Contract analysis

1. Chapter 43.160A RCW, as currently in effect (the "Enabling Act");

2. Board Resolution No. 2023-014, adopted by the Board of Directors of CSIA on May 9, 2023, certified by the Secretary to the Board as a true and correct copy;

3. The Master Indenture dated as of October 24, 2023, by and between CSIA and the Trustee;

4. The First Supplemental Indenture dated as of October 24, 2023, by and between CSIA and the Trustee;

5. The Revenue Pledge Agreement dated as of October 24, 2023, by and between CSIA and the Trustee;

6. The Tax Regulatory Agreement and Certificate executed by CSIA on October 15, 2023;

7. The Bond Purchase Agreement dated August 30, 2023, by and between CSIA and Meridian Capital Partners LLC, as representative of the underwriters named therein;

8. The Continuing Disclosure Agreement dated as of October 24, 2023, by and between CSIA and the Trustee, as Dissemination Agent;

9. The Escrow Deposit Agreement dated as of October 24, 2023, by and between CSIA and the Trustee, as Escrow Agent;

10. The Debt-Service Reserve Fund Surety Bond Agreement dated as of October 24, 2023 (Surety Policy No. OG-2023-MUN-4718), by and among CSIA, the Trustee, and Olympia Guaranty Insurance Corp.;

11. The Preliminary Official Statement dated June 26, 2023, relating to the Bonds, and the Final Official Statement dated September 5, 2023, relating to the Bonds (the "Official Statement");

12. The Certificate of Authorized Officer of CSIA, executed by Harold K. Nakamura, Executive Director, dated the date hereof;

13. The CFO's Certificate executed by Denise R. Whitford, Chief Financial Officer of CSIA, dated the date hereof;

14. The State Environmental Policy Act ("SEPA") Determination of Non-Significance issued by the Washington State Department of Ecology on September 12, 2022, relating to the water treatment facilities to be financed with the proceeds of the Bonds;

15. The National Pollutant Discharge Elimination System ("NPDES") Permit No. WA-004837-2 modification approved by the Washington State Department of Ecology on January 6, 2023;

16. Rating letters from Lakeshore Ratings Group, Inc. (assigning a long-term credit rating of "AA" with a stable outlook to the Bonds) and Pinnacle Credit Analytics, Inc. (assigning a long-term credit rating of "AA−" with a stable outlook to the Bonds), each dated July 28, 2023; and

17. Such other documents, certificates, instruments, records, and matters of law as we have deemed necessary or appropriate for purposes of rendering this opinion. Assumptions and Reliance In rendering the opinions set forth herein, we have made the following assumptions and have relied upon the following, without undertaking independent investigation or verification: We have assumed the genuineness of all signatures

1. Due Organization and Existence of CSIA. CSIA is a duly created and validly existing governmental instrumentality and public body corporate of the State of Washington, created and existing under and pursuant to Chapter 43.160A RCW. CSIA has full legal right, power, and authority under the Enabling Act to issue the Bonds, to execute and deliver the Bond Documents to which it is a party, and to carry out and perform

2. Due Authorization. The issuance of the Bonds and the execution and delivery of each of the Bond Documents by CSIA have been duly authorized by all necessary action on the part of CSIA, including the adoption of Board Resolution No. 2023-014 by the Board of Directors of CSIA on May 9, 2023, in accordance with the Enabling Act and all applicable procedural requirements. All conditions precedent to such authorization

3. Valid Issuance and Binding Obligation. The Bonds have been duly authorized, executed, issued, and delivered by CSIA and constitute valid and legally binding special, limited obligations of CSIA, enforceable against CSIA in accordance with their terms. The Bonds are payable solely from and secured by a lien on and pledge of the Net Pledged Revenues, as such term is defined in the Indenture and the Revenue Pledge Ag

4. Validity of Indenture and Bond Documents. The Indenture (consisting of the Master Indenture and the First Supplemental Indenture), the Revenue Pledge Agreement, the Tax Agreement, the Continuing Disclosure Agreement, the Escrow Deposit Agreement, and the Surety Bond Agreement have each been duly authorized, executed, and delivered by CSIA and constitute valid and legally binding obligations of CSIA, enforceable ag

5. Validity and Perfection of Revenue Pledge. Under the Indenture and the Revenue Pledge Agreement, CSIA has validly pledged to the payment of the principal of, premium, if any, and interest on the Bonds the Net Pledged Revenues, which consist of (i) Wholesale Water Treatment Service Charges received by CSIA from the fourteen participating municipal water districts, as identified in the Indenture and the Revenue Pled

6. Federal Tax Exemption — Section 103 of the Internal Revenue Code. Under existing statutes, regulations, published rulings, and court decisions, and assuming continuing compliance by CSIA with certain covenants, representations, and conditions set forth in the Tax Regulatory Agreement and Certificate executed on October 15, 2023, interest on the Bonds is excludable from gross income of the owners thereof for federa

7. Washington State Tax. Under existing law of the State of Washington, the State of Washington does not impose a personal income tax on the income of individuals. Accordingly, we express no opinion regarding state income tax exemption as applied to interest on the Bonds. We note that we have not examined and express no opinion concerning the tax treatment of interest on the Bonds under the laws of any state other th

8. No Litigation Opinion. We have not been engaged to review, and have not reviewed, the status of any pending or threatened litigation, proceedings, or investigations that may affect CSIA, the Bonds, or the Bond Documents. We express no opinion as to the existence or absence of any pending or threatened litigation, arbitration, administrative proceeding, or governmental investigation affecting the validity or enforc