New Screening Tool Protects Streams, Wetlands, and Residences From Landfill Risks

LAWRENCEVILLE, NJ – A new screening tool to assess the potential risk posed by contaminated groundwater moving from landfills to nearby streams, wetlands and residences has been developed by the U.S. Geological Survey and the New Jersey Pinelands Commission. 

The recently published article in Waste Management Journal presents the innovative method to assign "levels of concern" to landfills based on a new modeling method.

The tool uses monitoring well and hydrologic data, physical characteristics of the landfill (or other point source) and chemical properties of the contaminant(s) to estimate groundwater contaminant concentrations at receptor locations.

"The method is suitable for a screening-level assessment of the risk posed by a landfill or other contaminant point source, and can be used by regulators and managers using basic spreadsheets." said Ron Baker, a hydrologist with the U.S. Geological Survey and lead author of the study. "This cost-saving approach enables regulators to make more informed decisions as to the need for additional monitoring, a more comprehensive modeling effort, or engineered remediation solutions."

The application of this screening tool was demonstrated by assessing level-of-concern categories (high, moderate or low) to 30 closed, uncapped or uncovered landfills in the New Jersey Pinelands National Reserve, where there may be economic and environmental incentives to redevelop.  Caps do not destroy or remove contaminants, but instead isolates them and keep them in place to avoid the spread of contamination.  Caps also prevent people and wildlife from coming in contact with contaminants.

"This is a valuable tool for scientists and regulators because it provides an economical approach to categorize the relative risks of contaminant sources to nearby human and ecological systems," said, Rick Kropp, Center Director of the USGS New Jersey Water Science Center.

Groundwater-quality data are collected at many landfills, but those data alone are insufficient for deciding whether to take no action, conduct further monitoring, install engineering controls, or cap a landfill.

Landfills that pose no threat of groundwater contaminants leaking to nearby receptors, such as rivers, streams, and residences, may be exempted from further consideration.  At landfills where the screening tool predicts the movement of contaminants of concern, such as nitrate, benzene or mercury, towards receptors in concentrations exceeding regulatory standards may require additional monitoring and/or engineering controls.

"The development and implementation of the screening-level model will allow the Pinelands Commission’s staff to prioritize landfills in need of remedial action and to bring those prioritized landfills to the attention of the host municipalities," said Nancy Wittenberg, Executive Director of the Pinelands Commission. "It will also ensure that remedial actions are commensurate with site specific considerations and hasten approval of environmentally-appropriate, beneficial reuses of select sites, such as the proposed installation of photovoltaic arrays at a grid-accessible closed landfill site in the New Jersey Pinelands"

Beginning in 2016, the Pinelands Commission will advise those municipalities in which a landfill with a high or moderate level of concern is located of the results of the USGS’s screening level assessment, for local follow-up. Host municipalities with landfills that were categorized as representing a low level of concern will be encouraged to meet with the Commission to finalize the closure status of their landfills.