Geosynthetic Barriers for

Transcription

1 8 th International Conference on Geosynthetics Geosynthetic Barriers for Environmental Protection at Landfills by Edward Kavazanjian, Jr., USA Neil Dixon, United Kingdom Takeshi Katsumi, Japan Anthony Kortegast, New Zealand Peter Legg, South Africa Helmut Zanzinger, Germany Fulton School of Engineering 1

2 Geosynthetic Barriers for Environmental Protection at Landfills Outline Introduction Developments in Liner Technology Developments in Cover Technology Coastal Landfills Summary and Conclusions Fulton School of Engineering 2

3 Geosynthetic Barriers for Environmental Protection at Landfills Scope of presentation includes: Barrier layers for liners Barrier layers for covers Coastal landfills Not in scope, but important to barrier performance, includes: Drainage layers Protection layers 3

4 Geosynthetic Barriers for Landfills Landfill Liner Systems Single geomembranes Geomembranes / Low Permeability Soil Composite Barriers Compacted Soil or Geosynthetic Clay Liner (GCL) Low Permeability Layers Single and Double Liner Systems 4

5 Single Composite Liner System Permeability k > 10-4 m/s Permeability k < 1 x 10-9 m/s 5

6 Geosynthetic Barriers for Landfills Cover (Capping Systems) Systems Geomembranes Exposed or Covered Geosynthetic Clay Liners Composite Barriers 6

7 Composite Cover System 7

8 Coastal Landfills 8

9 Prior (Baseline) Work on Liners and Covers Bouazza, A, Zornberg, J.G., and Adams, D. Geosynthetics in Waste Containment Facilities: Recent Advances Proceedings of the 7th International Conference on Geosynthetics, Nice,

10 Developments in Liner Systems Adoption in developing countries Continued accumulation of evidence of effectiveness Diffusion control systems Reactive geomembranes Forced air systems Diffusion attenuation layers Electrical leak detection surveys 10

11 Asia/Pacific Landfills with Geosynthetic Composite Liner Systems Location Date Waste Barrier Layer Beijing, China 2003 MSW GM/GCL Guangdong, China 2003 MSW GM/GCL Kate Valley, New Zeal MSW GM/GCL/GM SinFu, Taiwan 2002 MSW GM/GCL Rayong, Thailand 2002 Industrial GM/GCL 11

12 Southern Africa Landfills with Geosynthetic Composite Liner Systems Location Date Waste Barrier Layer Kome, Chad 2002 Industrial GM/GCL Belabo, Cameroon 2002 MSW GM/GCL Kumasi, Ghana 2003 MSW GM/GCL GM Walvis Bay, Namibia 2000 Haz. GM/GCL Mavoco, Mozambique 2003 Haz. GM/Clay - GM 12

13 Field Surveys of Composite Liner Effectiveness Bonaparte et al. (2002) for US EPA Leak Detection System Flow Rates for Double Lined Landfills GeoSyntec Consultants (2004) for CIWMB Performance of Single Composite Liner Systems 13

14 Bonaparte et al. (2002) LDS Collection Rates from Double Liner Systems 0.3 m 0.9 m 14

15 Bonaparte et al. (2002) LDS Collection Rates (liters/hectares/day) Sand/Geomembrane/GCL Stage Initial Active Post-Closure Average Flow Minimum Flow Maximum Flow Sand/Geomembrane/Compacted Clay Average Flow Minimum Flow Maximum Flow

16 GeoSyntec (2004) Groundwater impacts at lined landfills due only to gas migration and construction defects Landfill gas compacted soil Landfill gas to groundwater Kavazanjian and Corcoran,

17 Diffusion Control Rowe (2005): Diffusion attenuation layer Aquatan (2004): Forced air through h leak detection system 17

18 Reactive Geomembranes Shin et al. (2005): Geomembrane coated with Palladium / Iron (Pd/FE) 18

19 Liner Integrity Geomembrane mechanical defects Geomembrane aging Global l stability Local stability GCL seam separation 19

20 Leak Detection Surveys Test Wand Neoprene Pad Power Source 20

21 Construction Defect Frequency Hruby and Barrie (2003): 276 sites, > 3,000,000 square meters of geomembrane 11 defects / hectare No information on CQA Forget et al. (2005): 10 years of surveys 0.5 defects / hectare for strict CQA 16 defects / hectare without t CQA 21

22 Construction Defect Frequency Comparison Forget et al. (2005): defects / hectare for strict t CQA 16 defects / hectare without CQA Hruby and Barrie (2003): 11 defects / hectare (no information on CQA) US EPA HELP: leaks / hectare for good quality installation Dwyer (1998): Intentionally introduced 60 defects / hectare to simulate field conditions 22

23 Geomembrane Aging Anti-Oxidant Depletion Time Rowe (2005) > 500 yr at 15 o C years at typical MSW service temperatures (30 o -40 o C) (w/ leachate) 23

24 Global Stability 24

25 Global Stability Governed by interface shear strength Use residual strength of interface w/ lowest peak strength ( fuse concept) GCL - Internal Normal Stress = 69.0 kpa Textured Geomembrane/GCL ) Shea ar Stress (kpa) Minimum Peak Strength in System GCL/Drainage Geocomposite Residual Strength for System 10 5 Minimum Residual Strength in System Shear Displacement (mm) 25

26 GCL In-Plane (Internal) Strength Improvements in GCL In-Plane Strength Peak Strength c = 1.7 kpa, φ = 23 o Large Displacement Strength c = 6.2 kpa, φ = 17 o 26

27 Local Stability Overstressing, loss of function due to internal deformations Often ignored in practice Assessment requires numerical analysis Mitigation measures include Built-in preferential slip pp plane (e.g. Hong Kong) Benched slope with reinforced soil in-fill 27

28 Local Stability Modes Modes of Local Stability Failure (Jones and Dixon, 2005) Steep Slope Shallow Slope 28

29 Local Stability FLAC numerical analysis for geomembrane strain (Dixon et al., 2004) JOB TITLE :. FLAC (Version 4.00) (*10^1) LEGEND 18-Oct-04 16:02 step E+01 <x< 1.599E E+00 <y< 3.494E+01 Beam Plot Axial Strn. on Structure Max. Value # 2 (Beam ) E s,mnvzx;klcjhvpasd89f7q-ldosasdfl 1oijaspojfzxcnvxmnbz;kasjhdfqpow (*10^1) 29

30 Local Stability Benched slope with reinforced soil in-fill (Fowmes, et al, 2005) Clay Polystyrene panels Reinforced soil Liner and protection ti Waste Rock sub-grade 30

31 Local Stability JOB TITLE :. FLAC (Version 4.00) LEGEND 15-Apr-05 16:56 step E+01 <x< 6.223E E+00 <y< 3.817E+01 Max. shear strain increment 0.00E E E E E E E E-01 Liner strains for benched slope with reinforced soil in-fill (Fowmes, et al, 2005) (*10^1) Contour interval= 2.50E (*10^1) 31

32 GCL Seam Separation Observed at 5 landfills (at least) prior to waste placement 32

33 GCL Seam Separation Seam Separation Mitigation Measures Place waste as soon as possible Increase overlaps GCL initial water content < 20% Avoid double non-woven GCLs Use white geomembrane 33

34 Developments in Landfill Cover Systems Increased confidence in GCLs Better understanding of limitations, mitigation Chemically Modified GCLs Encapsulated GCLs Geomembrane aging 34

35 GCL Hydraulic Performance Issues Freeze e / Thaw Shrink / Swell / Desiccation Chemical Compatibility 35

36 Freeze / Thaw of GCLs Kraus et al. (1997) 36

37 Shrink / Swell / Desiccation Self-healing facilitated by sufficient overburden (0.6 1 m) Desiccation cracking of GCL (Melchior, 2002) 37

38 GCL Field Test Sections precipitation [mm/d] [mm/d] surface runoff drainage flow m/d] [m Bakersfield GCL test section (Mansour, 2001) [mm/d d] seepage through GCL Nuremberg GCL test section Henken-Mellies et al. (2002). 38

39 1E-06 Chemical Compatibility Some sodium to calcium transition may be unavoidable ficient k [m/s] 1E-07 log hydraulic conductivity coef 1E-08 1E-09 1E-10 initial swelling with aqua dest. permeation with CaCl 2 -solution "radical" ion exchange by initial swelling with salt solution 1E-11 "soft" ion exchange in situ during 1-3 years 0,01 0, log time [days] medium-heavy GCL after structural building with 15 kpa imposed load medium-heavy GCL after structural building with 20 kpa imposed load medium-heavy GCL, initial swelling medium-heavy GCL, no initial swelling heavy GCL, initial swelling heavy GCL, filled with Ca-bentonite bentonite, initial swelling heavy GCL, no initial swelling Evolution of GCL hydraulic conductivity with time (Egloffstein, 2002) 39

40 Chemically Modified GCLs Organobentonites for increased resistance to VOC flux Lorenzetti et al., 2005 Multi-swellable bentonite for increased resistance to cations Onikata et al., 1996 and 1999 Katsumi et al., 2001,

41 Encapsulated GCLs Developed for Geomembrane-backed GCLs (Giroud et al., 2004) Can also be used for GM GCL GM systems 41

42 Encapsulated GCLs Kate Valley Landfill, Canterbury, New Zealand Encapsulated GCL provides stability well beyond the liner system design life years 42

43 Cover System Degradation Geomembrane anti-oxidant depletion Reinforced GCL fiber degradation 43

44 Geomembrane Anti-Oxidant Depletion Tarnowski et al., 2005 Exposed geomembrane service life > 50 yrs Buried geomembrane service life > 300 yrs Results consistent with Rowe Oxidation Induction Time Oxidation Induction Time for the exposed geomembrane at Galing II Tarnowski et al.,

45 Reinforced GCL Fiber Degradation Potential for fiber failure in as little as 30 yrs at 20 o C under some conditions Arrhenius plot for needlepunched HDPE-GCLs (Thies et al., 2002) 45

46 Coastal Landfills A developing technology in densely populated coastal regions 46

47 Typical Caisson Barrier System Kamon and Inui (2002 ) 47

48 Influence of Geomembrane Defect Frequency Kamon and Inui (2002) 200 Defects / Hectare 2.5 Defects / Hectare 48

49 Influence of Geomembrane Backfill Kamon and Inui (2002) Backfill k = 1x10-1 cm/s Backfill k = 1x10-4 cm/s 49

50 Influence of Geomembrane Backfill Kamon and Inui (2002) 50

51 SUMMARY Use of geosynthetic barriers at landfills continuing to increase Data on effectiveness, limitations continuing to accumulate Composite barriers very effective for advection Geomembrane aging, local stability may be a concern Overburden pressure mitigates GCL cover desiccation Calcium cation exchange may be inevitable GCL seam separation also an issue 51

52 SUMMARY (Continued) New technologies continue to be developed Coastal landfills Reactive geomembranes Other diffusion control mechanisms Chemically modified GCLs Encapsulated GCLs 52

53 Acknowledgements My co-authors Neil Dixon Takeshi Katsumi Anthony Kortegast Peter Legg Helmut Zanzinger The organizers For the opportunity to prepare and present this paper For manuscript review comments The many people who s work was cited herein 53

54 8 th International Conference on Geosynthetics THANK YOU! 54