What Can You Do With A Problem Landfill?

Neal Miller

Government cover-ups usually touch off anger from citizens. But in Oakland County, Mich., this past fall, crews put the finishing touches on a government-sponsored cover-up that has local citizens breathing a collective sigh of relief.

Under the direction of the Mich-igan Department of Environmental Quality (DEQ), City Environmental Contracting, a division of Detroit-based City Management Corp., has nearly finished capping the Water-ford Hills Sanitary Landfill. The project is a major first step in an $11.3 million state-sponsored effort to cut off groundwater contamination from the site and to determine the best cleanup method.

Unlike other, more straight-forward capping projects, Waterford Hills presented an added challenge. To meet slope requirements for a stable cap, City Environmental Contracting carved almost a million cubic yards from the mountain of refuse and transferred it to a new double-composite-lined cell adjacent to the existing landfill.

An Ill-Fated History Located on a 50-acre site in Oakland County's Waterford Town-ship, northwest of Detroit, the Wa-terford Hills Landfill aroused the ire of neighboring residents for more than a decade. Since opening in 1981, the landfill repeatedly received complaints about blowing trash, odors and its close proximity (less than 2,000 feet) to Maceday Lake. The landfill is located within the borders of the popular Pontiac Lake State Recreation Area.

Developed on the former site of a sand and gravel mining operation, the landfill also raised drinking water concerns due to its close proximity to several homes with residential wells. The site's original owner, Gene Hirs, had won the right to open the landfill through a court challenge after Waterford Township officials denied his landfill permit re-quest in 1981.

During operation by Hirs and, subsequently, Oakland Disposal Inc., the landfill consistently attracted regulators' attention due to problems such as failing to maintain adequate cover. But the state didn't have cause to take serious action until October 1989, when 1,1 di-chloroethane first showed up in groundwater monitoring wells.

After subsequent groundwater sampling and testing revealed significant levels of 1,1 dichloroethane and six other contaminants, the DEQ issued an October 1990 order directing Oakland Disposal to shut down the landfill and take corrective action.

The existing landfill is equipped with a single 30-mil PVC liner. It's still unclear whether the contaminants were released due to liner failure or problems with leachate collection and removal, according to Jim Sygo, chief of the DEQ's Waste Man-agement Division.

"It could have been a combination of both. We [felt] the first step would be to cap the old cell to cut off any further infiltration and generation of leachate." Meanwhile, the DEQ made sure the collection system was operating properly to reduce leach-ate quantities already in the cell, Sygo said.

But the DEQ was unable to negotiate a consent agreement with Oakland Disposal to provide for capping and cleaning up the landfill. Oakland Disposal, which was facing serious financial problems, failed to comply with the DEQ's or-der to begin closure and remediation.

In January 1991, the DEQ denied Oakland Disposal's request to construct and open a new cell adjacent to the existing landfill. After the company ignored an Oakland County Dis-trict Court order to address the site's problems, in December 1991 the court ordered the DEQ to cap the landfill.

To fund closure and remedial investigation, the DEQ turned to Michigan's $800 million, tax-fi-nanced Environmental Protection Bond program. The $11.3 million appropriated for the project so far covers only the cost of capping, re-lated closure activities and a hydrogeological investigation to determine the extent of contamination and a containment strategy. Additional funds likely will be needed for remedial action, which could get underway this year.

Meanwhile, the state continues to seek recovery from Oakland Dis-posal, waste haulers and generators. In addition to $750,000 in bond money forfeited by Oakland Dis-posal, approximately $1 million has been collected from settlements with de minimus waste generators who paid $5,000 each to free themselves from additional liability.

In January 1994, an Oakland County District Court judge sealed the fate of the Waterford Hills Landfill by approving the DEQ's plan for permanent closure. First, to meet the 4:1 slope needed for a stable cap on the existing landfill, a portion of the waste would be transferred to the adjacent double-lined cell. Then the existing landfill and the new cell would be permanently capped.

Moving A Mountain The project presented multiple challenges for City Environmental Contracting, which won the bid to handle the waste transfer and landfill closure. With capping already delayed by years of negotiation and litigation, the court, the DEQ and local residents were eager to see the project completed quickly. To minimize odor, most of the waste was transferred during cold winter months. Work began almost immediately.

Because of potential hazards un-earthed by the massive waste transfer, safety was a prime concern. The already-controversial nature of the landfill also required special sensitivity to community relations.

To help keep costs down and to ensure that the new cell and cap would meet regulations, the DEQ handled much of the design work internally, relying on some plans initially developed by Oakland Disposal. For example, due to Oakland Disposal's plan to expand the landfill, the new cell already was under construction when the site closed. The DEQ, which has Subtitle D regulatory authority in Michigan, had enough engineering expertise to complete the design work.

"Typically, we don't actually sit down and design caps, but we did have the capability in-house to do that," Sygo explained. "Because of our knowledge of the site, we felt we could more effectively complete the design and get the project moving."

To bring the existing refuse pile within maximum slope limits yet keep the site's overall footprint as small as possible, the new cell needed to be just large enough to accommodate the transferred waste. Using a computer modeling program, engineers defined new contour lines for the landfill and calculated the expected cut and fill quantities. The waste transfer eventually trimmed approximately 45 feet from the landfill's elevation, leaving the total elevation at approximately 1,151 feet.

The original contract underestimated the amount of waste and earth to be moved, according to Dennis Oszust, project manager for City Environmental Contracting. The initial projection of 836,000 cubic yards of waste later was revised to 910,000 cubic yards. Based on before and after physical surveys, Oszust estimates that the actual amount of waste transferred was close to 970,000 cubic yards.

The waste removed from the refuse pile filled an eight-acre cell. The cell's base uses a double composite liner system: two 60-mil HDPE liners made by Gundle, now GSE Lining Technology Inc., backed by two layers of compacted clay. A single composite system, one 60-mil liner and a layer of compacted clay, is used on the cell's sides.

To achieve the original completion date of November 15, 1995, and to prevent the need to transfer waste during warm weather, which would aggravate odor problems, City Environmental Contracting put the project on an accelerated schedule, Oszust said. "To get the refuse transfer done before spring we ultimately worked a double shift seven days a week, 24 hours a day," he said.

The liner system for the new cell was installed in December and January, under adverse conditions that required paying the subcontractor on a time-and-materials basis. The waste transfer, which began in February 1995, included two major operations. First, City Environmental Contracting used four Caterpillar bulldozers (two D-10Ns with refuse packages and two D-10Ls) on the existing landfill's face in order to push waste toward the near face of the new cell. The length of pushes generally was limited to 500 feet.

Second, to transfer waste from the opposite side of the existing landfill to the far side of the new cell, a dig-and-haul operation used two Caterpillar 245 backhoes, with grapples, off-loading to highway trucks. A maximum haul was approximately one-quarter mile.

Once transferred to the new cell, the waste had to be re-compacted, just as in a standard landfill operation. "We had to make three to five passes with a 45,000-pound gross weight compactor, in this case an 815 trash compactor," Oszust said,

Although the Waterford Hills landfill had accepted only mixed municipal solid waste, City Environmental Contracting still was prepared for potentially uncovering hazardous materials during waste transfer.

"No hazardous materials were anticipated, and we didn't run into any hazardous wastes or barrels. But we did hit a few pockets of asbestos," Oszust said. "Our crews were suited with special equipment at all times to protect them against potential contamination."

Methane And Odor Control Because the landfill didn't have a methane venting or collection system in place, to reduce the risk of fire or explosion, City Environmental Contracting constantly monitored for landfill gas. Little methane was detected - probably because the existing landfill had only a minimal cover of sandy material that wouldn't allow methane to collect, Oszust said.

A passive system has been installed on the existing landfill and the new cell to collect and burn off methane gas. To reduce interference with the runway lights at a nearby airport, the number of methane gas flares were kept to a minimum.

A more critical concern during the waste transfer - at least from a community relations standpoint - was odor control. Fortunately, the cold weather provided some odor suppression; a variety of odor control products also were employed.

"We used a dual approach to odor suppression," Oszust explained. "We applied odor control products directly to the exposed faces [of both the existing landfill and the new cell] as we transferred the refuse, and we used various misting products to mask any odor that was emitted."

City Environmental Contracting fabricated its own misting and dispersion system, setting up misting equipment behind large-diameter directional fans which provided the flexibility to adapt to changing wind conditions. Rather than relocating equipment when the wind shifted, crews could simply change the direction of the fans.

Oszust believes effective odor control helped to minimize residents' complaints. Maintaining effective communication with neighbors also was a high priority. In addition to a new community hotline to field questions and concerns, neighbors had an open invitation to visit the landfill.

With the waste transfer completed in the spring, City Environmental Contracting spent the next several months installing the final cap on the existing landfill and the new cell. The cap for both consists of four feet of cover material topped with a geosynthetic layer, a 40-mil very-low-density polyethylene liner, vegetative cover and seeded topsoil.

While much remedial action work to clean up existing contamination still lies ahead, the capping of the Waterford Hills Sanitary Landfill may bring the first sense of "closure" to a problem that has haunted neighboring residents and state officials for more than a decade.