landfill leachate

In brief –

 

Leaking landfills have been the focus of public attention, and, already leaks are too frequent. But, the more immediate and serious threats come from elsewhere – from landfill covers that are almost certain to fail soon after care ends, and from leachate drainage lines prone to clogging. These are more likely to lead to catastrophic and expensive site failures long before most liners deteriorate.

 

Groundwater protection based on liners

Landfill groundwater contamination

Unlike the open dumps of the past, since EPA promulgated the first federal landfill rules in 1991, most landfills have been lined. This was done in an effort to isolate the buried wastes and prevent pollutants from leaking into the groundwater, contaminating drinking water supplies.

 

Summary of groundwater protection rule

EPA’s 1991 groundwater rule was intended to protect drinking water by regulating the location, design, operation, monitoring and closure of landfills.

Landfills were supposed to be designed and operated as dry tombs to minimize the mobility of the dangerous constituents, and also to include additional layers of defense–

 

In practice, though, too often the rules’ requirements have been ignored or compromised by state regulators, to which the federal law delegates enforcement, in order to be responsive to landfill owners’ desires to minimize costs.

 

Landfill requirements often ignored

The groundwater rule was intended to provide defense in depth, but, too often, that does not happen.

In practice –

  • Wetlands. Too often, landfills are permitted in wetlands (Potrero), within flood plains below sea level (Redwood), near earthquake faults (Sunshine Canyon), over sinkholes certain to collapse (Cedar Ridge) and, until a public outcry led the legislature to ban the site, another (Black Bear) was about to be permitted on the Atlantic coast, within the hurricane storm surge zone, where the water table was at the surface, and lifted up on a manmade 50 foot platform.
  • Toxics. While industrial hazardous compounds are banned, household toxics are not. Also, many lined landfills have been built on top of unlined and leaking hazardous landfills (Kettleman and Sunshine Canyon).
  • Exceptions. In practice, landfills are, sometimes routinely, granted special exceptions to accept industrial hazardous wastes, to add or recirculate liquids in ways that violates dry tomb conditions, and to forgo installation of a seal on top of the landfill.
 

Essentially, the rule’s criteria, which were intended to reduce some of the risks of burying trash, have often been subordinated to sites favored for economic and political reasons, for their proximity to collection routes or transfer points, or their ability to be easily sited in poor communities – as well as with design and operating compromises that increase profitability with disturbingly insufficient attention to the long-term consequences.

 
Landfill Groundwater Impacts

However, in addition to the rule’s failures, as applied, the more serious problem is the fact that the barriers relied upon are badly flawed.

Liners delay – not prevent – pollution

Little is really known directly about how well those liners are functioning today while the sites are still being operated. Deep inside a landfill, measuring instruments needed to detect liner problems would get crushed, and the monitoring wells at the perimeter of the site are too far apart. Also, the liners, which were first required in 1994, should at least delay the onset of leaks for awhile. Even so, leaking landfills are already a too frequent occurrence.

 

Landfills are leaking long before expected. There is no comprehensive data base of landfill leaks: reports have to be compiled from news accounts. Also, some reported leaks involve sections of landfills that were unlined, although that begs the question of why lined landfills were permitted on top of leaking unlined cells.

Inasmuch as the expected problems with liners that were properly installed at carefully maintained sites lies in the future, the record today fails to reach that larger issue. In any event, examples of landfills that experienced leaks reported by the news media include –

  • Waste Management's Tontiown Landfill (Little Rock AR) in 2002
  • Waste Management's Cedar Grove Landfill (Cedar Grove TN) in 2009
  • Waste Management's Muskego Landfill (Milwaukee, WI), 2009
  • Waste Management's Pottstown Landfill (Pottstown, PA), 2005
  • Waste Management's Live Oak Landfill (Atlanta, GE), 2005
  • Orange County Landfill (Orange County, CA), 1996
  • Southeaster Public Service Authority's Suffolk Landfill (Suffolk, VA), 2003
  • Safety Kleen's Rimini Landfill (Lake Marion,SC), 2001.

If you know of a leaking landfill, please email us This email address is being protected from spambots. You need JavaScript enabled to view it. , and include any documentation.

 

Yet, what we have seen today is not the main concern, but rather what lies in the future. For today’s lined landfills suffer from the same systemic flaw – the barriers, being manmade, have limited lives, while the threats posed by the mountains of trash effectively persist forever.

 

Reasons why liners leak. Liner integrity can be compromised over time by–

  • Manufacturing mistakes
  • Improper installation of the liner the fail to permanently glue one sheet to the next or puncture the liner
  • Damage to liner if the first layer of trash at the bottom contains sharp objects or the compacting bulldozers apply too much force
  • Household cleaners and paint residues that either permeate or subject the liner to stress cracking
  • Leachate that drains to the bottom, fails to drain away and raises a head over the liner.
 

This fatal flaw was not unknown to EPA when it decided to ground landfill safety on liners. The agency’s technical staff repeatedly warned about the flaw through the decade of the 1980s leading up to publication of the 1991 groundwater rule, which was adopted for political, not technical, reasons.

 

EPA knew its liner-based rules were flawed. Even composite liners “will ultimately fail” within decades after the agency's post-closure care requirements have expired, they advised, and when the liners fail, “leachate will migrate out of the facility.” Yet, its staff recognized, the duration of a landfill’s hazardous loadings that need to be isolated may be “many thousands of years,” long after the time when discharges will occur.

Why did the EPA nonetheless proceed to rest safety on a flawed technology? The answer is not edifying. “EPA officials,” an investigation by the agency's Inspector General reported a decade later, made the decision “based on a compromise of these competing interests ... not based on specific scientific criteria or research studies.”

 

Still, while contaminated drinking water continues to worry us, especially for the future, as our experience has grown, other matters dealing with the cover and leachate collection system have actually turned out to be of greater and more immediate concern.

More important than liners

Other key groundwater safety systems are far more likely to fail, to fail sooner and to fail more catastrophically than the liners beneath the site. In particular, that is the cover above and the leachate collection pipes along the bottom, which are identified with red arrows in the preceding diagram.

Landfill groundwater contamination

Sunrise Landfill’s catastrophic cover failure

Covers are mission critical for safety. The final cover that caps a closed landfill usually consists of a two foot dirt or clay foundation and a thin plastic sheet the thickness of a credit card. It is overlaid by a drainage layer and a foot or so of dirt for vegetation to protect the cover (and at other times, the cap consists of just a few feet of dirt). That cover is mission-critical for safety.

If that cover is breached, rainfall will re-enter the site and re-ignite a second wave of decomposition in the organic wastes below, which can set cascading failures in motion [in the link, select the attachments Presentation 1, Slide 10, and Discussion Paper]. If the landfill fails catastrophically at one time from an extreme weather event, or over time from the accumulation of many tears, garbage may washout into adjoining waterways and massive landslides could shear off from the manmade mountain of trash.

 

Cover damage can lead to site failures. Just under the surface, the cap is vulnerable to being breached any number of ways, such as from heavy rainfall, animals burrowing through and tree roots penetrating the seal. This is what EPA’s Inspector General found in 2001 was already happening routinely from storms and from pigs, bears and marauding teenagers even while the sites were still being managed.

In 1998, a catastrophic cover failure occurred during heavy rains at the Sunrise landfill near Las Vegas. That failure discharged garbage, medical wastes, sewage sludge, asbestos, construction debris and soil contaminated with oil into the Las Vegas wash that feeds Lake Mead, which is the main source of drinking water for Las Vegas and Phoenix and parts of California. Republic Services, the landfill’s operator, vigorously opposed EPA’s order for long term remediation of the site, finally signing a consent agreement in 2008. Clean up costs are estimated at $66 million. (Interestingly, the company was able to afford to give its executives bonuses worth as much as twice that).

Under other provisions of the groundwater rule, after 30 years of postclosure care for closed landfills, they are likely to be abandoned. However, covers will continue to deteriorate from these same causes we are seeing today. But, then, no one will be around to monitor and repair the damage before the site fails.

 
leachate collection

Leachate collection system being installed

Leachate collection. Collection pipes are lain across the bottom of the landfill to remove the rain that drains down through the garbage, becoming contaminated leachate, and keep the site dry. However, they are prone to clogging, and when they do, the accumulating leachate head “is not only a concern with respect to leakage through the base liner system, but can also negatively impact the stability of the landfill. ... [T]he failure can be enormous [and] waste masses up to [two football stadiums] have failed and actually liquified [and] slid over a distance of [almost a mile] in a matter of minutes.”

 

Liner damage also leads to site failures. The liners that are laid on the bottom of a landfill effectively make the site into a giant bathtub. Since rainfall freely enters the site while it is open to accept trash, and may continue to do so through tears in the cover after it is closed, EPA concluded that a drainage system is essential to prevent accumulating water from damaging the liner and eventually overflowing. Other experts add that rising water also threaten site stability.

To extract the leachate that drains to the bottom of the landfill, perforated pipes, called leachate collection lines, are required to be laid in 20 foot segments about 200 feet apart above the bottom liner in lengths, which extend almost a half a mile in megafills.

Unfortunately, over time pipes this long are difficult-to-impossible to clean out from the ends, and there is no way to clean out the perforated holes if they clog, nor the gravel beds that the pipes are set in.

These pipes can clog up and lose their functionality in several different ways–

  • Pipe clog. Microbial and chemical reactions can create blockages inside the pipe and in the perforated holes in the pipe.
  • Gravel clog. Gravel drainage beds, which are meant to prevent blockages and maintain flow to the pipes, can themselves clog, especially if the wrong type of gravel is used or if the geotextile screens used to block out debris that would fill the spaces between the gravel itself clogs.
  • Joint breaks. At every joint where the 100 or more segments in dozens of long lines are glued together, there is another possible failure point if the glue fails or if the segments were not installed in a straight line.

Maintenance to keep the lines is spotty and often ineffective, and once clogged, little can be done because the cost to dig through so much garbage is prohibitive.

When they do become clogged, leachate will accumulate in growing pools, or “heads” over the liner, weakening its integrity and leading to leaks through the plastic, and, if the head becomes too large, threatening site stability as pore pressures on the liner increase, sheer strength declines and the site becomes to saturated to retain its structural integrity. Sometimes vertical relief wells drilled down into site in an attempt to extract some of the leachate head, but this is rarely effective.

Disturbingly, regulators have studiously avoided any comprehensive investigation of clogging problems, and organized record keeping for citizens to examine is non-existent. But tentative reports suggest that pipe blockages are a common occurrence.

 

Essentially, mega-fills are too big to fix, even when their critical safety systems degrade, threatening major site failures.

 
 
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