Among the roadside attractions along U.S. Highway 99 through the flat, agricultural expanse of the San Joaquin Valley, the Fairmead landfill would probably rate near the bottom of anyone’s list.
Few motorists heading north to Merced or south to Fresno realize that around the 160-foot-high hill where thousands of tons of trash are buried lies one of the largest known concentrations of fossils from long-extinct mammals that roamed the valley between 750,000 and 1.6 million years ago.
Since the first great, curved mammoth tusk was discovered in 1993, when a new section of the Madera County landfill was opened, the Fairmead site has yielded more than 16,000 large fossils and 5,000 microfossils from about 36 species, said Diane Blades, co-founder of the San Joaquin Valley Paleontology Foundation.
Except for volunteers, the public has mostly been kept from the 116-acre landfill for more than a decade as fossils were uncovered. But that may change under a plan by the county and the foundation to build a natural sciences museum and visitors center on the site.
Fossils so far have been found over more than 14 acres at depths of 10 to 60 feet, making Fairmead one of the largest middle-Pleistocene fossil beds in North America, scientists say.
“There’s no indication of fossils running out any time soon,” said Robert Dundas, a vertebrate paleontologist at Cal State Fresno who was among the researchers to identify the first mammoth tusk excavated in 1993. “I don’t think anyone knows how big the site really is.”
The current vision for the museum includes several modular buildings containing exhibits of some of the fossils found at the site; a laboratory where fossils would be prepared for exhibit; a display of how the landfill operates; and a 3,600-square-foot, tent-like structure that would cover the site and allow visitors to watch as the ancient remains were retrieved from the earth.
But even as the county and foundation proceed with fundraising for the museum, a dispute has arisen between Blades and the county over management of the fossil-extraction process. Monitored by Blades from 1993 until earlier this year when she resigned, the process has ground to a halt as the county prepares a “mitigation plan” that meets the requirements of state environmental law, said Kathy Kivley, deputy director of the Madera County Resource Management Agency.
Under the law, the county is required to have monitors at the landfill looking for fossils whenever any new digging occurs. But in recent months, the number of paid and volunteer monitors has dwindled. By late last month, when the last monitor left, the county ordered fossil recovery operations halted until the mitigation plan was in place.
Kivley said the county expects to choose one of five environmental consultants to prepare the mitigation plan that would permit burial of the trash as newly exposed fossils are excavated. County officials said it could take several months to select a consultant and prepare a mitigation plan.
The dispute illustrates the dilemma that Madera County officials face as they deal with protecting a unique scientific resource that happens to lie beneath the county’s only landfill.
Under the old mitigation plan, a bulldozer was used to scrape a thin layer of earth away. Monitors working with a small group of volunteers identified and tagged the fossilized remains and, in some cases, arranged for larger specimens to be encased in protective plaster before removal.
Once the fossils were removed to a depth of 50 to 60 feet, each five-acre bulldozed pit -- known as a cell -- was lined with plastic material to contain contamination from the garbage dumped into it. Once the cell was filled, it was covered with topsoil and work began on a new cell.
The system worked well for years and resulted in the recovery of thousands of specimens now at the University of California’s Museum of Paleontology in Berkeley, said Mark Goodwin, assistant director of the museum.
Indeed, the fossil cornucopia has led county officials to ask how many are enough, since hundreds of examples of the same Pleistocene mammals have been recovered over the years, said Madera County Engineer John Mitchell.
Goodwin, like many in the scientific community, argues that the county is obligated by law to remove and preserve all the fossils uncovered at Fairmead. Despite the duplication found in the fossil beds, there is no end to future discoveries, he said.
Goodwin and Dundas agree that if the landfill had not existed on top of the fossil beds -- thus requiring the county to remove and protect them -- there would have been no money to pay for the 11 years of scientific work at the site.
According to Blades, county supervisors raised the so-called tipping fees for solid waste disposal at the site after the fossil beds were discovered in 1993 to help pay for the cost of monitoring and removing the ancient remains. But county officials, none of whom worked for Madera County 11 years ago, said they could not find any records to support Blades’ contention.
The Fairmead fossils reveal an ancient world inhabited by a variety of prey and predators -- some familiar and some long extinct. No human remains have been found. Among the prey species are mammoths, two types of camels (one of which looked like a modern-day llama) and three species of ground sloth.
The predators were large and fearsome. In addition to saber-toothed cats, including the Smilodon californicus (the California state fossil), there was the fearsome giant short-faced bear, which was much larger than today’s grizzly.
When these creatures roamed the Central Valley, it was a vast, marshy area because drainage through San Francisco Bay was blocked, Dundas said. “It was probably something akin to an African waterhole today.”