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Household Hazardous Waste in the Sanitary Landfill Riley N. Kinman Department of Civil and Environmental Engineering University of Cincinnati and David L. Nutini RNK Environmental, Inc. Reprinted from Chemical Times and Trends Magazine, 1988 Household hazardous waste (HHW) disposal is a growing nationwide concern. HHW is perceived by some people to have a detrimental effect on the sanitary landfill environment and to require special collection programs to isolate it from the general waste stream. This paper presents the results of a literature review, as well as ongoing research, to determine what volume of HHW might be reaching the sanitary landfill and their impacts. The exact impacts of these waste materials on the sanitary landfill are not known. However, data from solid waste research, codisposal research, and leachate and landfill gas characterizations are presented to help extrapolate what those impacts might be. Finally, benefits deed from collection programs versus placina HHW sanitary landfills are discussed, versus issues such as costs, liability, health and safety, and other related issues. Waste Characterizations Of the early literature searched, one hazardous household product waste characterization was a study performed by the Los Angeles County Sanitation Districts on two landfills: Puente Hills and Mission Canyon- Out of the 185 tons of waste sorted at Puente Hills landfill, only 107 gallons of liquid HHW were detected. Household loads contained 0.0045% and mixed and commercial loads contained 0.28% of potentially unacceptable material. Of 2,056 containers found at the Mission Canyon landfill that had contained materials that could be classified as hazardous, 1,889 were empty (92%). Detailed records on the containers (empty or with residue) were classified into six categories: 40%  Household and cleaning products 30%  Automotive products 16%  Personal products 8%    Paint and related products 3%    Insecticides, pesticides, Herbicides 4%    Other products considered hazardous Containers with a residue were estimated for the percentage of material remaining. For example, in one truckload, 99 hazardous material containers were found. All of these were empty except five containers. One was a 2.35-oz bottle of butane fuel about 30% full. Four other bottles found to have 10% of their original contents included: a 5-oz bottle of shaving lotion, a 5-oz can of insect killer, a 17-oz (aerosol) can of disinfectant, and an aerosol enamel paint can. Of a total of 155 tons of waste sorted at the Mission Canyon landfill, 48.8 gallons of material were found that could be classified as hazardous. Overall. 0.13% of the total refuse mass could be classified as HHW. The conclusions drawn from this study were that: Quantities of potentially hazardous waste disposed of in municipal waste are extremely small. The vast majority of materials inspected and detected were common products which would only be considered hazardous if received in large bulk loads The small -quantity of this type of material is effectively absorbed by the solid waste Consumers do not appreciable quantities of materials that could be considered hazardous. A more recent waste characterization study was performed in King County, Wash., in which 33.7 tons of waste were examined. This waste total comprised residential, commercial, industrial, and self haul samples. Data presented in this paper showed that the residential type waste had a nonregulated hazardous waste component of 0.1% of the total municipal solid waste landfilled. This was based on estimated residuals from the waste and did not include the containers in which they were packaged. An EPA study by Fungaroli and Steiner reported compositions of the refuse they sorted from a 11 city, in southeast Pennsylvania to contain 0.8% paints and oils. This was the only potentially HHW they reported. This is somewhat in line with the Los Angeles study. Although the percentage is higher solely for paints and oils. it is not reported whether this was totally residential, commercial, or mixed. As in most studies of this type, it is probably a mixture of commercial and residential waste. On a smaller scale, Kinman has hand-sorted 532 pounds of municipal refuse from low to medium income homes in the Cincinnati, Ohio, area specifically looking for HHW. Removing the residual hazardous household products from their containers and weighing those residuals yielded a total weight of 0.52 pounds of material. Although based on small sample size, this amounted to 0. 1% of the total refuse mass, which is very similar to the previous studies There were many other waste characterizations found in the literature review. Most of these were characterizations of solid municipal wastes from various solid waste/codisposal projects. A total of 40 waste characterizations representing areas of the southern, midwestern, western, and eastern United States and western Canada were found. Generally, the municipal wastes actually ,g to a sanitary landfill are classified into 11 categories. Note that none of the general categories specifically includes HHW. A composite of these characterizations is given in Table I. From the 40 characterizations, the mean and ranges are reported for each waste category. The reported percentages are based on a combination of wet and dry weights of these wastes. Note in Table I that the greatest average percentage of municipal solid waste is paper, which can effectively absorb small quantities of HHW. As seen in this table, this would generally be the case for any landfill because of the large quantity of paper waste characterized in a landfill. Proponents for preventing HHW from being disposed of in sanitary landfills base their waste characterization figures on collection days and consumption survey. Table II is a composite from waste collection programs reported around the United States indicating that fairly large quantities have been collected. However, what is typically found in the day-to-day garbage can inspection or an inspection of waste compactors is not these large volumes of HHW. Consumers typically don't throw wastes of these types away in bulk. What is thrown away can be handled at the landfill if it is properly maintained and operated. Remember that these collection day figures are generally based on a one-day collection. It does not indicate the time period this waste was accumulated by the participant before the one-day collection program occurred. These collection day data do not contradict the relatively low figures found in the other waste characterizations.  TABLE 1     Mean and Ranges of Waste Categories Characterized in 40 Waste Characterization Studies Across the United States 37 Category Mean % Range % Paper 46.7 36.5-54.7 Garden 9.5 0.4-25.0 Metals 8.5 4,0-14.7 Glass/ceramics 8.4 6.0-13.7 Food 7.8 0.9-18.2 Plastic, rubber, leather 5.3 2.0-9.0 Fines 4.2 3.0-6.1 Textiles 3.3 0.7-5.0 Wood 2.6 0.5-7.0 Rock, ash, dirt 2.5 0.5-10.0 Dirt 1.5 0.5-2.9 Landfill Leachate and Gas Once waste characterizations have determined the amount of HHW entering the sanitary landfill, the true impacts should be determined by studying the effects of these wastes on the leachate and the gas from the landfill. Unfortunately, no studies have looked specifically at HHW impacts on sanitary landfill leachate and gas. However, the studies referenced below were performed with municipal refuse and codisposed refuse (municipal plus industrial sludges). Some of the industrial sludges would be similar to some HHWs, only in larger quantities. For example, some sludges used in these studies include solvent-based paint sludge, battery production waste, and chlorine production brine sludge. The studies examined the leachate from the site; i.e., contaminated water produced as rain or other water infiltrates the refuse in a landfill site. The character of the leachate depends on the types of wastes received into the landfill, the material available for solution, cover material, the age of the landfill, biological activity, chemical activity, and the quantity of the infiltration water. Pohland and co-workers point out that the leachate quality and quantity are site-specific. However different in quality and quantity, several research projects on solid municipal waste indicate that leachate toxicity decreased with time. In two projects in which leachates have been monitored for up to 10 years, the leachate concentrations have peaked within the first year of leachate production (or after the landfill reached field capacity) and tapered off over the remainder of the studies. Table III shows data for leachates in a young landfill (less than one year old), in a medium landfill (five years old) and in an older landfill (ten years old). The young and medium landfill data are taken from Cameron and Koch, whereas the 10 year sample is taken from Kinman et al. The pH of young landfills is generally more acidic, as seen in Table M. The other parameters listed tend to decrease with the age of the landfill, thus decreasing the toxicity of the leachate. This indicates that biological activity is taking place and that the wastes are being detoxified and treated within the lando. The leachate becomes less strong as time and nature do their job. It was noted that Cameron and Koch also measured natural leachates directly from landfills and found them to be less toxic than the lysimeter "synthetic- leachates." Table IV shows the data for their measurements of the natural leachate. This shows that nature does do her job, reducing toxicity while degrading materials.  TABLE II     Examples of Household and Small Small Business Hazardous Waste Disposal Programs Location Waste Collected No. of Participants Anchorage, Alaska(I982) 1,000 lbs + 35 barrels waste oil 48 households,41 businesses Palo Alto, Calif.(1983-1984) Fall: 30 55-gal drums 150 households     Spring: 55 55-gal drums Redlands, Calif. (1984) 175 gal liquid 30 households     75 lbs solid Sacramento, Calif. (1982-1984) 1982: 54 drums, 2,400 lbs oil or recycling 1982: 250 households     1984: 900 households     1984: 165 drums San Diego, Calif. (1984) 13,626 lbs in 5,057 containers 202 pickups, 88 people wentto collection site       Woodland, Calif. (1984-l985) 33 55-gal drums + 100 gal motor oil 106 households Florida(1984) 250 lbs 50 schools,86 gov't agencies,     2,513 households,     277 businesses Barristable, Mass. (1983) 8,000 gals in bulk + 144 gals of waste 500+ households     oil Lexington. Mass. (1982-1983) 86 55 gal drums 316 households Seattle, Wash. 6 gals, 90 lbs pesticides, 3 qts solvents, 65 households     40 gals oil Madison, Wis. 2,872 lbs 325 households San Bernardino, Calif. 60 drums ? I Orange County, Calif. 270 drums 600 Midland, Mich. 3,000 lbs, mostly paint. 10% pesticides 89 Ann Arbor, Mich. 110 gals paint, 35 gals solvent, 3 drums 83     toxic chemicals, 100 lbs lye Lexington, Mass. (1982) 7 55-gal drums paint, 4 drums pesticides 93 Andover, Mass. (1983) 165 gals paint, 55 gals oil, 55 gals 43     waste, poisonous liquid, 30 gals pesticides Bedford, Mass. 7 55-gal drums paint, 1 0 drums pesticides, 67     fertilizers, asbestos, misc. Greater Fan River area, Mass. 3 55-gal drums paint, 1 drum flammable 30 (6 towns) (1983) liquid, 1 drum pesticides, 1 drum acid   Braintree, Mass. (1983) 6 55-gal paint, 7 drums oil, 2 drums 65     flammable liquid, 1 drum acid. 3 30-gal     drums pesticides, 10 5-gals flammable solvents TABLE III       Chemical Composition of Landfill Leachate with Time 10, 14           Parametera 1 year 5 years 10 years pH 4.8-5.2 5.0-6.6 5.6-6.1 Chemical oxygen demand 19,700-45,300 137-34,900 293-10,600 Total organic carbon 7,300-16,350 83-9,150 108-3,080 Total solids 10,000-33,000 718-18,400 1,920-5,530 Total volatile solids 5,350-20,330 124-10,300 770-3,330 Alkalinity 4,100-7,700 184-7,600 1,240-2,900 Chloride 620-1,880 5.3-730 115-193 Cadmium 0.005-0.89 <0.001-0.162 <0.05-0.009 Chromium 0.09-16.8 0.003-0.410 <0.025 Copper 0.03-0.12 0.009-0.09 <0.025 Iron 308-1,136 195-1,820 98.7-855 Lead 0.077-3.15 0.003-0.082 <0.05-0.08 Nickel 0.15-0.79 <0.005-0.342 <0.040-0.127 Zinc 46-298 0.18-75 <0.025-0.167 a All units are in milligrams per liter except pH.   Although leachate toxicity is reduced with time for some parameters, it may still be considered toxic. For example, another study compared the chemical characteristics of leachate from an operating section and from a 20-year-old abandoned section of a landfill in southeastern Pennsylvania. The authors noted (Table V) significant reductions in biochemical oxygen demand and chemical oxygen demand, whereas other parameters were reduced but less significantly. They concluded that the abandoned section, although less toxic, was still considered a source of contamination. Small quantities of HHW in sanitary landfills do not keep the microorganisms from doing their job of biodegradation. HHW have little effect on leachate or gas quality. Although leachate is toxic, it is not toxic because of HHW alone. All residential wastes have the "ingredients" to cause leachate toxicity, primarily from the breakdown of organic wastes placed in the sanitary landfill, including the "nonhazardous" materials such as paper, food, fecal matter, leaves, leather, metal, etc. Therefore, the threat would exist even if the "hazardous" household wastes were eliminated from the refuse. In the case where it may still be a potential threat to water supplies, the leachate must be collected and treated. Several reports indicate that leachate can be treated effectively through recycling, physical treatment, combined physical/chemical treatment, conventional activated sludge plants, separate anaerobic and aerobic biological processes, public-owned treatment works (POTWS) or combinations of these. TABLE IV   Natural Leachate Analysis b   Natural Parameter leachate pH 6.3-7.8 Chemical oxygen demand 720-4,720 Total organic carbon 810-1,600 Total solids 3,190-6,490 Total volatile solids 1,092-2,930 Alkalinity 1,350-3,510 Chloride 125-2,400 Cadmium 0.001-0.004 Chromium 0.025-0.085 Copper 0.01-0.05 Iron 1.6-30.3 Lead 0.023-0.065 Nickel 0.002-0.069 Zinc 0.43-1.32 b All units are in milligrams per liter except pH.   TABLE V     Leachate Comparison Between an Operating Section and a 20-year-old Abandoned of a Landfill in Pennsylvania 28 Parametersa Operating Abandoned Specific Conductance 3,000 2.5 Biochemical oxygen demand 1,800 15 Chemical oxygen demand 3,850 246 Ammonia-Nitrogen 160 100 Hardness 900 290 Iron (total) 40.4 2.2 Sulfates 225 100 a All units are milligrams per liter except specific conductance (microohms). Certain studies have also examined substances that result from the decomposition of modern municipal refuse measured in landfill gas. Anaerobic conditions lead to the carbon containing compound conversion to methane (CH 4 ) and carbon dioxide (CO2), the two principal gases in landfill gas. In addition to these two major components. there are a large number of trace compounds in the gas. One of the experimental goals is to be able to model the decomposition process in sanitary landfill. Table VI contains the trace volatiles in landfill gas. Several compounds were spiked into the experimental landfills so that spiked cells and unspiked cells could be compared. Note that all of the samples from the test cells contained the three compounds used in the spike: benzene, ethylbenzene, and toluene. Concentrations of benzene were about one-fourth of that in the spiked cell. Toluene concentrations exceeded one of the spiked cell concentrations in some of the samples. Ethylbenzene also exceeded the spike cell levels in some of the samples. This indicates that there are materials in the refuse that decompose to yield higher concentrations of the three compounds than when the refuse was specifically spiked to yield higher measurable concentrations of these compounds. Thus, they are there, even if one tries to eliminate them. This is clear from Table VI, which has the compounds (benzene, toluene, and ethylbenzene) grouped according to relative concentrations found in landfill gas. All three compounds are very common solvents used in the manufacture of ingredients for some household products. Benzene is used for organic compound synthesis and, therefore, may be contained in some paints and inks. Ethylbenzene and toluene are used in paint manufacture and many coating materials. These compounds were found in all experimental landfill samples. Highest concentrations were in decreasing order: toluene, 128 mg/m 3 ; ethylbenzene, 105 mg/m 3 -, and benzene, 12.2 mg/m 3 , respectively. In summary, leachate toxicity and gas production in a sanitary landfill. due specifically to HHW, are not found anywhere in the technical literature. However, based upon studies of codisposed municipal and industrial waste, it appears that landfill leachate and gas will have toxic components, regardless of whether the landfill contains HHW. Fortunately, in most cases, if a sanitary landfill is properly engineered, is on a suitable site, and is maintained and operated properly, leachate should not present a threat to groundwater or surface water supplies. The suggestion here is that the landfill acts biologically and chemically on the waste materials to make them less toxic. Nature, in time, will degrade the waste to a considerable extent. At the same time. the collection and treatment of the leachate is recommended to render a safe effluent.  TABLE VI               Trace Volatile Organic Compound Concentrations at 25ºC                 Lysimeter(sample date)       21b,c 21c 22 22 23b 33 35 Compound. (5/22/55) (6/20/55) (6/20/55) (7/01/85) (5/22/85) (6/20/85) (6/20/85) Pentane NDd 6.42 0.2 1.33 Pe ND 2.13 Tetrahydrofuran ND ND 0.406 ND ND 0.653 0.408 Freon ND 67.7 0.203 13.3 ND 1.08 ND Benzene 12.2 12.1 1.02 1.05 0.4 1.3 0.821 Dichloromethane 0.05 27.7 0.71 54.1 0.017 2.71 0.321 Hexane P 101 1.02 26.4 P 1.08 2 Toluene 11.2 128 20.3 21.1 3.62 33.5 48 1.1-Dichloroethylene 0.04 ND ND ND 0.032 ND ND 1.2-Dichloroethylene 0.99 0.54 1.31 1.85 1.27 ND 0.651 1.1-Dichloroethylene ND ND ND ND ND ND ND o,m,p-Xylenes 13.3 175 112 118 12.2 249 120 Ethylbenzene 8.78 105 24.4 25.1 4.58 68.3 97.1 Chlorobenzene ND ND ND ND ND ND ND Isooctane ND ND ND ND ND ND ND benzene ND ND ND ND ND ND ND Propylbenzene p 33.7 8.11 11.8 ND ND 3 Carbon disulfide NO 67.7 0.965 128 0.018 8.02 1 0.8 Naphthalene ND ND ND ND ND ND ND Nonane ND ND ND ND ND ND ND Trichloroethylene 0.149 0.506 0.193 0.185 0.389 NO 0.13 1.1.2-Trichloroethylane ND ND ND ND ND ND ND Tetrachloroethylene 0.292 ND ND 0.146 0.155 ND ND a All values are in milligrams per cubic meter.           b High sample volume, results tend to be low.           c Waste spiked with benzene, toluene, and ethylbenzene.         d ND, not detected: <5 mg in sample trap.           e P, identified, but not quantified.           Codisposal Projects Further support for this position is found in additional studies of how some industrial wastes have behaved when codisposed with municipal solid wastes. Some of these industrial wastes studied have similarities to some of the HHW (for example, paint sludge). By comparing these, it may give the reader some idea of the capability of a landfill to accept and degrade these materials. One study performed by Kinman et al found few significant differences between leachate parameters in landfill lysimeters with codisposed hazardous and nonhazardous industrial wastes and municipal waste and lysimeters with municipal waste only. Table VII presents data at the closure of this landfill project (ten years). One cell contained electroplating waste (heavy metals) mixed with municipal refuse and the other cell contained petroleum waste mixed with municipal refuse. The parameters of these two hazardous waste cells are averaged for the codisposal column. The other column represents four control cells with municipal refuse only. These parameters are averaged and presented in the municipal refuse column. Note that in ten years the leachate parameters shown here are not significantly different.  TABLE VII     Comparison of 10-year old Leachae Samples From Codisposed Cells Versus Municipal Refuse Only Cells 14             Parametersa Municipal Refuse Only   Codisposed Refuse pH 5.93 6.5 Conductivity 2,305 2,160 Total solids 2,950 3,090 Total volatile solids 1,481 1,330 Total organic carbon 852 214 Chemical demand 2.903 602 Alkalinity 1.793 2.395 Total Kjeldahl nitrogen 135 79 Phosphate-phosphorus 5 2 Chloride 161 118 Chromium 0.025 0.029 Cadmium 0.006 0.009 Copper 0.025 0.025 Iron 306.4 299 Nickel 0.08 0.19 Lead 0.06 0.11 Zinc 0.08 0.17 a All units are in milligrams per liter except pH and conductivity. Other studies have reported similar results Pohland and Gould reported on comparisons of codisposed wastes with municipal wastes with specific emphasis on the fate of heavy metals. Their data indicate significant attenuation and reduction in leachate heavy metal concentrations. They report that the waste was disposed of in a controlled manner and with the benefit of leachate containment, collection, and recycling. The key here is control, operation, and maintenance. Three different studies on codisposal of various industrial sludges with municipal refuse have also shown that the two waste groups behaved similarly. The industrial waste sludges codisposed in these projects included oil reclaiming clay, petroleum refinery incinerator ash. paint manufacturing sludge, solvent refinery sludge, tannery waste, electroplating sludge, metal finishing sludge, automobile assembly plant sludges (paint and putty), chlorine production brine sludge, and calcium fluoride/sewage sludge. The first study concluded that the concentrations of the metals found at significant levels in the industrial waste leachates tended to decrease over the sampling period. Another conclusion in the same port showed that the results of the limited organic analyses for toluene, xylene, and cresol in the municipal waste leachates and the industrial waste leachates indicated that the concentrations of the organics in the leachates collected before and after contact with the industrial wastes were very similar. The second study concluded that, although elevated levels of a limited number of constituents which could be related to the presence of the treated wastes were detected in the first meter of soil under the sludge/soil interface, in no case were these levels higher than the typical range for these elements in eastern U.S. soils. Therefore, attenuation of pollutants from the leaching medium by the underlying solid does not seem to be a major factor in maintaining high quality groundwater under the studied sites. The third study produced the following results: 1) no release of metal contaminants from the electroplating sludge; 2) stabilized chlorine production brine sludge reduces release of toxic metals and chlorides, whereas untreated chlorine production brine sludge released significant quantities of aluminum, cadmium, copper, chlorine, mercury, sodium, and other dissolved solids; 3) calcium fluoride/sewage sludge improved leachate quality. What all three of these reports tell is that many of the industrial wastes experimented with in these codisposal projects behave similarly to landfills with municipal refuse only. The State of Minnesota runs a codisposal program. Officials believe that some nonhazardous industrial wastes may be codisposed with the municipal refuse. They require specific screening procedures and tests to be performed before a waste can be accepted. Because the program is growing and has become so large, they are hoping to develop lists of industrial wastes that would be acceptable for codisposal. Some of the 102 waste types requested for codisposal have been grouped into 12 categories: paint agriculture organic resins sludge wood and papermill food foundry health care ash ink sludge petroleum spills other Of the 102 requests, 53 were approved for codisposal. (They do not report specifically which wastes were accepted and how much). Contrary to previous codisposal projects discussed, a codisposal study reported by Jones et al concluded that, in all cases, the codisposal of treated or untreated industrial wastes with municipal solid waste had significant effects on the character of the leachates produced. It must be noted that this lysimeter experiment was in the young to medium stage (four years) when these results were reported. As seen previously, in all lysimeter studies examined in this report. the early leachate parameters go to a peak concentration and then decrease through time of landfill operation. It is believed that with time similar results might be obtained. In summarizing this section, most codisposal research work has demonstrated that codisposed refuse did not produce substantially different results compared with municipal waste disposed. The leachates were similar, gases produced were similar, and microorganisms were not significantly affected.  Collection Programs Versus Sanitary Landfill Disposal Proponents for collection programs state that the advantages and goals of separating HHW from the general municipal refuse stream are: 1) it keeps hazardous materials which may cause groundwater problems out of the sanitary landfill; 2) it increases homeowners' awareness of HHW; 3) it educates homeowners about HHW; 4) it reduces exposure and injury to homeowners (health and safety); 5) it reduces dangers to sanitation workers; and 6) it provides for proper disposal. Research indicates, as described earlier, that there are only small quantities of HHW, as compared with the total waste stream by weight. HHW has little effect on the quality of either the leachate or gas coming from sanitary landfills. Furthermore, the hazardous materials do receive some treatment in the sanitary landfill, whereas they receive little or no treatment in a secure chemical landfill. Although there is limited incineration capacity presently available, if these materials were incinerated, they would also receive treatment. Overall, this suggests that collection programs may not be necessary when .the materials are placed in a well-designed and well operated sanitary landfill. In further response to the other collection program goals above, it may be said that the homeowner is more exposed to these products during use or when collecting, storing, handling, and transporting them to a collection center. If some chemicals were removed from the trash, this would reduce sanitation worker injury by 2-3%, according to available statistics from the National Institute for Occupational Safety and Health. More injuries occur from broken glass and other sharp objects in the refuse. Costs of collection programs to date are extremely expensive. The costs average greater than $5,000 per ton of waste for various collection days presently held around the United States. Costs for disposal into a sanitary landfill are dramatically less ($5-17/ ton) with seemingly more benefit in treatment and less risk to the consumer. Collection program costs to date have been subsidized by government on the local, state, and federal levels; by sponsoring chemical companies and hazardous waste firms; and by donations from a variety of organizations (private and public) in the form of money and/or services. Funding on a continuous basis is questionable at the very best. Liability is another potential issue concerning collection programs. Technically, there is liability of collecting HHW and disposing of these materials in a Subtitle C Facility under Resource Conservation and Recovery Act laws. The issue to date has somehow circumvented RCRA law. Will it if collection programs continue? Who would be liable for these wastes if there is a problem at the secure chemical landfill in the future under the Comprehensive Environmental Response, Compensation, and Liability Act (Superfund)?  Conclusions HHW are present in extremely low concentrations in municipal refuse, around 0.1% by weight. Small quantities of HHW in sanitary landfills do not keep the microorganisms from doing their job of biodegradation. HHW have little effect on leachate or gas quality. The sanitary landfill can absorb large quantities of hazardous materials with little change in either leachate or gas quality. Collection days for HHW may not be necessary when the refuse is disposed in properly designed and operated sanitary landfills.   References in Hard Copy Only.     For more information call   800-OK-LINER   today!

This paper was presented at Geosynthetics '91 in Atlanta, GA. -  February 1991 By Fred P. Rohe Environmental Protection, Inc., U. S. A. ABSTRACT Environmental Protection, Inc. participated in the design and development of a prototype system to install a 30 mil PVC liner and 3 inches of concrete underwater in the Coachella Canal located in Southern California. This project, under the direction of the U.S. Bureau of Reclamation, is the first of its kind anywhere in the world. The development of this technology required the cooperation of many different suppliers, including EPI, under the coordination of the prime contractor, Kiewit Pacific Company. The development and implementation of a unique solution to liner placement underwater is the beginning of a significant effort to conserve water resources and to reduce canal maintenance and construction costs. INTRODUCTION In the spring of 1988, EPI was one of several suppliers to bid on providing a 30 mil PVC geomembrane liner for the U.S. Bureau of Reclamation. The project, titled "Coachella Canal In place Lining Prototype, All American Canal Relocation, California," is the first of its kind anywhere. After completion of the bidding process, the Bureau of Reclamation determined that Kiewit Pacific Company, of Santa Fe Springs, California, should be awarded the contract. In the Fall of 1988, EPI was contacted by Mr. Bill Giroux, Design Engineer for Kiewit, regarding the supplying of the PVC geomembrane liner. The initial meeting in September of 1988 involved preliminary research regarding the feasibility of the preliminary design work done by Mr. Giroux. Over the next several months, much research and development was done in order to solve the problems of handling the PVC liner during the in place lining process. Since the project was being done on a fast track schedule, actual fabrication of much of the equipment was being undertaken while other development was being done regarding the handing of the liner material. Fabrication of the geomembrane was undertaken during February and March of 1989 with shipment to California and actual placement of liner in the canal beginning in May of 1989. MATERIAL Polyvinyl Chloride (PVC) was selected as the membrane lining material for the underwater application at the Coachella Canal. The Bureau's selection of PVC was based on many factors, including: The availability of large panels. PVC was fabricated into panels 58.6' x 200'. The PVC geomembrane is highly flexible and retains its properties over a wide temperature range. This permits the liner to conform to the subgrade better than other available geomembrane materials. The PVC geomembrane is easily field spliced with solvent welding. The PVC also has very good puncture, abrasive, and tear resistance properties, which are important in minimizing damage during installation. PVC has a proven history of use in canal lining for more than 30 years by the Bureau of Reclamation. Since the lining of the canal was to be done in two passes requiring a longitudinal seam in the PVC liner down the center of the canal, it was necessary to use a geomembrane that could be sealed underwater. Since an unbonded longitudinal seam would not provide the necessary seepage control, laboratory studies concluded that a vinyl swimming pool adhesive used to repair pool liners would be a suitable adhesive for this seam. Laboratory test results of seam strengths for the underwater seam proved comparable with normally fabricated field seams, even though these were constructed underwater. There was also a concern that the freshly placed concrete would have a tendency to slough down the slope of the canal sidewalls. Initial design requirements called for the application of a 3.4 ounce per square yard non-woven geotextile fabric on the side slopes on top of the PVC. The final solution involved the contractor gluing this geotextile to the PVC liner at their facility in Santa Fe Springs. The liner panels were then refolded and rolled prior to installation at the project site. It is anticipated that a factory laminated product, which will provide both the 30 mil PVC and a non-woven geotextile bonded to one side of the liner, will be available for future projects. This product will save considerable time and manpower in the placement of the two materials at the same time. Currently, a new GeoLam product is being introduced by Occidental Chemical Corporation, which has evolved from the research and development on this canal project. Since the PVC material had never been used in this type of application, there was no data available as to how the membrane would behave during the underwater installation procedure. The preliminary design concept, proposed by Bill Giroux, involved holding the PVC in a manner much like a garage door track supports the sides of an overhead garage door. The track design called for the inclusion of a hem in the liner material along both sides of the panel. This hem was to be filled with a rope to provide body and hold the liner securely in the guide track. The development involved the use of a PVC jacketed nylon rope. In order to develop data as to the behavior of the liner in this application, EPI fabricated for Kiewit Pacific, several full size samples of the PVC liner. In addition, EPI fabricated a small section of liner 60 feet wide, which was furnished to Mr. Giroux at his office in Omaha, Nebraska. Mr. Giroux proceed to do full scale testing with this liner at the YMCA pool in Omaha. From the data generated in these tests, it was determined that support of the liner on the two outside edges would not be sufficient to control the final placement of the liner. The design was then modified to have two center guide tracks, one at the toe of the slope, and one at the centerline of the canal. The outside guides would be at the top of the slope, and at the outside edge of the three foot overlap in the canal bottom. The center guides posed a problem in that a hem type seam would be subjected to forces which would exceed the normal peel strength of the seams. The challenge for EPI was to develop a fabrication process which was both effective and cost competitive to provide the liner panels for this project. EPI developed a system whereby the ropes could be anchored into the PVC liner, and seams made with sufficient strength to resist the forces that would be placed on the liner during the underwater placement of the geomembrane. The final fabrication techniques are a proprietary process of Environmental Protection, Inc. The process was inspected in operation by the U.S. Bureau of Reclamation. All fabricated panels were tested for bonded seam strength and peel adhesion of the factory seams and a sample of each roll of material was supplied to the Bureau of Reclamation for physical property testing. In addition, all material that was supplied for the project by Occidental Chemical Corporation was also tested for compliance with the project specifications. DISCUSSION The prototype project was to line 1.5 miles of the Coachella Canal near Niland, California. The canal at this section was approximately 110 feet wide, and 9 feet deep. The side slopes of the canal were approximately 2.5:1. Since the canal was built 49 years ago in the sandy desert soil, it was necessary to reshape the canal prior to the placement of liner and concrete. A machine to dredge the canal and place a new sub-base of crushed aggregate was also designed and built by Kiewit Pacific. This machine precedes the paving unit and reshapes the sides and bottom of the canal to line and grade. Coachella Canal Paver After shaping is completed, the paving unit proceeds to travel along the canal, placing the PVC/geotextile composite in place directly in front of a slipform paving unit designed and constructed by Gomaco, of Ida Grove, Nebraska. After paving one half of the canal, the machine is turned around, and proceeds to pave the second half of the canal from the opposite direction. Based on design, speed, and availability of concrete, working 24 hours per day, it was estimated that the paving of 1.5 miles in one direction could be accomplished in approximately 3 days. The initial paving operation was started in May of 1989. At that time, the water usage requirements in Southern California were reaching their peak. It was necessary to be able to regulate the flow of water so that the many adjustments to all of the various operating systems of the paving unit could be accomplished in reasonable fashion. Initially, about 1,200 feet of lining was placed during early May. The balance of the paving will be completed after modifications are made to the equipment to accommodate the soft substrate that underlies the canal bottom. SUMMARY The selection of PVC liner for this project has proven to be an excellent choice. The custom fabrication of the PVC liner for handling during placement by this equipment was accomplished with minimal additional cost for the geomembrane liner. In addition, the performance of the liner and geotextile combination for this project has shown itself to be very satisfactory. After completion of the lining of this section of the canal, the Bureau of Reclamation will monitor the performance to determine whether additional section should be lined and completed at a future date. Sections of the All-American Canal, which feeds the Coachella Canal, are being surveyed for potential relining efforts. The need to maintain water quality for environmental reasons prompted an environmental impact study before the project was started. Extensive monitoring of the water quality is occurring during the placement of concrete and liner in the canal. No adverse effects to the environment have occurred or are anticipated. Since the canal supports a fishery with 16 different species, as well as the irrigation water to the Coachella Valley, the environmental priorities are very important. EPI provided on site training for the placement and seaming of the PVC geomembrane. The Bureau of Reclamation also provided onsite inspection and quality assurance for the project. In addition, EPI provided actual random factory welded samples from every PVC panel for physical testing by the Bureau of Reclamation. EPI also provided in house testing of factory seams from every geomembrane panel. The geomembrane material was tested by the Bureau of Reclamation on a random basis prior to shipment to the project site. Occidental Chemical Corporation, the manufacturer of the PVC geomembrane, also coordinated their quality control testing in their lab with the Quality Control testing by the Bureau of Reclamation and EPI. This combination of efforts ensures that the final product installed for this prototype is as required by the Bureau's specifications. It is estimated that by relining this canal, up to 115,000 acre feet annually (enough fresh water for up to 150,000 households) will be conserved. User fees generated from the water saved will offset the cost of the relining of the canal. The 5.2 million dollar contract is being shared by the Bureau of Reclamation (40%) as well as the Metropolitan Water District (54%) and the Imperial Irrigation District (6%), both of which serve the end users of the canal. The estimated cost to line the rest of the Coachella and the All-American Canals is estimated at $170 million. If initial estimates hold true, this figure is about 40% less than the alternative of constructing new sections of canal. CONCLUSIONS The development of a prototype lining system will eventually produce a new method to conserve water resources and to provide a method of remediation for existing canals that have been in service for many years. The development of equipment and process to place a PVC geomembrane underwater, without disturbing or restricting the water supply will be a boon to the eventual long term maintenance of this water supply system. This project is being viewed by engineers and water professionals from around the world. Its eventual evolution into a significant industry is becoming a more substantial possibility each day. REFERENCES 1. Workshop on Inplace Lining Prototype - Coachella Canal, American Water Foundation - May 8, 1989, Palm Springs, California. 2. Rebant, Daniel B., "Underwater Lining of Canal Promises Huge Savings in both Water and Money", Geotechnical Fabrics Report, November, 1989. 3. Solicitation/Specifications, "Coachella Canal Inplace Lining Prototype", Bureau of Reclamation, Lower Colorado Region, P. O. Box 427, Boulder City, NV 4. Morrison, W.R. and Starbuck, J.G., "Performance of Plastic Canal Linings" Report #REC-ERC-84-1, Bureau of Reclamation, Denver, Colorado, 1984. 5. Morris, W.R. and Swihart, J.J., "Bureau of Reclamation Experiences with PVC Seams", The Seaming of Geosynthetics, Geosynthetics Research Institute, Philadelphia, PA, 1989.     For more information call   800-OK-LINER   today!

By Fred P. Rohe and Sam Lewis 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.)   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 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.  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.  Please direct any questions to Fred Rohe or Mark Wolschon at EPI . They will be pleased to answer any questions regarding the curing of chemical fusion welded seams, accelerated testing, and factory fabrication quality control.   For more information call   800-OK-LINER   today!

All MSW leachates are different. Many PVCs have successfully contained MSW leachates for many years. At Lycoming County, PVC that has been exposed to leachate in a leachate storage pond for 13 years is marginally more flexible than the material that was not exposed to leachate. Artieres (paper enclosed) is testing different geomembranes in two different MSW leachates and water. Two PVC geomembranes (with DOP and ethylene copolymer/vinyl acetate plasticizers) and one HDPE geomembrane are being evaluated. After 16 months at room temperature and 3.5 months at 50 degrees, both PVC and HDPE show good resistance. Burst tests show small changes in HDPE, no changes in PVC. Infrared (IR) spectrophotometry shows PVC affected to t depth of 80 m m (loss of plasticizer) and HDPE affected to a depth of 100 m m (loss of antioxidant). The paper by Fayoux et al. Discusses an uncovered 40 mil PVC geomembrane used to contain MSW leachate for 10 years. The liner was, therefore, exposed to UV radiation and/or leachate. The loss of plasticizer was less, (averaging only 0.35% / year) in PVC under the leachate than in PVC expose to UV radiation. The loss of plasticizer was, in fact, essentially the same as it was in plain water. Oil-resistant PVC was subjected to an EPA Method 9090 test in a leachate, generated from a mixed municipal solid waste and industrial waste landfill, that was strongly spiked with liquids normally very aggressive towards PVC. The PVC was shown to be resistant to the leachate. Conclusion: MSW leachates do not automatically leach out plasticizers and degrade PVC geomembranes. Laboratory Ageing of Geomembranes in Municipal Landfill Leachates by O. Artieres, F. Gousse and E. Prigent Summary The chemical stability of geomembranes layed in municipal landfills is, even if not alone, an important choice criterion. Changes of their physical and chemical properties must be assessed in the time with an ageing simulation. Selected liner materials exposed to leachate during 16 months present no damages. INTRODUCTION In many European and international legislations, geomembranes are prescribed to be used in hazardous waste landfills to prevent aquifer pollution. They are also used to watertight the bottom and the top of municipal landfills and collect leachate produced by rainfall through the domestic wastes. The duration before complete stabilization of actual domestic wastes, when not pretreated, is very long, perhaps many centuries after deposition (1). During this period, produced leachates contain a lot of chemical compounds which can react with the liner material point of the landfill security. This paper describes a long-term laboratory study undertaken to evaluate the possible modifications of the geomembranes characteristics during their contact with leachates. METHODOLOGY OF THE LABORATORY-AGEING The aim of this study is to simulate only the chemical compatibility of a selection of geomembranes in leachates. The laboratory-ageing must reproduce the chemical environment of a geomembrane layed at the bottom of the landfill, i.e. chemical, biological or mechanical stresses, temperatures flow,.... The general principle of the experiment is to immerse at 200C and at 50C samples of various geomembranes in two different municipal landfill leachates and in distillated water, then to test these samples periodically to follow the variation of their characteristics. The size of the geomembrane samples is about 30 cm x 30 cm. The samples are hung up in polypropylene tanks of 60 cm x 40 cm area filled with about 35 cm of leachates or water. Each tank holds 17 samples of one type of geomembrane in one kind of fluid. There is about 27 1 of fluid per m2 of geomembrane area. The local environment and stresses must be simulated as far as possible: 1) Flow and dissolved oxygen rate . An immersed pump connected to a pipe distributes the fluid between the samples. This constant flow is necessary to renew the fluid at the samples surface avoiding the saturation of the chemical reactions. The flow is high enough to move the fluid along all the samples surface, but sufficiently low to avoid turbulencies on the fluid surface preventing its re-oxygenation. The anaerobic condition must be preserved to reproduce the real environment, this condition is usually more injurious to the polymers because anaerobic micro-organisms find their energy in eating molecular chains. 2) Temperature. The temperature of 500C is the extreme value reached by the leachate at the bottom of the landfill near the geomembrane. The value of 70 degrees C is also proposed in literature (2) (3). On the other hand, 20 degrees C can be considered as medium-temperature at the bottom of the landfill when the degradation phase of the organic matter is almost finished or when the reaction heart of the landfill is far from the geomembrane. The knowledge of the ageing-kinetics at these two extreme temperatures also allow to extrapolate the kinetic at intermediate or, if necessary, at higher temperatures. 3) Light The tank is covered against the light which can help to the development of not suitable bacteria or fungi, or accelerate the ageing of the samples by photo-degradation. Chemical parametersi n mg/l exept precised Leachate from compacted wastes Leachate from crushed wastes PH 6.93 7 diss. O2 0.5 1.7 Redox potential (mV) -70 -72 COD (mg 02/l) 12700 1480 NH4+ 1200 66 PO43- 0.8 1 cl- 14960 328 acetone 1.45 0.75 butanone 0.053 0.025 methylisobutylcetone 0.018 - hydrocarbon <0.01 - Table 1: Physico-chemical parameters of the two leachates from municipal landfills used in the ageing-study [4]. 4) Chemical media. Leachates: It was decided to use real leachate instead of a synthetic one because of the wide range of compounds they contain. The aim of the study was not a work on the definition of a standard leachate. At the beginning time of these simulation tests, no artificial leachate was yet standardized. To take the variability of leachates into account, the samples are immersed at room temperature (= 20 degrees C) in two leachates of different municipal landfills : the first is sampled at the outlet of the leachate collector of a landfill where the domestic wastes are compacted; as a result they are in anaerobic conditions and they produce a leachate with high concentrated pollution (Table 1). the second one is sampled in the treatment pond of a landfill were the wastes are crushed, but not compacted. They decompose in aerobic conditions and the produced leachate is less polluted as the first one (Table 1). The rate of dissolved oxygen in the two leachates in very low. This value is little higher in the case of the crushed wastes because of the sampling in the treatment pond. But both conditions are anaerobic and it is primordial not to introduce air in the ageing tanks during the tests. Reference medium: All the samples are also immersed at room temperature in distilled water used as reference medium, in the same conditions as those immersed in the leachates. The samples at 50 degrees C are only immersed in the leachate from the compacted wastes landfill to simulate the extreme conditions. All immersion media are usually renewed every 3 or 4 months. The physical-chemical characteristics (pH, conductivity, dissolved 02) are checked every 2 weeks to follow their evolution and to give the renewing-time. Figure 2.) Schematic of stress cracking device after ISO 6252. 1-Beam, 2-Pivot without friction or fulcrum, 3-Anchor, 4-Inox cable, 5-Thermoregulated fluid circulation, 6-ClampS, 7-Sample, 8-Ageing fluid, 9-Masses, 10-clock circuit breaker, 11-Clock 5) Mechanical stress. Chemical and mechanical stresses can combine to affect the polymer's service life. The combined stress on semicrystalline polymeric materials can cause stress cracks [2]. This phenomenon is now well know for polyethylene geomembranes and is one of the disadvantages of this material (5) (6). These failures often occur in the seam areas, due to residual stresses after seaming and also due to the overlapping geometry of the seams [5]. Cracks and strain due to residual stress increase diffusion of chemicals in polymer material leading to chains break. This acceleration of chemical damages due to synergy of stresses was also tested in this research program. A device according to ISO 6252 "Determination of environmental stress cracking Constant tensile force method" was therefore developed. Twelve test specimens of one liner material as described in figure 4 are loaded to a portion of their break stress by means of static load. Then, 4 of them are immersed in crushed wastes leachate, in distillated water and 4 in the air. The leachate and the samples are protected from light (figure 2). The first tests were initially leaded on continuous samples and 20 degrees C. Further tests will concern seamed samples and higher temperatures. Figure 3.) Structure of the bituminous geomembrane 1-Non-stick film, 2-Sanding, 3-Asphalt impregnation, 4-Bidim non-woven fabric, 5-Glass fiber layer, 6-Anti-perforation film   Type Thickness Room Temperature ( 20º C) 50º C geomembrane (MM) comp. waste crus. waste distilled crus. waste.     leachate leachate water leachate Bituminous 3.9 -2 -2 -2 - SBS/Bitumin. 4 -1 -1 -1 -4 PVC/DOP 1.2 -1 -1 -1 -4 PVC/EVA 1.8       -3 HDPE 2 -1 -1 -1 -4strong> co-PP 1.2 -3 -3 -3 -3 EPDM 1 -1 -1 -1 -3 Table 2 : Ageing time and media of the selected geomembranes. (1)-since December 89, (2)-stopped after 5 months, (3)-since December 90, (4)-since November 90 SELECTED GEOMEMBRANES The current constituent material for the geomembranes prescribed at the bottom of hazardous, and even domestic, wastes landfills is High Density Polyethylene (HDPE). This polymer is commonly selected because of his chemical stability. But data about long-term ageing of other types of geomembranes in domestic wastes landfill leachates are so few in literature (except (12)), that it was decided to test a representative range of the present international production. Seven kinds of material constituting the geomembranes were selected (Table 2) : - Bituminous geomembrane- The geomembrane is made up of a polyester non-woven geotextile and a glass voile arming the sheet, both impregnated with oxidized biumen (Figure 3). Bitumen is particularly sensitive to hydrocarbons, ether, xylene, benzene,... Polyester is sensitive to hydrolysis, especially over 50-70 degrees C, but it has a good chemical stability to petrol and solvents (7). - Modified bituminous geomembrane. The structure is the same as the previous one, but the impregnation is made with bitumen modified with a copolymer of styrene-butadiene-styrene (SBS). SBS is a styrenic elastomer which gives a part of its elastic properties to the mixture. SBS is sensitive to oxidation, hydrocarbons and solvents (7). - Plasticized PVC geomembranes, Polyvinylchloride (PVC) polymer has a good stability to chemical compounds (oil, water, oxydizing agents) (7). But it is a rigid material. One must include plasticizers (between 20 and 50 %) to produce soft geomembranes. These platicizers are very sensitive to oxidation (alcohols, hydrocarbons... ) because of their polarity and they migrate out of the material. others additives are then added to protect the plasticizers: anti-oxidizing and blocking agents (7). The kind of plasticizers and additives is therefore very important for the long-term evolution of the geomembrane two PVC geomembranes were tested to evaluate the influence of the plasticizers - PVC plasticized with dioctylphtalate (DOP) - PVC plasticized with a copolymer of ethylene and vinylacetate (EVA). EVA which belong to the polyolefinic family (like PE or PP) is more resistant to oxydation than the phtalates - Polvolefinic geomembranes. Polyolefines comes from polymerisation of ethylene and/or propylene. The resulting polymers have a good resistance to chemical compounds because of the low chain ramifications and the crystalline structure, but they are sensitive to oxidation (especially UV) [7]. They contain very few additives (< 5%): mainly anti-oxidizing agents. Two kinds of polyolefinic geomembranes were tested High Density Polyethylene (HDPE) Copolymer of Ethylene and Propylene (co-PP) - EPDM geomembrane. EPDM is an elastomer terpolymer of ethylene-propylene-diene monomer. Like the polyolefines, EPDM is sensitive to oxidation, but also to aromatic solvents and chlorinated hydrocarbons Some additives are used to protect it against oxidation. TESTS The selected tests intend to quantify and understand the ageing of the geomembranes in the time. These tests are mechanical, hydraulical or analytical. Figure 4.) Sample of ISO type for uniaxial tensile test.   L A B F C D R 50+/-0.5 60±0.5 10±0.5 150 min 20+/-0.5 115+/-3 60 min D-initial distance between clamps, L-Distance between the marks, A-Constant width part. All the sizes in mm- 5 .1 Mechanical tests 5.1.1 Uniaxial tensile test The classic uniaxial tensile test is used to assess the mechanical values of the geomembranes, i.e. tensile strength and strain at break and/or yield points, secant tensile modulus at 10 % strain. All these values are very common and easy to use, even if the test doesn't describe exactly the real behaviour of the geomembrane in place. The sample size shown in figure 4 is of ISO type defined in the ISO/RS27 standard. The thickness of the sample is the thickness of the geomembrane. The strain rate of the machine is 50% per minute. Strain is measured with an optical extensometer following 2 lines previously drawn on the sample. 5.1.2 Biaxial tensile test The principle consists in blowing up the sample of geomembrane facing a circular opening by air pressure while clamps prevent from shortening. The air pressure is raised by steps of 100 kPa per 2 minutes and the geomembrane forms a spherical dome which grows in relation with the pressure up to the bursting failure. The result of the test is a relationship between air pressure and increase of the dome. The bursting test has the following advantages regarding the uniaxial tensile test : it generates a 2D-tension which is very close to field conditions it tests a larger area of material, it displays leaks in the geomembrane under strain (see further) The two mechanical tests complement one another. 5.2 Hydraulical test The ageing processes has also an effect on the tightness Of the geomembrane to leachates. Mass transfer in geomembranes is due to diffusion process. This mass transport is due to 2 driving forces : concentration and pressure gradients between the 2 sides of the sheet [8]. In landfill applications, the leachate level over the geomembrane is low (< 1 M) and the pressure gradient is negligible. The diffusion due to concentration gradient is therefore the main cause of permeation of leachate through the geomembrane. The sorption test is an easy method to quantify the diffusion by concentration gradient. It may be performed with any kind of compounds. Water is chosen as permeant to characterize the tightness of the aged geomembranes, because it is the main compound in the case of municipal landfill. The test consist in following in the time the mass of absorbed water (Mt) in samples of geomembrane which are immersed in water till they reach mass stabilization (M). A mathematical interpretation of diffusion process with the mass increase leads to the diffusivity (diffusion coefficient) in measuring the half-sorption time t1/2 (Mt1/2 =M/2). This model is described in [8]. The relationship between diffusivity D (in m2/s) and the half - sorption time t1/2 (in s) is: D = 0.0492 . Tg2 / t1/2 Tg : Thickness of the geomembrane in m. Analytical test All the above macroscopic tests are benefit to assess the general behaviour of the geomembrane after ageing, to evaluate the possibly loss of characteristics and to compare then with the design values. But these tests doesn't allow the interpretation of the changes which happen at the molecular level. An analytical test is useful to know the kind of degradation and its extent. Many analytical tests are employed to characterize the polymers (see, for instance, (9) and (10). Each of them describes one aspect of the polymer structure. But among these methods, the micro (Fourier Transformation Infra Red) spectrophotometric technique applies to almost all the polymer materials tested, gives the chemical and morphological changes in the polymer matrix and quantifies them. The basis of the method described in (11) consists in sampling with a microtome small slices of geomembranes (thickness between 80 and l00 mm for PVC and HDPE; only 7 mm for EPDM which is very opaque because of its high black carbon content) normal to its surface and in analysing these films by IR light (Figures 6 and 7) . The micro (FTi.r.) spectrophotometric measurement gives distribution profiles of the compounds which could appear during the ageing of the material in the thickness of the liner. Figure 6.) Cutting of a geomembrane slice to make an IR spectrum after CNEP report.   1-Microtome blade, 2-Thickness of 80 or 7 m m, 3-geomembrane, 4-PE plates maintaining the sample, 5-Slice cutting with the microtome blade, The opacity of the bituminous geomembranes is to high to allow micro(FT i.r.) spectrophotometric measurement. The photoacoustics (FT i.r.) spectroscopy is a sustitution method which analyses surfaces of sheets with a high black carbon load. These tests are made at the Centre National d’evaluation de Photoprotection (CNEP) in Aubi6res (France) . FIRST RESULTS These following results describe the changes of characteristics in the geomembranes after an ageing of about 16 months at room temperature and 3.5 months at 50 degrees C. 6.1 Mechanical chances The uniaxial tensile tests shows no sensible changes of the mechanical properties between unexposed and exposed geomembrane samples. The bursting tests agree this point. But they are a little more sensitive comparing to the uniaxial tensile tests for the reasons explained in 5.1. The curves drawn in figures 8 indicate small variations between unexposed and aged samples for HDPE geomembranes. These latest are softer (lower modulus) and have greater pressure and elongation at break. For the Bituminous/SBS geomembrane, the tendency is quite opposite. The differencies are very small for PVC and EPDM materials. The bituminous geomembrane was took away from the initial liner selection, because the bursting test shows that this material was porous under little deformation (<6%) and little pressure (<200 kPa). It was assumed that such a behaviour is inadequate for an secure use in landfills. The uniaxial tests under constant stress show for PVC/DOP and HDPE neither failure nor differences between the 3 media after 3 months. The future tests must be conducted at 50 degrees C to increase stress cracking, on samples with and without seams. Finally, the most important result of all these tests is that there is no noticeable difference between the exposed samples, i.e. there are no mechanical degradation due to leachate. This first result agrees with those presented in [12]. In this study, Low Density polyethylene, PVC, EPDM geomembranes were exposed during 56 months to landfill leachate at 10-20 degrees C. They changed only modestly in physical properties. 6.2 Hydraulical changes: Sorption tests were carried out on after 16 months ageing. Because of the long duration of the test (many months at 20 degrees C), it is not possible to get the diffusivity. But the comparison of the beginning of the curves for the PVC shows an acceleration of diffusion, which is higher for samples exposed to distillated water (Figure 9). The differences are however very small. Because of the very low difusivity of HDPE, no changes are noticeable yet. Figure 9: Absorption of water in PVC/DOP Samples 1-Unexposed, 2-Compacted wastes leachate, 3-Crusched wastes leachate, 4-Distillated water 6.3 Chances at molecular level These tests are more sensitive than the macroscopic tests. The HDPE matrix shows no oxidation trace, even in the superficial layer (0-24 mm) , as well at 20 degrees C or at 50 degrees C. The HDPE geomembrane contains an anti-oxidizing agent owning an ester function (extrenum at 1736 cm-1) . This ester is hydrolised producing OH groups in the hydroxile zone (3100 to 3500 cm-1). The hydrolisis is very small at 20 degrees C in distillated water, and still smaller with the compacted wastes leachate at 20 degrees C (<5%) (Figure 10) . It is located in the superficial zones (0-25 m m) This reaction is higher with leachate at 50 degrees C, where the ester is quite consumed in the first 30 m m but remains intact after 100 m m (Figure 11, available on hard copy) . This last result is conform to the fact that hydrolisis increases with temperature. Like HDPE, the PVC matrix is oxidized in any environment. On the other hand, the DOP plasticizer (extremum at 1580 and 1600 cm-1 On figure 12) is hydrolised producing an acid of phtalic type and alcohols (range from 3100 to 3500 =-1) (Figure 13, available on hard copy). At 20 degrees C, this reaction is more important in leachate than in distillated water, because hydrolisis is higher when pH is different from 7, and faster at 50 degrees C. In all the cases, the loss of plasticizer is limited to the first 80 m m. After 16 months exposure to leachate at 20 degrees C, EPDM matrix presents also no oxydation. On the other hand, there is a small oxidation in bituminous/SBS samples which is faster at 500C, due to the thermical evolution of SBS elastomer (Figure 14, available on hard copy). The water absorbtion in these 2 materials is important. As conclusion of these analytical tests, it was found there is no strong oxidation of the geomembranes, whatever the environmental conditions. There is only an hydrolisis of the additives, but this one is very limitated in quantity and in thickness. All the observed facts are of minor importance. CONCLUSION With the increasing use of geomembranes in domestic wastes landfills, the question of their chemical compatibility to leachate and their long-term durability becomes crucial. The study here described aims to give some information on this point. The first results after an exposure of 16 months at room temperature and 3..5 months at 5O degrees C shows that all the tested geomembranes keep their initial characteristics. But this too short ageing time cannot lead to any conclusion yet. The ageing kinetic must be calculated on longer period to assess the durability of the liner when the degradations, if they occur, are of greater importance. It is therefore provided to make a complete tests programme every one or two years during at least 5 years. It was shown that an ageing programme is based on one hand on a good definition and simulation of the environmental stresses (temperature, strains, seams,..) taking into account their synergy, and on the other hand, on judicious selected tests to assess the changes. The macroscopic tests are used to compare the geomembrane characteristics to reference design criteria. The microscopic tests aim to describe the ageing processes to be interpreted, quantified, and to assess their durability. But the environmental durability must not be the only choice criterion for a geomembrane. Its long-term mechanical behaviour, its aptitude for laying and seaming, its adequation with the other elements of the tightness system, are also of great importance and must be taken into account. It is therefore necessary to put the chemical behaviour of the materials at the right level of stability referring to the real environmental stresses. For instance, the nature of the domestic wastes leachate, even if it is of more complex composition, is certainly less aggressive for geosynthetics as hazardous wastes leachate. Then, the materials chosen after simulation tests for hazardous wastes (for instance EPA 9090 method) are not necessary the best ones for some domestic landfills applications. In these conditions, the procedure for the choice of the products will give an enough range of acceptable materials for the design of the best liner in each situation.   REFERENCES [1] STIEF, K. (1989) "Deponietechnik im Umbruch. Nachbesserung bestehender Deponien". ZeitgemiBe Deponietechnik III. Stuttgarter Berichte zur Abfallwirtschaft. Erich Schmidt Verlag, Bielefeld. pp-7-31. [2]LANDRETH, R.E. (1988) "Durability of geosynthetics in waste management facilities : needed research". Proceedings of a Seminar on Durability and Ageing of Geosynthetics. GRI, Drexel University, USA. [3] HAXO, H.E. and MAXO, P.D. (1988) "Environmental conditions encountered by geosynthetics in waste containment applications". proceedings of a Seminar on Durability and Ageing of Geosynthetics. GRI, Drexel University, USA. [4] PRIGENT, E. (1990) "Contribution A l’etude de la compatibilite chimique des geomembranes aux percolate de de d6charges dlordures m6nag&res'. CEKAGREF. Memoire de 36me ann6e de IIENITRTS. 133 P. [5] HALSE, Y.H.; KO@ER, R.M. and LORD, A.E. (1982) "Laboratory evaluation of stress - cracking in MDPE geomembrane seams". Proceedings of a Seminar on Durability and Ageing of Geosynthetics. GRI, Drexel University, USA. [6] PEGGS, M.D. and CARLSON, D.S. (1988) "Stress cracking of polyethylene geomembranes : field experiences". Proceedings of a Seminar on Durability and Ageing of Geosynthetics. GRI, Drexel University, USA. [7] REYNE, M. (1990) "Les plastiques. Applications et transformations." Traitte des Nouvelles Technoloqies. Serie ,materiaux. Ed. Hermes, Paris. 268 P. [8] FAME, Y.H.; PIERSON, P; ARTIERES, 0. and GOUSSE, F. (1990). "Tests of geomembranes water permeability". Proceedings of the 4th International Conference on Geotextiles, Geomembranes and Related Products. Ed. G. den Hoedt, A.A. Balkema, Rotterdam. pp. 543-553. [9] VERSCHOOR, K.L.; WHITE, D.F. and THOMAS, R.W. (1990) "An cverview of practicies used in the United States to determine the compatibility of geosynthetics with chemical wastes". Proceedings of the 4th International Conference on Geotextiles, Geomembranes and Related Products. Ed. G. den Hoedt, A.A. Balkema, Rotterdam. pp. 715-718., [10] VAN LANGENHOVE, L. (1990) "Conclusions of an extensive BRITE-research programme on ageing". Proceedings of the 4th International Conference on Geotextiles Geomembranes and Related Products. Ed. G. den Hoedt, A.A. Balkema, Rotterdam. pp. 703-707. [11] JOUAN, X. and - GARDETTE, J.L. (1987) "Development of micro (Fti.r) spectrophotometric method for characterization of heterogeneities in polymer films". Polymer commnications, Vol. 28, december, pp 329-331. [12] HAXO, E.E. and NELSON N.A. (1984) "Factors in the durability of polymeric membrane liners". Proceedings of the International Conference on Geomembranes, Denver, IFAI, pp. 287-292.   For more information call   800-OK-LINER  today!

PVC GEOMEMBRANES IN MUNICIPAL WASTE LANDFILL LINERS AND COVERS: THE FACTS I. D. Peggs, Ph.D., P.Eng. I-CORP INTERNATIONAL INTRODUCTION "The liner system shall consist of the following: i. a leachate collection and removal system designed ii. a 3-foot recompacted clay liner iii. a leak detection system designed iv. a geomembrane liner at least 60 mil thick." This is a rule in the draft of one state's Solid Waste Regulations. The impression is left that the leachate and leak systems are designed but that as long as a 60 mil geomembrane (of any type) is used, it will be adequate. Unfortunately, as experience has shown, geomembranes cannot be so simply regulated. The selection and design of the geomembrane components of landfill lining and cover systems are not simple matters if optimum durability is required. A designer cannot blindly take any material of a predetermined regulated (implying satisfactory) minimum thickness "off the shelf" and apply it for all systems, on all slopes, on all subgrades, with all leachates, in all environments, and for all landfill operating procedures. If such a practice is followed, and often it is, the liner is not 'designed' and will probably fail before its intended service life. And there have been a- significant number of geomembrane failures in landfills and liquid impoundments, mostly the latter. There is not one universally acceptable geomembrane material because all materials have their Achilles Heel - it is simply a matter of recognizing the negative feature of each material and designing around it, to take advantage of the positive aspects of each material. This is why geomembrane lining systems need to be competently designed in the first place. Subsequently, they must then be reviewed and approved by informed regulatory design engineers' Geomembrane thickness is only one of the integral parameters in the design process and should not be arbitrarily legislated at one value to cover all potential materials. The flexibility to properly design a given system is essential if optimum performance is to be achieved, and if advances in materials are to be taken advantage of. My objective in this document is to show that polyvinyl chloride (PVC), in its variant forms, has a large number of very desirable properties and, therefore, is an excellent candidate material for consideration in all lining systems. However, that does not mean that it is a suitable material to use in all applications. Similarly, HDPE cannot arbitrarily be used in all lining systems. I am in the midst of a failure analysis of an HDPE linen, system that failed after 18 months use despite there being a written guarantee from the manufacturer that the material was chemically compatible with the impoundment contents. I have a second failure that occurred after 5 years in a plant that produced the HDPE resin from which the geomembrane was manufactured to line its own waste facilities. In this latter case, the resin manufacturers were not aware that their resin was inadequate for geomembrane applications. There is a general feeling at the grass roots level of the regulatory and designing arenas that HDPE is the geomembrane of choice and will meet all waste containment performance requirements. It will not do that, and those who have had failures certainly would not agree with that feeling I believe that the extreme confidence that the geomembrane users place in HDPE is as unjustified as the lack of confidence they place in other materials such as PVC. This is somewhat strange since PVC has, apparently, been so successfully used for waste containment for over 36 years. I would like to dispel the myths about PVC so that it will come out of the starting gate being considered by competent designers on its technical merits (and demerits) only - not with preconceived emotional feelings. The regulatory agencies must play a large part in this procedure by positively requiring comprehensive design processes, and not by imposing restrictions that unintentionally discourage necessary design efforts. Certainly it may be necessary to define the 'entry level', or to make the 'initial cut', but this must not be done in such a way that the intended minimum criteria be perceived as the only criteria that need to be met. And the minimum criteria should not be written in such a way that, unintentionally, adequate candidate materials, both old and new, are eliminated. There are two groups of people and institutions that always have, and always will lose their battles: those who stick will the old, ignoring new developments, and those who blindly jump to the new, not fully recognizing the problems of the new (see Figure 1). Those who remain flexible and take advantage of both will be the winners. The PVC geomembrane manufacturers are attempting to recover from the former. Those who have had HDPE failures are suffering from the latter. As one considers PVC and HDPE (and other) geomembranes, one must remember that there are many types and grades of each of them. Saying 'HDPE' and 'PVC' is like saying 'steel': there are many different types of steels (ferritic, austenitic, martensitic, and others) formulated to meet different service conditions. There are many PVC geomembranes formulated to meet specific environmental applications. HDPEs also are different but, at the present stage of geomembrane development, they are different not so much by design but by default, due to the different resin types. 'Me factors responsible for the widely variable fundamental stress cracking resistance (mechanical durability) of HDPE are not yet fully understood, and, therefore, cannot be intentionally engineered. It, therefore, follows that just because a failure has occurred in a PVC or HDPE geomembrane, it does not automatically mean that all other PVC and HDPE products will fall under the same circumstances. Except for a relatively small number of failures that have occurred due to the selection of inappropriate materials,, the majority of geomembrane failures have occurred due to inadequate design, poor installation workmanship, or inattentive Construction Quality Assurance (CQA). There is no question that, to prevent failures, the emphasis must be placed on proper design and CQA. And this, most certainly, includes proper design after the correct material has been selected. PVC PERFORMANCE To dismiss some of the perceived concerns of PVC, the following, generally-expressed myths about PVC are addressed: It contains pinholes and therefore a lining cannot be made leak-free. It does not have adequate chemical resistance. It does not have adequate weathering resistance to ultraviolet (UV) and thermal radiation. It becomes brittle at low temperatures. Plasticizers leach out, or volatilize, causing, unacceptable material degradation. The CQA associated with PVC is inadequate. In addressing these misconceptions, one should keep in mind that the major factor is whether the material continues to function as intended. The fact that some changes occur is irrelevant unless they affect the functional performance of the geomembrane. In other words, different materials may change at different rates as they age, but both could still provide in excess of the required performance (Figure 2). The fact that one changes more than another is irrelevant.   Pinholes Since a geomembrane is intended to be in impermeable barrier, pinholes are not desirable features. However, no geomembrane is absolutely impermeable, a fact that is difficult for -any of us to accept, but one that is the basis for our acceptance of the need to install double lining systems. In all CQA plans, project specifications, and regulatory aspects, it is necessary to consider that ideals may not be practically achievable and that real world (practical) situations inevitably require some compromise. PVC sheeting has been made in thin gages (as low as 4 mil) for vapor barriers, swimming pool liners, and critical medical applications for many years without pinholes. With continuous inplant backlighting QC techniques for continuous examination of manufactured geomembranes and more detailed examination under stress of QC samples, geomembranes with pinholes should not appear on site. There are ASTM standards(e.g.D4451)and Federal Specifications(e.g. L-P-375C) that demand that PVC membranes in thicknesses greater than 10 mil contain absolutely no pinholes. Alberta Environment (1) has used many millions of square feet of 20 mil PVC geomembrane for lining irrigation canals and, several years ago, had a specification of 1 pinhole(maximum) per 100 ft 2 of geomembrane. After thorough examination of a large amount of geomembrane, they concluded that pinholes were statistically nonexistent. Improved methods of calendering have effectively eliminated pinholes in PVC sheet and geomembranes: the geomembrane passes through 3 or 4 sets of caleadering rolls (Figure 3) in which semi-molten material is squeezed to fill any existing, small voids. The US Bureau of Reclamation has also used immense areas of PVC geomembrane to line irrigation canals and reservoirs and has had a similar experience with (the lack of) pinholes in PVC geomembrane. Many years ago (1960's), they experienced a few pinholes in 10 mil material, but after changing to 20 mil geomembrane, they found it unnecessary to have a pinhole specification. They have done a large amount of laboratory testing with 20 mil PVC, such as hydrostatic burst and puncture testing, and have never had a premature test failure due to pinholes. They have also used 20 mil PVC, in 5 x 10 ft panels, to provide critical water proofing in other laboratory tests, without premature failures. It is inappropriate, and incorrect to propagate the myth that PVC contains pinholes and HDPE does not. In a recent CQA project, I-CORP found a 60 ft. length of installed 60 @l textured HDPE geomembrane that contained about 10 holes up to 80 mil in diameter. This, however, was a remote occurrence, just as it would be to see pinholes in PVC geomembranes. PVC, when used for medical collection bags (solids and liquids), and internal feeding and plasma bags must be, and is, totally free of pin holes. Chemical Resistance For landfill applications, the chemical resistance of the proposed geomembrane to the leachate is assessed by EPA Method 9090 "Compatibility Test for Waste and Membrane Liners" (3) . In this test, the geomembrane is exposed to leachate at 23 and 50° C for 120 days. Changes in properties are measured every 30 days. If there is no continuing degradation trend, or if changes reach an equilibrium condition within certain limits, the geomembrane is considered to be compatible with the leachate. As previously stated, for practical purposes, it is immaterial whether one of two types of the same material, or one of two different materials, ages more than the other if both still, and will continue to, adequately meet the project specifications. There is no question that for an given chemical containment requirement, there is more chance y. That HDPE (but not all HDPE's), rather than PVC, will provide the better absolute chemical resistance. However, for most municipal waste leachate applications, it is probable that PVC may provide more than adequate resistance for the required service. The historical performance of PVC geomembrane has proven this. Certainly, there have been a few well-publicized failures, as with HDPE, but there have been many more successes and a large number of successful laboratory test programs. It would be an unreasonable trade-off to use a fundamentally more chemically resistant material if other performance characteristics and durability are sacrificed. In preparing for this report, a survey of lining system designers and installers in North America and Europe was performed, asking the questions shown in Appendix 1. (Responses are also included in Appendix 1.) Most of the installers surveyed felt that PVC was much easier to install correctly than HDPE. A European respondent stated, appropriately and realistically: 'PVC is not suitable for ALL chemical contacts, but PVC is one of the best materials for the ratio price/properties, mechanical properties, weldability, and permanent elongation.' In other words, the selection of the most appropriate geomembrane becomes a project-specific decision. Three laboratories that perform EPA Method 9090 testing were surveyed for this project: GeoSyntec Consultants, Precision Laboratories, and Texas Research Institute. All have performed, or are presently performing, tests on PVC in hazardous and municipal waste leachates. None of the PVC geomembranes has failed the test. One of the tests in hazardous leachate his been performed at 85'C and, even though there has been some loss of plasticizer, the PVC geomembrane successfully passed the test. This confirms that it is extremely important to recognize that, even though some changes in properties occur, the material will still provide satisfactory service. It should be remembered that PVC can be formulated to provide protection against specific environments, e. oil-resistant PVC. It is clear that to obtain the optimum combination of material and performance, it is essential to assess the site-specific leachate resistance of each material and its seams. Semi-crystalline materials, such as HDPE, should, in addition, be tested under stress in the leachate to assess their stress cracking resistances. Chemical resistance work, presently being performed in France by Artieres (4) , includes the exposure of one HDPE and two PVC geomembranes to two different municipal solid waste (MSW) leachates. While this study provides an opportunity to directly compare the performances of PVC and HDPE in MSW leachates, it again must be remembered that only two PVCs and one HDPE of the many variants that exist have been assessed. The surface reactions of the exposed specimens were carefully examined by the sophisticated Fourier Transform Infrared (FTIR) technique. After 16 months at 20° C and 3.5 months at 50° C, the surface of the PVC had been affected only to a depth of 80 m m. In the same time period, the HDPE had been affected to a slightly larger depth of 100 m m. There is, therefore, very little difference in the chemical resistance of these PVCs and this HDPE to the two MSW leachates - both materials could probably adequately contain the leachates. In assessing chemical resistance, the last thing that should be used is a standard chemical compatibility table. Such tables are notoriously inconsistent. Artieres (4) states: "But the environmental durability must not be the only choice criterion for a geomembrane. Its long-term mechanical behavior, its aptitude for laying and seaming, its adequation (sic) with the other elements of the tightness system, are also of great importance and must be taken into account."  I have investigated three HDPE liner failures in which the standard chemical resistance tables indicate that the HDPE is compatible with the contents of the ponds (nitric acid and black liquor). In one case, the liner manufacturer had provided a written guarantee that the HDPE would be resistant to the black liquor for 10 years. The black liquor pond liner failed after 12 to 18 months by environmental stress cracking. The nitric acid pond liner failed after 9 months, also by environmental stress cracking. In the latter case, there was even sufficient residual stress in the extruded fillet seam bead to initiate stress cracking in the bead, independently of the service stress on the geomembrane. Two of the laboratories performing EPA Method 9090 tests commented that MSW leachates are getting weaker, as the wastes placed in landfills become more controlled. The third agreed in principal, but identified two municipal leachates they have tested as containing 'bad actors'. In the recently promulgated Part 258 of 40 CFR 'Criteria for Classification of Solid Waste Disposal Facilities and Practice' (colloquially known as Subtitle D), there are indications (pp 24 and 25) that there is little difference in the toxic constituents of leachates generated in true municipal waste landfills (built since 1980) and those operated prior to 1980 that contained industrial wastes in addition to municipal wastes. It is possible, therefore, that municipal landfills that accept industrial wastes may not have significantly more obnoxious leachates than those that accept municipal waste only. Such co-disposal of municipal and industrial wastes can be used to advantage since there is evidence (5) that it can be done in such a way as to promote the degradation of the municipal waste. There is a large amount of evidence, not only from EPA Method 9090 testing,, but also from field experience, that PVC is apparently (many installations have not been directly measuring leakage rates) satisfactorily containing municipal waste leachates. For instance, samples of PVC geomembrane removed from the sump of Lycoming County, PA, landfill after exposure to leachate for 11 years are still very flexible and show no visible signs of degradation (6) . The few problems that have occurred are, as in most HDPE liner failures, related to inadequate design, poor installation, and/or poor CQA. In summary, there is no justification for taking the following two approaches to geomembrane chemical resistance: 1) to dismiss PVC out of hand saying it does not have adequate leachate resistance; and 2) to assume that HDPE will perform adequately without appropriately testing it. Weathering and Thermal Resistance This is the most confusing area of concern with PVC. In North America, we are adamant that PVC should not be left exposed to the elements; yet in Europe, PVC is quite regularly left exposed on critical installations, such as the upstream faces of hydroelectric dams. In one installation(7), PVC has provided excellent service for more than 12 years at an elevation of over 6000 ft. In Sicily, an exposed PVC roofing membrane has provided a watertight seal at a chemical plant for over 18 years(8). The US Bureau of Reclamation(9) has investigated 10 mil thick PVC geomembrane that has been installed on irrigation canal side slopes for up to 27 years, and while it has lost some plasticizer, there is still sufficient plasticizer remaining for the geomembrane to have adequate ductility and flexibility for continued service. Once again, the important factor is that material still performs its intended function despite the fact that it has aged. Plasticizers are added in sufficient quantities for the intended service, recognizing that some will be lost in service. Similarly, antioxidant packages are added to HDPE to prevent damaging thermal oxidation during extrusion, seaming, repairing, and service. Just as PVC can lose some (not all) plasticizer during aging, HDPE can age by consumption of antioxidant as it experiences temperatures as high as 80°C or more in summer sunshine. In other words, it is expected that a portion of these additives will be lost during different phases of service, but that fact alone is immaterial provided sufficient additive remains. Figure 4, developed from the Bureau of Reclamation data(9) shows the rate of plasticizer loss in PVC. Initially, plasticizer is lost rapidly from the surface layers of the geomembrane: 30% of the plasticizer may be lost in the first 4 years of service. As plasticizer begins to diffuse from the interior of the geomembrane, the rate of loss decreases resulting in less than 50% being lost after 19 years. The rate of loss will continue to decrease. These figures were generated on 10 mil PVC geomembrane. The thicker the geomembrane and the lower the surface area to volume ratio, the lower the rate of loss of plasticizer will be. An appropriately formulated 30 mil PVC geomembrane should, therefore, lose no significant amounts of plasticizer in service. Figure 5 shows that even if 75% of the plasticizer is removed from PVC, causing the geomembrane strength and puncture and tear resistances to increase, and the ductility to decrease, the elongation at break may still exceed 100%. last value is still more than 10 times greater thin the useful strain (the yield strain) allowable in HDPE. In HDPE, once the yield strain has been exceeded the material will continue to elongate at a stress lower than the yield stress. It has been implied that rats and rodents eat PVC geomembrane because they become addicted to plasticizers. Yet the documents that report this work clearly state(10) that "the undigested debris could be detected in their (the rats) excrement." This does not suggest, as often implied, that the rats eat the PVC for its nutritional (food) value, but rather that they find it easy to gnaw on, as rats must continually do. Rats do gnaw on the edges of HDPE geomembrane and on folded corners with an angle of less than 90° (11), i.e., in regions they can get their teeth into. Elsewhere, the HDPE is too hard and smooth for them to get a bite. Reportedly(10), PVC is not attacked when it does not contain plasticizer; however, without plasticizer, PVC is very hard and may not be possible to bite into. The report itself states: "At the moment, it has not been determined whether the 'addiction' (quotations by Peggs) is of a chemical or tactile nature." In a related document(12), it is stated: "The polyethylene and polyvinyl chloride membranes used to date in The Netherlands have shown good resistance to such attack. Damage due to rats, wood borers, algae, barnacles, or mussels was not observed . . . " However, consistent with the Dutch findings, a survey of PVC geomembrane users identified only one or two positive cases where holes have been gnawed in liners. Where rodents have penetrated PVC in the field, they have only done it to gain access to the warmth behind the liner, not because they find the plasticizer good to eat. & the other band, HDPE is normally claimed to be inedible by rodents. However, at a power station on one of the Great Lakes, there has been ample evidence, in the form of 1 in. diameter holes, that vole-type rodents do burrow through HDPE. These cases may be the exceptions that prove the rule. They also identify the danger of generic statements, and the resultant possibility of avoiding perfectly adequate materials based on misstatements. PVC geomembranes are now being successfully heat seamed in the U.S. They have been successfully heat seamed for many years in Europe. If the geomembrane can tolerate seaming temperatures without degrading in service at the seams, it can tolerate the thermal effects of exposure to sunlight for extended service periods, as proven on dams and roofs. For landfill liners and covers, most weathering/thermal problems are eliminated by the regulatory requirements for covering the liner with various types of soil and other geosynthetic layers. Such layers protect the geomembrane from ultraviolet and severe thermal effects. Low Temperature Brittleness and Mechanical Properties PVC canal liners have been successfully installed during Canadian winters with a maximum brittleness temperature specification of -20° C(ASTM D1790). When deployed, a covering layer of stones is dumped onto the geomembrane from a conveyor belt. This is a severe cold impact test which the geomembrane withstands. National Sanitation Foundation (NSF) International Standard 54 'Flexible Membrane Liners'(13) specifies a maximum brittleness temperature of -29° C for PVC geomembrane. This is even more stringent than the Canadian specifications which have proven satisfactory in harsh service environments. Since most landfill CQA plans require that geomembrane shall not be seamed (thereby meaning 'installed') below 5'C, PVC should be able to withstand most installation environments. Once installed, the soil cover will protect the geomembrane from extremely low temperatures. Even if the temperature does reach the -20° C range under the soil, a PVC geomembrane should continue to provide adequate protection. If the geomembrane is only subject to static loading, it will be protective to much lower temperatures than -30'C, since the brittleness temperature is determined by an impact procedure (ASTM D1790). The measured brittleness temperature of HDPE (ASTM D746) appears to be considerably lower than that for PVC, but once again, is this really of practical significance? It will depend on the particular installation. It should be noted that PVC is tested by impacting a beat strip, while HDPE is tested by striking a single thickness cantilevered specimen. The PVC test is far more severe and will, therefore, show a higher brittleness temperature. If PVC has other favorable properties, but for some project specific reason must be installed when it is cold, it may be only necessary to take a little extra care during its installation. This is no different to the extra care that is required when installing HDPE to minimize its potential for stress cracking in service. The majority of designers and installers surveyed for this project agree (Appendix 1) that PVC has better mechanical properties and is easier to install than HDPE. HDPE is a problem because of the yield point in its stress/strain curve (Figure 6) that occurs at approximately 12% strain. This point of instability is of major concern to the designer. When allowing for biaxial stress conditions, as occur in geomembranes in the field, and low temperatures, it is necessary to design for maximum strains in the order of 2 or 3 %. Since PVC does not have a yield point, the designer can make use of strains to the breaking point - in excess of 300% at room temperature under uniaxial conditions. The level of comfort gained by the designer when using a material that has a steadily changing stress/strain curve is significant; the designer is able to give a facility owner an installation with a larger factor of safety and therefore, a wider range of operating conditions. However, once again, mechanical properties are not the only factors that should be considered in liner/cover design. If the subgrade is not subject to settlement, tensile properties may be of less significance. If slopes are steep, and friction angles are high on one side of the geomembrane and low on the other, mechanical properties could be extremely important. Quality Control and Construction Quality Assurance There is a feeling among regulators and users that the qualities of HDPE geomembranes and geomembrane seams are higher than those of PVC since the HDPE industry has been required to provide more visible QC documentation and CQA documentation. Comprehensive CQA is absolutely essential for HDPE, particularly in locations where it can be very cold, since its service performance is critically dependent upon proper installation in many respects - it is not as forgiving a material as PVC. HDPE's window of seaming parameters is narrow, allowance for expansion and contraction must be provided, and the conditions that produce stress cracking must be avoided. It is not surprising that more CQA attention is paid to HDPE. Many owners of facilities have demanded detailed CQA plans for HDPE, but only recently have requested that similar CQA plans be prepared for PVC installations. The manufacturers and installers of PVC geomembrane, at their own discretion, have also recently generated comprehensive QC documents and CQA plans. Such documents can become part of CQA plans, and can be useful to regulators in those instances when adequate CQA Plans are not available. The past absence of CQA plans for PVC has unquestionably been a function of most designers’ experiences with PVC, and the fact that PVC has generally performed satisfactorily without major installation controls. The survey (Appendix 1) of nationally recognized designers and geomembrane installers (those who regularly install both PVC and HDPE) in the USA and Canada, elicited the fact that most felt most comfortable working firstly with PVC, secondly with VLDPE, and thirdly with HDPE. A number of significant comments returned with the survey are as follows: "Some HDPE resins are a (expletive) to weld and some are easier, the whole gamut of seamability". "PVC is hard to generalize, there are so many types available" "Although the mechanical and temperature characteristics of HDPE are less than ideal, its chemical inertness and weldability make it the material of choice" "PVC has the best overall mechanical properties" "I feel most comfortable with all the types of geomembranes and all design aspects, except repairability". "PVC is low tech seaming, high performance product. HDPE is high tech seaming" "Eliminate chemical resistance and long term stability and HDPE doesn't have much going for it" It is clear that neither PVC nor HDPE is the better geomembrane in all applications. It is also clear that a selection must be made on a project specific basis, with due allowance being made for the less desirable features of each material. Experienced designers will take and work with each material on its own technical merits, not on pre-selected generalities. The CQA plan will have to be prepared for the specific material being used in the Project in order to complement the advantageous materials properties being utilized. For instance, it has been pointed out that the uniaxial stress-strain curve of HDPE (Figure 6) contains a yield point at approximately 12% strain while the curve for PVC shows no point of instability up to the break strain of over 300 %: there will be instances when it will be necessary to work with the uniformity and predictability of the PVC curve, and them will be other instances when the point of instability (yield point) of the HDPE is immaterial. Another significant difference between PVC and HDPE occurs in their puncture performances as shown schematically in Figure 7. The maximum force required to puncture an HDPE geomembrane is higher thin that required to puncture a PVC geomembrane, which might indicate that HDPE is mom puncture resistant than PVC. However, the PVC geomembrane has a much higher puncture strain than the HDPE, which may be of more importance, for instance, in the case of subgrade settlement and in the case of conformance to a rough subgrade. In other words, the PVC will retain effective barrier properties under a much higher strain than HDPE. For PVC, the puncture performance is complete at this stage, but for HDPE there are additional implications: even though the puncture strength and s@ may not be instantaneously exceeded, a constantly applied puncture stress (even 40 % of the yield stress) may ultimately cause a stress cracking failure. Here again is evidence that the interaction and synergism of several individual properties of any material must be considered in order to achieve the optimum design.' The CQA plan for a PVC geomembrane liner need not, apparently, be as extensive as one for HDPE. An increasing number of state regulations are requiring comprehensive CQA programs on lining system installation, thereby putting HDPE, PVC, and other materials, on an equal footing. However, it will still be necessary to ensure that the correct information is requested in the CQA plan, and that each plan is customized to account for the problematic parameters of each material, whether that material be PVC or HDPE. Seams All geomembranes require some field seaming. It is universally recognized that field prepared seams are potentially the most problematic features of lining systems. The width of HDPE geomembrane rolls is steadily increasing in order to minimize the number of field seams required. PVC, on the other hand, is seamed under controlled conditions in the fabrication plant to produce larger panels, thereby reducing the number of field seams required. In a given liner area, the length of field seam required in a PVC liner may be 20% of that required in an HDPE liner. For any project, it is better to have fewer field seams to minimize the potential problems associated with them. Whether to have a few field seams or a larger number of field seams is a decision only the designer can make. Such a point was concluded by the Bureau of Reclamation(14) in its study on the chemical exposure and weathering of FML field seams: 'Generic-type material specifications are not sufficient to ensure satisfactory performance of FML seams when used for hazardous waste containment applications'. Until recently, most field seams in PVC have been made with a chemical (adhesive or solvent). Now hot wedge equipment, the same as that preferred for long-run HDPE seaming, is used for PVC geomembrane seaming. It can be used in a wider range of environmental conditions than chemicals. Thermal fusion methods of joining PVC have been used for many years in the roofing industry and in the European geomembrane industry. Double hot wedge (and hot air) fusion offers all the control features and nondestructive testing capabilities in PVC as it does for HDPE. Thickness For many years EPA has recognized, as now have the more enlightened states, that a single minimum thickness is not an adequate criterion for geomembranes used in landfill liner and cover applications. All materials are not equal, and cannot so simply be reduced to a single common denominator. Due to its semi-crystalline nature, HDPE is a different breed of geomembrane and within its ranks are many sub-species. Even if a single thickness requirement is based on HDPE, there are many types of HDPE geomembrane that would not perform satisfactorily even at twice a minimum thickness of 60 mil. At this moment, I am investigating, a stress cracking failure that occurred, after five years service, in an HDPE liner 100 mil thick that was not exposed to low temperatures. In such instances, thickness has absolutely no influence on the performance of the geomembrane. Other parameters must be considered for every type of traditional and novel geomembrane lining installation. A single thickness value, such as 60 mil, is selected based on HDPE, but where realistic technical considerations have been given to other materials, such as PVC and Hypalon, thicknesses in the range of 30 rail are considered adequate. In Subtitle D (p32), a composite bottom liner is required to have a primary geomembrane with a minimum thickness of 30 mil, but if the geomembrane is HDPE, it must be at least 60 mil thick. A higher thickness for HDPE is understood to be required to make allowance for its problematic features; it is difficult to seam at thicknesses less than 40 mil, and the grinding required on preparation for fillet extrusion seaming produces reduced thickness in the notch sensitive area at the edge of the seam. la fact, with a tolerance of ± 10%(13) on HDPE geomembrane thickness and the supposed maximum grinding depth(15) of 10 % of geomembrane thickness, 60 mil HDPE geomembrane could be almost 40 mil thick adjacent to extruded seams, patches, and penetrations. EPA has stated(16): "the design engineer should recognize that some geomembrane materials may require greater thicknesses to prevent failure or to accommodate unique seaming requirements." The norm is the 30 mil figure. HDPE is the exception that requires additional thickness. PVC and the other geomembranes should not be penalized because of HDPE's perceived deficiencies. There is also some feeling that thicker HDPE is necessary to provide improved stress cracking resistance. This is not so, since stress cracking resistance is a fundamental material property. In fact, the use of a thicker material with the same surface scratches and defects as a thinner material may increase the susceptibility of the liner to stress cracking; the applied stress must be lower and closer to the brittle fracture range. As a constant stress on an HDPE geomembrane decreases from the yield stress, the break mode changes from ductile to the brittle (stress cracking) mode. In a given situation, a thicker HDPE geomembrane may be more inappropriate than a thinner one. One disadvantage, therefore, of specifying a minimum thickness is that it may eliminate excellent candidate geomembranes. Even the best available geomembrane, that would perform adequately at lower thicknesses, may be eliminated on the basis of cost at higher thicknesses. The intent of regulations is to provide safer waste containment, not simply more expensive waste containment. And, as discussed, a minimum thickness may not be functional, even if that thickness is tailored for the specific material selected. Another disadvantage of specifying a minimum thickness, whether or not there are one or two values to suit different materials, is the danger that some 'designers' will read it as a specification, i.e. a geomembrane of the minimum thickness will perform the job, and no other factors need be considered. The same sentiment was expressed by Bob Landreth, chief of EPA's Landfill Technology Section(17): "Thickness of materials should be a function of design which implies site specific information and considerations. Although other thicknesses, 30 and 60 mils, are allowed (page v), this approach, we believe, ties the hands of the designer and will force the use of generic designs and could lead to increases in overall project costs. We also strongly believe and as part of our recommendation to consultants (sic) that a minimum thickness of material type should be specified then let the consultants "design" the system. Our recommendations based on seamability, punctureability and instalability is (sic) as follows: Type Min Thickness (mil) PVC 20-30 (30 is very tough) CPE 30CSPE-R 36 Polyethylene* 60* Polyethylene is set as a 60 mil minimum primarily from a seamability standpoint. It has not been clearly demonstrated to us that PE products less than 60 mil can be constantly (sic) seamed in the field. 'Mere is also concern that this is at the lower limit for creating conditions that encourages (sic) stress cracking. While stress cracking is still under review we are starting to see improvements in seaming techniques. It is interesting to note that the West German are now requiring PE thickness greater than 100 mil. CLOSURE A number of geomembranes, including PVC geomembranes, have apparently been used successfully, for many years, to contain municipal and hazardous wastes. PVC does not suddenly become inappropriate because HDPE geomembranes have become available. It is desirable to design geomembrane lining systems using the most cost effective material that will best achieve the performance specifications. Regulations should be written to accommodate all candidate materials that will adequately perform the required function, and the performance of that function should be decided by proper engineering design, not by a regulatory recipe. In no way can a regulation provide a satisfactory design. In the September/October 1990 issue of Geotechnical Fabrics Report, Bob Landreth of EPA's Risk Reduction Engineering Laboratory stated: "The modifications (to chemical analysis techniques and control of wastes) should increase the number of geomembrane compositions available for use. The increased number of geomembrane compositions should now allow the designer to develop innovative designs. We (EPA) believe innovative designs will be more economical, technically viable, and be more reliable." As knowledgeable designers and regulators recognize, optimum design cannot be achieved by regulating a single minimum geomembrane thickness. At least two minimum thicknesses are required to accommodate two fundamental types of materials; amorphous thermoplastics (such as PVC) and semi-crystalline thermoplastics (such as HDPE). The minimum thicknesses, (30 mil and 60 mil respectively), specified in Subtitle D are acceptable to producers of both these classes of materials. It is hoped that the information presented in this paper will assist users, designers, and regulators in being open to the use of PVC on the basis of its technical merits. There is a wide range of geomembrane materials available with many interesting and useful properties, but no one material is a panacea appropriate for all applications. The positive attributes of each material should be compared to the prime requirements of each project in order to make the primary selection of candidate materials. The negative attributes of each material should then be assessed to determine which ones can most easily be accommodated. The optimum selection of geomembrane material can then be made. PVC has performed well in the past and, as it continues to be improved, it will perform well in municipal solid waste landfills in the future. Designers and regulators can achieve more, and widen the window of environmental protection, by taking advantage of the many unique properties of PVC. REFERENCES 1. Private Communication. Alberta Environment, October, 1991. Private Communication. US Bureau of Reclamation, October, 1991.EPA Method 9090. "Compatibility Test for Waste and Membrane Liners". U.S. Environmental Protection Agency, September, 1986. Artieres, 0. Goussé,F., and Prigent, E. "Laboratory-Ageing of Geomembranes in Municipal Landfill Leachates". Proc. 3rd. International Landfill Symposium, CISA. Cagliari. October, 1991, pp. 587-603. Pohland, F. G. "Fundamental Principles and Management Strategies for Landfill Codisposal Practices". Ibid, pp. 1445-1460. Taylor, F. "Lycoming County Landfill Protected with Geomembrane". Geotechnical Fabrics Report. IFAI, July/Aug, 1991, pp. 22-25. 7. Private Communication. P. L. Sembenelli, October, 1991. 8. Private Communication. Alberto Scuero, October, 1991. Morrison, W. R. and Starbuck, J.G. "Performance of Plastic Canal Linings". REC ERC-84-1. US Bureau of Reclamation. January, 1984. 10. Steiniger, F. "The Effect of Burrower Attack on Dike Liners." Wasser Und Boden, 1968. 11. Einbrödt, H. "Testing of Schlegel Sheet for Rodent Resistance." Private communication. April, 1978. Zitcher, F. F. "Resistance to Microorganisms and Rodents." Plastics in Water Engineering. Wilhelm Ernst & Sohne, 1971. 13. NFS International Standard 54. "Flexible Membrane Liners". National Sanitation Foundation. May, 1991. Morrison, W. R. and Parkhill, L. D. "Evaluation of Flexible Membrane Liner Seams After Chemical Exposure and Simulated Weathering". EPA/600/2-87/015. US Environmental Protection Agency. February, 1987. Landreth, R. E. and Carson, D. A. "Technical Guidance Document: Inspection Techniques for the Fabrication of Geomembrane Field Seams". EPA/530/SW-91/051. US Environmental Protection Agency. May, 1991. Hartley, R. P. 'Technical Resource Document: Design, Construction, and Operation of Hazardous and Non- hazardous Waste Surface Impoundments'. EPA/530/SW-91/051. US Environmental Protection Agency. June, 1991. 17. Landreth, R. E. Letter to US Army Corps of Engineers. September, 1989 For more information call  800-OK-LINER  today!

GENERAL PVC is the common abbreviation for polyvinylchloride, one member of a large class of polymers, called vinyl. Most versatile of the thermoplastics, vinyl polymers are also among the oldest. They - when suitably compounded - range in form from soft and flexible to hard and rigid, either of which may be solid or cellular. CHEMISTRY Polyvinyl chloride polymer is, of course, produced from vinyl chloride monomer. The classical method of VCl manufacture is from the reaction of H Cl and acetylene:   H Cl + C 2 H 2               CH 2 CHCl Acetylene                  vinyl chloride monomer   This is a somewhat inefficient and expensive process. The method presently used involves the oxychlorination of ethylene to make ethylene dechloride which is subsequently cracked to vinyl chloride.   2 H Cl + ½ O 2 + Cl 2 + 2 C 2 H 4                   2 C 2 H 4 Cl 2 + H 2 O (ethylene)                                                 (ethylene dichloride)                                C 2 H 4 Cl 2                         CH 2 CHCl + HCl                                                                    (vinyl chloride)   The derivations and reactions involved are shown schematically below:   Vinyl chloride monomer, then, is the basic repeating unit of a polyvinyl chloride chain. This monomer is an easily liquefiable gas with a pleasant odor (B.P. - 20° C). The polymerization of this material is then carried out to produce high molecular weight polymer. Polymerization processes available are as follows: Suspension: Monomer is dispersed in water to form a suspension where the reaction occurs. Particle shape is like popcorn and particle size of the order of 50 micrometers. Emulsion: Monomer is emulsified in water. Particle sizes are usually less than 1 micrometer. Chain lengths and hence molecular weight can be controlled by polymerization temperatures. RESIN TYPES AND CHARACTERISTICS PVC resins can be classified as either general purpose or dispersion. General purpose resins are usually produced by suspension polymerization and the calendering resins used at C.G.T. fall into this category. Dispersion resins which are used in plastisols and organosols are produced primarily by emulsion polymerization where the fine particles are obtained. (A)Characteristics of general-purpose suspension PVC: The most important is molecular weight due to its great effect on processing and end product properties. Further, processing may also be affected by molecular weight distribution and by the degree of branching. Particle size and particle-size-distribution will affect compounding, processing and bulk handling. Large, fairly uniform particles are easier to handle and process. Fine particles will absorb plasticizer less evenly during dry blending. For most commercial suspension resins particles range from 50 - 150 micrometers. Gels are large resin particles that failed to fuse completely during processing and appear as small spots or lumps on finished film. There are inherent variations in heat stability amongst vinyl resins. These are attributed to differences in initiators, residual catalysts and impurities. (B) Characteristics of Emulsion Resins or Dispersion Resins: These resins fuse most rapidly because of their fine particle structure. Particle sizes range from 0.5 to 2.0 micrometers. Particle size and particle-size distribution affect the viscosity and stability of plastisols. Complete fusion of dispersion resins is generally considered to indicate complete solvation which is the solution formation of a resin by a solvent or plasticizer.  COMPOUNDING It should be noted that PVC resins, of themselves, are of no practical use. When fused they are hard, brittle compounds. Their inherent limited heat stability make any type of processing difficult if not impossible. Therefore, in order to produce a useful product other ingredients are added to the PVC resin for the purpose of: increasing flexibility providing adequate heat stability improving processability imparting aesthetic appeal Let's consider these ingredients in some detail: 1. PLASTICIZERS: Plasticizers are low boiling liquids or low molecular weight solids that are added to resins to alter processing and physical properties. They increase resin flexibility, softness and elongation. They increase low temperature flexibility but decrease hardness. They also reduce processing, temperatures and melt viscosity in the case of calendering. Plasticizers fall into two categories based on their solvating power and compatibility with resins: A. Primary Plasticizers: are able to solvate resins and retain compatibility on aging. Samples of these would be: DOP         Dioctyl phthalate S-711        Di (n-hexyl; n-octyl; n-decyl) phthalate (linear) DIDP        Di-iso decyl phthate B. Secondary Plasticizers : are so defined because of their limited solubility and compatibility and are, therefore, used only in conjunction with primary plasticizers. The ratio of primary to secondary depends on the type and quantity of the particular plasticizers. Secondary plasticizers are used to impart special properties such as: Low temperature flexibility:             - DMODA (di-normal octyl decyl adipate) - DOZ (di-octyl azelate) - DOA (di-octyl adipate) Flame retardance:             - Reofas 65 (tri-iso propyl phenyl phosphate) Electrical properties - tri-mellitates Cost reduction - Cereclor, chlorinated paraffins  In a separate category are the polymeric plasticizers. These are long chain molecules and are made from adipic, azelaic, sebacic acids and propylene and butylene glycols. The efficiency of polymerics is poor but volatility and migration are superior. An example of a polymeric plasticizer is Paraplex G-54. The characteristics sought in plasticizers can be summarized as follows: efficiency - This is the level or concentration needed to give a stated hardness, flexibility or modulus. The effect on low temperature flexibility. Solvating power: This influences the fluxing rate of the compound at a given temperature or at a minimum fluxing temperature. The fluxing rate relates directly to processing time. Permanence: This relates to volatility, extraction resistance, compatibility.  2. HEAT STABILIZERS : The chief purpose of a heat stabilizer is to prevent discoloration during processing of the resin compound. Degradation begins with the evolution of Hydrogen Chloride, at about 200° F Increasing sharply with time and temperature. Color changes parallel the amount of degradation running from white to yellow to brown to black. Therefore, the need for heat stabilizers. The most effective stabilizers have been found to be: Metal soaps: Barium -cadmium solids and liquids : Mark 725, Mark 311 Organo tin compounds: octyl tin mercaptide: Mark OTME poxies: epoxidized soya oil (G-62)The above are most likely most effective only when used in combination (synergism). What are some of the criteria in choosing a stabilizer system? The ability to prevent discoloration. The amount of lubrication involved. In calandering this can be of Critical importance. Mark 725 has low lubricating effect while Mark 311 contributes high lubrication effect. Plate-Out - a potential side-affect of processing and has been linked to certain barium-cadium stabilizers. Compatibility with the resin systems - for obvious reasons. Resistance to sulpher staining: atmospheric discoloration. 3. FILLERS: Essentially fillers are added to formulations to reduce costs, although they may offer other advantages - such as opacity, resistance to blocking, reduced plate-out, improved dry blending. On the other side, fillers can reduce tensile and tear strength, reduce elongation, cause stress whitening, reduce low temperature performance. The most common fillers used with PVC are calcined clays, and water-ground and precipitated calcium carbonates of particle size around 3 micrometers. Other fillers are silicas and talcs.  Examples of fillers used at C.G.T. are: - water ground calcium carbonate : Microwhite 25   Duramite - silica: Cab-O-Sil - Talc: Hi-Fine # 80 4. LUBRICANTS: These materials are of prime importance in PVC processing. They: Improve the internal flow characteristics of the compound. Reduce the tendency for the compound to stick to the process machinery. Improve the surface smoothness of the finished product. Improve heat stability by lowering internal and/or external friction. Examples of lubricants, with which you may be familiar, are stearic acid, calcium stearate, Wax E, polyethylene AC 617   5. PROCESSING AIDS: These may be regarded as low-melt viscosity, compatible solid plasticizers. They are added to lower processing temperature, improve roll release on calendars, reduce plate-out, promote fusion. They are usually added at concentrations of 5.0%. The most widely used processing aids are acrylic resins of which acryloid K 120N is an example.  7. OTHER ADDITIVES There are several other additives which we will list and comment on briefly: Impact Modifiers: These are used in rigid vinyls to improve impact resistance. These are usually acrylic or ABS polymers used at 10 - 15 phr levels. Examples are: Kureha BTA 111, Blendex 301. Light Stabilizers: for resistance to ultraviolet radiation. They are used in low concentrations 0.5 - 1.5 phr. An example is Tinuvin P which is produced by Ciba-Geigy. Flame Retardants : PVC is inherently self-extinguishing. However, the plasticizers and additives are not. Therefore, flame retardants are added. The most widely known one is antimony tri-oxide. Anti-Static Agents Fungicides: Vinyzene BP-5 Foaming Agents: Chemicals that decompose at predetermined temperatures to produce a certain volume of gas within the molten vinyl and thereby create a foam. Colorants: Both pigments and dyes can be used. However, dyes, which are soluble organic substances, are used sparingly due to their tendency toward migration and extract ability. Heat resistance of colorants must be carefully evaluate.  In summary, we have seen that a vinyl compound consists of the following components:- PVC resin - plasticizer - heat stabilizer - lubricant - special additive - colorants.  P. Lussier       For more information call   800-OK-LINER   today!

PW Technology News - October 1993PVC GEOMEMBRANES Fabricator boosts quality with speedy seam test   Seaming problems are nipped in the bud within 5 minutes, not 40 hours after they're made. Environmental Protection Inc. (EPI), a Mancelona, Mich.-based fabricator of poIyvinyl chloride (PVC) geomembrane liners, has developed a process that permits it to test the integrity of a welded seam within 5 minutes. Dubbed the Wolschon Test after its developer, the 5-minute process directly correlates with the ASTM's and NSF's (National Sanitation Foundation) standards for testing weld-seam integrity, which requires that sampIes be brought from the production floor into the lab to "acclimate" for 40 hours-allowing the seam to cure before peel-strength tests are done. The end result of the accelerated test is that EPI can correct flawed seams about 10 minutes after they’re made, instead of nearly three days later. "The procedure has allowed us to make any corrections in the seam before the problem gets away from us and a lot of flawed product is made," said Fred Rohe, [former] president of EPI. "And since the operator is getting such fast feedback, he is learning how to make the seam right in the first place more often". The numbers bear this out. Before implementing the system in December 1991, EPI seams didn’t meet the minimum NSF peel-strength standard of 10 lb/inch wide 25 times per 1,000 samples taken. The rate is down to 5 per 1,000 samples now. There’s no black magic involved in the test itself: samples are pulled from the production process and after 5 minutes tested for peel strength in a tensiometer. The tricky part was correlating the results with ASTM/NSF 40-hour standard.  EPI achieved this by comparing peel strength results from the Wolschon Tests with results from the ASTM/NSF procedure and looking for patterns. They soon became apparent; as the strength of the Wolschon Test sample average increased, so did the 40-hour test, and vice-versa. After 200 samples were taken, EPI established that Wolschon Test samples had to have a minimum peel strength of 4.25 lb/inch width in order to meet the 10 lb/inch wide standard after 40 hours of acclimation. "What this test basically does is allow us to predict from a 5-minute test what the results will be after 40 hours," Rohe elaborated. "It has also isolated the critical factors of what makes a good seam and what doesn't. "We found that what makes a difference is the time the chemical is allowed to react with the surface of the PVC before pressure is applied. Too little time and the surface won't be dissolved: too much time and the solvent will evaporate and the material will harden." PVC geomembrane liners are generally seamed twice: in the plant and at the point of installation. EPI buys 76-inch wide calendered PVC in rolls and seams them until a panel as large as 30,000 sq ft is formed. That web is then shipped to the field, where it is seamed again. EPI's Wolschon Test currently is applied to seams in the plant only, though the company is working on extending it to field welds as well. -Jim Callari Jim Callari, (1993), "Fabricator Boosts Quality With Speedy Seam Test", Plastics World, October 1993, Page 18   For more information call   800-OK-LINER  today!

Strength testing of thermal welded PVC geomembrane field seams using non-destructive air channel methods   by Rohe, Fred P. and Rohe, Daniel S. Environmental Protection, Inc. Click here for PDF Version Keywords: Geosynthetics, PVC, PVC Geomembrane, Quality Control, Thermal Welding, Air Channel, ASTM D7177, Case Studies, Closure, Final Covers, Geotechnical Design, Innovative Technologies, Landfill Construction, Landfill Design, Landfill Gas Management  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 evaluated by ASTM Committee D-35 and was adopted as ASTM D 7177 Standard Specification in June 2005 and has been published in time for use in 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 2 million square foot (185,000 M2) PVC geomembrane closure installed on the Georgia Pacific Paper mill sludge landfill in Parchment, MI, USA.  This first of its kind PVC air channel strength testing Quality Control program was developed in conjunction with the Michigan Department of Environmental Quality and the design engineers at Blasland Bouck and Lee, Inc. (BB&L).  The 30 mil PVC geomembrane was installed using dual track thermal welding and over 10 kilometers (6 Miles) of field seams were air channel tested for seam peel strength and continuity.  The success of this project has provided the basis for implementing this new technology for testing PVC geomembrane field welds and for developing an ASTM standard test method for the geomembrane industry. Introduction In 1990, the author began experimenting with thermal welding of PVC geomembranes. The original motivation was to develop installation and welding methods that would extend the construction season in the cold northern climates of the USA.  Subsequent projects such as the Coachella Canal Underwater Lining Prototype clarified the need for a more rapid and faster curing method for welding PVC than the chemical or adhesive methods being used at the time.  With the advent of wedge welding of HDPE geomembranes, engineers became more comfortable with that method than extrusion welding.  Further refinement of the dual track process made it the method of choice for many QC firms.  In the mid 90’s thermal welding of PVC was somewhat of a novelty in the USA, but eventually caught on with installers.  Many used a single wedge machine and continued to use old fashioned air lance testing to verify seam integrity. During this period, welding equipment manufacturers also began developing smaller, lighter weight machines that were better suited for welding highly flexible materials like PVC.  Most of the wedge machines used a single wedge approximately one inch wide.  Hot air machines were introduced that used a wedge or a nozzle for producing single or double seams.  The authors began experimenting and developing procedures to dual track weld PVC so that air channel testing could also be done on PVC.   Early attempts with the heavier machines used on HDPE were less than desirable.  There were many difficulties making long seams in the flexible PVC.  Light weight hot air welders that could easily adjust nip roller pressure proved to be the solution for making high quality PVC seams. Continued experimentation with air channel testing on 30 mil PVC geomembrane projects produced mixed, but encouraging results.  Testing the air channel using methods similar to those used on HDPE was the starting point.  However, in the hot summer months, air channel testing flexible PVC at high ambient temperatures with the high air pressures required for the more rigid HDPE proved to be more damaging to good PVC seams than it did to find flaws.  Other ideas needed to be explored. Research In 2001 the PVC Geomembrane Institute funded basic research by TRI Environmental on the thermal welding temperature variables for PVC geomembrane.  This initial research lead to the conclusion that air channel testing of PVC geomembrane dual track welds could provide accurate information about the peel strength for the full length of the weld. This research was continued in early 2002 by TRI to find the optimum welding conditions for PVC and to further asses the author’s theory that air channel testing of PVC dual track welds could confirm the minimum peel strength of the weld and eliminate the need to cut any destructive samples. In order to provide the basic information, dual track hot air welding was used on 54 different PVC seam variations.  In order to establish the variable parameters, three different welding temperatures with three different welding speeds were selected.  These were performed on materials at three different ambient temperatures.  These 27 different combinations were used to weld 30 mil and 40 mil PVC geomembrane.  To further broaden the data base, the same variations were duplicated using hot wedge welding on 30 and 40 mil PVC, bring the total to 108 sample variations. Figure 1.)  PVC Air channel burst testing   Each seam was peel and shear tested in the laboratory according to ASTM D 6392 . Each seam was made long enough to allow air channel testing of each of these seam combinations to be conducted at three different ambient test temperatures.  This allowed for analysis of the effect of ambient temperature on each of the air channel tests for different weld variables.  Each seam section was tested until burst (Fig.1).  The results of the testing provided broad information about the effect of ambient sheet temperature on the air channel test as it relates to the peel strength of each weld.  Figure 2.) Effect of ambient sheet temperature on PVC seam peel strength. The data generated did not include low temperature tests, so a second battery of samples was prepared during the winter of 2003 to provide more accurate temperature requirements at ambient temperatures below 80ºF (27ºC).   When this data was included in the research, it became apparent that the relationship of ambient temperature and test pressure was linear rather than the curve in Fig. 2.  Further modifications of the test pressure/ambient temperature chart will be developed in the future. Case history The Georgia-Pacific paper mill in Parchment, MI was unable to obtain LLDPE geomembrane for a landfill closure project scheduled for installation in the late summer of 2002.  Engineers from Blasland Bouck & Lee (BB&L) were encouraged to consider using PVC geomembrane as a substitute for the 40 mil LLDPE textured both sides, and still meet all permit requirements.  Environmental Protection, Inc. (EPI) worked with BB&L and the Michigan Department of Environmental Quality to provide all the information necessary to revise the specifications and permit applications.  Revisions were made to the CQC/CQA plan to insure that all materials and welding methods would meet MI-DEQ permit requirements. Friction angle testing was conducted on 30 mil smooth PVC geomembrane samples with the soils encountered at the site.  Smooth PVC met all the factors of safety requirements for slope stability with the soils on this project.  There was no need to use a textured material because the smooth PVC soil interface friction angles were above the minimum requirements for the project. Figure 3.)  PVC Panel layout of Type III cell The project consisted of two cells.  The Type II cell was an ash fill requiring 55,000 M2 of 30 mil PVC liner.   The liner was placed directly on the fine, black ash material compacted on the 3/1 slopes of the cell.  The second area was a Type III waste cell that had been covered with two feet of sand material by Terra Contracting, LLC, the prime contractor on the project.  This cell required 130,000 M2 of PVC.  The PVC liner would also be placed directly on the sand layer already placed over the Type III waste on slopes varying from 5/1 up to 3/1 shown in the photo (Figure 4). Figure 4.)  Arial view of Type III cell PVC cap. The Type II cell required 32 panels to cover the 55,000 M2 (598,200 sq. ft.) footprint.  2,500 M (8,200 lineal ft.) of field seam was required to seal the panels together on the 3/1 slopes of the waste pile.  Installation and thermal welding of liner started in September, even before fabrication of all the material for the cell was completed.  The MI-DEQ requirements for weld testing for this project included trial welds from each machine at the start and end of each welding session.  That meant trial welds needed to be tested in shear and peel at start up in the morning, before shut down at mid day, at start up again after any break in welding (i.e. lunch), and finally again before shut down of the welder at the end of the day.  Only one sample for destructive testing of shear and peel strength would be removed for independent laboratory testing each day that welding was performed, no matter how much field seam was welded that day. All field seams were also to be non-destructively air channel tested (Fig. 5) according to established levels for air pressure and sheet temperature.  Based on research previously completed by EPI and the PGI, the installer was able to verify that peel strength exceeded the minimum requirement of 15 lb/in (2.6 kN/m) width for the full length of EVERY field seam. Figure 5.)  Inflated PVC air channel test The much larger Type III cell (Fig. 3 & 4) required 72 prefabricated panels to cover the 130,000 M2 (1,406,345 sq. ft.) waste pile.  The majority of the panels for both cells were 100 feet wide and 200 feet long. Over 7 km (23,000 lineal feet) of field seam were required to weld the panels together.  While 4+ miles of field welding may seem like a huge number, this is 70% less than would have been required with LLDPE.  Air channel testing of the dual track PVC welds also eliminated 75% of the destructive test sampling that would have been required on this project (>200 sample holes for polyethylene). Ambient temperatures during construction of the Type II cell cap varied from 65° - 92°F (18 - 33º C).  Sheet temperatures varied from 65° to 145° F (18-62º C) during welding operations. The Type III cell cap was constructed in October and ambient temps ranged from 82°F down to 36°F (28–2ºC). Sheet temperatures also varied greatly from a high of 120°F down to 36°F (49-2ºC).  Welder temperatures were set between 700° and 750°F (380 - 400ºC) and welder speeds ranged from 5 to 8 feet per minute (1.5–2.5 M/min), depending on sheet temperatures. There were no destructive test failures on this project. The combination of rigorous trial weld testing and air channel testing of every field seam resulted in confidence that every inch of seam exceeded minimum strength specifications.  There were also no air channel test failures due to below standard peel strength.  Air channel test failures were confined to holes in "T" seams where the loose flap of an intersecting field seam had not been trimmed properly. ASTM D 7177 standard test method In June 2003 EPI introduced the first draft of a standard specification for air channel testing of PVC thermal dual track welds based on the research completed and on actual field experience with welding and air channel testing large scale projects using PVC.  The process of ASTM peer review was completed in June of 2005 and ASTM D 7177 Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed  Sheet Temp ºC Sheet Temp ºF Air PressureKPa Air PressurePSI 4.5 40 414 60 7 45 386 56 10 50 358 52 13 55 324 47 15.5 60 290 42 18 65 276 40 21 70 248 36 24 75 234 34 26.5 80 200 29 29.5 85 186 27 32 90 172 25 35 95 165 24 37.5 100 152 22 40.5 105 138 20 43.5 110 131 19 Figure 6.)  Pressure required to verify 15 lb/in (2.6 kN/m) seam peel strength for PVC (per PGI-1104)   Geomembranes became a reality. This standard is now available for design engineers, owners and installers to accurately test PVC geomembrane seams. Conclusions Hot air welders have a distinct advantage with PVC in that they do not produce a buildup of burnt material on a wedge that can then scrape off and be deposited in the seam, causing inconsistencies in seam peel strength.  Overall weld quality is superior with hot air welders than with current wedge welder technology for PVC geomembranes. Air blowing from the nozzle into the seam from hot air welders also removes dirt, debris and moisture prior to melting the material, creating a more consistent weld in PVC. Air channel testing of PVC geomembranes has developed to the level that it is possible to verify the peel strength of 100% of the length of dual track welded PVC field seams.  This method also exposes failing portions of seams (no matter how small) that destructive testing does not identify.  When combined with an Electronic Leak Location Survey, it is now possible to test the strength of every cm of PVC field weld and every square cm of material. References ASTM D 7177 (2005). “Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes”, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA Thomas, Richard W. (2002). “Thermally Bonded PVC Seams”, Phase II - The Effects of Welding Speed, Welding Temperature, and Sheet Temperature on the Peel Strength and Burst Strength of 30 mil and 40 mil PVC Double-Track Fusion Seams. Thomas, Richard W., Stark, Timothy D., Choi, Hangseok, (2003). “Air channel testing of thermally bonded PVC seams”, Geosynthetics International Journal, Industrial Fabrics Association International, Vol. 10, No. 3, October 2003, pp 645-659 Stark, Timothy D., Choi, Hangseok, Thomas, Richard W. (2003). “Low temperature air channel testing of thermally bonded PVC geomembrane seams”, International Association of Geosynthetic Installers, Industrial Fabrics Association International, Vol. 4, Issue 1, Winter 2004, pp. 5-7. Thomas, Richard W., Stark, Timothy D. (2003). “Reduction of destructive tests for PVC seams”, Geotechnical Fabrics Report, Vol 21, No 2, March 2003 Rohe, Fred P., (EPI) 2004. “PVC geomembrane liner placement underwater in an operating irrigation canal”, Proceedings IGS Peru, November 2004 ASTM D 6392 (1999). “Standard Test Method for Determining the Geomembrane Seams Produced using Thermo-Fusion Methods”, American Society for Testing and Materials, Vol. 04.09, West Conshohocken, Pennsylvania, USA, pp. 1311-1315. PVC Geomembrane Institute (PGI), 2004. “PGI-1104 PVC Geomembrane Specification”, University of Illinois, Urbana, IL, January  2004.     For more information call   800-OK-LINER   today!

Thermal Welding Liners - How It Began In 1990 EPI began wedge welding PVC Geomembrane field seams. The original goal was to extend the liner construction season in Michigan by developing a welding technique for PVC that could be used in cooler weather. Geomembrane welding would allow earlier Spring start ups and delay shut down until late Fall. Wedge welders are hand-held devices that allow us to heat the two sides of the liner that we want to weld together to then press them and seal them. The material is sealed at the molecular level by the heat and compression. This new geomembrane welding technique is an excellent choice for many liner applications. Changing To Hot Air Welders After several years of experimentation and numerous consultations with equipment manufacturers, EPI made a wholesale change to hot air welders for welding PVC. We recieved considerable help from Bruno Zurmuhle of Leister and J.B. Budny from Heely-Brown Company . Developing the procedures for using hot air welders on thinner, more flexible PVC materials was a challenging task. But the problems were conquered and EPI welding technicians began to develop the skills to professionally weld PVC geomembrane in any thickness in almost any weather condition. Thermal Liner Welding - The Air Channel Test What evolved from these problem solving sessions and the reams of test data developed, was the absolute belief that the air channel test could be used to verify the physical strength of PVC liner welding. In 2001, TRI Environmental agreed to do some testing and research on PVC thermally welded seams. Rick Thomas also became intrigued that PVC seams could be tested for peel strength using an air channel test. In 2002 burst testing research was initiated on hot air and hot wedge welded PVC seams in 30 and 40 mil PVC. The result of this testing and other research was a graph of pressure vs. sheet temperature for air channel testing PVC geomembranes that verifies a minimum of 15 lb/in peel strength for the full length of the test section. This temperature and pressure correlation is necessary to correct the test to the same conditions required in the laboratory when peel testing PVC seams. In 2002, Mark Wolschon , Quality Control Manager of EPI, introduced to ASTM the idea of a standard air channel test for PVC. ASTM Committee D35 established an ASTM Task Group to develop a new standard. After over two years of extensive discussions, ASTM D7177 Standard Specification for Air Channel Evaluation of Polyvinyl Chloride (PVC) Dual Track Seamed Geomembranes was adopted by ASTM in 2005. ASTM D7177 is now the recognized standard for air channel testing of PVC field seams. Simply stated, poorly made thermal welds in PVC geomembrane peel open when subjected to air channel testing according to ASTM D7177 . This test stresses the entire length of the seam, so any weak areas no matter how small will be immediately located. Any failing seam should be replaced. EPI has also experienced field welds with passing destructive samples removed, failing an air channel test in a small area of the same seam. A seam of this type must be rewelded to insure the customer receives the best possible product.EPI has compiled qualitative test results and statistically analyzed the data. We have found through this process peel strength of the seams is generally stronger and the seams can be verified for conformance in minutes, rather than days, after production. Air channel testing is used for seam continuity as well as verifying peel strength for the entire length of the seam!   This histogram of field seam peel tests on 516 specimens of 30 and 40 Mil PVC shows that 80% of the results are between 20 and 45 pounds per inch width, with peek values as high as 55 lbs/in/width. This hot air dual track welding and testing method assures you that the PVC field seam strength will exceed all minimum quality standards.  "T" Seams ALL field seams must be tested and T-seams can be difficult to air channel test 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. We have had hundreds of questions from engineers and customers regarding the air channel testing of "T" seams, the seam created along the end of a PVC geomembrane panel. EPI air channel tests ALL field seams, including the seams along the ends of factory panels. While panels can be fabricated square, PVC panels are typically fabricated in rectangles, longer than they are wide. The panels are created using a large number of individual strips from rolls of PVC, welded together edge to edge. These edge welds terminate at the end of each panel and will overlap an adjacent panel when deployed in the field. This end panel overlap must be welded properly in order to air channel test the resulting weld. Specimen of EPI "T" Seam in 30 mil PVC 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 liner 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. EPI factory seams have no loose edge, so the process for welding T-seams is relatively easy. Slowing the welding machine's rate of travel will allow the melted PVC material to flow together at the junction of the three layers of material, providing the necessary seal and weld strength. For fabricators who leave 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.   For more information call   800-OK-LINER  today!

Bentomat® Geosynthetic Clay Liner General Installation Guidelines SURFACE AND SUBGRADE PREPARATION The subgrade or fill material should be free of any angular or sharp rocks larger than 2 inches (5 cm) in diameter as well as any organics or other deleterious materials. Compaction of the subgrade should be in accordance with the design specifications, or, at a minimum, to the extent that no rutting is caused by installation equipment or vehicles. Prior to deployment of the BENTOMAT geosynthetic clay liner, the subgrade should be final graded to fill all major voids or cracks and proof rolled to provide a smooth surface for the installation of the liner. The surfaces to be lined should be smooth and free of debris, roots and angular or sharp rocks larger than 1 inch (2.5 cm) in diameter. Minor variations in the subgrade surface are tolerable; however, no sharp irregularities should exist.  Installations over other geosynthetic materials requires no additional surface preparation. BENTOMAT HANDLING AND PLACEMENT Depending on the type of subgrade at the site, the typical equipment used for deployment may range from an extendible boom forklift to a front end loader or backhoe. Suspending the BENTOMAT roll using a spreader bar and a core pipe through the core will facilitate deployment and will prevent damage to the panel edges caused by the suspending chains or straps. Flat-bladed vise-type grips may be used by laborers for handling, but are not required. BENTOMAT may be cut with a sharp utility knife, scissors, or with a battery-powered rotating blade cutter. Panels of BENTOMAT should be installed with the white nonwoven surface facing down in order to maximize friction against the subgrade. BENTOMAT rolls are wound at the plant so that they naturally unroll with this orientation. Methods of deployment will vary based on site-specific conditions such as slope angle, berm widths, the type of project, the type of subgrade surface, and the subgrade preparation. As a general guideline, all seams should run parallel to the direction of the slope. Flat areas require no particular orientation; however, attention should be paid to the overlap orientation to prevent seam displacement during cover placement. Deployment should proceed from the highest elevation to the lowest to facilitate drainage in the event of precipitation. BENTOMAT may be deployed by pulling the material from a suspended roll, or by weighing down one end of the roll end and then allowing it to unroll as the installation equipment slowly moves backwards along the intended path of deployment. SEAMING PROCEDURES BENTOMAT seams are formed with a Volclay sodium bentonite enhanced overlap. BENTOMAT has been engineered so that when properly installed and hydrated, a small amount of internal sodium bentonite will extrude through the edges where overlaps exist; however, secondary seaming measures are also recommended to insure that a continuous seal is achieved between panels. A minimum of a 6-inch to 9-inch overlap should exist at all seam locations. A lap line as well as a match line have been printed on the BENTOMAT panel edges at 6 and 9 inches respectively, to ensure the proper overlap is achieved. The BENTOMAT panels should be adjusted to smooth out any wrinkles or creases between adjacent panels, leaving a proper seam where the overlapping panel covers the lapline of the underlying panel but leaves the matchline exposed. Any native soil and debris should be removed from the contacting BENTOMAT surfaces to ensure seam integrity. The overlapping panel edge should be pulled back and granular Volclay sodium bentonite similar to that used in the BENTOMAT itself should be poured continuously along all seams and lap areas from the panel edge to the 6-inch lapline, at a minimum application rate of one-quarter pound per lineal foot (one bag per roll of GCL). Granular bentonite is supplied with each shipment of BENTOMAT for these purposes and for other detail work as required. ANCHORING PROCEDURES Anchor trenches may be excavated in a number of ways, depending upon the size of the project and the maneuvering area available at the top of the slope. The preferred methods are to use a ditch trencher (set to the specified depth) or a small backhoe equipped with a bucket of appropriate width. Bentomat should be placed in the trench such that the end of the panel covers the entire trench floor but does not extend up the rear wall. The size of the anchor trench depends on site-specific criteria such as the soil type and general condition, the angle and length of the slope, as well as the thickness and type of proposed cover materials. In any case, anchor trench backfill should be well compacted to prevent water intrusion or pending and to prevent liner pullout. When using BENTOMAT in conjunction with other geosynthetic materials, the BENTOMAT may be put in a separate trench or placed as otherwise specified by the engineer. PENETRATION SEALING For sealing around penetrations, a small notch should be made around the circumference of the pipe, into the subgrade. Volclay bentonite should then be packed around the pipe in the notch and on adjacent areas so that the pipe is encased by a pure bentonite seal. The BENTOMAT panel should then be placed over the penetration and slit into a "pie" configuration where the pipe is to protrude. This procedure will create a snug fit between the BENTOMAT and the pipe once the laps are trimmed. More sodium bentonite should then be spread around the cut edges of the BENTOMAT against the pipe and over adjacent areas. To complete the detail, a collar of BENTOMAT should be cut in a manner similar to that made on the main panel and fit around the pipe, with additional Volclay sodium bentonite applied into any gaps that may remain. When Bentomat is used above or in conjunction with other geosynthetic materials, notching below the liner may not be possible. In these cases, sprayable bituminous coatings may be applied around the penetrations and any other critical areas. All other penetration sealing steps should be followed to ensure a watertight seal is produced. STRUCTURE SEALING Another critical area in an installation is the attachment or sealing of BENTOMAT to foundation walls, drainage outlets or concrete structures. Sealing panel edges against a wall or foundation is accomplished with the use of pure Volclay bentonite. To start, a small notch should be made against the edge of the object to be sealed. The notch should be packed full of Volclay bentonite. The BENTOMAT panel is then brought up to the structure and trimmed to fit against the wall of the structure as shown. Care must taken to ensure that the Bentomat is kept directly against the structure as the cover material is applied. Once hydrated, the Volclay bentonite seal will allow for settlement or other stresses that may tend to pull the BENTOMAT from the edge. PROTECTIVE COVER The protective cover should be composed of well graded soils, sands or crushed gravel free of sharp edged stones larger than 1 inch (2.5 cm) in diameter. Cover should be spread by low ground pressure equipment. A minimum cover thickness of 12 inches should be kept between heavy equipment and the liner at all times. No vehicles should drive on the BENTOMAT until proper cover has been placed to the specified depth. Once the proper depth of cover soils have been applied, compaction equipment may be used. Care should be taken to push materials upslope wherever possible and to avoid pinching or shifting the liner by making sharp turns or sudden stops. DAMAGE Rips or tears may be repaired by completely exposing the affected area, removing all foreign objects or soil, and by then placing a patch over the damage, with a minimum overlap of 12 inches on all edges. Accessory bentonite should be placed between the patch and the repaired material at a rate of a quarter pound per lineal foot of edge spread in a six-inch width. If damage occurs on a slope, the same basic procedure should be used; however, the edges of the patch should be fastened to the repaired liner with contact cement, epoxy, or some other construction adhesive, in addition to the bentonite-enhanced seam. ACTIVATION For fresh water applications, the water to be contained will activate the BENTOMAT. If highly contaminated or non-aqueous liquids are to be contained, however, the BENTOMAT must be prehydrated with fresh water for 48 hours prior to use. Approximately one-quarter gallon of fresh water per square foot is necessary for prehydration. Prehydration may be accomplished by flooding the impoundment, using a sprinkler system, or by natural rainfall. In landfill applications, the leachate is typically sufficient to hydrate the BENTOMAT. MAINTENANCE No regular maintenance of Bentomat is necessary under normal operational conditions. Should damage occur to the liner, the damage repair guidelines should be followed. Should unusual conditions exist or should the normal repair procedure not be possible, contact CETCO for further recommendations.    For more information call   800-OK-LINER  today!

Flap vents are installed at the crest of the slope to allow for venting of air or gas trapped under the liner during the covering operation. Once the liner has been completely covered, these vents serve no further purpose . Landfill covers require venting to relieve gas pressure under the liner.  This detail shows a typical gas vent utilizing perforated and solid PVC pipe.     For more information call   800-OK-LINER   today!

How Temperature Impacts Geomembranes  Geomembranes are known to be ideal for protecting the environment based upon their durability, flexibility, and resistance to chemical and temperature changes. Geomembranes are designed to be thermally stable and resistant.  Temperature can have various impacts on the properties and performance of geomembrane liners. It is important to consider the various impacts when deciding the type of liner right for your project site and environment, along with the manufacturing of the liner.  Here are 5 impacts temperature can have on geomembranes:  Mechanical Performance: Temperature variations can influence the mechanical properties and performance of geomembranes. High temperatures can cause geomembranes to soften, which can result in reduced tensile strength and tear resistance. This can result in punctures, tears, and even damage to the liner. Low temperatures can also affect geomembrane performance. Low temperatures can cause geomembranes to become brittle and stiff, causing liners to crack or tear.  Geomembrane Shape: Geomembranes can expand or contract with temperature variations. High temperatures will cause the liner to expand, while low temperatures may cause the liner to contract. This movement may affect the overall dimensions and shape of the geomembrane liner.  Seam Integrity: Geomembranes are often installed by heat welding or fusion techniques. Temperature variations can affect seam integrity. High temperatures may soften the seams, making them susceptible to deformations or failures. Low temperatures can make the seams rigid, increasing the risk of cracking or separating.   Chemical Resistance: Temperature variations can influence the chemical resistance of geomembranes. Chemicals and solvents may have different properties at different temperatures and some liners may experience changes in their resistance to specific chemicals and solvents at different temperature ranges.  Long-Term Durability: Temperature fluctuations over time can impact the long-term durability on geomembranes. Repeated exposure to temperature extremes may accelerate the degradation of geomembrane liners.  Although temperature variations may affect your geomembrane liner durability and performance, the experts at EPI can mitigate these effects.  The designers and manufacturers we use at EPI use materials specifically formulated to withstand extreme temperature conditions. Liners can not only be designed to withstand various weather conditions, but also to withstand high heat applications like power plants.  Our experts will advise you on the best geomembranes for your project and environment. They will assist in the entire process start to finish, ensuring the proper installation techniques and regular inspections are being done. This will help identify and address any temperature-related issues early on, maintain the effectiveness and longevity of the geomembrane system.   EPI is a leading provider of high-quality geomembrane solutions and tailor’s its manufacturing to your project’s unique requirements. Contact us today to discuss your needs and let our experts guide you through the process.