Exhibit 10.10.6 O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] July 21, 1994 Mr. William L. Bardeen Senior Vice President and Group Executive Consumer Energy Services Group PECO Energy Company 2301 Market Street P.O. Box 8699 Philadelphia, PA 19101-8699 Re: Letter Agreement Regarding Amendment of the Energy Service Agreements between the Philadelphia Municipal Authority and O'BRIEN Philadelphia Cogeneration Inc. in Conjunction with the Execution of Economic Efficiency Rider Contracts Between the City of Philadelphia Water Department and PECO Energy Company. Dear Bill: This letter sets forth the terms and conditions agreed to by PECO Energy Company ("PECO") and O'BRIEN Environmental Energy, Inc. ("O'BRIEN") under which, (i) O'BRIEN will agree to seek amendments to the Energy Service Agreements ("ESAs") between the Philadelphia Municipal Authority ("PMA") and O'BRIEN Philadelphia Cogeneration Inc. ("OPCI") under which OPCI currently provides standby electric generating services for the City of Philadelphia Water Department ("PWD") at its Northeast and Southwest waste water treatment facilities, and, (ii) PECO will offer and agree to enter into new Economic Efficiency Rider contracts with the PWD that would provide the PWD with the same level of economic benefits the PWD would have otherwise received from OPCI under the ESAs. The agreed upon terms and conditions are as follows: 1. PECO will loan O'BRIEN $5.5 million (the "Loan") on August 5, 1995, the last date of O'BRIEN's final option period to repurchase the common stock of OPCI (the "Stock Repurchase") from OPC Acquisition, Inc. (OPCAI). O'BRIEN will use $5 million of the Loan proceeds or such lesser amount as may be mutually agreed to by O'BRIEN and OPCAI to purchase the OPCI common stock (the "Stock Repurchase Price") and will assign the OPCI common stock to PECO as collateral for the Loan, as described below. PECO will facilitate the Stock Repurchase by wining the Stock Repurchase Price directly to OPCAI on behalf of O'BRIEN. Until the Loan is repaid, O'BRIEN will make monthly payments of $116,000 (the Monthly PECO Loan Payment) to PECO as provided in Schedule 1 attached hereto. O'BRIEN may prepay the outstanding balance of the Loan at any O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] Mr. William L. Bardeen July 21, 1994 Page 2 time without penalty. As further collateral for the Loan, O'BRIEN promises to establish a lock-box arrangement with a bank, acceptable to PECO and paid for by O'BRIEN, as described in the addendum to Schedule 2 attached hereto, under which all service fees received by OPCI from PMA will be directly deposited and all OPCI obligations, including full payment to PECO, as provided in Schedule 1, are paid in accordance with the Order of Monthly Service Fee Distributions attached hereto as Schedule 2. Interest shall accumulate on any unpaid balance (the Unpaid Balance) until paid in full. If there are insufficient funds available in any month to make the total Monthly PECO Loan Payment, or if there are excess funds available in any month after all the obligations of Schedule 2 have been satisfied, the remaining principal amount shall be adjusted and the term of the Schedule 1 Loan Amortization Table shall be extended or shortened, as the case may be, to amortize the adjusted principal amount using a monthly payment of $116,000 and 12% annual interest rate. Further O'BRIEN will not sell, move, pledge, or otherwise further encumber the 22 megawatts of diesel fuel standby electric generating equipment sets (the "Gen Sets") currently leased by O'Brien Rental Services ("RENTAL") to OPCI and located on PWD property without either obtaining PECO's prior written approval or by repaying the Loan in full. Further,upon the effective date of this Letter Agreement, O'BRIEN will immediately use its best efforts to grant PECO a second lien or mortgage on the Gen Sets in an amount equal to any Unpaid Balance due on the Loan. O'BRIEN will use its best efforts to obtain the consent of the lenders who have a primary lien on the Gen Sets (the "Primary Lenders") if such consent is necessary to permit O'BRIEN to grant the second lien to PECO. O'BRIEN represents that, (i) as of the date of this Letter Agreement, the projected schedule of payments would result in a remaining balance of less than $600,000 that will be owed to the Primary Lenders on all of the Gen Sets as of August, 1998, and (ii) the original financing costs of the Gen Sets and related equipment were greater than $8 million. O'BRIEN will provide PECO with detailed schedules and other documents memorializing RENTAL's obligations to the Primary Lenders with respect to the Gen Sets upon request. 2. O'BRIEN will not sell or pledge the common stock of OPCI to any party other than PECO until the Loan is repaid in full, except that O'BRIEN may sell the common stock to OPCAI as provided in paragraph 5 below. 3. Subject to a right of first refusal on the sale of the OPC I common stock which OPCAI has pursuant to Section 5 of Annex 11 to the Stock Purchase Agreement by and among OPCAI and affiliates and O'BRIEN dated November 12, 1993 (the "OPCAI Agreement"), after O'BRIEN has acquired the OPCI common stock, O'BRIEN shall grant PECO an exclusive option to acquire the OPCI common stock for the sum of $3 million, which option PECO must exercise when, and only if, all of the following conditions are satisfied: (1) O'BRIEN and the PMA execute amended ESAs that include at least the terms O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] Mr. William L. Bardeen July 21, 1994 Page 3 described below in paragraph 10, and the ESAs are acceptable to PECO; (2) PECO and the PWD execute Economic Efficiency Rider Contracts (the "EER contracts"), as described below in paragraphs 7 and 8; (3) O'BRIEN and PECO execute a transfer agreement (the "Transfer Agreement"), as described below in paragraph 1 0; and (4) PECO pays the difference between $9.5 million and the then current balance on the Loan to O'BRIEN and deems the Loan satisfied in full. 4. After O'BRIEN has acquired the common stock of OPCI, PECO shall have the right to tender an offer to purchase the OPCI common stock for $3 million (the "Offer"), which offer shall be subject to the conditions described above in paragraph 3. 5. If OPCAI, (i) exercises its rights to match the Offer, (ii) pays O'BRIEN $3 million for the OPCI common stock in accordance with the OPCAI Agreement, and (iii) makes the Lease Buyout Payment of $6.5 million, O'BRIEN shall immediately repay the Loan in full from the proceeds of the payments received from OPCAI for the OPCI common stock and the Lease Buyout and shall do so by requesting that OPCAI wire directly to PECO an amount equal to the principal and interest due on the Loan. 6. If OPCAI does not exercise its right to match, as soon as practicable and at least thirty days after the date the Loan is executed, O'BRIEN and PECO shall contact PWD and other relevant City of Philadelphia representatives to seek PWD's agreement to an amendment of the ESAs as described in paragraph 3 (1) above, the Transfer Agreement described in paragraph 10 below, and the EER contracts as described in paragraph 7 below. O'BRIEN and its affiliates shall fully defend, indemnify, and hold PECO harmless from and against any losses or damages that PECO might suffer as the result of any legal action of any kind, if any, brought by OPCAI, or by any other person or entity making a claim based on the OPCAI Agreement, in connection with alleged violations of rights, or alleged breaches of obligations, established by the OPCAI Agreement, 7. PECO will offer EER contracts to the PWID for its Northeast and Southwest waste water treatment facilities that would provide the same level of economic benefits that the PWID would otherwise receive under the ESAs. The EER contracts will provide a discount on PECO's full Rate HT service to the PWD in a manner that is consistent with the requirements of PECO's EER Tariff and the Pennsylvania Public Utility Code. The combination of this discount and the timing of such discount will provide the same level of economic benefits that the PWD would have otherwise received at the PWID facilities from OPCI under the ESAs. O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] Mr. William L. Bardeen July 21, 1994 Page 4 8. The EER contracts may include provisions similar to those provisions relating to early termination contained in the "Term of Contract" section of the EER contract executed on June 30, 1994 between SmithKline Beecham Corporation and PECO if the PWD wishes to have such provisions included. 9. O'BRIEN and PECO shall cooperate to obtain PWD's agreement to the changes to the ESAs, to accept the transfer of obligations previously owed to the PWD by OPCI to O'BRIEN, and to induce the PWD to enter into the EER contracts on the terms and conditions described herein, and shall endeavor to share any additional burdens, economic or otherwise, which O'BRIEN and PECO deem reasonable and appropriate, to bring about PWD's agreement and participation. O'BRIEN shall have sole discretion to decide whether to accept any such burdens with respect to the amended ESAs, and PECO shall have sole discretion to decide whether to accept any such burdens with respect to the EER contracts. 10. The amendment to the ESAs shall include provisions that, (i) permit the PMA or PWD to enter into the EER contracts, and (ii) release O'BRIEN or an affiliate of O'BRIEN from its obligation to maintain and operate all diesel fuel standby electric generating equipment currently located on PWD property. The amendment to the ESAs and the Transfer Agreement between PECO and O'BRIEN will contain terms ensuring that, upon closing of those agreements and the EER contracts, (i) OPCI shall have no remaining obligations whatsoever to the PIVIA, the PWD, or to O'BRIEN and any of its affiliates, or to any other person or entity, and, (H) that O'BRIEN will assume any obligations that OPCI had to the PIVIA, the PWD or to O'BRIEN and any of its affiliates, or to any other person or entity, it being PECO's intent to take whatever actions that may be necessary to cause OPCI to cease to exist immediately following the execution of the amended ESAs, Transfer Agreement, and the EER contracts. 11. If the PMA fails to execute the amended ESAs and the EER contracts within 120 days after the date the Loan is made, PECO may issue a second offer to purchase the common stock according to the same terms and conditions as its first offer, as described above in paragraphs 3, 4 and 5. 12. On, or as soon as practicable after, the date on which there is no longer any possibility that the amended ESAs and EER contracts contemplated herein will be successfully negotiated and executed, O'BRIEN and RENTAL shall enter into a written security agreement (the "Security Agreement") with PECO that will obligate O'BRIEN and RENTAL to, within six (6) months of the date the ESAs are terminated (the "Final Repayment Date"), (i) pay to PECO the Unpaid Balance on the Loan plus accumulated interest or, (ii) cause RENTAL to sell such number of the Gen Sets as are required to pay the Unpaid Balance to PECO and any remaining obligations to the Primary Lenders, and, (iii) grant a security interest to PECO in the GEN SETS such that if O'BRIEN fails to pay the full amount of the Unpaid Balance by the Final Repayment Date, subject to any regulatory O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] Mr. William L. Bardeen July 21, 1994 Page 5 approvals that PECO deems necessary, O'BRIEN shall be obligated to cause RENTAL to assign RENTAL's full interest in all of the Gen Sets to PECO. The Security Agreement shall also provide, and O'BRIEN hereby promises, that PECO shall be entitled to recover any costs reasonably incurred by PECO or PECO's agent to sell the Gen Sets to satisfy the Loan from the net proceeds of any such sale and any balance remaining shall be returned to O'BRIEN. At the time O'BRIEN, RENTAL, and PECO enter into the Security Agreement, O'BRIEN and RENTAL shall execute whatever financing statements and other documents that PECO, in its sole judgment, deems necessary to enable PECO to perfect the security interest that the Security Agreement grants to PECO. 13. Should PECO, in its sole judgment, deem it necessary to obtain approval, from the Federal Trade Commission, the Federal Energy Regulatory Commission, Pennsylvania Public Utility Commission, or any other agency or governmental entity, to undertake any of the actions required by this Letter Agreement, O'BRIEN will undertake all actions that, in PECO's sole judgment, are necessary, including making all complementary or concurrent filings that may be required. PECO shall not be required to undertake or fulfill any obligation imposed by this Letter Agreement should an agency or other governmental entity disapprove of or forbid PECo from fulfilling the obligation. 14. O'BRIEN will manage and lead negotiations with the PWD, PIVIA, and, as appropriate, other City of Philadelphia officials, on the restructuring and amendment of the ESAs and shall consult PECO on strategy. PECO shall cooperate with O'BRIEN and shall attend meetings with O'BRIEN and City officials in support of O'BRIEN's negotiations consistent with the strategy. PECO shall not separately negotiate or maintain contact with the City or any other party involved with the ESAs, including OPCAI, Woodforde Energy, Inc., Mrs. Marsha Perelman or any of her affiliates or representatives, regarding any amendment of the ESAs or the provision of service under the EER contracts, except with the prior written approval of O'BRIEN. Except for initial telephone contacts to establish meeting dates and times, O'BRIEN shall not separately discuss with the PWID, the PIVIA, or other City officials, the EER contract provisions PECO has agreed to herein or the details of the EER contracts as the negotiations proceed. 15. Upon the execution of the amended ESAs, the Transfer Agreement, and the EER contracts contemplated herein, PECO will pay O'BRIEN the difference between $9.5 million and the then remaining principal amount and any accrued interest of the Loan owed to PECO by O'BRIEN and shall provide O'BRIEN with written certification that the Loan has been satisfied in full. 16. O'BRIEN represents to PECO that as of the date of this Letter Agreement, it knows of no outstanding claims against OPCI, and promises that, with respect to any claims that may be made or that accrue against OPCI between the date of this Letter Agreement and the date of the execution of the amended ESAs, the Transfer Agreement, and the EER contracts, O'BRIEN and its affiliates shall fully indemnify and hold PECO harmless from O'BRIEN ENVIRONMENTAL ENERGY [Letterhead] Mr. William L. Bardeen July 21, 1994 Page 6 and against any losses or damages, including attorney's fees and expenses incurred to defend against any such claims, that PECO might suffer as the result of any such claims should PECO ever obtain title to the OPCI stock as contemplated herein. As with our original restructuring proposal and in accordance with our Non- Disclosure Agreement, this Letter Agreement is hereby designated as "Confidential" by O'BRIEN and may not be disclosed to any other party for any purpose without O'BRIEN's or PECO's prior written permission. By signing below, both parties intend to be legally bound by the foregoing. Thank you for your consideration. Sincerely, ACCEPTED AND AGREED TO BY: /s/ Robert A. Shinn /S/ W. L. Bardeen Robert A. Shinn W. L. Bardeen Vice President for PECO Energy Company O'BRIEN Environmental Energy, Inc. DATE: 7/21/94 cc: cc: P. T. Eastman F. L. O'BRIEN, III L. Zalkin J. Cooperman Schedule 1 Loan Amortization Amount $5,500,000 Interest Rate/year 0.12 Monthly Payment 116,000 a. Unpaid b. Month Balance Payment Interest Principal 1 5,500,000 116,000 55,000 61,000 2 5,439,000 116,000 54,390 61,610 3 5,377,390 116,000 53,774 62,226 4 5,315,164 116,000 53,152 62,848 5 5,252,316 116,000 52,523 63,477 6 5,188,839 116,000 51,888 64,112 7 5,124,727 116,000 51,247 64,753 8 5,059,974 116,000 50,600 65,400 9 4,994,574 116,000 49,946 66,054 10 4,928,520 116,000 49,285 66,715 11 4,861,805 116,000 48,618 67,382 12 4,794,423 116,000 47,944 68,056 13 4,726,367 116,000 47,264 68,736 14 4,657,631 116,000 46,576 69,424 15 4,588,207 116,000 45,882 70,118 16 4,518,089 116,000 45,181 70,819 17 4,447,270 116,000 44,473 71,527 18 4,375,743 116,000 43,757 72,243 19 4,303,500 116,000 43,03S 72,965 20 4,230,535 116,000 42,305 73,695 21 4,156,841 116,000 41,568 74,432 22 4,082,409 116,000 40,824 75,176 23 4,007,233 116,000 40,072 75,928 24 3,931,306 116,000 39,313 76,687 25 3,854,619 116,000 38,546 77,454 26 3,777,165 116,000 37,772 78,228 27 3,698,936 116,000 36,989 79,011 28 3,619,926 116,000 36,199 79,801 29 3,540,125 116,000 35,401 80,599 30 3,459,526 116,000 34,595 81,405 31 3,378,122 116,000 33,781 82,219 32 3,295,903 116,000 32,959 83,041 33 3,212,862 116,000 32,129 83,871 34 3,128,990 116,000 31,290 84,710 35 3,044,280 116,000 30,443 85,557 36 2,958,723 116,000 29,587 86,413 Schedule 1, Loan Amortization Page 2 37 2,872,310 116,000 28,723 87,277 38 2,785,034 116,000 27,850 88,150 39 2,696,884 116,000 26,969 89,031 40 2,607,853 116,000 26,079 89,921 41 2,517,931 116,000 25,179 90,821 42 2,427,111 116,000 24,271 91,729 43 2,335,382 116,000 23,354 92,646 44 2,242,735 116,000 22,427 93,573 45 2,149,163 116,000 21,492 94,508 46 2,054,654 116,000 20,547 95,453 47 1,959,201 116,000 19,592 96,408 48 1,862,793 116,000 18,628 97,372 49 1,765,421 116,000 17,654 98,346 50 1,667,075 116,000 16,671 99,329 51 1,567,746 116,000 15,677 100,323 52 1,467,423 116,000 14,674 101,326 53 1,366,098 116,000 13,661 102,339 54 1,263,759 116,000 12,638 103,362 55 1,160,396 116,000 11,604 104,396 56 1,056,000 116,000 10,560 105,440 57 950,560 116,000 9,506 106,494 58 844,066 116,000 8,441 107,559 59 736,506 116,000 7,365 108,635 60 627,871 116,000 6,279 109,721 61 518,150 116,000 5,182 110,818 62 407,332 116,000 4,073 111,927 63 295,405 116,000 2,954 113,046 64 182,359 116,000 1,824 114,176 65 68,183 116,000 682 68,183 Unadjusted Term: 5.42 Years NOTE: Commencing September 20, 1994, and on the 20th day of each succeeding month during the term of the Loan, O'Brien will revise this Schedule 1 Loan Amortization Table in accordance with section 1 of the Letter Agreement and the provisions of Schedule 2 and forward the revised amortization table (the "Revised Schedule 1") to PECO for approval, such approval not to be unreasonably withheld. The Monthly PECO Loan Payment of $116,000 will remain a constant in the Revised Schedule 1, while the remaining Term, Unpaid Balance, Interest, and Principal payments in the revised Schedule 1 will be subject to adjustment. The following examples illustrate how the original and revised versions of Schedule 1 would be subject to change: A. If, based on Schedule 2, only $100,000 of the first month's payment is paid on time, then the Unpaid Balance for the second month will be increased by $16,000 to $5,455,000 and the Interest due for the second month will be $54,550. B. If no payment is made in the first month, then the balance due for the second month will be $5,555,000 and the interest due for the second month will be $55,550. C. If, based on Schedule 2, $130,000 is available and paid to PECO as payment in the first month, then the Unpaid Balance for the second month will be adjusted to $5,425,000 and the interest due for the second month will be $54,250. (a) Schedule 2 (b) Order of Monthly Distribution Payments 1. Primary Gen Set Lenders' Lease Payments. 2. An amount equal to O'BRIEN's Lease Margin as defined below plus the Operation & Maintenance Reimbursement of $25,000, such amount to be escalated each year by four (4) percent, to PECO Energy. 3. If applicable, the estimated Preferred Stockholder Dividend to the OPCI dividend reserve account. 4. The monthly PECO Loan Payment amount less the amount in line 2 above. 5. Operation & Maintenance Reimbursement of $25,000, such amount to be escalated each year by four (4) percent, to O'BRIEN. 6. Any remaining amount to PECO to further reduce the remaining principal amount of the loan. For purposes of this Schedule 2, O'BRIEN's Lease Margin, means $195,761 per month less the Primary Gen Set Lenders' Lease Payments. SCHEDULE 2 ADDENDUM LOCKBOX ARRANGEMENTS OPCI SERVICE FEES AND DISTRIBUTIONS As provided in section one of the Letter Agreement, upon the making of the Loan O'BRIEN will establish a Lockbox Account (the "Lockbox") with a bank (the "Bank"), acceptable to PECO and paid for by O'BRIEN, to receive and distribute OPCI service fees. The Bank will have standing instructions to follow the following procedures each month with respect to the flow of funds; 1. Monthly service fee checks will be remitted by the Philadelphia Municipal Authority ("PMA') directly to the Bank in the name of OPCI. These checks are typically received between the 10th and 12th day of each month. 2. As with PECO's own billing and payment schedule, there is a time lag (approximately 45 days) between the end of the applicable PECO billing period and the date the OPCI service fees are paid. While O'BRIEN, as the new holder of OPCI common stock, will be entitled to accrue dividends commencing August 6, 1994 (the day after the Stock Repurchase), the actual disbursement of the common stock dividend for the period August 6 through August 22, 1994 will not be available until October 12, 1994, and the common stock dividend accrued for the period August 22 through September 22, 1994 will not be available until November 12, 1994. 2. PECO, RENTAL and O'BRIEN will maintain a demand deposit account at the Bank during the term of the Loan. 3. On the 12th of each month, the Bank will automatically debit the account of OPCI and distribute payments in the amounts and in the order of the distribution categories shown in Schedule 2. Since the Preferred Stockholder Dividend (category number 4 on Schedule 2) is payable quarterly, if applicable and if funds are available, the Bank will debit the account of OPCI monthly in an amount estimated by O'BRIEN to be the then current month's share of the then current quarter's projected preferred stock dividend and deposit such amount into a separate dividend reserve account to be established at the Bank and controlled by OPCI. If applicable, the preferred stock dividend will be calculated in accordance with the formula described in a letter from O'BRIEN to OPCAI dated November 12, 1993 attached hereto as Schedule 3. 4. OPCI will be entitled to maintain a minimum monthly working capital, balance of $5,000 at all times during the term of the Loan.