Paper presented by Fred Rohe, [then] President of EPI
Your request for information relative to the longevity of PVC liner in buried applications is an often received question. The U.S. Bureau of Reclamation is one of our best resources for information relative to the longevity of buried PVC geomembrane liners. On December 14, 1989, the Bureau presented a paper at the "Seaming of Geosynthetics" conference at the Geosynthetic Research Institute, Drexel University, Philadelphia, PA. This research paper details tests conducted on actual in place PVC liner installations, and includes the following information:
One of the earliest Bureau of Reclamation PVC lining installations was in 1957 on the Shoshone Project in Wyoming. Over the years, the Bureau of Reclamation has obtained samples of PVC from various installations to determine the aging characteristics of PVC geomembranes. In the Spring of 1961, a section of .25mm (10 mil) PVC was installed on the Bugg Lateral, Tucumcari, New Mexico. Samples were obtained in 1965, 1970, 1975, 1980, and 1988 (after 27 years of service). The results of the sampling indicated the lining was intact below the water level. The samples obtained after 4, 9, and 27 years of service contained factory seams, which had been made with a chemical weld. Tensile tests were conducted to determine the bonded shear strength and peel strength of the 27-year-old factory seams. Results of the laboratory tests conducted on the seam samples indicated that the factory-fabricated seams are in excellent condition with no loss in seam strength. The bonded shear strength of the 10 mil PVC was 33.1 lbs. per inch width, and the peel strength was 19.9 lbs. per inch width after 27 years. (Current minimum requirements are 23 lbs. shear and 10 lbs. peel.)
The Bureau of Reclamation also removed samples of 10 mil PVC from the Helena Valley Canal, which was installed in 1968. Test results indicate that, as with the Bugg Lateral lining, the PVC liner and the factory seams continue to retain their integrity. The bonded seam strength was 29.2 lbs. per inch width, and the peel adhesion strength was 21.1 lbs. per inch width when the tests were conducted.
The Bureau of Reclamation's conclusions are that "The results of tests conducted on samples of in-service linings indicate that the factory seams retain excellent shear and peel strength properties with no apparent signs of deterioration." The Bureau also concluded, "Results of laboratory tests involving various environmental aging conditions indicate that there is no appreciable difference in the performance of solvent or dielectrically made factory seams."
The experiences detailed here with 10 mil PVC on 2/1 slopes show how well this material performs over the long term. Since today's projects usually use 20 or 30 mil thick PVC, you can be assured of excellent, long-term performance of PVC geomembrane liner for your application. More information from Michigan State University is available in the W.K. Kellogg research report.
If you would like a copy of the complete report, please contact the U. S. Bureau of Reclamation, Denver, Colorado, and ask for the paper entitled "Bureau of Reclamation Experiences with PVC Seams" authored by Mr. William R. Morrison and Mr. J. Jay Swihart. If I can answer any questions, or be of further assistance, please feel free to contact me at your convenience.
FOR MORE INFORMATION - REVIEW THESE PAGES ON THE DURABILITY OF PVC.
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