Lynn Merrill

When Subtitle D and its stringent requirements for landfill covers and lining systems became effective in 1991, there was concern that these tougher regulations would result in landfill capacity shortages across the United States. Many communities, it was predicted, would face skyrocketing disposal costs as small, local landfills were forced either to install liner systems or close. This fear was compounded by nightly newscasts about a barge named Mobro, whose inability to find a home for its cargo of trash is credited with precipitating the perceived landfill crisis.

At the time, regulators also were trying to determine the appropriate standards for liner and cap systems to ensure adequate groundwater protection. Lacking empirical data regarding the performance of these relatively untested systems, they elected to err on the side of tighter controls and prescriptive standards. States either could adopt the federal requirements or ones that were more stringent, potentially resulting in 50 sets of regulations. The process was further complicated by state regulations that predated Subtitle D.

But over the past decade, the regulatory process has matured, allowing for more flexibility. Some states are switching to performance-based standards.

"It's a question of what the state had prior to the Resource Conservation and Recovery Act (RCRA) Subtitle D requirements coming into place and what they feel comfortable administering," says Ed Repa, director of environmental programs for the Environmental Industry Associations (EIA), Washington, D.C.

"States that implement performance-based standards need to have a regulatory staff that is capable of reviewing the detailed hydrogeology and modeling reports to prove that the landfill containment system's performance still meets the federal standards," he says. "If a state has a strict design standard, well, that's a no-brainer. It's trying to fit the federal program into existing state programs and modify it so that it doesn't change the state programs."

Many states, including Florida, Pennsylvania, Virginia and New York implemented standards that are more stringent than those in Subtitle D.

"In New York State, we've been requiring double liners since 1988," says Robert J. Phaneuf, chief of the Eastern Facility Section of the Bureau of Solid Waste and Land Management within the Department of Environmental Conservation, Albany, New York. "In New York and other northeastern states, concerns about groundwater contamination have demanded more stringent landfill controls."

Since 1982, the department has been trying aggressively to close inappropriately lined and contaminating landfills, Phaneuf says. "The biggest thing that closed a number of our facilities was the federal regulations for corrective measures."

A large number of unlined landfills around the state closed after Oct. 9, 1993, when the requirement became effective because of the long-term responsibility and liability of a groundwater impact, he says.

"It really was the corrective measure requirement for fixing groundwater impacts that prompted a lot of activity and closure of inappropriately lined landfills at that time," he continues.

Because various states have different landfill containment system needs, states were allowed to submit for approval regulations that met or exceeded Subtitle D requirements.

However, this piecemeal approval process has caused individual states to continually change or increase the severity of the regulations administered within their jurisdiction.

"What states have been doing over the past couple of years is coming into the federal government saying, 'we have this state program that meets your standards and we want it all approved,'" Repa says. "Then there have been other states that submitted their programs and have received a partial approval on operational requirements, but they weren't quite there on financial assurance requirements. It's not like a wholesale revamping of the states' regulations to bring them into tighter alliance with the federal standards, but mostly tweaking and fine tuning," he says.

Warming Up to Subtitle D Industry observers believe the state regulations as applied actually are becoming more workable because regulators and landfill operators are gaining more knowledge through field experience.

"We're seeing a real stabilization as far as the use of the regulations," says Michael Cullinane, vice president of Brian A. Stirratt and Associates, a Diamond Bar, California-based engineering firm specializing in landfill design and engineering. The changes have required some states to spend more money and time than they initially anticipated to ensure that the regulations really work for them, he says.

"It's almost sad that states and landfill operators that reacted to the regulations in a timely manner probably spent more money than was necessary," he says. For example Cullinane says California's landfill cover requirements, which include a 2-foot foundation layer, a 1-foot barrier layer with a permeability of 10 -6, and a 1-foot vegetative layer, don't function well in an arid climate.

"What we found is that those landfills in arid climates dried and that the low permeability barrier layer was very expensive to construct," he says. "After three or four years, through wetting and drying cycles, the layer broke down and was ineffective. Some of the facilities that complied with the regulations now are finding they are not functioning as they initially were intended."

Additionally, technologies and materials that were developed after Subtitle D actually may improve the performance of landfill containment systems. New York, for example, has included an equivalent design section in its regulations, allowing for alternative construction and operational materials in certain components of the landfill liner and final cover system.

"The modern landfill is a vast consumer of natural construction materials and some [parts of the waste stream] can be re-used, providing an alternative to virgin construction and operational materials needed to build or expand landfills," Phaneuf says. "We realize that improved construction materials relating to landfill liners and final cover systems continue to evolve. These provisions allow for future landfill construction to take advantage of new materials."

This ability to use alternative materials may provide a market for some of the feedstocks coming from communities' recycling programs. For example, in Madison County, New York, using glass scraps to construct the landfill's primary drainage layer has saved the county $35,000 per acre in construction costs. Using tire chips in the landfill's leachate collection and removal system, and the gas venting layer also has reduced costs.

However, New York has stringent double liner design requirements to mitigate the potential for leachate contamination. "People are very concerned about their drinking water source," Phaneuf says. "The damp environment of the northeast has a significant potential for generating leachate within a landfill. Double liner systems are necessary to ensure protection of groundwater resources."

Phaneuf points to the success of the state's 38 active, double-lined landfills. "We have no indication of any groundwater-related impacts," he says, "despite collecting more than 450 million gallons of leachate during 1997."

Lessons Learned Many lessons have been learned by implementing the federal regulations, including what works and what doesn't. Consequently, the U.S. Environmental Protection Agency (EPA), Washington, D.C., is revising the current landfill capping guidance documents, which clarify the requirements to engineers in the field.

"In the past, we never really addressed the long-term maintenance of landfill caps," says Kenneth Skahn, environmental engineer in the Office of Solid Waste and Emergency Response at the EPA. The guidance document will cover topics such as regulatory requirements, alternative designs and geotechnical analysis and design. "One of the most important sections will address the lessons learned from past cover installations," he says. "It will address the subjects that have caused high maintenance or failure of some caps in the past, including erosion, insufficient flow capacity in drainage layers, slope stability and proper grading."

The final chapter of the guide will deal with long-term maintenance issues. "This is an important area," Skahn stresses. "I get the sense that people think that after 30 years, owners and operators are going to walk away from their sites because they've completed their obligations for maintaining caps."

Actually, the cap must be maintained as long as the waste remains a threat to human health and the environment, he says. "While we believe that caps should last hundreds of years, based on our testing of materials and predicted life spans, we have to know how these caps are performing. We are going to make clear what activities should be performed to maintain a cap adequately and ensure it has a long life."

The guide will assist regulators in evaluating proposals from landfill owners and operators regarding the use of alternative materials or designs, Skahn says. So far, the first draft of the document has been written and is expected to be in review at least one year before it is released.

Impacts at the Tipping Face While the state and federal regulations have worked to improve the quality of landfill operations, creating a demand for more environmentally sound landfills, they also have reduced the number of landfills nationwide. In New York, the number of operating landfills dropped from 1,600 active sites in the mid-1960s to 38 active landfills in 1998.

But Repa says the real impact was on operators who were running marginal facilities. "It [Subtitle D] was for the group of people who were operating open dumps," he says. "They pretty much got out of the business if they were running something that really was substandard.

"Many of the better facilities already were doing a lot of what the regulations required," Repa continues. "I think the impact was minimal if you were a good operator because you already were installing liners."

Cullinane agrees that the regulations have increased the quality of operations. "We find that the facilities are operating much better than they were 15 years ago," he says. "This is because when landfill operators spend money, they look to get the best performing system they can. In the long run, those facilities will have a lower potential for groundwater issues or gas migration problems."

Nevertheless, the costs for compliant caps, containment systems and liners can be minimal. "When we looked into the true cost of the double liner system, it was small compared to the overall cost of developing a landfill," Phaneuf says.

A double lining system does not add a significant amount to the per-unit cost compared to not having a liner system and the other systems that would need capital funds as a result. "It's only a small fraction of the tipping fee," he says.

"It's cheap insurance and allows the facility to move ahead in the permitting process without concerns."