An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Hazardous Waste Cleanup: Hercules LLC Research Center in Wilmington, Delaware

On this page:

EPA issued a Resource Conservation and Recovery Act (RCRA) Corrective Action permit July 2, 1991, and identified 16 Solid Waste Management Units (SWMUs) and four Areas of Concerns (AOCs) at the facility. SWMUs and AOCs are units that require investigation to determine if corrective measures for cleanup are necessary. Delaware Department of Natural Resources and Environmental Control (DNREC) reissued the Corrective Action Permit on December 1, 2004, and is the lead agency for Corrective Action at this facility.

Cleanup Status

Hercules conducted a RCRA Facility Investigation (RFI) of the SWMUs and AOCs and reported the results in July 2001.  A Phase II RFI workplan was approved by EPA and DNREC thereafter, and the Phase II RFI Report was submitted to DNREC in 2007.  DNREC commented on the Phase II Report in 2008, Hercules responded in 2009, and submitted a revised Human Health Risk Assessment (HHRA) in January 2011.  DNREC completed the review of the Risk Assessment upon the condition of Hercules giving  further clarification of specific sections of the HHRA.  Hercules submitted a response to DNREC for the HHRA Comment Letter in September 2012. The HHRA was approved by DNREC on January 11, 2013. Hercules has begun work on a site wide Corrective Measures Study (CMS). The CMS will provide remediation options for all remaining SWMUs and AOCs.

SWMU Closures/Status:

SWMU 9A was a former drum storage area. This regulated unit is located within a larger area, designated as SWMU 15.  SWMU 9A was closed under DNREC’s Solid and Hazardous Waste Management Branch (SHWMB) and in January 1999, DNREC issued the Closure Certification letter for SWMU 9A. Groundwater sampling is conducted semi-annually as part of Post Closure Care Monitoring.  Sampling showed that the area was impacted by past releases from experimental pesticide formulation in a nearby building.  Soil samples in SWMUs 9A/15 showed pesticide, metals, and volatile organic compounds, including chlorobenzene.  Hercules excavated contaminated soil "hot spots" and capped the area with a low permeability asphalt cover.  Groundwater samples indicated that soil contaminants did not impact the groundwater.

SWMU 8 and 9C was a dump and drum storage area, located adjacent to the Red Clay Creek.  Polychlorinated biphenyl (PCBs), pesticides, and metals were found in soil and some sediment on the SWMU.   Hercules submitted a Corrective Measures Study to EPA in 1997.  EPA required additional sediment sampling to evaluate if Red Clay Creek had been impacted by this SWMU.  Creek sediment sampling was completed in October 2000.  In March 2001, the Red Clay Creek Sediment Sampling and Analysis Report was submitted to EPA.  DDT and DDD (two types of pesticides) hotspots were detected downstream of Hercules.  In September 2001, EPA conducted limited confirmation sampling in the Creek.  The results indicated that contaminants in Red Clay Creek may have come from upstream sources, and could not be definitively linked to the Hercules site.  In 2008, further soil sampling was conducted at SWMU 8/9C to delineate the extent of excavation needed within the Wilmington and Western Railroad right-of-way.  DNREC selected a remedy for SWMU 8/9C and the construction of a low permeability cap began in August 2010 and was completed in 2011. An Environmental Covenant will also be implemented to protect the cap. The Covenant for SWMU 8/9c is currently under review by Hercules.

SWMU 6 was a RCRA regulated, greater-than-90-day container storage pad used for hazardous waste storage. The Pad included a small container shed with three separate diked areas for storage of corrosive, toxic, and reactive wastes.  In 2005, Hercules clean closed (under prior DNREC approval) the container storage area.  On May 31, 2006, DNREC issued a RCRA Closure Certification.

SWMU 16 is a former Agricultural Chemical Lab (ACL) research and development center.  Soil samples collected from the SWMU showed that only toxaphene (a pesticide) and a few metals exceeded DNREC Standards for Unrestricted Use.  Hercules removed an underground storage tank and demolished the buildings and structures at the ACL.  Hercules collected additional soil samples to delineate the extent of contamination. Any contamination found within this SWMU will be addressed as part of the site wide CMS.

In 2005, Hercules presented a Plan to relocate all operations currently in the Red Clay Creek floodplain to areas above the floodplain.  Hercules completed the relocations.

In September 2003, EPA concurred that current human exposure to contamination found in environmental media on-site is under control.  In August 2007, the Environmental Indicator for Migration of Contaminated Groundwater under Control (available on the EPA website) was signed, which means that contaminated groundwater is confined to discrete areas on-site.  Groundwater at the Facility is not used for drinking water purposes.

Top of Page

Site Description

Interactive Map of Hercules LLC Research Center, Wilmington, Delaware

View larger map

The Hercules Research Center is located about five miles west of Wilmington, Delaware. The facility occupies approximately 45 acres, primarily consisting of laboratory buildings used for research and development chemistry studies for Hercules' worldwide chemical operations. The facility is surrounded to the north, west and south by residences or proposed residences. To the east are the Red Clay Creek and a small railroad operated by the Wilmington and Western Railroad.

In November 2008, Hercules Incorporated was acquired by Ashland Water Technologies.

Top of Page

Contaminants at this Facility

 The main contaminants in the soil, groundwater, sediments and surface water are PCBs, pesticides, chlorinated solvents and metals.

Top of Page

Institutional and Engineering Controls at this Facility

No institutional controls are currently in place.

Top of Page

Land Reuse Information at this Facility

The facility is under continued use.

Top of Page

Site Responsibility at this Facility

RCRA Corrective Action activities at this facility are being conducted under the direction of the DE DNREC with assistance from EPA Region 3.

Top of Page