Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Longevity of Geonets and Geotextiles”. This topic generated significant discussion with the main “take-aways” being listed below:

1.           Longevity of Geonets

·        Little performance specifications

·        No longer using an AOS requirement; no FOS

·        Civil v. Environmental grade geotextiles -

·        What is happening under the geomembrane?

·        Research – check embedment of geonet on GM without a cushion GT – when to transition to a composite

·        Industry moving to composites from sands and gravels – so check compatibility of nets with flexible GMs – Brian and Rohit webinar on net and 40 mil GM

 2.           Longevity of Geotextiles

·        Little performance specifications

·        No longer using an AOS requirement; no FOS

·        Civil v. Environmental grade geotextiles -

·        Are geotextiles chemically resistant to liquidsbeing contained?

·        Kerry Rowe – double composite liner system – GCLgeotextile decomposed

·        No specs to excavate and check the geonet andgeotextile

·        Intercell berm excavations look good –

·        Compatibility b/t net and GTs – Polyester & Polypropylene GTs -

·        Compatibility b/t net and GMs – use same resin for both – no spec requiring same resin as GM

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Leak Testing Mechanical Attachments

- Cannot conduct electronic leak locate survey near metalattachments because of interference so need some other type of testing ofattachments

- Place ballast tubes around penetration, inject airbelow geomembrane, soap the attachment, and watch for bubbles along or aroundattachment

- Thermal imaging – not tried yet but possibly effective onsunny day to measure cooler air being pumped below geomembrane and exiting atleak(s) along attachment

- Vacuum below the geomembrane in tank or attachment and listen for vacuum sound along attachment

- Vacuum Acoustic Leak Identification (VALID) method – apply vacuum between primary and secondary geomembranes and listen for vacuum soundalong attachments; tests both geomembranes; the top surface of the geomembrane is scanned with ultrasonic microphones that can detect distinctive sounds of a vacuum leak.

 - Smoke Test – smoke exits at attachment surrounded by ballast tubes

- Spark test with material embed but cannot be used at landfills and oil and gas sites

- Vacuum boxes for strips and corners but limited because not straight segments for box

- Dye test – divers places dye along attachment or concrete joint and see if dye disappears into attachment or crack (see video)

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• ASTM D6182-00 (2015) – Standard test method for flexibility and adhesion of finish on leather 
 
• ISO 32100: 2018 Rubber- or plastics-coated fabrics — Physical and mechanical tests — Determination of flex resistance by the flexometer method
 
• AS 4878.9-2001- Methods of Testing For Coated Fabrics - Determination Of Resistance To Damage By Flexing
 
• ISO 7854:1995 - Rubber- or plastics-coated fabrics — Determination of resistance to damage by flexing
 
• ASTM D2097 – Standard Test Method for Flex Testing of Finish on Upholstery Leather
 
• ASTM D882 – test method for testing tensile properties of thin plastic sheeting.
 
• ASTM 5323-19a - Standard Practice for Determination of 2 % Secant Modulus for Polyethylene Geomembranes
 

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- Changes in liquid/water level but must show that change in level is not due to evaporation

- Seepage around pond/containment facility

- Contaminant detection in groundwater monitoring well(s)

- Pressure transducer – placed in stilling well on opposite sides or in LDZ sump show different liquid pressures

- Add chloride to liquid and conduct subsequent geophysical testing to detect chloride outside of facility

- Add dye to liquid and monitor adjacent wells

- Measure flow in Leak Detection Zone (LDZ) if present

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1.           Estimating remaining service life is important for owner’s replacement and budgeting purposes. This is gaining popularity in Australia, South America, and west and southwestern portions of the United States. As a result, a main objective of this White Paper is to educate engineers and owners on how to design, specify, and include sample coupons in their designs and installations, respectively. Most of this White Paper focuses on new projects except for the last section which focuses on old projects.

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