1. ESTIMATING METHOD AND USE OF LANDFILL SETTLEMENT by Michael L. Leonard, Sr., P.E., SCS Engineers, Inc. Kenneth J. Floom, Jr., P.E., Essentia Management, Inc. OII Landfill

2. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Permitting New Landfills-Why So Difficult? –Stringent Siting Criteria –Ever Increasing Land Values –Land Use Conflicts –Extensive Environmental Studies and Restrictions Vertical or Lateral Expansions—Also Limited American Canyon 1 Landfill

3. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Airspace As An Asset Requires Diligent Asset Management Loss Can Be Irrecoverable San Marcos Landfill

4. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Construction Methods Monitoring Airspace Use Settlement Predictions

5. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Waste Placement Compaction Cover Santamar Landfill

6. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Waste Placement –Initial Density—Ways to Improve and Monitor –Typical Achieved Values Overburden Soil Stockpiles Removal of Soil Cover American Canyon 2

7. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE What Is Density That Matters? Refuse Density, Total Density?? “Landfilling Density”—Defined As Weight of Refuse Divided By Total Air Space Consumed By Refuse, Cover Soil and Other Operations Soil

8. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE

10. Waste Settlement Over Time Settlement Mechanisms –Mechanical/Primary Compression –Biodegradation –Physical Creep Compression –Physical-Chemical/Corrosion –Interaction –Consolidation

11. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE LONG-TERM SETTLEMENT MECHANISM RELATIVE CONTRIBUTION TO LONG ‑ TERM SETTLEMENT BiodegradationHigh Physical Creep CompressionModerate Physical-Chemical/CorrosionLow InteractionGenerally Low; Potentially High in Localized Areas ConsolidationNone to Low

12. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Biodegradation Prediction is Key Model –S T = O x T R x S F –SF = a 1 /a T ; Settlement Factor –Where a 1 = future gas generation; a T = total gas generation –Q LFG = 0.029 G LFG (e -kN -e -kt ); gas generation

13. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE

14. Physical Creep Compression = Approx. 2% of fill thickness per log cycle of time

15. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE

17. Landfill Surface Generated By Model Is Input To Computer Data Base Siteworks, InRoads, SoftDesk Program Used To Compare to Final Permitted Waste Fill Surface Contours to Estimate Added Airspace Volume

18. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Application to Actual Landfill –Landfill Already at ½ Capacity –Estimated Tonnage Capacity 9,140,500 –With Settlement 10,100,000 –10 % Increase –Extended Remaining Site Life From 10.5 yrs to 11.5 years El Sobrante Landfill

19. INNOVATIVE LANDFILL OPERATIONS/OPTIMIZING AIRSPACE USE Conclusions/Recommendations –Use of Heavier Compaction Equipment –Maximize Use of Thin Daily Cover/ADCs –Apply Overburden via Soil Stockpiles –Limit Removal of Moisture by LFG Extraction –Add Moisture (as allowed): Liquid or Steam –Track and Update Average “Landfilling Density” and Settlement