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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">UNITED STATES</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">SECURITIES AND EXCHANGE COMMISSION</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Washington, D.C. 20549</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">FORM&nbsp;8-K</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">CURRENT REPORT</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">PURSUANT TO SECTION&nbsp;13 OR 15(d)&nbsp;OF</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">THE SECURITIES EXCHANGE ACT OF 1934</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date of Report (Date of earliest event reported):<b> August&nbsp;7, 2013</b></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">MARKWEST ENERGY PARTNERS, L.P.</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Exact name of registrant as specified in its charter)</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Delaware</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(State or other jurisdiction of</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">001-31239</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Commission File Number)</font></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">27-0005456</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Identification Number)</font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">1515 Arapahoe Street, Tower 1, Suite&nbsp;1600, Denver CO 80202</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Address of principal executive offices)</font></p>
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<p style="margin:0in 0in .0001pt;text-indent:110.0pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Registrant&#146;s telephone number, including area code: <b>303-925-9200</b></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Not Applicable.</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Former name or former address, if changed since last report.)</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Check the appropriate box below if the Form&nbsp;8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):</font></p>
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<p style="margin:0in 0in .0001pt .25in;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font><font size="2" style="font-size:10.0pt;">&#160;&#160;&#160; Written Communications pursuant to Rule&nbsp;425 under the Securities Act (17 CFR 230.425)</font></p>
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<p style="margin:0in 0in .0001pt .25in;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font><font size="2" style="font-size:10.0pt;">&#160;&#160;&#160; Soliciting material pursuant to Rule&nbsp;14a-12 under the Exchange Act (17 CFR 240.14a-12)</font></p>
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<p style="margin:0in 0in .0001pt .5in;text-indent:-.25in;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font><font size="2" style="font-size:10.0pt;">&#160;&#160;&#160; </font><font size="2" style="font-size:10.0pt;">Pre-Commencement communications pursuant to Rule&nbsp;14d-2(b)&nbsp;under the Exchange Act (17 CFR 240.14d-2(b))</font></p>
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<p style="margin:0in 0in .0001pt .5in;text-indent:-.25in;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font><font size="2" style="font-size:10.0pt;">&#160;&#160;&#160; </font><font size="2" style="font-size:10.0pt;">Pre-Commencement communications pursuant to Rule&nbsp;13e-4(c)&nbsp;under the Exchange Act (17 CFR 240.13e-4(c))</font></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">ITEM 2.02. Results of Operations and Financial Condition</font></b></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">On August&nbsp;7, 2013, MarkWest Energy Partners, L.P. (the &#147;Partnership&#148;) announced its consolidated financial results for the three and six months ended June&nbsp;30, 2013.&nbsp; A copy of the Partnership&#146;s earnings release is furnished as Exhibit&nbsp;99.1 to this Current Report on Form&nbsp;8-K.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">This information shall not be deemed &#147;filed&#148; for purposes of Section&nbsp;18 of the Securities Exchange Act of 1934, as amended (the &#147;Exchange Act&#148;), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The earnings release furnished with this Current Report on Form&nbsp;8-K utilizes the Non-GAAP financial measures of Distributable Cash Flow (&#147;DCF&#148;), Adjusted EBITDA, and Operating Income before Items Not Allocated to Segments.&nbsp; In general, we define DCF as net income (loss) adjusted for (i)&nbsp;depreciation, amortization, impairment, and other non-cash expense; (ii)&nbsp;amortization of deferred financing costs and discount; (iii)&nbsp;loss on redemption of debt net of current tax benefit; (iv)&nbsp;non-cash (earnings) loss from unconsolidated affiliates; (v)&nbsp;distributions from (contributions to) unconsolidated affiliates (net of affiliate growth capital expenditures); (vi)&nbsp;non-cash compensation expense; (vii)&nbsp;non-cash derivative activity; (viii)&nbsp;losses (gains) on the disposal of property, plant, and equipment (PP&amp;E) and unconsolidated affiliates; (ix)&nbsp;provision for deferred income taxes; (x)&nbsp;cash adjustments for non-controlling interest in consolidated subsidiaries; (xi)&nbsp;revenue deferral adjustment; (xii)&nbsp;losses (gains) relating to other miscellaneous non-cash amounts affecting net income for the period; and (xiii)&nbsp;maintenance capital expenditures net of joint venture partner contributions. We define Adjusted EBITDA as net income (loss) adjusted for (i)&nbsp;depreciation, amortization, impairment, and other non-cash expense; (ii)&nbsp;interest expense; (iii)&nbsp;amortization of deferred financing costs; (iv)&nbsp;loss on redemption of debt; (v)&nbsp;losses (gains) on the disposal of PP&amp;E and unconsolidated affiliates; (vi)&nbsp;non-cash derivative activity; (vii)&nbsp;non-cash compensation expense; (viii)&nbsp;provision for income taxes; (ix)&nbsp;adjustments for cash flow from unconsolidated affiliates; (x)&nbsp;adjustment related to non-guarantor, consolidated subsidiaries; and (xi)&nbsp;losses (gains) relating to other miscellaneous non-cash amounts affecting net income for the period. We generally define Operating Income before Items Not Allocated to Segments as (i)&nbsp;revenue, excluding derivative gains and losses and adjusted for certain revenue deferral adjustments less;&nbsp;(ii)&nbsp;purchased product costs, excluding derivative gains and losses&nbsp;less; (iii)&nbsp;facility expenses, adjusted for certain non-cash items not allocated to segments and certain interest payments allocable to the segments less; ( iv) the portion allocable to non-controlling interests.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">DCF is a financial performance measure used by management as a key component in the determination of cash distributions paid to unitholders.&nbsp; We believe distributable cash flow is an important financial measure for unitholders as an indicator of cash return on investment and to evaluate whether the Partnership is generating sufficient cash flow to support quarterly distributions.&nbsp; In addition, DCF is commonly used by the investment community because the market value of publicly traded partnerships is based, in part, on distributable cash flow and cash distributions paid to unitholders.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">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&#146;s ongoing business operations.&nbsp; 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.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Operating Income before Items Not Allocable to Segments is a financial performance measure used by management to evaluate the performance of the operating segments in order to make decisions and allocate resources.</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><i><font size="2" face="Times New Roman" style="font-size:10.0pt;font-style:italic;">Cautionary Statements</font></i></p>
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<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">This filing includes &#147;forward-looking statements.&#148;&#160; All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements.&#160; Actual results could vary significantly from those expressed or implied in such statements and are subject to a number of risks and uncertainties.&#160; Although we believe that the expectations reflected in the forward-looking statements are reasonable, we can give no assurance that such expectations will prove to be correct.&#160; The forward-looking statements involve risks and uncertainties that affect our operations, financial performance, and other factors as discussed in our filings with the Securities and Exchange Commission.&#160; Among the factors that could cause results to differ materially are those risks discussed in the periodic reports we file with the SEC, including our Annual Report on Form&nbsp;10-K for the year ended December</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">2<a name="PB_2_223555_7056"></a></font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">31, 2012 and our Quarterly Report on Form&nbsp;10-Q for the quarter ended June&nbsp;30, 2013.&#160; You are urged to carefully review and consider the cautionary statements and other disclosures made in those filings, specifically those under the heading &#147;Risk Factors.&#148;&#160; We do not undertake any duty to update any forward-looking statement except as required by law.</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">3<a name="PB_3_223620_5335"></a></font></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">ITEM 9.01.&#160; Financial Statements and Exhibits.</font></b></p>
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<p style="margin:0in 0in .0001pt .5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(d)&#160;&#160; Exhibits.</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Press release dated August&nbsp;7, 2013,   reporting 2013 2</font><font size="1" style="font-size:6.5pt;position:relative;top:-3.0pt;">nd</font><font size="2" style="font-size:10.0pt;">&nbsp;quarter financial results</font><b><font size="2" style="font-size:10.0pt;font-weight:bold;">.</font></b></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">SIGNATURE</font></b></p>
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<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">MARKWEST   ENERGY PARTNERS, L.P.</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt 1.4in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Registrant)</font></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">MarkWest Energy GP, L.L.C.,</font></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Its General Partner</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date:   August&nbsp;7, 2013</font></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">/s/ NANCY K. BUESE</font></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Nancy K. Buese <br>    <i>Senior Vice President and Chief Financial   Officer</i></font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">5<a name="PB_5_225246_7748"></a></font></p>
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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
PURSUANT TO SECTION 13 OR 15(d) OF
THE SECURITIES EXCHANGE ACT OF 1934
Date of Report (Date of earliest event reported):
August 7, 2013
MARKWEST ENERGY PARTNERS, L.P.
(Exact name of registrant as specified in its charter)
Delaware
(State or other jurisdiction of
incorporation or organization)
001-31239
(Commission File Number)
27-0005456
(I.R.S. Employer
Identification Number)
1515 Arapahoe Street, Tower 1, Suite 1600, Denver CO 80202
(Address of principal executive offices)
Registrant's telephone number, including area code:
303-925-9200
Not Applicable.
(Former name or former address, if changed since last report.)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):
o
Written Communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
o
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
o
Pre-Commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
o
Pre-Commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
ITEM 2.02. Results of Operations and Financial Condition
On August 7, 2013, MarkWest Energy Partners, L.P. (the "Partnership") announced its consolidated financial results for the three and six months ended June 30, 2013.  A copy of the Partnership's earnings release is furnished as Exhibit 99.1 to this Current Report on Form 8-K.
This information shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.
The earnings release furnished with this Current Report on Form 8-K utilizes the Non-GAAP financial measures of Distributable Cash Flow ("DCF"), Adjusted EBITDA, and Operating Income before Items Not Allocated to Segments.  In general, we define DCF as net income (loss) adjusted for (i) depreciation, amortization, impairment, and other non-cash expense; (ii) amortization of deferred financing costs and discount; (iii) loss on redemption of debt net of current tax benefit; (iv) non-cash (earnings) loss from unconsolidated affiliates; (v) distributions from (contributions to) unconsolidated affiliates (net of affiliate growth capital expenditures); (vi) non-cash compensation expense; (vii) non-cash derivative activity; (viii) losses (gains) on the disposal of property, plant, and equipment (PP&E) and unconsolidated affiliates; (ix) provision for deferred income taxes; (x) cash adjustments for non-controlling interest in consolidated subsidiaries; (xi) revenue deferral adjustment; (xii) losses (gains) relating to other miscellaneous non-cash amounts affecting net income for the period; and (xiii) maintenance capital expenditures net of joint venture partner contributions. We define Adjusted EBITDA as net income (loss) adjusted for (i) depreciation, amortization, impairment, and other non-cash expense; (ii) interest expense; (iii) amortization of deferred financing costs; (iv) loss on redemption of debt; (v) losses (gains) on the disposal of PP&E and unconsolidated affiliates; (vi) non-cash derivative activity; (vii) non-cash compensation expense; (viii) provision for income taxes; (ix) adjustments for cash flow from unconsolidated affiliates; (x) adjustment related to non-guarantor, consolidated subsidiaries; and (xi) losses (gains) relating to other miscellaneous non-cash amounts affecting net income for the period. We generally define Operating Income before Items Not Allocated to Segments as (i) revenue, excluding derivative gains and losses and adjusted for certain revenue deferral adjustments less; (ii) purchased product costs, excluding derivative gains and losses less; (iii) facility expenses, adjusted for certain non-cash items not allocated to segments and certain interest payments allocable to the segments less; ( iv) the portion allocable to non-controlling interests.
DCF is a financial performance measure used by management as a key component in the determination of cash distributions paid to unitholders.  We believe distributable cash flow is an important financial measure for unitholders as an indicator of cash return on investment and to evaluate whether the Partnership is generating sufficient cash flow to support quarterly distributions.  In addition, DCF is commonly used by the investment community because the market value of publicly traded partnerships is based, in part, on distributable cash flow and cash distributions paid to unitholders.
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.
Operating Income before Items Not Allocable to Segments is a financial performance measure used by management to evaluate the performance of the operating segments in order to make decisions and allocate resources.
Cautionary Statements
This filing includes "forward-looking statements."  All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements.  Actual results could vary significantly from those expressed or implied in such statements and are subject to a number of risks and uncertainties.  Although we believe that the expectations reflected in the forward-looking statements are reasonable, we can give no assurance that such expectations will prove to be correct.  The forward-looking statements involve risks and uncertainties that affect our operations, financial performance, and other factors as discussed in our filings with the Securities and Exchange Commission.  Among the factors that could cause results to differ materially are those risks discussed in the periodic reports we file with the SEC, including our Annual Report on Form 10-K for the year ended December
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31, 2012 and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2013.  You are urged to carefully review and consider the cautionary statements and other disclosures made in those filings, specifically those under the heading "Risk Factors."  We do not undertake any duty to update any forward-looking statement except as required by law.
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ITEM 9.01.  Financial Statements and Exhibits.
(d)   Exhibits.
Exhibit No.
Description of Exhibit
99.1
Press release dated August 7, 2013,   reporting 2013 2
nd
quarter financial results
.
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SIGNATURE
Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.
MARKWEST   ENERGY PARTNERS, L.P.
(Registrant)
By:
MarkWest Energy GP, L.L.C.,
Its General Partner
Date:   August 7, 2013
By:
/s/ NANCY K. BUESE
Nancy K. Buese
Senior Vice President and Chief Financial   Officer
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