Real Science for Real People:

Golfing on a Landfill

 

By Beth Ravit

 

  The Encap project to develop 7 abandoned Meadowlands landfills to build 4 golf courses, 2 hotels, offices, housing and retail space continues to move forward, and permits have already been issued by the US Army Corps of Engineers (USACE) and by the NJ Department of Environmental Protection (NJDEP). The cost to Encap to remediate the landfills is estimated at $100 million. In addition, the company will cover $27.5 million in costs related to leachate^[1] disposal and landfill closure^[2], allowing the State of New Jersey to recover $61.5 million that the New Jersey Meadowlands Commission (NJMC) had set aside to cover these costs. Encap has also committed to pay the NJMC $48.55 million, and produce new tax ratables for Meadowlands municipalities, which are estimated to be close to $1 billion. A lot of money is at stake in a time of very tight budgets.

 

In order to use the landfills for development, the leachate and the contaminants must be contained, and Encap proposes to do this through a process is known as “capping.” This technology, in use since the early 1980s, is still relatively new but is currently considered to be an efficient and economical method to isolate contaminants. The size of the cap is typically determined by the need to 1) isolate the contaminated sediments, 2) minimize chemical releases during the remediation process, and 3) be economically and environmentally viable. Site-specific factors include sediment conditions, levels of contamination and the required degree of protection. Because the technology is so new, we do not yet know how the caps currently in place will perform over a longer time period.

 

The actual cap is composed of three parts (Fig. 1). There is a base layer, which usually consists of sand with some organic material that may contain stabilizing and isolation sub-layers.  The stabilizing layer separates the underlying sediment and the sand cap, provides stability to the sediment in order to support the weight of the cap, and minimizes resuspension of contaminated sediment during construction. The sand layer must withstand the worst case physical and chemical events at the site, and stop the movement of contaminants from the landfill into the cap.

 

The base layer is covered with a filter layer, usually gravel, that provides stability for the lower layer. The filter layer helps distribute the load evenly and protects the base material from hydraulic forces--the velocity and direction of water flow.  The size and pores of the gravel determine the effectiveness of the filter material in protecting the base material.  

 

The top of the cap is the armor layer, usually composed of rocks to protect the filter and base layers from erosion.

 

Once the cap is completed and a leachate collection and treatment system is installed, the landfill is considered ready for development, essentially turning it from a brownfield^[3] into a greenfield^[4].   However, the design criteria for the cap are still a subject for scientific debate, and few studies of actual sediment caps in rivers have been done.

 

Past development in the Meadowlands, no matter how well intended, has done irreparable damage to this important ecosystem. In a time of tight budgets, with a lot of money at stake for State and local governments, the agencies overseeing this project must look beyond the short-term finances, and make sure this project in constructed in a manner that uses the best available technology to provide long term stability for the contaminated sediments. The Meadowlands ecosystem has seen too many projects, which seemed like great ideas at the time they were built, extract an unacceptable price over the long term. We hope the Encap project will be a major step in preserving and improving a valuable natural resource and providing the public with increased access to this unique urban wetland.