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Foothill Landfill Preliminary Plans December 21,2016 Page 2 of 2 - - --2.--- -Final-Cover-Dgai -T-he-Plans-assufrle-that-an-interim/foundation-(inter-mediate-c-over-)-iayer-is--___- anticipated to be in place at the time of final cover construction. The closure cost estimate excludes this layer in the foundation layer cover cost. This is not acceptable. Estimated closure costs are to include all activities yet to be completed at the time of preparation of the estimate. Since it is unknown(1)the quantity of intermediate cover that may be present at final closure(thickness initially placed, erosion, etc.)and (2)the quality of the material (not placed under final cover quality control conditions,wear over time, etc.), it is premature to presume that there will be sufficient quality and quantity of the material suitable for final cover. At the time of partial or final closure design and implementation,the suitability of any existing intermediate cover could be investigated at that time. The closure cost estimate must be revised to include the cost for the assumed in place material. 3. Final Cover Stability: There is no stability analysis of the final cover. While 27 CCR 21090(a) specifically requires slope stability analysis if final grades are steeper than 3:1 or a geosynthetic component is used in the final cover design, the'section does not exempt the design from slope stability analysis. Moreover,27 CCR 21145(a)requires the operator to ensure the integrity of final slopes under both static and dynamic conditions to protect public health and safety and prevent damage. Therefore,stability analysis on the most critical final cover slope interface (e.g.,soil/trash interface or internal soil interface)be run to demonstrate the stability of the final cover design. Since the previously analyzed global slope stability has shown the site to be stable (Factor of Safety> 1.5), the stability analysis may be simplified by either(1) demonstrating that the weakest final cover interface is more stable than the waste mass or(2)demonstrate that K,1KX is> 1.5. 4. Cost Estimates: Cost estimates shall be updated at each permit review or revision submittal and shall be based on costs the state may incur if the state would have to assume responsibility for corrective action due to the failure of the operator/owner to properly and adequately perform any or all of the activities. Updates of cost estimates shall be based on the current costs on a unit basis(unit costs). Cost estimate adjustments based only on inflation factors are not acceptable. The costs included as JTD Appendix I (Bullet 1 above)are for the annual inflation adjustment. These estimates do not meet the regulatory requirement for updated cost estimates at each permit review or revision application. The operator needs to submit updated cost estimates that are detailed and justified and reflect the potential state cost as required by 27 CCR§§21815, 21820, and 21840. 5. Postclosure Maintenance Costs: The postclosure maintenance cost estimate is to include the replacement cost for all capital items (e.g., landfill gas and ground water monitoring wells, drainage conveyances,fencing, etc.)at least once during the initial minimum 30-year postclosure maintenance period. In other words,the estimate is to account for replacement of all monitoring wells,fencing,drainage conveyance, etc. It is unclear if these costs are included in the estimate. The postclosure maintenance cost estimate must be revised to include the replacement costs,or alternatively, it can be indicated where these costs are already included in the estimate. Should you have any questions or comments concerning the above matter, please contact Diane Nordstrom-Lamkin or Michael Wochnick at(916)341-6448 or(916)341-6289, respectively. Alternatively, Closure staff may be reached by email at diane.nordstrom-lamkin@calrecyle.ca.gov or michael.wochnick@calrecycle.ca.gov. CC. Kevin Taylor,Manager,Permits and Assistance South Section Dave Otsubo,Supervisor,Permits and Assistance North Unit Elizabeth Felix,Financial Assurances Unit