A Comparison of the Hydraulic Properties of Tubular and Geonet Drainage Geocomposites Considering Landfill Leachate Conditions

Eric Steinhauser, Sanborn, Head & Associates Inc., Concord, NH, USA Stephan Fourmont, Afitex-Texel Geosynthetics, Ste Marie, QC, Canada

The Sagamore, Bolton Landing, New York, May 17, 2016

Outline

Leachate collection system (LCS) refresher

Hydraulic considerations for LCS design Commonly used construction materials Experience with an alternative drainage

geocomposite Recent comparison testing of drainage

geocomposites Design considerations

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Leachate Collection

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Question #1

What is the purpose of the leachate collection and removal system? Answer: Effectively remove leachate from the landfill. Must be designed so that, during typical operations, the head on the primary liner system is no greater than 1 foot.

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LCS Design

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Current NYS requirements Part 360-2.13 (g), (l), (m), & (n)

According to GRI White Paper #14, the geomembrane should be protected from the overlying sand.

Drainage Geocomposite Transmissivity = 1 ft × 1×10-2 cm/s

LCS Design

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Proposed NYS requirements Part 363-6.6 (a) (3); 9; 11; & 12

Slope k (min.) Component

≤ 10% 0.1 cm/s 1.0 cm/s

upper 12 in. lower 12 in.

>10% 0.1 cm/s 24 in.

Geocushion

Protective Soil k values If a drainage geocomposite is used, the hydraulic flow capacity calculations must include a Factor of Safety of at least 10!

Does this include the design reduction factors?

During operation

Rainfall retention / evaporation Leachate from the waste

Quantity of liquid drained by the Leachate Collection System (LCS)

Immediately after construction 100% rain to the LCS No leachate

Leachate generation

After closure

“no” infiltration Leachate from the waste

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Quantity of liquid drained by the LCS

Leachate generation

18 months

Cover

0 m 25 m Waste Thickness

HELP model example from Thiel R., Narejo D. & Richardson G., GFR, April 2005 8

The drainage geocomposite needs to be operational for at least 18 months

Validation of the required flow capacity of the LCS at each stage: Immediately after construction During operation After geomembrane cover

Just after construction Operation I Operation II Cover

Load

Flow of leachate

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Leachate generation

Question #2

What are the steps to select a drainage geocomposite for the leachate collection system? Answer: 1. Calculated the estimated amount of leachate to

be generated for each operational scenario. 2. Calculated the design transmissivity for the

leachate generated and the cell configuration. 3. Calculated the required transmissivity based on

reduction factors and an overall factor of safety.

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Where: θreq or θspec= required or specified drainage geocomposite hydraulic

transmissivity (m2/s); FS = Factor of Safety; П(RF) = product of reduction factors (dimensionless) qh = impingement rate (m/s); L = flow length (m); β = slope (degrees).

Equation from: Giroud, J.P. Zornberg, J.G., Zhao, A., 2000, “Hydraulic Design of Geosynthetic and Granular Liquid Collection Layers,” Geosynthetics International, Special Issue on Liquid Collection Systems, Vol. 7, Nos. 4-6, pp. 285-380.

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Hydraulic Design Criteria ≥10?

According to GSI WP#4, Π(RF) ranges from 4.73 to 16.

θdesign

Drainage Layer Materials

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Reduction Factors

For drainage geocomposite design: RFIN: intrusion of the geotextile into the drainage core; RFCR: creep in compression; RFCC: chemical clogging; RFBC: biological clogging.

RFs should be applied to geotextile AND drainage core.

For LCS, RFCC and RFBC for the geotextile are critical.

RFs presented in GSI White Paper #4 (Geosynthetic Institute, 2007)

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Question #3 Reduction factors? Published values or can the be evaluated in a laboratory setting? Answer: Both will work. Perform tests under design loading conditions with the proposed materials and extended testing time frame (100 hours). Consider specialty materials – those specifically made to combat reduction effects [e.g., biological clogging and creep]).

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Geonet Geocomposite

Geonet sandwiched between to geotextiles (typically nonwoven)

Geonet and be bi-planar or tri-planar

Design considerations: Geotextile intrusion into geonet Geonet crushing (creep) Biological / chemical impacts

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Geonet Geocomposites

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Tubular Geocomposite

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Perforated mini-pipes between to geotextiles (typically nonwoven)

Design considerations: Spacing of mini-pipes Biological / chemical impacts

How it Works

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Mechanical Behavior No creep & no geotextile intrusion over time and

under load (“Arching effect” when confined)

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Mechanical Behavior

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Mechanical Behavior Tubular drainage geocomposites do not loose

drainage capacity due to the weight of waste on it

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Biological Resistance

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DRAINTUBETM ACB: includes a non-leachable, silver based biocide treatment

22M sf 1M sf

2M sf

4M sf 0.7M sf

1.3M sf

0.6M sf

0.1M sf

International Experience

Leachate Collection System Projects

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Question #4

Is there any test data on how tubular drainage geocomposites perform with respect to landfill leachate? Answer: Yes! Testing programs were held in Morocco and France, and one is currently underway in the US (at the Geosynthetic Research Institute).

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Question #5 What is/are the standard(s) for transmissivity testing of drainage geocomposites? Answer: ASTM D4716 – Standard Test Method for Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant Head

GRI Test Method GC15 – Standard Test Method for “Determining the Flow Rate per Unit Width of the High Flow Component of Enhanced Flow Drainage Geocomposites”

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Testing Appartus

Geocomposite

Outlet

Water Reservoirs

Inlet

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Geocomposite

Sample Size: width – 300 mm (12 in.); length – 350 mm (14 in.)

ASTM D4716 Method

Works well for geonet drainage geocomposites

Underestimates the flow in tubular drainage geocomposites

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Modified Testing Apparatus

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Sample Size: width – 250 mm (10 in.); length – 250 mm (10 in.)

Testing: France & Morocco Behavior of the entire product was monitored

(geotextiles and tubes); Constant normal load of 100 kPa; Anaerobic conditions; cells saturated with fresh

leachate directly pumped from a landfill sump; Temperature maintained above 22°C (72°F); Same amount of leachate injected into each cell

~ 5.5 m3 (~ 1,453 gallons) over 18 months equivalent to a flow rate of 2×10-6 m3/s/m2 (~3×10-3 gpm/ft2); and

Nine simultaneous tests: Three each using two different anti-biological geotextiles; and One of gravel only.

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Modified Testing Device

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ACB #1 ACB #2 Gravel

Gravel: washed, 20 to 40 mm aggregate, k ~ 1 cm/s

Test Results

Tubluar drainage geocomposite similar behavior as gravel over the time.

Neither the geotextile filter nor the tube clogged during the 18-month test program.

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Test Results - ACBs

0.00

0.10

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0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

0 100 200 300 400 500 600

Res

idua

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tem

Per

mea

bilit

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Elapsed Time (days)

DRAINTUBE ACB (France)

DRAINTUBE ACB (Morocco)

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Recent Test Program US test program at the GRI is similar to that performed in France & Morocco, but:

Modeling aerobic conditions (cells are allowed to empty [i.e., falling head test]);

150 mm of sand above the products; 2 types of ACB filters tested; and A 7.6-mm [300-mil] thick biaxial geonet drainage

geocomposite was tested.

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Recent Test Program

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Sand

Leachate

6 in

.

Test Results: Aerobic vs. Anaerobic

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110%

0 100 200 300 400 500 600 700

Res

idua

l Sys

tem

Per

mea

bilit

y

Elapsed Time (days)

DRAINTUBE ACB (USA)

DRAINTUBE ACB Anaerobic (France, Morocco)

Test Results: Tubular/Geonet

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110%

0 100 200 300 400 500 600 700

Res

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tem

Per

mea

bilit

y

Elapsed Time (days)

DRAINTUBE ACB (USA)

300mil Geonet geocomposite

Design Example LCS geocomposite design example (see: Thiel R., Narejo D., & Richardson G., GFR, April 2005)

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Drainage length = 45 m (~148 ft) Base slope = 4% Loading and Impingement Rate:

After Construction 50 kPa (~12 feet of waste) 5×10-7 m/s

During Operation I 250 kPa (~60 feet of waste) 1×10-7 m/s

During Operation II 500 kPa (~120 feet of waste) 3×10-8 m/s

Closure 550 kPa

(~130 feet of waste, plus cover)

1×10-9 m/s

Stage σ θdesign FSD RFIN RFCR RFCC RFBC θspec θ100 θ100/θspec

After construction 50 kPa 100% 5.00E-07 5.63E-04 2 1.0 1.0 1.5 1.0 1.69E-03 2.00E-03 1.2During operation I 250 kPa 20% 1.00E-07 1.13E-04 3 1.0 1.0 6.75E-04 2.00E-03 3.0During operation II 500 kPa 6% 3.00E-08 3.38E-05 3 1.0 1.0 2.03E-04 2.00E-03 9.9Cover 550 kPa 0.2% 1.00E-09 1.13E-06 3 1.0 1.0 1.35E-05 2.00E-03 148.1

Stage σ θdesign FSD RFIN RFCR RFCC RFBC θspec θ100 θ100/θspec

After construction 50 kPa 100% 5.00E-07 5.63E-04 2 1.3 1.1 1.5 1.0 2.41E-03 2.50E-03 1.0During operation I 250 kPa 20% 1.00E-07 1.13E-04 3 1.5 1.4 2.13E-03 2.00E-03 0.9During operation II 500 kPa 6% 3.00E-08 3.38E-05 3 2.0 2.0 1.62E-03 1.30E-03 0.8Cover 550 kPa 0.2% 1.00E-09 1.13E-06 3 2.0 2.0 5.40E-05 1.30E-03 24.1

3.04.04.0

Design with DRAINTUBE ACB1 D25 geocomposite

2.02.04.0

Design with 7.6 mm thick (300 mil) geonet geocompositeqi

qi

Design Example LCS geocomposite design example (see: Thiel R., Narejo D. & Richardson G., GFR, April 2005)

Tubular drainage geocomposite meets the design requirements even with a smaller index transmissivity than the geonet drainage geocomposite.

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Question #6

How should NYS DEC’s proposed Factor of Safety of 10 be applied to the design of drainage geocomposites, especially considering the material test data and consideration of Reduction Factors? Answer: ?

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Appropriated for both liquid and gas flow in geonet and tubular geocomposites, and gravel.

Developed at Joseph Fourier University (Grenoble, France).

Validated by Laboratoire Régional des Ponts et Chaussées, Nancy, France)

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Design with LYMPHEA

Take Aways

Select a LCS drainage geocomposite based on product- and case-specific data.

Reduction factors are product and case specific.

Tubular drainage geocomposite experience: since 2001 in Europe and North Africa for LCS;

and since 2011 in the US and Canada for LFG

collection and cover system drainage.

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Take Aways

Test data indicates that tubular drainage geocomposites: behave as well as or better than geonet

drainage geocomposites and gravel; and require smaller RFs than their geonet cousins,

especially when the anti-biological geotextile component is used.

A formal report of the GRI test program to be published at Geotechnical Frontiers 2017.

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Questions?

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Thank you for your attention.

Eric Steinhauser, Sanborn, Head & Associates Inc., Concord, NH, USA esteinhauser@sanbornhead.com Stephan Fourmont, Afitex-Texel Geosynthetics, Ste Marie, QC, Canada sfourmont@draintube.net

The Sagamore, Bolton Landing, New York, May 17, 2016