A watchful eye: C&D landfill sites are under increasing scrutiny as operators address issues like hydrogen sulfide gas and groundwater contamination.

A self-evident truth is that C&D landfills are different than those accepting municipal solid waste (MSW) or a combination of other materials. For that reason they have been treated differently, usually with less stringent requirements, by regulators from the federal to the local level. However, some of those gaps are narrowing, and there is apparently some science behind the movement.

THE HYDROGEN SULFIDE SOLUTION

The different materials going into C&D and MSW landfills require different techniques on how they are placed in the landfill cell, says Dr. Timothy Townsend, assistant professor at the University of Florida, Gainesville, Fla. "The densities may be different, the ability to compact is different, gases that are produced and resulting odors can certainly be different. The quality of leachate produced may be much different. MSW has a high organic content, while C&D is much more mineral in nature," he says.

Both have their own separate issues, although most landfill experts agree that proper operating techniques on the part of the site operators can solve most problems. Here also is where both types of landfills have their commonalities, according to Townsend. "They all have the potential, if not operated properly, to pose harm to the environment," he says.

How so? Probably the most talked about issue now for the C&D material stream is hydrogen sulfide gas, or H2S. The wicked rotten-egg smell of H2S is an incredible nuisance odor for humans, and the gas can make a person sick in very high concentrations. Reportedly, it can even kill under the right circumstances. It is attracting the attention of regulators because neighbors of the sites affected are complaining about the smell.

But evidence suggests that H2S is not generated if the landfill is operated properly, and may never even make an appearance. R. David Loewendick, president of S.G. Loewendick & Sons, Columbus, Ohio, offers an example. He says his family owned and operated a C&D landfill for several decades before it finally ran out of room, and now operates a new C&D landfill in the same area (for a look at that operation, please see the article starting on page 20).

Loewendick was asked to be part of a task force appointed by the governor of Ohio to develop new regulations for C&D landfills. While attending the initial meeting, the discussion turned to the problems a few Ohio C&D landfills had with H2S. Loewendick, the long-time C&D landfill operator, says he had to stand up and ask what hydrogen sulfide gas was because he had never heard of it. "That just goes to show that if you operate properly, it is not a problem," he says.

According to J.W. Spear, principal, J. Spear Associates, to create H2S in a landfill environment five basic circumstances are necessary: First, a sulfur source has to be present, which is represented by the calcium sulfate in the gypsum, and then an anaerobic environment, which is possible in a landfill with a good, tight cover. Warm temperatures, between 60 and 90 degrees Fahrenheit, neutral to acid pH in the substrate and liquid water must also be present. "As it is generated in the landfill environment, it will find the path of least resistance to the surface," says the consultant to the landfill industry. "And the only way to stop it is by disrupting the confluence of those issues."

Stormwater management is critical. "We have seen a lot of success from operators picking up the general idea using simple, inexpensive tools to get sites to drain so that there isn't standing water or water flowing into active cells," says Spear. "There was attention given to stormwater when the site was designed and constructed. If the owner/operator just maintains the same level of attention, it becomes no problem."

Spear also suggests that landfill operators in a very wet setting or a site that is just beginning to have an H2S problem dispose of drywall and broken or ground concrete in the same location with as much 'mixing' as possible to shift the pH towards the neutral or alkaline.

Townsend agrees that stormwater management is important but adds "there is nothing more important than putting cover soil on. If you can maintain good cover soil practices, you have taken a big step toward minimizing odor problems from hydrogen sulfide."

WATER WAYS

Another issue Townsend sees rising for C&D landfills is groundwater contamination, especially from the many unlined landfills around the country.

"There is a growing body of evidence that suggests certain components often encountered in the C&D waste stream, such as CCA-treated wood, have the potential to result in groundwater contamination," he says. "However, data from facilities that utilize groundwater monitoring wells find that the impacts are less frequently seen from hazardous pollutants such as arsenic, and more frequently observed from common minerals that leach from basic construction materials such as drywall and wood." These include chlorides, sulfates, manganese, iron and ammonia. Townsend adds, however, that even though facilities which dispose CCA-treated wood may not always observe arsenic contamination at the moment there is still a risk of arsenic appearing in the groundwater in the future.

Currently he is involved in research on the potential impacts on groundwater quality, even though, he says, those concepts have been explored in great detail. "Issues still exist regarding arsenic from CCA-treated wood and newer treated wood products that don't contain arsenic--what is the long-term fate of the chemicals in those products?" he asks. "There are also reasons to believe that the leachate itself, even without the presence of the more toxic chemicals, will change soil conditions and groundwater chemistry underneath the landfill in a manner that might cause other naturally occurring elements to be liberated."

For instance, he cites ongoing research on iron. "In some areas of Florida where unlined C&D landfills are located, leachate gets into the groundwater. The leachate may not have a large concentration of iron, but because it changes the chemistry in the soil underneath the landfill, the iron becomes liberated, While iron contamination may not sound like a very big issue, iron is [found in] drinking water standards. Some landfill sites in Florida are currently required to install a pump-and-treat groundwater remediation system because of iron."

He also says that drywall and concrete can change the quality of the groundwater near a landfill, which raises the question of whether C&D landfills should be lined, similar MSW landfills. Indeed, some states, such as Florida and Ohio, are going to require any landfill expansions or new C&D landfills to be lined.

"The writing is on the wall that some day most of these types of facilities will be required to install liners," says Townsend. "The evidence suggests that they will impact groundwater quality. That impact is not necessarily a major problem with respect to large concentrations of toxic chemicals being released to the environment, but given the ability and relative ease these days of being able to install liner systems, there are now fewer arguments against including a liner system as part of landfill construction."

One possible item some C&D landfill operators may not be getting out of their sites is a legal depletion allowance for landfills under the federal tax code. Spear says that landfills can deplete the value of their air space. "All the big companies know this," he says. "You think they are just being crazy or mean when they drive past a competitor and go another 20 miles to their own site, but they are just picking up the depletion allowance."

It works like this: Say a brand new landfill had a million cubic yards of air space, plus siting, engineering, and constructions costs, plus some good will in their businesses. "They can take some of the good will and some of the land costs, and all of the engineering, siting and construction costs, and divide through by a million cubic yards. Whatever that number is, for every cubic yard that goes into the landfill, that amount drops off the company's federal tax liability" according to Spear.

C&D landfill operators have a tremendously valuable asset in their control. However, they can expect the sites to be under increasing scrutiny and certainly should see changes to current operating procedures. C&DDR 

The author is executive director of the CMRA and associate publisher of Construction & Demolition Recycling. He can be contacted at [e-mail].