Landfill Gas Monitoring Well Functionality at 20 California Landfills

1. Landfill Gas Monitoring Well Functionality at 20 California Landfills presented by: Raymond Huff, R.E.A. SCS Engineers July 15, 2008

2. Objectives • Determine Functionality of Gas Migration Monitoring Probes • Is monitoring data collected representative of actual soil gas conditions in vicinity of the probe • Based on Findings, Recommend Enhancements to Existing Regulations

3. Approach • 20 Landfills selected for inclusion in study • 10 in northern California • Clovis, Ukiah, Crazy Horse, Kiefer, Corral Hollow, Hillside, Buena Vista, Anderson, Redding/Benton, Red Bluff • 10 in southern California • Azusa, Bradley, City of HB, Olinda Alpha, Coyote Canyon, Upland, Milliken, South Chollas, South Miramar, Otay Landfill • 10 probes per site • A probe is a single monitoring point that may be located within a well containing multiple depth probes. • 190 Probes in study • 10 probes removed from study because their construction was outside of limits of the equipment (e.g. >100 feet deep)

4. Functionality Assessment Overview • Pre-Assessment Activities • Initial Condition Assessment • Gas Monitoring • Vacuum Testing • Video Borescope Inspection • Lithology Evaluation

5. Pre-Assessment Activities • Pre-Notification and On-Site Arrival • Landfill operator notified prior to assessment • Selection of Gas Probes • Determined on-site • Based on age, depth, and accessibility • Ambient Condition Assessment • Ambient atmospheric conditions recorded • Weather, barometric pressure, temperature, wind speed/direction • Recordkeeping

6. Initial Condition Assessment • Location Assessment • Available site maps were cross-checked against field location of probe • Probe Identification Assessment • Individual probes should be easily identifiable • Probehead Assembly Assessment • Gas monitoring port on every probe • Allows initial pressure monitoring • Surface Emissions Monitoring • Assessment of wellhead completion and seal

7. Gas Monitoring Assessment • Initial Pressure Readings • Probes with significant variation from ambient (e.g. <> 0 pressure) assumed to be functional • LFG Monitoring • CH4, CO2, O2, CO, and H2S • Ambient Oxygen Analysis • Probes with ambient (e.g. >20%) O2 may be subject to ambient air intrusion • Depth Trend Analysis • Generally, O2 should decrease with depth and CO2 should increase • Methane Concentration • Used to verify functionality more than non-functionality

8. Vacuum Testing • Known vacuum applied to each probe • Vacuum change over time (e.g. recovery) recorded • 120 second recovery period • Readings every 30 seconds

9. Video Borescope Inspection • Downhole video logging of each probe in study • Visual inspection of probe integrity and construction • Video data compared to probe construction logs

10. Lithology Evaluation • Video verified screened intervals compared to lithology logs • For closed landfills §20925(c)(1)(D) indicates that probe screened intervals should be placed, “preferentially adjacent to soils which are most conducive to gas flow”

11. Findings – Initial Conditions • Location • 1 out of 190 probes incorrectly marked on map • Identification • 15 out of 190 probes difficult to identify • Probehead Assembly • 10 out of 190 were missing caps • Surface Emissions Monitoring • 16 out of 190 had some surface emissions

12. Initial Conditions

13. Findings – Gas Monitoring • Initial Pressure • 113 out of 190 probes had 0 pressure • LFG Monitoring • No H2S or CO detected • Some ambient O2 levels • Ambient Oxygen Analysis • 37 out of 190 probes had ambient (>20%) O2 levels • Depth Trend Analysis • 21 out of 75 wells had increasing O2 with depth • Methane Concentration • 23 out of 190 probes had CH4 >5%* *Note: Not all probes included in study were perimeter compliance probes

14. Findings – Vacuum Testing • Vacuum recovery better for determining functionality, as opposed to determining non-functionality • Significant number of probes had quick vacuum recovery • Not necessarily indicative of a non-functional probe • Probes screened in highly permeable zone would recover quickly • No vacuum recovery indicative of clogged/flooded probe.

15. Findings – Video Borescope • Probe Construction Observations • Screened interval verification • Pipe connection observation • Threaded vs. screwed couplings • Probe Obstruction Observations • Soil, roots, insects, paper • Construction materials • Bentonite, nails, PVC shavings

16. Probe Construction Observations

17. Probe Obstruction Observations

18. Findings – Lithology Evaluation • Probes generally screened in coarse-grained lithologies • At sites where probes were screened in finer-grained lithologies, no more coarse-grained lithologies were present.

19. Functionality Determination • “Functional” for this study was based on a combination of observations including condition and location of screens, general condition of well and probe, presence of ambient air in the probe, flooding, and other factors. • Some probes identified as non-functional may easily be deemed “functional” with minimal effort • Change probehead assembly • Additional construction verification • Review of historic readings

20. Functionality Determination • 32% (61 out of 190) probes determined to be non-functional • Non-functional as determined by this study • 12 probes identified as “indeterminate” • Additional data needed to determine functionality • 117 probes identified as functional

21. Conclusions • Probe Identification • Proper labels are necessary for valid probe monitoring • Although 25 out of 190 were not properly labeled, only 4 of these were mis-labeled • Surface Emissions • Generally surface emissions around the wells were not found to be of issue

22. Conclusions (cont.) • Probe Construction • Use of screws for pipe coupling is questionable • Probe wellheads were generally designed to function, with a few exceptions • Depth to water and screened interval should be taken into account when designing/constructing probes • Durability of Materials • With limited exceptions, probe construction materials identified in this study were adequate • PVC, etc.

23. Recommendations • Probe identification • Individually labeled probes • Well ID • Relative depth (S, M, D) • Screened interval • Example: MP-1-S, 7-10’ • Probes should be constructed with longer screened sections • Covers lithology and reduces possibility for biofouling

24. Recommendations (cont.) • Probe Assembly • Threaded coupling preferred over slip-coupling and screwed/glued connections • Exceptions noted for wellhead • Probehead assemblies should contain a non-proprietary locking valve (labcock valve, quick connect, etc.) • Probes should be preferentially located away from dense vegetation • Avoid root intrusion where possible

25. Recommendations (cont.) • Development of a standard probe specification/construction detail • Length of screened interval, wellhead completion, etc. • Require certification of installed probes post-installation, not just during drilling • Include rationale for mid-depth probe placement based on lithology • Perform periodic (appx. Every 10 years) of probes in order to verify functionality

26. QuestionsandAnswers