Search Results

William R. Morrison & J. Jay Swihart Bureau of Reclamation, Denver, Colorado 80225. USA ABSTRACT The Bureau of Reclamation has been using polyvinyl chloride (PVC) plastic in its buried membrane canal lining work for over 20 years. Results of tests conducted on samples of inservice linings indicate that the factory-fabricated seams retain excellent shear and peel strength properties with no apparent signs of deterioration. The practice of using a 1 - m overlap unbonded PVC field seam has proven adequate for most irrigation canal lining applications, but would not be suitable for applications requiring 100% seepage control. Results of laboratory investigations conducted in conjunction with a study on the underwater lining of operating canals with PVC indicate that an adhesive formulated for the repair of vinyl swimming pool liners can be used to make underwater PVC field seams. Results of these investigations also indicate that field seams made in the dry can achieve enough early peel and shear strength development (within 15 min) for placement underwater.  INTRODUCTION Reclamation has used PVC linings for seepage control in irrigation canals for over 20 years. The earliest PVC plastic lining installation was a small experimental section installed in 1957, on the Shoshone Project in Wyoming.1 The first PVC installation under construction specifications (604C-72) was on the Helena Valley Canal, Montana, in 1968. The plastic lining was an alternative to the hot, spray-applied asphalt membrane material.2 (Because the energy crisis in the 1970s caused a significant increase in the cost of petroleum products, coupled with a limited source of supply, the asphalt membrane material was deleted from our specifications.) Over the years, Reclamation has obtained samples of PVC from various installations to determine the aging characteristics of these materials.3 Results of tests conducted on PVC scams from two installations are discussed in this paper. Laboratory tests were also conducted on PVC seams as part of the research program to develop methods and materials for the underwater lining of operating canals. Reclamation has a number of leaky, unlined irrigation canals that cannot be easily dewatered for lining because of water delivery commitments. Underwater installation of a PVC lining protected with a concrete cover is currently being evaluated. In addition, PVC seams were evaluated among other seams under a laboratory study Reclamation conducted for the Environmental Protection Agency (EPA) entitled 'Evaluation of Flexible Membrane Liner Seams after Chemical Exposure and Simulated Weathering'.4 The results for the PVC seams are presented in this paper.  FIELD PERFORMANCE OF PVC PLASTIC CANAL LINERS PVC plastic linings were originally used in the rehabilitation of old, unlined canals, especially in areas unsuitable for compacted earth or concrete linings.5 Plastic linings finding wider use in new construction.6.7 The work involves four basic steps: excavation, subgrade preparation, installation of the plastic membrane, and placement of the earth cover (0.3 - 0.5 m in depth) to protect the membrane from the elements and physical damage. Because of the requirement of an earth cover, membrane linings are restricted to canals having low-velocity flows (0.3 -1 m/s). Also the side slopes should be no steeper than 2.5(H): 1(V) and preferably 3(H): 1(V) to minimize cover stability problems. PVC is manufactured in roll goods approximately 2 m wide. The roll goods are factory fabricated into sheets wide enough to cover the canal prism and up to several hundred meters in length depending upon its thickness. For most canal lining work, sheets of PVC lining can be joined simply by lapping the downstream end of one sheet of 0.9 m over the upstream end of the adjacent sheet. The PVC plastic has a tendency to adhere to itself and, with the weight of the earth cover, a sufficiently bonded joint is obtained where 100% seepage control is not required. The watertightness of the unbonded field seam is discussed in more detail in the next section. Where a more positive seal is required, the PVC is overlapped a minimum of 0.3 m and a solvent cement (recommended by the manufacturer) applied to a minimum width of 50 mm. A continuous study is being conducted by Reclamation to evaluate the performance of buried PVC membrane canal linings. Results from two installations-Bugg Lateral, Tucumcari Project, New Mexico, and the Helena Valley Canal, Helena Valley Unit, Montana- are presented. Bugg Lateral In the spring of 1961, a small test of 0.25 mm PVC was installed on the Bugg Lateral, Tucumcari Project, New Mexico. The test section was about 228 m in length, and it is the oldest Reclamation installation for which performance data are available for this material. The hydraulic properties of the canal are summarized in Table 1 . TABLE 1           Hydraulic Properties of Plastic-Lined Canals     Protective Flow Velocity Bottom width Normal water depth Cover Canal depth (m3/s)   (m/s)   (m)   (m)   (m)   Helena Valley -26   0.64   2.7   28-Jan   0.3   Bugg Lateral 2.66   0.57   4-Feb   4-Jan   0.4               Note: Ratio of side slopes in both canals is 2 (horizontal) to 1 (vertical).   Samples were obtained in 1965 (4 years of service), 1970 (9 years of service), 1975 ( 14 years of service). 1980 (19 years of service), and 1988 (after 27 years of service). A photograph taken during the 1980 field sampling is shown in Fig. 1. Results of the sampling indicated the lining was intact below water level, but had suffered some damage from root penetration above the waterline.   TABLE 2           Results of Laboratory Tests Conducted on PVC Seam Samples from Bugg Lateral.   Tucumcari Project, New Mexico           Typical       Physical Specification original 4 Years 9 Years 27 Years property requirements results of service of service of service Thickness 0.25 0.26 0.26 0.25 0.25 (mm) 10%         Tensile 3 4 4.1 4 5.5 Strength           (kN/m)           Bonded seam 1.95 4 4 3.8 5.8 Strength in           shear (kN/m)           Bonded seam Not NDa ND ND 3.5 Strength in peel Required         (kN/m)           aNot determined. Helena Valley Canal In the fall and winter of 1968-69, a reach of the Helena Valley Canal, 1930 m in length, was lined with 0.25-mm thick PVC plastic. This was the first PVC lining installation under a Reclamation construction specification (604C-72). The PVC was furnished in sheets 12.8 m wide by 122 m in length. The sheets were accordion folded in both directions for delivery to the job site. Samples of the lining containing a factory seam were obtained after 9 and 14 years of service. Results of laboratory tests conducted on the factory seam are summarized in Table 3. Test results indicate that as with the Bugg Lateral lining, the factory seams retained their integrity after 14 years of service. LABORATORY TESTS FOR UNDERWATER LINING OF OPERATING CANALS Reclamation has been conducting research to develop new technologies for lining canals while they are in operation. The basic concept consists of placing a PVC geomembrane covered with gravel, soil or concrete while the canal remains in operation. The canal would be lined in two or more passes necessitating an underwater field seam in the PVC geomembrane down the centerline of the canal. A 1-m overlapped unbonded seam was planned for this location. As previously mentioned, Reclamation routinely, uses this type of seam (in the transverse direction only) for its PVC-lined canals. Leakage through the unbonded seam was expected to be relatively small since PVC tends to bond slightly to itself under pressure. Seepage measurements obtained for some of these canals, although limited, has supported this expectation. For underwater lining, a study was undertaken to quantify the seepage for this type of seam and to examine the effects of hydraulic head, cover depth and cover material. Additional important information was obtained, quite accidentally, concerning the effect of an irregular subgrade. These results led to a second phase of the study where a new adhesive for bonding PVC under water was examined. Conventional solvents for field seaming in the dry were also examined. TABLE 3         Results of Laboratory Tests Conducted on PVC Seam Samples from Helena Valley Canal. Helena Valley Unit, Montana                 Specification     Physical requirement Typical 9 years 15 years property results original of service of service Thickness (mm) 0.25 0.27 0.25 0.25   10%       Tensile strength 3 5.8 5 5.7 (kN/m)                   Bonded seam 2.2 5 4.6 5.1 strength in shear       (kN/m)                   Bonded seam Not NDa ND 3.7 strength in peel required       (kN/m)         a Not determined.         Phase 1-Unbonded field Seams The test apparatus for determining seepage through the overlapped seam measures (width by length by height) 1.2 m by 2.4 m by 0.6 m and is shown in Fig. 2. The gravel drain collects the seepage while the geotextile provides a smooth subgrade for the PVC liner. A more representative subgrade material (i.e. something less permeable than gravel) would obviously reduce seepage; however, an investigation into various subgrade materials was beyond the scope of this study. Three cover conditions were examined including 25 mm of sand (No. 50 in size), 25 mm of sand plus 50 mm of concrete blocks (200 mm by 600 mm), and 25 mm of sand plus 150 mm of concrete blocks. The voids (approximately 10 mm wide) between the concrete blocks were filled with sand. With the aid of a stand-pipe, tests were run at hydraulic heads of 0.3, 0.9, 1.5 and 2.1 m. Each test was run for a minimum of 24 h to allow stabilization of hydraulic gradients within the gravel drainage layer. Some tests were run for up to 2 weeks to evaluate observed decreases in seepage with time. The results are summarized in Table 4. Test sets A and B are duplicates with 25-mm sand/50-mm concrete cover and demonstrate the variations seen for identical test conditions. These test sets were meant to approximate the 75 mm of concrete cover. The seepage at 2.1 m of head represents 15-30 liters per day per linear meter of seam and was considered acceptable. A gradual decrease in seepage was seen with time, caused either by fines moving through the overlapped seam and plugging the geotextile and/or gravel drain, or by settlement and compaction of the sand between the concrete blocks. TABLE 4         See page through Overlapped Unbonded Seam in PVC Geomembrane Test Set Cover Hydraulic head Seepage         (m) (liters m d)   A 25 mm of sand plus 0.3 0     50 mm concrete 0.9 0       1.5 2 2.1 15         B 24 mm of sand plus 0.3 1     50 mm concrete 0.9 5       1.5 -       2.1 30   C 25 mm of sand plus 0.3 1     150 mm concrete 0.9 4       1.5 5       2.1 15   D 25 mm of sand 0.3 15       0.9 60       1.5 80   E 25 mm of sand plus 0.3 60     50 mm concrete 0.9 400     (wrinkle in geotextile) 1.5 - Test set C used 150 mm of concrete blocks rather than the 50 mm used in test sets A and B. No measurable differences in seepage were detected. Test set D had only the 1.5 mm of sand cover (no concrete blocks) and demonstrated 20 times more seepage than test sets A and B which had 25 mm of sand and 50 mm of concrete cover. This increase in seepage has two causes. The first is the difference in cover load 25 mm versus 75 mm, and the second is the difference in seepage paths. The sand/concrete combination has not only longer but also fewer seepage paths, as the seepage can only occur through the sand between the concrete blocks. Test set E again had 25 mm of sand plus 50 mm of concrete cover: however, a defect was inadvertently introduced into the subgrade by a fold (wrinkle) in the geotextile. This defect increased seepage by a factor of about 100. As subgrade defects will be impossible to avoid entirely in the field, methods for bonding the seams underwater are needed to assure maximum water conservation. TABLE 5       PVC Seam Strength Using Special Vinyl Liner Adhesive   Peel Strength Shear Strength Cure condition (kN/m) (kN/m)   Air 2.6 10   Underwater 3 12.2   Requirementa 1.8 9.8   a Specification requirements for factory seams   Phase II-Bonded field seams Phase II of the study examined solvents adhesives for field seaming of PVC geomembranes both underwater and in the dry. The biggest challenge was finding a solvent which could be used underwater, as there has been very little experience in this area. Discussions with manufacturers led to the selection of a specially modified bodied tetrahydrofuran solvent used to repair vinyl swimming pool liners. Test results for PVC seams made both underwater and in air with the special vinyl adhesive are summarized in Table 5. Tests were conducted to determine peel and shear strength after a 24-h cure. Test results indicate that the seams are quite satisfactory and even meet the requirements for factory seams using conventional solvents in the dry. There was also concern about the rate of seam strength development for the transverse field seams that would be needed every 60 m. These seams would be fabricated in the dry with conventional solvents but then very quickly (perhaps within 15 min) subjected to shear stress as they were placed underwater in the canal prism. Seam specimens were fabricated in air with a manufacturer-supplied solvent cement and tested for shear and peel strength after cure times ranging from 5 min up to 4 h. The shear strength developed very quickly (within 5 min) and then decreased with time until reaching equilibrium after 1-2 h. Conversely, the peel strength developed rather slowly and required-30- 60 min to develop fully. Shear strength is the more critical as shear is the predominant stress on the seams during installation and service. Tests were also performed to ensure that specimens, made with conventional solvent and initially cured in air, would continue to cure underwater. Seam specimens were partially cured in air for 5 min and then cured in water for 3 days. These specimens did indeed develop full shear and peel strengths. RESULTS OF EPA STUDY In 1986, Reclamation completed a study for EPA entitled 'Evaluation of Flexible Membrane Liner Seams After Chemical Exposure and Simulated Weathering'. In this study, 37 geomembrane seams, both factory and field were evaluated. The PVC seams included in the study are listed in Table 6. The seams were subjected to six chemical solutions, brine and water immersion, freeze/thaw cycling, wet/dry cycling, heat aging, and accelerated outdoor aging for periods of up to 1 year. Effects of these environmental conditions were evaluated using shear and peel strength tests before and after exposure. The tests were performed under dynamic load at room temperature and under static dead load at 50° C. The rate of grip separation for both the peel and shear tests was kept the same (50 mm/min) to determine if there was any direct correlation between the two properties. Also, a 25-mm wide test specimen was used in both tests. Results of tests conducted on seams subjected to water immersion, freeze/thaw cycling, wet/dry cycling, and heat aging are summarized in Table 7. These environmental conditions are those often encountered in Reclamation's hydraulic applications. TABLE 6           Type of PVC Seams Evaluated in EPA Study     Sample Type of Manufacturer Seaming Seam   No Seam Fabricator Method Width   1 Factory A,C Solvent adhesive 25   2 Factory A,D Thermal-dielectric 19   3 Field Aa Solvent adhesive 50   4 Filed Ab Solvent adhesive 88   5 Filed Bc Solvent adhesive 75 a Solvent adhesive furnished by fabricator C.   b Solvent adhesive furnished by fabricator D.   c Solvent adhesive furnished by manufacturer B.   Test results indicated that except for heat aging, the samples performed satisfactorily with very little change occurring to either the shear or peel strength. The heat aging samples exhibited stiffening due to plasticizer loss from the material. Of the two factory seaming methods used for the PVC, the seams made with the solvent adhesive exhibited higher shear strength, whereas those made dielectrically produced higher peel strength values. The higher shear strength was primarily due to the wider factory seam for the solvent adhesive seam. All failures occurred in the parent material, except for the peel tests on the PVC solvent adhesive seam, where the failure occurred within the seam itself. No appreciable difference was noted in the performance of the two seaming methods however. TABLE 7                       Results of EPA Study on PVC Seams                     Sample 1   Sample 2   Sample 3   Sample 4   Sample 5     Test Condition Shear Peel Shear Peel Shear Peel Shear Peel Shear Peel Original   10 2.6 9.3 6.7 8.3 2.7 9.3 3.4 10.4 4.3 Water immersion at 23°C 6 months 9.9 2.8 9.1 6.6 8.5 3.1 10.5 3.8 10.6 4.3   12 months 10 2.9 9.3 7.3 9 2.7 10.7 3.9 11.7 4.4 Heat aging at 60°C 4 weeks 9.2 3.1 9.3 6.5 8.8 3.8 10.4 4.2 10 4     8 weeks 9.1 3.1 9.2 6.9 9.4 3.2 9.3 4.3 11.3 5.1   13 weeks 10 3.3 9.5 6.9 9.1 4.1 10 4.4 11.4 3.9 Freeze/thaw at: 10 cycles 10.1 2.7 8.9 6.7 8.4 2.4 9.6 4 10.5 4.4   20 cycles 9.7 2.8 9.3 7.3 9.3 3 10 4 12.4 4.7   50 cycles 10.1 2.8 8.4 7.2 8.9 2.7 9.1 3.8 10.4 4.7 Wet/dry at: 10 cycles 10.2 2.7 9.4 6.9 8.4 2.6 10.3 3.8 11.2 6   20 cycles 9.9 2.7 8.5 6.5 8.8 3.3 9.5 3.7 10.2 3.2   50 cycles 9.9 2.7 10.1 6.7 8.2 2 10.6 4.3 10.7 4.6 Note: Test values are expressed as kN/m width of seam. One freeze/thaw cycle consisted of freezing for 16 h at 6.7?C and thawing for 8 h in room temperature water. One wet/dry cycle consisted of 16 h water immersion followed by 8 h of drying at 37.7?C. CONCLUSIONS The Bureau of Reclamation has been using PVC in its buried membrane canal lining work for over 20 years. Results of tests conducted on samples of inservice linings indicate that the factory seams retain excellent shear and peel strength properties with no apparent signs of deterioration. A 1-m overlap, unbonded PVC field seam appears to be adequate for most irrigation canal lining applications, but would not be suitable for landfills or hazardous waste installation where 100% seepage control is required. Results of laboratory tests also indicate that the solvent-bonded field seams can achieve early peel and shear strength development which is advantageous for underwater lining applications. Laboratory tests conducted on an adhesive sealant formulated for the repair of vinyl swimming pool liners indicated that it can be used to make underwater PVC field seams. 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.  REFERENCES 1. Hickey, M. E. Investigations of plastic films for canal linings. Research Report No. 19. A Water Resources Technical Publication. Bureau of Reclamation, Denver, Colorado, 1969.2. Geier, F. H. & Morrison, W. R. Buried asphalt membrane canal lining, Research Report No. 12. A Water Resources Technical Publication. Bureau of Reclamation, Denver, Colorado, 1968.3. Morrison, W. R. & Starbuck, J. G. Performance of plastic canal linings. Bureau of Reclamation Report No. REC-ERC-84-1. Denver, Colorado, 1984.4. Morrison. W. R. & Parkhill, L. O. Evaluation of flexible membrane liner seams after chemical exposure and simulated weathering, US Environmental Protection Agency. Report No. EPA/600/S2-87/0l5, Cincinnati, Ohio, 1987.5. Wilkinson, R. W. Plastic lining on the Riverton Irrigation Project. Proc. ASCE Irrigation and Drainage Speciailty Conference. Flagstaff, Arizona, 1984.6. Starbuck, J. G. & Morrison, W. R. Flexible membrane for closed basin conveyance channel. San Luis Valley Project, Colorado, Proc. International Conference on Geomembranes. Denver, Colorado, 1984.7. Weimer, N. F. Use of polyvinyl chloride liners for large irrigation canals in Alberta. Canadian Geotechnical Journal. 24 (1987) (2) 252-9.    REC-ERC-84-1 PERFORMANCE OF PLASTIC CANAL LININGS January 1984 Engineering and Research Center U. S. Department of the InteriorBureau of Reclamation   Table18. -Physical properties test results for PVC membrane linings on Bugg Lateral. Tucumcari Project, New Mexico, installed spring 196l.- Continued     Sample Sample Sample   Specifications No. B-6764 No. B-7022 No. B-7023 Physical property requirements (14 years (19 years (I 9 years     of service, of service, of service,     BWL) BWL2 ) AWL1) Thickness, mm (mils) 0.25 (10) 0.24 (9.6) 0.24 (9.6) 0.21 (8.2) percent change ±10 -14.3 -14.3 -26.8           Tensile strength, N/mm (lbf/in) 3.0 (1 7) 4.2 (24.2) L3 4.6 (26.4) L 5.0 (28.6) L     4.6 (26.1) T4 5.2 (29.8) T 4.7 (26.9) T percent change -5.5 L +3.1 L +1 1.7 L     +14.5 T +30.7 T +18.0 T           Elongation percent 225* 268 L 211 L 151 L     274 T 188 T 188 T percent change -35.0 L -48.9 L -63.3 L     -40.7 T -59.3 T -59.3 T           Modulus at 100 percent Not required 2.4 (13.8) L 3.6 (20.5) L 4.6 (26.0) L elongation, N/mm (lbf/in) 2.4 (13.8) T 4.2 (23.9) T 4.2 (23.9) T percent change +21.1 L +79.8 L +128.1 L     +34.0 T +132.0 T +132.0 T           Elmendorf Tear, grams 1500* 3000 L 3000 L 450 L     2865 T 2200 T 1300 T percent change +63.9 L +63.9 L -75.4 L     +25.1 T -3.9 T -43.2 T           Impact resistance Not more than 2 5 tested Not Not   specimens out determined determined   of 10 shall fail 5 failures       at -18ºC (0ºF)               Plasticizer content, percent Not required 34.1 27 21.6 percent change -14.3 -32.2 -45.7           Bonded seam strength, 65 Not Not Not percent of parent material determined determined determined           1 AWL denotes above normal waterline   2 BWL denotes below normal waterline   3 L denotes longitudinal direction     4 T denotes transverse direction     * Minimum, each direction         Canal data: Established     seepage   b = 5.00 ft, d =4.40 ft, s:s =1.5:1, and   rate   WP =20.86 ft. (7.4806 gal/ft3) (2169 ft2)   Length =104.25 ft.     Average seepage rate for section is 8.2 = 0.0005 (ft3/ft2)/d gal/d.   Reach 5A, station 599+00, PVC lined: Seepage section has a wetted surface of (104)(2y0.86) = 2169 ft2. Canal data: For more information call   800-OK-LINER   today!

T he First Pan American Geosynthetics Conference & Exhibition2-5 March 2008, Cancun, Mexico Eliminating costly tests for PVC geomembranes by using new ASTM D 7177 air channel test for field seams. D.S. Rohe, Environmental Protection, Inc. Mancelona, MI, USA ABSTRACT Air channel strength testing of dual track thermal welds of PVC geomembranes has been developed to provide quality assurance for the full length of PVC geomembrane field welds, eliminating the need for cutting holes in the liner to perform destructive peel testing.  The testing method was adopted as ASTM D 7177 Standard Specification in June 2005 and has been published for use since the 2006 construction season.  This paper will present a detailed case history of the installation quality control and engineering quality assurance programs implemented on the 787,800 square foot 40 mil PVC geomembrane lagoon system installed at the Village of Manton Wastewater Treatment Lagoon improvement project in Manton, MI, USA.  The design engineers at Fleis & Vandenbrink Engineers worked with the Michigan Department of Environmental Quality to eliminate the outdated and highly inaccurate water balance test by requiring air channel testing for PVC geomembrane field seams.  The 40 mil PVC geomembrane was installed using dual track thermal welding and all field seams were air channel tested for seam continuity and peel strength.  The success of this project has provided the basis for implementing this new testing technology in lieu of the water balance test, saving the customer precious time and ultimately precious funding. Introduction In Michigan, there have been numerous projects to rehabilitate old existing waste water lagoons.  Many of these lagoons were constructed over thirty years ago and simply used native soils or natural clay as a bottom liner.  At the time, clay was a suitable option for a liner system to minimize infiltration into the soil and potentially the water table.  With the advances in geosynthetic technology over the past few decades, there are now a plethora of better liner systems. Using Government grants and funding through the United States Department of Agriculture (USDA) Rural Development, many communities have been able to rehabilitate their waste water treatment plants to include a new geosynthetic liner system.  In the spring of 2006 the Village of Manton, Michigan began this process. Contractors Fleis & Vandenbrink Engineers from Grand Rapids, Michigan were retained by the Village and given the task of designing the new system and construction oversight for the project.  The project was advertised for public bid proposals.  Team Elmer's was selected as the Prime Contractor to complete the project and selected Environmental Protection, Inc. (EPI) as the PVC geomembrane fabricator and installer.  The project specifications also required an independent third party construction quality assurance firm specifically to inspect the geomembrane liner installation and testing.  STS Consultants, Ltd. was retained for this purpose as the independent third party construction quality assurance (CQA) firm.  Design The existing lagoon system was made up of three large lagoons.  The new design would require two of the existing lagoons be renovated to include two settling lagoons (lagoons number two and four) and one aeration basin (lagoon 1a).  The third existing lagoon would be removed from service but left intact for future expansion.  The excavation phase began by draining each lagoon.  Once the lagoon had drained down to a workable level, the contractor began with the sludge drying and removal.  After the sludge removal was complete, the subgrade was excavated down to the existing clay liner system.  Since this project was a rehabilitation of existing lagoons, the engineer also designed a gas venting system into the subgrade that would allow any gases from organic degradation to vent outside the liner and not be trapped below the liner system.  A sand cushion layer was then placed over the clay subgrade in preparation for the PVC geomembrane. The new design specified 40 mil PVC geomembrane be used as the primary liner system in the rehabilitated lagoons.  For the three new lagoons, a total of 787,800 square feet of 40 mil PVC geomembrane would be required to completely line the lagoons.  EPI fabricated the 40 Mil PVC geomembrane into panels as large as 15,000 square feet (75 feet wide & 200 feet long) for this project.  By fabricating large custom sized panels, the amount of field seams required would be minimized. The sequence was essentially the same for each lagoon.  Once the PVC geomembrane was installed and all testing had been completed, the excavation contractor began placing the cover soil.  One foot of cover soil was placed over the entire liner system using heavy equipment and GPS guided bulldozers for finish grading.  The side slopes were also covered with rip rap to maintain the cover soil and minimize erosion.  Once the excavation, liner placement and cover soil phase was completed, each individual lagoon was placed back into service prior to beginning work on the next lagoon.  This sequence allowed the Village of Manton to continue uninterrupted service during the rehabilitation process.  Geomembrane discussion Project specification required the Minnesota Water Balance Test to be conducted if all the requirements of the air channel testing were not met to the satisfaction of the Owner.  The water balance test essentially consists of filling each lagoon with clean water and measuring any change in the water level.  Any water level changes are compared against a control to determine the integrity of the lagoon liner system.  The control is typically a barrel placed in or near the lined area or a weather station.  Measurements are taken for four weeks and compared with atmospheric gains and losses to determine the lagoon leakage rate.  The downside of the water balance test is the time it takes as well as the required clean water to fill the lagoons to six feet in depth.  The accuracy of the test itself makes the determination of liner integrity a real challenge.  The time involved for the contractor as well as the challenge of securing the clean water to fill the lagoons is quite costly.  Following are the details of how the water balance test was not required due to the high level of testing and quality control required on this project. Prior to the lagoons being prepared, the geomembrane panels were delivered to the site and each fabricated geomembrane panel was labeled with its size and a unique serial number for quality control purposes.  During installation, the panels were deployed beginning in the morning and technicians began seaming once enough panels were in place to begin.  Seaming was performed using a hot air welding machine that produced a dual track thermal fusion weld with an unbonded center channel for testing.  Prior to production seaming, the machines were configured and trial welds were made.  These trial welds were tested with a portable tensiometer to ensure seam strengths.  All field seams were dual track welded, including the ?butt seams? that have the overlap from factory seams.  These factory seams of each panel have the potential to leak at the intersection of field to factory seams if the welding machine is not properly configured.  Special care was taken to ensure the field seams that included factory seam overlaps were sealed at each joint. The project specifications required the 40 mil PVC geomembrane to be installed with all production field seams constructed using dual track thermal fusion welds.  The dual track weld leaves an unbonded area between two parallel welds that can be air pressure tested.  With this technique, the entire length of seam can be evaluated to ensure continuity as well as seam strength.  Minimum required peel strength was 15 pounds per inch width and minimum required shear strength was 77.6 pounds per inch width.  All of the trial welds and destruct samples were tested in peel and shear modes according to ASTM D 6392 Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams.  Every destruct taken passed the requirements for peel and shear, with peel strength averaging around forty pounds per inch width. Thermal fusion welding allows for the air channel testing to be performed once the seam is completed and the material returns to ambient temperature.  This allowed the installation personnel to begin air channel testing shortly after each seam was completed.  The air channel testing was typically done in the afternoon, after enough seam was completed to efficiently test.  Ambient temperatures were typically between 80°F and 100°F.  The geomembrane liner temperatures were normally 20°F to 40°F above the ambient temperature due to the dark coloration of the liner.The specifications for this project required all seams be air channel tested according to GRI Test Method GM6 .  The project specifications did not require the test pressure in the air channel to meet the ASTM D 7177 requirements. The ASTM D 7177 testing requirements specify a minimum pressure at a particular geomembrane sheet temperature.  Due to the high ambient temperatures, the ASTM requirements actually correlated to the GRI GM6 test requirement which was actually slightly lower than the ASTM requirements.  In accordance with the ASTM D 7177 test method which requires the seam to maintain the minimum pressure at a given sheet temperature, this test method will verify seam strength as well as continuity.  EPI used the minimum requirements of the ASTM method since they were more specific to PVC geomembrane than the requirements of GM6 and provided more confidence to the CQA.  GRI GM6 requires the seam of 40 mil PVC geomembrane to maintain a pressure of 20-30 psi and have no more than a five psi drop over a two minute holding period.  The air channel pressures used for this project were between 20 psi and 30 psi and typically on the higher end at 25 psi to 27 psi.  Given the sheet temperatures at the time of the tests, the pressures used would ensure the seam strength of the entire length of seam according to ASTM D 7177 .  Any seam that did not hold the required pressure was investigated to find the leak point and then tested in each direction from the leak.  The leak point was then capped with a repair patch after the air channel testing was completed.  That repair patch was then tested using the air lance method according to ASTM D 4437 .  Lagoon 2 ( Figure 1 ) was ready to be lined in June of 2006.  304,625 square feet of 40 mil PVC Geomembrane liner was supplied for this lagoon.  From approximately 4,500 lineal feet of field seam in this lagoon, nine destructive samples were taken.  Over 1,225 lineal feet of field seam from this lagoon were from the factory end to factory end type of field seam.  This means there was a "T" from the factory seam every 6.25 feet on both panels being seamed.  It was critical that these end to end seams were also dual track welded and air channel tested to ensure the integrity of the seams.  Special care was taken by the seaming technicians when setting up the welder to make sure this type of seam was completely sealed.  Then the air channel test also verified the strength of the seam as well as continuity. Figure 1.)  Lagoon 2 panel layout.   There is a potential for each of the "T" seams to have a very tiny leak at the junction of three sheets of material.  This is another reason why air channel testing every seam is critical to the integrity of the liner system and not just using air channel testing for the long flat edge to flat edge seams.  While destructive samples will give you a decent representative sample, they are not comprehensive.  For example, if a destruct is taken in the first half of any given seam and the welding machine has a malfunction in the second half of the seam, it is possible for that section of seam to go unchecked for strength.  With dual track welding and air channel testing according to ASTM D 7177 , the entire length of seam will be pressurized and any section of seam that is less than the required peel strength will quite literally peel open from the inside out.  This is in essence peel testing 100% of the seam from the inside out.  This technological advance in non-destructive testing is also a destructive test over the entire length of seam giving all parties involved a much higher level of confidence in the final liner system. Lagoon 1a ( Figure 2 ) was the next lagoon to be lined in July of 2006.  A little more than 76,000 square feet of PVC Geomembrane liner was required for this aeration basin.  There were two destruct samples taken from nearly 880 lineal feet of field seam in this lagoon.  Only about 225 lineal feet of field seam from this lagoon were from the factory end to factory end.  Given the critical nature of these types of seams they were also dual track welded and air channel tested to ensure there were no leaks.                    Figure 2.) Lagoon 1a panel layout.                                    Figure 3.) Lagoon 4 panel layout.   Lagoon 4 ( Figure 3 ) was the last lagoon to be rehabilitated in August of 2006.  406,625 square feet of 40 mil PVC Geomembrane liner was provided for this lagoon.  There were 16 destruct samples taken from almost 8,000 lineal feet of field seam in this lagoon.  Close to 1,700 lineal feet of field seam from this lagoon were from the factory end to factory end.  All seams were dual track welded and air channel tested to ensure their strength and integrity.  Conclusion With the very short construction season in Michigan, which is typically April through October, waiting 30 days for a water balance test on each lagoon would have been a real challenge for the contractor to complete the project on schedule.  Therefore, completing the air channel testing on all field seams and not being required to undertake the water balance test was a significant savings to everyone involved.  In the end, this savings directly benefitted the community and the Village of Manton.  This project provides a great example of how more stringent quality control procedures and requirements can actually be a cost savings in the long run.    References GRI Test Method GM6. Standard Practice for Pressurized Air Channel Test of Dual Seamed Geomembranes, Geosynthetic Research Institute, Folsom, Pennsylvania, USA. ASTM D 4437, Standard Practice for Determining the Integrity of Field Seams Used in Joining Flexible Polymeric Sheet Geomembranes, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D 6392. Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams Produced Using Thermo-Fusion Methods, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D 7177. Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA.   For more information call   800-OK-LINER   today!

Air Channel Test ASTM D 7177 Eliminates Water Balance Test of PVC Geomembrane Lined Surface Impoundment  Fred P. Rohe and Daniel S. Rohe, Environmental Protection, Inc.   ABSTRACT This paper will present a detailed description of the installation quality control and engineering quality assurance programs implemented on the 73,000 square meter (787,800 Ft2) PVC geomembrane lagoon system installed at the Village of Manton Wastewater Treatment Lagoon improvement project in Manton, MI USA.   Air channel strength testing of dual track thermal welds of PVC geomembranes has been developed to provide quality assurance testing for the full length of PVC geomembrane field welds.  This method effectively peel tests every inch of a field weld and eliminates the need for cutting holes in the liner to remove samples in order to perform destructive peel testing on only a small portion of the seam.  The testing method was adopted as ASTM D 7177 Standard Specification for Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes in June 2005 and was first used extensively in the 2006 construction season.  The designers at Fleis & Vandenbrink Engineers worked with the Michigan Department of Environmental Quality to eliminate the outdated and obsolete water balance test by requiring air channel testing for PVC geomembrane field seams.  The success of this project has provided the basis for implementing this new testing technology in lieu of the water balance test, saving customers precious time and ultimately precious funding for construction of PVC lined surface impoundments.  INTRODUCTION There is an old cliche about spending more initially for a quality product and saving money in the long run.  This paper provides information about how quality PVC geomembrane welding and testing can provide immediate cost savings today to owners, operators and communities. Thermal welding of PVC material is not a new development. The process has been used for many years in all types of PVC fabrication. However over the past 5 years or so, there have been new developments and improvements in the equipment and techniques for thermal welding of thin, flexible PVC films used as geomembranes.  In the process of developing these new techniques and working countless hours in the field with new equipment, it became very apparent to the authors that air channel testing of PVC dual track welded seams was also a strenuous test of the strength and quality of the full length of every weld.   While heat welding any thermoplastic geomembrane today is relatively simple, welding long lengths of seam without the slightest imperfection in its peel strength is still quite challenging.  This came to light on some of the first projects while developing these PVC air channel testing techniques. For instance, a field seam that had a destructive sample removed (and that sample passed independent laboratory peel testing) failed when air channel tested along its entire length.  A large section of that same tested seam had not bonded completely, had passed air lance testing, but began to split open when air channel tested.  It was then that the authors were more convinced than ever that air channel testing of PVC geomembranes could in fact measure the strength, and therefore the quality, of the entire length of a weld. The authors also discovered that thermal welding long lengths of seam (> 60-100M) (200-300 ft.) that easily passes an air lance test, would invariably fail an air channel test in some small area, unless the operator was thoroughly trained and the welding machine properly set up.  Temperature, speed, and contact pressure are critical to developing a consistent weld in any geomembrane.  Welding too hot and traveling too fast are the major detriments to the successful, consistent welding of PVC.  They also discovered that too much air pressure at very high sheet temperatures would cause failure in an otherwise passing PVC weld.  This is not the case in testing HDPE geomembranes. Persisting in their belief that air channel testing could provide real time strength testing of PVC welds led others into this research and the eventual development of ASTM D 7177 Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes.  This procedure only applies to the air channel strength testing of PVC geomembrane welds.  While there have been serious attempts to develop a similar procedure for testing the full length of other thermoplastic geomembrane welds (i.e. HDPE), none have been successful or standardized. The Manton project recognized that superior testing of the PVC geomembrane seams by checking both the continuity and strength would render a costly and time consuming water balance test unnecessary. (Not to mention that a water balance test does not identify the defect, it only tells you the lagoon is leaking, but not where.)   The project specifications required the Minnesota Water Balance Test be conducted, if all the requirements of the air channel testing were not met to the satisfaction of the Owner.  The water balance test essentially consists of filling each lagoon with clean water and measuring any change over a 30 day period.  Any water level changes are compared against a control to determine the integrity of the lagoon liner system.  The control is typically a barrel placed in or near the lined area or a weather station.  Measurements are taken for four weeks and compared with atmospheric gains and losses to determine the lagoon leakage rate.  The downside of the water balance test is the cost of the time it takes, as well as the cost of pumping clean water to fill the lagoons to six feet in depth, and then discharge it again.     CASE STUDY The Village of Manton in northwest lower Michigan has a wastewater treatment facility utilizing three ponds.  The ponds were originally constructed using clay soil as a liner.  In 2006 it became necessary to rehabilitate the lagoons and reduce the amount of leakage from the ponds.  Elmer's Crane & Dozer, Inc. of Traverse City, MI USA was selected as prime contractor for the project.  They performed all of the earth work on the site. Elmer's selected Environmental Protection, Inc. (EPI) of Mancelona, MI USA to fabricate and install the PVC geomembrane liner system.  STS Consultants, Inc. was retained as the independent third party construction quality assurance (CQA) firm to oversee liner installation and testing.  73,000 M2 of 40 mil PVC geomembrane was required to completely line the lagoons.  EPI fabricated the 40 Mil PVC into panels as large as 1,400 M2 (15,000 square feet -75 feet wide & 200 feet long). These large custom sized panels were used to reduce the amount of field seams required.  The existing lagoon system was made up of three large ponds.  The new design would require two of the existing lagoons be renovated to include two settling lagoons (lagoons number two and four) and one aeration basin (lagoon 1a).  The third existing lagoon would be removed from service but left intact for future expansion. In succession, the lagoons were each drained, dewatered, and sludge removed, then excavated down to the original clay liner.  Since this project was a rehabilitation of existing lagoons, the engineer also designed a gas venting system into the subgrade that would allow any gases from organic degradation to vent outside the liner and not be trapped below the liner system.  A sand cushion layer was then placed over the clay subgrade in preparation for the PVC geomembrane.  The sequence was essentially the same for each lagoon.  Once the PVC geomembrane was installed and all testing had been completed, the excavation contractor began placing one foot of cover soil over the entire liner system using heavy equipment and GPS guided bulldozers for finish grading.  The side slopes were also covered with rip rap to maintain the cover soil and minimize erosion.  Once the excavation, liner placement, and cover soil phase was completed, each individual lagoon was placed back into service prior to beginning work on the next lagoon.  The use of the air channel strength test instead of the 30 day water balance test also saved a minimum of one month between the completion of one lagoon and the start of draining the next.  This sequence allowed the Village of Manton to continue uninterrupted service during the rehabilitation process.  WELDING Once the lagoon subgrade was completed, the PVC geomembrane panels were deployed and welded together using Leister Twinny hot air welding machines that produce a dual track weld with an un-bonded air channel between the welds.  Fig. 1 provides a close up view of the nip rollers and hot air nozzle that create the two parallel welds with an un-bonded air channel between. Prior to production welding, each machine was configured and trial welds were made.  Minimum required peel strength was 2.6 kN/M (15 lb/in width) of specimen and the shear strength requirement was 14 kN/M (77.6 lbs/in width).  All trial welds and destructive samples were tested according to ASTM D 6392 Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams.  There was approximately 3,700 lineal meters (12,000 feet) of field seam produced on this project.  The CQA Engineer removed 26 destructive samples (> 1 sample per 150 M of seam).  All destructive samples were tested in EPI's lab, and 50% of the samples (13) had a portion also sent to an independent laboratory (TRI / Environmental, Inc., Austin, TX).  All samples met specification requirements when tested according to ASTM D 6392 . FIG 1.) Dual Track Hot Air Welder   AIR CHANNEL TESTING  Air channel testing of the dual track field seams was conducted immediately after the welding was completed and the material had cooled to ambient temperatures. The specifications for this project required all seams be air channel tested according to GRI Test Method GM6 .  ASTM D 7177 testing requirements specify a minimum pressure for each particular geomembrane sheet temperature.  On this project, the ASTM requirements correlated to the GRI GM6 test requirement (GM6 was actually slightly lower than the ASTM requirements.)  In addition, the ASTM D 7177 test method will verify seam peel strength, as well as continuity.  EPI used the minimum requirements of the ASTM D 7177 method since they were more specific to PVC geomembrane than the requirements of GM6, and provided more confidence to the CQA.  When the air channel is inflated (FIG. 2) to the appropriate test pressure for the material temperature, a peel stress equivalent to 2.6 kN/m (15 lb/in width) is applied to the interior of BOTH sides of the dual track weld.  Thus both welds are being tested at the same moment.  The peel stress from the interior of the weld is similar to the stress applied to a test specimen in a tensiometer when it is peel tested from the exterior of the weld channel. FIG. 2.)  Exaggerated view of an inflated dual track PVC geomembrane thermal weld produced with a Leister Twinny hot air welder. Significant research was done on this test method comparing air channel peel pressures to actual laboratory peel specimen test results.  "Air Channel Testing of Thermally Bonded PVC Seams", by Thomas, et al. (2003) describes the testing used to develop the relationships between air pressure in the PVC channel and the temperature of the PVC material at the time of testing.  These field tests results were then correlated with laboratory test results to develop a relationship between air channel pressures and peel strength of the weld.  Further refinements involved testing in cold temperatures with very stiff material, and testing at very high material temperatures.  The resulting information produced the following Table 1 which is referred to in ASTM D 7177 :   Table 1.  Pressure Required to Verify 2.6 kN/M (15 lb/in) Peel Strength for PVC SheetTemperature °C SheetTemperature °F Air PressureKPa Air PressurePSI Hold Time(seconds) 4.5 40 345 50 30 7 45 324 47 30 10 50 310 45 30 13 55 290 42 30 15.5 60 276 40 30 18 65 262 38 30 21 70 241 35 30 24 75 228 33 30 26.5 80 214 31 30 29.5 85 193 28 30 32 90 179 26 30 35 95 165 24 30 37.5 100 152 22 30 40.5 105 138 20 30 43.5 110 131 19 30 The air channel pressures used for this project were between 138 and 214 KPa (20 psi and 31 psi) and typically on the higher end at 165 to 193 KPa (24 psi to 28 psi).  Given the sheet temperatures at the time of the tests, the pressures used would ensure the seam strength of the entire length of seam according to ASTM D 7177 .  Any seam that did not hold the required pressure was investigated to find the leak point and then tested in each direction from the leak.  The leak point was then capped with a repair patch after the air channel testing was completed.  That repair patch was then tested using the air lance method according to ASTM D 4437 . Understanding the relationship of air pressure to material sheet temperature is critical in testing flexible PVC geomembranes.  If the pressure is not high enough, the only test is of continuity, so the pressure needs to be high enough to stress the weld in a peel mode.  Conversely, if the pressure is too high (which is often the case at very high material temperatures, i.e. above 32 °C) a passing seam can be compromised.  With excessive air pressure in the PVC channel at very high sheet temperature, we are expecting the weld to have much higher peel strength than the standard specification requires, and we cause a seam to fail an air channel test when it would normally pass a destructive peel test.  There is an inverse relationship of material sheet temperature to air channel pressure when testing PVC geomembrane peel strength. The ideal scenario would be to have every seam be leak free and without defects over 100% of its length prior to testing.  However, the ideal is tough to deliver under field conditions.  Rain, dirt, wind, operator error, burn outs all contribute to problems welding a perfect seam.  On this project 71% of the seams were welded and tested over their complete length, welded error free, without holes.  As operators and equipment improve, this rate will also improve.   AIR CHANNEL TESTING T-SEAMS ALL field seams must be tested and T-seams can be difficult if not welded properly.  T-seams are defined as a point in the seam where three layers of material overlap each other.  This occurs at the point that a dual track field weld crosses a factory seam, usually at a 90 degree angle.  The PVC geomembrane factory welded panels on this project were made up of strips of PVC material 193 cm (76 inches) wide.      FIG. 3.) Panel Layout Dwg Lagoon 2   Referring to Fig.3, each panel is made up of 12 strips of 193 cm (76 inch) wide PVC, each 61 M (200 feet) long.  The factory seams are vertical in Fig.3.  There are eleven factory seams in each panel.  The lines shown on Fig. 3 are the field seams.  There is approximately 1,200 M (4,000 feet) of simple two panel overlap field seam in this lagoon (the vertical field seams shown).  Approximately 400 M (1,225 feet) of seam (the horizontal seams shown in Fig. 3) are typical T-seams where the end of one factory panel over laps the end of another factory panel.  Since the factory seams don't normally line up exactly from the end of one panel to the end of the next panel, one of these horizontal seams could have a potential of 146 Ts in that weld.  There is an additional T-seam created at the end of each field seam.  The field T-seam must be specially prepared so that there is no un-bonded edge where the welder crosses the previously welded field seam.   FIG. 4.) Specimen from PVC geomembrane T-Seam   The air channel test over each "T" requires great care in welding (FIG. 4) in order to eliminate leaks and be able to proficiently perform air channel testing.  There is a potential at each "T" to have a very tiny hole at the junction of the three layers of material.  This is another key reason why air channel testing of every seam is critical to the integrity of the liner system finding and eliminating these holes.  Special care is taken by the welding technicians when setting up the welder to make sure this type of overlap is completely sealed, so the air channel test can be used to verify strength and continuity of these seams also. On this project the factory seams had no loose edge, so the process for welding T-seams in PVC was relatively easy. Slowing the welding machine's rate of travel allowed the melted PVC material to flow together at the junction of the three layers of material, providing the necessary seal and weld strength.  If there is a loose edge on the factory seams, then each loose edge will need to be trimmed, similar to the process used on field welds which intersect other seams.  On this project all factory panel end seams were tested over their entire length.   CONCLUSIONS The downside of the water balance test is the cost of the time it takes, as well as the cost of pumping clean water to fill the lagoons, and then discharging it again.  If the test indicates that the pond is leaking, there is no way to know where the leak may be.  On the Manton project, eliminating the water balance test of each lagoon saved at least 90 days from the construction schedule and the pumping millions of gallons of water. Air channel testing for continuity and peel strength on all PVC field welds gives the regulators, engineers and owner the assurance that every inch of field seam exceeds the minimum specified strength requirements.  Investing in a superior welding and weld testing system saved the community of Manton significant construction time and significant real dollars.   REFERENCES ASTM D 7177. Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D 4437, Standard Practice for Determining the Integrity of Field Seams Used in Joining Flexible Polymeric Sheet Geomembranes, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D 6392. Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams Produced Using Thermo-Fusion Methods, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. GRI Test Method GM6. Standard Practice for Pressurized Air Channel Test of Dual Seamed Geomembranes, Geosynthetic Research Institute, Folsom, Pennsylvania,  USA.  Thomas, R.W. and Stark, T. D., Air Channel Testing of Thermally Bonded PVC Seams, September 4, 2002 Thomas, R. W., Stark, T. D., and Choi, H., Air Channel Testing of Thermally Bonded PVC Seams, Geosynthetics International Journal, Industrial Fabrics Association International (IFAI), Vol 10, No. 3, October 2003, pp. 645-659. Thomas, R.W. and Stark, T. D., Air-Channel Testing of Thermally Bonded PVC Geomembrane Seams, Geotechnical Fabrics Report, Industrial Fabrics Association International, Vol 20, No. 8, October 2003, p. 10. Stark, T. D., Choi, H., and Thomas, R. W., Low Temperature Air Channel Testing of Thermally Bonded PVC Seams, International Association of Geosynthetic Installers, Industrial Fabrics Association International (IFAI), Vol 4, Issue 1, Winter 2004, pp. 5-7.   For more information call   800-OK-LINER   today!

CURING OF CHEMICALLY WELDED PVC SEAMS By Fred P. Rohe and Sam Lewis | Environmental Protection, Inc., Mancelona MI  Chemical welding and heat welding are the two most common methods of producing seams in geomembrane fabrication. While heat welded seams reach full strength almost as soon as they cool, chemically welded seams require a period of time for curing in order to reach full strength. Since heat welding is not always practical for use on thin gauge geomembrane material, chemical welding has been used successfully on thin gauge geomembrane materials since the 1950's. Currently, there is an increasing requirement for destructive testing of geomembrane seams at the earliest possible time. The curing of chemically welded PVC seams takes place over a long period of time. The age of the sample will affect the test results and should affect the engineer's interpretation of these results. On July 25, 1988, Environmental Protection, Inc. began a study of the curing of chemically welded PVC seams. A 100 foot long seam of 20 mil PVC was fabricated using normal EPI factory fabrication techniques. This seam was then cut into 24" long test sample blanks. These samples were then tested at the following intervals: 20 minutes, 1 hour, 2 hours, 4 hours, 7.5 hours, 23 hours, 30.5 hours, 46.5 hours, and then at a rate of one per day until the end of one month. The samples were tested for bonded seam strength using ASTM D-3083 NSF modified, and they were tested for seam peel adhesion following ASTM D-413 as modified by NSF. The results from these tests were then plotted on two graphs: shear vs. age, and peel vs. age. The natural logarithm was taken of the data and was also plotted on two graphs: ln shear vs. In age, and ln peel vs. ln age. These graphs were found to be highly linear with a correlation coefficient of .95 for ln shear vs. ln age, and .80 for ln peel vs. In age. A linear regression analysis was then performed for both log-log graphs to find the equations for the best fit lines. These lines were then superimposed on the log-log plots. The equations for the best fit lines was then exponentiated to find the best fit curves for the real data. While the applicability of these results is limited to the materials and methods used by EPI, they do show that chemically welded PVC seams will increase in shear and peel strengths over time. ASTM requires 40 hours of conditioning time in the laboratory prior to testing PVC seams for shear and peel. As can be seen from the data presented here, this may not be sufficient time for the seam to reach its ultimate strength. However, based on the age of the sample, a prediction could be made using this curve as to what the ultimate strength of the seam will be. While it is sometimes necessary to test the seams when still fairly new, the results of these tests should not be taken as representative of the ultimate strength of a chemically welded PVC seam. Caution should be used in evaluating the data on the testing of seams that are not completely cured. Figure 1.) shows the best fit curve for the shear strength vs. time of this test. The minimum shear strength of 36.8 lbs. per inch reach in approximately 2 hours. The shear strength to increase over time to a strength of 53.3 lbs. per inch width.   Figure 2.) shows the best fit curve for peel strength vs. time. The peel strength reached the minimum requirements in approximately 96 hours. The strength continued to increase throughout the time of the test reaching an ultimate peel strength of 12.1 IBS. per inch width at the conclusion of the test.   Figure 3.) illustrates the shear strength of the seam vs. its age. The minimum required bonded seam strength of 36.8 lbs. per inch was achieved in approximately 2 hours. The seam continued to cure and increase in strength to a final value of 57 lbs. at the end of the 30 day test.   As part of EPI's quality control process a second long term test on the curing of a chemically welded 20 mil PVC seam was conducted in December of 1988. Again, a l00 foot seam was fabricated using normal EPI processes. The seam was cut into 24 inch samples immediately after fabrication, and tested at the same intervals as the July long term test. Calculation of the data to plot the best fit curve was performed in the identical manner of the original test.  Figure 4.) illustrates the best fit curve of the peel strength vs. the age of the seam. The ultimate peel strength of this seam is approximately 2.5 lbs. per inch width higher than the original test. Also, the seam reached its initial minimum requirements for peel strength much sooner than the original test. Although the ultimate value of the second test was slightly higher, when superimposed on each other, the best fit curves for the increase of peel strength are virtually identical. This observation also holds true for the shear strength of the seam in that, when superimposed, the shear strength best fit curves are also almost identical from these two tests.     For more information call   800-OK-LINER  today!

XR-5 Geomembrane installation over structural Geofoam fill by Fred P. Rohe  The city of Detroit is in the process of reclaiming its river front. Over the years the area has been dominated by business and industry but the area has become an embarrassment. The Detroit Riverfront Conservancy was created with the mission of revitalizing the waterfront area. The first phase of this undertaking was the Louis Arena to the Douglas MacArthur bridge to Belle Isle. People are to run, walk, bike and roller-blade on the new RiverWalk, which will also include places for people to sit and take in the scenery. A portion of the RiverWalk passes directly between the General Motors (GM) Renaissance Center buildings and the Detroit River. GM retained Albert Kahn Associates to design a suitable plaza and promenade to blend as part of the RiverWalk project. The plaza includes a granite world map showing the GM facility locations world wide. John Carlo, Inc. was selected as the prime contractor to build the plaza as a showpiece for the GM Center.    Planter boxes were lined to create a tree-lined tiered walkway.   Material The area selected for the plaza has seen many varied uses over the past century. There are many unknowns regarding the soils and other materials deposited there. It was known that the area had experienced some subsidence and the fill in the area was over soft soils. The area is bounded on one side by a service areaway and on the other by a concrete sea wall at the river’s edge. The site’s close proximity to the Windsor Tunnel under the Detroit River to Canada was another important consideration.The plaza area needed to be raised approximately four meters above the existing parking lot area it is replacing. The designers selected expanded polystyrene Geofoam for use as fill material. The 1.5 pounds/square foot density Geofoam would save weight, reduce lateral pressures on the adjacent structures, and speed construction at the congested work site. Hydrocarbons have a devastating effect on contact with expanded polystyrene foam. In order to protect the Geofoam from damage by an accidental spill of fuel or other hydrocarbon materials, the designers utilized a geomembrane. 8130 XR-5 was selected to cover the top of all areas where Geofoam was installed. XR-5 is a PVC coated fabric formulated using Elvaloy, a chemical resistant polymer which imparts flexibility to the geomembrane. Protective sand layer was broadcast-spread over geomembrane liner.    Discussion The GM Renaissance Center Plaza and Promenade is a public area in downtown Detroit. GM will be displaying vehicles at the plaza as well as hosting many outdoor events in the area. The plaza will also be heavily landscaped to provide an enhanced look to the park like setting. The plaza is also directly adjacent to a busy city street with all types of vehicles all types of vehicles traveling in the congested area. There is legitimate concern for a possibility of an accidental fuel spill. Therefore it was necessary to take precautions to protect the Geofoam from any adverse exposure to chemicals that would dissolve the foam. Environmental Protection, Inc. (EPI) was selected to provide over 4,700 square meters of XR-5 geomembrane liner for this project. Over one acre of XR-5 was prefabricated to fit the varying shapes of the plaza and the many planter boxes and planting areas that were incorporated into the design. Each area of the plaza where Geofoam was installed had to be covered with geomembrane. The XR-5 material was installed directly over the foam, or over a sand cushion that was installed on top of the foam in some areas. The liner extended up vertically 30 to 50 centimeters on the perimeter concrete walls. The geomembrane was secured to the concrete using an aluminum batten bar 0.3175 centimeters by five centimeters. The batten was anchored to the concrete wall using Ramset three centimeter long powder-actuated fasteners located approximately 15 centimeters centre to centre. Since the geomembrane now acts to collect any fluid, including rainwater, a drain age system had to be implemented above the liner and drain piping to direct the water away from the plaza. The liner was sealed to these drain pipes using prefabricated EPI Tapered Pipe Boots. Boots were custom fabricated of XR-5 for each pipe diameter used on the project. EPI also prefabricated inside and outside corners to simplify the installation of the XR-5 around the many column foundations and intricate corners in the planter areas. Installation of the XR-5 had to be coordinated with the many other subcontractors working on the site. The area was so congested that the installation had to be done in phases in order to allow enough area for everyone to operate efficiently.  Summary The XR-5 geomembrane provided an excellent solution for protection of the EPS Geofoam on this project. The material was easily fabricated to fit the unusual shapes and dimensions of the plaza and its many planters. Installation was rapid, with very little field welding required. While unlikely, it is possible that an accidental spill could cause serious damage to the Geofoam underlying the GM Renaissance Center Plaza and Promenade. The foresight to provide protection for the EPS foam will ensure that this area will be use-able and useful to the visitors to the Detroit river front for many years to come. References: Curtis, R., Page, D., Peaslee, G. “EPS Geofoam Technology Project”, The Bridge, April/June 2004, Michigan Technological University, Houghton, MI 49931. “Reclaiming The Riverfront.” “GM Riverfront Plaza & Promenade”, The Liner Letter, Vol. 4 – Issue 5, July 7, 2004. Wehrmeyer, S., “Geofoam: Providing new solutions to old challenges”, Geotechnical Fabrics Report, June/July 2001. Nystrom, J., “Applications: Geofoam takes a new track”, Geotechnical Fabrics Report, September 1999. Reuter, G., Rutz, J., “Applications: A lightweight solution for landslide stabilization”, Geotechnical Fabrics Report, September 2000.     For more information call   800-OK-LINER  today!

William R. Morrison & J. Jay Swihart Bureau of Reclamation, Denver, Colorado 80225. USA ABSTRACT The Bureau of Reclamation has been using polyvinyl chloride (PVC) plastic in its buried membrane canal lining work for over 20 years. Results of tests conducted on samples of in-service linings indicate that the factory-fabricated seams retain excellent shear and peel strength properties with no apparent signs of deterioration. The practice of using a 1 - m overlap unbonded PVC field seam has proven adequate for most irrigation canal lining applications, but would not be suitable for applications requiring 100% seepage control. Results of laboratory investigations conducted in conjunction with a study on the underwater lining of operating canals with PVC indicate that an adhesive formulated for the repair of vinyl swimming pool liners can be used to make underwater PVC field seams. Results of these investigations also indicate that field seams made in the dry can achieve enough early peel and shear strength development (within 15 min) for placement underwater.  INTRODUCTION Reclamation has used PVC linings for seepage control in irrigation canals for over 20 years. The earliest PVC plastic lining installation was a small experimental section installed in 1957, on the Shoshone Project in Wyoming.1 The first PVC installation under construction specifications (604C-72) was on the Helena Valley Canal, Montana, in 1968. The plastic lining was an alternative to the hot, spray-applied asphalt membrane material.2 (Because the energy crisis in the 1970s caused a significant increase in the cost of petroleum products, coupled with a limited source of supply, the asphalt membrane material was deleted from our specifications.) Over the years, Reclamation has obtained samples of PVC from various installations to determine the aging characteristics of these materials.3 Results of tests conducted on PVC scams from two installations are discussed in this paper. Laboratory tests were also conducted on PVC seams as part of the research program to develop methods and materials for the underwater lining of operating canals. Reclamation has a number of leaky, unlined irrigation canals that cannot be easily dewatered for lining because of water delivery commitments. Underwater installation of a PVC lining protected with a concrete cover is currently being evaluated. In addition, PVC seams were evaluated among other seams under a laboratory study Reclamation conducted for the Environmental Protection Agency (EPA) entitled 'Evaluation of Flexible Membrane Liner Seams after Chemical Exposure and Simulated Weathering'.4 The results for the PVC seams are presented in this paper.  FIELD PERFORMANCE OF PVC PLASTIC CANAL LINERS PVC plastic linings were originally used in the rehabilitation of old, unlined canals, especially in areas unsuitable for compacted earth or concrete linings.5 Plastic linings finding wider use in new construction.6.7 The work involves four basic steps: excavation, subgrade preparation, installation of the plastic membrane, and placement of the earth cover (0.3 - 0.5 m in depth) to protect the membrane from the elements and physical damage. Because of the requirement of an earth cover, membrane linings are restricted to canals having low-velocity flows (0.3 -1 m/s). Also the side slopes should be no steeper than 2.5(H): 1(V) and preferably 3(H): 1(V) to minimize cover stability problems. PVC is manufactured in roll goods approximately 2 m wide. The roll goods are factory fabricated into sheets wide enough to cover the canal prism and up to several hundred meters in length depending upon its thickness. For most canal lining work, sheets of PVC lining can be joined simply by lapping the downstream end of one sheet of 0.9 m over the upstream end of the adjacent sheet. The PVC plastic has a tendency to adhere to itself and, with the weight of the earth cover, a sufficiently bonded joint is obtained where 100% seepage control is not required. The watertightness of the unbonded field seam is discussed in more detail in the next section. Where a more positive seal is required, the PVC is overlapped a minimum of 0.3 m and a solvent cement (recommended by the manufacturer) applied to a minimum width of 50 mm. A continuous study is being conducted by Reclamation to evaluate the performance of buried PVC membrane canal linings. Results from two installations-Bugg Lateral, Tucumcari Project, New Mexico, and the Helena Valley Canal, Helena Valley Unit, Montana- are presented. Bugg Lateral In the spring of 1961, a small test of 0.25 mm PVC was installed on the Bugg Lateral, Tucumcari Project, New Mexico. The test section was about 228 m in length, and it is the oldest Reclamation installation for which performance data are available for this material. The hydraulic properties of the canal are summarized in Table 1 . TABLE 1           Hydraulic Properties of Plastic-Lined Canals     Protective Flow Velocity Bottom width Normal water depth Cover Canal depth (m3/s)   (m/s)   (m)   (m)   (m)   Helena Valley -26   0.64   2.7   28-Jan   0.3   Bugg Lateral 2.66   0.57   4-Feb   4-Jan   0.4               Note: Ratio of side slopes in both canals is 2 (horizontal) to 1 (vertical).   Samples were obtained in 1965 (4 years of service), 1970 (9 years of service), 1975 ( 14 years of service). 1980 (19 years of service), and 1988 (after 27 years of service). A photograph taken during the 1980 field sampling is shown in Fig. 1. Results of the sampling indicated the lining was intact below water level, but had suffered some damage from root penetration above the waterline.   TABLE 2           Results of Laboratory Tests Conducted on PVC Seam Samples from Bugg Lateral.   Tucumcari Project, New Mexico           Typical       Physical Specification original 4 Years 9 Years 27 Years property requirements results of service of service of service Thickness 0.25 0.26 0.26 0.25 0.25 (mm) 10%         Tensile 3 4 4.1 4 5.5 Strength           (kN/m)           Bonded seam 1.95 4 4 3.8 5.8 Strength in           shear (kN/m)           Bonded seam Not NDa ND ND 3.5 Strength in peel Required         (kN/m)           a Not determined. Helena Valley Canal In the fall and winter of 1968-69, a reach of the Helena Valley Canal, 1930 m in length, was lined with 0.25-mm thick PVC plastic. This was the first PVC lining installation under a Reclamation construction specification (604C-72). The PVC was furnished in sheets 12.8 m wide by 122 m in length. The sheets were accordion folded in both directions for delivery to the job site. Samples of the lining containing a factory seam were obtained after 9 and 14 years of service. Results of laboratory tests conducted on the factory seam are summarized in Table 3. Test results indicate that as with the Bugg Lateral lining, the factory seams retained their integrity after 14 years of service. LABORATORY TESTS FOR UNDERWATER LINING OF OPERATING CANALS Reclamation has been conducting research to develop new technologies for lining canals while they are in operation. The basic concept consists of placing a PVC geomembrane covered with gravel, soil or concrete while the canal remains in operation. The canal would be lined in two or more passes necessitating an underwater field seam in the PVC geomembrane down the centerline of the canal. A 1-m overlapped unbonded seam was planned for this location. As previously mentioned, Reclamation routinely, uses this type of seam (in the transverse direction only) for its PVC-lined canals. Leakage through the unbonded seam was expected to be relatively small since PVC tends to bond slightly to itself under pressure. Seepage measurements obtained for some of these canals, although limited, has supported this expectation. For underwater lining, a study was undertaken to quantify the seepage for this type of seam and to examine the effects of hydraulic head, cover depth and cover material. Additional important information was obtained, quite accidentally, concerning the effect of an irregular subgrade. These results led to a second phase of the study where a new adhesive for bonding PVC under water was examined. Conventional solvents for field seaming in the dry were also examined. TABLE 3         Results of Laboratory Tests Conducted on PVC Seam Samples from Helena Valley Canal. Helena Valley Unit, Montana                 Specification     Physical requirement Typical 9 years 15 years property results original of service of service Thickness (mm) 0.25 0.27 0.25 0.25   10%       Tensile strength 3 5.8 5 5.7 (kN/m)                   Bonded seam 2.2 5 4.6 5.1 strength in shear       (kN/m)                   Bonded seam Not NDa ND 3.7 strength in peel required       (kN/m)         a Not determined.         Phase 1-Unbonded Field Seams The test apparatus for determining seepage through the overlapped seam measures (width by length by height) 1.2 m by 2.4 m by 0.6 m and is shown in Fig. 2. The gravel drain collects the seepage while the geotextile provides a smooth subgrade for the PVC liner. A more representative subgrade material (i.e. something less permeable than gravel) would obviously reduce seepage; however, an investigation into various subgrade materials was beyond the scope of this study. Three cover conditions were examined including 25 mm of sand (No. 50 in size), 25 mm of sand plus 50 mm of concrete blocks (200 mm by 600 mm), and 25 mm of sand plus 150 mm of concrete blocks. The voids (approximately 10 mm wide) between the concrete blocks were filled with sand. With the aid of a stand-pipe, tests were run at hydraulic heads of 0.3, 0.9, 1.5 and 2.1 m. Each test was run for a minimum of 24 h to allow stabilization of hydraulic gradients within the gravel drainage layer. Some tests were run for up to 2 weeks to evaluate observed decreases in seepage with time. The results are summarized in Table 4. Test sets A and B are duplicates with 25-mm sand/50-mm concrete cover and demonstrate the variations seen for identical test conditions. These test sets were meant to approximate the 75 mm of concrete cover. The seepage at 2.1 m of head represents 15-30 liters per day per linear meter of seam and was considered acceptable. A gradual decrease in seepage was seen with time, caused either by fines moving through the overlapped seam and plugging the geotextile and/or gravel drain, or by settlement and compaction of the sand between the concrete blocks. TABLE 4         See page through Overlapped Unbonded Seam in PVC Geomembrane Test Set Cover Hydraulic head Seepage         (m) (liters m d)   A 25 mm of sand plus 0.3 0     50 mm concrete 0.9 0       1.5 2 2.1 15         B 24 mm of sand plus 0.3 1     50 mm concrete 0.9 5       1.5 -       2.1 30   C 25 mm of sand plus 0.3 1     150 mm concrete 0.9 4       1.5 5       2.1 15   D 25 mm of sand 0.3 15       0.9 60       1.5 80   E 25 mm of sand plus 0.3 60     50 mm concrete 0.9 400     (wrinkle in geotextile) 1.5 - Test set C used 150 mm of concrete blocks rather than the 50 mm used in test sets A and B. No measurable differences in seepage were detected. Test set D had only the 1.5 mm of sand cover (no concrete blocks) and demonstrated 20 times more seepage than test sets A and B which had 25 mm of sand and 50 mm of concrete cover. This increase in seepage has two causes. The first is the difference in cover load 25 mm versus 75 mm, and the second is the difference in seepage paths. The sand/concrete combination has not only longer but also fewer seepage paths, as the seepage can only occur through the sand between the concrete blocks. Test set E again had 25 mm of sand plus 50 mm of concrete cover: however, a defect was inadvertently introduced into the subgrade by a fold (wrinkle) in the geotextile. This defect increased seepage by a factor of about 100. As subgrade defects will be impossible to avoid entirely in the field, methods for bonding the seams underwater are needed to assure maximum water conservation. Phaonded Field Seams Phase II of the study examined solvents adhesives for field seaming of PVC geomembranes both underwater and in the dry. The biggest challenge was finding a solvent which could be used underwater, as there has been very little experience in this area. Discussions with manufacturers led to the selection of a specially modified bodied tetrahydrofuran solvent used to repair vinyl swimming pool liners. Test results for PVC seams made both underwater and in air with the special vinyl adhesive are summarized in Table 5. Tests were conducted to determine peel and shear strength after a 24-h cure. Test results indicate that the seams are quite satisfactory and even meet the requirements for factory seams using conventional solvents in the dry. There was also concern about the rate of seam strength development for the transverse field seams that would be needed every 60 m. These seams would be fabricated in the dry with conventional solvents but then very quickly (perhaps within 15 min) subjected to shear stress as they were placed underwater in the canal prism. Seam specimens were fabricated in air with a manufacturer-supplied solvent cement and tested for shear and peel strength after cure times ranging from 5 min up to 4 h. The shear strength developed very quickly (within 5 min) and then decreased with time until reaching equilibrium after 1-2 h. Conversely, the peel strength developed rather slowly and required-30- 60 min to develop fully. Shear strength is the more critical as shear is the predominant stress on the seams during installation and service. Tests were also performed to ensure that specimens, made with conventional solvent and initially cured in air, would continue to cure underwater. Seam specimens were partially cured in air for 5 min and then cured in water for 3 days. These specimens did indeed develop full shear and peel strengths. RESULTS OF EPA STUDY In 1986, Reclamation completed a study for EPA entitled 'Evaluation of Flexible Membrane Liner Seams After Chemical Exposure and Simulated Weathering'. In this study, 37 geomembrane seams, both factory and field were evaluated. The PVC seams included in the study are listed in Table 6. The seams were subjected to six chemical solutions, brine and water immersion, freeze/thaw cycling, wet/dry cycling, heat aging, and accelerated outdoor aging for periods of up to 1 year. Effects of these environmental conditions were evaluated using shear and peel strength tests before and after exposure. The tests were performed under dynamic load at room temperature and under static dead load at 50° C. The rate of grip separation for both the peel and shear tests was kept the same (50 mm/min) to determine if there was any direct correlation between the two properties. Also, a 25-mm wide test specimen was used in both tests. Results of tests conducted on seams subjected to water immersion, freeze/thaw cycling, wet/dry cycling, and heat aging are summarized in Table 7. These environmental conditions are those often encountered in Reclamation's hydraulic applications. TABLE 6           Type of PVC Seams Evaluated in EPA Study     Sample Type of Manufacturer Seaming Seam   No Seam Fabricator Method Width   1 Factory A,C Solvent adhesive 25   2 Factory A,D Thermal-dielectric 19   3 Field Aa Solvent adhesive 50   4 Filed Ab Solvent adhesive 88   5 Filed Bc Solvent adhesive 75 a Solvent adhesive furnished by fabricator C.   b Solvent adhesive furnished by fabricator D.   c Solvent adhesive furnished by manufacturer B.   Test results indicated that except for heat aging, the samples performed satisfactorily with very little change occurring to either the shear or peel strength. The heat aging samples exhibited stiffening due to plasticizer loss from the material. Of the two factory seaming methods used for the PVC, the seams made with the solvent adhesive exhibited higher shear strength, whereas those made dielectrically produced higher peel strength values. The higher shear strength was primarily due to the wider factory seam for the solvent adhesive seam. All failures occurred in the parent material, except for the peel tests on the PVC solvent adhesive seam, where the failure occurred within the seam itself. No appreciable difference was noted in the performance of the two seaming methods however. TABLE 7                       Results of EPA Study on PVC Seams                     Sample 1   Sample 2   Sample 3   Sample 4   Sample 5     Test Condition Shear Peel Shear Peel Shear Peel Shear Peel Shear Peel Original   10 2.6 9.3 6.7 8.3 2.7 9.3 3.4 10.4 4.3 Water immersion at 23°C 6 months 9.9 2.8 9.1 6.6 8.5 3.1 10.5 3.8 10.6 4.3   12 months 10 2.9 9.3 7.3 9 2.7 10.7 3.9 11.7 4.4 Heat aging at 60°C 4 weeks 9.2 3.1 9.3 6.5 8.8 3.8 10.4 4.2 10 4     8 weeks 9.1 3.1 9.2 6.9 9.4 3.2 9.3 4.3 11.3 5.1   13 weeks 10 3.3 9.5 6.9 9.1 4.1 10 4.4 11.4 3.9 Freeze/thaw at: 10 cycles 10.1 2.7 8.9 6.7 8.4 2.4 9.6 4 10.5 4.4   20 cycles 9.7 2.8 9.3 7.3 9.3 3 10 4 12.4 4.7   50 cycles 10.1 2.8 8.4 7.2 8.9 2.7 9.1 3.8 10.4 4.7 Wet/dry at: 10 cycles 10.2 2.7 9.4 6.9 8.4 2.6 10.3 3.8 11.2 6   20 cycles 9.9 2.7 8.5 6.5 8.8 3.3 9.5 3.7 10.2 3.2   50 cycles 9.9 2.7 10.1 6.7 8.2 2 10.6 4.3 10.7 4.6 Note: Test values are expressed as kN/m width of seam. One freeze/thaw cycle consisted of freezing for 16 h at 6.7?C and thawing for 8 h in room temperature water. One wet/dry cycle consisted of 16 h water immersion followed by 8 h of drying at 37.7?C. CONCLUSIONS The Bureau of Reclamation has been using PVC in its buried membrane canal lining work for over 20 years. Results of tests conducted on samples of inservice linings indicate that the factory seams retain excellent shear and peel strength properties with no apparent signs of deterioration. A 1-m overlap, unbonded PVC field seam appears to be adequate for most irrigation canal lining applications, but would not be suitable for landfills or hazardous waste installation where 100% seepage control is required. Results of laboratory tests also indicate that the solvent-bonded field seams can achieve early peel and shear strength development which is advantageous for underwater lining applications. Laboratory tests conducted on an adhesive sealant formulated for the repair of vinyl swimming pool liners indicated that it can be used to make underwater PVC field seams. 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.  REFERENCES 1. Hickey, M. E. Investigations of plastic films for canal linings. Research Report No. 19. A Water Resources Technical Publication. Bureau of Reclamation, Denver, Colorado, 1969.2. Geier, F. H. & Morrison, W. R. Buried asphalt membrane canal lining, Research Report No. 12. A Water Resources Technical Publication. Bureau of Reclamation, Denver, Colorado, 1968.3. Morrison, W. R. & Starbuck, J. G. Performance of plastic canal linings. Bureau of Reclamation Report No. REC-ERC-84-1. Denver, Colorado, 1984.4. Morrison. W. R. & Parkhill, L. O. Evaluation of flexible membrane liner seams after chemical exposure and simulated weathering, US Environmental Protection Agency. Report No. EPA/600/S2-87/0l5, Cincinnati, Ohio, 1987.5. Wilkinson, R. W. Plastic lining on the Riverton Irrigation Project. Proc. ASCE Irrigation and Drainage Speciailty Conference. Flagstaff, Arizona, 1984.6. Starbuck, J. G. & Morrison, W. R. Flexible membrane for closed basin conveyance channel. San Luis Valley Project, Colorado, Proc. International Conference on Geomembranes. Denver, Colorado, 1984.7. Weimer, N. F. Use of polyvinyl chloride liners for large irrigation canals in Alberta. Canadian Geotechnical Journal. 24 (1987) (2) 252-9.    REC-ERC-84-1 PERFORMANCE OF PLASTIC CANAL LININGS January 1984 Engineering and Research Center U. S. Department of the InteriorBureau of Reclamation   Table18. -Physical properties test results for PVC membrane linings on Bugg Lateral. Tucumcari Project, New Mexico, installed spring 196l.- Continued     Sample Sample Sample   Specifications No. B-6764 No. B-7022 No. B-7023 Physical property requirements (14 years (19 years (I 9 years     of service, of service, of service,     BWL) BWL2 ) AWL1) Thickness, mm (mils) 0.25 (10) 0.24 (9.6) 0.24 (9.6) 0.21 (8.2) percent change ±10 -14.3 -14.3 -26.8           Tensile strength, N/mm (lbf/in) 3.0 (1 7) 4.2 (24.2) L3 4.6 (26.4) L 5.0 (28.6) L     4.6 (26.1) T4 5.2 (29.8) T 4.7 (26.9) T percent change -5.5 L +3.1 L +1 1.7 L     +14.5 T +30.7 T +18.0 T           Elongation percent 225* 268 L 211 L 151 L     274 T 188 T 188 T percent change -35.0 L -48.9 L -63.3 L     -40.7 T -59.3 T -59.3 T           Modulus at 100 percent Not required 2.4 (13.8) L 3.6 (20.5) L 4.6 (26.0) L elongation, N/mm (lbf/in) 2.4 (13.8) T 4.2 (23.9) T 4.2 (23.9) T percent change +21.1 L +79.8 L +128.1 L     +34.0 T +132.0 T +132.0 T           Elmendorf Tear, grams 1500* 3000 L 3000 L 450 L     2865 T 2200 T 1300 T percent change +63.9 L +63.9 L -75.4 L     +25.1 T -3.9 T -43.2 T           Impact resistance Not more than 2 5 tested Not Not   specimens out determined determined   of 10 shall fail 5 failures       at -18ºC (0ºF)               Plasticizer content, percent Not required 34.1 27 21.6 percent change -14.3 -32.2 -45.7           Bonded seam strength, 65 Not Not Not percent of parent material determined determined determined           1 AWL denotes above normal waterline   2 BWL denotes below normal waterline   3 L denotes longitudinal direction     4 T denotes transverse direction     * Minimum, each direction         Canal data: Established     seepage   b = 5.00 ft, d =4.40 ft, s:s =1.5:1, and   rate   WP =20.86 ft. (7.4806 gal/ft3) (2169 ft2)   Length =104.25 ft.     Average seepage rate for section is 8.2 = 0.0005 (ft3/ft2)/d gal/d.   Reach 5A, station 599+00, PVC lined: Seepage section has a wetted surface of (104)(2y0.86) = 2169 ft2. Canal data:   For more information call   800-OK-LINER  today!

PVC in Arch Dam Repair The use of a geomembrane for an arch dam repair By G. Zuccoli, C. Scalabrini and A. Scuero, General Manager*, Technical Manager* and Technical Manager** Reprinted from Water Power & Dam Construction, February 1989  A geomembrane was recently used in Italy to repair the upstream face of a double curvature arch dam. The authors describe the process and give details of a number of tests that were conducted in the laboratory to verify properties of the membrane used. Publino dam, a 40 m-high double curvature arch dam with a crest length of 250 m, was built in 1951. It is located at an elevation of 2135 m. The dam, which is provided with a de-icing plant on the upstream face, has a reservoir capacity of 5 x 106 m3. It is used as seasonal storage for hydroelectric power generation and pumping. Publino dam can be reached from the valley floor by both cable and narrow gauge railways: most of the route is in tunnels, for an overall length of 11 km. In 1988 widespread deterioration of the surface of the upstream face of the dam was observed. Further investigation showed that up to 30 percent of the 5500 m2 cement rendering had become detached. This condition indicated that the permeability of the structure would rapidly increase if no remedial work were carried out. Although the losses at full storage capacity were only 0.25 l/s. Sondel (the owners of the structure) decided to carry out the rehabilitation of the upstream face as a preventive measure. rather than wait for any further deterioration. It was considered that any delay in this work would make the necessary operations expensive, in terms of both the extent of the operation and the loss of hydro production. Refurbishment method On the basis of work carried out previously by ENEL (the Italian national power authority) on gravity dams. Sondel decided to use a synthetic, waterproof, drained membrane to protect the upstream face. Experience had shown that these membranes could be installed rapidly with mechanical anchorage and with minimal preparatory operations on the underlying concrete support. The system adopted was the same as that already used on the Miller, Lago Nero, Piano Barbellino and Cignana Molato dams. In this system, the impermeable facing is a geocomposite consisting of a very thick flexible synthetic PVC membrane (characterized by high resistance to aging) which was prefabricated and heat-welded to a polyester geotextile during production. Paired stainless-steel sections (ribs), placed vertically and fitted to the body of the dam with small anchors, fasten the geomembrane to the dam face. These pairs of sections also act as non-pressurized drainage collectors for water condensing, behind the membrane. The water collected is conveyed to the heel of the dam, where a perimeter drainage pipe conveys it through the drainage gallery, downstream of the body of the dam. The membrane is manufactured in sections of sufficient length to cover the whole height of the dam, thus avoiding horizontal joints. The vertical joints and the corresponding mechanical anchorages are covered with an additional strip of the same membrane. The mechanical anchorage of the membrane makes it possible to keep the protective facing independent of the facing behind so that construction and expansion joints in the original structure are waterproofed at the same time. (The anchorage ribs are simply placed on either side of the joint, and covered with the waterproof facing.) The system constitutes an efficient drainage system for the body of the dam: the presence of the layer of geotextile draws off the water present within the body of the dam, which tends to stabilize its moisture content. The finished appearance of the installation is satisfactory from an aesthetic point of view: the membrane is a uniform grey colour. The membrane adheres well to the face thanks to the mechanical anchorage, which avoids any sagging or bulging of the material. The solution adopted does not involve any stability reappraisal, since the membrane itself, and the ribs which support it, are comparatively light. The drainage collector, installed along the upstream perimeter of the foundation of the Publino dam, is a stainless steel omega-sectioned bar, fixed externally to the body of the dam. This bar also acts as the sealing element for the base of the membrane sections, as well as connecting with all the vertical ribs. The water collected is drained off through one of the original drainage pipes inserted in the body of the dam. Climatic conditions From an operational point of view, the system adopted allows work to be carried out even in harsh climatic conditions, which would make the adoption of other solutions (such as mortar with resins) difficult, uncertain, and more expensive. In fact, all the components of the system are manufactured and prepared in the factory under controlled climatic conditions. The only operations which take place on site are of a mechanical nature: with other solutions there could be problems with chemical behaviour (polymerization, gelling, and so on) and physical behaviour (viscosity, distribution, and so on), which are often the cause of poor results. Transportation The overall quantity of material necessary for the geocomposite solution is relatively small. This makes the solution particularly suitable in cases of difficult access to the site, as at Publino dam. Also, limited volume of equipment is necessary for this method: only suspended platforms (quickly and easily constructed and dismantled) and small tools (drills, welder, and so on) are required. Installation In the case of the Publino dam, it was planned to waterproof the entire face, which meant that the reservoir had to be completely emptied. Normally the time required for installing the stainless steel sections is approximately 40 percent of the total time needed for the whole operation. However, this installation can be carried out at various stages, according to the water level in the reservoir, using, platforms suspended from the crest of the dam. At Publino, in June and July 1988, the deteriorated parts of the cement rendering were removed from the face, the upstream heel of the dam was cleaned, the perimeter drainage pipe was constructed and the lower vertical sections of the support for the geomembrane were installed (working in horizontal bands).   At the same time, other general work was carried out, such as the complete overhaul of the bottom outlet valve. By the beginning of August, the reservoir was back in operation. The installation of the vertical sections continued, using platforms suspended above the water level, which was continually rising. Placement of the vertical sections continued until October 1988. At the beginning of the summer 1989 season, corresponding with the minimum water level, the reservoir be completely emptied for another month, for the installation of the geocomposite. Therefore, the rehabilitation will be completed over two seasons (representing a total of eight months). The careful planning, of such work should cause minimum interference with the running of the plant and consequently low operational losses. Concrete face preparation It was possible to accelerate the overall installation time because the thick geomembrane (2.5 mm) heat bonded to a 500 g/m2 geotextile, does not require laborious preparation of the concrete face. At Publino, only the deteriorated part of the rendering was removed (using light electric scrapers). The surface after scraping, although rough, is generally considered suitable for laying the geomembrane. A very small amount of patching was done (approximately 3 percent of the total surface), using pozzolan cement, on those parts of the face which were particularly pitted, exposing aggregate with sharp edges. This was decided on the basis of experimental investigations carried out by ENEL at their Hydraulic and Structural Research Centre (ENEL-CRIS). Durability of the system The solution adopted has until now proved to be very reliable, since similar installations carried out up to ten years earlier (for example Lago Miller, 1976) have not shown any deterioration compared with their initial performance. Whenever the partial substitution of the waterproof geomembrane becomes necessary, the operation is very quick and inexpensive compared with the initial installation. The geocomposite The geocomposite chosen for the Publino dam is designated Sibelon CNT 3750, which consists of a 2.5 mm-thick geomembrane manufactured with a PVC mix, heat-bonded during production to a 500 g/m2 polyester felt geotextile. Great care was taken over the choice of the plasticizer added to the basic mix, so as to obtain a geomembrane with good performance in view of the difficult climatic conditions. The material constituting the membrane has been subjected to an extensive series of laboratory tests, both in Italy, at independent University institutes and independant research centres, and abroad, at laboratories belonging to public institutions. These tests have confirmed the good balance of the material. The geomembrane incorporated in the composite has shown the following mechanical characteristics: very low permeability (Darcy coefficient k less than 1 x 10-12 cm/s); non-degradability; good tensile strength (exceeding 285 percent elongation at breaking load); excellent flexibility and elasticity (almost complete spring back, even at loads close to breaking load); good resistance to low temperatures (no sign of cracking after folding test at -35° C); excellent bending fatigue limit (no breakage after 1 x l06 repeated flexions); good resistance to abrasion; optimal chemical inertia; ice-repellence; resistance to damage by flora and fauna: and, good performance of the heat-welded joints. These mechanical characteristics are further enhanced when the geomembrane is heat-bonded to the geotextile. The functions of the heat-bonded to the geotextile are: to increase the dimensional stability of the geomembrane; to provide diffused drainage of the waterproofed surface, drawing off and then draining the waters of infiltration and condensation; and, to cushion the geomembrane and protect it from possible puncture on the rough surface of the existing face. An interesting laboratory elasticity test was carried out. A sample of geomembrane (2 mm thick, and 20 cm in diameter) used on the Lago Nero dam, was placed on a rigid 5 mm-thick support with a slit in the centre, 50 mm long and 5 mm wide. Hydraulic pressure of 20 bar was applied to the sample. A 1.9 mm deflection was measured on the part of the membrane which corresponded with the slit: this returned to its original position within about 10 min of the pressure ceasing. The performance of the membrane remained constant over several repetitions of the test. This test carried out on a sample without a geotextile, shows the excellent resistance of the membrane even if it were fixed directly onto very rough or pitted surfaces. Another laboratory test carried out by ENEL-CRIS involved the application of cycles of hydraulic pressure up to 20 bar on pieces of geomembrane 2 mm thick, bonded to a 200 g/m2 weight geotextile, placed on samples of very rough surfaces which were taken from the deteriorated faces of existing dams. The membrane behavior was as follows: no perforation or laceration occurred, indicating that the membrane had remained waterproof: and, immediately after the test, the PVC material showed the imprint of the underlying surface, but within one hour of the end of the test, the membrane had returned to its original smooth condition. Also in connection with the application of PVC geomembranes to dams, ENEL-CRIS carried out a series of tests regarding the aging of the material, analyzing samples, of membrane taken from dams that had been functioning for more than ten years. The samples were taken from areas above the maximum storage level, which had therefore been exposed to the light constantly. Compared to the initial values, the results of the mechanical tests showed a deterioration of about 22 percent in the tensile strength and approximately 20 percent in the elongation at breaking load: this performance is excellent, considering the high initial values used as the reference. The possible chemical alteration of the polymer with time was tested by infrared spectrophotometry. Absorption tests were carried out on two different samples, exposed and not exposed to ultraviolet rays: the resulting graphs showed the same pattern. It can be concluded that, as far as aging in natural conditions is concerned, the PVC geomembranes used so far show no sign of deterioration in their chemical structure, and therefore in the chemical additives which give the material its mechanical performance. Conclusions Waterproofing the upstream face with a mechanically anchored PVC geomembrane offers a number of advantages:  efficient protection of the construction and expansion joints:  drainage of the body of the dam: and,  simple and rapid installation which does not require expensive surface preparation and is long-lasting. In addition, the installation costs are competitive, but, since the membrane does not require maintenance and is durable over a long period of time, the overall costs are well below those of a traditional facing. Acknowledgment Planning of the Project and work on the waterproof facing were carried out by CARPI, and the preparation of the face was carried out by the same company in direct collaboration with Sondel. Bibliography Scuero, A., "RCC Dams, Upstream Face Waterproofing" ASCE Specialty Conference. San Diego, USA: March 1988. Cazzuffi, D., "The use of geomembranes in Italian Dams": Water Power & Dam Construction, March 1987. Koerner, R. M., Designing with Geosynthetics". Prentice-Hall. Englewood Cliffs, New Jersey, USA: 1986 Monari, F. "Waterproof Covering for the Upstream Face of the ‘Lago Nero’ Dam", Proceedings International Conference on Geomembranes, Denver, Colorado, USA: 1984.   For more information call   800-OK-LINER  today!

There has been much written regarding the use of PVC vinyl products in water pipe, medical applications, toys, packaging and other consumer applications.  Some fanatical groups are advocating the ban of vinyl and chlorine throughout the world. Their claims of dangers of vinyl, based on outdated studies, inconclusive reports, and "junk science" continue to be disproved by sound scientific research conducted by reputable scientists and by the vinyl industry. Here are a few examples: New Phthalate study is PVC’s Koop d’etat The PVC industry had the world's attention June 22, 1999, and for a change it was happy to be in the spotlight. Former U.S. Surgeon General C. Everett Koop pronounced phthalates completely safe in medical devices and toys. His declaration was reported widely in the popular press. This is the same press that a year ago had never heard of phthalates, but just seven months ago helped bully retailers into pulling soft vinyl toys from store shelves. A variety of commentators picked up on Koop's study, and Koop himself authored an opinion piece for the Wall Street Journal. Much of the coverage made a connection between his study and a report on the safety of silicone breast implants. The commentators criticized the trend toward "junk" science that attacks products with anecdotal evidence that doesn’t stand up to the rigors of scientific inquiry. In this celebrity-crazed era, a stamp of approval from Koop seems to be just the prescription that the vinyl industry needed. Koop was arguably the most visible surgeon general in U.S. history. He used the office as a bully pulpit, and in the process won a gold-plated reputation as an advocate for public health. Critics attacked the Koop study, arguing that the American Council on Science and Health, which organized the project, was funded by, and therefore a pawn of, chemical industry interests. Given Koop's stature, it will be difficult to make that charge stick. The key now will be for the vinyl industry to sustain its success. It needs to reinforce Koop's conclusion and create a public perception that vinyl products are safe. It needs to convince a few former customers to shift course publicly and go back to using PVC. In the meantime, it should continue to support research into the safety of PVC, as well as research and development efforts to make vinyl resin production, use and disposal as safe as possible. This article is from Plastic News Magazine, July 5, 1999 as shown in the Viewpoint.   TV: In an interview on CBS This Morning , Dr. Koop stated that the medical profession has over 40 years of historical data showing the safety of vinyl products used in health care applications.  He stated that the use of phlalate plasticizers in medical applications has proven to be a safe and cost effective practice, and that consumers should not be concerned with its use in health care.  Here's another... NEW ORLEANS - Baxter International Inc. , a leading supplier of medical products, wants to set the record straight regarding its use of flexible PVC. The Deerfield, III.- based firm was thrust into the spotlight in April when, after shareholders expressed concern about alleged health problems resulting from PVC use, Baxter officials said the company would continue its effort to find alternatives to vinyl products. In a June 24 speech at Flexpo 99 in New Orleans, Baxter technical director K.Z. Hong said the company had been reviewing alternate materials for several years. "We’re constantly searching for better materials," Hong said. "People were asking us why we were resisting change, and that’s totally contrary to the truth." Hong said Baxter has replaced rigid and semirigid PVC applications such as blister packaging and drip chambers as superior replacement materials were developed. Flexible PVC also has been replaced in applications including bags for pre-mix drugs and some blood products such as platelets. But in most flexible PVC applications, competing materials haven't been able to match the variety of attributes PVC can offer, he said. Materials aiming for PVC’s medical uses include thermoplastics elastomers and metallocene or single-site-enhanced grades of polyethylene and polypropylene, as well as numerous blends, alloys and multilayer laminates made from those materials. Hong laid out those criteria in a three-tiered, pyramid-shaped diagram, with basic attributes on the bottom and difficult ones on top. By volume, 80 percent of medical PVC applications require materials that can reach the third level. Hong also repeated Baxter’s belief that PVC is not harmful in medical uses. Greenpeace and other activist groups have claimed that phthalates used in plasticizers can leach out of PVC blood bags and intravenous tubing and enter the bloodstream. Most potential replacement materials are significantly more expensive than PVC. But Hong said the cost factor has been exaggerated in some accounts. "There's been a misleading impression that we've overemphasized the cost, and that makes Greenpeace think we're only thinking of dollar signs," Hong said. "That's totally untrue. The first item on our list of material-selection criteria is the safety of the end users. The material must first do no harm to patients." Hong added that PVC has more than 40 years of safe and effective clinical use working in its favor. That history adds up to at least 5 billion patient days of acute exposure to PVC products and at least 1 billion patient days of chronic exposure. "The PVC experience has been very unique," Hong said. "The material is unchallengeable today, but maybe tomorrow that will change." Baxter has done a good job of handling the PVC issue so far, according to Robert Brookman, vice president of Teknor Apex, a PVC compounder headquartered in Pawtucket, R.I. "Initially, I was shocked at what [Baxter] said, when it sounded like they were actively seeking to replace PVC," Brookman said. "But when the company followed up and straightened things out, I felt more comfortable with it." Brookman added that PVC’s history of widespread medical use, combined with research such as former U.S. Surgeon General C. Everett Koop's recent study, are proof of the material's safety. "This argument doesn't have a leg to stand on," Brookman said. "There's no sound data that shows PVC is medically harmful." This article was written by Frank Esposito and published in the Plastic News Magazine, July 5, 1999 edition.

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.   For more information call   800-OK-LINER  today!

EPI specializes in the fabrication of flexible PVC geomembrane liners. The liner materials meet or exceed the PGI 1197 specification which replaces the NSF-54 standard, and are custom fabricated in many shapes and sizes for various applications.  Panels can also be fabricated as "stepped" panels to fit irregularly shaped containments .  This reduces wasted material from conventional rectangular panels. Read below to learn how to properly execute a PVC panel deployment. The liners are accordion folded in two directions. After the liner is fabricated, it is folded onto a wooden pallet. When finished the liner is marked on the top with the necessary information for installation. The liner is also marked with the material type, dimensions, serial number, and the customer's name.                  When unpacking note a long arrow with a shorter arrow on one side. Figure #1 illustrates the markings on top of the liner: Figure 1. The long arrow indicates the first direction the liner unfolds off the pallet as shown in Figure #2: Figure 2. The short arrow indicates the second direction the liner should unfold to reveal the finished product shown in Figure #3. Figure 3. EPI marks an L-shaped arrow on every liner fabricated. The short arrow does not always appear on the same side of the long arrow. Still have questions? Give us a call: 800-OK-LINER (800-655-4637)

It is likely that you have chosen a PVC liner for your project because of its durability, flexibility, and resistance to chemicals and UV radiation. However, in order to ensure its longevity and optimal performance it requires proper maintenance. Here are our tips for maintaining PVC liners: 1. Conduct regular inspections. Regular inspections can help identify potential issues early on, allowing them to be fixed before they turn into a much larger issue. During your inspection look for signs of damage, such as punctures, tears, or wrinkles. 2. Regularly clean the PVC liner. Removing dirt, debris, algae, and other contaminants helps to ensure the durability of the liner. The best way to clean the PVC liner is by using a soft brush or cloth to lightly scrub the surface. 3. Avoid using sharp objects near the liner. It is important to be cautious when working near or on the liner and ensure that tools, equipment, and other objects with sharp edges do not come into contact with it. The slightest puncture can compromise the liner’s entire integrity. 4. Repair any minor damages. If during your inspection or when working you notice small punctures or tears, repair them immediately with a compatible PVC liner repair kit. 5. If your PVC liner is being used in a pond or pool, regularly monitor and maintain the appropriate water chemistry levels. Extreme pH levels and high concentrations of certain chemicals can degrade PVC liners over time. It can be useful to consult with a water chemistry expert about the appropriate levels and care. 6. Protect your liner from chemicals, UV radiation, and/or algae. Most PVC liners can come with resistant coatings to help protect the liner from these damaging factors. For example, if your liner will be directly exposed to sunlight, you can use a UV-resistant coating to help extend its life. Another useful tactic if your liner is being used with water is to install the correct filtration and circulation system to help limit algae growth. 7. Manage extreme temperature fluctuations. Significant temperature variations can affect the flexibility and longevity of PVC liners. If your liner is in an environment with significant temperature variations — extreme hot weather or extreme cold or switching from both — consider investing in insulation or protective coverings for your liner. This will help protect it and help make it last longer. 8. If not using your liner, properly store it in a cool, dry place. Before storing it make sure it is clean and completely dry. Choose a place that is away from direct sunlight and extreme temperatures, to help prevent premature degradation. PVC liners can maintain a high-level performance for a long time if properly maintained. By following the above tips and taking proactive measures to protect your PVC liner, you can ensure it serves its purpose effectively for years to come. Our experts at EPI can also help advise you on the best care and maintenance of your liner so that you are able to save money while also protecting the environment. Have a questions? Give us a call: 231-943-2266

EPI's PVC fabricated geomembrane liners are single-ply construction. Polyvinyl Chloride is the main polymer. EPI uses only first quality virgin resins and each material meets or surpasses the  ASTM D 7176 minimum specifications* for materials and ASTM D 7408 minimum specifications for seam strength.** PVC Liners are fabricated by EPI in panel sizes up to 40,000 square feet, accordion-folded in both directions, and packaged for shipment to your site—our process helps you get your liner installed quickly and easily to save you time and money. EPI uses statistical process control (SPC) to ensure the quality and integrity of each panel we produce. EPI is the only fabricator to remove samples from actual factory seams during the welding process for a rigorous, proven testing procedure that assures you of the highest quality factory-fabricated PVC geomembranes available. Benefits of EPI PVC Geomembranes: Flexibility for three-dimensional performance. Larger Panels: Up to 80% fewer field seams. Long-term survivability. Custom size and shaped panels. Most orders ship within 72 hours. Typical Applications: Landfill Closures Irrigation Ponds Oil Drilling Reserve Pits Soil Remediation Decorative Water Features Waste Water Lagoons Mining * ASTM D7176 has replaced the no longer published National Sanitation Foundation Standard 54 for flexible membrane liners. ** ASTM D7408 is the new standard specification for PVC geomembrane factory and field seams(chemical, adhesive, dielectric, hot air, and hot wedge)

PVC Geomembrane Research Negates Film Tearing Bond Requirement Daniel S. Rohe, President Environmental Protection, Inc., 9939 US Hwy 131 South NE, Mancelona, MI 49659PH (800) 655-4637; FAX (231) 587-8020; email: danrohe@geomembrane.com ABSTRACT Current research being done at EPI with PVC Geomembrane demonstrates the physical characteristics of PVC Geomembrane material outperforms normal design criteria. This paper will show that PVC Geomembrane seams can acclimate to 200% elongation without an issue in the integrity of the seam. PVC Geomembrane can accommodate 200% movement without failure. If the landfill or containment project can’t accommodate 200% movement without catastrophic failure, why are we trying to make FTB seams in PVC Geomembrane that don’t reach failure until +400% elongation? Film tearing bond(FTB) has been preached by the geomembrane industry as the minimum standard criteria for years. FTB is required of HDPE materials requiring the seam to be stronger than the material itself, while the material has functional elongation less than 20%. This simply isn’t the case with PVC because of its high elongation, ability to conform and adjust to minor soil movement. PVC Geomembrane material with a normal strength seam of about 10 lbs per inch width can withstand 200% elongation without seam failure. Requiring the welding process to create FTB in the seam at the expense of raw material properties sacrifices the ultimate goal of geomembrane integrity. A wide sampling of seams in 0.75mm and 1.0mm PVC Geomembrane have been elongated and held at 100% and 200% elongation in a custom built apparatus for over a year. No failures in any of the variety of seams have been observed to date in this ongoing test. The research conducted by EPI will be presented in this paper. Background on PVC Geomembrane Standards One of the first industry standards was the National Sanitation Foundation Standard 54 (NSF-54)1 in 1983. This industry standard was created by geomembrane industry professionals in a consensus agreement. The last revision was in 1993 and subsequently, the National Sanitation Foundation withdrew their support of Standard 54. The geomembrane industry continued to use it and reference it. Amazingly almost 20 years after it was abandoned, some projects still refer to it. In 1996 the PVC Geomembrane Institute (PGI) filled the void when they published their consensus specification on January 1, 1996 (PGI-1196)2. Subsequent versions were also released, PGI-1197, PGI-1103 and PGI-1104. The PGI Specifications failed to become the industry standard the organization had hoped. The Technical Director at Canadian General Tower, Ltd approached ASTM to create a material specification that would carry the credibility of the ASTM Organization. In 2006, ASTM D7176 Standard Specification for Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes Used in Buried Applications was published. This was followed by ASTM D7408 Standard Specification for Non Reinforced PVC (Polyvinyl Chloride) Geomembrane Seams in 2008. These are now the industry standard. While film tearing bond(FTB) is not technically spelled out as a requirement in current industry standard specifications for PVC Geomembranes, we commonly see this requirement carry over from the polyethylene world. In ASTM D6392, it refers to and directs the laboratory to measure peel incursion. If a seam is only acceptable with less than 25% peel incursion, that means the parent material sheet fails before the seam peels open. When this protocol is carried over to a PVC project, the requirement is essentially the same as requiring FTB. It may not be written in current industry specifications, but we see this requirement commonly carried over in projects during the copy & paste of new project specifications. The other common scenario comes up during the installation of PVC Geomembranes when the CQA Technician, who only has experience with polyethylene, tries to apply what he/she knows directly to the PVC Geomembrane. The standards and requirements are very different because these materials are very different. The relationship between peel and shear There is a relationship between peel and shear as it applies to seam strengths but there is a very distinct difference between the function of peel strength and shear strength. Shear stress is the stress on the seam when the top sheet and bottom sheet are pulled in opposite directions. Shear mode is representative of the stress normally seen in the field. Peel testing is a full frontal assault on the seam to verify its internal strength by peeling the sheets apart. Peel mode is rarely seen in the field and only if there is a flap on the seam. Thermal fusion seams can be made with abnormally high peel strengths by using excessive heat or excessive pressure but this comes at the expense of shear strength. Creating a seam with abnormally high peel strengths can damage the edge of the seam, deform the seam or thin the material which will cause the shear strength of the seam to decrease significantly. Since shear strength applies in the field and peel strength applies in the laboratory, it is counterproductive to produce seams with high peel strength and reduced shear strength therefore accommodating a laboratory requirement at the expense of durability in the field. Peel Strength For the purpose of this paper, we will focus specifically on peel strength requirements. The peel strength requirements for 0.75mm (30mil) and 1.0mm (40mil) are the same at 2.6 kN/m (15 lbs/in) and specimens of both material thicknesses were tested in our research. Table 1. Seam Strength Requirements for 25.4mm wide (1inch) specimen Standard Minimum Values Peel Strength0.75mm (30mil)and 1.0mm (40mil) Shear Strength0.75mm (30mil) Shear Strength1.0mm (40mil) NSF-54 1.8 kN/m (10 lbs/in) 9.9 kN/m (55.2 lbs) 13.3 kN/m (74 lbs/in) ASTM D7408 2.6 kN/m (15 lbs/in) 10 kN/m (58.4 lbs/in) 14 kN/m (77.6 lbs/in) Minimum Strength Required There is a minimum amount of peel strength needed to ensure a good seam that performs as intended without failure. When industry standards for PVC geomembrane were first introduced, 1.8 kN/m (10 lbs/in) was the agreed upon minimum requirement. After more than a decade of experience, the PVC geomembrane industry agreed that 2.6 kN/m (15 lbs/inch) was achievable in 0.75mm (30mil) and thicker PVC geomembrane seams and increased the industry minimum peel strength. That is where the minimum specification stands today. The author agrees that this minimum peel strength needs to be achieved to maintain a high quality seam. Long Term Testing of Elongated Samples After being asked why PVC Geomembrane can’t meet FTB on seams for so many years, EPI decided to do some research into what a seam can withstand. One of PVC geomembrane’s significant advantages is its flexibility and elongation properties. Typical samples can range from the minimum 380% up to 550% elongation at break. We asked ourselves the question, at what point is the performance of the seam stronger than the field application? Creating a seam with exceptional peel strength (0% peel incursion or FTB) while potentially sacrificing the shear strength of the seam is ultimately counter-productive. This author believes that there is a point in the design where the project fails before the physical properties of the geomembrane fails. If the typical 2.6 kN/m (15 lbs/in) seam exceeds the project design and the factor of safety, then why require a seam with FTB (0% peel incursion)? Extension & Hold More than a year ago, we took samples and elongated them in our laboratory. For the purpose of this research, we initially chose an elongation/movement of 100%. To increase the level of confidence, all the testing was mirrored at 200% elongation. There were several seams made using chemical fusion welding with peel specimens cut from opposing ends and tested in the tensiometer to bracket a consistent seam. These specimens gave us information on the peel and shear strength of the seam. Four seams that were consistent and had constant peel strength were chosen at 3.0 kN/m (17 lbs/in) and 4.7 kN/m (26 lbs/in) for both 0.75mm (30 mil) and 1.0mm (40 mil) thickness. Figure 1.) Typical Custom Clamp Custom specimen clamps were fabricated (see Figure 1) to grip the specimen after each specimen was elongated in the tensiometer. Each specimen was elongated to 100% or 200% elongation in the laboratory Instron tensiometer with the seam centered in the specimen. The custom clamp was then used to clamp onto the specimen just inside the tensiometer grips and hold the seam under tension. The tensiometer grips were then released and the specimen was removed. This was repeated 9 times for each sample on March 11, 2009 (see Table 2). These clamped samples were then stored in the warehouse where they wouldn’t be physically disturbed (see Figure 2). The samples were inspected daily for the first 90 days and then weekly since then. The inspection on May 20, 2009 revealed a broken sample #4. It is believed the sample was scored or deformed by burrs on the clamp which prematurely caused it to tear at the clamp. The clamp was smoothed off and a new specimen was prepared, clamped and hung back with the samples. It is important to note the sample failed at the edge of the clamp and not anywhere in the seam.  Table 2. Sample Identification Log Sample Elongation Material Seam Strength Seam Type Sample 1 100% 0.75mm (30 Mil) PVC 3.0 kN/m (17 lbs/inch) Chemical Sample 2 100% 1.0mm (40 Mil) PVC 3.0 kN/m (17 lbs/inch) Chemical Sample 3 200% 0.75mm (30 Mil) PVC 3.0 kN/m (17 lbs/inch) Chemical Sample 4 200% 1.0mm (40 Mil) PVC 3.0 kN/m (17 lbs/inch) Chemical Sample 5 100% 0.75mm (30 Mil) PVC 4.7 kN/m (26 lbs/inch) Chemical Sample 6 100% 1.0mm (40 Mil) PVC 4.7 kN/m (26 lbs/inch) Chemical Sample 7 200% 0.75mm (30 Mil) PVC 4.7 kN/m (26 lbs/inch) Chemical Sample 8 200% 1.0mm (40 Mil) PVC 4.7 kN/m (26 lbs/inch) Chemical Sample 9 100% 0.75mm (30 Mil) PVC 3.1 kN/m (18 lbs/inch) Thermal The warehouse where these samples are stored is not temperature controlled and the samples have been subject to the temperature extremes of Northern Michigan summer and winter. Normal temperatures range from -23°C(-10°F) to 35°C(95°F). We observed no changes in the samples during the temperature variations. Figure 2. Samples Stored in Warehouse Film Tearing Bond (FTB) Film tearing bond is the requirement that the bond of the seam is stronger than the parent film and the film itself fails before the seam fails. This requirement applies to high density polyethylene(HDPE) films because they have such a small window of functional elongation. When the HDPE material only elongates 50% before it breaks5, it’s very important that the seam never comes apart. PVC geomembrane has a completely different molecular structure which gives it excellent elongation properties. While the PVC material does thin out as it is elongated, it does not exhibit any yield point typical with polyethylene. At 200% elongation the 0.75mm (30mil) and 1.0mm (40mil) PVC geomembrane did not exhibit any failures in peel or shear mode. Conclusion At the time of this writing, it has been 15 months now without a single specimen failing in the seam. It’s hard to imagine a landfill slope or a lagoon that could withstand over 200% movement without a catastrophic failure. PVC geomembrane is a resilient material that can easily withstand up to 200% strain without failure in a 3.0 kn/m (17 lbs/inch) seam. Creating a FTB seam which sacrifices the integrity of the PVC material and/or results in a lower shear strength value detracts from the overall performance of the PVC geomembrane. Therefore universally applying the FTB requirement from other materials simply isn’t applicable to PVC Geomembranes in most applications. REFERENCES NSF Standard 54, NSF International, Ann Arbor, Michigan, USA PVC Geomembrane Institute Specification 1196, PVC Geomembrane Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA ASTM D6392 Standard Test Method for Determining the Integrity of Nonreinforced Geomembrane Seams Produced Using Thermo-Fusion Methods, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D7176 Standard Specification for Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes Used in Buried Applications, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. ASTM D7408 Standard Specification for Non Reinforced PVC (Polyvinyl Chloride) Geomembrane Seams, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA. GRI Test Method GM19, Geosynthetic Institute, Folsom, Pennsylvania, USA   For more information call   800-OK-LINER  today!

The Importance of PVC Geomembranes in Agricultural Applications In the realm of modern agriculture, the need for innovative and reliable solutions to manage water resources, prevent soil erosion, and contain harmful substances is more critical than ever. This is where PVC geomembranes, a specialty of Environmental Protections Inc. (EPI), play a pivotal role. Since its inception in 1980, EPI has been at the forefront of delivering environmental solutions, driven by a commitment to sustainability and innovation. Why PVC Geomembranes Matter PVC geomembranes are synthetic materials used extensively in agricultural applications due to their flexibility, durability, and impermeability. These properties make them ideal for lining irrigation canals, reservoirs, ponds, and even manure lagoons. In agriculture, where the efficient use and conservation of water are paramount, PVC geomembranes ensure that water loss through seepage is minimized, helping farmers maximize the efficiency of their irrigation systems. Moreover, these membranes serve as a barrier to prevent contaminants from leaching into the soil and groundwater, protecting the environment and ensuring the safety of agricultural products. EPI's Leadership in PVC Geomembrane Technology EPI has distinguished itself as a leader in the geomembrane industry, particularly in the development and implementation of advanced technologies for PVC geomembrane fabrication and installation. Among the cutting-edge techniques employed by EPI is Dual Track Welding, a method that ensures the highest level of seam integrity and durability. This technique, combined with Air Channel Testing using Thermal Welding, allows for thorough inspection and quality assurance of the seams, which are critical points in any geomembrane installation. EPI's dedication to excellence is further exemplified by its involvement in the development of the Wolschon Test, an accelerated testing procedure named after its developer, Mark Wolschon. This test is instrumental in assessing the long-term performance and durability of geomembranes, ensuring that they meet the rigorous demands of agricultural applications. EPI's Contributions to Industry Standards EPI's influence extends beyond just manufacturing and installation. The company has played a significant role in shaping industry standards for PVC geomembranes. EPI worked closely with TRI (Texas Research Institute) and the PGI (PVC Geomembrane Institute) to develop a process for air channel testing of PVC field seams, a critical advancement that enhances the reliability of geomembrane installations. EPI initiated the specification process at ASTM (American Society for Testing and Materials), with Mark Wolschon serving as the Task Group Leader and author of the specifications ASTM D7177 and ASTM D7408. These specifications have become benchmarks in the industry, providing guidelines for the quality assurance of PVC geomembranes and setting a high standard for environmental protection in agricultural applications. In summary, PVC geomembranes are indispensable in modern agriculture, offering a reliable solution for water conservation, soil protection, and containment of harmful substances. Environmental Protections Inc. (EPI) has been a trailblazer in this field, leveraging cutting-edge technology and industry expertise to deliver high-quality geomembrane solutions. EPI's commitment to innovation and environmental stewardship not only benefits the agricultural sector but also contributes to the broader goal of sustainable development. As the demand for efficient and eco-friendly agricultural practices continues to grow, EPI's role in providing top-tier PVC geomembrane solutions will undoubtedly remain vital.

FIVE QUESTIONS FOR ANDRÉ ROLLIN: FUNCTIONAL PVC GEOMEMBRANES Geotechnical Fabrics Report: Regardless of the application for which a geomembrane is used, we often refer to the geomembrane by its general category, such as “a PVC geomembrane,” and leave it at that.  But this really does not say enough.  In the case of PVC, what is its core composition? And how does this affect its many formulations? Andre Rollin : Polyvinyl chloride (PVC) has been produced since 1835.  In 1932 a plasticizer that could be added to the PVC formulation resulted in the production of a wide range of flexible products.  Flexible PVC geomembranes were introduced to the market in the 1950s. PVC is produced from petroleum fractions (ethylene and acetylene) and chloride by means of a suspension polymerization performed in reactors where vinyl chloride and an initiator are dispersed in water.  Reaction time and temperature are set to control the molecular weight of produced chains (polymerization levels).  Since PVC is a rigid material, a plasticizer that can lower attraction forces between hydrogen and chloride molecules is incorporated to lower the brittleness temperature.  A PVC flexible material is composed of crystallite areas surrounded by amorphous areas into which the plasticizer is located.  The maximum quantity is controlled by the desired permeability of the product – generally in the range of 28 to 35% by weight. Plasticizer is not the only product added to a PVC geomembrane blend: Heat stabilizers, color pigment, lubricant, biocide, and others ingredients are added to resist solicitations.  A PVC geomembrane must be considered as a complex recipe incorporating many ingredients in proportion, such as 35% polymer, 28 to 35% plasticizer, 0 to 20% filler, 5 to 10% of antioxidants, and 2 to 3% of other products.  The proportion and quality of the ingredients in a blend can be set to match climatic conditions, nature of stored liquids, and other parameters.  Functional formulations of PVC geomembrane can be achieved to offer characteristics differing greatly from one product to another.  The end product might be for general use, potable water storage, organic liquid storage (industrial effluents), fish grade, underground applications (transparent for tunnels, without ultraviolet [UV] stabilizers), cold temperature, reinforced materials, and exposed applications (UV-protected). GFR: That’s quite a bit, but it underscores how complex the construction of a single membrane can be, and why it is important for engineers to look into the deeper aspects of material selection.  How do these formulations change the vital characteristics of a PVC geomembrane so that we can achieve what we need to with our designs? Andre Rollin: In the past, inappropriate PVC formulations may have resulted in premature failures, discouraging the use of PVC geomembranes.  With the understanding of the interaction between ingredients, a designed formulation can be specified for an application to offer more-than-satisfactory long-term service life. Let’s take the material apart and understand it by looking at its ingredients.  First, the molecular weight (MW) of the PVC resin.  The resin’s molecular weight affects the maximum tensile strength, the tensile modulus at 100% elongation, and the puncture resistance.  For example, a 10% increase in these properties was reported by Diebel (2002) when the MW of the resin was increased from a 69K resin to an 81K resin.  The tear did not change significantly and the elongation dropped by approximately 10%.  This shows that there is a balance between strength and flexibility.  In actual use, the lower MW polymer may move more easily if the substrate settles.  The higher MW resin is a larger polymer resulting in greater entanglement, restricting movement. Then we have plasticizers.  This is the most important additive, the one that truly establishes the geomembrane’s properties and chemical resistance.  Two families of products are used: one, monomers such as the phthalates incorporated with geomembranes that will be in contact with drinkable water; and, two, polymers such as vinyl acetate for geomembranes in contact with organic liquids.  Plasticizers used in PVC are either polymers or monomers.  The monomers are different types of esters, while the polymers (often referred to as polymerics) are usually polyesters, nitrile rubbers, or ketone ethylene ester polymers. The majority of plasticizers used in flexible PVC are monomeric phthalates.  Linear phthalates are recognized as being the more stable plasticizers (less migration toward outside surfaces) because of strong bonds between the linear chains and the PVC molecules.  These high leach-resistant plasticizers are used presently for the production of all geomembranes that will be in contact with water. Monomeric trimellitate plasticizers are often used where high-temperature resistance is required.  For conditions under 50˚ C (122˚ F) monomeric phthalates with a chain length greater than 7 are adequate.  Monomeric phthalates with chains less than 9 and adipates have poor high-temperature resistance. Polyester polymeric plasticizers are used when unique properties are required such as in the containment of oils.  Resistance to animal fat, mineral oil, and corn oil all have been found to degrade adipates plasticizers, indicating that they should be avoided in the containment of oils.  Branched phthalates have performed slightly better than linear phthalates, while polyester polymeric plasticizers have performed the best for oils.  Formulations that incorporated the polyester polymeric plasticizers have been found to perform adequately in contact with hexane (a solvent that is known to aggressively extract monomeric plasticizers), gasoline, kerosene, ASTM fuel C, and ethanol.  Alloys of PVC, which contain nitrile rubbers, or ketone ethylene ester polymers, have also been found to provide superior resistance to oils and grease and many other hydrocarbons.  In environments where primary containment of numerous types of hydrocarbons are required, these PVC alloys would likely function well. Also, polyester polymeric plasticizers have performed well in other aggressive environments.  In concentrated caustic environments (20% sodium hydroxide solution), formulations containing the trimellitate or the polyester polymeric plasticizers had no change, while the adipates performed poorer than the monomeric phthalates. Now we come to stabilizers.  Mixed metal stabilizers are required in PVC formulations to allow the material to be processed into a film.  A 2002 study found no significant difference in physical properties between a barium cadmium stabilizer and a barium zinc stabilizer.  Both metal stabilizers are known to work synergistically with a co-stabilizer, epoxidized soybean oil (ESO).  ESO is required for optimum stability and the amount of ESO does not significantly affect the physical properties. Then we have fillers.  Calcium carbonate is often used as a filler in plastics.  Depending on the amount used in a blend, calcium carbonate can increase the modulus, increase the hardness, and at very high loadings decrease the cost of the formulation.  It was found that at levels less than 7% by weight the physical properties were not significantly affected and that, at levels over 20%, the physical properties were compromised and the chemical resistance severely compromised. Stanford et al. (1979) showed that high filler loadings resulted in excessive weight gain and, thus, poor chemical resistance.  A PVC formulation incorporating high calcium carbonate amount is by far the most significant negative factor in acidic leachate environments.  When exposed to acidic leachates, and with 37% HCl, formulations with less than 7% calcium carbonate, incorporating a branched or linear phthalate, had less than 5% weight change and – more importantly – were still very flexible. Now let’s examine UV absorbers and inhibitors.  Clear PVC has poor UV-light resistance and is not recommended for extended outdoor applications without additional components that can prolong the outdoor UV exposure.  These additives are UV inhibitors and absorbers or pigments.  Once a small amount of pigment is added, the UV resistance improves dramatically.  UV inhibitors and/or UV absorbers offer long-term protection. Next, biocide.  The biological resistance of flexible PVC geomembranes has often been questioned and phthalate plasticizers have been thought to be a food source for microorganisms.  This was not found to be the case.  Normally, flexible PVC incorporates a biocide as an extra precaution when blends include certain types of plasticizers that are more susceptible to attack.  In many cases, biocide is not required since the individual raw materials were shown to be resistant to microorganism metabolism. In a study by Klausmeir and Andrews (1981), all the different ingredients in a flexible geomembrane formulation were subjected to ASTM G21.  This involves inoculating the individual raw materials with an assortment of naturally occurring fungi and then incubating the samples for four weeks in an environment where the fungi are known to thrive.  None of the raw materials were found to be easily metabolized by the fungi.  The monomeric phthalate had no evidence of attack by the fungi, but the adipates and sebacates are susceptible to biological growth; and, thus, should be avoided. Overall, PVC geomembranes should be selected with formulations specific to a project’s conditions.  While a minimum molecular weight of 69K PVC resin is required, there is no advantage to go beyond that in most cases.  Polyester polymeric plasticizers result in superior resistance to hydrocarbons while monomeric adipate plasticizers should be avoided in flexible PVC geomembranes since they have poor long-term aging and chemical-resistance properties.  Monomeric trimellitate plasticizers have performed very well and are a good choice for buried, flexible PVC geomembranes, especially where sustained high temperatures (greater than 50˚ C) are anticipated.  Branched, linear or a blend of monomeric phthalates with a carbon chain average that’s greater than seven will perform well in most flexible PVC geomembrane applications.  Branched phthalates performed better than linear phthalates in extremely acidic and caustic environments. Calcium carbonate filler loadings of greater than 7% should be avoided in low pH (acidic) environments.  Proper pigment type and loading level of UV absorbers and inhibitors are required for exposed applications.  Properly formulated flexible PVC is not prone to microbiological attacks. GFR: What are the most common misconceptions in the selection of a PVC geomembrane?  Why should an engineer select (or not select) this material? Andre Rollin: The first misconception is that there exists only one type of PVC.  This is very wrong.  There are a multitude of formulations that result in an array of PVC geomembranes to fit most applications [as noted in response to the preceding questions]. The second most common misconception is that PVC will not resist hydrocarbons, acids, and bases; but, yes, PVC can resist many hydrocarbons (except strong solvents), acids, and bases for a long period of time if the proper formulation is used. Also, many seem to think that PVC will be punctured easily.  On the contrary, PVC is less easily punctured than a rigid geomembrane because PVC has a high elongation characteristic – flexibility is the most desirable property of a PVC geomembrane, offering no re-alignment of the molecular chains when elongated.  It conforms easily to sites, and in most applications does not require reinforcement. A fourth misconception is that you should compare geomembrane thickness, even between disparate materials, when making a selection.  This is wrong.  Comparing geomembrane thickness can be irrelevant.  Performance is what matters.  For example, comparing the properties of a 60 mil rigid geomembrane to the properties of a 60 mil PVC geomembrane is like comparing nonwoven to woven geotextiles.  At like thicknesses, the results can be dramatically different and confuse the real objective of a design.  Consider that many agencies (such as New York’s Department of Transportation) recognize that though nonwoven geotextiles generally have lower strength characteristics than woven geotextiles, the behavior of nonwovens is acceptable, even desirable in many applications because of higher flexibility (elongation).  In many geomembrane designs, a lower thickness PVC geomembrane can offer functional performance similar to thicker, rigid geomembranes. The fifth misconception with PVC geomembranes is that a chemically bonded seam is less resistant than a fusion seam.  This is not the case if proper bonding procedures are followed.  I and many others in the field have observed very strong, tensile-resistant, chemically bonded seams even after many years of their service life. A sixth misconception is that the fragility temperature is too high.  In most applications, the PVC geomembrane will be covered, and a liner temperature lower than 30˚ C (86˚ F) will not be attained.  Canadian and American users are well aware that PVC membranes used as exterior pool liners can withstand very cold temperatures for many winters (more than 10 years) without cracking or suffering structural damages. A seventh misconception is that a seam cannot be checked properly.  Yes, seams can be checked properly, which is to say they allow both non-destructive and destructive testing options.  For non-destructive measures, dual-fusion seams can be checked using the channel air pressure test similar to the one used for other types of geomembranes.  And chemical seams must be checked using air lance and/or electrical leak detection techniques.  Destructive testing can be performed on both types of seams to measure the tensile and peel resistances. Finally, there is a misconception that you cannot use PVC for exposed applications.  Well, yes and no – the general usage product’s blend (i.e., without UV inhibitors or absorbers) cannot resist long exposures; but, UV-resistant formulations will resist breakdown and perform very well for many years. GFR: What recommendations would you make to avoid these errors? Andre Rollin: First, increase the mentorship in consulting firms and governmental agencies.  In my experience, senior engineers accept project management responsibilities or move to other firms; thus, leaving junior engineers to select liners for an application without the senior engineer having transmitted their geosynthetic knowledge or the importance of analysis and proper geomembrane selection for construction.  As a result, the geomembrane selection is too often associated with cut-and-pasting from past experience (which may be little).  This ignores the need to take into account the availability of many other types of products – not just PVC geomembranes – that could offer the desired characteristics for safe and functional performance.  In short, more education is needed.  Engineers must share knowledge. Also, on the technical side, research and development professionals must offer mentoring to the geosynthetic family members, and share educational efforts with them.  For example, the PVC geomembrane industry and the various geosynthetic associations and societies.  In regards to PVC geomembranes, these groups must invest time and effort to make available technical references and papers on the necessity to formulate and select the appropriate PVC geomembranes for different types of applications.  Furthermore, they must make available specifications for these applications, support more seminars and courses, and never avoid giving engineers technical, accurate information on the performance of the geomembrane.  That is how we can avoid misconceptions. GFR: We would be remiss if we did not note your 2002 book on the subject of geomembrane formulations and uses.  However, a copy has appeared only in French.  Is an English language version in the works? Andre Rollin: The book – Geomembranes: a guide de Choix – was co-authored with Pierson and Lambert and published in French by Presse Internationale, Ecole Polytechnique.  Since then it has been updated, and it is now in the process of being translated into English with the collaboration of Barry Christopher, a fourth author.  The English title, Geomembranes: a guide to material selection, should be available by the Geo-Frontiers 2005 congress [January in Austin, Texas – see page 13]. André Rollin works for Solmers International, www.solmers.com This article was published in the October/November 2004 issue of Geotechnical Fabrics Report.