1. ENGINEERING CHALLENGES OF SITING RENEWABLE ENERGY AT LANDFILLS Ronald Johnson, PE, GE Brownfields Conference 2011 Philadelphia, PA April 5, 2011 1

2. Presentation Outline Landfill Cover Systems Alternative Energy Facilities Engineering Challenges Future Considerations Flexible Panels, Tessman Road Landfill, San Antonio, Texas Landfill Gas Microturbine – New Mexico 2

3. Engineering imperative for alternative energy on landfill sites: Maintain the disposal facility integrity! 3

4. Landfill Cover Regulations Regulations dictate cover design requirements and performance standards for landfills Federal Regulations 40 CFR 258 – Municipal Solid Waste Landfills 40 CFR 264 – Hazardous Waste Landfills State Regulations LEACHATE REMOVAL PUMP PIPELINE TO LEACHATE STORAGE POND SUMP LINER SYSTEM ACTIVE AREA FINAL COVER INTERMEDIATE COVER W A S T E 4

5. Types of Landfill Covers 5

6. Alternative energy common to landfills Landfill Gas Solar Wind 6

7. Landfill Gas Collection of methane Local combustion or liquefaction Important component of compliance OLD – open candlestick flares NEW – LFG to LNG, Orange County, CA 7

8. Solar Recently used on landfills Lightweight, scalable, variety of systems Much lower power than LFGTE or wind Tracking solar PV panels, Nellis AFB, NV Fixed PV panels, MCB Camp Pendleton, CA 8

9. Types of Solar Systems 9

10. Wind Advantages of topography and land use Higher power output than solar Foundation system challenges LFGTE & Wind integration concept, Saskatoon, Canada 10

11. Engineering Challenges - Overview Anchorage Bearing Capacity Cover Interaction Wind Forces Settlement Drainage Access Landfill Gas Management 11

12. Anchorage Bearing Capacity Select foundation size and depth to ensure adequate load carrying capacity and tolerable settlement Liner System Interaction Seal cover system penetrations (e.g., geomembrane boots) Cannot penetrate the base liner Skid mounted – movable to accommodate periodic cover maintenance 12

13. Wind Forces Creates uplift forces that need to be accounted for by: ballasting with weights anchorage 13

14. Settlement Magnitude and rate of settlement is a function of: Climate Waste type, age, thickness Degree of compaction Leachate recirculation Can be 10% to 15% of waste thickness during post-closure period (typically, 30 years) Settlement continues for a very long time, but rate decreases with time Differential settlement can cause local depressions and concentrated stresses and strains 14 McClellan-Palomar Airport, Carlsbad, CA

15. Drainage Consider interaction with stormwater management structures (e.g., benches, down chutes, down drains, etc.) and their maintenance Reduce drainage concentrations Accommodate hydraulic changes 15

16. Access (Installation, Operation, and Maintenance) Consider construction loads (trucks, cranes) impact on cover integrity Operation and maintenance of solar system may require more access roads than typical for a landfill Flexibility needed to allow for landfill maintenance 16

17. Landfill Gas Management Consider operation and maintenance access needs of landfill gas system Lateral and header pipes connect to extraction wells 17

18. Future Considerations Brownfield sites provide opportunities for beneficial land use for alternative energy production. Continual improvement in LF and alternative energy technologies. Closure and disposal site development should contemplate energy production scenarios. 18