Subsurface Fire Identification, Assessment, and Mitigation (A Presentation of Selected Case Studies)

Transcription

1 Subsurface Fire Identification, Assessment, and Mitigation (A Presentation of Selected Case Studies) Raymond H. Huff, R.E.P.A. Vice President - SCS Engineers SWANA NW Symposium April 2015

2 Outline of Presentation Introduction Landfill Fire Information Case Studies Landfill #1 Canyon Fill SSO Landfill #2 Unique Source SSO Landfill #3 Australian Landfill SSO

3 Quick Point of Clarification Conventional Landfill Fires Surface Area-Wide Reactions Subsurface

4 Conventional Landfill Fires Surface Fires Result from hot objects in fill materials Coal, ashes, etc. May result from spontaneous combustion related to subsurface issues Usually detected based on visible smoke or flame

5 Conventional Landfill Fires Subsurface Fires Usually associated with air intrusion into the waste mass Over-Pulling wells, surface cracking, etc. Usually detected based on elevated well temperatures, development of sinkholes, smoke, etc.

6 Area-Wide Landfill Reactions Not a fire Start small, but can cover dozens of acres over time Can run deeper than landfill fires Does not appear to be triggered by GCCS But symptoms first appear there

7 Subsurface Elevated Accelerated Subsurface And Enhanced Temperature Oxidation there Landfill Combustion are Degradation Pyrolysis more Events Landfills Fires (SSO)

8 Subsurface Landfill Fires Often caused by overdrawn LFG extraction well Isolated, shallow, confined Elevated temps, stressed GCCS, isolated settlement around well Char, smoke, even flame Small-area, short-term fix Fix is usually enhanced cover

9 Identification of Subsurface Fires Field Observations Development of sinkholes or other substantial settlement over a short period of time Smoke in laterals/header (GCCS sites) or emanating from fissures (no GCCS) Combustion residue (ash) in extraction wells/laterals/headers Well Monitoring Data Increase in CO to levels in excess of 1,000 ppmv Wellhead temperatures in excess of 170 F Increase in GCCS temperatures (e.g., >140 F)

10 Assessment of Subsurface Fires Field Assessment (BE CAREFUL!!!) Identify extent of sinkholes/settlement area Smoke from fissures may not identify fire (e.g., chimney effect) Surface temperature variance Handheld thermometers or IR cameras may not be useful depending on ground cover and could be dangerous Installation of subsurface temperature probes

11 Assessment of Subsurface Fires Well Monitoring Data Key is to identify trends in gas composition, not to look for a threshold value Gas composition will change before temperature Evaluate the wells individually based on departure from baseline conditions if early in assessment

12 Remediation of Subsurface Fires Fire Suppression Removal of (air intrusion) is usually the easiest way to stop a fire Suppression Methods Addition of soil Suppression agents Carbon Dioxide (CO 2 ) Nitrogen (N 2 ) Foam

13 Landfill Case Studies Landfill #1

14 Landfill #1 - Background 34-Acre Canyon Fill Los Angeles, California Operated for 6 Years ( ) Currently Undeveloped No Perimeter Probes or GCCS Maximum Refuse Thickness of 170 Feet with up to 40 Feet of Cover in Some Areas Landfill Property Divided Amongst 4 Different Parties (who were not in communication) Residences Located Adjacent; Uphill and to the Northwest

15 Landfill #1 - Background

16 Landfill #1 - Background

17 Landfill #1 - Background

18 Landfill #1 - Background

19 Landfill #1 - Identification Fire Department Response to Citizen Complaints Local residents complained of Campfire Odors Surface fire identified and extinguished Source of fire unknown to Fire Department at the time Fire Department Created an Exclusion Zone Around area of surface fire due to low-level O 2 identified when placing meter in a surface fissure Fire Department Contacted Federal EPA Due to unknown nature of fire EPA Deferred to Local Enforcement Agency (LEA) LEA issues Notice and Order (N&O) to All Owners

20 Landfill #1 Initial Response Area of Initial Response

21 Landfill #1 - Assessment SCS Hired by Property Owner for Portion of Site Where Surface Fire Occurred 2/4 owners agreed to split costs Remaining 2 owners made no contact with LEA in response to N&O Initial Assessment Completed in Modified Level B PPE Due to Low O 2 Assessment Activities Field gas analysis for O2 Soil temperature analysis Localized landfill cover/settlement assessment

22 Landfill #1 - Assessment SCS Assessment Area Surface Cracking

23 Landfill #1 - Assessment A A

24 West-East Cross Section A A Settlement 24

25 West-East Cross Section A A Exhaust Pathway Air Intrusion Pathway Heat and Fuel 25

26 Landfill #1 - Remediation Site Cover Re-Work SCS brought in additional soils to fill in crack along western edge of landfill, along boundary with native bedrock Removal of flammable vegetation along slopes and worked entire western perimeter to ensure cracks were filled and combustion smothered Work Completed in 2003 No evidence of combustion since 2003 Current Status 24,000 ppmv CH 4 identified in surface emissions along former crack area

27 Landfill #1 - Remediation SCS Remediation Area

28 Landfill Case Studies Landfill #2

29 Landfill #2 - Background 33-Acre Shallow Canyon Fill San Diego, California Maximum refuse thickness of 25 feet Operated for 13 years ( ) Landfill Comprised of Three Separate Fill Units Two covered in asphalt; used for airport operations One unit located on runway approach and unimproved GCCS Consisting of 12 perimeter migration monitoring wells and 48 LFG extraction wells Landfill property owned by local municipality Businesses located on and adjacent to landfill

30 Landfill #2 - Background Area 3 Area 2 Area 1

31 Landfill #2 - Identification Surface Settlement Identified by Field Staff 50-Foot diameter, 3-foot deep depression Located in Area 3, used for runway approach Initial Subsurface Investigation In order to assess the potential for subsurface combustion, a temperature sensor string (thermocouple) was installed near center of depression 5 depths (4-, 8-, 12, 16-, and 20-feet below surface) CO monitored with field instrument during installation activities was in excess of 1,000 ppmv

32 Landfill #2 Assessment Initial Settlement Area

33 Landfill #2 - Assessment Initial Response 250 c.y. of soil immediately placed into depression to halt surface air intrusion Extraction wells in vicinity to settlement area taken offline Assessment Activities 19 additional multi-depth thermocouples installed over a 2-month period to track temperature trends over time 100 total data points (20 locations * 5 points per location) Historic data review identified possible storm drain alignment directly below settlement area

34 Landfill #2 Assessment Initial Settlement Area LFG Wells Storm Drain Alignment

35 Landfill #2 Assessment ft ft Temp ft Temp Contours

36 Landfill #2 Assessment

37 Landfill #2 Remediation CO 2 Injection 9, 2-inch, SCH 80 black steel pipes installed to a max depth of 32 feet bgs 37

38 Landfill #2 - Remediation Real-Time Monitoring During CO 2 injection, real-time data collected from network of 100 data points Real-Time telemetry tracking allowed ability to track effectiveness in-field and adjust strategy accordingly Iterative Process Two rounds of injection over a 2-week period Initial round involved smaller amount of CO 2, second round was larger

39 Landfill #2 Remediation CO 2 Injection Area Storm Drain Alignment

40 Landfill #2 Real-Time Results

41 Long-Term Results Probe TP-1 CO2 Injection Seal Drain ' -8' -12' -16' -20' 70 41

42 Landfill Case Studies Landfill #3

43 Landfill #3 - Background 27-Acre Pit Fill - Brooklyn, Victoria (Australia) Maximum refuse thickness of 150 feet Groundwater at 50 feet (lower 100 feet of waste are in liquid) Operated for 10 years ( ) GCCS Pilot System 8 shallow LFG wells located in northwest portion of site Leachate Sumps 10 dewatering/leachate sumps installed and during fill operations using Reinforced Concrete Pipe Landfill Closed with Only Daily Cover Residences Within 700 Feet

44 Landfill #3-1992

45 Landfill #3-2013

46 Landfill #3 - Background Leachate/Groundwater Sumps Seven Leachate Sumps Three Groundwater Sumps Installed a Base of Pit at Beginning of Fill Sump Construction 3-meter long sections 1.2-meter diameter Reinforced Concrete Pipe (RCP) Bell-Spigot Connections NOT GAS TIGHT

47 Landfill #3 Pilot Wells Sumps

48 Landfill #3 Identification

49 Landfill #3 - Identification July 2013 October 2013

50 Landfill #3 Identification Charring Smoke Cover Desiccation

51 Landfill #3 Identification

52 Landfill #3 Identification

53 Landfill #3 - Assessment Temperature Profiling Five thermocouples installed within each sump at 5- meter intervals Lowest thermocouple is in liquid Weekly Readings Since July 2013 Depths are Difficult to Verify Due to Sump Construction

54 Temperature Visualization

55 Landfill #3 - Assessment 10 Meter Temp Contours - March Meter Temp Contours - March 2015

56 Landfill #3 - Remediation Sinkholes - Hydrated Bentonite and Soil Backfill

57 Landfill #3 - Remediation Surface Fissures Soil Import and Grading

58 Landfill #3 - Remediation Settlement Areas Soil Import and Grading

59 Landfill #3 - Remediation Sumps Capping and Monitoring

60 Landfill #3 - Remediation

61 Landfill #3 - Remediation

62 Landfill #3 - Remediation

63 Landfill #3 - Remediation

64 Final Thoughts (we made it!)

65 Final Thoughts Landfill #1 Nature of fill (unique geology) was key to understanding nature of fire Landfill #2 Historic land use (storm drain) was key to understanding limited effect of remediation Landfill #3 Lack of final cap and no gas control on sumps during construction resulted in formation of a convection current Cessation of Air Intrusion is Key for Suppression