Environmental Progress - Winter 2003

Environmental Progress : Winter 2003

Hawks, Deer Are Calling Remediated Urban Landfill Home

Just four years ago, Paxton II was a major environmental threat

Four years ago, an improperly operated and closed 170-foot tall mountain of garbage on Chicago's southeast side threatened to release several hundred thousand cubic yards of garbage, spill millions of gallons of contaminated leachate onto adjacent properties and wetlands, and possibly even to ignite when its high temperatures and flammable gases were suddenly exposed to oxygen. Dubbed a "garbalanche" by the media, Paxton Landfill II was described as "an environmental disaster waiting to happen." It threatened to shut down nearby roads and expressways and possibly force evacuation of residences miles from the site.

The top 15 acres of the Paxton II landfill were regraded and capped as part of the remediation work.

Today, following a well coordinated and timely response from several quarters, the site is under control and its threat has been greatly reduced. Monitoring and some additional work continue at the site, but today it demonstrates successful remediation of improper construction and years of faulty operation. It also demonstrates the resilience of wildlife, even near a major metropolitan area. Mice live in the tall grasses on the site, hawks stop by to dine, and white tailed deer have taken up residence.

A legacy of sloppy operation

Years of improper construction and operation had left Paxton II with steep, eroded and unstable slopes that were becoming progressively weaker due to erosion and the buildup of liquids within the landfill. The top had settled into a bowl-shaped depression, collecting rain and snow. This ponded water penetrated the inadequate soil and slag cover on the landfill and percolated through the buried garbage, creating leachate. Rainwater also ran down the slopes causing serious erosion, weakening those slopes and allowing even more water to enter the landfill. These unstable slopes were at risk of collapse, causing landslides of waste and leachate. A "garbalanche" would have created significant, immediate threats to public health and the environment.

In March of 1999, the Illinois EPA initiated a stabilization effort to reduce the threat of slope failure by pumping out the leachate and preventing additional rainwater from infiltrating the waste by regrading and capping the landfill's crown. Downchutes were constructed on the sideslopes to collect and convey storm water to two existing on-site ponds for retention and settling before being released from the site. The ponds and the vegetation on the new landfill cover will reduce storm water flow off the site by 10 to 24 percent during major rain events and also improve its quality.

Landfill accepted garbage for 21 years

The site began operation in 1971 and accepted waste until 1992. Paxton II and its owner/operator had a history of violating dozens of environmental regulations, not the least of which was continued landfilling of waste 100 feet above the site's permitted height. The result was an unstable and very steep hill containing 13 million cubic yards of waste.

White tailed deer find the new cover on the old landfill an attractive place to live.

During a 1998 site investigation, the Illinois EPA determined that a very real threat of a slope failure existed at the site. In addition to the disruption of business and traffic in the area, and the threats to human life, the cleanup costs for a slope failure would have been two to three times the cost of the remedial activities. Repair, stabilization and retrofitting of an old landfill that was not constructed properly and violated permit requirements is inherently more expensive than constructing it correctly from the beginning.

The IEPA's corrective actions at the site in the last four years included regrading and capping the top 15 acres of the landfill to reduce leachate generation, construction of storm water ditches and downchutes to minimize erosion, installation of 24 gas collection wells and a gas flare to burn off methane gas which continues to be generated by decompostion, and installing a leachate collection system and force main to remove several million gallons of leachate each year so it can be pumped off site for treatment. The steep 2:1 side slopes (this translates to approximately a 68 degree slope) precluded capping the side slopes and would have made retention of topsoil on the landfill sides difficult. Using the ditches and downchutes to manage rainfall and quickly remove stormwater from the landfill slopes proved more effective. The previously unvegetated slopes were then covered with topsoil and seeded to encourage grass growth, further stabilizing the slopes.

New clay cap has reduced rain infiltration

A two-foot clay cap was placed over the newly graded top and an innovative shredded tire drainage layer was placed over the clay cap. Two additional feet of protective soil and a one-foot topsoil layer completed the design. This cap dramatically reduces leachate generation from rainfall events.

In 1999, an interim leachate collection system was constructed to collect leachate from the base of the slopes. This provided immediate improvements in slope stability by dewatering the toe of the slopes. A permanent leachate-removal system was installed and began operating in September of 2001. Now leachate is collected at an average rate of 10,000 gallons per day. The liquid is pumped to a Metropolitan Water Reclamation District sanitary sewer over a mile from the site, then to a wastewater treatment facility.

Future use

In June of 2000, the state of Illinois and the city of Chicago committed to an ecological, environmental and industrial rehabilitation of the Southeast side. Numerous local environmental and community groups are also committed to maintaining the momentum from the Paxton II improvements to nearby environmentally impacted sites. A broad vision of rehabilitated wetlands, wildlife observation areas, biking and hiking trails, and a visitor center has been discussed. With its dominating height, the Paxton II Landfill is a natural focal point in the development of this vision.

However, many area issues including property access, funding and ownership will need to be resolved before this vision can become a reality. What is certain is that local wildlife considers Paxton II an attractive home and see no reason to wait to move into what it considers prime real estate.