a landfill is just a large bag of trash that drips into your drinking water.
and we all know that brown smelly drippy goo is NOT tasty.
this is why i throw my trash out the window.
DECADE-OLD STUDY REVEALED THE POLLUTING EFFECTS OF LANDFILLS.
A careful study of 50 landfills in 1977 concluded that 43 out of 50 (86%) had contaminated underground water supplies beyond the boundaries of the landfill. At the other 7 sites, off-site contamination was measured but could not be attributed to the landfills by the strict criteria used in the study. In other words, the study of 50 landfills found groundwater pollution at all 50 sites, but the contamination could be definitely traced to the landfills in only 43 cases (86%).
The study was conducted by Geraghty & Miller of Port Washington, NY, one of the nation's leading hydrology consulting firms, under contract to EPA (U.S. Environmental Protection Agency). They looked at 122 sites in 15 states and finally selected 50 sites in 11 states for careful evaluation. They studied 7 in Wisconsin, 6 in Illinois, 5 in Indiana, 5 in Michigan, 2 in Pennsylvania, 5 in New York, 9 in New Jersey, 3 in Connecticut, 5 in Massachusetts, 2 in New Hampshire, and 1 in Florida.
Criteria for selecting sites were strict: no site was selected if it was already known to be contaminated or if there were reports of bad taste or bad odors from drinking water near the site already; sites were selected to include various geologic settings (various rock and soil types) and various climatic conditions; sites were selected to include different kinds of dumping (landfills and lagoons), and different kinds of wastes. Some of the wastes would be termed "hazardous" today, but many of the wastes involved were not "hazardous" by today's legal definitions and are still allowed in municipal landfills today. Sites had to be at least 3 years old.
The criteria for determining whether a site was contaminating groundwater were strict. (1) Contaminants had to be measured in groundwater beyond the perimeter of the site; (2) the concentration of contaminants downstream of the site had to be greater than the concentration of the same contaminants measured in an uncontaminated background well; (3) all wells used had to be tapping the same aquifer; (4) geologic interpretation of the data by hydrologists had to convince them that the landfills was the source of the contamination.
In 43 out of 50 cases, the landfill was confirmed as the source of contamination. In four other cases, contamination was confirmed, but the area of contamination was so great that sources besides the landfill were also suspected; at three more sites, contamination was found but data could not be gathered from uncontaminated background wells. So contamination was confirmed at all 50 sites, but in 7 cases, the project's criteria could not be met for deciding that the landfill was the culprit.
The term "landfill" was used to mean a dumping ground that accepted garbage, demolition debris, municipal and industrial solid wastes, sludges or liquids. The investigation "concentrated on those landfills with a major component of industrial waste."
Some of the landfills had liners, others did not. Since publishing this study, the EPA has published its opinion several times, that all landfill liners will eventually leak. (See HWN #37.) Thus this study provides important evidence that all landfills, lined or not, all eventually contaminate groundwater. Lined landfills will contaminate groundwater more slowly than unlined landfills, but the long-term effects will be the same: someone's groundwater will become contaminated whenever municipal solid waste or industrial waste or legally hazardous wastes are placed in the ground.
The study makes some interesting points worth remembering about landfills: "The intermixing of inorganic and organic wastes, wastes of high and low pH, and wastes having different physical properties in a common disposal area, may lead to influences on the environment not anticipated from any single waste material." (pg. 7) This is important because landfill liners are selected to be compatible with the wastes that will be placed in a landfill. However, as this statement says, the mixing of wastes in a landfill will produced unanticipated chemical combinations with unpredictable results. A landfill liner selected to withstand attack from chemicals X, Y and Z may not withstand attack from chemicals X and Z in combination, or Y and Z in combination. The more chemicals involved, the greater the number of possible combinations, the more complex the interactions will be, and the less predictable the results become.
The study makes another valuable point: "The wastes that are deposited continue to weather and leach for years." (pg. 8) The chemical interactions within a landfill do not cease when the dumping stops. In the case of inorganic materials (arsenic, lead, chromium and so forth) the duration of the hazard is essentially infinite--toxic metals will never change into anything besides toxic metals. (The Geraghty & Miller study found toxic heavy metals at 49 of the 50 sites and found they contaminated groundwater off-site at 40 of the 50 sites.)
When anyone proposes a new landfill and says that liners are being selected to prevent contamination of the environment, you should ask, (a) How can they possibly predict all the possible combinations of chemicals that will be created inside the landfill, producing new combinations of chemicals that will attack the liners?; and (b) What is the expected duration of the hazard inside the landfill vs. the expected duration of the liners that have been selected?
If the proponents of a landfill project are honest, these questions will force them to admit that they are not able to predict the chemicals that will come in contact with the liner (especially since the chemicals used by industry change from year to year, and an average of 1000 new chemicals go into commercial use each year); and they will be forced to admit that the duration of the hazard (in the case of metals at least) is very great (thousands of years or longer) whereas the expected lifetime of any human-created material (including packed clay liners and all FMLs [flexible membrane liners]) is much shorter than the expected hazard. Leakage is inevitable.
Common sense and available data combine to force a single conclusion: all landfills will eventually leak. Landfill liners may SLOW the release of contaminants into groundwater but they cannot PREVENT it. There is no such thing as a secure landfill.
WHAT IS A LANDFILL?
A secure landfill is a carefully engineered depression in the ground (or built on top of the ground, resembling a football stadium) into which wastes are put. The aim is to avoid any hydraulic [water-related] connection between the wastes and the surrounding environment, particularly groundwater. Basically, a landfill is a bathtub in the ground; a double-lined landfill is one bathtub inside another. Bathtubs leak two ways: out the bottom or over the top.
WHAT IS THE COMPOSITION OF A LANDFILL?
THE NATURAL HYDROGEOLOGIC SETTING:
WHAT IS A BOTTOM LINER?
WHAT IS WRONG WITH A CLAY LINER?
WHAT IS WRONG WITH A PLASTIC LINER?
WHAT IS WRONG WITH COMPOSITE LINERS?
A Composite liner is a single liner made of two parts, a plastic liner and compacted soil (usually clay soil). Reports show that all plastic liners (also called Flexible Membrane Liners, or FMLs) will have some leaks. It is important to realize that all materials used as liners are at least slightly permeable to liquids or gases and a certain amount of permeation through liners should be expected. Additional leakage results from defects such as cracks, holes, and faulty seams. Studies show that a 10-acre landfill will have a leak rate somewhere between 0.2 and 10 gallons per day.
WHAT IS A LEACHATE COLLECTION SYSTEM?
WHAT ARE SOME OF THE PROBLEMS WITH LEACHATE COLLECTION SYSTEMS?
they clog up from silt or mud;
they can clog up because of growth of microorganisms in the pipes;
they can clog up because of a chemical reaction leading to the precipitation of minerals in the pipes; or
the pipes become weakened by chemical attack (acids, solvents, oxidizing agents, or corrosion) and may then be crushed by the tons of garbage piled on them.
WHAT IS A COVER?
WHAT ARE THE PROBLEMS WITH COVERS?
Erosion by natural weathering (rain, hail, snow, freeze-thaw cycles, and wind)
Vegetation, such as shrubs and trees that continually compete with grasses for available space, sending down roots that will relentlessly seek to penetrate the cover;
Burrowing or soil- dwelling mammals (woodchucks, mice, moles, voles), reptiles (snakes, tortoises), insects (ants, beetles), and worms will present constant threats to the integrity of the cover;
Sunlight (if any of these other natural agents should succeed in uncovering a portion of the umbrella) will dry out clay (permitting cracks to develop), or destroy membrane liners through the action of ultraviolet radiation;
Subsidence--an uneven cave-in of the cap caused by settling of wastes or organic decay of wastes, or by loss of liquids from landfilled drums--can result in cracks in clay or tears in membrane liners, or result in ponding on the surface, which can make a clay cap mushy or can subject the cap to freeze-thaw pressures;
Rubber tires, which "float" upward in a landfill; and
Human activities of many kinds.
LEACHATE FROM MUNICIPAL DUMPS HAS SAME TOXICITY AS LEACHATE FROM HAZARDOUS WASTE DUMPS.
In a new study, researchers at Texas A&M University have compared leachate from municipal landfills with leachate from hazardous waste landfills and they report, "...There is ample evidence that the municipal waste landfill leachates contain toxic chemicals in sufficient concentration to be potentially as harmful as leachate from industrial waste landfills." Specifically, the Texas researchers compared leachate from several municipal landfills with leachate from the notorious Love Canal landfill (and other hazardous waste landfills, such as Kin-Buc in Edison, NJ) and they found the leachates similar in their cancer-causing potential.
Leachate is the liquid that is produced when rain falls on a landfill, sinks into the wastes, and picks up chemicals as it seeps downward. Industries creating "hazardous wastes" (as legally defined under federal law) may not send those wastes to municipal landfills, but must instead send them to special hazardous waste landfills.
When a new municipal landfill is proposed, advocates of the project always emphasize that "no hazardous wastes will enter this landfill." The Texas study shows that even though municipal landfills may not legally receive "hazardous" wastes, the leachate they produce is as dangerous as the leachate from hazardous waste landfills.
Dr. Kirk Brown and Dr. K.C. Donnelly at Texas A&M, authors of the new study, examined data on the composition of leachate from 58 landfills. The data they reviewed showed 113 different toxic chemicals in leachate from municipal landfills and 72 toxic chemicals in leachate from hazardous waste landfills. The abundance of toxics in municipal landfills probably occurs because the entire spectrum of consumer products ends up in municipal landfills, whereas hazardous waste landfills serve a limited number of industries within a region.
The actual source of the toxic chemicals in municipal landfills is not known precisely. Under federal law (RCRA Subtitle C) each "small quantity generator" can send up to 2640 pounds per year of legally-hazardous chemicals to municipal landfills. In 1980, the EPA [U.S. Environmental Protection Agency] estimated that 600,000 tons per year of legally-hazardous wastes were going to municipal dumps from 695,000 "small quantity generators."
Illegal dumping may be another source; illegal dumping is impossible to prevent entirely because someone bringing in a truckload of wastes may hide a few gallons, or a few barrels, of hazardous chemicals in the middle of the truckload. The higher the price of legal disposal, the more incentive people have to dump illegally. However, the most likely source of most of the toxic materials in municipal landfills is legally-disposed household products like paint solvents, oils, cleaning compounds, degreasing compounds, and pesticides. "In addition, the final depository of most of the products of our modern industrial society is the municipal waste landfill where the paints, plastics, and pharmaceuticals dissolve and degrade in the acidic anaerobic [oxygen-free] environment, thereby, releasing degradation products which may be even more toxic than the products from which they originated," say Brown and Donnelly.
The findings of Brown and Donnelly will come as no surprise to many researchers who have known for years that municipal leachate is as toxic as the leachate from industrial landfills. For example, in an article entitled, "APPLICATION OF HYDROGEOLOGY TO THE SELECTION OF REFUSE DISPOSAL SITES," Ronald A. Landon reported in 1969 in the JOURNAL OF GROUND WATER, Vol. 7 (Nov.-Dec., 1969), pgs. 9-13, that "Leachate at its source, that is within the landfill, has concentrations and characteristics of many industrial wastes; and in many instances would be better treated as such a waste." (pg. 12)
What Brown and Donnelly have contributed is a quantitative analysis of the toxicity and the carcinogenic potential of leachates from the two types of landfills.
Brown and Donnelly conclude, "The risk calculations based on suspect carcinogens... indicate that the estimated carcinogenic potency for the leachate from some municipal landfills may be similar to the carcinogenic potency of the leachate from the Love Canal landfill."
In industrial landfill leachate, 32 chemicals cause cancer; 10 cause birth defects, and 21 cause genetic damage; in municipal landfill leachate, 32 chemicals cause cancer, 13 cause birth defects, and 22 cause genetic damage.
The new study, "An Estimation of the Risk Associated with the Organic Constituents of Hazardous and Municipal Waste Landfill Leachates," appears in the journal, HAZARDOUS WASTES AND HAZARDOUS MATERIALS, Vol. 5, No. 1 (Spring, 1988), pgs. 1-30. Request a free reprint from Dr. Kirk Brown, Soil and Crop Sciences Department, Texas A&M University, College Station, TX 77843. Phone (409) 845-5201.
--Peter Montague, Ph.D.
Descriptor terms: leachate; leaks; toxicity; hazardous waste industry; msw; texas a&m; landfilling; cancer; love canal; kin-buc landfill; studies; findings; household hazardous wastes; kirk brown; k.c. donnelly; rcra; epa; illegal dumping; haulers; risk assessment; birth defects; developmental disorders.
LEACHATE COLLECTION SYSTEMS: THE ACHILLES' HEEL OF LANDFILLS.
A landfill is a bathtub in the ground, and a bathtub can leak two ways: it can leak through a hole in the bottom (failure of its bottom liner), or it can fill up with fluid and spill over its sides. Either way, it's bad news. The basic problem is the fluid. If a landfill begins to fill up with fluid, the weight of the fluid puts pressure on the bottom of the landfill, increasing the likelihood of bottom liner failure, so any fluid inside a landfill is a potential source of trouble.
To prevent fluid from causing problems, every modern landfill has a system for draining liquids out of the landfill. This is called a leachate collection system. What is leachate? Think of a landfill as being like a drip coffee maker. The dry coffee is the garbage, the water you pour in the top is rainwater, and the dark, brewed coffee dripping out the bottom is leachate. You might want to drink coffee, but you definitely do not want to drink leachate: it has many toxic and dangerous characteristics. It is badly polluted with chemicals and with micro-organisms (bacteria and viruses) that would make you sick.
The picture below represents a closed landfill; the heavy dark line represents the plastic baggie (bottom liner and top cover) that is supposed to keep leachate from entering the environment. The round circles between the two bottom liners represent collection pipes which have many holes drilled along their length (making these pipes resemble a swiss cheese); they are supposed to collect any leachate that flows to the bottom of the landfill. In theory, these pipes carry off the leachate to a wastewater treatment plant, where the leachate is processed to remove the toxic chemicals. (At the wastewater treatment plant, some of the chemicals are released into the air, and the remaining ones are collected [they're now in a mud-like sludge] and they are sent to another landfill somewhere.)
One of the least-studied aspects of landfill design is how to make a leachate collection system that will work for many decades (much less many hundreds of years). The fact is, leachate collection systems can clog up in less than a decade and, when that happens, fluids begin to build up inside the landfill--a dangerous situation, as we have noted above.
Leachate collection systems fail in several known ways. First, they can clog up from silt or mud. Second, they can clog up because of the growth of microorganisms in the pipes. Third, they can clog because of a chemical reaction leading to the precipitation of minerals in the pipes; anyone who has boiled a pot of "hard" water and seen the whitish crusty residue in the bottom of the pot knows what "precipitated chemicals" look like. Fourth, the pipes themselves can be weakened by chemical attack (acids, solvents, oxidizing agents, or corrosion) and may then be crushed by the tons of garbage piled above them.
The book, AVOIDING FAILURE OF LEACHATE COLLECTION AND CAP DRAINAGE SYSTEMS, by Jeffrey Bass, discusses these four failure mechanisms. The first problem (silt) can sometimes be avoided, or at least reduced, by installing a "filter layer" above the leachate collection system. The filter layer may be made up of gravel or of a rug-like plastic material called "geotextile." Since the oldest leachate collection systems date from the early 1970s, humans have very little experience with the long-term performance of leachate collection systems. The hope is that a "filter layer" will solve the siltclogging problem, but after many decades the entire filter layer itself may clog. Only time will tell.
The growth of microorganisms seems to be an uncontrollable problem. The conditions for growth of slime-forming microorganisms are not well understood. Even if they were understood, we could not control chemical and physical conditions (temperature, pH, etc.) at the bottom of a landfill because of the thousands of tons of wastes heaped up in the landfill.
The problem of chemical precipitation also appears to be uncontrollable. The chemical conditions that lead to precipitation may be knowable, but again the conditions in the leachate collection system cannot be controlled because the system is not accessible once wastes have begun to be dumped into the landfill.
The last problem--chemical attack on the leachate collection pipes, leading to destruction of the pipes themselves--also appears to be an unsolvable problem. Mr. Bass suggests, in best ivory tower fashion, that the way to control chemical attack on the pipes is to select pipes that are resistant to the chemicals that you know will make their way into the landfill. In principal, this is a good idea. But in the real world, how do you know what's going to be put into your landfill next week? Next year? With 1000 brand new chemicals being put into commercial use each year, over the next 10 years, today's leachate collection pipes may come into contact with 10,000 new chemicals that don't even exist today. Any of those chemicals may attack the pipes. In addition, chemicals mixing together inside a landfill will create new chemical combinations that may produce heat or may otherwise attack the pipes.
Mr. Bass's book is misnamed because it seems to suggest that the failure of leachate collection systems can be avoided. However, as the text of Mr. Bass's book makes abundantly clear, if such failures were to be avoided, it would be by dumb luck, not by engineering design. Only a fool trusts dumb luck.
EPA SAYS ALL LANDFILLS LEAK, EVEN THOSE USING BEST AVAILABLE LINERS
People who are enthusiastic about garbage incinerators often fail to mention that every incinerator has a landfill associated with it. The ash left over from incineration needs to be landfilled, and the ash is toxic. Some engineers (especially those employed to promote garbage incinerators) try to argue that the toxic constituents of the ash will remain safely in the landfill "forever." But this is a flawed view: the weight of evidence and opinion in the technical world does not agree with this argument. On the contrary, even the U.S. Environmental Protection Agency says that all landfills will leak. The agency has published this opinion on many occasions in the FEDERAL REGISTER. But before we look at the EPA's reasons for believing all landfills will leak, let's look at the way landfills are constructed:
A landfill is a carefully-engineered depression in the ground (or built on top of the ground, resembling a football stadium) into which wastes are put. The intention is to avoid any hydraulic [water-related] connection between the wastes and the natural environment. To achieve this goal, there are four important parts of all landfills: a bottom liner, a leachate collection system, a cover, and the natural hydrogeologic setting (the earth).
The hydrogeologic setting can be selected to slow the entry of wastes into the natural environment. The other three components must be engineered. The bottom liner can be one or more layers of clay or a synthetic flexible membrane liner [FML], for example, a sheet of plastic; the liner effectively creates a bathtub in the ground. The leachate collection system consists of sloping the sides of the landfill and putting pipes in the lowest places, to pump out contaminated water and other fluids (leachate) as they accumulate; the pumped leachate is treated at a wastewater treatment plant (and the solids removed from the leachate during this step are returned to the landfill, or are sent to some other landfill). The cover or cap will consist of several sloped layers of clay or FML (to prevent rain from intruding), overlain by a very permeable layer of sandy or gravely soil, overlain by topsoil in which vegetation can root (to stabilize the underlying layers of the cap).
Each of these components is critical to success. If the bottom liner fails, wastes will migrate directly into the environment. If leachate collection pipes clog up and leachate remains in the landfill, fluids can build up in the bathtub; the resulting liquid pressure becomes the main force driving waste out the bottom of the landfill when the bottom liner fails. If the cover (cap) is not maintained, rain will enter the landfill, resulting in buildup of leachate to the point where the bathtub overflows its sides and wastes enter the environment.
In the FEDERAL REGISTER Feb. 5, 1981, the EPA first stated its opinion that all landfills will eventually leak:
"There is good theoretical and empirical evidence that the hazardous constituents that are placed in land disposal facilities very likely will migrate from the facility into the broader environment. This may occur several years, even many decades, after placement of the waste in the facility, but data and scientific prediction indicate that, in most cases, even with the application of best available land disposal technology, it will occur eventually." [pg. 11128]
"Manmade permeable materials that might be used for liners or covers (e.g., membrane liners or other materials) are subject to eventual deterioration, and although this might not occur for 10, 20 or more years, it eventually occurs and, when it does, leachate will migrate out of the facility." [pg. 11128]
"Unfortunately, at the present time, it is not technologically and institutionally possible to contain wastes and constituents forever or for the long time periods that may be necessary to allow adequate degradation to be achieved." [pg. 11129]
"Consequently, the regulation of hazardous waste land disposal facilities must proceed from the assumption that migration of hazardous wastes and their constituents and by-products from a land disposal facility will inevitably occur." [pg. 11129]
More than a year later, on July 26, 1982, the EPA again put its opinions into the FEDERAL REGISTER, emphasizing that all landfills will inevitably leak:
"A liner is a barrier technology that prevents or greatly restricts migration of liquids into the ground. No liner, however, can keep all liquids out of the ground for all time. Eventually liners will either degrade, tear, or crack and will allow liquids to migrate out of the unit." [pg. 32284]
"Some have argued that liners are devices that provide a perpetual seal against any migration from a waste management unit. EPA has concluded that the more reasonable assumption, based on what is known about the pressures placed on liners over time, is that any liner will begin to leak eventually." [pgs. 32284-32285].
In the FEDERAL REGISTER May 26, 1981, pgs. 28314 through 28328), the EPA argued forcefully that all landfills will eventually leak. Another EPA quote:
"Many organic constituents are stable (degrade very slowly); other hazardous constituents (e.g., toxic metals) never degrade. Yet the existing technology for disposing of hazardous wastes on or in the land cannot confidently isolate these wastes from the environment forever.
"Since disposing of hazardous wastes in or on the land inevitable [inevitably?] results in the release of hazardous constituents to the environment at some time, any land disposal facility creates some risk." [pg. 28315]
EPA went on to estimate that the duration of the hazard from a landfill would be "many thousands of years." [pg. 28315] And the Agency said, "The longer one wishes to contain waste, the more difficult the task becomes. Synthetic liners and caps will degrade; soil liners and caps may erode and crack. ...EPA is not aware of any field data showing successful long-term containment of waste at facilities which have not been maintained over time." [pg. 28324]
"Ultimately, waste reduction and resource recovery probably provide the best alternative to land disposal," said the EPA [pg. 28325], though it has never begun any programs to make this happen.
--Peter Montague, Ph.D.
Descriptor terms: ash; epa; landfills; soil; leachate; hazardous wastes; land; land disposal; metals; water pollution.
ANALYZING WHY ALL LANDFILLS LEAK.
The U.S. Environmental Protection Agency (EPA) has paid for a series of engineering studies to find out the best way to make a landfill. They wanted to know what was the "best demonstrated available technology" (BDAT) for making landfills. These studies reach some surprising conclusions.
Landfills are bathtubs in the ground; the bottom of the bathtub is called a liner and it can be made of compacted clay soil, or it can be made of a huge sheet of plastic underlain by ordinary soil, or it can be a huge sheet of plastic underlain by a layer of compacted soil (usually clay soil). The third combination, plastic liner and compacted soil, is called a "composite liner." (A composite liner is not a double liner; it is a single liner made up of two parts; to create a double liner, you would use two composite liners together, separated by a layer of sand or gravel.) Geoservices did not examine the second type of liner (plastic sheet on ordinary soil) because ordinary soil provides poor support for a plastic liner carrying many tons of weight, so they restricted their analysis to compacted clay liners vs. composite liners.
The EPA wanted to know which liners were the best ones available: compacted clay liners, or composite soil liners? So they hired Geoservices (of Boyton, Florida) to tell them. The resulting study makes dull reading because it is filled with technical details, but the conclusions are fascinating. All liners perform worse than anyone suspected.
Geoservices didn't have much good to say about clay liners. The flow of liquids through a liner (the liner's permeability) is measured in centimeters per second (cm/s). The EPA's current requirement for a liner for a hazardous waste landfill is that it pass liquids through it no faster than 10-7 cm/s (read ten to the minus seven centimeters per second, or one ten millionth of a centimeter per second). However, based on actual experience in the field, Geoser vices concludes that this ideal permeability is often not achieved for a variety of reasons. (See pgs. 3-3 through 3-8; case studies of clay liners appear in Appendix A.) Therefore, they assume that the actual permeability in the real world lies between 10-7 and 10-6 cm/s. Geoservices concludes, "Possibly the most significant observation is that with compacted [clay] soil bottom liners, leakage out of the [landfill] will be large (if there is leakage through the top liner).... even in [landfills] meeting current EPA design requirements" including permeability of 10-7 cm/s (pg. 3-18). By "large" leakage, Geoservices means 90 gallons of fluid leaking through each acre each day, or 900 gallons per day leaking from a 10-acre landfill. Their calculations show that, with 3 inches of water standing on the bottom liner, it will take 15 years for leakage to break through a 3-foot-thick compacted clay bottom liner, but once breakthrough has occurred, 90 gallons per acre per day will pass through the liner continuously thereafter. (See pg. 3-16, and Table 3-3 on pg. 3-40.) It won't take very long to contaminate a large drinking water supply if you pour 90 to 900 gallons of toxics into it day after day, year after year. Thus Geoservices has shown that clay liners are an environmental disaster.
Geoservices reports that all plastic liners (also called Flexible Membrane Liners, or FMLs) always have some leaks. "A common misconception regarding FMLs is that they are impermeable, that is, no fluid will pass through an intact FML. However, it is important to realize that all materials used as liners are at least slightly permeable to liquids or gases and a certain amount of permeation through liners should be expected. Additional leakage results from defects such as cracks, holes, and faulty seams." (pg. 4-2)
FMLs often develop defects called "pinholes" during manufacture; these result from thin places ("fish eyes"), bubbles, foreign material, or lumps of carbon in the raw molten plastic from which the FML is rolled ("calendered") into sheets. Furthermore, when a large landfill liner is created by joining strips of FML together with glue or by welding, the resulting seams often leak. Geoservices provides some data on typical seam defect rates. They look at six case studies (pgs. B-7 thru B-11). Based on the six case studies, they draw the following "tentative conclusions:" an average of one leak per 30 feet of seam can be expected if there is no quality assurance program (quality assurance being a third party coming along behind with special equipment to check the adequacy of the seams). Even with good quality assurance, "an average of one leak per 1000 feet of seam can be expected with reasonably good installation, adequate quality assurance, and repair of noted defects." (pg. B-11) That is to say, under the best of circumstances, you'll get one leak per thousand feet of seam. If the landfill liner is made by welding strips of FML that are each 20 to 30 feet wide, you can expect one to two defective seams in each acre of landfill.
Based on actual data, Geoservices concludes that a "standard" (typical) leak in an FML has an area of one square centimeter (1/16 of a square inch) and that the "standard" (average) number is one hole per acre. They point out that this "standard" hole size and standard number per acre are based on the assumption that "intensive quality assurance monitoring" will be performed during liner installation, so clearly we are talking about the best case, not the worst case here. Design flaws, poor construction practice, or poor quality assurance would result in larger holes, greater numbers of holes, or even large tears. (pg. B-13)
Geoservices then goes through an elaborate mathematical analysis to figure out how much fluid will pass through a composite liner under the best possible conditions and under less ideal (but still optimistic) conditions. They conclude (pg. B-41) that the "best demonstrated available technology" (BDAT) for composite landfills liners will allow leakage rates somewhere between 0.02 and 1.0 gallons per acre per day. (See Table B-10 on pg. B-51.) Thus they conclude that a 10-acre landfill will have a leak rate somewhere between 0.2 and 10 gallons per day, or between 73 and 3650 gallons of fluid per year; over 10 years, such a landfill will allow the leaking of 730 to 36,500 gallons of fluid. And this is the "best demonstrated available technology"--the very best we can do when everything goes right.
Next week we will show that leaking 730 to 36,500 gallons of toxics into a water supply during a 10-year period guarantees destruction of the drinking water resource.
We will also show that the Geoservices study is unduly optimistic because, as they say themselves (pg. B-7), "Many tupes of FMLs swell when placed in contact with chemicals. As a result, the distance between polymeric chains increases and permeability increases. Therefore, an FML can have a low permeability for water and a high permeability for some chemicals."
Environmental Research Foundation
P.O. Box 5036
Annapolis, MD 21403-7036
phone (410) 263-1584
fax (410) 263-8944