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Mr. Himanshu Mehta, P. E. <br />21 November 2025 <br />Page 3 <br />Phase 3: Closure of Cell 1/2 <br />Phase 2 of this Project includes activities necessary to design a closure system for Cell 1/2, <br />consisting of an approximately 8.5 -acre partial final closure area along the northern -facing <br />slope and an approximately 11.1 -acre temporary closure along the southern/southwestern <br />facing slope. Geosyntec will subcontract Peavey Surveying to complete the existing <br />conditions survey of the identified closure locations. <br />The initial step in the closure design, Geosyntec will perform a preliminary stormwater evaluation <br />to compare pre- versus post -capping stormwater runoff and function of the existing facility <br />stormwater management system. A brief memorandum will be prepared and submitted to IRC <br />SWDD documenting the preliminary stormwater evaluation approach, assumptions, and results. <br />While the stormwater evaluation will also serve to guide design of the stormwater management <br />system design for the proposed final cover system, we do not anticipate generating a formal set of <br />calculations that would be required for an Environmental Resource Permit (ERP) application. No <br />ERP modification application is anticipated or assumed as part of the proposed scope of work. We <br />assume that a brief teleconference will be held with IRC SWDD to discuss the stormwater <br />evaluation summary memo. <br />Geosyntec will prepare a draft set of closure design plan drawings. The drawings will depict <br />preliminary grading to prepare for placement of cover system materials, proposed gas management <br />features, proposed stormwater features (e.g., final cover drainage berms, down chutes) and <br />modifications to existing stormwater features (e.g., stormwater detention ponds and perimeter <br />drainage channels), if necessary. Details required to prepare subgrade, install cover system <br />components, and construct stormwater management features will also be developed as a part of <br />the draft design. The draft closure design drawings are assumed to include the following sheets: <br />1. Title Sheet; <br />2. General Notes; <br />3. Existing Site Conditions; <br />4. Subgrade Grading Plan; <br />5. Gas Management Plan; <br />6. Top of Final Cover Grading Plan; <br />7. Stormwater Management Plan; <br />8. Final Cover Details; <br />9. Gas Management Details; and <br />10. Stormwater Management Details. <br />NCP2525235\IRC Partial Closure & GCCS Evaluation <br />engineers I scientists I innovators <br />