Superfund Information Systems: Site Profile

Superfund Site:

DELAWARE SAND & GRAVEL LANDFILL
NEW CASTLE, DE

Cleanup Activities

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Background

The 27-acre Delaware Sand & Gravel Landfill Superfund Site is located in New Castle, Delaware. Between 1968 and 1976, the landfill accepted municipal and industrial wastes including drums containing organic and inorganic chemicals. Waste and leachate from the landfill contaminated soil and groundwater with hazardous chemicals.

The site was placed on the National Priorities List (NPL) on September 8,1983. Following several cleanup actions, operation and maintenance activities are ongoing. Additional cleanup actions are planned.

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What Has Been Done to Clean Up the Site?

Several cleanup measures have been implemented including:

  • Installation of an underground slurry wall around the Drum Disposal Area.
  • Excavation and off-site disposal of drums and contaminated soil.
  • Construction and operation of a bio-venting system which supplied oxygen to live microbes in the soil from 1997 to 2009, enabling them to break down hazardous substances.
  • Installation of multi-layer landfill caps at the Inert Area and the Grantham South Area.
  • Extraction of contaminated groundwater from the Upper Potomac Aquifer with onsite treatment and discharge to surface water or discharge to the local wastewater treatment plant.
  • Since 2000, the Artesian Water Company, which supplies water to the community, has been treating water from its Llangollen well field with carbon to remove the chemical bis(2-chloroethyl)ether (BCEE), a contaminant which has been traced to the Delaware Sand & Gravel Landfill Site. In 2014, Artesian installed an ultra violet/hydrogen peroxide treatment system at the Llangollen well field to remove 1,4-dioxane, another contaminant from the Delaware Sand & Gravel Landfill site. Visit Artesian Water Company's website for information on drinking water quality testing results.

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What Is the Current Site Status?

  • Volitile organic compounds (VOCs), including benzene, 1,4-dichlorobenzene, ethylbenzene, trichloroethylene, 1,2,4-trimethylbenzene and xylenes, were detected in outdoor and indoor air samples collected at a business adjacent to the Inert Area in April and June 2013. While the source of the VOCs was not confirmed, several of the VOCs detected in the indoor air samples at concentrations that exceed the industrial air screening level are contaminants of concern in the site groundwater. These contaminants were also detected in soil gas samples collected at the site in 2006, which is likely due to landfill gas migration.
  • EPA performed calculations of potential health risks using the test results from the air samples collected in June 2013. The estimated risks for exposure to outdoor air did not exceed EPA’s criteria for acceptable risk.
  • EPA has conducted several Five-Year Reviews of the site’s remedy. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review, completed in 2015, is available here.
  • The Delaware Sand & Gravel Remedial Trust began monitoring groundwater for perfluoroalkyl substances (PFAS) in fall 2016.  EPA will oversee the monitoring and conduct or oversee a risk analysis to determine if these contaminants need to be addressed by the response actions at the site in the future.
  • EPA issued a Record of Decision Amendment at the Delaware Sand & Gravel Landfill Site in December 2017 to address the source material and groundwater contamination. 

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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

Institutional controls at the Delaware Sand & Gravel Site include restrictions that prevent any future use of the Inert or Drum Disposal Areas that could compromise the effectiveness of the selected cleanup remedy and restrictions preventing the installation of drinking water wells at the Drum Disposal Area.

 

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Sampling and Monitoring

Sampling and testing results are available in the Administrative Record of the site.

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