Exhibit 4.1

SOUTHWEST GAS CORPORATION

$125,000,000

6.10% Senior Notes due 2041

NOTE PURCHASE AGREEMENT

Dated November 18, 2010

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SOUTHWEST GAS CORPORATION

5241 Spring Mountain Road

Las Vegas, NV 89150-0002

NOTE PURCHASE AGREEMENT

$125,000,000

6.10% Senior Notes due 2041

November 18, 2010

TO EACH OF THE PURCHASERS LISTED IN

SCHEDULE A HERETO:

Ladies and Gentlemen:

Southwest Gas Corporation, a California corporation (the “Company” ), agrees with each of the purchasers whose names appear at the end hereof (each, a “Purchaser” and, collectively, the “Purchasers” ) as follows:

SECTION 1. AUTHORIZATION OF NOTES.

The Company will authorize the issue and sale of $125,000,000 aggregate principal amount of its 6.10% Senior Notes due 2041 (the “Notes” , such term to include any such notes issued in substitution therefor pursuant to Section 13). The Notes shall be substantially in the form set out in Exhibit 1 . Certain capitalized and other terms used in this Agreement are defined in Schedule B ; and references to a “Schedule” or an “Exhibit” are, unless otherwise specified, to a Schedule or an Exhibit attached to this Agreement.

SECTION 2. SALE AND PURCHASE OF NOTES.

Subject to the terms and conditions of this Agreement, the Company will issue and sell to each Purchaser and each Purchaser will purchase from the Company, at the Closing provided for in Section 3, Notes in the principal amount specified opposite such Purchaser’s name in Schedule A at the purchase price of 100% of the principal amount thereof. The Purchasers’ obligations hereunder are several and not joint obligations and no Purchaser shall have any liability to any Person for the performance or non-performance of any obligation by any other Purchaser hereunder.

SECTION 3. CLOSING.

The sale and purchase of the Notes to be purchased by each Purchaser shall occur at the offices of Day Pitney LLP, 242 Trumbull Street, Hartford, Connecticut 06103, at 10:00 a.m.,

Eastern time, at a closing (the “Closing” ) on February 15, 2011 or on such other Business Day on or prior to February 15, 2011 as may be agreed upon by the Company and the Purchasers. At the Closing the Company will deliver to each Purchaser the Notes to be purchased by such Purchaser in the form of a single Note (or such greater number of Notes in denominations of at least $100,000 as such Purchaser may request) dated the date of the Closing and registered in such Purchaser’s name (or in the name of its nominee), against delivery by such Purchaser to the Company or its order of immediately available funds in the amount of the purchase price therefor by wire transfer of immediately available funds for the account of the Company to the account at the bank specified in writing by the Company to the Purchasers in accordance with Section 4.10. If at the Closing the Company shall fail to tender such Notes to any Purchaser as provided above in this Section 3, or any of the conditions specified in Section 4 shall not have been fulfilled to such Purchaser’s satisfaction, such Purchaser shall, at its election, be relieved of all further obligations under this Agreement, without thereby waiving any rights such Purchaser may have by reason of such failure or such nonfulfillment.

SECTION 4. CONDITIONS TO CLOSING.

Each Purchaser’s obligation to purchase and pay for the Notes to be sold to such Purchaser at the Closing is subject to the fulfillment to such Purchaser’s satisfaction, prior to or at the Closing, of the following conditions:

Section 4.1. Representations and Warranties. The representations and warranties of the Company in this Agreement shall be correct when made and at the time of the Closing.

Section 4.2. Performance; No Default. The Company shall have performed and complied with all agreements and conditions contained in this Agreement required to be performed or complied with by it prior to or at the Closing and after giving effect to the issue and sale of the Notes (and the application of the proceeds thereof as contemplated by Section 5.14) no Default or Event of Default shall have occurred and be continuing. Neither the Company nor any Subsidiary shall have entered into any transaction since June 30, 2010 that would have been prohibited by Section 10.1 or Section 10.4 had such Sections applied since such date.

Section 4.3. Compliance Certificates.

(a) Officer’s Certificate . The Company shall have delivered to such Purchaser an Officer’s Certificate, dated the date of the Closing, certifying that the conditions specified in Sections 4.1, 4.2 and 4.9 have been fulfilled.

(b) Secretary’s Certificate . The Company shall have delivered to such Purchaser a certificate of its Secretary or Assistant Secretary, dated the date of Closing, certifying as to the resolutions attached thereto and other corporate proceedings relating to the authorization, execution and delivery of the Notes and this Agreement.

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Section 4.4. Opinions of Counsel. Each Purchaser shall have received opinions in form and substance satisfactory to such Purchaser, dated the date of the Closing (a) from Morrison & Foerster LLP, counsel to the Company, covering the matters set forth in Exhibit 4.4(a) and covering such other matters incident to the transactions contemplated hereby as such Purchaser or its counsel may reasonably request (and the Company hereby instructs its counsel to deliver such opinion to the Purchasers), (b) from Sandra Carolina, Associate General Counsel of the Company, covering the matters set forth in Exhibit 4.4(b) and covering such other matters incident to the transactions contemplated hereby as such Purchaser or its counsel may reasonably request, and (c) from Day Pitney LLP, the Purchasers’ special counsel in connection with such transactions and covering such matters incident to such transactions as such Purchaser may reasonably request.

Section 4.5. Purchase Permitted By Applicable Law, Etc. On the date of the Closing such Purchaser’s purchase of Notes shall (a) be permitted by the laws and regulations of each jurisdiction to which such Purchaser is subject, without recourse to provisions (such as section 1405(a)(8) of the New York Insurance Law) permitting limited investments by insurance companies without restriction as to the character of the particular investment, (b) not violate any applicable law or regulation (including, without limitation, Regulation T, U or X of the Board of Governors of the Federal Reserve System) and (c) not subject such Purchaser to any tax, penalty or liability under or pursuant to any applicable law or regulation, which law or regulation was not in effect on the date hereof. If requested by such Purchaser, such Purchaser shall have received an Officer’s Certificate certifying as to such matters of fact as such Purchaser may reasonably specify to enable such Purchaser to determine whether such purchase is so permitted.

Section 4.6. Sale of Other Notes. Contemporaneously with the Closing the Company shall sell to each other Purchaser and each other Purchaser shall purchase the Notes to be purchased by it at the Closing as specified in Schedule A .

Section 4.7. Payment of Special Counsel Fees. Without limiting the provisions of Section 15.1, the Company shall have paid on or before the Closing the fees, charges and disbursements of the Purchasers’ special counsel referred to in Section 4.4 to the extent reflected in a statement of such counsel rendered to the Company at least one Business Day prior to the Closing.

Section 4.8. Private Placement Number. A Private Placement Number issued by Standard & Poor’s CUSIP Service Bureau (in cooperation with the SVO) shall have been obtained for the Notes.

Section 4.9. Changes in Corporate Structure. The Company shall not have changed its jurisdiction of incorporation or organization, as applicable, or been a party to any merger or consolidation or succeeded to all or any substantial part of the liabilities of any other entity, at any time following June 30, 2010.

Section 4.10. Funding Instructions. At least three Business Days prior to the date of the Closing, each Purchaser shall have received

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written funding instructions signed by a Responsible Officer on letterhead of the Company including (i) the name and address of the bank to which the purchase price for the Notes is to be wire transferred, (ii) such transferee bank’s ABA number, and (iii) the account name and number into which the purchase price for the Notes is to be deposited.

Section 4.11. Proceedings and Documents. All corporate and other proceedings in connection with the transactions contemplated by this Agreement and all documents and instruments incident to such transactions shall be satisfactory to such Purchaser and its special counsel, and such Purchaser and its special counsel shall have received all such counterpart originals or certified or other copies of such documents as such Purchaser or such special counsel may reasonably request.

SECTION 5. REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

The Company represents and warrants to each Purchaser that:

Section 5.1. Organization; Power and Authority. The Company is a corporation duly organized, validly existing and in good standing under the laws of its jurisdiction of incorporation, and is duly qualified as a foreign corporation and is in good standing in each jurisdiction in which such qualification is required by law, other than those jurisdictions as to which the failure to be so qualified or in good standing could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. The Company has the corporate power and authority to own or hold under lease the properties it purports to own or hold under lease, to transact the business it transacts and proposes to transact, to execute and deliver this Agreement and the Notes and to perform the provisions hereof and thereof.

Section 5.2. Authorization, Etc. This Agreement and the Notes have been duly authorized by all necessary corporate action on the part of the Company, and this Agreement constitutes, and upon execution and delivery thereof each Note will constitute, a legal, valid and binding obligation of the Company enforceable against the Company in accordance with its terms, except as such enforceability may be limited by (i) applicable bankruptcy, insolvency, reorganization, moratorium or other similar laws affecting the enforcement of creditors’ rights generally and (ii) general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

Section 5.3. Disclosure. This Agreement and the documents, certificates or other writings delivered to the Purchasers by or on behalf of the Company in connection with the transactions contemplated by this Agreement and the Notes and identified in Schedule 5.3 and the financial statements listed in Schedule 5.5 (this Agreement and such documents, certificates or other writings and such financial statements being referred to, collectively, as the “Disclosure Documents” ), taken as a whole, do not contain any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein not misleading in light of the circumstances under which they were made. Except as disclosed in the Disclosure Documents, since June 30, 2010, there has been no change in the financial condition, operations, business, properties or prospects of the Company or any

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Subsidiary except changes that individually or in the aggregate could not reasonably be expected to have a Material Adverse Effect. There is no fact known to the Company that could reasonably be expected to have a Material Adverse Effect that has not been set forth herein or in the Disclosure Documents.

Section 5.4. Organization and Ownership of Shares of Subsidiaries; Affiliates.

(a) Schedule 5.4 contains (except as noted therein) complete and correct lists (i) of the Company’s Subsidiaries, showing, as to each Subsidiary, the correct name thereof, the jurisdiction of its organization, and the percentage of shares of each class of its capital stock or similar equity interests outstanding owned by the Company and each other Subsidiary, (ii) of the Company’s Affiliates, other than Subsidiaries, and (iii) of the Company’s directors and senior officers.

(b) All of the outstanding shares of capital stock or similar equity interests of each Subsidiary shown in Schedule 5.4 as being owned by the Company and its Subsidiaries have been validly issued, are fully paid and nonassessable and are owned by the Company or another Subsidiary free and clear of any Lien (except as otherwise disclosed in Schedule 5.4 ).

(c) Each Subsidiary identified in Schedule 5.4 is a corporation or other legal entity duly organized, validly existing and in good standing under the laws of its jurisdiction of organization, and is duly qualified as a foreign corporation or other legal entity and is in good standing in each jurisdiction in which such qualification is required by law, other than those jurisdictions as to which the failure to be so qualified or in good standing could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect. Each such Subsidiary has the corporate or other power and authority to own or hold under lease the properties it purports to own or hold under lease and to transact the business it transacts and proposes to transact.

(d) No Subsidiary is a party to, or otherwise subject to any legal, regulatory, contractual or other restriction (other than this Agreement, the agreements listed on Schedule 5.4 , and customary limitations imposed by corporate law or similar statutes) restricting the ability of such Subsidiary to pay dividends out of profits or make any other similar distributions of profits to the Company or any of its Subsidiaries that owns outstanding shares of capital stock or similar equity interests of such Subsidiary.

Section 5.5. Financial Statements; Material Liabilities. The Company has delivered or made available to each Purchaser copies of the financial statements of the Company and its Subsidiaries listed on Schedule 5.5 . All of said financial statements (including in each case the related schedules and notes) fairly present in all material respects the consolidated financial position of the Company and its Subsidiaries as of the respective dates specified in such Schedule and the consolidated results of their operations and cash flows for the respective periods so specified and have been prepared in accordance with GAAP consistently applied throughout the periods involved except as set forth in the notes thereto (subject, in the case of any interim

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financial statements, to normal year-end adjustments). The Company and its Subsidiaries do not have any Material liabilities that are not disclosed on such financial statements or otherwise disclosed in the Disclosure Documents.

Section 5.6. Compliance with Laws, Other Instruments, Etc. The execution, delivery and performance by the Company of this Agreement and the Notes will not (i) contravene, result in any breach of, or constitute a default under, or result in the creation of any Lien in respect of any property of the Company or any Subsidiary under, any indenture, mortgage, deed of trust, loan, purchase or credit agreement, lease, corporate charter or by-laws, or any other agreement or instrument to which the Company or any Subsidiary is bound or by which the Company or any Subsidiary or any of their respective properties may be bound or affected, (ii) conflict with or result in a breach of any of the terms, conditions or provisions of any order, judgment, decree, or ruling of any court, arbitrator or Governmental Authority applicable to the Company or any Subsidiary or (iii) violate any provision of any statute or other rule or regulation of any Governmental Authority applicable to the Company or any Subsidiary.

Section 5.7. Governmental Authorizations, Etc. No consent, approval or authorization of, or registration, filing or declaration with, any Governmental Authority is required in connection with the execution, delivery or performance by the Company of this Agreement or the Notes other than the authorization by the California Public Utilities Commission, which has been obtained and is in full force and effect.

Section 5.8. Litigation; Observance of Agreements, Statutes and Orders.

(a) There are no actions, suits, investigations or proceedings pending or, to the knowledge of the Company, threatened against or affecting the Company or any Subsidiary or any property of the Company or any Subsidiary in any court or before any arbitrator of any kind or before or by any Governmental Authority that, individually or in the aggregate, could reasonably be expected to have a Material Adverse Effect.

(b) Neither the Company nor any Subsidiary is in default under any term of any agreement or instrument to which it is a party or by which it is bound, or any order, judgment, decree or ruling of any court, arbitrator or Governmental Authority or is in violation of any applicable law, ordinance, rule or regulation (including without limitation Environmental Laws or the USA Patriot Act) of any Governmental Authority, which default or violation, individually or in the aggregate, could reasonably be expected to have a Material Adverse Effect.

Section 5.9. Taxes. The Company and its Subsidiaries have filed all tax returns that are required to have been filed in any jurisdiction, and have paid all taxes shown to be due and payable on such returns and all other taxes and assessments levied upon them or their properties, assets, income or franchises, to the extent such taxes and assessments have become due and payable and before they have become delinquent, except for any taxes and assessments (i) the amount of which is not individually or in the

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aggregate Material or (ii) the amount, applicability or validity of which is currently being contested in good faith by appropriate proceedings and with respect to which the Company or a Subsidiary, as the case may be, has established adequate reserves in accordance with GAAP. The Company knows of no basis for any other tax or assessment that could reasonably be expected to have a Material Adverse Effect. The charges, accruals and reserves on the books of the Company and its Subsidiaries in respect of U.S. federal, state or other taxes for all fiscal periods are adequate. The U.S. federal income tax liabilities of the Company and its Subsidiaries have been finally determined (whether by reason of completed audits or the statute of limitations having run) for all fiscal years up to and including the fiscal year ended 2006.

Section 5.10. Title to Property; Leases. The Company and its Subsidiaries have good and sufficient title to their respective properties that individually or in the aggregate are Material, including all such properties reflected in the most recent audited balance sheet referred to in Section 5.5 or purported to have been acquired by the Company or any Subsidiary after said date (except as sold or otherwise disposed of in the ordinary course of business), in each case free and clear of Liens prohibited by this Agreement. All leases that individually or in the aggregate are Material are valid and subsisting and are in full force and effect in all material respects.

Section 5.11. Licenses, Permits, Etc.

(a) The Company and its Subsidiaries own or possess all licenses, permits, franchises, authorizations, patents, copyrights, proprietary software, service marks, trademarks and trade names, or rights thereto, that individually or in the aggregate are Material, without known conflict with the rights of others.

(b) To the best knowledge of the Company, no product of the Company or any of its Subsidiaries infringes in any material respect any license, permit, franchise, authorization, patent, copyright, proprietary software, service mark, trademark, trade name or other right owned by any other Person.

(c) To the best knowledge of the Company, there is no Material violation by any Person of any right of the Company or any of its Subsidiaries with respect to any patent, copyright, proprietary software, service mark, trademark, trade name or other right owned or used by the Company or any of its Subsidiaries.

Section 5.12. Compliance with ERISA.

(a) The Company and each ERISA Affiliate have operated and administered each Plan in compliance with all applicable laws except for such instances of noncompliance as have not resulted in and could not reasonably be expected to result in a Material Adverse Effect. Neither the Company nor any ERISA Affiliate has incurred any liability pursuant to Title I or IV of ERISA or the penalty or excise tax provisions of the Code relating to employee benefit plans (as defined in section 3 of ERISA), and no event, transaction or condition has occurred or exists that could reasonably be expected to result in the incurrence of any such liability by the Company or any ERISA Affiliate, or in the

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imposition of any Lien on any of the rights, properties or assets of the Company or any ERISA Affiliate, in either case pursuant to Title I or IV of ERISA or to such penalty or excise tax provisions or to section 401(a)(29) or 412 of the Code or section 4068 of ERISA, other than such liabilities or Liens as would not be individually or in the aggregate Material.

(b) The present value of the aggregate benefit liabilities under each of the Plans (other than Multiemployer Plans), determined as of the end of such Plan’s most recently ended plan year on the basis of the actuarial assumptions specified for funding purposes in such Plan’s most recent actuarial valuation report, did not exceed the aggregate current value of the assets of such Plan allocable to such benefit liabilities by more than 10% of the Company’s Net Worth. The term “benefit liabilities” has the meaning specified in section 4001 of ERISA and the terms “current value” and “present value” have the meaning specified in section 3 of ERISA.

(c) The Company and its ERISA Affiliates have not incurred withdrawal liabilities (and are not subject to contingent withdrawal liabilities) under section 4201 or 4204 of ERISA in respect of Multiemployer Plans that individually or in the aggregate are Material.

(d) The expected postretirement benefit obligation (determined as of the last day of the Company’s most recently ended fiscal year in accordance with Financial Accounting Standards Board Statement No. 106, without regard to liabilities attributable to continuation coverage mandated by section 4980B of the Code) of the Company and its Subsidiaries is not Material.

(e) The execution and delivery of this Agreement and the issuance and sale of the Notes hereunder will not involve any transaction that is subject to the prohibitions of section 406 of ERISA or in connection with which a tax could be imposed pursuant to section 4975(c)(1)(A)-(D) of the Code. The representation by the Company to each Purchaser in the first sentence of this Section 5.12(e) is made in reliance upon and subject to the accuracy of such Purchaser’s representation in Section 6.2 as to the sources of the funds used to pay the purchase price of the Notes to be purchased by such Purchaser.

Section 5.13. Private Offering by the Company. Neither the Company nor anyone acting on its behalf has offered the Notes or any similar Securities for sale to, or solicited any offer to buy any of the same from, or otherwise approached or negotiated in respect thereof with, any Person other than the Purchasers and not more than three other Institutional Investors, each of which has been offered the Notes at a private sale for investment. Neither the Company nor anyone acting on its behalf has taken, or will take, any action that would subject the issuance or sale of the Notes to the registration requirements of section 5 of the Securities Act or to the registration requirements of any Securities or blue sky laws of any applicable jurisdiction.

Section 5.14. Use of Proceeds; Margin Regulations. The Company will apply the proceeds of the sale of the Notes to repay a portion of the Company’s $200,000,000 8.375% Notes due February 15, 2011.

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No part of the proceeds from the sale of the Notes hereunder will be used, directly or indirectly, for the purpose of buying or carrying any margin stock within the meaning of Regulation U of the Board of Governors of the Federal Reserve System (12 CFR 221), or for the purpose of buying or carrying or trading in any Securities under such circumstances as to involve the Company in a violation of Regulation X of said Board (12 CFR 224) or to involve any broker or dealer in a violation of Regulation T of said Board (12 CFR 220). Margin stock does not constitute more than 2.0% of the value of the consolidated assets of the Company and its Subsidiaries and the Company does not have any present intention that margin stock will constitute more than 2.0% of the value of such assets. As used in this Section, the terms “margin stock” and “purpose of buying or carrying” shall have the meanings assigned to them in said Regulation U.

Section 5.15. Existing Indebtedness; Future Liens.

(a) Except as described therein, Schedule 5.15 sets forth a complete and correct list of all outstanding Indebtedness of the Company and its Subsidiaries as of September 30, 2010 (including a description of the obligors and obligees, principal amount outstanding and collateral therefor, if any, and Guaranty thereof, if any), since which date there has been no Material change in the amounts, interest rates, sinking funds, installment payments or maturities of the Indebtedness of the Company or its Subsidiaries. Neither the Company nor any Subsidiary is in default and no waiver of default is currently in effect, in the payment of any principal or interest on any Indebtedness of the Company or such Subsidiary and no event or condition exists with respect to any Indebtedness of the Company or any Subsidiary that would permit (or that with notice or the lapse of time, or both, would permit) one or more Persons to cause such Indebtedness to become due and payable before its stated maturity or before its regularly scheduled dates of payment.

(b) Neither the Company nor any Subsidiary has agreed or consented to cause or permit in the future (upon the happening of a contingency or otherwise) any of its property, whether now owned or hereafter acquired, to be subject to a Lien not permitted by Section 10.1.

(c) Neither the Company nor any Subsidiary is a party to, or otherwise subject to any provision contained in, any instrument evidencing Indebtedness of the Company or such Subsidiary, any agreement relating thereto or any other agreement (including, but not limited to, its charter or other organizational document) which limits the amount of, or otherwise imposes restrictions on the incurring of, Indebtedness of the Company, except limitations substantially the same as the limitations set forth in Sections 10.9 and 10.11.

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Section 5.16. Foreign Assets Control Regulations, Etc.

(a) Neither the sale of the Notes by the Company hereunder nor its use of the proceeds thereof will violate the Trading with the Enemy Act, as amended, or any of the foreign assets control regulations of the United States Treasury Department (31 CFR, Subtitle B, Chapter V, as amended) or any enabling legislation or executive order relating thereto.

(b) Neither the Company nor any Subsidiary (i) is a Person described or designated in the Specially Designated Nationals and Blocked Persons List of the Office of Foreign Assets Control or in section 1 of the Anti Terrorism Order or (ii) engages in any dealings or transactions with any such Person. The Company and its Subsidiaries are in compliance, in all material respects, with the USA Patriot Act.

(c) No part of the proceeds from the sale of the Notes hereunder will be used, directly or indirectly, for any payments to any governmental official or employee, political party, official of a political party, candidate for political office, or anyone else acting in an official capacity, in order to obtain, retain or direct business or obtain any improper advantage, in violation of the United States Foreign Corrupt Practices Act of 1977, as amended, assuming in all cases that such Act applies to the Company.

Section 5.17. Status under Certain Statutes. Neither the Company nor any Subsidiary is subject to regulation under the Investment Company Act of 1940, as amended, or the ICC Termination Act of 1995, as amended.

Section 5.18. Environmental Matters.

(a) Neither the Company nor any Subsidiary has knowledge of any claim or has received any notice of any claim, and no proceeding has been instituted raising any claim against the Company or any of its Subsidiaries or any of their respective real properties now or formerly owned, leased or operated by any of them or other assets, alleging any damage to the environment or violation of any Environmental Laws, except, in each case, such as could not reasonably be expected to result in a Material Adverse Effect.

(b) Neither the Company nor any Subsidiary has knowledge of any facts which would give rise to any claim, public or private, of violation of Environmental Laws or damage to the environment emanating from, occurring on or in any way related to real properties now or formerly owned, leased or operated by any of them or to other assets or their use, except, in each case, such as could not reasonably be expected to result in a Material Adverse Effect.

(c) Neither the Company nor any Subsidiary has stored any Hazardous Materials on real properties now or formerly owned, leased or operated by any of them and has not disposed of any Hazardous Materials in a manner contrary to any Environmental Laws in each case in any manner that could reasonably be expected to result in a Material Adverse Effect.

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(d) All buildings on all real properties now owned, leased or operated by the Company or any Subsidiary are in compliance with applicable Environmental Laws, except where failure to comply could not reasonably be expected to result in a Material Adverse Effect.

SECTION 6. REPRESENTATIONS OF THE PURCHASERS.

Section 6.1. Purchase for Investment. Each Purchaser severally represents that it is purchasing the Notes for its own account or for one or more separate accounts maintained by such Purchaser or for the account of one or more pension or trust funds and not with a view to the distribution thereof, provided that the disposition of such Purchaser’s or their property shall at all times be within such Purchaser’s or their control. Each Purchaser understands that the Notes have not been registered under the Securities Act and may be resold only if registered pursuant to the provisions of the Securities Act or if an exemption from registration is available, except under circumstances where neither such registration nor such an exemption is required by law, and that the Company is not required to register the Notes.

Section 6.2. Source of Funds. Each Purchaser severally represents that at least one of the following statements is an accurate representation as to each source of funds (a “Source” ) to be used by such Purchaser to pay the purchase price of the Notes to be purchased by such Purchaser hereunder:

(a) the Source is an “insurance company general account” (as the term is defined in the United States Department of Labor’s Prohibited Transaction Exemption ( “PTE” ) 95-60) in respect of which the reserves and liabilities (as defined by the annual statement for life insurance companies approved by the NAIC (the “NAIC Annual Statement” )) for the general account contract(s) held by or on behalf of any employee benefit plan together with the amount of the reserves and liabilities for the general account contract(s) held by or on behalf of any other employee benefit plans maintained by the same employer (or affiliate thereof as defined in PTE 95-60) or by the same employee organization in the general account do not exceed 10% of the total reserves and liabilities of the general account (exclusive of separate account liabilities) plus surplus as set forth in the NAIC Annual Statement filed with such Purchaser’s state of domicile; or

(b) the Source is a separate account that is maintained solely in connection with such Purchaser’s fixed contractual obligations under which the amounts payable, or credited, to any employee benefit plan (or its related trust) that has any interest in such separate account (or to any participant or beneficiary of such plan (including any annuitant)) are not affected in any manner by the investment performance of the separate account; or

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(c) the Source is either (i) an insurance company pooled separate account, within the meaning of PTE 90-1 or (ii) a bank collective investment fund, within the meaning of the PTE 91-38 and, except as disclosed by such Purchaser to the Company in writing pursuant to this clause (c), no employee benefit plan or group of plans maintained by the same employer or employee organization beneficially owns more than 10% of all assets allocated to such pooled separate account or collective investment fund; or

(d) the Source constitutes assets of an “investment fund” (within the meaning of Part V of PTE 84-14 (the “QPAM Exemption” )) managed by a “qualified professional asset manager” or “QPAM” (within the meaning of Part V of the QPAM Exemption), no employee benefit plan’s assets that are included in such investment fund, when combined with the assets of all other employee benefit plans established or maintained by the same employer or by an affiliate (within the meaning of section V(c)(1) of the QPAM Exemption) of such employer or by the same employee organization and managed by such QPAM, exceed 20% of the total client assets managed by such QPAM, the conditions of Part I(c) and (g) of the QPAM Exemption are satisfied, neither the QPAM nor a Person controlling or controlled by the QPAM (applying the definition of “control” in section V(e) of the QPAM Exemption) owns a 5% or more interest in the Company and (i) the identity of such QPAM and (ii) the names of all employee benefit plans whose assets are included in such investment fund have been disclosed to the Company in writing pursuant to this clause (d); or

(e) the Source constitutes assets of a “plan(s)” (within the meaning of section IV of PTE 96-23 (the “INHAM Exemption” )) managed by an “in-house asset manager” or “INHAM” (within the meaning of Part IV of the INHAM Exemption), the conditions of Part I(a), (g) and (h) of the INHAM Exemption are satisfied, neither the INHAM nor a Person controlling or controlled by the INHAM (applying the definition of “control” in section IV(d) of the INHAM Exemption) owns a 5% or more interest in the Company and (i) the identity of such INHAM and (ii) the name(s) of the employee benefit plan(s) whose assets constitute the Source have been disclosed to the Company in writing pursuant to this clause (e); or

(f) the Source is a governmental plan; or

(g) the Source is one or more employee benefit plans, or a separate account or trust fund comprised of one or more employee benefit plans, each of which has been identified to the Company in writing pursuant to this clause (g); or

(h) the Source does not include assets of any employee benefit plan, other than a plan exempt from the coverage of ERISA.

As used in this Section 6.2, the terms “employee benefit plan,” “governmental plan,” and “separate account” shall have the respective meanings assigned to such terms in section 3 of ERISA.

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SECTION 7. INFORMATION AS TO COMPANY.

Section 7.1. Financial and Business Information. The Company shall deliver to each Purchaser (so long as it is obligated to purchase Notes hereunder) and to each holder of Notes that is an Institutional Investor:

(a) Quarterly Statements — within 60 days (or such shorter period as is 15 days greater than the period applicable to the filing of the Company’s Quarterly Report on Form 10-Q (the “Form 10-Q” ) with the SEC regardless of whether the Company is subject to the filing requirements thereof) after the end of each quarterly fiscal period in each fiscal year of the Company (other than the last quarterly fiscal period of each such fiscal year), duplicate copies of,

(i) a consolidated balance sheet of the Company and its Subsidiaries as at the end of such quarter, and

(ii) consolidated statements of income, changes in shareholders’ equity and cash flows of the Company and its Subsidiaries, for such quarter and (in the case of the second and third quarters) for the portion of the fiscal year ending with such quarter,

setting forth in each case in comparative form the figures for the corresponding periods in the previous fiscal year, all in reasonable detail, prepared in accordance with GAAP applicable to quarterly financial statements generally, and certified by a Senior Financial Officer as fairly presenting, in all material respects, the financial position of the companies being reported on and their results of operations and cash flows, subject to changes resulting from year-end adjustments, provided that delivery within the time period specified above of copies of the Company’s Form 10-Q prepared in compliance with the requirements therefor and filed with the SEC shall be deemed to satisfy the requirements of this Section 7.1(a), provided, further, that the Company shall be deemed to have made such delivery of such Form 10-Q if it shall have timely made such Form 10-Q available on “EDGAR” and on its home page on the worldwide web (at the date of this Agreement located at: http//www.swgas.com) (such availability being referred to as “Electronic Delivery” );

(b) Annual Statements — within 105 days (or such shorter period as is 15 days greater than the period applicable to the filing of the Company’s Annual Report on Form 10-K (the “Form 10-K” ) with the SEC regardless of whether the Company is subject to the filing requirements thereof) after the end of each fiscal year of the Company, duplicate copies of

(i) a consolidated balance sheet of the Company and its Subsidiaries as at the end of such year, and

(ii) consolidated statements of income, changes in shareholders’ equity and cash flows of the Company and its Subsidiaries for such year,

setting forth in each case in comparative form the figures for the previous fiscal year, all in reasonable detail, prepared in accordance with GAAP, and accompanied by

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(A) an opinion thereon of independent public accountants of recognized national standing, which opinion shall state that such financial statements present fairly, in all material respects, the financial position of the companies being reported upon and their results of operations and cash flows and have been prepared in conformity with GAAP, and that the examination of such accountants in connection with such financial statements has been made in accordance with generally accepted auditing standards, and that such audit provides a reasonable basis for such opinion in the circumstances, and

(B) a certificate of such accountants stating that they have reviewed this Agreement and stating further whether, in making their audit, they have become aware of any condition or event that then constitutes a Default or an Event of Default, and, if they are aware that any such condition or event then exists, specifying the nature and period of the existence thereof (it being understood that such accountants shall not be liable, directly or indirectly, for any failure to obtain knowledge of any Default or Event of Default unless such accountants should have obtained knowledge thereof in making an audit in accordance with generally accepted auditing standards or did not make such an audit),

provided that the delivery within the time period specified above of the Company’s Form 10-K for such fiscal year (together with the Company’s annual report to shareholders, if any, prepared pursuant to Rule 14a-3 under the Exchange Act) prepared in accordance with the requirements therefor and filed with the SEC, together with the accountant’s certificate described in clause (B) above (the “Accountants’ Certificate” ), shall be deemed to satisfy the requirements of this Section 7.1(b), provided, further, that the Company shall be deemed to have made such delivery of such Form 10-K if it shall have timely made Electronic Delivery thereof, in which event the Company shall separately deliver, concurrently with such Electronic Delivery, the Accountants’ Certificate;

(c) SEC and Other Reports — promptly upon their becoming available, one copy of (i) each financial statement, report, notice or proxy statement sent by the Company or any Subsidiary to its principal lending banks as a whole (excluding information sent to such banks in the ordinary course of administration of a bank facility, such as information relating to pricing and borrowing availability) or to its public Securities holders generally, and (ii) each regular or periodic report, each registration statement (without exhibits except as expressly requested by such holder), and each prospectus and all amendments thereto filed by the Company or any Subsidiary with the SEC and of all press releases and other statements made available generally by the Company or any Subsidiary to the public concerning developments that are Material;

(d) Notice of Default or Event of Default — promptly, and in any event within five days after a Responsible Officer becoming aware of the existence of any Default or Event of Default or that any Person has given any notice or taken any action with respect to a claimed default hereunder or that any Person has given any notice or taken any action with respect to a claimed default of the type referred to in Section 11(g), a written notice specifying the nature and period of existence thereof and what action the Company is taking or proposes to take with respect thereto;

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(e) ERISA Matters — promptly, and in any event within five days after a Responsible Officer becoming aware of any of the following, a written notice setting forth the nature thereof and the action, if any, that the Company or an ERISA Affiliate proposes to take with respect thereto:

(i) with respect to any Plan, any reportable event, as defined in section 4043(c) of ERISA and the regulations thereunder, for which notice thereof has not been waived pursuant to such regulations as in effect on the date hereof; or

(ii) the taking by the PBGC of steps to institute, or the threatening by the PBGC of the institution of, proceedings under section 4042 of ERISA for the termination of, or the appointment of a trustee to administer, any Plan, or the receipt by the Company or any ERISA Affiliate of a notice from a Multi-employer Plan that such action has been taken by the PBGC with respect to such Multi-employer Plan; or

(iii) any event, transaction or condition that could result in the incurrence of any liability by the Company or any ERISA Affiliate pursuant to Title I or IV of ERISA or the penalty or excise tax provisions of the Code relating to employee benefit plans, or in the imposition of any Lien on any of the rights, properties or assets of the Company or any ERISA Affiliate pursuant to Title I or IV of ERISA or such penalty or excise tax provisions, if such liability or Lien, taken together with any other such liabilities or Liens then existing, could reasonably be expected to have a Material Adverse Effect;

(f) Notices from Governmental Authority — promptly, and in any event within 30 days of receipt thereof, copies of any notice to the Company or any Subsidiary from any federal or state Governmental Authority relating to any order, ruling, statute or other law or regulation that could reasonably be expected to have a Material Adverse Effect; and

(g) Requested Information — with reasonable promptness, such other data and information relating to the business, operations, affairs, financial condition, assets or properties of the Company or any of its Subsidiaries (including, but without limitation, actual copies of the Company’s Form 10-Q and Form 10-K) or relating to the ability of the Company to perform its obligations hereunder and under the Notes as from time to time may be reasonably requested by any such holder of Notes.

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Section 7.2. Officer’s Certificate. Each set of financial statements delivered pursuant to Section 7.1(a) or Section 7.1(b) shall be accompanied by a certificate of a Senior Financial Officer setting forth (which, in the case of Electronic Delivery of any such financial statements, shall be by separate concurrent delivery of such certificate to each holder of Notes):

(a) Covenant Compliance — the information (including detailed calculations) required in order to establish whether the Company was in compliance with the requirements of Section 10.9, Section 10.10, and Section 10.11 as of the end of the quarterly or annual period covered by the statements then being furnished (including with respect to each such Section, where applicable, the calculations of the maximum or minimum amount, ratio or percentage, as the case may be, permissible under the terms of such Sections, and the calculation of the amount, ratio or percentage then in existence); and

(b) Event of Default — a statement that such Senior Financial Officer has reviewed the relevant terms hereof and has made, or caused to be made, under his or her supervision, a review of the transactions and conditions of the Company and its Subsidiaries from the beginning of the quarterly or annual period covered by the statements then being furnished to the date of the certificate and that such review shall not have disclosed the existence during such period of any condition or event that constitutes a Default or an Event of Default or, if any such condition or event existed or exists (including, without limitation, any such event or condition resulting from the failure of the Company or any Subsidiary to comply with any Environmental Law), specifying the nature and period of existence thereof and what action the Company shall have taken or proposes to take with respect thereto.

Section 7.3. Visitation. The Company shall permit the representatives of each holder of Notes that is an Institutional Investor:

(a) No Default — if no Default or Event of Default then exists, at the expense of such holder and upon reasonable prior notice to the Company, to visit the principal executive office of the Company, to discuss the affairs, finances and accounts of the Company and its Subsidiaries with the Company’s officers, and (with the consent of the Company, which consent will not be unreasonably withheld) its independent public accountants, and (with the consent of the Company, which consent will not be unreasonably withheld) to visit the other offices and properties of the Company and each Subsidiary, all at such reasonable times and as often as may be reasonably requested in writing; and

(b) Default — if a Default or Event of Default then exists, at the expense of the Company to visit and inspect any of the offices or properties of the Company or any Subsidiary, to examine all their respective books of account, records, reports and other papers, to make copies and extracts therefrom, and to discuss their respective affairs, finances and accounts with their respective officers and independent public accountants (and by this provision the Company authorizes said accountants to discuss the affairs, finances and accounts of the Company and its Subsidiaries), all at such times and as often as may be requested.

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SECTION 8. PAYMENT AND PREPAYMENT OF THE NOTES.

Section 8.1. Maturity. As provided therein, the entire unpaid principal balance of the Notes shall be due and payable on the stated maturity date thereof.

Section 8.2. Optional Prepayments with Make-Whole Amount. The Company may, at its option, upon notice as provided below, prepay at any time all, or from time to time any part of, the Notes, in an amount not less than 5% of the aggregate principal amount of the Notes then outstanding in the case of a partial prepayment, at 100% of the principal amount so prepaid, and the Make-Whole Amount determined for the prepayment date with respect to such principal amount. The Company will give each holder of Notes written notice of each optional prepayment under this Section 8.2 not less than 30 days and not more than 60 days prior to the date fixed for such prepayment. Each such notice shall specify such date (which shall be a Business Day), the aggregate principal amount of the Notes to be prepaid on such date, the principal amount of each Note held by such holder to be prepaid (determined in accordance with Section 8.3), and the interest to be paid on the prepayment date with respect to such principal amount being prepaid, and shall be accompanied by a certificate of a Senior Financial Officer as to the estimated Make-Whole Amount due in connection with such prepayment (calculated as if the date of such notice were the date of the prepayment), setting forth the details of such computation. Two Business Days prior to such prepayment, the Company shall deliver to each holder of Notes a certificate of a Senior Financial Officer specifying the calculation of such Make-Whole Amount as of the specified prepayment date.

Section 8.3. Allocation of Partial Prepayments. In the case of each partial prepayment of the Notes, the principal amount of the Notes to be prepaid shall be allocated among all of the Notes at the time outstanding in proportion, as nearly as practicable, to the respective unpaid principal amounts thereof not theretofore called for prepayment.

Section 8.4. Maturity; Surrender, Etc. In the case of each prepayment of Notes pursuant to this Section 8, the principal amount of each Note to be prepaid shall mature and become due and payable on the date fixed for such prepayment (which shall be a Business Day), together with interest on such principal amount accrued to such date and the applicable Make-Whole Amount, if any. From and after such date, unless the Company shall fail to pay such principal amount when so due and payable, together with the interest and Make-Whole Amount, if any, as aforesaid, interest on such principal amount shall cease to accrue. Any Note paid or prepaid in full shall be surrendered to the Company and cancelled and shall not be reissued, and no Note shall be issued in lieu of any prepaid principal amount of any Note.

Section 8.5. Purchase of Notes. The Company will not and will not permit any Affiliate to purchase, redeem, prepay or otherwise acquire, directly or indirectly, any of the outstanding Notes except upon the payment or prepayment of the Notes in accordance with the terms of this Agreement and the Notes. The Company will promptly cancel all Notes acquired by it or any Affiliate pursuant to any payment or prepayment of Notes pursuant to any provision of this Agreement and no Notes may be issued in substitution or exchange for any such Notes.

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Section 8.6. Make-Whole Amount.

“Make-Whole Amount” means, with respect to any Note, an amount equal to the excess, if any, of the Discounted Value of the Remaining Scheduled Payments with respect to the Called Principal of such Note over the amount of such Called Principal, provided that the Make-Whole Amount may in no event be less than zero. For the purposes of determining the Make-Whole Amount, the following terms have the following meanings:

“Called Principal” means, with respect to any Note, the principal of such Note that is to be prepaid pursuant to Section 8.2 or has become or is declared to be immediately due and payable pursuant to Section 12.1, as the context requires.

“Discounted Value” means, with respect to the Called Principal of any Note, the amount obtained by discounting all Remaining Scheduled Payments with respect to such Called Principal from their respective scheduled due dates to the Settlement Date with respect to such Called Principal, in accordance with accepted financial practice and at a discount factor (applied on the same periodic basis as that on which interest on the Notes is payable) equal to the Reinvestment Yield with respect to such Called Principal.

“Reinvestment Yield” means, with respect to the Called Principal of any Note, 0.50% over the yield to maturity implied by (i) the yields reported as of 10:00 a.m. (New York City time) on the second Business Day preceding the Settlement Date with respect to such Called Principal, on the display designated as “Page PX1” (or such other display as may replace Page PX1) on Bloomberg Financial Markets for the most recently issued actively traded on the run U.S. Treasury Securities having a maturity equal to the Remaining Average Life of such Called Principal as of such Settlement Date, or (ii) if such yields are not reported as of such time or the yields reported as of such time are not ascertainable (including by way of interpolation), the Treasury Constant Maturity Series Yields reported, for the latest day for which such yields have been so reported as of the second Business Day preceding the Settlement Date with respect to such Called Principal, in Federal Reserve Statistical Release H.15 (or any comparable successor publication) for U.S. Treasury Securities having a constant maturity equal to the Remaining Average Life of such Called Principal as of such Settlement Date.

In the case of each determination under clause (i) or clause (ii), as the case may be, of the preceding paragraph, such implied yield will be determined, if necessary, by (a) converting U.S. Treasury bill quotations to bond equivalent yields in accordance with accepted financial practice and (b) interpolating linearly between (1) the applicable actively traded on the run U.S. Treasury Security with the maturity closest to and greater than such Remaining Average Life and (2) the applicable actively traded on the run U.S. Treasury Security with the maturity closest to and less than such Remaining Average Life. The Reinvestment Yield shall be rounded to the number of decimal places as appears in the interest rate of the applicable Note.

“Remaining Average Life” means, with respect to any Called Principal, the number of years (calculated to the nearest one-twelfth year) obtained by dividing (i) such Called Principal into (ii) the sum of the products obtained by multiplying (a) the principal component of each Remaining Scheduled Payment with respect to such Called Principal by (b) the number of years (calculated to the nearest one-twelfth year) that will elapse between the Settlement Date with respect to such Called Principal and the scheduled due date of such Remaining Scheduled Payment.

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“Remaining Scheduled Payments” means, with respect to the Called Principal of any Note, all payments of such Called Principal and interest thereon that would be due after the Settlement Date with respect to such Called Principal if no payment of such Called Principal were made prior to its scheduled due date, provided that if such Settlement Date is not a date on which interest payments are due to be made under the terms of the Notes, then the amount of the next succeeding scheduled interest payment will be reduced by the amount of interest accrued to such Settlement Date and required to be paid on such Settlement Date pursuant to Section 8.2 or Section 12.1.

“Settlement Date” means, with respect to the Called Principal of any Note, the date on which such Called Principal is to be prepaid pursuant to Section 8.2 or has become or is declared to be immediately due and payable pursuant to Section 12.1, as the context requires.

Section 8.7. Mandatory Offer to Prepay in Event of Change in Control.

(a) Notice of Change in Control or Control Event — The Company will, within five Business Days after any Responsible Officer has knowledge of the occurrence of any Change in Control or Control Event, give written notice of such Change in Control or Control Event to each holder of Notes unless notice in respect of such Change in Control (or the Change in Control contemplated by such Control Event) shall have been given pursuant to subparagraph (b) of this Section 8.7. If a Change in Control has occurred, such notice shall contain and constitute an offer to each holder of Notes to prepay Notes as described in subparagraph (c) of this Section 8.7 and shall be accompanied by the certificate described in subparagraph (f) of this Section 8.7.

(b) Condition to Company Action — The Company will not take any action that consummates or finalizes a Change in Control unless (i) at least 30 days prior to such action it shall have given to each holder of Notes written notice containing and constituting an offer to prepay Notes as described in subparagraph (c) of this Section 8.7, accompanied by the certificate described in subparagraph (f) of this Section 8.7, and (ii) contemporaneously with such action, it prepays all Notes required to be prepaid in accordance with this Section 8.7.

(c) Offer to Prepay Notes — The offer to prepay Notes contemplated by subparagraphs (a) and (b) of this Section 8.7 shall be an offer to prepay, in accordance with and subject to this Section 8.7, all, but not less than all, the Notes held by each holder (in this case only, “holder” in respect of any Note registered in the name of a nominee for a disclosed beneficial owner shall mean such beneficial owner) on a date specified in such offer (the “Proposed Prepayment Date” ).

(i) If such Proposed Prepayment Date is in connection with an offer relating to a Change in Control that has already occurred, such date shall be not less than 30 days and not more than 60 days after the date of such offer (if the Proposed Prepayment Date shall not be specified in such offer, the Proposed Prepayment Date shall be the 60 ^th day after the date of such offer).

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(ii) If such Proposed Prepayment Date is in connection with an offer relating to a Change in Control that has not yet occurred, such date shall be the expected date of the occurrence of such Change in Control (as can best be determined by the Company at the time it makes such offer). In the event that the expected date of the occurrence of such Change in Control changes or such Change in Control does not occur on the Proposed Prepayment Date in respect thereof, the prepayment shall be deferred until and shall be made on the date on which such Change in Control occurs. The Company shall keep each holder of Notes reasonably and timely informed of (A) any such change or deferral of the date of prepayment, (B) the date on which such Change in Control and the prepayment are expected to occur (as can best be determined by the Company from time to time), and (C) any determination by the Company that efforts to effect such Change in Control have ceased or been abandoned (in which case the offers and acceptances made pursuant to this Section 8.7 in respect of such Change in Control shall be deemed rescinded).

Any notice containing and constituting such offer shall be dated the date on which it is first given to the holders of Notes and such notices to all holders of Notes shall bear the same date.

(d) Acceptance — A holder of Notes may accept the offer to prepay made pursuant to this Section 8.7 by causing a notice of such acceptance to be delivered to the Company at least 10 days prior to the Proposed Prepayment Date. A failure by a holder of Notes to respond to an offer to prepay made pursuant to this Section 8.7 shall be deemed to constitute an acceptance of such offer by such holder.

(e) Prepayment — Prepayment of the Notes to be prepaid pursuant to this Section 8.7 shall be at 100% of the principal amount of such Notes plus a premium equal to 1% of such principal amount, together with interest on such Notes accrued to the date of prepayment. The prepayment shall be made on the Proposed Prepayment Date except as provided in subparagraph (c)(ii) of this Section 8.7. The obligation of the Company to prepay Notes pursuant to the offers required by subparagraph (b) and accepted in accordance with subparagraph (d) of this Section 8.7 is subject to the occurrence of the Change in Control in respect of which such offers and acceptances shall have been made.

(f) Officer’s Certificate — Each offer to prepay the Notes pursuant to this Section 8.7 shall be accompanied by a certificate, executed by a Senior Financial Officer of the Company and dated the date of such offer, specifying: (i) the Proposed Prepayment Date; (ii) that such offer is made pursuant to this Section 8.7; (iii) the principal amount of each Note offered to be prepaid; (iv) the amount of the premium specified in Section 8.7(e), if any, due in connection with such prepayment; (v) the interest that would be due on each Note offered to be prepaid, accrued to the Proposed Prepayment Date; (vi) that the conditions of this Section 8.7 have been fulfilled; and (vii) in reasonable detail, the nature and date or expected date of the Change in Control (as can best be determined by the Company at the time it makes such offer).

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SECTION 9. AFFIRMATIVE COVENANTS.

The Company covenants that so long as any Purchaser is committed to purchase any of the Notes hereunder or any of the Notes are outstanding:

Section 9.1. Compliance with Law. Without limiting Section 10.7, the Company will, and will cause each of its Subsidiaries to, comply with all laws, ordinances or governmental rules or regulations to which each of them is subject, including, without limitation, ERISA, the USA Patriot Act and Environmental Laws, and will obtain and maintain in effect all licenses, certificates, permits, franchises and other governmental authorizations necessary to the ownership of their respective properties or to the conduct of their respective businesses, in each case to the extent necessary to ensure that non-compliance with such laws, ordinances or governmental rules or regulations or failures to obtain or maintain in effect such licenses, certificates, permits, franchises and other governmental authorizations could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

Section 9.2. Insurance. The Company will, and will cause each of its Subsidiaries to, maintain, with financially sound and reputable insurers, insurance with respect to their respective properties and businesses against such casualties and contingencies, of such types, on such terms and in such amounts (including deductibles, co-insurance and self-insurance, if adequate reserves are maintained with respect thereto) as is customary in the case of entities of established reputations engaged in the same or a similar business and similarly situated.

Section 9.3. Maintenance of Properties. The Company will, and will cause each of its Subsidiaries to, maintain and keep, or cause to be maintained and kept, their respective properties in good repair, working order and condition (other than ordinary wear and tear), so that the business carried on in connection therewith may be properly conducted at all times, provided that this Section shall not prevent the Company or any Subsidiary from discontinuing the operation and the maintenance of any of its properties if such discontinuance is desirable in the conduct of its business and the Company has concluded that such discontinuance could not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.

Section 9.4. Payment of Taxes and Claims. The Company will, and will cause each of its Subsidiaries to, file all tax returns required to be filed in any jurisdiction and to pay and discharge all taxes shown to be due and payable on such returns and all other taxes, assessments, governmental charges, or levies imposed on them or any of their properties, assets, income or franchises, to the extent the same have become due and payable and before they have become delinquent and all claims for which sums have become due and payable that have or might become a Lien on properties or assets of the Company or any Subsidiary, provided that neither the Company nor any Subsidiary need pay

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any such tax, assessment, charge, levy or claim if (i) the amount, applicability or validity thereof is contested by the Company or such Subsidiary on a timely basis in good faith and in appropriate proceedings, and the Company or a Subsidiary has established adequate reserves therefor in accordance with GAAP on the books of the Company or such Subsidiary or (ii) the failure to file or nonpayment of all such taxes, assessments, charges, levies and claims in the aggregate could not reasonably be expected to have a Material Adverse Effect.

Section 9.5. Corporate Existence, Etc. Subject to Section 10.2, the Company will at all times preserve and keep in full force and effect its corporate existence. Subject to Section 10.2, the Company will at all times preserve and keep in full force and effect the corporate existence of each of its Subsidiaries (unless merged into the Company or a Wholly-Owned Subsidiary) and all rights and franchises of the Company and its Subsidiaries unless, in the good faith judgment of the Company, the termination of or failure to preserve and keep in full force and effect such corporate existence, right or franchise could not, individually or in the aggregate, have a Material Adverse Effect.

Section 9.6. Books and Records. The Company will, and will cause each of its Subsidiaries to, maintain proper books of record and account in conformity with GAAP and all applicable requirements of any Governmental Authority having legal or regulatory jurisdiction over the Company or such Subsidiary, as the case may be.

SECTION 10. NEGATIVE COVENANTS.

The Company covenants that so long as any Purchaser is committed to purchase any of the Notes hereunder or any of the Notes are outstanding:

Section 10.1. Liens. The Company will not create or suffer to exist, or permit any of its Subsidiaries to create or suffer to exist, any Lien upon or with respect to any of its property except Permitted Liens, unless and until the Company makes or causes to be made effective provision whereby the Notes will be secured equally and ratably with any and all other obligations thereby secured, such security to be pursuant to agreements reasonably satisfactory in writing to the Required Holders and, in any such case, the Notes shall have the benefit, to the fullest extent that, and with such priority as, the holders of the Notes may be entitled under applicable law, of an equitable Lien on such property.

Section 10.2. Merger, Consolidation, Etc. The Company will not consolidate with or merge with any other Person or convey, transfer or lease all or substantially all of its assets in a single transaction or series of transactions to any Person unless:

(a) the successor formed by such consolidation or the survivor of such merger or the Person that acquires by conveyance, transfer or lease all or substantially all of the assets of the Company as an entirety, as the case may be, shall be a solvent corporation or limited liability company organized and existing under the laws of the United States or any State thereof (including the District of Columbia), and, if the Company is not such

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corporation or limited liability company, (i) such corporation or limited liability company shall have executed and delivered to each holder of any Notes its assumption of the due and punctual performance and observance of each covenant and condition of this Agreement and the Notes and (ii) such corporation or limited liability company shall have caused to be delivered to each holder of any Notes an opinion of nationally recognized independent counsel, or other independent counsel reasonably satisfactory to the Required Holders, to the effect that all agreements or instruments effecting such assumption are enforceable in accordance with their terms and comply with the terms hereof; and

(b) immediately before and immediately after giving effect to such transaction, no Default or Event of Default shall have occurred and be continuing.

No such conveyance, transfer or lease of substantially all of the assets of the Company shall have the effect of releasing the Company or any successor corporation or limited liability company that shall theretofore have become such in the manner prescribed in this Section 10.2 from its liability under this Agreement or the Notes.

Section 10.3. Investments and Acquisitions. The Company will not make, or permit any of its Significant Subsidiaries to make, any Investments or Acquisitions except (1) for Permitted Investments, (2) as required by any Governmental Authority, and (3) for Acquisitions, provided that:

(a) immediately before or after giving effect to each Acquisition, no Default shall or would exist, and immediately after giving effect thereto, all of the representations and warranties contained in this Agreement shall be true and correct with the same effect as though then made,

(b) the Person or business acquired is engaged in the same line of business as the Company or any Significant Subsidiary,

(c) the Company shall have delivered to each holder of Notes notice thereof not less than ten days prior to the consummation of such Acquisition,

(d) the Company shall have delivered to each holder of Notes a certificate of a financial officer thereof, in all respects reasonably satisfactory to such holders and dated the date of such consummation,

(i) certifying that prior to and after giving effect to such Acquisition and based on the most recent financial statements delivered pursuant to Section 7.1(b), the Company is and will be in compliance with Sections 10.9, 10.10, and 10.11, and

(ii) providing or attaching such other information, documents and other items as the Required Holders shall have reasonably requested.

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Section 10.4. Transactions with Affiliates. The Company will not and will not permit any Subsidiary to enter into directly or indirectly any transaction or group of related transactions (including without limitation the purchase, lease, sale or exchange of properties of any kind or the rendering of any service) with any Affiliate (other than the Company or another Subsidiary), except pursuant to the reasonable requirements of the Company’s or such Subsidiary’s business and upon fair and reasonable terms no less favorable to the Company or such Subsidiary than would be obtainable in a comparable arm’s-length transaction with a Person not an Affiliate.

Section 10.5. Restricted Payments. The Company will not declare or make any dividend payment or other distribution of assets, properties, cash, rights, obligations or Securities on account of any shares of any class of its capital stock or purchase, redeem or otherwise acquire for value (or permit any of its Subsidiaries to do so) any shares of its capital stock or any warrants, rights or options to acquire such shares, now or hereafter outstanding if a Default or Event of Default has occurred and is continuing or would result therefrom.

Section 10.6. Line of Business, Etc.

(a) The Company will not and will not permit any Subsidiary to engage in any business if, as a result, the general nature of the business in which the Company and its Subsidiaries, taken as a whole, would then be engaged would be substantially changed from the general nature of the business in which the Company and its Subsidiaries, taken as a whole, are engaged on the date of this Agreement.

(b) The Company will not transfer any Material portion of the assets used in its natural gas operations as conducted as of the date hereof to any one or more of its Subsidiaries, nor will the Company permit any Material portion of such operations to be conducted through or by any one or more of its Subsidiaries.

Section 10.7. Terrorism Sanctions Regulations. The Company will not and will not permit any Subsidiary to (a) become a Person described or designated in the Specially Designated Nationals and Blocked Persons List of the Office of Foreign Assets Control or in section 1 of the Anti Terrorism Order or (b) engage in any dealings or transactions with any such Person.

Section 10.8. Guaranties. The Company will not cause or permit any Person to guarantee the obligations of the Company under any Primary Bank Facility unless and until the Company causes such Person to guarantee the obligations of the Company under this Agreement and the Notes pursuant to an agreement or agreements reasonably acceptable in writing to the Required Holders. For avoidance of doubt, this Section 10.8 shall not in any way prohibit the Company from causing or permitting any Person to guarantee the obligations of any Subsidiary under any Primary Bank Facility.

Section 10.9. Leverage Ratio. The Company will not permit the ratio of Funded Debt to Total Capitalization to exceed 0.70 to 1.00 as of the end of any quarter of any fiscal year.

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Section 10.10. Net Worth. The Company will not permit its Net Worth to be less than $550,000,000 as of the end of any quarter of any fiscal year.

Section 10.11. Priority Debt. The Company will not permit Priority Debt to exceed 10% of Total Capitalization as of the end of any quarter of any fiscal year.

SECTION 11. EVENTS OF DEFAULT.

An “Event of Default” shall exist if any of the following conditions or events shall occur and be continuing:

(a) the Company defaults in the payment of any principal or Make-Whole Amount, if any, on any Note when the same becomes due and payable, whether at maturity or at a date fixed for prepayment or by declaration or otherwise; or

(b) the Company defaults in the payment of any interest on any Note for more than five Business Days after the same becomes due and payable; or

(c) the Company defaults in the performance of or compliance with any term contained in Section 7.1(d) or Section 10.9, 10.10, or 10.11; or

(d) the Company defaults in the performance of or compliance with any term contained in Section 10.1 and such default is not remedied within 30 days after the earlier of (i) a Responsible Officer obtaining actual knowledge of such default and (ii) the Company receiving written notice of such default from any holder of a Note (any such written notice to be identified as a “notice of default” and to refer specifically to this Section 11(d)); or

(e) the Company defaults in the performance of or compliance with any term contained herein (other than those referred to in Sections 11(a), (b), (c), and (d)) and such default is not remedied within 30 days after the earlier of (i) a Responsible Officer obtaining actual knowledge of such default and (ii) the Company receiving written notice of such default from any holder of a Note (any such written notice to be identified as a “notice of default” and to refer specifically to this Section 11(e)); or

(f) any representation or warranty made in writing by or on behalf of the Company or by any officer of the Company in this Agreement or in any writing furnished in connection with the transactions contemplated hereby proves to have been false or incorrect in any material respect on the date as of which made; or

(g) (i) the Company or any Subsidiary is in default (as principal or as guarantor or other surety) in the payment of any principal of or premium or make-whole amount or interest on any Indebtedness that is outstanding in an aggregate principal amount of at least $10,000,000 beyond any period of grace provided with respect thereto, or (ii) the Company or any Subsidiary is in default in the performance of or compliance

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with any term of any evidence of any Indebtedness in an aggregate outstanding principal amount of at least $10,000,000 or of any mortgage, indenture or other agreement relating thereto or any other condition exists, and as a consequence of such default or condition such Indebtedness has become, or has been declared (or one or more Persons are entitled to declare such Indebtedness to be), due and payable before its stated maturity or before its regularly scheduled dates of payment, or (iii) as a consequence of the occurrence or continuation of any event or condition (other than the passage of time or the right of the holder of Indebtedness to convert such Indebtedness into equity interests), (x) the Company or any Subsidiary has become obligated to purchase or repay Indebtedness before its regular maturity or before its regularly scheduled dates of payment in an aggregate outstanding principal amount of at least $10,000,000, or (y) one or more Persons have the right to require the Company or any Subsidiary so to purchase or repay such Indebtedness; or

(h) the Company or any Subsidiary (i) is generally not paying, or admits in writing its inability to pay, its debts as they become due, (ii) files, or consents by answer or otherwise to the filing against it of, a petition for relief or reorganization or arrangement or any other petition in bankruptcy, for liquidation or to take advantage of any bankruptcy, insolvency, reorganization, moratorium or other similar law of any jurisdiction, (iii) makes an assignment for the benefit of its creditors, (iv) consents to the appointment of a custodian, receiver, trustee or other officer with similar powers with respect to it or with respect to any substantial part of its property, (v) is adjudicated as insolvent or to be liquidated, or (vi) takes corporate action for the purpose of any of the foregoing; or

(i) a court or other Governmental Authority of competent jurisdiction enters an order appointing, without consent by the Company or any of its Subsidiaries, a custodian, receiver, trustee or other officer with similar powers with respect to it or with respect to any substantial part of its property, or constituting an order for relief or approving a petition for relief or reorganization or any other petition in bankruptcy or for liquidation or to take advantage of any bankruptcy or insolvency law of any jurisdiction, or ordering the dissolution, winding-up or liquidation of the Company or any of its Subsidiaries, or any such petition shall be filed against the Company or any of its Subsidiaries and such petition shall not be dismissed within 60 days; or

(j) a final judgment or judgments for the payment of money aggregating in excess of $10,000,000 are rendered against one or more of the Company and its Subsidiaries and which judgments are not, within 60 days after entry thereof, bonded, discharged or stayed pending appeal, or are not discharged within 60 days after the expiration of such stay; or

(k) if (i) any Plan shall fail to satisfy the minimum funding standards of ERISA or the Code for any plan year or part thereof or a waiver of such standards or extension of any amortization period is sought or granted under section 412 of the Code, (ii) a notice of intent to terminate any Plan shall have been or is reasonably expected to be filed with the PBGC or the PBGC shall have instituted proceedings under ERISA section 4042 to terminate or appoint a trustee to administer any Plan or the PBGC shall have

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notified the Company or any ERISA Affiliate that a Plan may become a subject of any such proceedings, (iii) the aggregate “amount of unfunded benefit liabilities” (within the meaning of section 4001(a)(18) of ERISA) under all Plans, determined in accordance with Title IV of ERISA, shall exceed 10% of the Company’s Net Worth, (iv) the Company or any ERISA Affiliate shall have incurred or is reasonably expected to incur any liability pursuant to Title I or IV of ERISA or the penalty or excise tax provisions of the Code relating to employee benefit plans, (v) the Company or any ERISA Affiliate withdraws from any Multiemployer Plan, or (vi) the Company or any Subsidiary establishes or amends any employee welfare benefit plan that provides post-employment welfare benefits in a manner that would increase the liability of the Company or any Subsidiary thereunder; and any such event or events described in clauses (i) through (vi) above, either individually or together with any other such event or events, could reasonably be expected to have a Material Adverse Effect.

As used in Section 11(k), the terms “employee benefit plan” and “employee welfare benefit plan” shall have the respective meanings assigned to such terms in section 3 of ERISA.

SECTION 12. REMEDIES ON DEFAULT, ETC.

Section 12.1. Acceleration.

(a) If an Event of Default with respect to the Company described in Section 11(h) or (i) (other than an Event of Default described in clause (i) of Section 11(h) or described in clause (vi) of Section 11(h) by virtue of the fact that such clause encompasses clause (i) of Section 11(h)) has occurred, all the Notes then outstanding shall automatically become immediately due and payable.

(b) If any other Event of Default has occurred and is continuing, any holder or holders of more than 25% in principal amount of the Notes at the time outstanding may at any time at its or their option, by notice or notices to the Company, declare all the Notes then outstanding to be immediately due and payable.

(c) If any Event of Default described in Section 11(a) or (b) has occurred and is continuing, any holder or holders of Notes at the time outstanding affected by such Event of Default may at any time, at its or their option, by notice or notices to the Company, declare all the Notes held by it or them to be immediately due and payable.

Upon any Notes becoming due and payable under this Section 12.1, whether automatically or by declaration, such Notes will forthwith mature and the entire unpaid principal amount of such Notes, plus (x) all accrued and unpaid interest thereon (including, but not limited to, interest accrued thereon at the Default Rate) and (y) the Make-Whole Amount determined in respect of such principal amount (to the full extent permitted by applicable law), shall all be immediately due and payable, in each and every case without presentment, demand, protest or further notice, all of which are hereby waived. The Company acknowledges, and the parties hereto agree, that each holder of a Note has the right to maintain its investment in the Notes free from repayment by the Company (except as herein specifically provided for) and that the

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provision for payment of a Make-Whole Amount by the Company in the event that the Notes are prepaid or are accelerated as a result of an Event of Default, is intended to provide compensation for the deprivation of such right under such circumstances.

Section 12.2. Other Remedies. If any Default or Event of Default has occurred and is continuing, and irrespective of whether any Notes have become or have been declared immediately due and payable under Section 12.1, the holder of any Note at the time outstanding may proceed to protect and enforce the rights of such holder by an action at law, suit in equity or other appropriate proceeding, whether for the specific performance of any agreement contained herein or in any Note, or for an injunction against a violation of any of the terms hereof or thereof, or in aid of the exercise of any power granted hereby or thereby or by law or otherwise.

Section 12.3. Rescission. At any time after any Notes have been declared due and payable pursuant to Section 12.1(b) or (c), the holders of not less than 76% in principal amount of the Notes then outstanding, by written notice to the Company, may rescind and annul any such declaration and its consequences if (a) the Company has paid all overdue interest on the Notes, all principal of and Make-Whole Amount, if any, on any Notes that are due and payable and are unpaid other than by reason of such declaration, and all interest on such overdue principal and Make-Whole Amount, if any, and (to the extent permitted by applicable law) any overdue interest in respect of the Notes, at the Default Rate, (b) neither the Company nor any other Person shall have paid any amounts which have become due solely by reason of such declaration, (c) all Events of Default and Defaults, other than non-payment of amounts that have become due solely by reason of such declaration, have been cured or have been waived pursuant to Section 17, and (d) no judgment or decree has been entered for the payment of any monies due pursuant hereto or to the Notes. No rescission and annulment under this Section 12.3 will extend to or affect any subsequent Event of Default or Default or impair any right consequent thereon.

Section 12.4. No Waivers or Election of Remedies, Expenses, Etc. No course of dealing and no delay on the part of any holder of any Note in exercising any right, power or remedy shall operate as a waiver thereof or otherwise prejudice such holder’s rights, powers or remedies. No right, power or remedy conferred by this Agreement or by any Note upon any holder thereof shall be exclusive of any other right, power or remedy referred to herein or therein or now or hereafter available at law, in equity, by statute or otherwise. Without limiting the obligations of the Company under Section 15, the Company will pay to the holder of each Note on demand such further amount as shall be sufficient to cover all costs and expenses of such holder incurred in any enforcement or collection under this Section 12, including, without limitation, reasonable attorneys’ fees, expenses and disbursements.

SECTION 13. REGISTRATION; EXCHANGE; SUBSTITUTION OF NOTES.

Section 13.1. Registration of Notes. The Company shall keep at its principal executive office a register for the registration and registration of transfers of Notes. The name and address of each holder of one or more Notes,

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each transfer thereof and the name and address of each transferee of one or more Notes shall be registered in such register. Prior to due presentment for registration of transfer, the Person in whose name any Note shall be registered shall be deemed and treated as the owner and holder thereof for all purposes hereof, and the Company shall not be affected by any notice or knowledge to the contrary. The Company shall give to any holder of a Note that is an Institutional Investor promptly upon request therefor, a complete and correct copy of the names and addresses of all registered holders of Notes.

Section 13.2. Transfer and Exchange of Notes. Upon surrender of any Note to the Company at the address and to the attention of the designated officer (all as specified in Section 18(iii)), for registration of transfer or exchange (and in the case of a surrender for registration of transfer accompanied by a written instrument of transfer duly executed by the registered holder of such Note or such holder’s attorney duly authorized in writing and accompanied by the relevant name, address and other information for notices of each transferee of such Note or part thereof), within ten Business Days thereafter, the Company shall execute and deliver, at the Company’s expense (except as provided below), one or more new Notes (as requested by the holder thereof) in exchange therefor, in an aggregate principal amount equal to the unpaid principal amount of the surrendered Note. Each such new Note shall be payable to such Person as such holder may request and shall be substantially in the form of Exhibit 1 . Each such new Note shall be dated and bear interest from the date to which interest shall have been paid on the surrendered Note or dated the date of the surrendered Note if no interest shall have been paid thereon. The Company may require payment of a sum sufficient to cover any stamp tax or governmental charge imposed in respect of any such transfer of Notes. Notes shall not be transferred in denominations of less than $100,000, provided that if necessary to enable the registration of transfer by a holder of its entire holding of Notes, one Note may be in a denomination of less than $100,000. Any transferee, by its acceptance of a Note registered in its name (or the name of its nominee), shall be deemed to have made the representation set forth in Section 6.2.

Section 13.3. Replacement of Notes. Upon receipt by the Company at the address and to the attention of the designated officer (all as specified in Section 18(iii)) of evidence reasonably satisfactory to it of the ownership of and the loss, theft, destruction or mutilation of any Note (which evidence shall be, in the case of an Institutional Investor, notice from such Institutional Investor of such ownership and such loss, theft, destruction or mutilation), and

(a) in the case of loss, theft or destruction, of indemnity reasonably satisfactory to it ( provided that if the holder of such Note is, or is a nominee for, an original Purchaser or another holder of a Note with a minimum net worth of at least $100,000,000 or a Qualified Institutional Buyer, such Person’s own unsecured agreement of indemnity shall be deemed to be satisfactory), or

(b) in the case of mutilation, upon surrender and cancellation thereof,

within ten Business Days thereafter, the Company at its own expense shall execute and deliver, in lieu thereof, a new Note, dated and bearing interest from the date to which interest shall have been paid on such lost, stolen, destroyed or mutilated Note or dated the date of such lost, stolen, destroyed or mutilated Note if no interest shall have been paid thereon.

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SECTION 14. PAYMENTS ON NOTES.

Section 14.1. Place of Payment. Subject to Section 14.2, payments of principal, Make-Whole Amount, if any, and interest becoming due and payable on the Notes shall be made in New York, New York at the principal office of Bank of New York Mellon in such jurisdiction. The Company may at any time, by notice to each holder of a Note, change the place of payment of the Notes so long as such place of payment shall be either the principal office of the Company in such jurisdiction or the principal office of a bank or trust company in such jurisdiction.

Section 14.2. Home Office Payment. So long as any Purchaser or its nominee shall be the holder of any Note, and notwithstanding anything contained in Section 14.1 or in such Note to the contrary, the Company will pay all sums becoming due on such Note for principal, Make-Whole Amount, if any, and interest by the method and at the address specified for such purpose below such Purchaser’s name in Schedule A , or by such other method or at such other address as such Purchaser shall have from time to time specified to the Company in writing for such purpose, without the presentation or surrender of such Note or the making of any notation thereon, except that upon written request of the Company made concurrently with or reasonably promptly after payment or prepayment in full of any Note, such Purchaser shall surrender such Note for cancellation, reasonably promptly after any such request, to the Company at its principal executive office or at the place of payment most recently designated by the Company pursuant to Section 14.1. Prior to any sale or other disposition of any Note held by a Purchaser or its nominee, such Purchaser will, at its election, either endorse thereon the amount of principal paid thereon and the last date to which interest has been paid thereon or surrender such Note to the Company in exchange for a new Note or Notes pursuant to Section 13.2. The Company will afford the benefits of this Section 14.2 to any Institutional Investor that is the direct or indirect transferee of any Note purchased by a Purchaser under this Agreement and that has made the same agreement relating to such Note as the Purchasers have made in this Section 14.2.

SECTION 15. EXPENSES, ETC.

Section 15.1. Transaction Expenses. Whether or not the transactions contemplated hereby are consummated, the Company will pay all costs and expenses (including reasonable attorneys’ fees of a special counsel and, if reasonably required by the Required Holders, local or other counsel) incurred by the Purchasers and each other holder of a Note in connection with such transactions and in connection with any amendments, waivers or consents under or in respect of this Agreement or the Notes (whether or not such amendment, waiver or consent becomes effective), including, without limitation: (a) the costs and expenses incurred in enforcing or defending (or determining whether or how to enforce or defend) any rights under this Agreement or the Notes or in responding to any subpoena or other legal process or informal investigative demand issued in connection with this Agreement or the Notes, or by reason of being a holder of any Note, (b) the costs and expenses, including

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financial advisors’ fees, incurred in connection with the insolvency or bankruptcy of the Company or any Subsidiary or in connection with any work-out or restructuring of the transactions contemplated hereby and by the Notes and (c) the costs and expenses incurred in connection with the initial filing of this Agreement and all related documents and financial information with the SVO provided , that such costs and expenses under this clause (c) shall not exceed $3,500. The Company will pay, and will save each Purchaser and each other holder of a Note harmless from, all claims in respect of any fees, costs or expenses, if any, of brokers and finders (other than those, if any, retained by a Purchaser or other holder in connection with its purchase of the Notes).

Section 15.2. Survival. The obligations of the Company under this Section 15 will survive the payment or transfer of any Note, the enforcement, amendment or waiver of any provision of this Agreement or the Notes, and the termination of this Agreement.

SECTION 16. SURVIVAL OF REPRESENTATIONS AND WARRANTIES; ENTIRE AGREEMENT.

All representations and warranties contained herein shall survive the execution and delivery of this Agreement and the Notes, the purchase or transfer by any Purchaser of any Note or portion thereof or interest therein and the payment of any Note, and may be relied upon by any subsequent holder of a Note, regardless of any investigation made at any time by or on behalf of such Purchaser or any other holder of a Note. All statements contained in any certificate or other instrument delivered by or on behalf of the Company pursuant to this Agreement shall be deemed representations and warranties of the Company under this Agreement. Subject to the preceding sentence, this Agreement and the Notes embody the entire agreement and understanding between each Purchaser and the Company and supersede all prior agreements and understandings relating to the subject matter hereof.

SECTION 17. AMENDMENT AND WAIVER.

Section 17.1. Requirements. This Agreement and the Notes may be amended, and the observance of any term hereof or of the Notes may be waived (either retroactively or prospectively), with (and only with) the written consent of the Company and the Required Holders, except that (a) no amendment or waiver of any of the provisions of Section 1, 2, 3, 4, 5, 6 or 21 hereof, or any defined term (as it is used therein), will be effective as to any Purchaser unless consented to by such Purchaser in writing, and (b) no such amendment or waiver may, without the written consent of the holder of each Note at the time outstanding affected thereby, (i) subject to the provisions of Section 12 relating to acceleration or rescission, change the amount or time of any prepayment or payment of principal of, or reduce the rate or change the time of payment or method of computation of interest or of the Make-Whole Amount on, the Notes, (ii) change the percentage of the principal amount of the Notes the holders of which are required to consent to any such amendment or waiver, or (iii) amend any of Sections 8, 11(a), 11(b), 12, 17 or 20.

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Section 17.2. Solicitation of Holders of Notes.

(a) Solicitation. The Company will provide each holder of the Notes (irrespective of the amount of Notes then owned by it) with sufficient information, sufficiently far in advance of the date a decision is required, to enable such holder to make an informed and considered decision with respect to any proposed amendment, waiver or consent in respect of any of the provisions hereof or of the Notes. The Company will deliver executed or true and correct copies of each amendment, waiver or consent effected pursuant to the provisions of this Section 17 to each holder of outstanding Notes promptly following the date on which it is executed and delivered by, or receives the consent or approval of, the requisite holders of Notes.

(b) Payment. The Company will not directly or indirectly pay or cause to be paid any remuneration, whether by way of supplemental or additional interest, fee or otherwise, or grant any security or provide other credit support, to any holder of Notes as consideration for or as an inducement to the entering into by any holder of Notes of any waiver or amendment of any of the terms and provisions hereof unless such remuneration is concurrently paid, or security is concurrently granted or other credit support concurrently provided, on the same terms, ratably to each holder of Notes then outstanding even if such holder did not consent to such waiver or amendment.

Section 17.3. Binding Effect, etc. Any amendment or waiver consented to as provided in this Section 17 applies equally to all holders of Notes and is binding upon them and upon each future holder of any Note and upon the Company without regard to whether such Note has been marked to indicate such amendment or waiver. No such amendment or waiver will extend to or affect any obligation, covenant, agreement, Default or Event of Default not expressly amended or waived or impair any right consequent thereon. No course of dealing between the Company and the holder of any Note nor any delay in exercising any rights hereunder or under any Note shall operate as a waiver of any rights of any holder of such Note. As used herein, the term “this Agreement” and references thereto shall mean this Agreement as it may from time to time be amended or supplemented.

Section 17.4. Certain Notes Deemed Not to be Outstanding. Solely for the purpose of determining whether the holders of the requisite percentage of the aggregate principal amount of Notes then outstanding approved or consented to any amendment, waiver or consent to be given under this Agreement or the Notes, or have directed the taking of any action provided herein or in the Notes to be taken upon the direction of the holders of a specified percentage of the aggregate principal amount of Notes then outstanding, Notes directly or indirectly owned by

(a) the Company or any of its Affiliates or

(b) any holder that has (i) agreed to transfer such Notes to the Company or any of its Affiliates and (ii) provided or agreed to provide, in respect of such Notes, such approval, consent or direction as a condition to such transfer shall be deemed not to be outstanding.

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SECTION 18. NOTICES.

All notices and communications provided for hereunder shall be in writing and sent (a) by telecopy if the sender on the same day sends a confirming copy of such notice by a recognized overnight delivery service (charges prepaid), or (b) by registered or certified mail with return receipt requested (postage prepaid), or (c) by a recognized overnight delivery service (with charges prepaid). Any such notice must be sent:

(i) if to any Purchaser or its nominee, to such Purchaser or nominee at the address specified for such communications in Schedule A , or at such other address as such Purchaser or nominee shall have specified to the Company in writing,

(ii) if to any other holder of any Note, to such holder at such address as such other holder shall have specified to the Company in writing, or

(iii) if to the Company, to the Company at its address set forth at the beginning hereof to the attention of Treasurer, or at such other address as the Company shall have specified to the holder of each Note in writing.

Notices under this Section 18 will be deemed given only when actually received.

SECTION 19. REPRODUCTION OF DOCUMENTS.

This Agreement and all documents relating thereto, including, without limitation, (a) consents, waivers and modifications that may hereafter be executed, (b) documents received by any Purchaser at the Closing (except the Notes themselves), and (c) financial statements, certificates and other information previously or hereafter furnished to any Purchaser, may be reproduced by such Purchaser by any photographic, photostatic, electronic, digital, or other similar process and such Purchaser may destroy any original document so reproduced. The Company agrees and stipulates that, to the extent permitted by applicable law, any such reproduction shall be admissible in evidence as the original itself in any judicial or administrative proceeding (whether or not the original is in existence and whether or not such reproduction was made by such Purchaser in the regular course of business) and any enlargement, facsimile or further reproduction of such reproduction shall likewise be admissible in evidence. This Section 19 shall not prohibit the Company or any other holder of Notes from contesting any such reproduction to the same extent that it could contest the original, or from introducing evidence to demonstrate the inaccuracy of any such reproduction.

SECTION 20. CONFIDENTIAL INFORMATION.

For the purposes of this Section 20, “Confidential Information” means information delivered to any Purchaser by or on behalf of the Company or any Subsidiary in connection with the transactions contemplated by or otherwise pursuant to this Agreement that is proprietary in

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nature and that was clearly marked or labeled or otherwise adequately identified when received by such Purchaser as being confidential information of the Company or such Subsidiary, provided that such term does not include information that (a) was publicly known or otherwise known to such Purchaser prior to the time of such disclosure, (b) subsequently becomes publicly known through no act or omission by such Purchaser or any Person acting on such Purchaser’s behalf, (c) otherwise becomes known to such Purchaser other than through disclosure by the Company or any Subsidiary or (d) constitutes financial statements delivered to such Purchaser under Section 7.1 that are otherwise publicly available. Each Purchaser will maintain the confidentiality of such Confidential Information in accordance with procedures adopted by such Purchaser in good faith to protect confidential information of third parties delivered to such Purchaser, provided that such Purchaser may deliver or disclose Confidential Information to (i) its directors, officers, employees, agents, attorneys, trustees and Affiliates (to the extent such disclosure reasonably relates to the administration of the investment represented by its Notes), (ii) its financial advisors and other professional advisors who agree to hold confidential the Confidential Information substantially in accordance with the terms of this Section 20, (iii) any other holder of any Note, (iv) any Institutional Investor to which it sells or offers to sell such Note or any part thereof or any participation therein (if such Person has agreed in writing prior to its receipt of such Confidential Information to be bound by the provisions of this Section 20), (v) any Person from which it offers to purchase any Security of the Company (if such Person has agreed in writing prior to its receipt of such Confidential Information to be bound by the provisions of this Section 20), (vi) any federal or state regulatory authority having jurisdiction over such Purchaser, (vii) the NAIC or the SVO or, in each case, any similar organization, or any nationally recognized rating agency that requires access to information about such Purchaser’s investment portfolio, or (viii) any other Person to which such delivery or disclosure may be necessary or appropriate (w) to effect compliance with any law, rule, regulation or order applicable to such Purchaser, (x) in response to any subpoena or other legal process, (y) in connection with any litigation to which such Purchaser is a party or (z) if an Event of Default has occurred and is continuing, to the extent such Purchaser may reasonably determine such delivery and disclosure to be necessary or appropriate in the enforcement or for the protection of the rights and remedies under such Purchaser’s Notes and this Agreement. Each holder of a Note, by its acceptance of a Note, will be deemed to have agreed to be bound by and to be entitled to the benefits of this Section 20 as though it were a party to this Agreement. On reasonable request by the Company in connection with the delivery to any holder of a Note of information required to be delivered to such holder under this Agreement or requested by such holder (other than a holder that is a party to this Agreement or its nominee), such holder will enter into an agreement with the Company embodying the provisions of this Section 20.

SECTION 21. SUBSTITUTION OF PURCHASER.

Each Purchaser shall have the right to substitute any one of its Affiliates as the purchaser of the Notes that it has agreed to purchase hereunder, by written notice to the Company, which notice shall be signed by both such Purchaser and such Affiliate, shall contain such Affiliate’s agreement to be bound by this Agreement and shall contain a confirmation by such Affiliate of the accuracy with respect to it of the representations set forth in Section 6. Upon receipt of such notice, any reference to such Purchaser in this Agreement (other than in this Section 21), shall be deemed to refer to such Affiliate in lieu of such original Purchaser. In the event that such

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Affiliate is so substituted as a Purchaser hereunder and such Affiliate thereafter transfers to such original Purchaser all of the Notes then held by such Affiliate, upon receipt by the Company of notice of such transfer, any reference to such Affiliate as a “Purchaser” in this Agreement (other than in this Section 21), shall no longer be deemed to refer to such Affiliate, but shall refer to such original Purchaser, and such original Purchaser shall again have all the rights of an original holder of the Notes under this Agreement.

SECTION 22. MISCELLANEOUS.

Section 22.1. Successors and Assigns. All covenants and other agreements contained in this Agreement by or on behalf of any of the parties hereto bind and inure to the benefit of their respective successors and assigns (including, without limitation, any subsequent holder of a Note) whether so expressed or not.

Section 22.2. Payments Due on Non-Business Days. Anything in this Agreement or the Notes to the contrary notwithstanding (but without limiting the requirement in Section 8.4 that the notice of any optional prepayment specify a Business Day as the date fixed for such prepayment), any payment of principal of or Make-Whole Amount or interest on any Note that is due on a date other than a Business Day shall be made on the next succeeding Business Day without including the additional days elapsed in the computation of the interest payable on such next succeeding Business Day; provided that if the maturity date of any Note is a date other than a Business Day, the payment otherwise due on such maturity date shall be made on the next succeeding Business Day and shall include the additional days elapsed in the computation of interest payable on such next succeeding Business Day.

Section 22.3. Accounting Terms. All accounting terms used herein which are not expressly defined in this Agreement have the meanings respectively given to them in accordance with GAAP. Except as otherwise specifically provided herein, (i) all computations made pursuant to this Agreement shall be made in accordance with GAAP, and (ii) all financial statements shall be prepared in accordance with GAAP. Notwithstanding anything in this Agreement to the contrary, for purposes of determining compliance with the financial covenants set forth in Sections 10.9, 10.10, and 10.11, any election by the Company to measure an item of Indebtedness using fair value (as permitted by Statement of Financial Accounting Standards No. 159 or any similar accounting standard) shall be disregarded and such determination shall be made instead using the outstanding principal amount of such Indebtedness.

Section 22.4. Severability. Any provision of this Agreement that is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall (to the full extent permitted by law) not invalidate or render unenforceable such provision in any other jurisdiction.

Section 22.5. Construction, etc. Each covenant contained herein shall be construed (absent express provision to the contrary) as being

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independent of each other covenant contained herein, so that compliance with any one covenant shall not (absent such an express contrary provision) be deemed to excuse compliance with any other covenant. Where any provision herein refers to action to be taken by any Person, or which such Person is prohibited from taking, such provision shall be applicable whether such action is taken directly or indirectly by such Person.

For the avoidance of doubt, all Schedules and Exhibits attached to this Agreement shall be deemed to be a part hereof.

Section 22.6. Counterparts. This Agreement may be executed in any number of counterparts, each of which shall be an original but all of which together shall constitute one instrument. Each counterpart may consist of a number of copies hereof, each signed by less than all, but together signed by all, of the parties hereto.

Section 22.7. Governing Law. This Agreement shall be construed and enforced in accordance with, and the rights of the parties shall be governed by, the law of the State of New York excluding choice of law principles of the law of such State that would permit the application of the laws of a jurisdiction other than such State.

Section 22.8. Jurisdiction and Process; Waiver of Jury Trial.

(a) The Company irrevocably submits to the non-exclusive jurisdiction of any New York State or federal court sitting in the Borough of Manhattan, The City of New York, over any suit, action or proceeding arising out of or relating to this Agreement or the Notes. To the fullest extent permitted by applicable law, the Company irrevocably waives and agrees not to assert, by way of motion, as a defense or otherwise, any claim that it is not subject to the jurisdiction of any such court, any objection that it may now or hereafter have to the laying of the venue of any such suit, action or proceeding brought in any such court and any claim that any such suit, action or proceeding brought in any such court has been brought in an inconvenient forum.

(b) The Company consents to process being served by or on behalf of any holder of Notes in any suit, action or proceeding of the nature referred to in Section 22.8(a) by mailing a copy thereof by registered or certified mail (or any substantially similar form of mail), postage prepaid, return receipt requested, to it at its address specified in Section 18 or at such other address of which such holder shall then have been notified pursuant to said Section. The Company agrees that such service upon receipt (i) shall be deemed in every respect effective service of process upon it in any such suit, action or proceeding and (ii) shall, to the fullest extent permitted by applicable law, be taken and held to be valid personal service upon and personal delivery to it. Notices hereunder shall be conclusively presumed received as evidenced by a delivery receipt furnished by the United States Postal Service or any reputable commercial delivery service.

(c) Nothing in this Section 22.8 shall affect the right of any holder of a Note to serve process in any manner permitted by law, or limit any right that the holders of any

-36-

of the Notes may have to bring proceedings against the Company in the courts of any appropriate jurisdiction or to enforce in any lawful manner a judgment obtained in one jurisdiction in any other jurisdiction.

(d) THE PARTIES HERETO HEREBY WAIVE TRIAL BY JURY IN ANY ACTION BROUGHT ON OR WITH RESPECT TO THIS AGREEMENT, THE NOTES OR ANY OTHER DOCUMENT EXECUTED IN CONNECTION HEREWITH OR THEREWITH.

[Remainder of page intentionally left blank; signature pages follow]

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If you are in agreement with the foregoing, please sign the form of agreement on a counterpart of this Agreement and return it to the Company, whereupon this Agreement shall become a binding agreement between you and the Company.

Signature Page to

Note Purchase Agreement

-S-1-

This Agreement is hereby accepted and agreed to as

of the date thereof.

METROPOLITAN LIFE INSURANCE COMPANY

METLIFE INSURANCE COMPANY OF CONNECTICUT

By: Metropolitan Life Insurance Company, for itself and as

investment manager for the above entity

Signature Page to

Note Purchase Agreement

-S-2-

This Agreement is hereby accepted and agreed to as

of the date thereof.

UNION FIDELITY LIFE INSURANCE COMPANY

By: MetLife Investment Advisors Company LLC, its

investment adviser

Signature Page to

Note Purchase Agreement

-S-3-

This Agreement is hereby accepted and agreed to as

of the date thereof.

JOHN HANCOCK LIFE INSURANCE COMPANY (U.S.A.)

Signature Page to

Note Purchase Agreement

-S-4-

This Agreement is hereby accepted and agreed to as

of the date thereof.

JOHN HANCOCK LIFE & HEALTH INSURANCE COMPANY

Signature Page to

Note Purchase Agreement

-S-5-

SCHEDULE A

INFORMATION RELATING TO PURCHASERS

Name and Address of Purchaser :

METROPOLITAN LIFE INSURANCE COMPANY

1095 Avenue of the Americas

New York, New York 10036-6796

Payments :

All payments on account of the Note shall be made by crediting in the form of bank wire transfer of Federal or other immediately available funds (identifying each payment as Southwest Gas Corp. 6.10% Senior Notes due 2041 Private Placement Number 844895 C#7¸ principal, interest, make-whole amount, or otherwise, and confirming principal balance):

For all payments other than scheduled payments of principal and interest, the Company shall seek instructions from the holder, and in the absence of instructions to the contrary, will make such payments to the account and in the manner set forth above.

Notices :

1. Send All Communications and Notices to :

METROPOLITAN LIFE INSURANCE COMPANY

Investments, Private Placements

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Director

Facsimile (973) 355-4250

in each case with a copy OTHER than with respect to deliveries of financial statements to:

METROPOLITAN LIFE INSURANCE COMPANY

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Chief Counsel-Securities Investments (PRIV)

Email: sec_invest_law@metlife.com

-Schedule A-1-

INFORMATION RELATING TO PURCHASERS

Name and Address of Purchaser :

METLIFE INSURANCE COMPANY OF CONNECTICUT

c/o Metropolitan Life Insurance Company

1095 Avenue of the Americas

New York, New York 10036-6796

Payments :

All payments on account of the Note shall be made by crediting in the form of bank wire transfer of Federal or other immediately available funds (identifying each payment as Southwest Gas Corp. 6.10% Senior Notes due 2041 Private Placement Number 844895 C#7¸ principal, interest, make-whole amount, or otherwise, and confirming principal balance):

For all payments other than scheduled payments of principal and interest, the Company shall seek instructions from the holder, and in the absence of instructions to the contrary, will make such payments to the account and in the manner set forth above.

Notices :

1. Send All Communications and Notices to :

METLIFE INSURANCE COMPANY OF CONNECTICUT

c/o Metropolitan Life Insurance Company

Investments, Private Placements

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Director

Facsimile (973) 355-4250

in each case with a copy OTHER than with respect to deliveries of financial statements to:

METLIFE INSURANCE COMPANY OF CONNECTICUT

c/o Metropolitan Life Insurance Company

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Chief Counsel-Securities Investments (PRIV)

Email: sec_invest_law@metlife.com

-Schedule A-2-

INFORMATION RELATING TO PURCHASERS

Name and Address of Purchaser :

UNION FIDELITY LIFE INSURANCE COMPANY

c/o Jane Kipper

5700 Broadmoor, Suite 1000

Mission, KS 66202

Payments :

All payments on account of the Note shall be made by crediting in the form of bank wire transfer of Federal or other immediately available funds (identifying each payment as Southwest Gas Corp. 6.10% Senior Notes due 2041 Private Placement Number 844895 C#7¸ principal, interest, make-whole amount, or otherwise, and confirming principal balance):

For all payments other than scheduled payments of principal and interest, the Company shall seek instructions from the holder, and in the absence of instructions to the contrary, will make such payments to the account and in the manner set forth above.

Notices :

1. Send All Communications and Notices to :

UNION FIDELITY LIFE INSURANCE COMPANY

c/o MetLife Investment Advisors Company LLC

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Director

Facsimile (973) 355-4250

in each case with a copy OTHER than with respect to deliveries of financial statements to:

UNION FIDELITY LIFE INSURANCE COMPANY

c/o MetLife Investment Advisors Company LLC

P.O. Box 1902

10 Park Avenue

Morristown, New Jersey 07962-1902

Attention: Chief Counsel-Securities Investments (PRIV)

Email: sec_invest_law@metlife.com

-Schedule A-3-

INFORMATION RELATING TO PURCHASERS

Name and Address of Purchaser :

JOHN HANCOCK LIFE INSURANCE COMPANY (U.S.A.)

c/o John Hancock Financial Services

197 Clarendon Street

Boston, MA 02116

Payments :

All payments on account of the Note shall be made by crediting in the form of bank wire transfer of Federal or other immediately available funds (identifying each payment as Southwest Gas Corporation 6.10% Senior Notes due 2041, Private Placement Number 844895 C#7¸ principal, interest, make-whole amount, or otherwise, and confirming principal balance):

For all payments other than scheduled payments of principal and interest, the Company shall seek instructions from the holder, and in the absence of instructions to the contrary, will make such payments to the account and in the manner set forth above.