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The Service Life of Geomembrane Liners: Actions to be Taken. Ian D. Peggs I-CORP INTERNATIONAL, Inc. Ocean Ridge, USA EuroGeo 3 Munich March 2004. RESPONSIBILITIES REST WITH:. Regulator Owner Design engineer Manufacturer Fabricator/installer CQA firm Earthworks contractor
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The Service Life of Geomembrane Liners: Actions to be Taken Ian D. Peggs I-CORP INTERNATIONAL, Inc. Ocean Ridge, USA EuroGeo 3 Munich March 2004
RESPONSIBILITIES REST WITH: • Regulator • Owner • Design engineer • Manufacturer • Fabricator/installer • CQA firm • Earthworks contractor • Operator
REGULATOR: • Knowledgeable staff who do not: • only decide to do an electrical integrity survey at the end of construction • decide that a permitted 1 m of sand on a 3:1 slope is now inadequate and demand it be increased to 1.7 m – it all falls down! • require that HDPE be used for every liner application • expect a zero leakage rate through a single liner
OWNER • Hire experienced design engineer • Hire independent CQA firm to report directly to owner or engineer • Hire adequate CQA staff • Do CQA as soils cover geosynthetics • Require liner integrity survey • Prepare operational plan for first layer of waste placed on liner
MOBILE LEAK SURVEY: 600 mm STONES, 3 m WATER. DRAG PROBE USED. LEAK IN MIDDLE. BURN-THROUGH LOCATED WITHIN 5 mm
DESIGN ENGINEER • Do not practice outside expertise • Design for electrical integrity survey • Select correct material/grade • Specify material correctly • Hire experienced installer • Ensure manufacturer/installer can meet specifications • Ensure adequate CQA is performed – subgrade to cover soil • Require electrical integrity survey
DESIGN ANOMALY • Geomembrane liners are designed with minimum stress…….. • ……. then we use double textured geomembrane to keep soil on slopes! • May be acceptable with LLDPE, PP, PVC but not HDPE…… • ……. unless HDPE has adequate SCR • Extra care in bioreactors with higher temperatures and more settlement on slopes
MANUFACTURER/INSTALLER • Read and meet specifications • Do not assume anything • Be consistent with, and only improve, additives • Get to understand SIP • Generate fully integrated QA/QC documents • Deliver QA/QC documents with products
WELD AIR WELD SIP IN HDPE GEOMEMBRANE SEAM
CQA • Generate integrated CQA Plan • Use experienced staff • Use sufficient staff • Integrated records • Record failing data • Monitor cover soil placement
FOUND BY FAST IRS SURVEY
HDPE • SCR (ASTM D5397) • OIT (standard or high pressure) • Thermal aging (GRI.GM13, S-OIT) • UV resistance (GRI.GM13, HP-OIT) • Seam shear elongation • Seam peel separation • SIP • [Why is weld shear strength f(thickness)?]
PP • Montell CA743GA, CA721GW, CA1722GW resins • Thermal Aging (GRI.GM18, HP-OIT) • UV Resistance (GRI.GM18, HP-OIT) • Note black vs non-black • Leaching out additives • Aging under stress • Seam shear elongation • Seam peel separation • SIP
LLDPE • Density (0.935 g/cm3) • OIT (standard or high pressure) • Thermal aging (GRI.GM17) • UV resistance (GRI.GM17) • Seam shear elongation • Seam peel separation
PVC • Plasticizer • To cover or not is f(plasticizer) • PVC alloys • 30 year experience • Seam shear elongation • Seam peel separation (allowed)
PLASTICIZER RETENTION • Plasticizer permanence is a function of molecular weight. • PGI recently updated the PGI 1104 spec to include a minimum MW of 400.
CONFINED GEOMEMBRANE MAXIMUM ALLOWABLE STRAIN • SMOOTH HDPE (SCR <1500 HR) 6% • SMOOTH HDPE (SCR >1500 HR) 8% • HDPE STRUCTURED SURFACE 6% • HDPE RANDOM TEXTURE 4% • LLDPE (DENSITY >0.935 g/cm3) 10% • LLDPE (DENSITY <0.935 g/cm3) 12% • STRUCTURED LLDPE 10% • TEXTURED LLDPE 8% • SMOOTH PP 15% • THIS ONLY APPLIES TO GEOMEMBRANE CONFINED BETWEEN TWO SOIL LAYERS. IT SHOULD NOT BE APPLIED TO UNCONFINED GEOMEMBRANE.
FOR OPTIMUM DURABILITY: • Sensible regulation • Experienced engineer • Considered material/specifications • Good installation • Knowledgeable CQA • Appropriate conformance testing • Final integrity survey • Careful initial operations • 400 years covered, 75 years exposed?