16. Long-Term Debt

Debt is summarized below (in thousands):

	December 31, 2013		December 31, 2012

Credit Facility
Revolving credit facility, variable interest, due September 2017(1)	$	—	$	—
Senior Notes
2018 Senior Notes, 8.75% interest, net of discount of $0 and $109, respectively, issued April and May 2008 and repaid in February 2013		—		81,003
2020 Senior Notes, 6.75% interest, issued November 2010 and due November 2020		500,000		500,000
2021 Senior Notes, 6.5% interest, net of discount of $474 and $826, respectively, issued February and March 2011 and due August 2021		324,526		499,174
2022 Senior Notes, 6.25% interest, issued October 2011 and due June 2022		455,000		700,000
2023A Senior Notes, 5.5% interest, net of discount of $6,455 and $7,126, respectively, issued August 2012 and due February 2023		743,545		742,874
2023B Senior Notes, 4.5% interest, issued January 2013 and due July 2023		1,000,000		—


Total long-term debt	$	3,023,071	$	2,523,051

(1): Applicable interest rate was 4.75% at December 31, 2013.

Credit Facility

On June 29, 2012, the Partnership amended its Credit Facility to increase the borrowing capacity to $1.2 billion and retained the existing accordion option, providing for potential future increases of up to an aggregate of $250.0 million upon the satisfaction of certain requirements. The term of the Credit Facility was extended one year and now matures on September 7, 2017. The Partnership incurred approximately $0, $2.5 million and $2.1 million of deferred financing costs associated with modifications of the Credit Facility during the years ended December 31, 2013, 2012 and 2011, respectively.

The borrowings under the Credit Facility bear interest at a variable interest rate, plus basis points. The variable interest rate is based either on the London interbank market rate ("LIBO Rate Loans") or the higher of (a) the prime rate set by the Facility's administrative agent, (b) the Federal Funds Rate plus 0.50% and (c) the rate for LIBO Rate Loans for a one month interest period plus 1% ("Alternate Base Rate Loans"). The basis points correspond to the Partnership's Total Leverage Ratio (which is the ratio of the Partnership's consolidated funded debt to the Partnership's adjusted consolidated EBITDA), ranging from 0.75% to 1.75% for Alternate Base Rate Loans and from 1.75% to 2.75% for LIBO Rate Loans. The Partnership may utilize up to $150.0 million of the Credit Facility for the issuance of letters of credit and $10.0 million for shorter-term swingline loans.

Under the provisions of the Credit Facility and indentures, the Partnership is subject to a number of restrictions and covenants. The Credit Facility and indentures place limits on the ability of the Partnership and its restricted subsidiaries to incur additional indebtedness; declare or pay dividends or distributions or redeem, repurchase or retire equity interests or subordinated indebtedness; make investments; incur liens; create any consensual limitation on the ability of the Partnership's restricted subsidiaries to pay dividends or distributions, make loans or transfer property to the Partnership; engage in transactions with the Partnership's affiliates; sell assets, including equity interests of the Partnership's subsidiaries; make any payment on or with respect to or purchase, redeem, defease or otherwise acquire or retire for value any subordinated obligation or guarantor subordination obligation (except principal and interest at maturity); and consolidate, merge or transfer assets. The Credit Facility also limits the Partnership's ability to enter into transactions with parties that require margin calls under certain derivative instruments. Under the Credit Facility, neither the Partnership nor the bank can require margin calls for outstanding derivative positions.

Significant financial covenants under the Credit Facility include the Interest Coverage Ratio (as defined in the Credit Facility), which must be greater than 2.75 to 1.0 and the Total Leverage Ratio (as defined in the Credit Facility), which must be less than 5.5 to 1.0 in accordance with an amendment executed in December 2013. The maximum permissible Total Leverage Ratio will be 5.25 to 1.0 beginning on January 1, 2015. As of December 31, 2013, the Partnership was in compliance with these covenants. These covenants are used to calculate the available borrowing capacity on a quarterly basis. The Credit Facility is guaranteed by and collateralized by substantially all assets of the Partnership's wholly- owned subsidiaries, other than MarkWest Liberty Midstream and its subsidiaries. As of December 31, 2013, the Partnership had no borrowings outstanding and $11.3 million of letters of credit outstanding under the Credit Facility, leaving approximately $1,188.7 million available for borrowing of which approximately $704.8 million was available for borrowing based on financial covenant requirements. Additionally, the full amount of unused capacity is available for borrowing on a short-term basis to provide financial flexibility within a given fiscal quarter.

Senior Notes

2018 Senior Notes. In April 2008, the partnership and its wholly-owned subsidiary, MarkWest Energy Finance Corporation (the "Issuers") completed a private placement, subsequently registered, of $400.0 million in aggregate principal amount of 8.75% senior unsecured notes to qualified institutional buyers under Rule 144A. In May 2008, the Partnership completed the placement of an additional $100.0 million pursuant to the indenture to the 2018 Senior Notes. The notes issued in the April 2008 and May 2008 offerings are treated as a single class of debt under this same indenture. Approximately $253.3 million and $165.6 million of the 2018 Senior Notes were redeemed in the fourth quarter and first quarter of 2011, respectfully. The Partnership received combined proceeds of approximately $488.5 million, after including initial purchasers' premium and deducting the underwriting fees and the other expenses of the offering. The 2018 Senior Notes were repaid in February 2013.

2020 Senior Notes. In November 2010, the Issuers completed a public offering of $500.0 million in aggregate principal amount of 6.75% senior unsecured notes. The 2020 Senior Notes mature on November 1, 2020 and interest is payable semi-annually in arrears on May 1 and November 1. The Partnership received proceeds of approximately $490.3 million after deducting the underwriting fees and the other third-party expenses associated with the offering.

2021 Senior Notes. On February 24, 2011, the Issuers completed a public offering of $300.0 million in aggregate principal amount of 6.5% senior unsecured notes, which were issued at par. On March 10, 2011, the Issuers completed a follow-on public offering of an additional $200.0 million in aggregate principal amount of 2021 Senior Notes, which were issued at 99.5% of par and are treated as a single class of debt securities under the same indenture as the 2021 Senior Notes issued on February 24, 2011. The 2021 Senior Notes mature in August 2021 and interest is payable semi-annually in arrears on February 15 and August 15. The Partnership received aggregate net proceeds of approximately $492.4 million from the 2021 Senior Notes offerings after deducting the underwriting fees and other third-party expenses associated with the offerings. The Partnership repaid approximately $175.0 million of the 2021 Senior Notes in February 2013.

2022 Senior Notes. On November 3, 2011, the Issuers completed a public offering of $700.0 million in aggregate principal amount of 6.25% senior unsecured notes due June 2022. Interest on the 2022 Notes is payable semi-annually in arrears on June 15 and December 15, commencing June 15, 2012. The Partnership received aggregate net proceeds of approximately $688.5 million from the 2022 Senior Notes offerings, after deducting the underwriting fees and other third-party expenses. The Partnership repaid approximately $245.0 million of the 2021 Senior Notes in February 2013.

2023A Senior Notes. On August 10, 2012, the Issuers completed a public offering of $750.0 million in aggregate principal amount of 5.5% senior unsecured notes due February 2023. Interest on the 2023A Senior Notes is payable semi-annually in arrears on February 15 and August 15, commencing February 15, 2013. The Partnership received aggregate net proceeds of approximately $730.2 million from the 2023A Senior Notes offerings, after deducting the underwriting fees and other third-party expenses.

2023B Senior Notes. In January 2013, the Partnership completed a public offering for $1.0 billion in aggregate principal amount of 4.5% senior unsecured notes due July 2023. Interest on the 2023B Senior Notes is payable semi-annually in arrears on January 15 and July 15, commencing July 15, 2013. The Partnership received aggregate net proceeds of approximately $986.0 million from the 2023B Senior Notes offerings, after deducting underwriters' and third-party expenses.

The proceeds from the issuance of the 2021 and 2022 Senior Notes were used to redeem $275.0 million in aggregate principal amount of 2016 Senior Notes and $419.0 million in aggregate principal amount of 2018 Senior Notes and to provide additional working capital for general partnership purposes. The proceeds from the issuance of the 2020 Senior Notes were used to redeem the 2014 Senior Notes, repay the Credit Facility and to provide additional working capital for general partnership purposes. The proceeds from the issuance of the 2023A Senior Notes were used to repay borrowings under our Credit Facility, fund capital expenditures and provide additional working capital for general partnership purposes. The proceeds from the 2023B Senior Notes were used to repurchase the $81.1 million of the 2018 Senior Notes, approximately $175.0 million of the 2021 Senior Notes and approximately $245.0 million of the 2022 Senior Notes and to fund capital expenditures and provide general working capital.

The Partnership recorded a total pre-tax loss during 2013 of approximately $38.5 million related to repurchases of the $81.1 million of the 2018 Senior Notes, approximately $175.0 million of the 2021 Senior Notes and approximately $245.0 million of the 2022 Senior Notes. The pre-tax loss consisted of approximately $7.0 million in the first quarter of 2013 related to the non-cash write-off of the unamortized discount and deferred finance costs and approximately $31.5 million related to the payment of redemption premiums. The Partnership recorded a total pre-tax loss of approximately $79.0 million during 2011 related to the redemption of the 2016 Senior Notes and 2018 Senior Notes. The pre-tax loss consisted of approximately $7.6 million related to the non-cash write-off of the unamortized discount and deferred finance costs and approximately $71.4 million related to the payment of tender premiums and third party expenses. The losses were recorded in Loss on redemption of debt in the accompanying Consolidated Statements of Operations.

The Issuers have no independent operating assets or operations. All subsidiaries that are owned 100% by the Partnership, other than MarkWest Energy Finance Corporation and MarkWest Liberty Midstream and its subsidiaries, guarantee the Senior Notes, jointly and severally and fully and unconditionally, subject to certain customary release provisions, including:

(1)

in connection with any sale or other disposition of all or substantially all of a subsidiary guarantor's assets (including by way of merger or consolidation) to a third party, if the transaction does not violate the asset sale provisions of the indentures;

(2)

in connection with any sale or other disposition of the equity interests of a subsidiary guarantor to a third party, if the transaction does not violate the asset sale provisions of the indentures and the subsidiary guarantor is no longer a restricted subsidiary of the Partnership;

(3)

if the Partnership designates any subsidiary guarantor as an unrestricted subsidiary under the indentures;

(4)

upon legal defeasance, covenant defeasance or satisfaction and discharge of the indentures; and

(5)

at such time as a subsidiary guarantor no longer guarantees any other indebtedness of the Issuers or MarkWest Energy Operating Company, L.L.C. ("Operating Company") and, in the case of Operating Company, Operating Company is not an obligor of any indebtedness under the Credit Facility.

Subsidiaries that are not 100% owned by the Partnership do not guarantee the Senior Notes (see Note 25 for required consolidating financial information). The Senior Notes are senior unsecured obligations equal in right of payment with all of the Partnership's existing and future senior debt. The Senior Notes are senior in right of payment to all of the Partnership's future subordinated debt but effectively junior in right of payment to its secured debt to the extent of the assets securing the debt, including the Partnership's obligations in respect of the Credit Facility.

The indentures governing the Senior Notes limit the activity of the Partnership and the restricted subsidiaries identified in the indentures. Subject to compliance with certain covenants, the Partnership may issue additional notes from time to time under the indentures. If at any time the Senior Notes are rated investment grade by both Moody's Investors Service, Inc. and Standard & Poor's Rating Services and no default (as defined in the indentures) has occurred and is continuing, many of such covenants will terminate, in which case the Partnership and its subsidiaries will cease to be subject to such terminated covenants.

As of December 31, 2013, there are no minimum principal payments on the Senior Notes due during the next five years.