EX-99.(c)(6)

Project Intrepid

April 30, 2013

EXHIBIT (c)(6)

DRAFT

Preliminary and Subject

to Change

Preliminary Materials Prepared for the Conflicts Committee

of the Board of Directors of Crestwood Gas Services GP LLC

DRAFT

These materials have been prepared by Evercore Group L.L.C. (“Evercore”) for the Conflicts Committee of the Board of Directors (the “Conflicts Committee”) of

Crestwood Gas Services GP LLC (the “Company”), the general partner of Crestwood Midstream Partners LP (the “Partnership”), to whom such materials are

directly addressed and delivered and may not be used or relied upon for any purpose other than as specifically contemplated by a written agreement with Evercore. These

materials are based on information provided by or on behalf of the Partnership and/or other potential transaction participants, from public sources or otherwise

reviewed by Evercore. Evercore assumes no responsibility for independent investigation or verification of such information and has relied on such information being

complete and accurate in all material respects. To the extent such information includes estimates and forecasts of future financial performance prepared by or reviewed

with the management of the Partnership and/or other potential transaction participants or obtained from public sources, Evercore has assumed that such estimates and

forecasts have been reasonably prepared on bases reflecting the best currently available estimates and judgments of such management (or, with respect to estimates and

forecasts obtained from public sources, represent reasonable estimates). No representation or warranty, express or implied, is made as to the accuracy or completeness of

such information and nothing contained herein is, or shall be relied upon as, a representation, whether as to the past, the present or the future. These materials were

designed for use by specific persons familiar with the business and affairs of the Partnership. These materials are not intended to provide the sole basis for evaluating,

and should not be considered a recommendation with respect to, any transaction or other matter. These materials have been developed by and are proprietary to Evercore

and were prepared for the benefit and internal use of the Conflicts Committee.

These materials were compiled on a confidential basis for use by the Conflicts Committee in evaluating the potential transaction described herein and not with a view to

public disclosure or filing thereof under state or federal securities laws, and may not be reproduced, disseminated, quoted or referred to, in whole or in part, without the

prior written consent of Evercore.

These materials do not constitute an offer or solicitation to sell or purchase any securities and are not a commitment by Evercore (or any affiliate) to provide or arrange

any financing for any transaction or to purchase any security in connection therewith. Evercore assumes no obligation to update or otherwise revise these materials.

These materials may not reflect information known to other professionals in other business areas of Evercore and its affiliates.

Evercore and its affiliates do not provide legal, accounting or tax advice. Accordingly, any statements contained herein as to tax matters were neither written nor

intended by Evercore or its affiliates to be used and cannot be used by any taxpayer for the purpose of avoiding tax penalties that may be imposed on such taxpayer.

Each person should seek legal, accounting and tax advice based on his, her or its particular circumstances from independent advisors regarding the impact of the

transactions or matters described herein.

Confidential

DRAFT

Market Value Weighted Average Current Yield and Exchange Ratio Calculation

Project Intrepid

CMLP

NRGM

Unit Price (as of 04/29/2013)

$23.76

$25.26

Current Distribution per Unit

$2.04

$1.58

Current Yield

8.6%

6.3%

Market Value

$1,451.0

$2,169.9

% of Combined Market Value

40.1%

59.9%

Market Value Weighted Average Current Yield

7.2%

20-Day VWAP (as of 04/29/2013)

$24.49

Offer Premium to CMLP's 20-Day VWAP

5.0%

Offer Price per CMLP Unit

$25.71

NRGM 20-Day VWAP

$23.81

CMLP / NRGM Exchange Ratio

1.080x

($ in millions, except per unit amounts)

Confidential

DRAFT

Project Intrepid

CMLP Management Financial Projections / NRGM Management Financial Projections

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield

$24.11

$25.05

$27.56

$30.32

$33.35

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.0%

7.9%

8.0%

7.7%

7.2%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

CMLP Management Sensitivity Case / NRGM Management Financial Projections

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.04

$2.08

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield

$23.76

$24.20

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.89

$1.98

$2.06

$2.10

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.1%

8.0%

8.4%

8.7%

Incremental GP/IDR Cash Flow Created

($0.8)

($1.8)

$5.5

$13.0

$15.3

CMLP Management Financial Projections / NRGM Management Sensitivity Case

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield

$24.11

$25.05

$27.56

$30.32

$33.35

Pro Forma Distribution per CMLP Unitholder

$1.93

$2.12

$2.29

$2.47

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.0%

7.7%

7.6%

7.4%

Incremental GP/IDR Cash Flow Created

($0.6)

$4.5

$16.9

$28.5

$39.8

CMLP Management Sensitivity Case / NRGM Management Sensitivity Case

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.04

$2.08

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield

$23.76

$24.20

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.85

$1.91

$2.00

$2.08

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.1%

7.8%

8.0%

8.4%

8.6%

Incremental GP/IDR Cash Flow Created

$1.0

($1.2)

$6.2

$19.8

$30.2

Summary Pro Forma Impact – Original – 1.080x Exchange Ratio as of April 29, 2013

($ in millions, except per unit amounts)

Confidential

DRAFT

($ in millions, except per unit amounts)

Project Intrepid

CMLP Management Financial Projections / NRGM Management Financial Projections (Including 100% of $25.0 million Cash Payment)

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $0.73 per Unit Cash Consideration)

$23.38

$24.32

$26.83

$29.58

$32.61

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.3%

8.2%

7.9%

7.4%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

CMLP Management Sensitivity Case / NRGM Management Financial Projections (Including 100% of $25.0 million Cash Payment)

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.04

$2.08

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $0.73 per Unit Cash Consideration)

$23.03

$23.47

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.89

$1.98

$2.06

$2.10

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.4%

8.2%

8.6%

9.0%

Incremental GP/IDR Cash Flow Created

($0.8)

($1.8)

$5.5

$13.0

$15.3

CMLP Management Financial Projections / NRGM Management Sensitivity Case (Including 100% of $25.0 million Cash Payment)

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $0.73 per Unit Cash Consideration)

$23.38

$24.32

$26.83

$29.58

$32.61

Pro Forma Distribution per CMLP Unitholder

$1.93

$2.12

$2.29

$2.47

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.3%

8.0%

7.9%

7.8%

7.6%

Incremental GP/IDR Cash Flow Created

($0.6)

$4.5

$16.9

$28.5

$39.8

CMLP Management Sensitivity Case / NRGM Management Sensitivity Case (Including 100% of $25.0 million Cash Payment)

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

Standalone Distribution per CMLP Unitholder

$2.04

$2.08

CMLP Current Yield

8.6%

CMLP

Standalone

Projected

Unit

Price

Current

Yield

(Less

$0.73

per

Unit

Cash

Consideration)

$23.03

$23.47

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.85

$1.91

$2.00

$2.08

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.4%

8.0%

8.3%

8.7%

8.9%

Incremental GP/IDR Cash Flow Created

$1.0

($1.2)

$6.2

$19.8

$30.2

Summary Pro Forma Impact – Including 100% of $25.0 Million Payment to CMLP

Unaffiliated Unitholders ($0.73 per Unit)

Confidential

DRAFT

Project Intrepid

Summary Pro Forma Impact – Base Case Incremental GP IDR Calculation ($ in millions)

For the Quarter Ending

For the Years Ending December 31,

9/30/13E

12/31/13E

2013E

2014E

2015E

2016E

2017E

NRGM GP/IDR Cash Flow Standalone

$3.0

$3.4

$11.2

$20.2

$26.8

$33.4

$36.6

CMLP GP/IDR Cash Flow Standalone

5.7

6.2

22.2

30.3

43.4

57.7

73.5

Total Combined GP/IDR Cash Flows Standalone

$8.7

$9.6

$33.3

$50.5

$70.1

$91.1

$110.1

Pro Forma NRGM GP/IDR Cash Flow

$8.0

$31.0

$55.3

$86.2

$110.3

$125.7

Incremental Combined GP/IDR Cash Flow Created

($0.7)

($1.6)

(2.4)

$4.8

$16.1

$19.3

$15.6

Equity Cost of Capital Based on CAPM

PV @ 8.0% of Incremental Combined GP/IDR Cash Flow Created

$42.5

PV @ 8.5% of Incremental Combined GP/IDR Cash Flow Created

41.9

PV @ 9.0% of Incremental Combined GP/IDR Cash Flow Created

41.4

PV @ 9.5% of Incremental Combined GP/IDR Cash Flow Created

40.8

PV @ 10.0% of Incremental Combined GP/IDR Cash Flow Created

40.3

Equity Cost of Capital Based on Total Expected Market Return

PV @ 13.0% of Incremental Combined GP/IDR Cash Flow Created

$37.2

PV @ 13.5% of Incremental Combined GP/IDR Cash Flow Created

36.7

PV @ 14.0% of Incremental Combined GP/IDR Cash Flow Created

36.3

PV @ 14.5% of Incremental Combined GP/IDR Cash Flow Created

35.8

PV @ 15.0% of Incremental Combined GP/IDR Cash Flow Created

35.4

Relevant Present Value of Incremental GP/IDR Cash Flow Created from the Proposed Transaction

$38.8

NRGM Pro Forma Units Outstanding:

Units

% of Total

NRGM Public Unitholders

17.5

11.6%

CMLP Public Unitholders

36.8

24.4%

Crestwood Holdings

21.5

14.2%

NRGY Unitholders

56.4

37.3%

NRGY

6.8

4.5%

NRGM Management

12.0

7.9%

Total NRGM Units

151.0

100.0%

$9.5

Incremental GP/IDR Cash Flow Created from the Proposed Transaction - 24.4%

Confidential

DRAFT

Summary Pro Forma Impact

($ in millions, except per unit amounts)

Project Intrepid

For the Years Ending December 31,

2013E

2014E

2015E

2016E

2017E

$25.0 Million Cash Payment (100% of Original $25.0 Million plus $0.0 Million per Incremental GP IDRs Created)

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $0.73 per Unit Cash Consideration)

$23.38

$24.32

$26.83

$29.58

$32.61

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.3%

8.2%

7.9%

7.4%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

$30.0 Million Cash Payment (100% of Original $25.0 Million plus $5.0 Million per Incremental GP IDRs Created)

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $0.88 per Unit Cash Consideration)

$23.23

$24.17

$26.68

$29.44

$32.47

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.3%

8.2%

7.9%

7.4%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

$34.5 Million Cash Payment (100% of Original $25.0 Million plus $9.5 Million per Incremental GP IDRs Created)

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $1.01 per Unit Cash Consideration)

$23.10

$24.04

$26.55

$29.30

$32.34

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.4%

8.3%

8.0%

7.5%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

$40.0 Million Cash Payment (100% of Original $25.0 Million plus $15.0 Million per Incremental GP IDRs Created)

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $1.17 per Unit Cash Consideration)

$22.94

$23.88

$26.39

$29.14

$32.17

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.4%

8.3%

8.0%

7.5%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

CMLP Management Financial Projections and NRGM Management Financial Projections

$45.0 Million Cash Payment (100% of Original $25.0 Million plus $20.0 Million per Incremental GP IDRs Created)

Standalone Distribution per CMLP Unitholder

$2.07

$2.15

$2.37

$2.60

$2.86

CMLP Current Yield

8.6%

CMLP Standalone Projected Unit Price - Current Yield (Less $1.32 per Unit Cash Consideration)

$22.79

$23.73

$26.24

$29.00

$32.03

Pro Forma Distribution per CMLP Unitholder

$1.93

$1.99

$2.19

$2.33

$2.41

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

8.5%

8.4%

8.0%

7.5%

Incremental GP/IDR Cash Flow Created

($2.4)

$4.8

$16.1

$19.3

$15.6

Confidential

DRAFT

Summary

($ in millions)

Project Intrepid

CMLP Management Financial Projections / NRGM Management Financial Projections

Total Cash Payment

$25.0 / $0.0

$25.0 / $5.0

$25.0 / $9.5

$25.0 / $15.0

$25.0 / $20.0

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)

2013E

8.3%

8.4%

8.5%

2014E

8.2%

8.3%

8.4%

2015E

8.2%

8.3%

8.4%

2016E

7.9%

8.0%

2017E

7.4%

7.5%

Original

CMLP Projections

Base

Sensitivity

Base

Sensitivity

NRGM Projections

Base

Sensitivity

2013E

8.0%

8.1%

8.0%

8.1%

2014E

7.9%

8.0%

7.7%

7.8%

2015E

8.0%

8.4%

7.7%

8.0%

2016E

7.7%

8.7%

7.6%

8.4%

2017E

7.2%

8.7%

7.4%

8.6%

100% of $25.0 Million to CMLP Unaffiliated Unitholders

CMLP Projections

Base

Sensitivity

Base

Sensitivity

NRGM Projections

Base

Sensitivity

2013E

8.3%

8.4%

8.3%

8.4%

2014E

8.2%

8.0%

2015E

8.2%

8.6%

7.9%

8.3%

2016E

7.9%

9.0%

7.8%

8.7%

2017E

7.4%

9.0%

7.6%

8.9%

NRGM Yield Necessary to Achieve CMLP Standalone Projected Unit Price (Breakeven Yield)