2018 Notes at any minimum level of acceptance.

        There is no assurance that the tender offer for our 2018 Notes will be subscribed for in any amount. For the purposes of this prospectus supplement, we do not give effect to any of our 2018 Notes being tendered.

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PARTNERSHIP STRUCTURE AND MANAGEMENT

        The diagram below depicts our organization and ownership structure as of February 7, 2011, without giving effect to the Class A units:

        MarkWest Energy Finance Corporation, the co-issuer of the notes, is a direct wholly-owned subsidiary of MarkWest Energy Partners and carries on no independent business other than acting as a co-issuer of the notes and our other senior notes.

        For more details about our ownership structure, please read "Organizational Structure" included in Item 1 in our annual report on Form 10-K for the year ended December 31, 2009, which is incorporated herein by reference.

Management of MarkWest Energy Partners, L.P.

        Our general partner, which we indirectly own and control, has sole responsibility for conducting our business and for managing our operations. Our common unitholders have the right to elect the members of the board of directors of our general partner at our annual meeting of unitholders.

Principal Executive Offices and Internet Address

        Our principal executive offices are located at 1515 Arapahoe Street, Tower 1, Suite 1600, Denver, Colorado 80202. We maintain a website at http://www.markwest.com. The information on our website is not part of this prospectus supplement, and you should rely only on information contained in or incorporated by reference herein and any free writing prospectus filed in connection with this offering when making an investment decision.

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THE OFFERING

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SUMMARY HISTORICAL CONDENSED COMBINED FINANCIAL
AND OPERATING DATA

        The following tables show our summary historical financial and operating data as of and for the periods indicated. We derived the information in the following tables from, and that information should be read together with and is qualified in its entirety by reference to, our historical consolidated financial statements and the accompanying notes included in our annual report on Form 10-K for the year ended December 31, 2009, and our quarterly report on Form 10-Q for the quarter ended September 30, 2010, which are incorporated herein by reference. The tables should be read together with "Management's Discussion and Analysis of Financial Condition and Results of Operations," included in our annual report on Form 10-K for the year ended December 31, 2009, and our quarterly report on Form 10-Q for the quarter ended September 30, 2010, which are incorporated herein by reference.

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¹

Revenue, purchased product costs, facility expenses and interest expense have been impacted by our derivative instruments. Miscellaneous income (expense), net has been impacted by an embedded derivative related to certain outstanding senior notes. As discussed further in Note 7 to our historical consolidated financial statements included in our annual report on Form 10-K for the year ended December 31, 2009, which is incorporated herein by reference, volatility in any given period related to unrealized gains and losses on our derivative positions can be significant. The following table summarizes the unrealized and realized losses and gains for the periods indicated:

²

We define net operating margin as revenue, excluding any derivative gain (loss), less purchased product costs, excluding any derivative gain (loss). These charges have been excluded for the purpose of enhancing the understanding, by both management and investors of the underlying baseline operating performance of our contractual arrangements, which management uses to evaluate our financial performance for purposes of planning and forecasting. Net operating margin is not a measure calculated in accordance with GAAP and should not be considered in isolation from, or as a substitute for, net income, net income attributable to the Partnership, income from operations or cash flow from operating activities as reflected in our financial statements. Net operating margin does not have any standardized definition and therefore is unlikely to be comparable to similar measures presented by other reporting companies. Our use of net operating margin,

(footnotes continue on next page)

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and the underlying methodology in excluding certain charges, is not necessarily an indication of the results of operations that may be expected in the future, or that we will not, in fact, incur such charges in future periods. The following table reconciles net operating margin to (loss) income from operations, which is the most directly comparable GAAP financial performance measure:

³

In general, we define Adjusted EBITDA as net income (loss) adjusted for (i) depreciation, amortization, accretion, and impairment expense; (ii) interest expense; (iii) amortization of deferred financing costs; (iv) losses (gains) on the disposal of property, plant and equipment ("PP&E") and unconsolidated affiliates; (v) non-cash derivative activity; (vi) non-cash compensation expense; (vii) provision for income taxes; (viii) adjustment related to non-wholly owned subsidiaries; (ix) adjustments for cash flow from unconsolidated investments; and (x) losses (gains) relating to other miscellaneous non-cash amounts affecting net income for the period. Adjusted EBITDA is a financial performance measure used by management, industry analysts, investors, lenders, and rating agencies to assess the financial performance and operating results of the Partnership's ongoing business operations. Additionally, we believe Adjusted EBITDA provides useful information to investors for trending, analyzing, and benchmarking our operating results from period to period as compared to other companies that may have different financing and capital structures.

There are material limitations to using a measure such as Adjusted EBITDA, including the difficulty associated with using it as the sole measure to compare the results of one company to another, and the inability to analyze certain significant items that directly affect a company's net income or loss. Management compensates for these limitations by considering Adjusted EBITDA in conjunction with its analysis of other GAAP financial measures, such as gross profit, net income, net income attributable to the Partnership and cash flow from operating activities. In addition, our calculation of Adjusted EBITDA may not be consistent with similarly titled measures presented by other companies and should be viewed in conjunction with measurements that are computed in accordance with GAAP. The following table reconciles Adjusted EBITDA to net (loss) income, which is the most directly comparable GAAP financial performance measure:

⁴

Maintenance capital includes capital expenditures made to maintain our operating capacity and asset base. Growth capital includes expenditures made to expand the existing operating capacity, to increase the efficiency of our existing assets, and to facilitate an increase in volumes within our operations. Growth capital also includes costs associated with new well connections, expenditures for construction, third-party acquisitions and equity investments.

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Operating Statistics

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RISK FACTORS

        An investment in the notes is subject to a number of risks. You should carefully consider the risk factors included below and those in Item 1A. "Risk Factors" in our annual report on Form 10-K for the year ended December 31, 2009 and in our quarterly report on Form 10-Q for the quarter ended September 30, 2010, together with all of the other information included or incorporated by reference in this prospectus supplement. You should consider the following risk factors in evaluating this investment. If any of these risks materialize into actual events, our business, financial condition or results of operations could be adversely affected.

Risks Related to the Notes

We have a holding company structure in which our subsidiaries conduct our operations and own our operating assets.

        We are a holding company, and our subsidiaries conduct all of our operations and own all of our operating assets. We have no significant assets other than the partnership interests, stock and the other equity interests in our subsidiaries. As a result, our ability to make required payments on the notes depends on the performance of our subsidiaries and their ability to distribute funds to us. The ability of our subsidiaries to make distributions to us may be restricted by, among other things, our Amended and Restated Credit Agreement and applicable state business organization laws and other laws and regulations. If we are unable to obtain the funds necessary to pay the principal amount at maturity of the notes, or to repurchase the notes upon the occurrence of a change of control, we may be required to adopt one or more alternatives, such as a refinancing of the notes. We cannot assure you that we would be able to refinance the notes or obtain the funds to pay principal or interest on the notes.

Payment of principal and interest on the notes will be effectively subordinated to our senior secured debt to the extent of the value of the assets securing that debt and structurally subordinated to the liabilities of any of our subsidiaries that do not guarantee the notes.

        The notes are effectively subordinated to claims of our secured creditors and the subsidiary guarantees are effectively subordinated to the claims of our secured creditors as well as the secured creditors of our subsidiary guarantors. As of February 7, 2011, we and our subsidiary guarantors had $30.2 million in aggregate principal amount of secured indebtedness outstanding (excluding $27.4 million of outstanding letters of credit). Holders of our secured obligations, including obligations under our Amended and Restated Credit Agreement, will have claims that are prior to claims of the holders of the notes with respect to the assets securing those obligations. In the event of a liquidation, dissolution, reorganization, bankruptcy or any similar proceeding, our assets and those of our subsidiaries will be available to pay obligations on the notes and the guarantees only after holders of our senior secured debt have been paid the value of the assets securing such debt. Although all of our wholly-owned subsidiaries, other than MarkWest Energy Finance Corporation, the co-issuer of the notes, will initially guarantee the notes, in the future, under certain circumstances, the guarantees are subject to release and we may have subsidiaries that are not guarantors. In that case, the notes would be structurally subordinated to the claims of all creditors, including trade creditors and tort claimants, of our subsidiaries that are not guarantors. In the event of the liquidation, dissolution, reorganization, bankruptcy or similar proceeding of the business of a subsidiary that is not a guarantor, creditors of that subsidiary would generally have the right to be paid in full before any distribution is made to us or the holders of the notes. Accordingly, there may not be sufficient funds remaining to pay amounts due on all or any of the notes.

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We require a significant amount of cash to service our indebtedness. Our ability to generate cash depends on many factors beyond our control.

        Our ability to make payments on and to refinance our indebtedness, including the notes, and to fund planned capital expenditures depends on our ability to generate cash in the future. This, to a certain extent, is subject to general economic, financial, competitive, legislative, regulatory and other factors that are beyond our control.

        We cannot assure you that we will generate sufficient cash flow from operations or that future borrowings will be available to us under our Amended and Restated Credit Agreement or otherwise in an amount sufficient to enable us to pay our indebtedness, including these notes, or to fund our other liquidity needs. We may need to refinance all or a portion of our indebtedness, including the notes, on or before maturity. We cannot assure you that we will be able to refinance any of our indebtedness, including outstanding indebtedness pursuant to our Amended and Restated Credit Agreement and the notes, on commercially reasonable terms or at all.

We distribute all of our available cash to our unitholders and we are not required to accumulate cash for the purpose of meeting our future obligations to our noteholders, which may limit the cash available to service the notes.

        Subject to the limitations on restricted payments contained in the indenture governing the notes and in our Amended and Restated Credit Agreement and other indebtedness, we distribute all of our "available cash" each quarter to our limited partners and our general partner. "Available cash" is defined in our partnership agreement, and it generally means, for each fiscal quarter:

•

all cash and cash equivalents on hand at the end of the quarter (excluding cash at MarkWest Hydrocarbon);



•

less the amount of cash that our general partner determines in its reasonable discretion is necessary or appropriate to:



•

provide for the proper conduct of our business;



•

comply with applicable law, any of our debt instruments, or other agreements; or



•

provide funds for distributions to unitholders for any one or more of the next four quarters;



•

plus all cash and cash equivalents on hand on the date of determination of available cash for the quarter resulting from working capital borrowings made after the end of the quarter. Working capital borrowings are generally borrowings that are made under our Credit Facility and in all cases are used solely for working capital purposes or to pay distributions to partners.

        As a result, we do not expect to accumulate significant amounts of cash. Depending on the timing and amount of our cash distributions, these distributions could significantly reduce the cash available to us in subsequent periods to make payments on the notes.

We may not be able to fund a change of control offer.

        Upon the occurrence of certain change of control events, we will be required, subject to certain conditions, to offer to purchase all outstanding notes at a price equal to 101% of the principal amount thereof, plus accrued and unpaid interest thereon to the date of purchase. The holders of our outstanding senior notes have similar put rights. If a change of control event were to occur today, we would not have sufficient funds available to purchase all of the outstanding notes were they to be tendered in response to an offer made as a result of a change of control event. We cannot assure you that we will have sufficient funds available or that we will be permitted by our other debt instruments

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to fulfill these obligations upon a change of control event in the future. Furthermore, certain change of control events would constitute an event of default under our Credit Facility. Please read "Description of Notes—Repurchase at the Option of Holders—Change of Control."

Many of the covenants contained in the indenture will terminate if the notes are rated investment grade by both Standard & Poor's and Moody's and no default has occurred and is continuing.

        Many of the covenants in the indenture governing the notes will terminate if the notes are rated investment grade by both Standard & Poor's and Moody's provided at such time no default or event of default has occurred and is continuing. The covenants will restrict, among other things, our ability to pay dividends, incur debt, and to enter into certain other transactions. There can be no assurance that the notes will ever be rated investment grade. However, termination of these covenants would allow us to engage in certain transactions that would not be permitted while these covenants were in force, and the effects of any such transactions will be permitted to remain in place even if the notes are subsequently downgraded below investment grade. Please read "Description of Notes—Covenants—Covenant Termination."

The subsidiary guarantees could be deemed fraudulent conveyances under certain circumstances, and a court may try to subordinate or void the subsidiary guarantees.

        Under the federal bankruptcy laws and comparable provisions of state fraudulent transfer laws, a subsidiary guarantee could be voided, or claims in respect of a subsidiary guarantee could be subordinated to all other debts of that subsidiary guarantor if, among other things, the subsidiary guarantor, at the time it incurred the indebtedness evidenced by its subsidiary guarantee:

•

received less than reasonably equivalent value or fair consideration for the incurrence of such subsidiary guarantee; and



•

was insolvent or rendered insolvent by reason of such incurrence;



•

was engaged in a business or transaction for which the subsidiary guarantor's remaining assets constituted unreasonably small capital; or



•

intended to incur, or believed that it would incur, debts beyond its ability to pay such debts as they mature.

        In addition, any payment by that subsidiary guarantor pursuant to its subsidiary guarantee could be voided and required to be returned to the subsidiary guarantor, or to a fund for the benefit of the creditors of the subsidiary guarantor. The measures of insolvency for purposes of these fraudulent transfer laws will vary depending upon the law applied in any proceeding to determine whether a fraudulent transfer has occurred. Generally, however, a subsidiary guarantor would be considered insolvent if:

•

the sum of its debts, including contingent liabilities, was greater than the fair saleable value of all of its assets;



•

the present fair saleable value of its assets was less than the amount that would be required to pay its probable liability, including contingent liabilities, on its existing debts, as they become absolute and mature; or



•

it could not pay its debts as they become due.

Your ability to transfer the notes may be limited by the absence of a trading market.

        The notes will be new securities for which currently there is no trading market. Although the underwriter has informed us that it currently intends to make a market in the notes, it is not obligated

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to do so. In addition, it may discontinue any such market making at any time without notice. The liquidity of any market for the notes will depend on the number of holders of those notes, the interest of securities dealers in making a market in those notes and other factors. Accordingly, we cannot assure you as to the development or liquidity of any market for the notes. Historically, the market for noninvestment grade debt has been subject to disruptions that have caused substantial volatility in the prices of securities similar to the notes. We cannot assure you that the market, if any, for the notes will be free from similar disruptions. Any such disruption may adversely affect the noteholders' ability to transfer the notes.

Risks Related to our Ownership Structure

Our tax treatment depends on our status as a partnership for federal income tax purposes as well as our not being subject to a material amount of entity-level taxation by individual states. If the Internal Revenue Service were to treat us as a corporation for federal income tax purposes or we were to become subject to additional amounts of entity-level taxation for state tax purposes, then our cash available for payment of principal and interest on the notes would be substantially reduced.

        Although we do not believe based upon our current operations that we are so treated, and despite the fact that we are a limited partnership under Delaware law, it is possible in certain circumstances for a partnership such as ours to be treated as a corporation for federal income tax purposes. A change in our business (or a change in current law) could cause us to be treated as a corporation for federal income tax purposes or otherwise subject us to taxation as an entity.

        If we were treated as a corporation for federal income tax purposes, we would pay federal income tax on our taxable income at the corporate tax rate, which is currently a maximum of 35%, and would likely pay state income tax at varying rates. If we were required to pay tax on our taxable income, our anticipated cash flow could be materially reduced, which could materially adversely affect our ability to make payments on the notes and our other debt obligations.

        Current law may change so as to cause us to be treated as a corporation for federal income tax purposes or otherwise subject us to entity-level taxation. At the federal level, legislation has recently been considered by members of Congress that would have eliminated partnership tax treatment for certain publicly traded partnerships. Although it does not appear that the legislation considered would have affected our tax treatment, we are unable to predict whether any of these changes, or other proposals, will be reconsidered or will ultimately be enacted. Any such changes could negatively impact the amount of cash available for payment on the notes and on our other debt obligations. At the state level, because of widespread state budget deficits and other reasons, several states are evaluating ways to subject partnerships to entity-level taxation through the imposition of state income, franchise and other forms of taxation. For example, we are required to pay an entity-level tax on the portion of our gross income apportioned to Texas. Imposition of such a tax on us by any other state will reduce the cash available for payment on the notes and on our other debt obligations.

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USE OF PROCEEDS

        We estimate the net proceeds to us from this offering to be approximately $296.0 million, after deducting estimated fees and expenses payable by us (including underwriting discounts and commissions). We intend to use the net proceeds from this offering and, if necessary, cash on hand or borrowings under the Credit Facility to fund our pending tender offer and consent solicitation respecting our 2016 Notes described under "Summary—Recent Developments—Tender Offer for 2016 Notes." Assuming that all of our existing 2016 Notes are tendered for repurchase on February 23, 2011, we will use all of the net proceeds for such purpose (including accrued and unpaid interest and the consent fees). In the event the tender offer is not consummated or is not fully subscribed, any remaining net proceeds will be used to repay borrowings outstanding under the Credit Facility, to fund our tender offer for the 2018 Notes or to provide additional working capital for general partnership purposes.

        As of February 7, 2011, the outstanding balance of the Credit Facility, which matures on July 1, 2015, was approximately $30.2 million (excluding $27.4 million of outstanding letters of credit), and the weighted average interest rate of the Credit Facility was 5.0%.

        The underwriter or its affiliates are holders of our 2016 Notes and accordingly may receive a portion of the proceeds of this offering in the tender offer for such notes described under "Summary—Recent Developments—Tender Offer for 2016 Notes." Additionally, an affiliate of the underwriter is a lender under the Credit Facility and may receive a portion of the proceeds of this offering in the event the tender offer is not consummated or is not fully subscribed and net proceeds are used to repay borrowings under the Credit Facility.

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CAPITALIZATION

        The following table sets forth our consolidated cash and cash equivalents and our consolidated capitalization as of September 30, 2010:

•

on an actual basis;



•

on an as adjusted basis to give effect to: (1) our public offering of $500 million in aggregate principal amount of our 6.75% senior notes due 2020 completed in November 2010 and the application of the net proceeds therefrom to fund the retirement of our 6.875% senior notes due 2014 and the repayment of borrowings under our Credit Facility; and (2) our public offering of 3,450,000 common units in January 2011 and the use of approximately $138 million in net proceeds therefrom, cash on hand and borrowings under our Credit Facility to fund the EQT Transaction; and



•

on an as further adjusted basis to give effect to the issuance of the notes in this offering and the application of the net proceeds of this offering in the manner described under "Use of Proceeds."

        This table is derived from, should be read together with, and is qualified in its entirety by reference to the information contained in "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our unaudited consolidated financial statements, including the related notes, contained in our quarterly report on Form 10-Q for the quarter ended September 30, 2010, which is incorporated by reference in this prospectus supplement.

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RATIO OF EARNINGS TO FIXED CHARGES

        The table below sets forth the ratios of earnings to fixed charges for us for the periods indicated. The ratio of earnings to fixed charges is calculated as earnings divided by fixed charges. Earnings consist of pre-tax income from continuing operations before fixed charges. Fixed charges consist of interest expense and capitalized interest, including the gain or loss on interest rate swaps and amortization of premiums, discounts and capitalized expenses related to indebtedness. Fixed charges also include an estimate of the interest within rental expense.